WorldWideScience

Sample records for ground-based radial velocity

  1. Radial Velocities with PARAS

    Science.gov (United States)

    Roy, Arpita; Mahadevan, S.; Chakraborty, A.; Pathan, F. M.; Anandarao, B. G.

    2010-01-01

    The Physical Research Laboratory Advanced Radial-velocity All-sky Search (PARAS) is an efficient fiber-fed cross-dispersed high-resolution echelle spectrograph that will see first light in early 2010. This instrument is being built at the Physical Research laboratory (PRL) and will be attached to the 1.2m telescope at Gurushikhar Observatory at Mt. Abu, India. PARAS has a single-shot wavelength coverage of 370nm to 850nm at a spectral resolution of R 70000 and will be housed in a vacuum chamber (at 1x10-2 mbar pressure) in a highly temperature controlled environment. This renders the spectrograph extremely suitable for exoplanet searches with high velocity precision using the simultaneous Thorium-Argon wavelength calibration method. We are in the process of developing an automated data analysis pipeline for echelle data reduction and precise radial velocity extraction based on the REDUCE package of Piskunov & Valenti (2002), which is especially careful in dealing with CCD defects, extraneous noise, and cosmic ray spikes. Here we discuss the current status of the PARAS project and details and tests of the data analysis procedure, as well as results from ongoing PARAS commissioning activities.

  2. Ground-based CCD astrometry with wide field imagers. II. A star catalogue for M67: WFI@2.2m MPG/ESO astrometry, FLAMES@VLT radial velocities

    CERN Document Server

    Yadav, R K S; Piotto, G; Anderson, J; Cassisi, S; Villanova, S; Platais, I; Pasquini, L; Momany, Y; Sagar, R

    2008-01-01

    The solar-age open cluster M67 (C0847+120, NGC2682) is a touchstone in studies of the old Galactic disk. Despite its outstanding role, the census of cluster membership for M67 at fainter magnitudes and their properties are not well-established. Using the proprietary and archival ESO data, we have obtained astrometric, photometric, and radial velocities of stars in a 34'x 33' field centered on the old open cluster M67. The two-epoch archival observations separated by 4 years and acquired with the Wide Field Imager at the 2.2m MPG/ESO telescope have been reduced with our new astrometric techniques, as described in the first paper of this series. The same observations served to derive calibrated BVI photometry in M67. Radial velocities were measured using the archival and new spectroscopic data obtained at VLT. We have determined relative proper motions and membership probabilities for ~2,400 stars. The precision of proper motions for optimally exposed stars is ~2 mas/yr, gradually degrading down to ~5 mas/yr at...

  3. Tachoastrometry: astrometry with radial velocities

    CERN Document Server

    Pasquini, L; Lombardi, M; Monaco, L; Leão, I C; Delabre, B

    2014-01-01

    Spectra of composite systems (e.g., spectroscopic binaries) contain spatial information that can be retrieved by measuring the radial velocities (i.e., Doppler shifts) of the components in four observations with the slit rotated by 90 degrees in the sky. By using basic concepts of slit spectroscopy we show that the geometry of composite systems can be reliably retrieved by measuring only radial velocity differences taken with different slit angles. The spatial resolution is determined by the precision with which differential radial velocities can be measured. We use the UVES spectrograph at the VLT to observe the known spectroscopic binary star HD 188088 (HIP 97944), which has a maximum expected separation of 23 milli-arcseconds. We measure an astrometric signal in radial velocity of 276 \\ms, which corresponds to a separation between the two components at the time of the observations of 18 $\\pm2$ milli-arcseconds. The stars were aligned east-west. We describe a simple optical device to simultaneously record p...

  4. Radial velocity moments of dark matter haloes

    CERN Document Server

    Wojtak, R; Gottlöber, S; Mamon, G A; Wojtak, Radoslaw; Lokas, Ewa L.; Gottloeber, Stefan; Mamon, Gary A.

    2005-01-01

    Using cosmological N-body simulations we study the radial velocity distribution in dark matter haloes focusing on the lowest-order even moments, dispersion and kurtosis. We determine the properties of ten massive haloes in the simulation box approximating their density distribution by the NFW formula characterized by the virial mass and concentration. We also calculate the velocity anisotropy parameter of the haloes and find it mildly radial and increasing with distance from the halo centre. The radial velocity dispersion of the haloes shows a characteristic profile with a maximum, while the radial kurtosis profile decreases with distance starting from a value close to Gaussian near the centre. We therefore confirm that dark matter haloes possess intrinsically non-Gaussian, flat-topped velocity distributions. We find that the radial velocity moments of the simulated haloes are very well reproduced by the solutions of the Jeans equations obtained for the halo parameters with the anisotropy measured in the simu...

  5. Radial Velocity Fluctuations of RZ Psc

    Science.gov (United States)

    Potravnov, I. S.; Gorynya, N. A.; Grinin, V. P.; Minikulov, N. Kh.

    2014-12-01

    The behavior of the radial velocity of the UX Ori type star RZ Psc is studied. The existence of an inner cavity with a radius of about 0.7 a.u. in the circumstellar disk of this star allows to suggest the presence of a companion. A study of the radial velocity of RZ Psc based on our own measurements and published data yields no periodic component in its variability. The two most accurate measurements of V r , based on high resolution spectra obtained over a period of three months, show that the radial velocity is constant over this time interval to within 0.5 km/s. This imposes a limit of M p ≤10 M Jup on the mass of the hypothetical companion. Possible reasons for the observed strong fluctuations in the radial velocity of this star are discussed.

  6. Precise Near-Infrared Radial Velocities

    CERN Document Server

    Plavchan, Peter; Gagne, Jonathan; Furlan, Elise; Brinkworth, Carolyn; Bottom, Michael; Tanner, Angelle; Anglada-Escude, Guillem; White, Russel; Davison, Cassy; Mills, Sean; Beichman, Chas; Johnson, John Asher; Ciardi, David; Wallace, Kent; Mennesson, Bertrand; Vasisht, Gautam; Prato, Lisa; Kane, Stephen; Crawford, Sam; Crawford, Tim; Sung, Keeyoon; Drouin, Brian; Lin, Sean; Leifer, Stephanie; Catanzarite, Joe; Henry, Todd; von Braun, Kaspar; Walp, Bernie; Geneser, Claire; Ogden, Nick; Stufflebeam, Andrew; Pohl, Garrett; Regan, Joe

    2016-01-01

    We present the results of two 2.3 micron near-infrared radial velocity surveys to detect exoplanets around 36 nearby and young M dwarfs. We use the CSHELL spectrograph (R ~46,000) at the NASA InfraRed Telescope Facility, combined with an isotopic methane absorption gas cell for common optical path relative wavelength calibration. We have developed a sophisticated RV forward modeling code that accounts for fringing and other instrumental artifacts present in the spectra. With a spectral grasp of only 5 nm, we are able to reach long-term radial velocity dispersions of ~20-30 m/s on our survey targets.

  7. Radial velocities of population II binary stars. II

    CERN Document Server

    Bartkevicius, A

    2006-01-01

    Here we publish the second list of radial velocities for 91 Hipparcos stars, mostly high transverse velocity binaries without previous radial velocity measurements. The measurements of radial velocities are done with a CORAVEL-type radial velocity spectrometer with an accuracy better than 1 km/s. We also present the information on eight new radial velocity variables - HD 29696, HD 117466AB, BD +28 4035AB, BD +30 2129A, BD +39 1828AB, BD +69 230A, BD +82 565A and TYC 2267-1300-1 - found from our measurements. Two stars (HD 27961AB and HD 75632AB) are suspected as possible radial velocity variables.

  8. Radial velocity eclipse mapping of exoplanets

    CERN Document Server

    Nikolov, Nikolay

    2015-01-01

    Planetary rotation rates and obliquities provide information regarding the history of planet formation, but have not yet been measured for evolved extrasolar planets. Here we investigate the theoretical and observational perspective of the Rossiter-McLauglin effect during secondary eclipse (RMse) ingress and egress for transiting exoplanets. Near secondary eclipse, when the planet passes behind the parent star, the star sequentially obscures light from the approaching and receding parts of the rotating planetary surface. The temporal block of light emerging from the approaching (blue-shifted) or receding (red-shifted) parts of the planet causes a temporal distortion in the planet's spectral line profiles resulting in an anomaly in the planet's radial velocity curve. We demonstrate that the shape and the ratio of the ingress-to-egress radial velocity amplitudes depends on the planetary rotational rate, axial tilt and impact factor (i.e. sky-projected planet spin-orbital alignment). In addition, line asymmetrie...

  9. The radial velocity experiment (RAVE) : Fourth data release

    NARCIS (Netherlands)

    Kordopatis, G.; Gilmore, G.; Steinmetz, M.; Boeche, C.; Seabroke, G. M.; Siebert, A.; Zwitter, T.; Binney, J.; de Laverny, P.; Recio-Blanco, A.; Williams, M. E. K.; Piffl, T.; Enke, H.; Roeser, S.; Bijaoui, A.; Wyse, R. F. G.; Freeman, K.; Munari, U.; Carrillo, I.; Anguiano, B.; Burton, D.; Campbell, R.; Cass, C. J. P.; Fiegert, K.; Hartley, M.; Parker, Q. A.; Reid, W.; Ritter, A.; Russell, K. S.; Stupar, M.; Watson, F. G.; Bienayme, O.; Bland-Hawthorn, J.; Gerhard, O.; Gibson, B. K.; Grebel, E. K.; Helmi, A.; Navarro, J. F.; Conrad, C.; Famaey, B.; Faure, C.; Just, A.; Kos, J.; Matijevic, G.; McMillan, P. J.; Minchev, I.; Scholz, R.; Sharma, S.; Siviero, A.; de Boer, E. Wylie; Zerjal, M.

    2013-01-01

    We present the stellar atmospheric parameters (effective temperature, surface gravity, overall metallicity), radial velocities, individual abundances, and distances determined for 425,561 stars, which constitute the fourth public data release of the RAdial Velocity Experiment (RAVE). The stellar atm

  10. The Radial Velocity Experiment (RAVE): Fourth Data Release

    NARCIS (Netherlands)

    Kordopatis, G.; Gilmore, G.; Steinmetz, M.; Boeche, C.; Seabroke, G. M.; Siebert, A.; Zwitter, T.; Binney, J.; de Laverny, P.; Recio-Blanco, A.; Williams, M. E. K.; Piffl, T.; Enke, H.; Roeser, S.; Bijaoui, A.; Wyse, R. F. G.; Freeman, K.; Munari, U.; Carrillo, I.; Anguiano, B.; Burton, D.; Campbell, R.; Cass, C. J. P.; Fiegert, K.; Hartley, M.; Parker, Q. A.; Reid, W.; Ritter, A.; Russell, K. S.; Stupar, M.; Watson, F. G.; Bienaymé, O.; Bland-Hawthorn, J.; Gerhard, O.; Gibson, B. K.; Grebel, E. K.; Helmi, A.; Navarro, J. F.; Conrad, C.; Famaey, B.; Faure, C.; Just, A.; Kos, J.; Matijevič, G.; McMillan, P. J.; Minchev, I.; Scholz, R.; Sharma, S.; Siviero, A.; de Boer, E. Wylie; Žerjal, M.

    2013-01-01

    We present the stellar atmospheric parameters (effective temperature, surface gravity, overall metallicity), radial velocities, individual abundances, and distances determined for 425,561 stars, which constitute the fourth public data release of the RAdial Velocity Experiment (RAVE). The stellar atm

  11. RADIAL VELOCITY ECLIPSE MAPPING OF EXOPLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Nikolov, Nikolay; Sainsbury-Martinez, Felix, E-mail: nikolay@astro.ex.ac.uk [Astrophysics Group, School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom)

    2015-07-20

    Planetary rotation rates and obliquities provide information regarding the history of planet formation, but have not yet been measured for evolved extrasolar planets. Here we investigate the theoretical and observational perspective of the Rossiter–McLaughlin effect during secondary eclipse (RMse) ingress and egress for transiting exoplanets. Near secondary eclipse, when the planet passes behind the parent star, the star sequentially obscures light from the approaching and receding parts of the rotating planetary surface. The temporal block of light emerging from the approaching (blueshifted) or receding (redshifted) parts of the planet causes a temporal distortion in the planet’s spectral line profiles resulting in an anomaly in the planet’s radial velocity curve. We demonstrate that the shape and the ratio of the ingress-to-egress radial velocity amplitudes depends on the planetary rotational rate, axial tilt, and impact factor (i.e., sky-projected planet spin–orbital alignment). In addition, line asymmetries originating from different layers in the atmosphere of the planet could provide information regarding zonal atmospheric winds and constraints on the hot spot shape for giant irradiated exoplanets. The effect is expected to be most-pronounced at near-infrared wavelengths, where the planet-to-star contrasts are large. We create synthetic near-infrared, high-dispersion spectroscopic data and demonstrate how the sky-projected spin axis orientation and equatorial velocity of the planet can be estimated. We conclude that the RMse effect could be a powerful method to measure exoplanet spins.

  12. Analytical fit of radial velocity data

    CERN Document Server

    Delisle, J -B; Buchschacher, N; Alesina, F

    2015-01-01

    We describe an analytical method for computing the orbital parameters of planets from the periodogram of a radial velocity signal. The method is very efficient and provides a good approximation of the orbital parameters. The accuracy is mainly limited by the accuracy of the computation of the Fourier decomposition of the signal which is sensible to sampling and noise. Our method is complementary with more accurate (and more computer time expensive) numerical algorithms (e.g. Levenberg-Marquardt, MCMC, genetic algorithms). Indeed, the analytical approximation can be used as initial condition to accelerate the convergence of these numerical methods.

  13. Radial Velocity Variability of Field Brown Dwarfs

    CERN Document Server

    Prato, L; Rice, E L; McLean, I S; Kirkpatrick, J D; Burgasser, A J; Kim, S S

    2015-01-01

    We present paper six of the NIRSPEC Brown Dwarf Spectroscopic Survey, an analysis of multi-epoch, high-resolution (R~20,000) spectra of 25 field dwarf systems (3 late-type M dwarfs, 16 L dwarfs, and 6 T dwarfs) taken with the NIRSPEC infrared spectrograph at the W. M. Keck Observatory. With a radial velocity precision of ~2 km/s, we are sensitive to brown dwarf companions in orbits with periods of a few years or less given a mass ratio of 0.5 or greater. We do not detect any spectroscopic binary brown dwarfs in the sample. Given our target properties, and the frequency and cadence of observations, we use a Monte Carlo simulation to determine the detection probability of our sample. Even with a null detection result, our 1 sigma upper limit for very low mass binary frequency is 18%. Our targets included 7 known, wide brown dwarf binary systems. No significant radial velocity variability was measured in our multi-epoch observations of these systems, even for those pairs for which our data spanned a significant ...

  14. Precise radial velocities in the near infrared

    Science.gov (United States)

    Redman, Stephen L.

    Since the first detection of a planet outside our Solar System byWolszczan & Frail (1992), over 500 exoplanets have been found to date2, none of which resemble the Earth. Most of these planets were discovered by measuring the radial velocity (hereafter, RV) of the host star, which wobbles under the gravitational influence of any existing planetary companions. However, this method has yet to achieve the sub-m/s precision necessary to detect an Earth-mass planet in the Habitable Zone (the region around a star that can support liquid water; hereafter, HZ) (Kasting et al. 1993) around a Solar-type star. Even though Kepler (Borucki et al. 2010) has announced several Earth-sized HZ candidates, these targets will be exceptionally difficult to confirm with current astrophysical spectrographs (Borucki et al. 2011). The fastest way to discover and confirm potentiallyhabitable Earth-mass planets is to observe stars with lower masses - in particular, late M dwarfs. While M dwarfs are readily abundant, comprising some 70% of the local stellar population, their low optical luminosity presents a formidable challenge to current optical RV instruments. By observing in the near-infrared (hereafter, NIR), where the flux from M dwarfs peaks, we can potentially reach low RV precisions with significantly less telescope time than would be required by a comparable optical instrument. However, NIR precision RV measurements are a relatively new idea and replete with challenges: IR arrays, unlike CCDs, are sensitive to the thermal background; modal noise is a bigger issue in the NIR than in the optical; and the NIR currently lacks the calibration sources like the very successful thorium-argon (hereafter, ThAr) hollow-cathode lamp and Iodine gas cell of the optical. The PSU Pathfinder (hereafter, Pathfinder) was designed to explore these technical issues with the intention of mitigating these problems for future NIR high-resolution spectrographs, such as the Habitable-Zone Planet Finder (HZPF

  15. Radial velocities of southern visual multiple stars

    Energy Technology Data Exchange (ETDEWEB)

    Tokovinin, Andrei [Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile); Pribulla, Theodor [Astronomical Institute, Slovak Academy of Sciences, 059 60 Tatranská Lomnica (Slovakia); Fischer, Debra, E-mail: atokovinin@ctio.noao.edu, E-mail: pribulla@ta3.sk, E-mail: debra.fischer@gmail.com [Department of Astronomy, Yale University, New Haven, CT 06511 (United States)

    2015-01-01

    High-resolution spectra of visual multiple stars were taken in 2008–2009 to detect or confirm spectroscopic subsystems and to determine their orbits. Radial velocities of 93 late-type stars belonging to visual multiple systems were measured by numerical cross-correlation. We provide the individual velocities, the width, and the amplitude of the Gaussians that approximate the correlations. The new information on the multiple systems resulting from these data is discussed. We discovered double-lined binaries in HD 41742B, HD 56593C, and HD 122613AB, confirmed several other known subsystems, and constrained the existence of subsystems in some visual binaries where both components turned out to have similar velocities. The orbits of double-lined subsystems with periods of 148 and 13 days are computed for HD 104471 Aa,Ab and HD 210349 Aa,Ab, respectively. We estimate individual magnitudes and masses of the components in these triple systems and update the outer orbit of HD 104471 AB.

  16. Radial velocity monitoring of Kepler heartbeat stars

    CERN Document Server

    Shporer, Avi; Isaacson, Howard; Hambleton, Kelly; Thompson, Susan E; Prsa, Andrej; Kurtz, Donald W; Howard, Andrew W; O'Leary, Ryan M

    2016-01-01

    Heartbeat stars (HB stars) are a class of eccentric binary stars with close periastron passages. The characteristic photometric HB signal evident in their light curves is produced by a combination of tidal distortion, heating, and Doppler boosting near orbital periastron. Many HB stars continue to oscillate after periastron and along the entire orbit, indicative of the tidal excitation of oscillation modes within one or both stars. These systems are among the most eccentric binaries known, and they constitute astrophysical laboratories for the study of tidal effects. We have undertaken a radial velocity (RV) monitoring campaign of Kepler HB stars in order to measure their orbits. We present our first results here, including a sample of 21 Kepler HB systems, where for 19 of them we obtained the Keplerian orbit and for 3 other systems we did not detect a statistically significant RV variability. Results presented here are based on 218 spectra obtained with the Keck/HIRES spectrograph during the 2015 Kepler obse...

  17. Radial velocity signatures of Zeeman broadening

    CERN Document Server

    Reiners, Ansgar; Anglada-Escude, Guillem; Jeffers, Sandra V; Morin, Julien; Zechmeister, Mathias; Kochukhov, Oleg; Piskunov, Nikolai

    2013-01-01

    Stellar activity signatures such as spots and plage can significantly limit the search for extrasolar planets. Current models of activity-induced radial velocity (RV) signals focused on the impact of temperature contrast in spots predicting the signal to diminish toward longer wavelengths. On the other hand, the relative importance of the Zeeman effect on RV measurements should grow with wavelength, because the Zeeman displacement itself grows with \\lambda, and because a magnetic and cool spot contributes more to the total flux at longer wavelengths. We model the impact of active regions on stellar RV measurements including both temperature contrast in spots and Zeeman line broadening. We calculate stellar line profiles using polarized radiative transfer models including atomic and molecular Zeeman splitting from 0.5 to 2.3\\mum. Our results show that the amplitude of the RV signal caused by the Zeeman effect alone can be comparable to that caused by temperature contrast. Furthermore, the RV signal caused by c...

  18. High precision radial velocities with GIANO spectra

    CERN Document Server

    Carleo, I; Gratton, R; Benatti, S; Bonavita, M; Oliva, E; Origlia, L; Desidera, S; Claudi, R; Sissa, E

    2016-01-01

    Radial velocities (RV) measured from near-infrared (NIR) spectra are a potentially excellent tool to search for extrasolar planets around cool or active stars. High resolution infrared (IR) spectrographs now available are reaching the high precision of visible instruments, with a constant improvement over time. GIANO is an infrared echelle spectrograph at the Telescopio Nazionale Galileo (TNG) and it is a powerful tool to provide high resolution spectra for accurate RV measurements of exoplanets and for chemical and dynamical studies of stellar or extragalactic objects. No other high spectral resolution IR instrument has GIANO's capability to cover the entire NIR wavelength range (0.95-2.45 micron) in a single exposure. In this paper we describe the ensemble of procedures that we have developed to measure high precision RVs on GIANO spectra acquired during the Science Verification (SV) run, using the telluric lines as wavelength reference. We used the Cross Correlation Function (CCF) method to determine the v...

  19. The Radial Velocity Experiment (RAVE) : Second data release

    NARCIS (Netherlands)

    Zwitter, T.; Siebert, A.; Munari, U.; Freeman, K. C.; Siviero, A.; Watson, F. G.; Fulbright, J. P.; Wyse, R. F. G.; Campbell, R.; Seabroke, G. M.; Williams, M.; Steinmetz, M.; Bienayme, O.; Gilmore, G.; Grebel, E. K.; Helmi, A.; Navarro, J. F.; Anguiano, B.; Boeche, C.; Burton, D.; Cass, P.; Dawe, J.; Fiegert, K.; Hartley, M.; Russell, K.; Veltz, L.; Bailin, J.; Binney, J.; Bland-Hawthorn, J.; Brown, A.; Dehnen, W.; Evans, N. W.; Fiorentin, P. Re; Fiorucci, M.; Gerhard, O.; Gibson, B.; Kelz, A.; Kuijken, K.; Matijevic, G.; Minchev, I.; Parker, Q. A.; Penarrubia, J.; Quillen, A.; Read, M. A.; Reid, W.; Roeser, S.; Ruchti, G.; Scholz, R. -D.; Smith, M. C.; Sordo, R.; Tolstoi, E.; Tomasella, L.; Vidrih, S.; De Boer, E. Wylie

    We present the second data release of the Radial Velocity Experiment ( RAVE), an ambitious spectroscopic survey to measure radial velocities and stellar atmosphere parameters ( temperature, metallicity, surface gravity, and rotational velocity) of up to one million stars using the 6 dF multi-object

  20. Radial velocity planet detection biases at the stellar rotational period

    OpenAIRE

    2016-01-01

    Future generations of precise radial velocity (RV) surveys aim to achieve sensitivity sufficient to detect Earth mass planets orbiting in their stars' habitable zones. A major obstacle to this goal is astrophysical radial velocity noise caused by active areas moving across the stellar limb as a star rotates. In this paper, we quantify how stellar activity impacts exoplanet detection with radial velocities as a function of orbital and stellar rotational periods. We perform data-driven simulati...

  1. A New Filtering Algorithm Utilizing Radial Velocity Measurement

    Institute of Scientific and Technical Information of China (English)

    LIU Yan-feng; DU Zi-cheng; PAN Quan

    2005-01-01

    Pulse Doppler radar measurements consist of range, azimuth, elevation and radial velocity. Most of the radar tracking algorithms in engineering only utilize position measurement. The extended Kalman filter with radial velocity measureneut is presented, then a new filtering algorithm utilizing radial velocity measurement is proposed to improve tracking results and the theoretical analysis is also given. Simulation results of the new algorithm, converted measurement Kalman filter, extended Kalman filter are compared. The effectiveness of the new algorithm is verified by simulation results.

  2. Astrometric radial velocities. I. Non-spectroscopic methods for measuring stellar radial velocity

    OpenAIRE

    1999-01-01

    High-accuracy astrometry permits the determination of not only stellar tangential motion, but also the component along the line-of-sight. Such non-spectroscopic (i.e. astrometric) radial velocities are independent of stellar atmospheric dynamics, spectral complexity and variability, as well as of gravitational redshift. Three methods are analysed: (1) changing annual parallax, (2) changing proper motion and (3) changing angular extent of a moving group of stars. All three have significant pot...

  3. A test field for Gaia. Radial velocity catalogue of stars in the South Ecliptic Pole

    CERN Document Server

    Frémat, Y; Pancino, E; Soubiran, C; Jofré, P; Damerdji, Y; Heiter, U; Royer, F; Seabroke, G; Sordo, R; Blanco-Cuaresma, S; Jasniewicz, G; Martayan, C; Thévenin, F; Vallenari, A; Blomme, R; David, M; Gosset, E; Katz, D; Viala, Y; Boudreault, S; Cantat-Gaudin, T; Lobel, A; Meisenheimer, K; Nordlander, T; Raskin, G; Royer, P; Zorec, J

    2016-01-01

    Gaia is a space mission currently measuring the five astrometric parameters as well as spectrophotometry of at least 1 billion stars to G = 20.7 mag with unprecedented precision. The sixth parameter in phase space (radial velocity) is also measured thanks to medium-resolution spectroscopy being obtained for the 150 million brightest stars. During the commissioning phase, two fields, one around each ecliptic pole, have been repeatedly observed to assess and to improve the overall satellite performances as well as the associated reduction and analysis software. A ground-based photometric and spectroscopic survey was therefore initiated in 2007, and is still running in order to gather as much information as possible about the stars in these fields. This work is of particular interest to the validation of the Radial Velocity Spectrometer (RVS) outputs. The paper presents the radial velocity measurements performed for the Southern targets in the 12 - 17 R magnitude range on high- to mid-resolution spectra obtained...

  4. Radial Velocity Monitoring of Kepler Heartbeat Stars

    Science.gov (United States)

    Shporer, Avi; Fuller, Jim; Isaacson, Howard; Hambleton, Kelly; Thompson, Susan E.; Prša, Andrej; Kurtz, Donald W.; Howard, Andrew W.; O'Leary, Ryan M.

    2016-09-01

    Heartbeat stars (HB stars) are a class of eccentric binary stars with close periastron passages. The characteristic photometric HB signal evident in their light curves is produced by a combination of tidal distortion, heating, and Doppler boosting near orbital periastron. Many HB stars continue to oscillate after periastron and along the entire orbit, indicative of the tidal excitation of oscillation modes within one or both stars. These systems are among the most eccentric binaries known, and they constitute astrophysical laboratories for the study of tidal effects. We have undertaken a radial velocity (RV) monitoring campaign of Kepler HB stars in order to measure their orbits. We present our first results here, including a sample of 22 Kepler HB systems, where for 19 of them we obtained the Keplerian orbit and for 3 other systems we did not detect a statistically significant RV variability. Results presented here are based on 218 spectra obtained with the Keck/HIRES spectrograph during the 2015 Kepler observing season, and they have allowed us to obtain the largest sample of HB stars with orbits measured using a single instrument, which roughly doubles the number of HB stars with an RV measured orbit. The 19 systems measured here have orbital periods from 7 to 90 days and eccentricities from 0.2 to 0.9. We show that HB stars draw the upper envelope of the eccentricity-period distribution. Therefore, HB stars likely represent a population of stars currently undergoing high eccentricity migration via tidal orbital circularization, and they will allow for new tests of high eccentricity migration theories. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

  5. TRUE MASSES OF RADIAL-VELOCITY EXOPLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Robert A., E-mail: rbrown@stsci.edu [Space Telescope Science Institute (United States)

    2015-06-01

    We study the task of estimating the true masses of known radial-velocity (RV) exoplanets by means of direct astrometry on coronagraphic images to measure the apparent separation between exoplanet and host star. Initially, we assume perfect knowledge of the RV orbital parameters and that all errors are due to photon statistics. We construct design reference missions for four missions currently under study at NASA: EXO-S and WFIRST-S, with external star shades for starlight suppression, EXO-C and WFIRST-C, with internal coronagraphs. These DRMs reveal extreme scheduling constraints due to the combination of solar and anti-solar pointing restrictions, photometric and obscurational completeness, image blurring due to orbital motion, and the “nodal effect,” which is the independence of apparent separation and inclination when the planet crosses the plane of the sky through the host star. Next, we address the issue of nonzero uncertainties in RV orbital parameters by investigating their impact on the observations of 21 single-planet systems. Except for two—GJ 676 A b and 16 Cyg B b, which are observable only by the star-shade missions—we find that current uncertainties in orbital parameters generally prevent accurate, unbiased estimation of true planetary mass. For the coronagraphs, WFIRST-C and EXO-C, the most likely number of good estimators of true mass is currently zero. For the star shades, EXO-S and WFIRST-S, the most likely numbers of good estimators are three and four, respectively, including GJ 676 A b and 16 Cyg B b. We expect that uncertain orbital elements currently undermine all potential programs of direct imaging and spectroscopy of RV exoplanets.

  6. Radial Velocity Planet Detection Biases at the Stellar Rotational Period

    CERN Document Server

    Vanderburg, Andrew; Johnson, John Asher; Ciardi, David R; Swift, Jonathan; Kane, Stephen R

    2016-01-01

    Future generations of precise radial velocity (RV) surveys aim to achieve sensitivity sufficient to detect Earth mass planets orbiting in their stars' habitable zones. A major obstacle to this goal is astrophysical radial velocity noise caused by active areas moving across the stellar limb as a star rotates. In this paper, we quantify how stellar activity impacts exoplanet detection with radial velocities as a function of orbital and stellar rotational periods. We perform data-driven simulations of how stellar rotation affects planet detectability and compile and present relations for the typical timescale and amplitude of stellar radial velocity noise as a function of stellar mass. We show that the characteristic timescales of quasi-periodic radial velocity jitter from stellar rotational modulations coincides with the orbital period of habitable zone exoplanets around early M-dwarfs. These coincident periods underscore the importance of monitoring the targets of RV habitable zone planet surveys through simul...

  7. Radial Velocity Fitting Challenge. I. Simulating the data set including realistic stellar radial-velocity signals

    CERN Document Server

    Dumusque, X

    2016-01-01

    Stellar signals are the main limitation for precise radial-velocity (RV) measurements. These signals arise from the photosphere of the stars. The m/s perturbation created by these signals prevents the detection and mass characterization of small-mass planetary candidates such as Earth-twins. Several methods have been proposed to mitigate stellar signals in RV measurements. However, without precisely knowing the stellar and planetary signals in real observations, it is extremely difficult to test the efficiency of these methods. The goal of the RV fitting challenge is to generate simulated RV data including stellar and planetary signals and to perform a blind test within the community to test the efficiency of the different methods proposed to recover planetary signals despite stellar signals. In this first paper, we describe the simulation used to model the measurements of the RV fitting challenge. Each simulated planetary system includes the signals from instrumental noise, stellar oscillations, granulation,...

  8. Astrometric radial velocities. I. Non-spectroscopic methods for measuring stellar radial velocity

    Science.gov (United States)

    Dravins, Dainis; Lindegren, Lennart; Madsen, Søren

    1999-08-01

    High-accuracy astrometry permits the determination of not only stellar tangential motion, but also the component along the line-of-sight. Such non-spectroscopic (i.e. astrometric) radial velocities are independent of stellar atmospheric dynamics, spectral complexity and variability, as well as of gravitational redshift. Three methods are analysed: (1) changing annual parallax, (2) changing proper motion and (3) changing angular extent of a moving group of stars. All three have significant potential in planned astrometric projects. Current accuracies are still inadequate for the first method, while the second is marginally feasible and is here applied to 16 stars. The third method reaches high accuracy (accuracy limit is set by uncertainties in the cluster expansion rate. Based (in part) on observations by the ESA Hipparcos satellite

  9. Astrometric radial velocities; 1, Non-spectroscopic methods for measuring stellar radial velocity

    CERN Document Server

    Dravins, D; Madsen, S; Dravins, Dainis; Lindegren, Lennart; Madsen, Soren

    1999-01-01

    High-accuracy astrometry permits the determination of not only stellar tangential motion, but also the component along the line-of-sight. Such non-spectroscopic (i.e. astrometric) radial velocities are independent of stellar atmospheric dynamics, spectral complexity and variability, as well as of gravitational redshift. Three methods are analysed: (1) changing annual parallax, (2) changing proper motion and (3) changing angular extent of a moving group of stars. All three have significant potential in planned astrometric projects. Current accuracies are still inadequate for the first method, while the second is marginally feasible and is here applied to 16 stars. The third method reaches high accuracy (<1 km/s) already with present data, although for some clusters an accuracy limit is set by uncertainties in the cluster expansion rate.

  10. Radial velocities of "slow movers" - call for observations

    CERN Document Server

    Dybczynski, P A; Dybczynski, Piotr A.; Kwiatkowski, Tomasz

    2003-01-01

    This paper presents a list of suggested stars for radial velocity measurements. We explain here in brief the research project for which the radial velocity of the "slow movers" i.e. small proper motion stars are necessary. Basing on this study we prepared a list of 1100 stellar targets with very accurate positions, proper motions and trigonometric parallaxes but without radial velocity measurements. Distributions of stellar brightnesses and spectral types among these stars are presented as well as its "most wanted" subset. We announce the begin of the radial velocity measurements to be conducted with our new echelle spectrograph just put into operation and offer some coordination for observations of targets that cannot be reached from our location.

  11. The Galactic Bulge Radial Velocity/Abundance Assay

    Science.gov (United States)

    Rich, R. M.

    2012-08-01

    The Bulge Radial Velocity Assay (BRAVA) measured radial velocities for ˜ 9500 late-type giants in the Galactic bulge, predominantly from -10° Cam and planned spectroscopic modes, as well as the high resolution spectrograph. The planned Jasmine satellite series may deliver a comprehensive survey of distances and proper motions of bulge stars, and insight into the origin and importance of the X-shaped bulge.

  12. Precise Radial Velocity First Light Observations With iSHELL

    Science.gov (United States)

    Cale, Bryson Lee; Plavchan, Peter; Nishimoto, America; Tanner, Angelle M.; Gagne, Jonathan; Gao, Peter; Furlan, Elise; White, Russel J.; Walp, Bernie; von Braun, Kaspar; Brinkworth, Carolyn; Johnson, John A.; Anglada-Escudé, Guillem; Henry, Todd J.; Catanzarite, Joseph; Kane, Stephen R.; Beichman, Charles; Ciardi, David R.; Wallace, J. Kent; Mennesson, Bertrand; Vasisht, Gautam

    2017-01-01

    We present our first light observations with the new iSHELL spectrograph at the NASA Infrared Telescope facility. iShell replaces the 25 year old CSHELL with improvements in spectral grasp (~40x), resolution (70,000 versus 46,000), throughput, optics, and detector characteristics. With CSHELL, we obtained a radial velocity precision of 3 m/s on a bright red giant and we identified several radial velocity variable M dwarfs for future follow up. Our goal with iSHELL is to characterize the precise radial velocity performance of the methane isotopologue absorption gas cell in the calibration unit. We observe bright nearby radial velocity standards to better understand the instrument and data reduction techniques. We have updated our CSHELL analysis code to handle multiple orders and the increased number of pixels. It is feasible that we will obtain a radial velocity precision of < 3 m/s, sufficient to detect terrestrial planets in the habitable zone of nearby M dwarfs. We will also follow up radial velocity variables we have discovered, along with transiting exoplanets orbiting M dwarfs identified with the K2 and TESS missions.

  13. State of the Field: Extreme Precision Radial Velocities

    CERN Document Server

    Fischer, Debra; Arriagada, Pamela; Baluev, Roman V; Bean, Jacob L; Bouchy, Francois; Buchhave, Lars A; Carroll, Thorsten; Chakraborty, Abhijit; Dawson, Rebekah I; Diddams, Scott A; Dumusque, Xavier; Eastman, Jason D; Endl, Michael; Figueira, Pedro; Ford, Eric B; Foreman-Mackey, Daniel; Fournier, Paul; Furesz, Gabor; Gaudi, B Scott; Gregory, Philip C; Grundahl, Frank; Hatzes, Artie P; Hebrard, Guillaume; Herrero, Enrique; Hogg, David W; Howard, Andrew W; Johnson, John A; Jorden, Paul; Jurgenson, Colby A; Latham, David W; Laughlin, Greg; Loredo, Thomas J; Lovis, Christophe; Mahadevan, Suvrath; McCracken, Tyler M; Pepe, Francesco; Perez, Mario; Phillips, David F; Plavchan, Peter P; Prato, Lisa; Quirrenbach, Andreas; Reiners, Ansgar; Robertson, Paul; Santos, Nuno C; Sawyer, David; Segransan, Damien; Sozzetti, Alessandro; Steinmetz, Tilo; Szentgyorgyi, Andrew; Udry, Stephane; Valenti, Jeff A; Wang, Sharon X; Wittenmyer, Robert A; Wright, Jason T

    2016-01-01

    The Second Workshop on Extreme Precision Radial Velocities defined circa 2015 the state of the art Doppler precision and identified the critical path challenges for reaching 10 cm/s measurement precision. The presentations and discussion of key issues for instrumentation and data analysis and the workshop recommendations for achieving this precision are summarized here. Beginning with the HARPS spectrograph, technological advances for precision radial velocity measurements have focused on building extremely stable instruments. To reach still higher precision, future spectrometers will need to produce even higher fidelity spectra. This should be possible with improved environmental control, greater stability in the illumination of the spectrometer optics, better detectors, more precise wavelength calibration, and broader bandwidth spectra. Key data analysis challenges for the precision radial velocity community include distinguishing center of mass Keplerian motion from photospheric velocities, and the proper ...

  14. Empirical Limits on Radial Velocity Planet Detection for Young Stars

    CERN Document Server

    Hillenbrand, Lynne; Marcy, Geoffrey; Barenfeld, Scott; Fischer, Debra; Howard, Andrew

    2014-01-01

    We report initial results from our long term search using precision radial velocities for planetary-mass companions located within a few AU of stars younger than the Sun. Based on a sample of >150 stars, we define a floor in the radial velocity scatter, sigma_RV, as a function of the chromospheric activity level R'_{HK}. This lower bound to the jitter, which increases with increasing stellar activity, sets the minimum planet mass that could be detected. Adopting a median activity-age relationship reveals the astrophysical limits to planet masses discernable via radial velocity monitoring, as a function of stellar age. Considering solar-mass primaries having the mean jitter-activity level, when they are younger than 100 / 300 / 1000 Myr, the stochastic jitter component in radial velocity measurements restricts detectable companion masses to > 0.3 / 0.2 / 0.1 M_Jupiter. These numbers require a large number -- several tens -- of radial velocity observations taken over a time frame longer than the orbital period....

  15. Radial velocity fitting challenge. I. Simulating the data set including realistic stellar radial-velocity signals

    Science.gov (United States)

    Dumusque, X.

    2016-08-01

    Context. Stellar signals are the main limitation for precise radial-velocity (RV) measurements. These signals arise from the photosphere of the stars. The m s-1 perturbation created by these signals prevents the detection and mass characterization of small-mass planetary candidates such as Earth-twins. Several methods have been proposed to mitigate stellar signals in RV measurements. However, without precisely knowing the stellar and planetary signals in real observations, it is extremely difficult to test the efficiency of these methods. Aims: The goal of the RV fitting challenge is to generate simulated RV data including stellar and planetary signals and to perform a blind test within the community to test the efficiency of the different methods proposed to recover planetary signals despite stellar signals. Methods: In this first paper, we describe the simulation used to model the measurements of the RV fitting challenge. Each simulated planetary system includes the signals from instrumental noise, stellar oscillations, granulation, supergranulation, stellar activity, and observed and simulated planetary systems. In addition to RV variations, this simulation also models the effects of instrumental noise and stellar signals on activity observables obtained by HARPS-type high-resolution spectrographs, that is, the calcium activity index log (R'HK) and the bisector span and full width at half maximum of the cross-correlation function. Results: We publish the 15 systems used for the RV fitting challenge including the details about the planetary systems that were injected into each of them. Based on observations collected at the La Silla Parana Observatory, ESO (Chile), with the HARPS spectrograph at the 3.6-m telescope.The simulated data sets are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/593/A5 and at the wiki of the RV fitting challenge http://https://rv-challenge.wikispaces.com.

  16. Starspot-induced radial velocity jitter during a stellar cycle

    DEFF Research Database (Denmark)

    Korhonen, Heidi Helena; Andersen, Jan Marie; Järvinen, Silva

    2012-01-01

    on the Sun and other cool stars changes cyclically during an activity cycle, which has length varying from about a year to longer than the solar 11 years. In this work we investigate the influence of varying amount of starspots on the sparsely sampled radial velocity observations - which are the norm...... in the radial velocity studies searching for exoplanets on wide orbits. We study two simulated cases: one with a random spot configuration, and one where the spot occurrence is concentrated. In addition we use Doppler images of young solar analogue V889 Her as a high activity case....

  17. Radial Velocity Studies of Close Binary Stars. XI

    CERN Document Server

    Pribulla, T; Lu, W; Mochnacki, S W; Conidis, G; Blake, R M; De Bond, H; Thomson, J R; Pych, W; Ogloza, W; Siwak, M; Pribulla, Theodor; Rucinski, Slavek M.; Lu, Wenxian; Mochnacki, Stefan W.; Conidis, George; Bond, Heide De; Pych, Wojtek; Ogloza, Waldemar; Siwak, Michal

    2006-01-01

    Radial-velocity measurements and sine-curve fits to the orbital radial velocity variations are presented for ten close binary systems: DU Boo, ET Boo, TX Cnc, V1073 Cyg, HL Dra, AK Her, VW LMi, V566 Oph, TV UMi and AG Vir. By this contribution, the DDO program has reached the point of 100 published radial velocity orbits. The radial velocities have been determined using an improved fitting technique which uses rotational profiles to approximate individual peaks in broadening functions. Three systems, ET Boo, VW LMi and TV UMi, were found to be quadruple while AG Vir appears to be a spectroscopic triple. ET Boo, a member of a close visual binary with $P_{vis} = 113$ years, was previously known to be a multiple system, but we show that the second component is actually a close, non-eclipsing binary. The new observations enabled us to determine the spectroscopic orbits of the companion, non-eclipsing pairs in ET Boo and VW LMi. The particularly interesting case is VW LMi, where the period of the mutual revolution...

  18. Radial velocity information in solar-type spectra

    Science.gov (United States)

    Merline, W. J.

    1985-01-01

    A criterion is developed for determining the amount of radial velocity information theoretically available at the earth's surface from a star as a function of wavelength and spectral resolution. A description of the study is provided. The wavelength dependence is examined as well as the dependence on resolution, frequency information, and the problem of time-dependent astrophysical phenomena.

  19. Precise Radial Velocities of Polaris: Detection of Amplitude Growth

    CERN Document Server

    Lee, Byeong-Cheol; Han, Inwoo; Park, Myeong-Gu; Kim, Kang-Min

    2008-01-01

    We present a first results from a long-term program of a radial velocity study of Cepheid Polaris (F7 Ib) aimed to find amplitude and period of pulsations and nature of secondary periodicities. 264 new precise radial velocity measurements were obtained during 2004-2007 with the fiber-fed echelle spectrograph Bohyunsan Observatory Echelle Spectrograph (BOES) of 1.8m telescope at Bohyunsan Optical Astronomy Observatory (BOAO) in Korea. We find a pulsational radial velocity amplitude and period of Polaris for three seasons of 2005.183, 2006.360, and 2007.349 as 2K = 2.210 +/- 0.048 km/s, 2K = 2.080 +/- 0.042 km/s, and 2K = 2.406 +/- 0.018 km/s respectively, indicating that the pulsational amplitudes of Polaris that had decayed during the last century is now increasing rapidly. The pulsational period was found to be increasing too. This is the first detection of a historical turnaround of pulsational amplitude change in Cepheids. We clearly find the presence of additional radial velocity variations on a time scal...

  20. Signals embedded in the radial velocity noise. Periodic variations in the tau Ceti velocities

    CERN Document Server

    Tuomi, Mikko; Jenkins, James S; Tinney, Chris G; Butler, R Paul; Vogt, Steve S; Barnes, John R; Wittenmyer, Robert A; O'Toole, Simon; Horner, Jonathan; Bailey, Jeremy; Carter, Brad D; Wright, Duncan J; Salter, Graeme S; Pinfield, David

    2012-01-01

    The abilities of radial velocity exoplanet surveys to detect the lowest-mass extra-solar planets are currently limited by a combination of instrument precision, lack of data, and "jitter". Jitter is a general term for any unknown features in the noise, and reflects a lack of detailed knowledge of stellar physics (asteroseismology, starspots, magnetic cycles, granulation, and other stellar surface phenomena), as well as the possible underestimation of instrument noise. We study an extensive set of radial velocities for the star HD 10700 ($\\tau$ Ceti) to determine the properties of the jitter arising from stellar surface inhomogeneities, activity, and telescope-instrument systems, and perform a comprehensive search for planetary signals in the radial velocities. We perform Bayesian comparisons of statistical models describing the radial velocity data to quantify the number of significant signals and the magnitude and properties of the excess noise in the data. We reach our goal by adding artificial signals to t...

  1. Photoelectric Radial Velocities, Paper XX 45 Years’ Monitoring of the Radial Velocities of the Redman K Stars

    Indian Academy of Sciences (India)

    R. F. Griffin; A. Stroe

    2012-06-01

    The ‘Redman K stars’ are a group of 80-odd seventh-magnitude late-type stars, nearly all giants, distributed along the Galactic equator between approximate longitudes 50° and 150° (roughly Sagitta to Cassiopeia). Their radial velocities have been measured systematically once per season in 30 of the 45 seasons from 1966 to 2010/11. At least 26 of them (30%) have proved to vary in velocity. Orbits have been derived for all but one of the 26, many of them having longer periods than have normally been associated with spectroscopic binaries; several are comparable with, or longer than, the present duration of the observing campaign. Also reported here are radial-velocity measurements made casually of stars seen in the fields of some of the Redman stars. Two of the companions have proved to vary in velocity on long time-scales, and (somewhat preliminary) orbits are given for them.

  2. Precision radial velocities of 15 M5 - M9 dwarfs

    CERN Document Server

    Barnes, J R; Jones, H R A; Jeffers, S V; Rojo, P; Arriagada, P; Jordan, A; Minniti, D; Tuomi, M; Pinfield, D; Anglada-Escude, G

    2014-01-01

    We present radial velocity measurements of a sample of M5V-M9V stars from our Red-Optical Planet Survey, ROPS, operating at 0.65-1.025 micron. Radial velocities for 15 stars, with r.m.s. precision down to 2.5 m/s over a week long time scale are achieved using Thorium-Argon reference spectra. We are sensitive to planets with m_psin(i) >= 1.5 MEarth (3 MEarth at 2-sigma) in the classical habitable zone and our observations currently rule out planets with m_psin(i) > 0.5 MJup at 0.03 AU for all our targets. A total of 9 of the 15 targets exhibit r.m.s. 10 MEarth in 0.03 AU orbits. Since the mean rotation velocity is of order 8 km/s for an M6V star and 15 km/s by M9V, we avoid observing only slow rotators that would introduce a bias towards low axial inclination i << 90 deg systems, which are unfavourable for planet detection. Our targets with the highest vsini values exhibit radial velocities significantly above the photon-noise limited precision, even after accounting for vsini. We therefore monitored st...

  3. Accelerated radial Fourier-velocity encoding using compressed sensing

    Energy Technology Data Exchange (ETDEWEB)

    Hilbert, Fabian; Han, Dietbert [Wuerzburg Univ. (Germany). Inst. of Radiology; Wech, Tobias; Koestler, Herbert [Wuerzburg Univ. (Germany). Inst. of Radiology; Wuerzburg Univ. (Germany). Comprehensive Heart Failure Center (CHFC)

    2014-10-01

    Purpose:Phase Contrast Magnetic Resonance Imaging (MRI) is a tool for non-invasive determination of flow velocities inside blood vessels. Because Phase Contrast MRI only measures a single mean velocity per voxel, it is only applicable to vessels significantly larger than the voxel size. In contrast, Fourier Velocity Encoding measures the entire velocity distribution inside a voxel, but requires a much longer acquisition time. For accurate diagnosis of stenosis in vessels on the scale of spatial resolution, it is important to know the velocity distribution of a voxel. Our aim was to determine velocity distributions with accelerated Fourier Velocity Encoding in an acquisition time required for a conventional Phase Contrast image. Materials and Methods:We imaged the femoral artery of healthy volunteers with ECG - triggered, radial CINE acquisition. Data acquisition was accelerated by undersampling, while missing data were reconstructed by Compressed Sensing. Velocity spectra of the vessel were evaluated by high resolution Phase Contrast images and compared to spectra from fully sampled and undersampled Fourier Velocity Encoding. By means of undersampling, it was possible to reduce the scan time for Fourier Velocity Encoding to the duration required for a conventional Phase Contrast image. Results:Acquisition time for a fully sampled data set with 12 different Velocity Encodings was 40 min. By applying a 12.6 - fold retrospective undersampling, a data set was generated equal to 3:10 min acquisition time, which is similar to a conventional Phase Contrast measurement. Velocity spectra from fully sampled and undersampled Fourier Velocity Encoded images are in good agreement and show the same maximum velocities as compared to velocity maps from Phase Contrast measurements. Conclusion: Compressed Sensing proved to reliably reconstruct Fourier Velocity Encoded data. Our results indicate that Fourier Velocity Encoding allows an accurate determination of the velocity

  4. Radial Velocity Data Analysis with Compressed Sensing Techniques

    Science.gov (United States)

    Hara, Nathan C.; Boué, G.; Laskar, J.; Correia, A. C. M.

    2016-09-01

    We present a novel approach for analysing radial velocity data that combines two features: all the planets are searched at once and the algorithm is fast. This is achieved by utilizing compressed sensing techniques, which are modified to be compatible with the Gaussian processes framework. The resulting tool can be used like a Lomb-Scargle periodogram and has the same aspect but with much fewer peaks due to aliasing. The method is applied to five systems with published radial velocity data sets: HD 69830, HD 10180, 55 Cnc, GJ 876 and a simulated very active star. The results are fully compatible with previous analysis, though obtained more straightforwardly. We further show that 55 Cnc e and f could have been respectively detected and suspected in early measurements from the Lick observatory and Hobby-Eberly Telescope available in 2004, and that frequencies due to dynamical interactions in GJ 876 can be seen.

  5. Radial Velocity Data Analysis with Compressed Sensing Techniques

    CERN Document Server

    Hara, Nathan C; Laskar, Jacques; Correia, Alexandre C M

    2016-01-01

    We present a novel approach for analysing radial velocity data that combines two features: all the planets are searched at once and the algorithm is fast. This is achieved by utilizing compressed sensing techniques, which are modified to be compatible with the Gaussian processes framework. The resulting tool can be used like a Lomb-Scargle periodogram and has the same aspect but with much fewer peaks due to aliasing. The method is applied to five systems with published radial velocity data sets: HD 69830, HD 10180, 55 Cnc, GJ 876 and a simulated very active star. The results are fully compatible with previous analysis, though obtained more straightforwardly. We further show that 55 Cnc e and f could have been respectively detected and suspected in early measurements from the Lick observatory and Hobby-Eberly Telescope available in 2004, and that frequencies due to dynamical interactions in GJ 876 can be seen.

  6. Radial velocity data analysis with compressed sensing techniques

    Science.gov (United States)

    Hara, Nathan C.; Boué, G.; Laskar, J.; Correia, A. C. M.

    2017-01-01

    We present a novel approach for analysing radial velocity data that combines two features: all the planets are searched at once and the algorithm is fast. This is achieved by utilizing compressed sensing techniques, which are modified to be compatible with the Gaussian process framework. The resulting tool can be used like a Lomb-Scargle periodogram and has the same aspect but with much fewer peaks due to aliasing. The method is applied to five systems with published radial velocity data sets: HD 69830, HD 10180, 55 Cnc, GJ 876 and a simulated very active star. The results are fully compatible with previous analysis, though obtained more straightforwardly. We further show that 55 Cnc e and f could have been respectively detected and suspected in early measurements from the Lick Observatory and Hobby-Eberly Telescope available in 2004, and that frequencies due to dynamical interactions in GJ 876 can be seen.

  7. A Goldilocks principle for modeling radial velocity noise

    CERN Document Server

    Feng, Fabo; Jones, H R A; Butler, R P; Vogt, S

    2016-01-01

    The doppler measurements of stars are diluted and distorted by stellar activity noise. Different choices of noise models and statistical methods have led to much controversy in the confirmation of exoplanet candidates obtained through analysing radial velocity data. To quantify the limitation of various models and methods, we compare different noise models and signal detection criteria for various simulated and real data sets in the Bayesian framework. According to our analyses, the white noise model tend to interpret noise as signal, leading to false positives. On the other hand, the red noise models are likely to interprete signal as noise, resulting in false negatives. We find that the Bayesian information criterion combined with a Bayes factor threshold of 150 can efficiently rule out false positives and confirm true detections. We further propose a Goldilocks principle aimed at modeling radial velocity noise to avoid too many false positives and too many false negatives. We propose that the noise model w...

  8. Differential Radial Velocities and Stellar Parameters of Nearby Young Stars

    CERN Document Server

    Yelda, D P S

    2006-01-01

    Radial velocity searches for substellar mass companions have focused primarily on stars older than 1 Gyr. Increased levels of stellar activity in young stars hinders the detection of solar system analogs and therefore there has been a prejudice against inclusion of young stars in radial velocity surveys until recently. Adaptive optics surveys of young stars have given us insight into the multiplicity of young stars but only for massive, distant companions. Understanding the limit of the radial velocity technique, restricted to high-mass, close-orbiting planets and brown dwarfs, we began a survey of young stars of various ages. While the number of stars needed to carry out full analysis of the problems of planetary and brown dwarf population and evolution is large, the beginning of such a sample is included here. We report on 61 young stars ranging in age from beta Pic association (~12 Myr) to the Ursa Majoris association (~300 Myr). This initial search resulted in no stars showing evidence for companions grea...

  9. The Radial Velocity Experiment (RAVE): first data release

    CERN Document Server

    Steinmetz, M; Siebert, A; Watson, F G; Freeman, K C; Munari, U; Campbell, R; Williams, M; Seabroke, G M; Wyse, R F G; Parker, Q A; Bienaymé, O; Röser, S; Gibson, B K; Gilmore, G; Grebel, E K; Helmi, A; Navarro, J F; Burton, D; Cass, C J P; Dawe, J A; Fiegert, K; Hartley, M; Russell, K S; Saunders, W; Enke, H; Bailin, J; Binney, J; Bland-Hawthorn, J; Boeche, C; Dehnen, W; Eisenstein, D J; Evans, N W; Fiorucci, M; Fulbright, J P; Gerhard, O; Jauregi, U; Kelz, A; Mijovic, L; Minchev, I; Parmentier, G; Penarrubia, J; Quillen, A C; Read, M A; Ruchti, G; Scholz, R D; Siviero, A; Smith, M C; Sordo, R; Veltz, L; Vidrih, S; Von Berlepsch, R; Boyle, B J; Schilbach, E

    2006-01-01

    We present the first data release of the Radial Velocity Experiment (RAVE), an ambitious spectroscopic survey to measure radial velocities and stellar atmosphere parameters (temperature, metallicity, surface gravity) of up to one million stars using the 6dF multi-object spectrograph on the 1.2-m UK Schmidt Telescope of the Anglo-Australian Observatory (AAO). The RAVE program started in 2003, obtaining medium resolution spectra (median R=7,500) in the Ca-triplet region ($\\lambda\\lambda$ 8,410--8,795 \\AA) for southern hemisphere stars drawn from the Tycho-2 and SuperCOSMOS catalogs, in the magnitude range 9radial velocities for 24,748 individual stars (25,274 measurements when including re-observations). Those data were obtained on 67 nights between 11 April 2003 to 03 April 2004. The total sky coverage within this data release is $\\sim$4,760 square degrees. The average signal to noise ratio of the observed spectra is 29.5, and 80% of t...

  10. Investigation of gravity waves using horizontally resolved radial velocity measurements

    Directory of Open Access Journals (Sweden)

    G. Stober

    2013-06-01

    Full Text Available The Middle Atmosphere Alomar Radar System (MAARSY on the island Andøya in Northern Norway (69.3° N, 16.0° E observes polar mesospheric summer echoes (PMSE. These echoes are used as tracers of atmospheric dynamics to investigate the horizontal wind variability at high temporal and spatial resolution. MAARSY has the capability of a pulse-to-pulse beam steering allowing for systematic scanning experiments to study the horizontal structure of the backscatterers as well as to measure the radial velocities for each beam direction. Here we present a method to retrieve gravity wave parameters from these horizontally resolved radial wind variations by applying velocity azimuth display and volume velocity processing. Based on the observations a detailed comparison of the two wind analysis techniques is carried out in order to determine the zonal and meridional wind as well as to measure first order inhomogeneities. Further, we demonstrate the possibility to resolve the horizontal wave properties, e.g. horizontal wavelength, phase velocity and propagation direction. The robustness of the estimated gravity wave parameters is tested by a simple atmospheric model.

  11. Investigation of gravity waves using horizontally resolved radial velocity measurements

    Science.gov (United States)

    Stober, G.; Sommer, S.; Rapp, M.; Latteck, R.

    2013-10-01

    The Middle Atmosphere Alomar Radar System (MAARSY) on the island of Andøya in Northern Norway (69.3° N, 16.0° E) observes polar mesospheric summer echoes (PMSE). These echoes are used as tracers of atmospheric dynamics to investigate the horizontal wind variability at high temporal and spatial resolution. MAARSY has the capability of pulse-to-pulse beam steering allowing for systematic scanning experiments to study the horizontal structure of the backscatterers as well as to measure the radial velocities for each beam direction. Here we present a method to retrieve gravity wave parameters from these horizontally resolved radial wind variations by applying velocity azimuth display and volume velocity processing. Based on the observations a detailed comparison of the two wind analysis techniques is carried out in order to determine the zonal and meridional wind as well as to measure first-order inhomogeneities. Further, we demonstrate the possibility to resolve the horizontal wave properties, e.g., horizontal wavelength, phase velocity and propagation direction. The robustness of the estimated gravity wave parameters is tested by a simple atmospheric model.

  12. Investigation of gravity waves using horizontally resolved radial velocity measurements

    Directory of Open Access Journals (Sweden)

    G. Stober

    2013-10-01

    Full Text Available The Middle Atmosphere Alomar Radar System (MAARSY on the island of Andøya in Northern Norway (69.3° N, 16.0° E observes polar mesospheric summer echoes (PMSE. These echoes are used as tracers of atmospheric dynamics to investigate the horizontal wind variability at high temporal and spatial resolution. MAARSY has the capability of pulse-to-pulse beam steering allowing for systematic scanning experiments to study the horizontal structure of the backscatterers as well as to measure the radial velocities for each beam direction. Here we present a method to retrieve gravity wave parameters from these horizontally resolved radial wind variations by applying velocity azimuth display and volume velocity processing. Based on the observations a detailed comparison of the two wind analysis techniques is carried out in order to determine the zonal and meridional wind as well as to measure first-order inhomogeneities. Further, we demonstrate the possibility to resolve the horizontal wave properties, e.g., horizontal wavelength, phase velocity and propagation direction. The robustness of the estimated gravity wave parameters is tested by a simple atmospheric model.

  13. VizieR Online Data Catalog: Radial velocity and photometry for GJ3470 (Bonfils+, 2012)

    Science.gov (United States)

    Bonfils, X.; Gillon, M.; Udry, S.; Armstrong, D.; Bouchy, F.; Delfosse, X.; Forveille, T.; Fumel, A.; Jehin, E.; Lendl, M.; Lovis, C.; Mayor, M.; McCormac, J.; Neves, V.; Pepe, F.; Perrier, C.; Pollaco, D.; Queloz, D.; Santos, N. C.

    2012-11-01

    The tables contain radial-velocity and photometry time series of GJ3470. Radial velocities were obtained with he HARPS spectrograph. Photometry was obtained with TRAPPIST, EulerCam and NITES telescopes. (5 data files).

  14. The Radial Velocity Precision of Fiber-fed Spectrographs

    CERN Document Server

    Walker, G A H; Bohlender, D A; Yang, S; Walker, Gordon A.H.; Shkolnik, Evgenya; Bohlender, David A.; Yang, Stephenson

    2003-01-01

    We have measured the radial velocities of five 51 Peg-type stars and one star with constant velocity. Our measurements, on 20 \\AA centered at 3947 \\AA, were conventional using Th/Ar comparison spectra taken every 20 or 40 minutes between the stellar exposures. Existing IRAF routines were used for the reduction. We find $\\sigma_{RV}$ $\\leq$ 20 m s$^{-1}$, provided 4 measurements (out of 72) with residuals $>5\\sigma_{RV}$ are neglected. The observations were made with the CFHT Gecko spectrograph, fiber-fed with the CAFE system (R$\\sim$110,000). $\\sigma_{RV}$ $\\leq$10 m s$^{-1}$ seems possible with additional care. This study was incidental to the main program and so not exhaustive but the small value of $\\sigma_{RV}$ implies that the fiber feed/image slicer system on Gecko + CAFE, essentially eliminates the long standing problem of guiding errors in radial velocity measurements. We are not suggesting this conventional approach for serious Doppler planet searches (especially with Gecko which has such a small mul...

  15. Precise Masses for Wolf 1062 AB from Hubble Space Telescope Interferometric Astrometry and McDonald Observatory Radial Velocities

    CERN Document Server

    Benedict, G F; Franz, O G; Wasserman, L H; Henry, T J; Takato, T; Strateva, I V; Crawford, J L; Ianna, P A; McCarthy, D W; Nelan, E; Jefferys, W H; Van Altena, W F; Shelus, P J; Hemenway, P D; Duncombe, R L; Story, D; Whipple, A L; Bradley, A J; Fredrick, L W

    2001-01-01

    We present an analysis of astrometric data from FGS 3, a white-light interferometer on {\\it HST}, and of radial velocity data from two ground-based campaigns. We model the astrometric and radial velocity measurements simultaneously to obtain parallax, proper motion and component masses for Wolf 1062 = Gl 748 AB (M3.5V). To derive the mass fraction, we relate FGS 3 fringe scanning observations of the science target to a reference frame provided by fringe tracking observations of a surrounding star field. We obtain an absolute parallax $\\pi_{abs} = 98.0 \\pm 0.4$ milliseconds of arc, yielding ${\\cal M}_A = 0.379 \\pm 0.005{\\cal M}_{\\sun}$ and ${\\cal M}_B= 0.192 \\pm 0.003 {\\cal M}_{\\sun}$, high quality component masses with errors of only 1.5%.

  16. A Radial Velocity Survey for LMC Microlensed Sources

    CERN Document Server

    Zhao, H S

    1999-01-01

    We propose a radial velocity survey with the aim to resolve the current dispute between the pro-macho camp and the pro-star camp on whether the lensing is caused by halo white dwarfs or machos in general or by stars in various observed or hypothesized structures of the Magellanic Clouds and the Galaxy. Star-star lensing should prefer sources at the backside or behind the LMC disc because lensing is most efficient if the source is located a few kpc behind a dense screen of stars, here the thin disc of the LMC. This signature of self-lensing can be looked for by a radial velocity survey since kinematics of the stars at the back can be markedly different from that of the majority of stars in the cold, rapidly rotating disc of the LMC. Detailed simulations of effect together with optimal strategies of carrying out the proposed survey are reported here. Assuming that the existing 30 or so alerted stars in the LMC are truely microlensed stars, their kinematics can test the two lensing scenarios; the confidence leve...

  17. An extensive radial velocity survey toward NGC 6253

    CERN Document Server

    Montalto, M; Santos, N C; Queloz, D; Piotto, G; Desidera, S; Bedin, L R; Momany, Y; Saviane, I

    2016-01-01

    The old and metal rich open cluster NGC 6253 was observed with the FLAMES multi-object spectrograph during an extensive radial velocity campaign monitoring 317 stars with a median of 15 epochs per object. All the targeted stars are located along the upper main sequence of the cluster between 14.8 $<$ V $<$ 16.5. Fifty nine stars are confirmed cluster members both by radial velocities and proper motions and do not show evidence of variability. We detected 45 variable stars among which 25 belong to NGC 6253. We were able to derive an orbital solution for 4 cluster members (and for 2 field stars) yielding minimum masses in between $\\sim$90 M$\\rm_J$ and $\\sim$460 M$\\rm_J$ and periods between 3 and 220 days. Simulations demonstrated that this survey was sensitive to objects down to 30 M$\\rm_J$ at 10 days orbital periods with a detection efficiency equal to 50%. On the basis of these results we concluded that the observed frequency of binaries down to the hydrogen burning limit and up to 20 days orbital perio...

  18. New systemic radial velocities of suspected RR Lyrae binary stars

    CERN Document Server

    Guggenberger, Elisabeth; Kolenberg, Katrien

    2015-01-01

    Among the tens of thousands of known RR Lyrae stars there are only a handful that show indications of possible binarity. The question why this is the case is still unsolved, and has recently sparked several studies dedicated to the search for additional RR Lyraes in binary systems. Such systems are particularly valuable because they might allow to constrain the stellar mass. Most of the recent studies, however, are based on photometry by finding a light time effect in the timings of maximum light. This approach is a very promising and successful one, but it has a major drawback: by itself, it cannot serve as a definite proof of binarity, because other phenomena such as the Blazhko effect or intrinsic period changes could lead to similar results. Spectroscopic radial velocity measurements, on the other hand, can serve as definite proof of binarity. We have therefore started a project to study spectroscopically RR Lyrae stars that are suspected to be binaries. We have obtained radial velocity (RV) curves with t...

  19. Radial Velocities of Stars with Multiple Co-orbital Planets

    CERN Document Server

    Dobrovolskis, Anthony R

    2014-01-01

    To date, well over a thousand planets have been discovered orbiting other stars, hundreds of them in multi-planet systems. Most of these exoplanets have been detected by either the transit method or the radial velocity method, rather than by other methods such as astrometry or direct imaging. Both the radial velocity and astrometric methods rely upon the reflex motion of the parent star induced by the gravitational attraction of its planets. However, this reflex motion is subject to misinterpretation when a star has two or more planets with the same orbital period. Such co-orbital planets may effectively "hide" from detection by current algorithms. In principle, any number of planets can share the same orbit; the case where they all have the same mass has been studied most. Salo and Yoder (A & A 205, 309--327, 1988) have shown that more than 8 planets of equal mass sharing a circular orbit must be equally spaced for dynamical stability, while fewer than 7 equal-mass planets are stable only in a configurat...

  20. The Radial Velocity Experiment (RAVE): Fifth Data Release

    CERN Document Server

    Kunder, Andrea; Steinmetz, Matthias; Zwitter, Tomaz; McMillan, Paul; Casagrande, Luca; Enke, Harry; Wojno, Jennifer; Valentini, Marica; Chiappini, Cristina; Matijevic, Gal; Siviero, Alessandro; de Laverny, Patrick; Recio-Blanco, Alejandra; Bijaoui, Albert; Wyse, Rosemary F G; Binney, James; Grebel, E K; Helmi, Amina; Jofre, Paula; Gilmore, Gerard; Siebert, Arnaud; Famaey, Benoit; Bienayme, Olivier; Gibson, Brad K; Freeman, Kenneth C; Navarro, Julio F; Munari, Ulisse; Seabroke, George; Jimenez, Borja Anguiano; Reid, Warren; Bland-Hawthorn, Joss; Watson, Fred; Gerhard, Ortwin; Davies, G R; Elsworth, Y P; Lund, M; Miglio, A; Chaplin, W J; Mosser, B

    2016-01-01

    Data Release 5 (DR5) of the Radial Velocity Experiment (RAVE) is the fifth data release from a magnitude-limited (9< I < 12) survey of stars randomly selected in the southern hemisphere. The RAVE medium-resolution spectra (R~7500) covering the Ca-triplet region (8410-8795 A) span the complete time frame from the start of RAVE observations in 2003 to their completion in 2013. Radial velocities from 520,781 spectra of 457,588 unique stars are presented, of which more than 200,000 are expected to have parallaxes and proper motions from the Tycho-Gaia astrometric solution (TGAS) in Gaia DR1. For our main DR5 catalog, stellar parameters (effective temperature, surface gravity, overall metallicity) are computed using the RAVE DR4 stellar pipeline, but calibrated using recent K2 Campaign 1 seismic gravities and Gaia benchmark stars, as well as results obtained from high-resolution studies. Also included are temperatures from the Infrared Flux Method, and we provide a catalogue of red giant stars in the deredde...

  1. A Goldilocks principle for modelling radial velocity noise

    Science.gov (United States)

    Feng, F.; Tuomi, M.; Jones, H. R. A.; Butler, R. P.; Vogt, S.

    2016-09-01

    The Doppler measurements of stars are diluted and distorted by stellar activity noise. Different choices of noise models and statistical methods have led to much controversy in the confirmation of exoplanet candidates obtained through analysing radial velocity data. To quantify the limitation of various models and methods, we compare different noise models and signal detection criteria for various simulated and real data sets in the Bayesian framework. According to our analyses, the white noise model tend to interpret noise as signal, leading to false positives. On the other hand, the red noise models are likely to interpret signal as noise, resulting in false negatives. We find that the Bayesian information criterion combined with a Bayes factor threshold of 150 can efficiently rule out false positives and confirm true detections. We further propose a Goldilocks principle aimed at modelling radial velocity noise to avoid too many false positives and too many false negatives. We propose that the noise model with RHK-dependent jitter is used in combination with the moving average model to detect planetary signals for M dwarfs. Our work may also shed light on the noise modelling for hotter stars, and provide a valid approach for finding similar principles in other disciplines.

  2. The Radial Velocity Experiment (RAVE): second data release

    CERN Document Server

    Zwitter, T; Munari, U; Freeman, K C; Siviero, A; Watson, F G; Fulbright, J P; Wyse, R F G; Campbell, R; Seabroke, G M; Williams, M; Steinmetz, M; Bienaymé, O; Gilmore, G; Grebel, E K; Helmi, A; Navarro, J F; Anguiano, B; Boeche, C; Burton, D; Cass, P; Dawe, J; Fiegert, K; Hartley, M; Russell, K; Veltz, L; Bailin, J; Binney, J; Bland-Hawthorn, J; Brown, A; Dehnen, W; Evans, N W; Fiorentin, P Re; Fiorucci, M; Gerhard, O; Gibson, B; Kelz, A; Kujken, K; Matijevic, G; Minchev, I; Parker, Q A; Penarrubia, J; Quillen, A; Read, M A; Reid, W; Röser, S; Ruchti, G; Scholz, R -D; Smith, M C; Sordo, R; Tolstoi, E; Tomasella, L; Vidrih, S; de Boer, E Wylie

    2008-01-01

    We present the second data release of the Radial Velocity Experiment (RAVE), an ambitious spectroscopic survey to measure radial velocities (RVs) and stellar atmosphere parameters of up to one million stars using the 6dF multi-object spectrograph on the 1.2-m UK Schmidt Telescope of the Anglo-Australian Observatory (AAO). It is obtaining medium resolution spectra (median R=7,500) in the Ca-triplet region (8,410--8,795 \\AA) for southern hemisphere stars in the magnitude range 9

  3. What velocities and eccentricities tell us about radial migration

    Directory of Open Access Journals (Sweden)

    Schönrich R.

    2012-02-01

    Full Text Available This note attempts to interpret some of the recent findings about a downtrend in the mean azimuthal velocity of low [α/Fe] thin disc stars with increasing metallicity. The presence of such a trend was predicted in the model of [19], albeit with a slightly steeper slope. We show that in a simple picture a Galactic disc without mixing in angular momenta would display an exceedingly steep trend, while in the case of complete mixing of all stars the trend has to vanish. The difference between model and observational data can hence be interpreted as the consequence of the radial abundance gradient in the model being too high resulting in an underestimate of the migration strength. We shortly discuss the value of eccentricity distributions in constraining structure and history of the Galactic disc.

  4. Monolithic interferometer for high precision radial velocity measurements

    Science.gov (United States)

    Wan, Xiaoke; Ge, Jian; Wang, Ji; Lee, Brian

    2009-08-01

    In high precision radial velocity (RV) measurements for extrasolar planets searching and studies, a stable wide field Michelson interferometer is very critical in Exoplanet Tracker (ET) instruments. Adopting a new design, monolithic interferometers are homogenous and continuous in thermal expansion, and field compensation and thermal compensation are both satisfied. Interferometer design and fabrication are decrypted in details. In performance evaluations, field angle is typically 22° and thermal sensitivity is typically -1.7 x 10-6/°C, which corresponds to ~500 m/s /°C in RV scale. In interferometer stability monitoring using a wavelength stabilized laser source, phase shift data was continuously recorded for nearly seven days. Appling a frequent calibration every 30 minutes as in typical star observations, the interferometer instability contributes less than 1.4 m/s in RV error, in a conservative estimation.

  5. Common Radial Velocity vs. Rare Microlensing: Difficulties and Futures

    CERN Document Server

    Molaverdikhani, Karan

    2010-01-01

    In this paper, effective factors for success of Microlensing and Radial Velocity methods were choose. A semi-Delphi process applied on the factors to evaluating them and finding the most important factors for present situation of ML and RV, with help from about 100 experts, in or related exoplanets detection. I found the public definition on "success of exoplanets detection methods" is not correct and we should change it, as some experts did it, in the form of fundamental questions in planetary science. Also, the views of "Special Experts" are different from other experts that help us to choose the right way in evaluating. The next step was choosing the best strategy for future and finally, from SWOT landscape and with a new objective of ML method (New Game Board Strategy) I suggested four critical future strategies for completing current strategic directions.

  6. MARVELS Radial Velocity Solutions to Seven Kepler Eclipsing Binaries

    Science.gov (United States)

    Heslar, Michael Francis; Thomas, Neil B.; Ge, Jian; Ma, Bo; Herczeg, Alec; Reyes, Alan; SDSS-III MARVELS Team

    2016-01-01

    Eclipsing binaries serve momentous purposes to improve the basis of understanding aspects of stellar astrophysics, such as the accurate calculation of the physical parameters of stars and the enigmatic mass-radius relationship of M and K dwarfs. We report the investigation results of 7 eclipsing binary candidates, initially identified by the Kepler mission, overlapped with the radial velocity observations from the SDSS-III Multi-Object APO Radial-Velocity Exoplanet Large-Area Survey (MARVELS). The RV extractions and spectroscopic solutions of these eclipsing binaries were generated by the University of Florida's 1D data pipeline with a median RV precision of ~60-100 m/s, which was utilized for the DR12 data release. We performed the cross-reference fitting of the MARVELS RV data and the Kepler photometric fluxes obtained from the Kepler Eclipsing Binary Catalog (V2) and modelled the 7 eclipsing binaries in the BinaryMaker3 and PHOEBE programs. This analysis accurately determined the absolute physical and orbital parameters of each binary. Most of the companion stars were determined to have masses of K and M dwarf stars (0.3-0.8 M⊙), and allowed for an investigation into the mass-radius relationship of M and K dwarfs. Among the cases are KIC 9163796, a 122.2 day period "heartbeat star", a recently-discovered class of eccentric binaries known for tidal distortions and pulsations, with a high eccentricity (e~0.75) and KIC 11244501, a 0.29 day period, contact binary with a double-lined spectrum and mass ratio (q~0.45). We also report on the possible reclassification of 2 Kepler eclipsing binary candidates as background eclipsing binaries based on the analysis of the flux measurements, flux ratios of the spectroscopic and photometric solutions, the differences in the FOVs, the image processing of Kepler, and RV and spectral analysis of MARVELS.

  7. VizieR Online Data Catalog: Radial velocities for 1309 stars and 166 OCl (Mermilliod+, 2008)

    Science.gov (United States)

    Mermilliod, J.-C.; Mayor, M.; Udry, S.

    2008-02-01

    We present the final catalogues of a long term observing program performed with the two Coravel spectrovelocimeters for red giants in open clusters. The main aims were to detect spectroscopic binaries and determine their orbital parameters, determine the membership, and compute mean velocities for the stars and open clusters. We computed weighted mean radial velocities for 1309 stars from 10517 individual observations, including the systemic radial velocities from spectroscopic orbits and for Cepheids. The final results are contained in three catalogues collecting 10517 individual radial velocities, mean radial velocities for 1309 red giants, and mean radial velocities for 166 open clusters, among which 57 are new determinations. We identify 891 members and 418 non-members. We discovered a total of 288 spectroscopic binaries, among which 57 were classified as non-members. In addition 27 stars were judged to be variable in radial velocities, all of them being red supergiants. (5 data files).

  8. A test field for Gaia. Radial velocity catalogue of stars in the South Ecliptic Pole

    Science.gov (United States)

    Frémat, Y.; Altmann, M.; Pancino, E.; Soubiran, C.; Jofré, P.; Damerdji, Y.; Heiter, U.; Royer, F.; Seabroke, G.; Sordo, R.; Blanco-Cuaresma, S.; Jasniewicz, G.; Martayan, C.; Thévenin, F.; Vallenari, A.; Blomme, R.; David, M.; Gosset, E.; Katz, D.; Viala, Y.; Boudreault, S.; Cantat-Gaudin, T.; Lobel, A.; Meisenheimer, K.; Nordlander, T.; Raskin, G.; Royer, P.; Zorec, J.

    2017-01-01

    Context. Gaia is a space mission that is currently measuring the five astrometric parameters, as well as spectrophotometry of at least 1 billion stars to G = 20.7 mag with unprecedented precision. The sixth parameter in phase space (i.e., radial velocity) is also measured thanks to medium-resolution spectroscopy that is being obtained for the 150 million brightest stars. During the commissioning phase, two fields, one around each ecliptic pole, have been repeatedly observed to assess and to improve the overall satellite performances, as well as the associated reduction and analysis software. A ground-based photometric and spectroscopic survey was therefore initiated in 2007, and is still running to gather as much information as possible about the stars in these fields. This work is of particular interest to the validation of the radial velocity spectrometer outputs. Aims: The paper presents the radial velocity measurements performed for the Southern targets in the 12-17 R magnitude range on high- to mid-resolution spectra obtained with the GIRAFFE and UVES spectrographs. Methods: Comparison of the South Ecliptic Pole (SEP) GIRAFFE data to spectroscopic templates observed with the HERMES (Mercator in La Palma, Spain) spectrograph enabled a first coarse characterisation of the 747 SEP targets. Radial velocities were then obtained by comparing the results of three different methods. Results: In this paper, we present an initial overview of the targets to be found in the 1 sq. deg SEP region that was observed repeatedly by Gaia ever since its commissioning. In our representative sample, we identified one galaxy, six LMC S-stars, nine candidate chromospherically active stars, and confirmed the status of 18 LMC Carbon stars. A careful study of the 3471 epoch radial velocity measurements led us to identify 145 RV constant stars with radial velocities varying by less than 1 km s-1. Seventy-eight stars show significant RV scatter, while nine stars show a composite spectrum

  9. A radial velocity study of the intermediate polar EX Hydrae

    Science.gov (United States)

    Echevarría, J.; Ramírez-Torres, A.; Michel, R.; Hernández Santisteban, J. V.

    2016-09-01

    A study on the intermediate polar EX Hya is presented, based on simultaneous photometry and high-dispersion spectroscopic observations, during four consecutive nights. The strong photometric modulation related to the 67-min spin period of the primary star is clearly present, as well as the narrow eclipses associated with the orbital modulation. Since our eclipse timings have been obtained almost 91 000 cycles since the last reported observations, we present new linear ephemeris, although we cannot rule out a sinusoidal variation suggested by previous authors. The system shows double-peaked H α, H β and He I λ5876 Å emission lines, with almost no other lines present. As H α is the only line with enough S/N ratio in our observations, we have concentrated our efforts in its study, in order to obtain a reliable radial velocity semi-amplitude. From the profile of this line, we find two important components; one with a steep rise and velocities not larger than ˜1000 km s-1 and another broader component extending up to ˜2000 km s-1, which we interpret as coming mainly from the inner disc. A strong and variable hotspot is found and a stream-like structure is seen at times. We show that the best solution correspond to K1 = 58 ± 5 km s-1 from H α, from the two emission components, which are both in phase with the orbital modulation. We remark on a peculiar effect in the radial velocity curve around phase zero, which could be interpreted as a Rositter-MacLaughlin-like effect, which has been taken into account before deriving K1. This value is compatible with the values found in high resolution both in the ultraviolet and X-ray. Using the published inclination angle of i =78° ± 1° and semi-amplitude K2 = 432 ± 5 km s-1, we find: M1 = 0.78 ± 0.03 M⊙, M2 = 0.10 ± 0.02 M⊙ and a = 0.67 ± 0.01 R⊙. Doppler Tomography has been applied, to construct six Doppler tomograms for single orbital cycles spanning the four days of observations to support our conclusions

  10. A Spitzer search for transits of radial velocity detected super-Earths

    Energy Technology Data Exchange (ETDEWEB)

    Kammer, J. A.; Knutson, H. A.; Desert, J.-M. [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Howard, A. W. [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Laughlin, G. P.; Fortney, J. J. [Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Deming, D. [Department of Astronomy, University of Maryland at College Park, College Park, MD 20742 (United States); Todorov, K. O. [Institute for Astronomy, ETH Zürich, CH-8093 Zürich (Switzerland); Agol, E. [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Burrows, A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Showman, A. P. [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States); Lewis, N. K., E-mail: jkammer@caltech.edu [Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2014-02-01

    Unlike hot Jupiters or other gas giants, super-Earths are expected to have a wide variety of compositions, ranging from terrestrial bodies like our own to more gaseous planets like Neptune. Observations of transiting systems, which allow us to directly measure planet masses and radii and constrain atmospheric properties, are key to understanding the compositional diversity of the planets in this mass range. Although Kepler has discovered hundreds of transiting super-Earth candidates over the past 4 yr, the majority of these planets orbit stars that are too far away and too faint to allow for detailed atmospheric characterization and reliable mass estimates. Ground-based transit surveys focus on much brighter stars, but most lack the sensitivity to detect planets in this size range. One way to get around the difficulty of finding these smaller planets in transit is to start by choosing targets that are already known to host super-Earth sized bodies detected using the radial velocity (RV) technique. Here we present results from a Spitzer program to observe six of the most favorable RV-detected super-Earth systems, including HD 1461, HD 7924, HD 156668, HIP 57274, and GJ 876. We find no evidence for transits in any of their 4.5 μm flux light curves, and place limits on the allowed transit depths and corresponding planet radii that rule out even the most dense and iron-rich compositions for these objects. We also observed HD 97658, but the observation window was based on a possible ground-based transit detection that was later ruled out; thus the window did not include the predicted time for the transit detection recently made by the Microvariability and Oscillations of Stars space telescope.

  11. Photonic systems for high precision radial velocity measurements

    Science.gov (United States)

    Halverson, Samuel

    2016-01-01

    I will discuss new instrumentation and techniques designed to maximize the Doppler radial velocity (RV) measurement precision of next generation exoplanet discovery instruments. These systems include a novel wavelength calibration device based on an all-fiber fabry-perot interferometer, a compact and efficient optical fiber image scrambler based on a single high-index ball lens, and a unique optical fiber mode mixer. These systems have been developed specifically to overcome three technological hurdles that have classically hindered high precision RV measurements in both the optical and near-infrared (NIR), namely: lack of available wavelength calibration sources, inadequate decoupling of the spectrograph from variable telescope illumination, and speckle-induced noise due to mode interference in optical fibers. The instrumentation presented here will be applied to the Habitable-zone Planet Finder, a NIR RV instrument designed to detect rocky planets orbiting in the habitable zones of nearby M-dwarfs, and represents a critical technological step towards the detection of potentially habitable Earth-like planets. While primarily focused in the NIR, many of these systems will be adapted to future optical RV instruments as well, such as NASA's new Extreme Precision Doppler Spectrometer for the WIYN telescope.

  12. Comparing radial velocities of atmospheric lines with radiosonde measurements

    CERN Document Server

    Figueira, P; Chacon, A; Lovis, C; Santos, N C; Curto, G Lo; Sarazin, M; Pepe, F

    2011-01-01

    The precision of radial velocity (RV) measurements depends on the precision attained on the wavelength calibration. One of the available options is using atmospheric lines as a natural, freely available wavelength reference. Figueira et al. (2010) measured the RV of O2 lines using HARPS and showed that the scatter was only of ~10 m/s over a timescale of 6 yr. Using a simple but physically motivated empirical model, they demonstrated a precision of 2 m/s, roughly twice the average photon noise contribution. In this paper we take advantage of a unique opportunity to confirm the sensitivity of the telluric absorption lines RV to different atmospheric and observing conditions: by means of contemporaneous in-situ wind measurements by radiosondes. The RV model fitting yielded similar results to that of Figueira et al. (2010), with lower wind magnitude values and varied wind direction. The probes confirmed the average low wind magnitude and suggested that the average wind direction is a function of time as well. The...

  13. CHIRON - A Fiber Fed Spectrometer for Precise Radial Velocities

    CERN Document Server

    Tokovinin, Andrei; Bonati, Marco; Giguere, Matthew J; Moore, Peter; Schwab, Christian; Spronck, Julien F P; Szymkowiak, Andrew

    2013-01-01

    The CHIRON optical high-resolution echelle spectrometer was commissioned at the 1.5m telescope at CTIO in 2011. The instrument was designed for high throughput and stability, with the goal of monitoring radial velocities of bright stars with high precision and high cadence for the discovery of low-mass exoplanets. Spectral resolution of R=79,000 is attained when using a slicer with a total (including telescope and detector) efficiency of 6% or higher, while a resolution of R=136,000 is available for bright stars. A fixed spectral range of 415 to 880 nm is covered. The echelle grating is housed in a vacuum enclosure and the instrument temperature is stabilized to +-0.2deg. Stable illumination is provided by an octagonal multimode fiber with excellent light-scrambling properties. An iodine cell is used for wavelength calibration. We describe the main optics, fiber feed, detector, exposure-meter, and other aspects of the instrument, as well as the observing procedure and data reduction.

  14. Light Curves as Predictors of Good Radial Velocity Planet Search Targets in New Stellar Domains

    Science.gov (United States)

    Bastien, Fabienne A.; Wright, Jason; Sigurdsson, Steinn; Dumusque, Xavier; Luhn, Jacob K.; Howard, Andrew

    2017-01-01

    As Kepler and K2 have collectively found thousands of exoplanet candidates, their discoveries have strained ground-based radial velocity (RV) follow-up resources, which are unable to simultaneously keep up with the pace of transit discoveries by measuring masses for all of the candidates and maintain vigorous RV searches for planets that do not transit their parent star. The burden to the RV community is expected to worsen with the upcoming TESS mission, even as new RV instruments are slated to come online in the coming years. Observations that can enable the RV community to prioritize targets on the basis of their stellar RV variability in advance and, ideally, independently of the RV instruments themselves, can therefore permit us to reserve our RV resources for the stars most likely to yield the highest payoff. We show that the light curves from space-based transit surveys may not only be used as predictors of good RV search targets for the stars predominantly targeted by the exoplanet community but also for stars usually avoided by both RV and transit surveys due to their high intrinsic levels of stellar variability. We also briefly present recommendations to the RV planet search community on how to improve prospects for finding Earth analogs from the recent workshop at the Aspen Center for Physics, “Approaching the Stellar Astrophysical Limits of Exoplanet Detection: Getting to 10cm/s.”

  15. A Spitzer Search for Transits of Radial Velocity Detected Super-Earths

    CERN Document Server

    Kammer, J A; Howard, A W; Laughlin, G P; Deming, D; Todorov, K O; Desert, J -M; Agol, E; Burrows, A; Fortney, J J; Showman, A P; Lewis, N K

    2013-01-01

    Unlike hot Jupiters or other gas giants, super-Earths are expected to have a wide variety of compositions, ranging from terrestrial bodies like our own to more gaseous planets like Neptune. Observations of transiting systems, which allow us to directly measure planet masses and radii and constrain atmospheric properties, are key to understanding the compositional diversity of the planets in this mass range. Although Kepler has discovered hundreds of transiting super-Earth candidates over the past four years, the majority of these planets orbit stars that are too far away and too faint to allow for detailed atmospheric characterization and reliable mass estimates. Ground-based transit surveys focus on much brighter stars, but most lack the sensitivity to detect planets in this size range. One way to get around the difficulty of finding these smaller planets in transit is to start by choosing targets that are already known to contain super-Earth sized bodies detected using the radial velocity technique. Here we...

  16. Characterization of wind velocities in the wake of a full scale wind turbine using three ground-based synchronized WindScanners

    DEFF Research Database (Denmark)

    Yazicioglu, Hasan; Angelou, Nikolas; Mikkelsen, Torben Krogh;

    2016-01-01

    , installed at Risoe test field, has been measured from 0 to 2 diameters downstream. For this, three ground-based synchronised short-range WindScanners and a spinner lidar have been used. The 3D wind velocity field has been reconstructed in horizontal and vertical planes crossing the hub. The 10-min mean...... deficit is calculated both in a Nacelle and Moving Frame of Reference. The results can be used in quantitative validation of numerical wake models....

  17. Pulkovo Compilation of Radial Velocities for 35495 Hipparcos Stars in a Common System

    CERN Document Server

    Gontcharov, George

    2016-01-01

    The Pulkovo Compilation of Radial Velocities (PCRV) has been made to study the stellar kinematics in the local spiral arm. The PCRV contains weighted mean absolute radial velocities for 35 495 Hipparcos stars of various spectral types and luminosity classes over the entire celestial sphere mainly within 500 pc of the Sun. The median accuracy of the radial velocities obtained is 0.7 km s$^{-1}$. Results from 203 publications were used in the catalogue. Four of them were used to improve the radial velocities of standard stars from the IAU list. The radial velocities of 155 standard stars turned out to be constant within 0.3 km s$^{-1}$. These stars were used to analyze 47 768 mean radial velocities for 37 200 stars from 12 major publications ($\\sim80\\%$ of all the data used). Zero-point discrepancies and systematic dependences on radial velocity, $(B-V)$ color index, right ascension, and declination were found in radial velocity differences of the form "publication minus IAU list of standards". These discrepanc...

  18. Advanced structural design for precision radial velocity instruments

    Science.gov (United States)

    Baldwin, Dan; Szentgyorgyi, Andrew; Barnes, Stuart; Bean, Jacob; Ben-Ami, Sagi; Brennan, Patricia; Budynkiewicz, Jamie; Chun, Moo-Young; Conroy, Charlie; Crane, Jeffrey D.; Epps, Harland; Evans, Ian; Evans, Janet; Foster, Jeff; Frebel, Anna; Gauron, Thomas; Guzman, Dani; Hare, Tyson; Jang, Bi-Ho; Jang, Jeong-Gyun; Jordan, Andres; Kim, Jihun; Kim, Kang-Min; Mendes de Oliveira, Claudia; Lopez-Morales, Mercedes; McCracken, Kenneth; McMuldroch, Stuart; Miller, Joseph; Mueller, Mark; Oh, Jae Sok; Ordway, Mark; Park, Byeong-Gon; Park, Chan; Park, Sung-Joon; Paxson, Charles; Phillips, David; Plummer, David; Podgorski, William; Seifahrt, Andreas; Stark, Daniel; Steiner, Joao; Uomoto, Alan; Walsworth, Ronald; Yu, Young-Sam

    2016-07-01

    The GMT-Consortium Large Earth Finder (G-CLEF) is an echelle spectrograph with precision radial velocity (PRV) capability that will be a first light instrument for the Giant Magellan Telescope (GMT). G-CLEF has a PRV precision goal of 40 cm/sec (10 cm/s for multiple measurements) to enable detection of Earth-like exoplanets in the habitable zones of sun-like stars1. This precision is a primary driver of G-CLEF's structural design. Extreme stability is necessary to minimize image motions at the CCD detectors. Minute changes in temperature, pressure, and acceleration environments cause structural deformations, inducing image motions which degrade PRV precision. The instrument's structural design will ensure that the PRV goal is achieved under the environments G-CLEF will be subjected to as installed on the GMT azimuth platform, including: Millikelvin (0.001 °K) thermal soaks and gradients 10 millibar changes in ambient pressure Changes in acceleration due to instrument tip/tilt and telescope slewing Carbon fiber/cyanate composite was selected for the optical bench structure in order to meet performance goals. Low coefficient of thermal expansion (CTE) and high stiffness-to-weight are key features of the composite optical bench design. Manufacturability and serviceability of the instrument are also drivers of the design. In this paper, we discuss analyses leading to technical choices made to minimize G-CLEF's sensitivity to changing environments. Finite element analysis (FEA) and image motion sensitivity studies were conducted to determine PRV performance under operational environments. We discuss the design of the optical bench structure to optimize stiffness-to-weight and minimize deformations due to inertial and pressure effects. We also discuss quasi-kinematic mounting of optical elements and assemblies, and optimization of these to ensure minimal image motion under thermal, pressure, and inertial loads expected during PRV observations.

  19. Extreme Precision Environmental Control for Next Generation Radial Velocity Spectrographs

    Science.gov (United States)

    Stefansson, Gudmundur K.; Hearty, Fred; Levi, Eric; Robertson, Paul; Mahadevan, Suvrath; Bender, Chad; Nelson, Matt; Halverson, Samuel

    2015-12-01

    Extreme radial velocity precisions of order 10cm/s will enable the discoveries of Earth-like planets around solar-type stars. Temperature and pressure variations inside a spectrograph can lead to thermomechanical instabilities in the optics and mounts, and refractive index variations in both the optical elements as well as the surrounding air. Together, these variations can easily induce instrumental drifts of several tens to hundreds of meters per second. Enclosing the full optical train in thermally stabilized high-vacuum environments minimizes such errors. In this talk, I will discuss the Environmental Control System (ECS) for the Habitable Zone Planet Finder (HPF) spectrograph: a near infrared (NIR) facility class instrument we will commission at the Hobby Eberly Telescope in 2016. The ECS will maintain the HPF optical bench stable at 180K at the sub milli-Kelvin level on the timescale of days, and at the few milli-Kelvin level over months to years. The entire spectrograph is kept under high-quality vacuum (compensated for with an actively controlled radiation shield outfitted with custom feedback electronics. High efficiency Multi-Layer Insulation (MLI) blankets, and a passive external thermal enclosure further isolate the optics from ambient perturbations. This environmental control scheme is versatile, suitable to stabilize both next generation NIR, and optical spectrographs. I will show how we are currently testing this control system for use with our design concept of the Extreme Precision Doppler Spectrograph (EPDS), the next generation optical spectrograph for the WIYN 3.5m telescope. Our most recent results from full-scale stability tests will be presented.

  20. Astrophysical supplements to the ASCC-2.5. Ia. Radial velocities of about 55000 stars and mean radial velocities of 516 Galactic open clusters and associations

    CERN Document Server

    Kharchenko, N V; Röser, S; Schilbach, E; Scholz, R -D

    2007-01-01

    We present the 2nd version of the Catalogue of Radial Velocities with Astrometric Data (CRVAD-2). This is the result of the cross-identification of stars from the All-Sky Compiled Catalogue of 2.5 Million Stars (ASCC-2.5) with the General Catalogue of Radial Velocities and with other recently published radial velocity lists and catalogues. The CRVAD-2 includes accurate J2000 equatorial coordinates, proper motions and trigonometric parallaxes in the Hipparcos system, $B, V$ photometry in the Johnson system, spectral types, radial velocities (RVs), multiplicity and variability flags for 54907 ASCC-2.5 stars. We have used the CRVAD-2 for a new determination of mean RVs of 363 open clusters and stellar associations considering their established members from proper motions and photometry in the ASCC-2.5. For 330 clusters and associations we compiled previously published mean RVs from the literature, critically reviewed and partly revised them. The resulting Catalogue of Radial Velocities of Open Clusters and Assoc...

  1. A new infrared Fabry-Pérot-based radial-velocity-reference module for the SPIRou radial-velocity spectrograph

    Science.gov (United States)

    Cersullo, Federica; Wildi, François; Chazelas, Bruno; Pepe, Francesco

    2017-05-01

    Context. The field of exoplanet research is moving towards the detection and characterization of habitable planets. These exo-Earths can be easily found around low-mass stars by using either photometric transit or radial-velocity (RV) techniques. In the latter case the gain is twofold because the signal induced by the planet of a given mass is higher due to the more favourable planet-star mass ratio and because the habitable zone lies closer to the star. However, late-type stars emit mainly in the infrared (IR) wavelength range, which calls for IR instruments. Aims: SPIRou is a stable RV IR spectrograph addressing these ambitious scientific objectives. As with any other spectrograph, calibration and drift monitoring is fundamental to achieve high precision. However, the IR domain suffers from a lack of suitable reference spectral sources. Our goal was to build, test and finally operate a Fabry-Pérot-based RV-reference module able to provide the needed spectral information over the full wavelength range of SPIRou. Methods: We adapted the existing HARPS Fabry-Pérot calibrator for operation in the IR domain. After manufacturing and assembly, we characterized the FP RV-module in the laboratory before delivering it to the SPIRou integration site. In particular, we measured finesse, transmittance, and spectral flux of the system. Results: The measured finesse value of F = 12.8 corresponds perfectly to the theoretical value. The total transmittance at peak is of the order of 0.5%, mainly limited by fibre-connectors and interfaces. Nevertheless, the provided flux is in line with the the requirements set by the SPIRou instrument. Although we could test the stability of the system, we estimated it by comparing the SPIRou Fabry-Pérot with the already operating HARPS system and demonstrated a stability of better than 1 m s-1 during a night. Conclusions: Once installed on SPIRou, we will test the full spectral characteristics and stability of the RV-reference module. The

  2. Precision velocimetry planet hunting with PARAS: current performance and lessons to inform future extreme precision radial velocity instruments

    Science.gov (United States)

    Roy, Arpita; Chakraborty, Abhijit; Mahadevan, Suvrath; Chaturvedi, Priyanka; Prasad, Neelam J. S. S. V.; Shah, Vishal; Pathan, F. M.; Anandarao, B. G.

    2016-08-01

    The PRL Advanced Radial-velocity Abu-sky Search (PARAS) instrument is a fiber-fed stabilized high-resolution cross-dispersed echelle spectrograph, located on the 1.2 m telescope in Mt. Abu India. Designed for exoplanet detection, PARAS is capable of single-shot spectral coverage of 3800 - 9600 Å, and currently achieving radial velocity (RV) precisions approaching 1 m s-1 over several months using simultaneous ThAr calibration. As such, it is one of the few dedicated stabilized fiber-fed spectrographs on small (1-2 m) telescopes that are able to fill an important niche in RV follow-up and stellar characterization. The success of ground-based RV surveys is motivating the push into extreme precisions, with goals of 10 cm s-1 in the optical and <1 m s-1 in the near-infrared (NIR). Lessons from existing instruments like PARAS are invaluable in informing hardware design, providing pipeline prototypes, and guiding scientific surveys. Here we present our current precision estimates of PARAS based on observations of bright RV standard stars, and describe the evolution of the data reduction and RV analysis pipeline as instrument characterization progresses and we gather longer baselines of data. Secondly, we discuss how our experience with PARAS is a critical component in the development of future cutting edge instruments like (1) the Habitable Zone Planet Finder (HPF), a near-infrared spectrograph optimized to look for planets around M dwarfs, scheduled to be commissioned on the Hobby Eberly Telescope in 2017, and (2) the NEID optical spectrograph, designed in response to the NN-EXPLORE call for an extreme precision Doppler spectrometer (EPDS) for the WIYN telescope. In anticipation of instruments like TESS and GAIA, the ground-based RV support system is being reinforced. We emphasize that instruments like PARAS will play an intrinsic role in providing both complementary follow-up and battlefront experience for these next generation of precision velocimeters.

  3. Radial velocities of giant stars: an investigation of line profile variations

    Energy Technology Data Exchange (ETDEWEB)

    Hekker, S; Snellen, I A G [Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden (Netherlands); Aerts, C [Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven (Belgium); Quirrenbach, A; Reffert, S [ZAH, Landessternwarte Heidelberg, Koenigstuhl 12, D-69117 Heidelberg (Germany); Mitchell, D S [California Polytechnic State University, San Luis Obispo, CA 93407 (United States)], E-mail: saskia@strw.leidenuniv.nl

    2008-10-15

    Since 1999, a radial velocity survey of 179 red giant stars is ongoing at Lick Observatory with a one month cadence. At present{approx}20-100 measurements have been collected per star with an accuracy of 5 to 8 ms{sup -1}. Of the stars monitored, 145 (80%) show radial velocity (RV) variations at a level >20 ms{sup -1}, of which 43 exhibit significant periodicities. Here, we investigate the mechanism causing the observed radial velocity variations. Firstly, we search for a correlation between the radial velocity amplitude and an intrinsic parameter of the star, in this case surface gravity (logg). Secondly, we investigate line profile variations and compare these with theoretical predictions.

  4. VizieR Online Data Catalog: WASP-80 photometric and radial velocity data (Triaud+, 2013)

    Science.gov (United States)

    Triaud, A. H. M. J.; Anderson, D. R.; Collier, Cameron A.; Doyle, A. P.; Fumel, A.; Gillon, M.; Hellier, C.; Jehin, E.; Lendl, M.; Lovis, C.; Maxted, P. F. L.; Pepe, F.; Pollacco, D.; Queloz, D.; Segransan, D.; Smalley, B.; Smith, A. M. S.; Udry, S.; West, R. G.; Wheatley, P. J.

    2013-01-01

    The data is composed of one WASP photometric timeseries in a band similar to V+R, of two TRAPPIST photometric timeseries in the z band, and of one series from the EulerCam, in the Gunn r' filter. There is also one set of CORALIE radial velocities and one set of HARPS radial velocities. They give evidence of a planet orbiting and transiting WASP-80. (6 data files).

  5. Characterization of the radial velocity signal induced by rotation in late-type dwarfs

    Science.gov (United States)

    Suárez Mascareño, A.; Rebolo, R.; González Hernández, J. I.; Esposito, M.

    2017-07-01

    We investigate the activity-induced signals related to rotation and magnetic cycles in late-type stars (FGKM) and analyse the Ca II H&K, the H α and the radial velocity time series of 55 stars using the spectra from the HARPS public data base and the light curves provided by the All Sky Automated Survey. We search for short-term and long-term periodic signals in the time series of activity indicators as well as in the photometric light curves. Radial velocity data sets are then analysed to determine the presence of activity-induced signals. We measure a radial velocity signal induced by rotational modulation of stellar surface features in 37 stars, from late-F-type to mid-M-type stars. We report an empirical relationship, with some degree of spectral type dependency, between the mean level of chromospheric emission measured by the log _{10}(R^' }_{HK}) and the measured radial velocity semi-amplitude. We also report a relationship between the semi-amplitude of the chromospheric measured signal and the semi-amplitude of the radial velocity-induced signal, which strongly depends on the spectral type. We find that for a given strength of chromospheric activity (i.e. a given rotation period), M-type stars tend to induce larger rotation-related radial velocity signals than G- and K-type stars.

  6. Comparison of the Pulkovo Compilation of Radial Velocities with the RAVE DR1 Catalogue

    CERN Document Server

    Gontcharov, George

    2016-01-01

    The Data Release 1 of the Radial-Velocity Experiment (RAVE DR1, 24 748 stars) is compared with the May 15, 2006 version of the Pulkovo Compilation of Radial Velocities (PCRV, 35 495 stars). RAVE DR1 includes mostly $9^m-13^m$ stars, while the PCRV contains brighter stars. Analysis of the "RAVE minus PCRV" radial-velocity differences for 14 common stars has revealed no systematic dependences on any factors, except the effect due to the RAVE radial-velocity zero-point offset known from the RAVE observations. This effect shows up for ten of these stars observed on a single night as a sine wave with an amplitude of 1.5 km s$^{-1}$ in the dependence of the radial-velocity difference on the ordinal number of the optical fiber used and, accordingly, on the star position angle in the field of view of the RAVE instrument. The detection of this dependence confirms a high radial-velocity accuracy in both catalogs: on average, better than 1 km s$^{-1}$ for stars brighter than $10^m$ (for the RAVE, after applying a correc...

  7. Daytime, low latitude, vertical ExB drift velocities, inferred from ground-based magnetometer observations in the Peruvian, Philippine and Indian longitude sectors under quiet and disturbed conditions

    CERN Document Server

    Anderson, D; Chau, J; Yumoto, K; Bhattacharya, A; Alex, S

    2006-01-01

    Daytime, low latitude, vertical ExB drift velocities, inferred from ground-based magnetometer observations in the Peruvian, Philippine and Indian longitude sectors under quiet and disturbed conditions

  8. Radial velocity measurements of the pulsating zirconium star: LS IV -14 116

    CERN Document Server

    Jeffery, C Simon; Neelamkodan, Naslim; Kerzendorf, Wolfgang

    2014-01-01

    The helium-rich hot subdwarf LS IV -14 116 shows remarkably high surface abundances of zirconium, yttrium, strontium, and germanium, indicative of strong chemical stratification in the photosphere. It also shows photometric behaviour indicative of non-radial g-mode pulsations, despite having surface properties inconsistent with any known pulsational instability zone. We have conducted a search for radial velocity variability. This has demonstrated that at least one photometric period is observable in several absorption lines as a radial velocity variation with a semi-amplitude in excess of 5 km s$^{-1}$. A correlation between line strength and pulsation amplitude provides evidence that the photosphere pulsates differentially. The ratio of light to velocity amplitude is too small to permit the largest amplitude oscillation to be radial.

  9. Analysis of Terminal Velocity and VHF Backscatter of Precipitation Particles Using Chung-Li VHF Radar Combined with Ground-Based Disdrometer

    Directory of Open Access Journals (Sweden)

    Ching-Lun Su and Yen-Hsyang Chu

    2007-01-01

    Full Text Available The backscatter from precipitation particles observed by the vertically pointed antenna beam of the Chung-Li VHF radar and the drop size distributions measured by a ground-based disdrometer co-located at the radar site are analyzed and studied in this article. We find that the disdrometermeasured drop size distribution can be well approximated to a Gamma distribution. On the basis of this property and a power law approximation to the fallspeed-diameter relation VD = ADB, we derive the theoretical relation between terminal velocity VD and range-corrected VHF backscatter P of the precipitation particles. We find that the VD - P relation follows a power law in the form of VD = _ where _ _ both the functions of the precipitation parameters. Chu et al. (1999 first found that the relation between _ _ be empirically approximated to an exponential form of _ _ where _ a function of B and _ a factor associated with precipitation. In this article, under the assumptions of the Gamma distribution of the drop size distribution and the power-law relation between VD and D, we theoretically show that the analytical relation between _ _ follows an exponential form of _ _ where _ a function of the drop size distribution. The experimental results obtained by the Chung-Li VHF radar combined with the ground-based disdrometer measurements validate the exponential approximation to the _ _ The uses of the _ _ for the investigations of the rainfall rate and properties of drop size distribution are presented and discussed.

  10. Transit and radial velocity survey efficiency comparison for a habitable zone Earth

    Energy Technology Data Exchange (ETDEWEB)

    Burke, Christopher J. [SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035 (United States); McCullough, P. R., E-mail: christopher.j.burke@nasa.gov [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2014-09-01

    Transit and radial velocity searches are two techniques for identifying nearby extrasolar planets to Earth that transit bright stars. Identifying a robust sample of these exoplanets around bright stars for detailed atmospheric characterization is a major observational undertaking. In this study we describe a framework that answers the question of whether a transit or radial velocity survey is more efficient at finding transiting exoplanets given the same amount of observing time. Within the framework we show that a transit survey's window function can be approximated using the hypergeometric probability distribution. We estimate the observing time required for a transit survey to find a transiting Earth-sized exoplanet in the habitable zone (HZ) with an emphasis on late-type stars. We also estimate the radial velocity precision necessary to detect the equivalent HZ Earth-mass exoplanet that also transits when using an equal amount of observing time as the transit survey. We find that a radial velocity survey with σ{sub rv} ∼ 0.6 m s{sup –1} precision has comparable efficiency in terms of observing time to a transit survey with the requisite photometric precision σ{sub phot} ∼ 300 ppm to find a transiting Earth-sized exoplanet in the HZ of late M dwarfs. For super-Earths, a σ{sub rv} ∼ 2.0 m s{sup –1} precision radial velocity survey has comparable efficiency to a transit survey with σ{sub phot} ∼ 2300 ppm.

  11. Evidence for thermospheric gravity waves in the southern polar cap from ground-based vertical velocity and photometric observations

    Directory of Open Access Journals (Sweden)

    J. L. Innis

    Full Text Available Zenith-directed Fabry-Perot Spectrometer (FPS and 3-Field Photometer (3FP observations of the λ630 nm emission (~240 km altitude were obtained at Davis station, Antarctica, during the austral winter of 1999. Eleven nights of suitable data were searched for significant periodicities common to vertical winds from the FPS and photo-metric variations from the 3FP. Three wave-like events were found, each of around one or more hours in duration, with periods around 15 minutes, vertical velocity amplitudes near 60 ms–1 , horizontal phase velocities around 300 ms–1 , and horizontal wavelengths from 240 to 400 km. These characteristics appear consistent with polar cap gravity waves seen by other workers, and we conclude this is a likely interpretation of our data. Assuming a source height near 125 km altitude, we determine the approximate source location by calculating back along the wave trajectory using the gravity wave property relating angle of ascent and frequency. The wave sources appear to be in the vicinity of the poleward border of the auroral oval, at magnetic local times up to 5 hours before local magnetic midnight.

    Key words. Meteorology and atmospheric dynamics (thermospheric dynamics; waves and tides

  12. VizieR Online Data Catalog: Radial velocities of K-M dwarfs (Sperauskas+, 2016)

    Science.gov (United States)

    Sperauskas, J.; Bartasiute, S.; Boyle, R. P.; Deveikis, V.; Raudeliunas, S.; Upgren, A. R.

    2016-09-01

    We analyzed nearly 3300 measurements of radial velocities for 1049 K-M dwarfs, that we obtained during the past decade with a CORAVEL-type instrument, with a primary emphasis on detecting and eliminating from kinematic calculations the spectroscopic binaries and binary candidates. We present the catalog of our observations of radial velocities for 959 stars which are not suspected of velocity variability. Of these, 776 stars are from the MCC sample and 173 stars are K-M dwarfs from the CNS4. The catalog consists of two parts: Table 2 lists the mean radial velocities, and Table 2a contains individual measurements. Our radial velocities agree with the best published standard stars to within 0.7km/s in precision. Combining these and supplementary radial-velocity data with Hipparcos/Tycho-2 astrometry (Table 4 summarizes input observational data) we calculated the space velocity components and parameters of the galactic orbits in a three-component model potential by Johnston K.V. et al. (1995ApJ...451..598J) for a total of 1088 K-M dwarfs (Table 5), that we use for kinematical analysis and for the identification of possible candidate members of nearby stellar kinematic groups. We identified 146 stars as possible candidate members of the classical moving groups and known or suspected subgroups (Table 7). We show that the distributions of space-velocity components, orbital eccentricities, and maximum distances from the Galactic plane for nearby K-M dwarfs are consistent with the presence of young, intermediate-age and old populations of the thin disk and a small fraction (3%) of stars with the thick disk kinematics. (7 data files).

  13. VizieR Online Data Catalog: Radial velocities in Omega Cen (NGC5139) (Reijns+, 2006)

    Science.gov (United States)

    Reijns, R. A.; Seitzer, P.; Arnold, R.; Freeman, K. C.; Ingerson, T.; van den Bosch, R. C. E.; van de Ven, G.; de Zeeuw, P. T.

    2005-11-01

    List of 1966 radial velocity measurements of stars in globular cluster Omega Centauri (NGC 5139) taken with the ARGUS multi-object spectrometer at the CTIO 4m Blanco telescope. All the stars have a B magnitude brighter than 16.5. The median error is less than 2km/s. The stars are numbered using their LID (Leiden Identification Number) from van Leeuwen et.al. (2000, Cat. ). In a companion paper by van de Ven et al. (2006A&A...445..513V), we correct these radial velocities for the perspective rotation caused by the space motion of the cluster. Additionaly 339 stars where measured. These consist of (i) 87 stars with B-Vii) 252 stars not in the van Leeuwen et al. catalog. We suspect that that many of these stars have an erroneous value for their radial velocity. (2 data files).

  14. An Inexpensive Field-Widened Monolithic Michelson Interferometer for Precision Radial Velocity Measurements

    CERN Document Server

    Mahadevan, Suvrath; Fleming, Scott W; Wan, Xiaoke; DeWitt, Curtis; van Eyken, Julian C; McDavitt, Dan

    2008-01-01

    We have constructed a thermally compensated field-widened monolithic Michelson interferometer that can be used with a medium-resolution spectrograph to measure precise Doppler radial velocities of stars. Our prototype monolithic fixed-delay interferometer is constructed with off-the-shelf components and assembled using a hydrolysis bonding technique. We installed and tested this interferometer in the Exoplanet Tracker (ET) instrument at the Kitt Peak 2.1m telescope, an instrument built to demonstrate the principles of dispersed fixed delay interferometry. An iodine cell allows the interferometer drift to be accurately calibrated, relaxing the stability requirements on the interferometer itself. When using our monolithic interferometer, the ET instrument has no moving parts (except the iodine cell), greatly simplifying its operation. We demonstrate differential radial velocity precision of a few m s$^{-1}$ on well known radial velocity standards and planet bearing stars when using this interferometer. Such mon...

  15. XO-2b: a Prograde Planet with a Negligible Eccentricity, and an Additional Radial Velocity Variation

    CERN Document Server

    Narita, Norio; Sato, Bun'ei; Harakawa, Hiroki; Fukui, Akihiko; Aoki, Wako; Tamura, Motohide

    2011-01-01

    We present precise radial velocities of XO-2 taken with the Subaru HDS, covering two transits of XO-2b with an interval of nearly two years. The data suggest that the orbital eccentricity of XO-2b is consistent with zero within 2$\\sigma$ ($e=0.045\\pm0.024$) and the orbit of XO-2b is prograde (the sky-projected spin-orbit alignment angle $\\lambda=10^{\\circ}\\pm72^{\\circ}$). The poor constraint of $\\lambda$ is due to a small impact parameter (the orbital inclination of XO-2b is almost 90$^{\\circ}$). The data also provide an improved estimate of the mass of XO-2b as $0.62\\pm0.02$ $M_{\\rm Jup}$. We also find a long-term radial velocity variation in this system. Further radial velocity measurements are necessary to specify the cause of this additional variation.

  16. Uncovering the planets and stellar activity of CoRoT-7 using only radial velocities

    CERN Document Server

    Faria, J P; Brewer, B J; Figueira, P; Oshagh, M; Santerne, A; Santos, N C

    2016-01-01

    Stellar activity can induce signals in the radial velocities of stars, complicating the detection of orbiting low-mass planets. We present a method to determine the number of planetary signals present in radial-velocity datasets of active stars, using only radial-velocity observations. Instead of considering separate fits with different number of planets, we use a birth-death Markov chain Monte Carlo algorithm to infer the posterior distribution for the number of planets in a single run. In a natural way, the marginal distributions for the orbital parameters of all planets are also inferred. This method is applied to HARPS data of CoRoT-7. We confidently recover both CoRoT-7b and CoRoT-7c although the data show evidence for additional signals.

  17. Open Cluster Radial Velocity determination from observations at Observatório Pico Dos Dias

    Science.gov (United States)

    Faria, M. A. F.; Monteiro, H.; Dias, W. S.; Lépine, J. R. D.

    2014-10-01

    In studies of the dynamics of the Galactic disk, such as the determination of the speed of the spiral pattern and the permanence of stars in the spiral arms, it is crucial to know orbits obtained from proper motions, radial velocities and the potential of the Galaxy. Aiming to improve the statistics of our catalog of open clusters, maintained by our research group, we determined the radial velocity of stars belonging to a group of open clusters using spectra with a resolution of 4000, obtained at the Pico dos Dias Observatory (LNA) with the 1.60 m telescope and the Coudé spectrograph. We observed the open cluster's member stars and calculated their radial speeds using standard techniques. The stars were selected from our own database based on relevant information concerning the clusters, obtained by statistical analysis of their proper motions and/or their position in the HR's diagram. In this work, we present the detailed analysis of the data reduction and radial velocity determination using synthetic spectra from different libraries. Finally we present the open cluster's radial (and spacial) velocities.

  18. A Radial Velocity Study of the Intermediate Polar EX Hydrae

    CERN Document Server

    Echevarría, J; Michel, R; Santisteban, J V Hernández

    2016-01-01

    A study on the intermediate polar EX Hya is presented, based on simultaneous photometry and high dispersion spectroscopic observations, during four consecutive nights. The strong photometric modulation related to with the 67-min spin period of the primary star is clearly present, as well as the narrow eclipses associated to the orbital modulation. Since our eclipse timings have been obtained almost 91,000 cycles since the last reported observations, we present new linear ephemeris, although we cannot rule out a sinusoidal variation suggested by previous authors. The system mainly shows double-peaked H$\\alpha$, H$\\beta$ and HeI $\\lambda$5876 \\AA emission lines. From the profile of the H$\\alpha$ line, we find two components; one with a steep rise and velocities not larger than $\\sim$1000 km s$^{-1}$ and another broader component extending up to $\\sim$2000 km s$^{-1}$, which we interpret as coming mainly from the inner disc. A strong and variable hotspot is found and a stream-like structure is seen at times. We ...

  19. Axial and radial velocities in the creeping flow in a pipe

    Directory of Open Access Journals (Sweden)

    Zuykov Andrey L'vovich

    2014-05-01

    Full Text Available The article is devoted to analytical study of transformation fields of axial and radial velocities in uneven steady creeping flow of a Newtonian fluid in the initial portion of the cylindrical channel. It is shown that the velocity field of the flow is two-dimensional and determined by the stream function. The article is a continuation of a series of papers, where normalized analytic functions of radial axial distributions in uneven steady creeping flow in a cylindrical tube with azimuthal vorticity and stream function were obtained. There is Poiseuille profile for the axial velocity in the uniform motion of a fluid at an infinite distance from the entrance of the pipe (at x = ∞, here taken equal to zero radial velocity. There is uniform distribution of the axial velocity in the cross section at the tube inlet at x = 0, at which the axial velocity is constant along the current radius. Due to the axial symmetry of the flow on the axis of the pipe (at r = 0, the radial velocities and the partial derivative of the axial velocity along the radius, corresponding to the condition of the soft function extremum, are equal to zero. The authors stated vanishing of the velocity of the fluid on the walls of the pipe (at r = R , where R - radius of the tube due to its viscous sticking and tightness of the walls. The condition of conservation of volume flow along the tube was also accepted. All the solutions are obtained in the form of the Fourier - Bessel. It is shown that the hydraulic losses at uniform creeping flow of a Newtonian fluid correspond to Poiseuille - Hagen formula.

  20. An Inexpensive Field-Widened Monolithic Michelson Interferometer for Precision Radial Velocity Measurements

    Science.gov (United States)

    Mahadevan, Suvrath; Ge, Jian; Fleming, Scott W.; Wan, Xiaoke; DeWitt, Curtis; van Eyken, Julian C.; McDavitt, Dan

    2008-09-01

    We have constructed a thermally compensated field-widened monolithic Michelson interferometer that can be used with a medium-resolution spectrograph to measure precise Doppler radial velocities of stars. Our prototype monolithic fixed-delay interferometer is constructed with off-the-shelf components and assembled using a hydrolysis bonding technique. We installed and tested this interferometer in the Exoplanet Tracker (ET) instrument at the Kitt Peak 2.1 m telescope, an instrument built to demonstrate the principles of dispersed fixed-delay interferometry. An iodine cell allows the interferometer drift to be accurately calibrated, relaxing the stability requirements on the interferometer itself. When using our monolithic interferometer, the ET instrument has no moving parts (except the iodine cell), greatly simplifying its operation. We demonstrate differential radial velocity precision of a few m s-1 on well known radial velocity standards and planet bearing stars when using this interferometer. Such monolithic interferometers will make it possible to build relatively inexpensive instruments that are easy to operate and capable of precision radial velocity measurements. A larger multiobject version of the Exoplanet Tracker will be used to conduct a large scale survey for planetary systems as part of the Sloan Digital Sky Survey III (SDSS III). Variants of the techniques and principles discussed in this paper can be directly applied to build large monolithic interferometers for such applications, enabling the construction of instruments capable of efficiently observing many stars simultaneously at high velocity precision.

  1. The Joker: A custom Monte Carlo sampler for binary-star and exoplanet radial velocity data

    CERN Document Server

    Price-Whelan, Adrian M; Foreman-Mackey, Daniel; Rix, Hans-Walter

    2016-01-01

    Given sparse or low-quality radial-velocity measurements of a star, there are often many qualitatively different stellar or exoplanet companion orbit models that are consistent with the data. The consequent multimodality of the likelihood function leads to extremely challenging search, optimization, and MCMC posterior sampling over the orbital parameters. Here we create a custom-built Monte Carlo sampler that can produce a posterior sampling for orbital parameters given sparse or noisy radial-velocity measurements, even when the likelihood function is poorly behaved. The six standard orbital parameters for a binary system can be split into four non-linear parameters (period, eccentricity, argument of pericenter, phase) and two linear parameters (velocity amplitude, barycenter velocity). We capitalize on this by building a sampling method in which we densely sample the prior pdf in the non-linear parameters, and perform rejection sampling using a likelihood function marginalized over the linear parameters. Wit...

  2. The OCCASO survey: Presentation and radial velocities of twelve Milky Way Open Clusters

    CERN Document Server

    Casamiquela, L; Jordi, C; Balaguer-Núñez, L; Pancino, E; Hidalgo, S L; Martínez-Vázquez, C E; Murabito, S; del Pino, A; Aparicio, A; Blanco-Cuaresma, S; Gallart, C

    2016-01-01

    Open clusters (OCs) are crucial for studying the formation and evolution of the Galactic disc. However, the lack of a large number of OCs analyzed homogeneously hampers the investigations about chemical patterns and the existence of Galactocentric radial and vertical gradients, or an age-metallicity relation. To overcome this, we have designed the Open Cluster Chemical Abundances from Spanish Observatories survey (OCCASO). We aim to provide homogeneous radial velocities, physical parameters and individual chemical abundances of six or more Red Clump stars for a sample of 25 old and intermediate-age OCs visible from the Northern hemisphere. To do so, we use high resolution spectroscopic facilities (R> 62,000) available at Spanish observatories. We present the motivation, design and current status of the survey, together with the first data release of radial velocities for 77 stars in 12 OCs, which represents about 50% of the survey. We include clusters never studied with high-resolution spectroscopy before (NG...

  3. Impact of micro-telluric lines on precise radial velocities and its correction

    CERN Document Server

    Cunha, D; Figueira, P; Santerne, A; Bertaux, J L; Lovis, C

    2014-01-01

    Context: In the near future, new instruments such as ESPRESSO will arrive, allowing us to reach a precision in radial-velocity measurements on the order of 10 cm/s. At this level of precision, several noise sources that until now have been outweighed by photon noise will start to contribute significantly to the error budget. The telluric lines that are not neglected by the masks for the radial velocity computation, here called micro-telluric lines, are one such noise source. Aims: In this work we investigate the impact of micro-telluric lines in the radial velocities calculations. We also investigate how to correct the effect of these atmospheric lines on radial velocities. Methods: The work presented here follows two parallel lines. First, we calculated the impact of the micro-telluric lines by multiplying a synthetic solar-like stellar spectrum by synthetic atmospheric spectra and evaluated the effect created by the presence of the telluric lines. Then, we divided HARPS spectra by synthetic atmospheric spec...

  4. Radial variation of refractive index, plasma frequency and phase velocity in laser induced air plasma

    CSIR Research Space (South Africa)

    Mathuthu, M

    2006-12-01

    Full Text Available induced air plasma to study the spatial variation of plasma parameters in the axial direction of the laser beam. In this paper, the authors report investigation on the radial variation of the refractive index, plasma frequency, and phase velocity of a...

  5. Precise Radial Velocity Measurements for Kepler Giants Hosting Planetary Candidates: Kepler-91 and KOI-1894

    CERN Document Server

    Sato, Bun'ei; Omiya, Masashi; Harakawa, Hiroki; Kobayashi, Atsushi; Hasegawa, Ryo; Takarada, Takuya; Kawauchi, Kiyoe; Masuda, Kento

    2015-01-01

    We present results of radial-velocity follow-up observations for the two Kepler evolved stars Kepler-91 (KOI-2133) and KOI-1894, which had been announced as candidates to host transiting giant planets, with the Subaru 8.2m telescope and the High Dispersion Spectrograph (HDS). By global modeling of the high-precision radial-velocity data taken with Subaru/HDS and photometric ones taken by Kepler mission taking account of orbital brightness modulations (ellipsoidal variations, reflected/emitted light, etc.) of the host stars, we independently confirmed that Kepler-91 hosts a transiting planet with a mass of 0.66 M_Jup (Kepler-91b), and newly detected an offset of ~20 m s$^{-1}$ between the radial velocities taken at ~1-yr interval, suggesting the existence of additional companion in the system. As for KOI-1894, we detected possible phased variations in the radial velocities and light curves with 2--3 sigma confidence level which could be explained as a reflex motion and ellipsoidal variation of the star caused ...

  6. Precise Radial Velocity Measurements for Kepler Giants Hosting Planetary Candidates: Kepler-91 and KOI-1894

    Science.gov (United States)

    Sato, Bun'ei; Hirano, Teruyuki; Omiya, Masashi; Harakawa, Hiroki; Kobayashi, Atsushi; Hasegawa, Ryo; Takarada, Takuya; Kawauchi, Kiyoe; Masuda, Kento

    2015-03-01

    We present results of radial-velocity follow-up observations for the two Kepler evolved stars Kepler-91 (KOI-2133) and KOI-1894, which had been announced as candidates to host transiting giant planets, with the Subaru 8.2 m telescope and the High Dispersion Spectrograph (HDS). By global modeling of the high-precision radial-velocity data taken with Subaru/HDS and photometric data taken by the Kepler mission accounting for orbital brightness modulations (ellipsoidal variations, reflected/emitted light, etc.) of the host stars, we independently confirmed that Kepler-91 hosts a transiting planet with a mass of 0.66 {{M}Jup}(Kepler-91b), and newly detected an offset of ˜20 m s-1 between the radial velocities taken at ˜1 yr interval, suggesting the existence of an additional companion in the system. As for KOI-1894, we detected possible phased variations in the radial velocities and light curves with 2-3σ confidence level, which could be explained as a reflex motion and ellipsoidal variation of the star caused by a transiting sub-Saturn-mass (˜0.18 {{M}Jup}) planet.

  7. High-Resolution Radial Velocity Mapping of Optical Filaments in Evolved Supernova Remnants

    Science.gov (United States)

    Greidanus, H.; Strom, R. G.

    The authors report on observations of the kinematical structure of optical filaments in evolved supernova remnants, using an imaging Fabry-Perot interferometer. The radial velocity characteristics as seen in [O III] λ5007 emission in one area in the Cygnus Loop are described, where four kinematically different components contributing to the emission can be recognized.

  8. VizieR Online Data Catalog: Coralie radial velocities for l Car (Anderson+, 2016)

    Science.gov (United States)

    Anderson, R. I.; Merand, A.; Kervella, P.; Breitfelder, J.; Lebouquin, J.-B.; Eyer, L.; Gallenne, A.; Palaversa, L.; Semaan, T.; Saesen, S.; Mowlavi, N.

    2016-07-01

    360 radial velocity measurements (RVs) of {ell} Carinae are made publicly available. These RVs were measured using optical spectra observed with the Coralie spectrograph mounted to the 1.2m Swiss Euler telescope situated at La Silla Observatory, Chile. (1 data file).

  9. VizieR Online Data Catalog: Radial velocity monitoring of 5 FGK stars (Endl+, 2016)

    Science.gov (United States)

    Endl, M.; Brugamyer, E. J.; Cochran, W. D.; MacQueen, P. J.; Robertson, P.; Meschiari, S.; Ramirez, I.; Shetrone, M.; Gullikson, K.; Johnson, M. C.; Wittenmyer, R.; Horner, J.; Ciardi, D. R.; Horch, E.; Simon, A. E.; Howell, S. B.; Everett, M.; Caldwell, C.; Castanheira, B. G.

    2016-04-01

    Our radial velocity (RV) measurements were obtained using the 2.7m Harlan J. Smith Telescope (HJST; R=60000, 3750-10200Å). For HD 95872, we also obtained 10 precise RV measurements using the 10m Keck I and its HIRES spectrograph (R=50000). (6 data files).

  10. Long-term radial-velocity variations of the Sun as a star: the HARPS view

    CERN Document Server

    Lanza, A F; Monaco, L; Haywood, R D

    2016-01-01

    Stellar radial velocities play a fundamental role in the discovery of extrasolar planets and the measurement of their physical parameters as well as in the study of stellar physical properties. We investigate the impact of the solar activity on the radial velocity of the Sun using the HARPS spectrograph to obtain measurements that can be directly compared with those acquired in the extrasolar planet search programs. We use the Moon, the Galilean satellites, and several asteroids as reflectors to measure the radial velocity of the Sun as a star and correlate it with disc-integrated chromospheric and magnetic indexes of solar activity that are similar to stellar activity indexes. We discuss in detail the systematic effects that affect our measurements and the methods to account for them. We find that the radial velocity of the Sun as a star is positively correlated with the level of its chromospheric activity at about 95 percent significance level. The amplitude of the long-term variation measured in the 2006-2...

  11. Radial velocity variations in red giant stars : pulsations, spots and planets

    NARCIS (Netherlands)

    Hekker, Saskia

    2007-01-01

    Radial velocity variations in K giants are observed on long (order hundreds of days) and short (order hours) time scales. Short term variations are most likely caused by solar-like oscillations, stochastically excited in the turbulent atmosphere of the stars. Long term variations can be caused by e

  12. VizieR Online Data Catalog: WASP-117b photometry and radial velocities (Lendl+, 2014)

    Science.gov (United States)

    Lendl, M.; Triaud, A. H. M. J.; Anderson, D. R.; Collier-Cameron, A.; Delrez, L.; Doyle, A. P.; Gillon, M.; Hellier, C.; Jehin, E.; Maxted, P. F. L.; Neveu-Vanmalle, M.; Pepe, F.; Pollacco, D.; Queloz, D.; Segransan, D.; Smalley, B.; Smith, A. M. S.; Udry, S.; Van Grootel, V.; West, R.

    2014-08-01

    We present photometric time-series obtained with EulerCam and TRAPPIST during one and four transits of WASP-117, respectively. We also present radial velocity data from CORALIE and HARPS used to characterize the planetary orbit. (4 data files).

  13. VizieR Online Data Catalog: Radial velocity curves of alpha Lib A (Fuhrmann+, 2014)

    Science.gov (United States)

    Fuhrmann, K.; Chini, R.; Barr, A.; Buda, L.-S.; Kaderhandt, L.; Pozo, F.; Ramolla, M.

    2015-03-01

    Our observations of α Lib A consist of optical spectra secured with the BESO high-resolution echelle spectrograph of the Universitetssternwarte Bochum near Cerro Armazones in Chile. The full record of the total of 55 radial velocities is given in Table 1. Intense Doppler-monitoring of alpha Lib A started in 2012 August and was continued until 2013 September. (1 data file).

  14. Precise Infrared Radial Velocities from Keck/NIRSPEC and the Search for Young Planets

    CERN Document Server

    Bailey, John I; Blake, Cullen H; Charbonneau, Dave; Barman, Travis S; Tanner, Angelle M; Torres, Guillermo

    2012-01-01

    We present a high-precision infrared radial velocity study of late-type stars using spectra obtained with NIRSPEC at the W. M. Keck Observatory. Radial velocity precisions of 50 m/s are achieved for old field mid-M dwarfs using telluric features for precise wavelength calibration. Using this technique, 20 young stars in the {\\beta} Pic (age ~12 Myr) and TW Hya (age ~8 Myr) Associations were monitored over several years to search for low mass companions; we also included the chromospherically active field star GJ 873 (EV Lac) in this survey. Based on comparisons with previous optical observations of these young active stars, radial velocity measurements at infrared wavelengths mitigate the radial velocity noise caused by star spots by a factor of ~3. Nevertheless, star spot noise is still the dominant source of measurement error for young stars at 2.3 {\\mu}m, and limits the precision to ~77 m/s for the slowest rotating stars (v sin i 12 km/s). The observations reveal both GJ 3305 and TWA 23 to be single-lined...

  15. High resolution spectroscopy of bright subdwarf B stars - I. Radial velocity variables

    CERN Document Server

    Edelmann, H; Altmann, M; Karl, C; Lisker, T

    2005-01-01

    Radial velocity curves for 15 bright subdwarf B binary systems have been measured using high precision radial velocity measurements from high S/N optical high-resolution spectra. In addition, two bright sdB stars are discovered to be radial velocity variable but the period could not yet be determined. The companions for all systems are unseen. The periods range from about 0.18 days up to more than ten days. The radial velocity semi amplitudes are found to lie between 15 and 130 km/s. Using the mass functions, the masses of the unseen companions have been constrained to lower limits of 0.03 up to 0.55 M_sun, and most probable values of 0.03 up to 0.81 M_sun. The invisible companions for three of our program stars are undoubtedly white dwarfs. In the other cases they could be either white dwarfs or main sequence stars. For two stars the secondaries could possibly be brown dwarfs. As expected, the orbits are circular for most of the systems. However, for one third of the program stars we find slightly eccentric ...

  16. Modeling the Radial Velocity Curve of the Water Vapor Maser in VX UMa

    Science.gov (United States)

    Salter, D. M.; Benson, P. J.; Strelnitski, V. S.

    1999-12-01

    VX UMa is a unique Mira-type star that demonstrates a triple-peaked spectrum of its 1.35-cm H2O maser emission. We used the high-precision curves of radial velocities of the spectral peaks, obtained by Benson & Little-Marenin from 1988 to 1992, as probes of the kinematics of the masing region. The pronounced periodicity of the radial velocity of the central component, with a period equal to the pulsational period of the optical variations, suggests the involvement of pulsations in the observed excursions of radial velocity. However, the radial velocity of the central spectral component produced by a symmetrical, pulsating spherical layer should be constantly zero. Rotation seems to be the most obvious mechanism to impart a small non-zero component to the central feature. We assume that the bulk of maser radiation originates in the equatorial "belt" around the star and approximate this region as a two-dimensional, rotating and pulsating ring. We found that any combination of rotation and pulsation produces a quadruple peaked, not a triple peaked spectrum. Therefore, some asymmetry in the disk or unequal absorption of the two central peaks by ionized gas (e.g. in the shock responsible for the maser emission) is needed. We demonstrate that one of the central peaks can then undergo periodic changes of its radial velocity with the period of pulsation, as observed. A VLBA experiment that may verify our model is under way. This project was supported by the NSF/REU grant AST-9820555.

  17. Radial Velocities of Dwarf Spheroidal Galaxies in the M81 Group

    OpenAIRE

    Sharina, M. E.; Karachentsev, I. D.; Burenkov, A. N.

    2001-01-01

    Long-slit observations of 4 dwarf spheroidal galaxies in the M81 group are presented. We have obtained a heliocentric velocity of globular cluster candidate located near the center of DDO78 to be +55 +- 10 km/s by cross-correlation with template stars. We estimated a heliocentric radial velocity of -116 +- 21 km/s for an HII region seen in the K 61. A red diffuse object near the K64 center is found to be a remote galaxy with a heliocentric velocity of +46530 km/s.

  18. Comparison of CME radial velocities from a flux rope model and an ice cream cone model

    Science.gov (United States)

    Kim, T.; Moon, Y.; Na, H.

    2011-12-01

    Coronal Mass Ejections (CMEs) on the Sun are the largest energy release process in the solar system and act as the primary driver of geomagnetic storms and other space weather phenomena on the Earth. So it is very important to infer their directions, velocities and three-dimensional structures. In this study, we choose two different models to infer radial velocities of halo CMEs since 2008 : (1) an ice cream cone model by Xue et al (2005) using SOHO/LASCO data, (2) a flux rope model by Thernisien et al. (2009) using the STEREO/SECCHI data. In addition, we use another flux rope model in which the separation angle of flux rope is zero, which is morphologically similar to the ice cream cone model. The comparison shows that the CME radial velocities from among each model have very good correlations (R>0.9). We will extending this comparison to other partial CMEs observed by STEREO and SOHO.

  19. RADIAL VELOCITIES FROM VLT-KMOS SPECTRA OF GIANT STARS IN THE GLOBULAR CLUSTER NGC 6388

    Energy Technology Data Exchange (ETDEWEB)

    Lapenna, E.; Mucciarelli, A.; Lanzoni, B.; Ferraro, F. R.; Dalessandro, E. [Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy); Origlia, L. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani, 1, I-40127 Bologna (Italy); Valenti, E. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München (Germany); Cirasuolo, M. [Institute for Astronomy, University of Edinburgh and STFC, UK Astronomy Technology Center Royal Observatory, Blackford Hill, EH9 3HJ, Edinburgh (United Kingdom)

    2015-01-01

    We present new radial velocity measurements for 82 stars, members of the Galactic globular cluster (GC) NGC 6388, obtained from ESO-VLT K-band Multi Object Spectrograph (KMOS) spectra acquired during the instrument Science Verification. The accuracy of the wavelength calibration is discussed and a number of tests of the KMOS response are presented. The cluster systemic velocity obtained (81.3 ± 1.5 km s{sup –1}) is in very good agreement with previous determinations. While a hint of ordered rotation is found between 9'' and 20'' from the cluster center, where the distribution of radial velocities is clearly bimodal, more data are needed before drawing any firm conclusions. The acquired sample of radial velocities has also been used to determine the cluster velocity dispersion (VD) profile between ∼9'' and 70'', supplementing previous measurements at r < 2'' and r > 60'' obtained with ESO-SINFONI and ESO-FLAMES spectroscopy, respectively. The new portion of the VD profile nicely matches the previous ones, better defining the knee of the distribution. The present work clearly shows the effectiveness of a deployable integral field unit in measuring the radial velocities of individual stars for determining the VD profile of Galactic GCs. It represents the pilot project for an ongoing large program with KMOS and FLAMES at the ESO-VLT, aimed at determining the next generation of VD and rotation profiles for a representative sample of GCs.

  20. Finding binaries from phase modulation of pulsating stars with Kepler. IV. Detection limits and radial velocity verification

    CERN Document Server

    Murphy, Simon J; Bedding, Timothy R

    2016-01-01

    We explore the detection limits of the phase modulation (PM) method of finding binary systems among multi-periodic pulsating stars. The method is an attractive way of finding non-transiting planets in the habitable zones of intermediate mass stars, whose rapid rotation inhibits detections via the radial velocity (RV) method. While oscillation amplitudes of a few mmag are required to find planets, many $\\delta$ Scuti stars have these amplitudes. In sub-optimal cases where the signal-to-noise of the oscillations is lower, low-mass brown dwarfs ($\\sim$13 M$_{\\rm Jup}$) are detectable at orbital periods longer than about 1 yr, and the lowest mass main-sequence stars (0.1-0.2 M$_{\\odot}$) are detectable at all orbital periods where the PM method can be applied. We use purpose-written Markov chain Monte Carlo (MCMC) software for the calculation of the PM orbits, which offers robust uncertainties for comparison with RV solutions. Using Kepler data and ground-based RVs, we verify that these two methods are in agreeme...

  1. Precision velocimetry planet hunting with PARAS: Current performance and lessons to inform future extreme precision radial velocity instruments

    CERN Document Server

    Roy, Arpita; Mahadevan, Suvrath; Chaturvedi, Priyanka; Prasad, Neelam J S S V; Shah, Vishal; Pathan, F M; Anandarao, B G

    2016-01-01

    PARAS is a fiber-fed stabilized high-resolution cross-dispersed echelle spectrograph, located on the 1.2 m telescope in Mt. Abu India. Designed for exoplanet detection, PARAS is capable of single-shot spectral coverage of 3800 - 9600 A, and currently achieving radial velocity (RV) precisions approaching ~1 m/s over several months using simultaneous ThAr calibration. As such, it is one of the few dedicated stabilized fiber-fed spectrographs on small (1-2 m) telescopes that are able to fill an important niche in RV follow-up and stellar characterization. The success of ground-based RV surveys is motivating the push into extreme precisions, with goals of ~10 cm/s in the optical and <1 m/s in the near-infrared (NIR). Lessons from existing instruments like PARAS are invaluable in informing hardware design, providing pipeline prototypes, and guiding scientific surveys. Here we present our current precision estimates of PARAS based on observations of bright RV standard stars, and describe the evolution of the dat...

  2. Precise radial velocities of giant stars. IV. A correlation between surface gravity and radial velocity variation and a statistical investigation of companion properties

    CERN Document Server

    Hekker, S; Aerts, C; Quirrenbach, Andreas G; Reffert, S; Mitchell, D S

    2008-01-01

    Since 1999, we have been conducting a radial velocity survey of 179 K giants using the CAT at UCO/Lick observatory. At present ~20-100 measurements have been collected per star with a precision of 5 to 8 m/s. Of the stars monitored, 145 (80%) show radial velocity (RV) variations at a level >20 m/s, of which 43 exhibit significant periodicities. Our aim is to investigate possible mechanism(s) that cause these observed RV variations. We intend to test whether these variations are intrinsic in nature, or possibly induced by companions, or both. In addition, we aim to characterise the parameters of these companions. A relation between log g and the amplitude of the RV variations is investigated for all stars in the sample. Furthermore, the hypothesis that all periodic RV variations are caused by companions is investigated by comparing their inferred orbital statistics with the statistics of companions around main sequence stars. A strong relation is found between the amplitude of the RV variations and log g in K ...

  3. Characterization of wind velocities in the wake of a full scale wind turbine using three ground-based synchronized WindScanners

    Science.gov (United States)

    Yazicioglu, Hasan; Angelou, Nikolas; Mikkelsen, Torben; José Trujillo, Juan

    2016-09-01

    The wind energy community is in need of detailed full-field measurements in the wake of wind turbines. Here, three dimensional(3D) wind vector field measurements obtained in the near-wake region behind a full-scale test turbine are presented. Specifically, the wake of a NEG Nordtank turbine, installed at Risoe test field, has been measured from 0 to 2 diameters downstream. For this, three ground-based synchronised short-range WindScanners and a spinner lidar have been used. The 3D wind velocity field has been reconstructed in horizontal and vertical planes crossing the hub. The 10-min mean values of the three wind components reveal detailed information regarding the wake properties while propagating downwind over flat terrain. Furthermore, the wake centre is tracked from the measurements and its meander is investigated as function of yaw misalignment of the turbine. The centre-line wake deficit is calculated both in a Nacelle and Moving Frame of Reference. The results can be used in quantitative validation of numerical wake models.

  4. Celestial-mechanical interpretation of the two-way radio measurements of radial velocity of spacecraft for scientific applications

    Science.gov (United States)

    Komovkin, S. V.; Lavrenov, S. M.; Tuchin, A. G.; Tuchin, D. A.; Yaroshevsky, V. S.

    2016-12-01

    The article describes a model of the two-way measurements of radial velocity based on the Doppler effect. The relations are presented for the instantaneous value of the increment range at the time of measurement and the radial velocity of the mid-dimensional interval. The compensation of methodological errors of interpretation of the two-way Doppler measurements is considered.

  5. The Pathfinder Testbed: Exploring Techniques for Achieving Precision Radial Velocities in the Near-Infrared

    CERN Document Server

    Ramsey, Larry; Redman, Stephen; Bender, Chad; Roy, Arpita; Zonak, Stephanie; Sigurdsson, Steinn; Wolszczan, Alex

    2010-01-01

    The Penn State Pathfinder is a prototype warm fiber-fed Echelle spectrograph with a Hawaii-1 NIR detector that has already demonstrated 7-10 m/s radial velocity precision on integrated sunlight. The Pathfinder testbed was initially setup for the Gemini PRVS design study to enable a systematic exploration of the challenges of achieving high radial velocity precision in the near-infrared, as well as to test possible solutions to these calibration challenges. The current version of the Pathfinder has an R3 echelle grating, and delivers a resolution of R~50,000 in the Y, J or H bands of the spectrum. We will discuss the on sky-performance of the Pathfinder during an engineering test run at the Hobby Eberly Telescope as well the results of velocity observations of M dwarfs. We will also discuss the unique calibration techniques we have explored, like Uranium-Neon hollow cathode lamps, notch filter, and modal noise mitigation to enable high precision radial velocity observation in the NIR. The Pathfinder is a proto...

  6. Efficient fitting of multiplanet Keplerian models to radial velocity and astrometry data

    CERN Document Server

    Howard, J T Wright A W

    2009-01-01

    We describe a technique for solving for the orbital elements of multiple planets from radial velocity (RV) and/or astrometric data taken with 1 m/s and microarcsecond precision, appropriate for efforts to detect Earth-massed planets in their stars' habitable zones, such as NASA's proposed Space Interferometry Mission. We include details of calculating analytic derivatives for use in the Levenberg-Marquardt (LM) algorithm for the problems of fitting RV and astrometric data separately and jointly. We also explicate the general method of separating the linear and nonlinear components of a model fit in the context of an LM fit, show how explicit derivatives can be calculated in such a model, and demonstrate the speed up and convergence improvements of such a scheme in the case of a five-planet fit to published radial velocity data for 55 Cnc.

  7. The Probabilities of Orbital-Companion Models for Stellar Radial Velocity Data

    CERN Document Server

    Hou, Fengji; Hogg, David W

    2014-01-01

    The fully marginalized likelihood, or Bayesian evidence, is of great importance in probabilistic data analysis, because it is involved in calculating the posterior probability of a model or re-weighting a mixture of models conditioned on data. It is, however, extremely challenging to compute. This paper presents a geometric-path Monte Carlo method, inspired by multi-canonical Monte Carlo to evaluate the fully marginalized likelihood. We show that the algorithm is very fast and easy to implement and produces a justified uncertainty estimate on the fully marginalized likelihood. The algorithm performs efficiently on a trial problem and multi-companion model fitting for radial velocity data. For the trial problem, the algorithm returns the correct fully marginalized likelihood, and the estimated uncertainty is also consistent with the standard deviation of results from multiple runs. We apply the algorithm to the problem of fitting radial velocity data from HIP 88048 ($\

  8. Radial velocity follow-up of CoRoT transiting exoplanets

    Directory of Open Access Journals (Sweden)

    Deleuil M.

    2011-02-01

    Full Text Available We report on the results from the radial-velocity follow-up program performed to establish the planetary nature and to characterize the transiting candidates discovered by the space mission CoRoT. We use the SOPHIE at OHP, HARPS at ESO and the HIRES at Keck spectrographs to collect spectra and high-precision radial velocity (RV measurements for several dozens different candidates from CoRoT. We have measured the Rossiter-McLaughlin effect of several confirmed planets, especially CoRoT-1b which revealed that it is another highly inclined system. Such high-precision RV data are necessary for the discovery of new transiting planets. Furthermore, several low mass planet candidates have emerged from our Keck and HARPS data.

  9. An Affine-Invariant Sampler for Exoplanet Fitting and Discovery in Radial Velocity Data

    CERN Document Server

    Hou, Fengji; Hogg, David W; Weare, Jonathan; Schwab, Christian

    2011-01-01

    Markov Chain Monte Carlo (MCMC) proves to be powerful for Bayesian inference and in particular for exoplanet radial velocity fitting because MCMC provides more statistical information and makes better use of data than common approaches like chi-square fitting. However, the non-linear density functions encountered in these problems can make MCMC time-consuming. In this paper, we apply an ensemble sampler respecting affine invariance to orbital parameter extraction from radial velocity data. The autocorrelation time of this sampler is approximately the same for all parameters and far smaller than Metropolis-Hastings, which means it requires many fewer function calls to produce the same number of independent samples. The affine-invariant sampler speeds up MCMC by hundreds of times compared with Metropolis-Hastings in the same computing situation. Besides being fast, the new sampler has only one free parameter, and it does not require tuning for good performance, which is important for automatization. This novel ...

  10. A multi-method approach to radial-velocity measurement for single-object spectra

    CERN Document Server

    David, M; Frémat, Y; Damerdji, Y; Luche, C Delle; Gosset, E; Katz, D; Viala, Y

    2014-01-01

    The derivation of radial velocities from large numbers of spectra that typically result from survey work, requires automation. However, except for the classical cases of slowly rotating late-type spectra, existing methods of measuring Doppler shifts require fine-tuning to avoid a loss of accuracy due to the idiosyncrasies of individual spectra. The radial velocity spectrometer (RVS) on the Gaia mission, which will start operating very soon, prompted a new attempt at creating a measurement pipeline to handle a wide variety of spectral types. The present paper describes the theoretical background on which this software is based. However, apart from the assumption that only synthetic templates are used, we do not rely on any of the characteristics of this instrument, so our results should be relevant for most telescope-detector combinations. We propose an approach based on the simultaneous use of several alternative measurement methods, each having its own merits and drawbacks, and conveying the spectral informa...

  11. Accounting for Convective Blue-Shifts in the Determination of Absolute Stellar Radial Velocities

    CERN Document Server

    Prieto, C Allende; Ramírez, I; Ludwig, H -G; Asplund, M

    2009-01-01

    For late-type non-active stars, gravitational redshifts and convective blueshifts are the main source of biases in the determination of radial velocities. If ignored, these effects can introduce systematic errors of the order of ~ 0.5 km/s. We demonstrate that three-dimensional hydrodynamical simulations of solar surface convection can be used to predict the convective blue-shifts of weak spectral lines in solar-like stars to ~ 0.070 km/s. Using accurate trigonometric parallaxes and stellar evolution models, the gravitational redshifts can be constrained with a similar uncertainty, leading to absolute radial velocities accurate to better than ~ 0.1 km/s.

  12. Astrophysical Sources of Statistical Uncertainty in Precision Radial Velocities and Their Approximations

    CERN Document Server

    Beatty, Thomas G

    2015-01-01

    We investigate astrophysical contributions to the statistical uncertainty of precision radial velocity measurements of stellar spectra. We analytically determine the uncertainty in centroiding isolated spectral lines broadened by Gaussian, Lorentzian, Voigt, and rotational profiles, finding that for all cases and assuming weak lines, the uncertainty is the line centroid is $\\sigma_V\\approx C\\,\\Theta^{3/2}/(W I_0^{1/2})$, where $\\Theta$ is the full-width at half-maximum of the line, $W$ is the equivalent width, and $I_0$ is the continuum signal-to-noise ratio, with $C$ a constant of order unity that depends on the specific line profile. We use this result to motivate approximate analytic expressions to the total radial velocity uncertainty for a stellar spectrum with a given photon noise, resolution, wavelength, effective temperature, surface gravity, metallicity, macroturbulence, and stellar rotation. We use these relations to determine the dominant contributions to the statistical uncertainties in precision ...

  13. Towards a new full-sky list of radial velocity standard stars

    CERN Document Server

    Crifo, F; Soubiran, C; Katz, D; Siebert, A; Veltz, L; Udry, S

    2010-01-01

    The calibration of the Radial Velocity Spectrometer (RVS) onboard the ESA Gaia satellite (to be launched in 2012) requires a list of standard stars with a radial velocity (RV) known with an accuracy of at least 300 m/s. The IAU Commission 30 lists of RV standard stars are too bright and not dense enough. We describe the selection criteria due to the RVS constraints for building an adequate full-sky list of at least 1000 RV standards from catalogues already published in the literature. A preliminary list of 1420 candidate standard stars is built and its properties are shown. An important re-observation programme has been set up in order to ensure within it the selection of objects with a good stability until the end of the Gaia mission (around 2018). The present list of candidate standards is available at CDS and usable for many other projects.

  14. Miniature Exoplanet Radial Velocity Array (MINERVA) I. Design, Commissioning, and First Science Results

    CERN Document Server

    Swift, Jonathan J; Johnson, John A; Wright, Jason T; McCrady, Nate; Wittenmyer, Robert A; Plavchan, Peter; Riddle, Reed; Muirhead, Philip S; Herzig, Erich; Myles, Justin; Blake, Cullen H; Eastman, Jason; Beatty, Thomas G; Lin, Brian; Zhao, Ming; Gardner, Paul; Falco, Emilio; Criswell, Stephen; Nava, Chantanelle; Robinson, Connor; Sliski, David H; Hedrick, Richard; Ivarsen, Kevin; Hjelstrom, Annie; de Vera, Jon; Szentgyorgyi, Andrew

    2014-01-01

    The MINiature Exoplanet Radial Velocity Array (MINERVA) is a US-based observational facility dedicated to the discovery and characterization of exoplanets around a nearby sample of bright stars. MINERVA employs a robotic array of four 0.7 m telescopes outfitted for both high-resolution spectroscopy and photometry, and is designed for completely autonomous operation. The primary science program is a dedicated radial velocity survey and the secondary science objective is to obtain high precision transit light curves. The modular design of the facility and the flexibility of our hardware allows for both science programs to be pursued simultaneously, while the robotic control software provides a robust and efficient means to carry out nightly observations. In this article, we describe the design of MINERVA including major hardware components, software, and science goals. The telescopes and photometry cameras are characterized at our test facility on the Caltech campus in Pasadena, CA, and their on-sky performance...

  15. Investigation of the Pleiades cluster. I - Radial velocities of corona stars

    Science.gov (United States)

    Rosvick, J. M.; Mermilliod, J.-C.; Mayor, M.

    1992-02-01

    Coravel radial velocities of 83 stars ranging in spectral types from F5 to K0 selected frozen van Leeuwen's et al. (1986) survey of the corona of the Pleiades show that only 56 are actually members. Six spectroscopic binaries among the members and two among the nonmembers have been found. The large extent of the cluster over the sky also induces a radial-velocity gradient from which a convergent point has been determined. Since the cluster's depth is so large, the width of the main sequence is increased. The present results lead to a star density of 1.1 stars per sq deg for r between 2.5 and 3.5 deg. However, we stress that this is only a preliminary result, since the sample of stars in the corona is incomplete.

  16. CARMENES: A New Visible/Near-IR Radial-Velocity Spectrograph

    Science.gov (United States)

    Quirrenbach, Andreas; Carmenes Consortium

    2016-07-01

    CARMENES is a next-generation radial-velocity instrument that has been constructed for the 3.5m telescope at the Calar Alto Observatory by a consortium of eleven Spanish and German institutions. It consists of two separate échelle spectrographs covering the wavelength range from 0.55 to 1.7μm at a spectral resolution of R = 82,000, fed by fibers from the Cassegrain focus of the telescope. CARMENES saw "First Light" on Nov 9, 2015. We report on results from the commissioning and the first months of operation, and discuss the plans for the large M dwarf survey that is the core science program of CARMENES. With a bit of luck, CARMENES may find a few planets that are very well suited for characterization by JWST. In the longer run, CARMENES will be an excellent instrument for radial-velocity follow-up of transit survey missions such as TESS and PLATO.

  17. An Inexpensive Field-Widened Monolithic Michelson Interferometer for Precision Radial Velocity Measurements

    OpenAIRE

    Mahadevan, Suvrath; Ge, Jian; Fleming, Scott W.; Wan, Xiaoke; DeWitt, Curtis; van Eyken, Julian C.; McDavitt, Dan

    2008-01-01

    We have constructed a thermally compensated field-widened monolithic Michelson interferometer that can be used with a medium-resolution spectrograph to measure precise Doppler radial velocities of stars. Our prototype monolithic fixed-delay interferometer is constructed with off-the-shelf components and assembled using a hydrolysis bonding technique. We installed and tested this interferometer in the Exoplanet Tracker (ET) instrument at the Kitt Peak 2.1m telescope, an instrument built to dem...

  18. VizieR Online Data Catalog: Radial velocities of 76 M31 candidate clusters (Galleti+, 2006)

    Science.gov (United States)

    Galleti, S.; Federici, L.; Bellazzini, M.; Buzzoni, A.; Fusi Pecci, F.

    2006-06-01

    We present the first results of a large spectroscopic survey of globular clusters and candidate globular clusters in the nearby M31 galaxy. The survey is aimed at the classification of known candidate M31 clusters and at the study of their kinematic properties. We obtained low-resolution spectroscopy for 133 targets, including 76 yet-to-be-confirmed candidate clusters (i.e. with no previous spectroscopic information), 55 already-confirmed genuine M31 clusters, and 2 uncertain candidates. Our observations allowed a reliable estimate of the target radial velocity, within a typical accuracy of ~+/-20Km/s. The observed candidates have been robustly classified according to their radial velocity and shape parameters that allowed us to confidently discriminate between point sources and extended objects even from low-spatial-resolution imagery. In our set of 76 candidate clusters we found: 42 newly-confirmed bona-fide M31 clusters, 12 background galaxies, 17 foreground Galactic stars, 2 HII regions belonging to M31 and 3 unclassified (possibly M31 clusters or foreground stars) objects. The classification of a few other candidates not included in our survey has been also reassessed on various observational bases. All the sources of radial velocity estimates for M31 known globular clusters available in the literature have been compared and checked, and a homogeneous general list has been obtained for 349 confirmed clusters with radial velocity. Our results suggest that a significant number of genuine clusters (~>100) is still hidden among the plethora of known candidates proposed by various authors. Hence our knowledge of the globular cluster system of the M31 galaxy is still far from complete even in terms of simple membership. (1 data file).

  19. Finding binaries from phase modulation of pulsating stars with Kepler - IV. Detection limits and radial velocity verification

    Science.gov (United States)

    Murphy, Simon J.; Shibahashi, Hiromoto; Bedding, Timothy R.

    2016-10-01

    We explore the detection limits of the phase modulation (PM) method of finding binary systems among multiperiodic pulsating stars. The method is an attractive way of finding non-transiting planets in the habitable zones of intermediate-mass stars, whose rapid rotation inhibits detections via the radial velocity (RV) method. While oscillation amplitudes of a few mmag are required to find planets, many δ Scuti stars have these amplitudes. In suboptimal cases where the signal to noise of the oscillations is lower, low-mass brown dwarfs (˜13MJup) are detectable at orbital periods longer than about 1 yr, and the lowest mass main-sequence stars (0.1-0.2 M⊙) are detectable at all orbital periods where the PM method can be applied. We use purpose-written Markov chain Monte Carlo (MCMC) software for the calculation of the PM orbits, which offers robust uncertainties for comparison with RV solutions. Using Kepler data and ground-based RVs, we verify that these two methods are in agreement, even at short orbital periods where the PM method undersamples the orbit. We develop new theory to account for the undersampling of the time delays, which is also necessary for the inclusion of RVs as observational data in the MCMC software. We show that combining RVs with time delays substantially refines the orbits because of the complementarity of working in both the spatial (PM) and velocity (RV) domains simultaneously. Software outputs were tested through an extensive hare-and-hounds exercise, covering a wide range of orbital configurations including binaries containing two pulsators.

  20. The Gaia-ESO Survey: Empirical determination of the precision of stellar radial velocities and projected rotation velocities

    CERN Document Server

    Jackson, R J; Lewis, J; Koposov, S E; Sacco, G G; Randich, S; Gilmore, G; Asplund, M; Binney, J; Bonifacio, P; Drew, J E; Feltzing, S; Ferguson, A M N; Micela, G; Neguerela, I; Prusti, T; Rix, H-W; Vallenari, A; Alfaro, E J; Allende~Prieto, C; Babusiaux, C; Bensby, T; Blomme, R; Bragaglia, A; Flaccomio, E; Francois, P; Hambly, N; Irwin, M; Korn, A J; Lanzafame, A C; Pancino, E; Recio-Blanco, A; Smiljanic, R; Van Eck, S; Walton, N; Bayo, A; Bergemann, M; Carraro, G; Costado, M T; Damiani, F; Edvardsson, B; Franciosini, E; Frasca, A; Heiter, U; Hill, V; Hourihane, A; Jofre, P; Lardo, C; de Laverny, P; Lind, K; Magrini, L; Marconi, G; Martayan, C; Masseron, T; Monaco, L; Morbidelli, L; Prisinzano, L; Sbordone, L; Sousa, S G; Worley, C C; Zaggia, S

    2015-01-01

    The Gaia-ESO Survey (GES) is a large public spectroscopic survey at the European Southern Observatory Very Large Telescope. A key aim is to provide precise radial velocities (RVs) and projected equatorial velocities (v sin i) for representative samples of Galactic stars, that will complement information obtained by the Gaia astrometry satellite. We present an analysis to empirically quantify the size and distribution of uncertainties in RV and v sin i using spectra from repeated exposures of the same stars. We show that the uncertainties vary as simple scaling functions of signal-to-noise ratio (S/N) and v sin i, that the uncertainties become larger with increasing photospheric temperature, but that the dependence on stellar gravity, metallicity and age is weak. The underlying uncertainty distributions have extended tails that are better represented by Student's t-distributions than by normal distributions. Parametrised results are provided, that enable estimates of the RV precision for almost all GES measure...

  1. An Affine-invariant Sampler for Exoplanet Fitting and Discovery in Radial Velocity Data

    Science.gov (United States)

    Hou, Fengji; Goodman, Jonathan; Hogg, David W.; Weare, Jonathan; Schwab, Christian

    2012-02-01

    Markov chain Monte Carlo (MCMC) proves to be powerful for Bayesian inference and in particular for exoplanet radial velocity fitting because MCMC provides more statistical information and makes better use of data than common approaches like chi-square fitting. However, the nonlinear density functions encountered in these problems can make MCMC time-consuming. In this paper, we apply an ensemble sampler respecting affine invariance to orbital parameter extraction from radial velocity data. This new sampler has only one free parameter, and does not require much tuning for good performance, which is important for automatization. The autocorrelation time of this sampler is approximately the same for all parameters and far smaller than Metropolis-Hastings, which means it requires many fewer function calls to produce the same number of independent samples. The affine-invariant sampler speeds up MCMC by hundreds of times compared with Metropolis-Hastings in the same computing situation. This novel sampler would be ideal for projects involving large data sets such as statistical investigations of planet distribution. The biggest obstacle to ensemble samplers is the existence of multiple local optima; we present a clustering technique to deal with local optima by clustering based on the likelihood of the walkers in the ensemble. We demonstrate the effectiveness of the sampler on real radial velocity data.

  2. AN AFFINE-INVARIANT SAMPLER FOR EXOPLANET FITTING AND DISCOVERY IN RADIAL VELOCITY DATA

    Energy Technology Data Exchange (ETDEWEB)

    Hou Fengji; Hogg, David W. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Goodman, Jonathan; Weare, Jonathan [Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, NY 10012 (United States); Schwab, Christian, E-mail: fh417@nyu.edu [Department of Astronomy, Yale University, 260 Whitney Avenue, New Haven, CT 06511 (United States)

    2012-02-01

    Markov chain Monte Carlo (MCMC) proves to be powerful for Bayesian inference and in particular for exoplanet radial velocity fitting because MCMC provides more statistical information and makes better use of data than common approaches like chi-square fitting. However, the nonlinear density functions encountered in these problems can make MCMC time-consuming. In this paper, we apply an ensemble sampler respecting affine invariance to orbital parameter extraction from radial velocity data. This new sampler has only one free parameter, and does not require much tuning for good performance, which is important for automatization. The autocorrelation time of this sampler is approximately the same for all parameters and far smaller than Metropolis-Hastings, which means it requires many fewer function calls to produce the same number of independent samples. The affine-invariant sampler speeds up MCMC by hundreds of times compared with Metropolis-Hastings in the same computing situation. This novel sampler would be ideal for projects involving large data sets such as statistical investigations of planet distribution. The biggest obstacle to ensemble samplers is the existence of multiple local optima; we present a clustering technique to deal with local optima by clustering based on the likelihood of the walkers in the ensemble. We demonstrate the effectiveness of the sampler on real radial velocity data.

  3. The Rotation of the halo of NGC 6822 from the radial velocities of carbon stars

    CERN Document Server

    Thompson, Graham P; Sibbons, Lisette F

    2016-01-01

    Using spectra taken with the AAOmega spectrograph, we measure the radial velocities of over 100 stars, many of which are intermediate age carbon stars, in the direction of the dwarf irregular galaxy NGC 6822. Kinematic analysis suggests that the carbon stars in the sample are associated with NGC 6822, and estimates of its radial velocity and galactic rotation are made from a star-by-star analysis of its carbon star population. We calculate a heliocentric radial velocity for NGC 6822 of $-51\\pm3$ \\kms\\ and show that the population rotates with a mean rotation speed of $11.2\\pm2.1$ \\kms\\ at a mean distance of 1.1 kpc from the galactic centre, about a rotation axis with a position angle of $26^\\circ\\pm13^\\circ$, as projected on the sky. This is close to the rotation axis of the HI gas disk and suggests that NGC 6822 is not a polar ring galaxy, but is dynamically closer to a late type galaxy. However, the rotation axis is not aligned with the minor axis of the AGB isodensity profiles and this remains a mystery.

  4. Miniature Exoplanet Radial Velocity Array (MINERVA) I. Design, Commissioning, and First Science Results

    Science.gov (United States)

    Swift, Jonathan J.; Bottom, Michael; Johnson, John A.; Wright, Jason T.; McCrady, Nate; Wittenmyer, Robert A.; Plavchan, Peter; Riddle, Reed; Muirhead, Philip S.; Herzig, Erich; Myles, Justin; Blake, Cullen H.; Eastman, Jason; Beatty, Thomas G.; Barnes, Stuart I.; Gibson, Steven R.; Lin, Brian; Zhao, Ming; Gardner, Paul; Falco, Emilio; Criswell, Stephen; Nava, Chantanelle; Robinson, Connor; Sliski, David H.; Hedrick, Richard; Ivarsen, Kevin; Hjelstrom, Annie; de Vera, Jon; Szentgyorgyi, Andrew

    2015-04-01

    The Miniature Exoplanet Radial Velocity Array (MINERVA) is a U.S.-based observational facility dedicated to the discovery and characterization of exoplanets around a nearby sample of bright stars. MINERVA employs a robotic array of four 0.7-m telescopes outfitted for both high-resolution spectroscopy and photometry, and is designed for completely autonomous operation. The primary science program is a dedicated radial velocity survey and the secondary science objective is to obtain high-precision transit light curves. The modular design of the facility and the flexibility of our hardware allows for both science programs to be pursued simultaneously, while the robotic control software provides a robust and efficient means to carry out nightly observations. We describe the design of MINERVA, including major hardware components, software, and science goals. The telescopes and photometry cameras are characterized at our test facility on the Caltech campus in Pasadena, California, and their on-sky performance is validated. The design and simulated performance of the spectrograph is briefly discussed as we await its completion. New observations from our test facility demonstrate sub-mmag photometric precision of one of our radial velocity survey targets, and we present new transit observations and fits of WASP-52b-a known hot-Jupiter with an inflated radius and misaligned orbit. The process of relocating the MINERVA hardware to its final destination at the Fred Lawrence Whipple Observatory in southern Arizona has begun, and science operations are expected to commence in 2015.

  5. Removing Activity-Related Radial Velocity Noise to Improve Extrasolar Planet Searches

    Science.gov (United States)

    Saar, Steven; Lindstrom, David M. (Technical Monitor)

    2004-01-01

    We have made significant progress towards the proposal goals of understanding the causes and effects of magnetic activity-induced radial velocity (v_r) jitter and developing methods for correcting it. In the process, we have also made some significant discoveries in the fields of planet-induced stellar activity, planet detection methods, M dwarf convection, starspot properties, and magnetic dynamo cycles. We have obtained super high resolution (R approximately 200,000), high S / N (greater than 300) echelle study of joint line bisector and radial velocity variations using the McDonald 2-D coude. A long observing run in October 2002 in particular was quite successful (8 clear nights). We now have close to three years of data, which begins to sample a good fraction of the magnetic cycle timescales for some of our targets (e.g., kappa Ceti; P_cyc = 5.6 yrs). This will be very helpful in unraveling the complex relationships between plage and radial velocity (v-r) changes which we have uncovered. Preliminary analysis (Saar et al. 2003) of the data in hand, reveals correlations between median line bisector displacement and v_r. The correlation appears to be specific the the particular star being considered, probably since it is a function of both spectral type and rotation rate. Further analysis and interpretation will be in the context of evolving plage models and is in progress.

  6. Uncovering the planets and stellar activity of CoRoT-7 using only radial velocities

    Science.gov (United States)

    Faria, J. P.; Haywood, R. D.; Brewer, B. J.; Figueira, P.; Oshagh, M.; Santerne, A.; Santos, N. C.

    2016-04-01

    Stellar activity can induce signals in the radial velocities of stars, complicating the detection of orbiting low-mass planets. We present a method to determine the number of planetary signals present in radial-velocity datasets of active stars, using only radial-velocity observations. Instead of considering separate fits with different number of planets, we use a birth-death Markov chain Monte Carlo algorithm to infer the posterior distribution for the number of planets in a single run. In a natural way, the marginal distributions for the orbital parameters of all planets are also inferred. This method is applied to HARPS data of CoRoT-7. We confidently recover the orbits of both CoRoT-7b and CoRoT-7c although the data show evidence for the presence of additional signals. All data and software presented in this article are available online at http://https://github.com/j-faria/exoBD-CoRoT7

  7. Radial velocities and metallicities of red giant stars in the old open cluster NGC 7762

    CERN Document Server

    Carraro, Giovanni; Villanova, Sandro

    2016-01-01

    We present and discuss radial velocity and the very first metallicity measurements for nine evolved stars in the poorly known old open cluster NGC 7762. We isolated eight radial velocity cluster members and one interloper. Radial velocities are in good agreement with previous studies. NGC 7762 turns out to be of solar metallicity within the uncertainties ([Fe/H]=0.04$\\pm$0.12). For this metallicity, the cluster age is 2.5$\\pm$0.2 Gyr, and falls in a age range where only a few old open clusters are known. With respect to previous studies, we find a larger distance, implying the cluster to be located at 900$^{+70}_{-50}$ pc from the Sun. For most of the elements we measure solar-scaled abundance ratios. We searched the literature for open clusters of similar age in the solar vicinity and found that NGC 7762 can be considered a twin of Ruprecht 147, a similar age cluster located at only 300 pc from the Sun. In fact, beside age, also metallicity and abundance ratios are very close to Ruprecht 147 values within th...

  8. Long-lived, long-period radial velocity variations in Aldebaran: A planetary companion and stellar activity

    CERN Document Server

    Hatzes, A P; Endl, M; Guenther, E W; MacQueen, P; Hartmann, M; Zechmeister, M; Han, I; Lee, B -C; Walker, G A H; Yang, S; Larson, A M; Kim, K -M; Mkrtichian, D E; Doellinger, M; Simon, A E; Girardi, L

    2015-01-01

    We investigate the nature of the long-period radial velocity variations in Alpha Tau first reported over 20 years ago. We analyzed precise stellar radial velocity measurements for Alpha Tau spanning over 30 years. An examination of the Halpha and Ca II 8662 spectral lines, and Hipparcos photometry was also done to help discern the nature of the long-period radial velocity variations. Our radial velocity data show that the long-period, low amplitude radial velocity variations are long-lived and coherent. Furthermore, Halpha equivalent width measurements and Hipparcos photometry show no significant variations with this period. Another investigation of this star established that there was no variability in the spectral line shapes with the radial velocity period. An orbital solution results in a period of P = 628.96 +/- 0.90 d, eccentricity, e = 0.10 +/- 0.05, and a radial velocity amplitude, K = 142.1 +/- 7.2 m/s. Evolutionary tracks yield a stellar mass of 1.13 +/- 0.11 M_sun, which corresponds to a minimum co...

  9. Photoelectric Radial Velocities, Paper XIX Additional Spectroscopic Binaries among the Redman K Stars

    Indian Academy of Sciences (India)

    R. F. Griffin

    2012-06-01

    The `Redman K stars’ project, described more particularly in the paper immediately following this one, involved the repeated measurement on a quasi-annual basis of the radial velocities of a group of 86 seventh-magnitude late-type stars over an interval of 45 years. Certain of the stars proved to vary in velocity and were then transferred to a different observing programme, in which they were measured more frequently with a view to determining their orbits. Orbits have already been published for 18 of the stars. Presented here (and summarized in Table 9) are the results on six more; all are single-lined. One of them (HD 191046, a star which has a literature coverage about ten times as rich as that of any of the others, probably on account of its high space velocity which includes a -velocity of nearly -100 km s-1) has a good orbit with a period of about 8000 days (22 years). Five others (HD 3345, 15728, 20509, 188058 and 191084) have orbits that are perfectly secure in principle, but their periods range between 40 and perhaps 70 years, and (particularly in some cases) their radial velocities have not been observed well enough for long enough to establish either the periods or the orbits very accurately. One star, HD 9354, has exhibited a monotonic variation of velocity throughout the duration of the observing programme; it is possible to draw a Keplerian velocity curve that does justice to the measurements, but it cannot be expected to have much predictive power.

  10. A catalog of UGC isolated galaxy pairs with accurate radial velocities

    CERN Document Server

    Chamaraux, Pierre

    2016-01-01

    The present paper is devoted to the construction of a catalog of isolated galaxy pairs from the Uppsala Galaxy Catalog (UGC), using accurate radial velocities. The UGC lists 12921 galaxies to declination larger than -2 deg 30 min and is complete to an apparent diameter of 1 arcmin. The criteria used to define the isolated galaxy pairs are the following: 1) Velocity criterion: radial velocity difference between the members lower than 500 km/s; 2) Interdistance criterion: projected distance between the members smaller than 1 Mpc; 3) Reciprocity criterion: each member is the closest galaxy to the other one, which excludes multiplets; 4) Isolation information: the catalog lists the ratio between the projected distance to the closest UGC galaxy (having a velocity difference smaller than 500 km/s) and the pair members interdistance, thus allowing one to choose any isolation criterion (beyond the chosen limit 2.5). In addition, we have accounted for the small diameter bias by searching for CGCG galaxies in the pair ...

  11. Tangential Velocity Profile for Axial Flow Through Two Concentric Rotating Cylinders with Radial Magnetic Field

    Directory of Open Access Journals (Sweden)

    Girishwar Nath

    1970-10-01

    Full Text Available A closed form solution of the Navier-Stokes equations has been obtained in the case of steady axisymmetric flow of an incompressible electrically conducting viscous fluid between two concentric rotating cylinders composed of an insulating material under the influence of radial magnetic field. It has been found that the velocity components are less than those of the classical hydrodynamic case. In the presence of the magnetic field, the tangential velocity becomes fully developed in a smaller axial distance than in the absence of the magnetic field. For small Reynolds number, the fully developed tangential velocity is achieved in a small axial distance, but it requires greater axial distance for large Reynolds number.

  12. VizieR Online Data Catalog: Radial velocities of 7 cataclysmic binaries (Halpern+, 2015)

    Science.gov (United States)

    Halpern, J. P.; Thorstensen, J. R.

    2016-04-01

    Our instrumentation, and reduction and analysis procedures are essentially identical to those described in Paper I (Thorstensen et al. 2013, cat. J/AJ/146/107). All of our optical data are from the MDM Observatory (http://mdm.kpno.noao.edu/index/Instrumentation.html), which comprises the 1.3m McGraw-Hill telescope and the 2.4m Hiltner telescope, both on the southwest ridge of Kitt Peak, Arizona. With a single exception, the radial velocity studies to search for the orbital periods were done on the 2.4m, while high-cadence photometry sensitive to spin periods was carried out on the 1.3m. All of our radial velocity studies used the modular spectrograph, as described in Paper I (Thorstensen et al. 2013, cat. J/AJ/146/107). Most of our velocities are from the the 2.4m telescope. Some spectra of Swift J2124.6+0500, and all the data we used for Swift J0939.7-3224, are from the McGraw-Hill 1.3m telescope, again with the modular spectrograph. For four newly identified objects we have only single spectra that were obtained on two observing runs on the 2.4m. These used the Boller and Chivens CCD spectrograph (CCDS) and the Ohio State Multi-Object Spectrograph (OSMOS). Descriptions of these instruments can be found on the MDM Observatory web page (http://mdm.kpno.noao.edu/index/Instrumentation.html). The objects observed are listed in Table1. Table2 lists the radial velocity data, and Table3 gives parameters of the best-fit sinusoids. (3 data files).

  13. Characterization of azimuthal and radial velocity fields induced by rotors in low-Reynolds number flows

    CERN Document Server

    Köhler, Jannis; Ostendorf, Andreas; Gurevich, Evgeny

    2015-01-01

    We theoretically and experimentally investigate the flow field that emerges from a rod-like microrotor rotating about its center in a non-axisymmetric manner. A simple theoretical model is proposed that uses a superposition of two rotlets as a fundamental solution to the Stokes equation. The predictions of this model are compared to measurements of the azimuthal and radial microfluidic velocity field components that are induced by a rotor composed of fused microscopic spheres. The rotor is driven magnetically and the fluid flow is measured with help of a probe particle fixed by an optical tweezer. We find considerable deviations of the mere azimuthal flow pattern induced by a single rotating sphere as it has been reported by Di Leonardo \\textit{et al.} [Phys. Rev. Lett. 96, 134502 (2006)]. Notably, the presence of a radial velocity component that manifests itself by an oscillation of the probe particle with twice the rotor frequency is observed. These findings open up a way to discuss possible radial transpor...

  14. Line-profile variations in radial-velocity measurements: Two alternative indicators for planetary searches

    CERN Document Server

    Figueira, P; Pepe, F; Lovis, C; Nardetto, N

    2013-01-01

    Aims. We introduce two methods to identify false-positive planetary signals in the context of radial-velocity exoplanet searches. The first is the bi-Gaussian cross-correlation function fitting, and the second is the measurement of asymmetry in radial-velocity spectral line information content, Vasy. Methods. We make a systematic analysis of the most used common line profile diagnosis, Bisector Inverse Slope and Velocity Span, along with the two proposed ones. We evaluate all these diagnosis methods following a set of well-defined common criteria and using both simulated and real data. We apply them to simulated cross-correlation functions created with the program SOAP and which are affected by the presence of stellar spots, and to real cross-correlation functions, calculated from HARPS spectra, for stars with a signal originating both in activity and created by a planet. Results. We demonstrate that the bi-Gaussian method allows a more precise characterization of the deformation of line profiles than the sta...

  15. Radial and Azimuthal Velocity Profiles in Gas-Puff Z-Pinches

    Science.gov (United States)

    Rocco, Sophia; Engelbrecht, Joseph; Banasek, Jacob; de Grouchy, Philip; Qi, Niansheng; Hammer, David

    2016-10-01

    The dynamics of neon, argon, and krypton (either singly or in combination) gas puff z-pinch plasmas are studied on Cornell's 1MA, 100-200ns rise-time COBRA pulsed power generator. The triple-nozzle gas puff valve, consisting of two annular gas puffs and a central jet, allows radial tailoring of the gas puff mass-density profile and the use of 1, 2 or 3 different gases at different pressures. Interferometry supplies information on sheath thickness and electron density, variously filtered PCDs and silicon diodes measure hard and soft x-ray production, and multi frame visible and extreme UV imaging systems allow tracking of the morphology of the plasma. A 527nm, 10J Thomson scattering diagnostic system is used to determine radial and azimuthal velocities. Implosion velocities of 170km/s (Kr) and 300km/s (Ne/Ar) are observed. We are investigating the correlations between instability growth, plasma density profile, velocity partitioning as a function of radius, and radiation production. Research supported by the NNSA Stewardship Sciences Academic Programs under DOE Cooperative Agreement No. DE-NA0001836.

  16. Precise Near-Infrared Radial Velocities with the TripleSpec Exoplanet Discovery Instrument (TEDI)

    Science.gov (United States)

    Muirhead, Philip; Edelstein, J.; Erskine, D. J.; Hamren, K. M.; Covey, K. R.; Lloyd, J. P.

    2011-01-01

    Attaining 10 m/s of Doppler velocity precision with near-infrared (NIR) spectroscopy enables the detection and mass measurement of terrestrial-mass and larger exoplanets orbiting mid-to-late M dwarf stars. This is especially exciting considering that JWST has the sensitivity to detect oxygen, an indicator of life, in the atmospheres of terrestrial planets transiting mid-to-late M dwarfs. Radial velocities are required to verify planetary transits. TEDI is an instrument on the Palomar Hale Telescope designed to measure precise NIR radial velocities. It is the combination of a variable-delay interferometer and TripleSpec, a resolution 2700 spectrograph covering 1.0 to 2.5 microns simultaneously. This technique has the potential for broad implementation on 4-meter-class telescopes, for both NIR RV measurements and high-resolution NIR spectroscopy. I will describe the instrument, method, data analysis, and recent results from TEDI, as all are a part of my Ph.D. dissertation at Cornell.

  17. Spectroscopic survey of the Galaxy with Gaia I. Design and performance of the Radial Velocity Spectrometer

    CERN Document Server

    Katz, D; Bono, G; Boschi, F; Crifo, F; Cropper, M; David, M; Gomboc, A; Gómez, A; Haywood, M; Helmi, A; Marrese, P M; Morin, D; Munari, U; Perryman, M; Royer, F; Sordo, R; Soubiran, C; Thévenin, F; Tomasella, L; Turon, C; Vallenari, A; Viala, Y; Wilkinson, M; Zwitter, T

    2004-01-01

    The definition and optimisation studies for the Gaia satellite spectrograph, the Radial Velocity Spectrometer (RVS), converged in late 2002 with the adoption of the instrument baseline. This paper reviews the characteristics of the selected configuration and presents its expected performance. The RVS is a 2.0 by 1.6 degree integral field spectrograph, dispersing the light of all sources entering its field of view with a resolving power R=11 500 over the wavelength range [848, 874] nm. The RVS will continuously and repeatedly scan the sky during the 5 years of the Gaia mission. On average, each source will be observed 102 times over this period. The RVS will collect the spectra of about 100-150 million stars up to magnitude V~17-18. At the end of the mission, the RVS will provide radial velocities with precisions of ~2 km/s at V=15 and \\~15-20 km/s at V=17, for a solar metallicity G5 dwarf. The RVS will also provide rotational velocities, with precisions (at the end of the mission) for late type stars of sigma...

  18. Mapping the Tidewater Submarine and Ice-Marginal Environment Using Interferometric Bathymetry, Ground-Based LiDAR and Current Velocities; Hubbard Glacier, Alaska

    Science.gov (United States)

    Finnegan, D. C.; Lawson, D. E.; Butler, W.; Waller, T.; Pratt, T.

    2009-12-01

    The seasonal advance and retreat of tidewater glaciers is a relatively well-documented phenomenon. But our understanding of the processes and conditions within the ice-marginal submarine environment that drive or result from this activity is limited. Capturing holistic information within this environment such as bathymetric topography, hydrographic measurements and geospatial information about the terminus itself is often limited to discrete measurements far from the terminus grounding line or lack the detail and scale necessary to identify features that may be indicative of process. To understand these processes, it is essential to accurately obtain data at resolutions that are sufficient to understand the geologic and marine environment. This paper describes the results of a first-of-its-kind survey of the submarine and ice-marginal terrestrial environment of the Hubbard Glacier tidewater terminus. Hubbard Glacier is the largest non-polar tidewater glacier in the world. It encompasses an area of 3500 sq km and flows 120 km from the flanks of Mt Logan (5959 m) in the Wrangell St. Elias Mountains (Canada) to sea level where its terminus widens to ~13 km. In contrast to most glaciers in Southeast Alaska, Hubbard Glacier continues to advance and thicken and is predicted to continue for the foreseeable future. We utilize a multi-sensor fusion approach that integrates high-resolution interferometric (swath-based) multibeam bathymetry with high-resolution ground-based LiDAR topography and current velocity profiles to provide a detailed look at the section of the glacier where significant ice advance and potential ice-damming occurs. Through simultaneous collection of these data we are able to precisely map the topography of the sea floor adjacent to and at the grounding line of the ice terminus while simultaneously mapping the ice terminus and surrounding terrain to create a complete 3D topographic model of the aerial and submarine environment. These data allow for

  19. Radial Velocity Observations and Light Curve Noise Modeling Confirm That Kepler-91b is a Giant Planet Orbiting a Giant Star

    CERN Document Server

    Barclay, Thomas; Huber, Daniel; Foreman-Mackey, Daniel; Cochran, William D; MacQueen, Phillip J; Rowe, Jason F; Quintana, Elisa V

    2014-01-01

    Kepler-91b is a rare example of a transiting hot Jupiter around a red giant star, providing the possibility to study the formation and composition of hot Jupiters under different conditions compared to main-sequence stars. However, the planetary nature of Kepler-91b, which was confirmed using phase-curve variations by Lillo-Box et al., was recently called into question based on a re-analysis of Kepler data. We have obtained ground-based radial velocity observations from the Hobby-Eberly Telescope and unambiguously confirm the planetary nature of Kepler-91b by simultaneously modeling the Kepler and radial velocity data. The star exhibits temporally correlated noise due to stellar granulation which we model as a Gaussian Process. We hypothesize that it is this noise component that led previous studies to suspect Kepler-91b to be a false positive. Our work confirms the conclusions presented by Lillo-Box et al. that Kepler-91b is a 0.73+/-0.13 Mjup planet orbiting a red giant star.

  20. RADIAL VELOCITY OBSERVATIONS AND LIGHT CURVE NOISE MODELING CONFIRM THAT KEPLER-91b IS A GIANT PLANET ORBITING A GIANT STAR

    Energy Technology Data Exchange (ETDEWEB)

    Barclay, Thomas; Huber, Daniel; Rowe, Jason F.; Quintana, Elisa V. [NASA Ames Research Center, M/S 244-30, Moffett Field, CA 94035 (United States); Endl, Michael; Cochran, William D.; MacQueen, Phillip J. [McDonald Observatory, The University of Texas at Austin, Austin, TX 78712 (United States); Foreman-Mackey, Daniel [New York University, Center for Cosmology and Particle Physics, New York, NY 10003 (United States)

    2015-02-10

    Kepler-91b is a rare example of a transiting hot Jupiter around a red giant star, providing the possibility to study the formation and composition of hot Jupiters under different conditions compared to main-sequence stars. However, the planetary nature of Kepler-91b, which was confirmed using phase-curve variations by Lillo-Box et al., was recently called into question based on a re-analysis of Kepler data. We have obtained ground-based radial velocity observations from the Hobby-Eberly Telescope and unambiguously confirm the planetary nature of Kepler-91b by simultaneously modeling the Kepler and radial velocity data. The star exhibits temporally correlated noise due to stellar granulation which we model as a Gaussian Process. We hypothesize that it is this noise component that led previous studies to suspect Kepler-91b to be a false positive. Our work confirms the conclusions presented by Lillo-Box et al. that Kepler-91b is a 0.73 ± 0.13 M {sub Jup} planet orbiting a red giant star.

  1. The Exoplanet Simple Orbit Fitting Toolbox (ExoSOFT): An Open-source Tool for Efficient Fitting of Astrometric and Radial Velocity Data

    Science.gov (United States)

    Mede, Kyle; Brandt, Timothy D.

    2017-03-01

    We present the Exoplanet Simple Orbit Fitting Toolbox (ExoSOFT), a new, open-source suite to fit the orbital elements of planetary or stellar-mass companions to any combination of radial velocity and astrometric data. To explore the parameter space of Keplerian models, ExoSOFT may be operated with its own multistage sampling approach or interfaced with third-party tools such as emcee. In addition, ExoSOFT is packaged with a collection of post-processing tools to analyze and summarize the results. Although only a few systems have been observed with both radial velocity and direct imaging techniques, this number will increase, thanks to upcoming spacecraft and ground-based surveys. Providing both forms of data enables simultaneous fitting that can help break degeneracies in the orbital elements that arise when only one data type is available. The dynamical mass estimates this approach can produce are important when investigating the formation mechanisms and subsequent evolution of substellar companions. ExoSOFT was verified through fitting to artificial data and was implemented using the Python and Cython programming languages; it is available for public download at https://github.com/kylemede/ExoSOFT under GNU General Public License v3.

  2. VizieR Online Data Catalog: LCES HIRES/Keck radial velocity Exoplanet Survey (Butler+, 2017)

    Science.gov (United States)

    Butler, R. P.; Vogt, S. S.; Laughlin, G.; Burt, J. A.; Rivera, E. J.; Tuomi, M.; Teske, J.; Arriagada, P.; Diaz, M.; Holden, B.; Keiser, S.

    2017-08-01

    We present 60949 precision radial velocities of 1624 stars obtained over the past 20 years from the Lick-Carnegie Exoplanet Survey Team (LCES) survey with the HIgh-Resolution Echelle Spectrometer (HIRES) spectrometer on the Keck I telescope. We tabulate a list of 357 significant periodic signals that are of constant period and phase, and not coincident in period and/or phase with stellar activity indices. For this survey, the HIRES spectrometer was configured to operate at a nominal spectral resolving power of R~60000 and wavelength range of 3700-8000Å. (4 data files).

  3. Toward accurate radial velocities with the fiber-fed GIRAFFE multi-object VLT spectrograph

    Science.gov (United States)

    Royer, Frederic; Blecha, Andre; North, Pierre; Simond, Gilles; Baratchart, Sebastien; Cayatte, Veronique; Chemin, Laurent; Palsa, Ralf

    2002-12-01

    We describe briefly the Data-Reduction of the VLT fiber-fed multi-object GIRAFFE spectrograph - part of the VLT FLAMES facility. We focus on specific features of GIRAFFE - the simultaneous wavelength calibration - and their impact on the data-reduction strategy. We describe the implementation of the global physical model and we compare the results obtained with the simulated, laboratory and preliminary data. We discuss the influence of critical parameters, the overall accuracy of the wavelength solution, and the stability and the robustness of the global model approach. We address the accuracy of radial velocity measurements illustrated by solar spectra obtained during the Preliminary Acceptance in Europe.

  4. General spherical anisotropic Jeans models of stellar kinematics: including proper motions and radial velocities

    CERN Document Server

    Cappellari, Michele

    2015-01-01

    Cappellari (2008) presented a flexible and efficient method to model the stellar kinematics of anisotropic axisymmetric and spherical stellar systems. The spherical formalism could be used to model the line-of-sight velocity second moments allowing for essentially arbitrary radial variation in the anisotropy and general luminous and total density profiles. Here we generalize the spherical formalism by providing the expressions for all three components of the projected second moments, including the two proper motion components. A reference implementation is now included in the public JAM package available at http://purl.org/cappellari/software

  5. Effective temperature and radial velocity of the small-amplitude Cepheid Polaris (alpha UMi) in 2015

    CERN Document Server

    Usenko, I A; Miroshnichenko, A S; Danford, S

    2016-01-01

    We present the results of an analysis of 21 spectra of alpha UMi (Polaris) obtained in September - December 2015. Frequency analysis shows an increase of the pulsation period up to 8.6 min in comparison to the 2007 observational set. The radial velocity amplitude comes to 4.16 km s^-1, and it approximately twice the one found in 2007. The average Teff = 6017 K, and it is close to the value determined for the 2001-2004 set. Therefore Polaris moves to the red edge of the Cepheid instability strip (CIS)

  6. VizieR Online Data Catalog: WASP-103b radial velocities and light curves (Gillon+, 2014)

    Science.gov (United States)

    Gillon, M.; Anderson, D. R.; Collier-Cameron, A.; Delrez, L.; Hellier, C.; Jehin, E.; Lendl, M.; Maxted, P. F. L.; Pepe, F.; Pollacco, D.; Queloz, D.; Segransan, D.; Smith, A. M. S.; Smalley, B.; Southworth, J.; Triaud, A. H. M. J.; Udry, S.; Van Grootel, V.; West, R. G.

    2014-01-01

    The host star WASP-103 (1SWASPJ163715.59+071100.0 = 2MASS16371556+0711000; V=12.1, K=10.8) was observed by the southern station of the WASP survey during the 2010, 2011, and 2012 observing seasons, covering the intervals 2010 May 15 to Aug. 16, 2011 Mar. 26 to Aug. 20, and 2012 Mar. 25 to Jun. 28. Files wasp.dat, trappist.dat, euler.dat contain the photometric time-series presented in the paper. File rv.dat contains the radial velocity time-series presented in the paper. (4 data files).

  7. Near-infrared metallicities, radial velocities, and spectral types for 447 nearby M dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Newton, Elisabeth R.; Charbonneau, David; Irwin, Jonathan; Berta-Thompson, Zachory K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Rojas-Ayala, Barbara [Centro de Astrofsica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Covey, Kevin [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Lloyd, James P., E-mail: enewton@cfa.harvard.edu [Department of Astronomy, Cornell University, 226 Space Sciences Building, Ithaca, NY 14853 (United States)

    2014-01-01

    We present metallicities, radial velocities, and near-infrared (NIR) spectral types for 447 M dwarfs determined from moderate resolution (R ≈ 2000) NIR spectra obtained with the NASA Infrared Telescope Facility (IRTF)/SpeX. These M dwarfs are primarily targets of the MEarth Survey, a transiting planet survey searching for super Earths around mid-to-late M dwarfs within 33 pc. We present NIR spectral types for each star and new spectral templates for the IRTF in the Y, J, H, and K-bands, created using M dwarfs with near-solar metallicities. We developed two spectroscopic distance calibrations that use NIR spectral type or an index based on the curvature of the K-band continuum. Our distance calibration has a scatter of 14%. We searched 27 NIR spectral lines and 10 spectral indices for metallicity sensitive features, taking into account correlated noise in our estimates of the errors on these parameters. We calibrated our relation using 36 M dwarfs in common proper pairs with an F-, G-, or K-type star of known metallicity. We validated the physical association of these pairs using proper motions, radial velocities, and spectroscopic distance estimates. Our resulting metallicity calibration uses the sodium doublet at 2.2 μm as the sole indicator for metallicity. It has an accuracy of 0.12 dex inferred from the scatter between the metallicities of the primaries and the estimated metallicities of the secondaries. Our relation is valid for NIR spectral types from M1V to M5V and for –1.0 dex < [Fe/H] < +0.35 dex. We present a new color-color metallicity relation using J – H and J – K colors that directly relates two observables: the distance from the M dwarf main sequence and equivalent width of the sodium line at 2.2 μm. We used radial velocities of M dwarf binaries, observations at different epochs, and comparison between our measurements and precisely measured radial velocities to demonstrate a 4 km s{sup –1} accuracy.

  8. Searching for Planets in the Hyades. I The Keck Radial Velocity Survey

    CERN Document Server

    Cochran, W D; Paulson, D B; Cochran, William D.; Hatzes, Artie P.; Paulson, Diane B.

    2002-01-01

    We describe a high-precision radial velocity search for jovian-mass companions to main sequence stars in the Hyades star cluster. The Hyades provides an extremely well controlled sample of stars of the same age, the same metallicity, and a common birth and early dynamical environment. This sample allows us to explore the dependence of the process of planet formation on only a single independent variable: the stellar mass. In this paper we describe the survey and summarize results for the first five years.

  9. Suppression of Fiber Modal Noise Induced Radial Velocity Errors for Bright Emission-Line Calibration Sources

    CERN Document Server

    Mahadevan, Suvrath; Ramsey, Lawrence; Venditti, Nick

    2014-01-01

    Modal noise in optical fibers imposes limits on the signal to noise and velocity precision achievable with the next generation of astronomical spectrographs. This is an increasingly pressing problem for precision radial velocity (RV) spectrographs in the near-infrared (NIR) and optical that require both high stability of the observed line profiles and high signal to noise. Many of these spectrographs plan to use highly coherent emission line calibration sources like laser frequency combs and Fabry-Perot etalons to achieve precision sufficient to detect terrestrial mass planets. These high precision calibration sources often use single mode fibers or highly coherent sources. Coupling light from single mode fibers to multi-mode fibers leads to only a very low number of modes being excited, thereby exacerbating the modal noise measured by the spectrograph. We present a commercial off-the-shelf (COTS) solution that significantly mitigates modal noise at all optical and NIR wavelengths, and which can be applied to...

  10. Searching for IMBHs in Galactic globular clusters through radial velocities of individual stars

    Science.gov (United States)

    Lanzoni, Barbara

    2016-02-01

    I present an overview of our ongoing project aimed at building a new generation of velocity dispersion profiles ad rotation curves for a representative sample of Galactic globular clusters, from the the radial velocity of hundreds of individual stars distributed at different distances from the cluster center. The innermost portion of the profiles will be used to constrain the possible presence of intermediate-mass black holes. The adopted methodology consists of combining spectroscopic observations acquired with three different instruments at the ESO-VLT: the adaptive-optics assisted, integral field unit (IFU) spectrograph SINFONI for the innermost and highly crowded cluster cores, the multi-IFU spectrograph KMOS for the intermediate regions, and the multi-fiber instrument FLAMES/GIRAFFE-MEDUSA for the outskirts. The case of NGC 6388, representing the pilot project that motivated the entire program, is described in some details.

  11. Astrophysical Sources of Statistical Uncertainty in Precision Radial Velocities and Their Approximations

    Science.gov (United States)

    Beatty, Thomas G.; Gaudi, B. Scott

    2015-12-01

    We investigate various astrophysical contributions to the statistical uncertainty of precision radial velocity measurements of stellar spectra. We first analytically determine the intrinsic uncertainty in centroiding isolated spectral lines broadened by Gaussian, Lorentzian, Voigt, and rotational profiles, finding that for all cases and assuming weak lines, the uncertainty in the line centroid is σV ≈ C\\Theta3/2/(WI1/20), where Θ is the full-width at half-maximum of the line, W is the equivalent width, and I0 is the continuum signal-to-noise ratio, with C a constant of order unity that depends on the specific line profile. We use this result to motivate approximate analytic expressions to the total radial velocity uncertainty for a stellar spectrum with a given photon noise, resolution, wavelength, effective temperature, surface gravity, metallicity, macroturbulence, and stellar rotation. We use these relations to determine the dominant contributions to the statistical uncertainties in precision radial velocity measurements as a function of effective temperature and mass for main-sequence stars. For stars more massive than ~1.1 Msolar we find that stellar rotation dominates the velocity uncertainties for moderate and high-resolution spectra (R gsim 30,000). For less-massive stars, a variety of sources contribute depending on the spectral resolution and wavelength, with photon noise due to decreasing bolometric luminosity generally becoming increasingly important for low-mass stars at fixed exposure time and distance. In most cases, resolutions greater than 60,000 provide little benefit in terms of statistical precision, although higher resolutions would likely allow for better control of systematic uncertainties. We find that the spectra of cooler stars and stars with higher metallicity are intrinsically richer in velocity information, as expected. We determine the optimal wavelength range for stars of various spectral types, finding that the optimal region

  12. The Joker: A Custom Monte Carlo Sampler for Binary-star and Exoplanet Radial Velocity Data

    Science.gov (United States)

    Price-Whelan, Adrian M.; Hogg, David W.; Foreman-Mackey, Daniel; Rix, Hans-Walter

    2017-03-01

    Given sparse or low-quality radial velocity measurements of a star, there are often many qualitatively different stellar or exoplanet companion orbit models that are consistent with the data. The consequent multimodality of the likelihood function leads to extremely challenging search, optimization, and Markov chain Monte Carlo (MCMC) posterior sampling over the orbital parameters. Here we create a custom Monte Carlo sampler for sparse or noisy radial velocity measurements of two-body systems that can produce posterior samples for orbital parameters even when the likelihood function is poorly behaved. The six standard orbital parameters for a binary system can be split into four nonlinear parameters (period, eccentricity, argument of pericenter, phase) and two linear parameters (velocity amplitude, barycenter velocity). We capitalize on this by building a sampling method in which we densely sample the prior probability density function (pdf) in the nonlinear parameters and perform rejection sampling using a likelihood function marginalized over the linear parameters. With sparse or uninformative data, the sampling obtained by this rejection sampling is generally multimodal and dense. With informative data, the sampling becomes effectively unimodal but too sparse: in these cases we follow the rejection sampling with standard MCMC. The method produces correct samplings in orbital parameters for data that include as few as three epochs. The Joker can therefore be used to produce proper samplings of multimodal pdfs, which are still informative and can be used in hierarchical (population) modeling. We give some examples that show how the posterior pdf depends sensitively on the number and time coverage of the observations and their uncertainties.

  13. The pair-wise velocity dispersion of galaxies effects of non radial motions

    CERN Document Server

    Popolo, A D

    2001-01-01

    I discuss the effect of non-radial motions on the small-scale pairwise peculiar velocity dispersions of galaxies (PVD) in a CDM model. I calculate the PVD for the SCDM model by means of the refined cosmic virial theorem (CVT) (Suto & Jing 1997) and taking account of non-radial motions by means of Del Popolo & Gambera (1998) model. I compare the results of the present model with the data from Davis & Peebles (1983), the IRAS value at 1 h{-1} Mpc of Fisher et al. (1993) and Marzke et al. (1995). I show that while the SCDM model disagrees with the observed values, as pointed out by several authors (Peebles 1976, 1980; Davis & Peebles 1983; Mo et. al 1993; Jing et al. 1998), taking account of non-radial motions produce smaller values for the PVD. At r <=1 h^{-1} Mpc the result is in agreement with Bartlett & Blanchard (1996) (hereafter BB96). At the light of this last paper, the result may be also read as a strong dependence of the CVT prediction on the model chosen to describe the mass dis...

  14. The Milky Way's halo in 6D: Gaia's Radial Velocity Spectrometer performance

    CERN Document Server

    Seabroke, George; Katz, David; Sartoretti, Paola; Panuzzo, Pasquale; Marchal, Olivier; Gueguen, Alain; Benson, Kevin; Dolding, Chris; Huckle, Howard; Smith, Mike; Baker, Steve

    2016-01-01

    Gaia's Radial Velocity Spectrometer (RVS) has been operating in routine phase for over one year since initial commissioning. RVS continues to work well but the higher than expected levels of straylight reduce the limiting magnitude. The end-of-mission radial-velocity (RV) performance requirement for G2V stars was 15 km/s at V = 16.5 mag. Instead, 15 km/s precision is achieved at 15 < V < 16 mag, consistent with simulations that predict a loss of 1.4 mag. Simulations also suggest that changes to Gaia's onboard software could recover ~0.14 mag of this loss. Consequently Gaia's onboard software was upgraded in April 2015. The status of this new commissioning period is presented, as well as the latest scientific performance of the on-ground processing of RVS spectra. We illustrate the implications of the RVS limiting magnitude on Gaia's view of the Milky Way's halo in 6D using the Gaia Universe Model Snapshot (GUMS).

  15. SOAP. A tool for the fast computation of photometry and radial velocity induced by stellar spots

    Science.gov (United States)

    Boisse, I.; Bonfils, X.; Santos, N. C.

    2012-09-01

    We define and put at the disposal of the community SOAP, Spot Oscillation And Planet, a software tool that simulates the effect of stellar spots and plages on radial velocimetry and photometry. This paper describes the tool release and provides instructions for its use. We present detailed tests with previous computations and real data to assess the code's performance and to validate its suitability. We characterize the variations of the radial velocity, line bisector, and photometric amplitude as a function of the main variables: projected stellar rotational velocity, filling factor of the spot, resolution of the spectrograph, linear limb-darkening coefficient, latitude of the spot, and inclination of the star. Finally, we model the spot distributions on the active stars HD 166435, TW Hya and HD 189733, which reproduce the observations. We show that the software is remarkably fast, allowing several evolutions in its capabilities that could be performed to study the next challenges in the exoplanetary field connected with the stellar variability. The tool is available at http://www.astro.up.pt/soap

  16. Planets around stars in young nearby associations *** radial Velocity searches: a feasibility study, and first results

    CERN Document Server

    Lagrange, A -M; Chauvin, G; Sterzik, M; Galland, F; Curto, G Lo; Rameau, J; Sosnowska, D

    2013-01-01

    Stars in young nearby associations are the only targets allowing giant planet searches at all separations in the near future, by coupling indirect techniques such as radial velocity and deep imaging. These stars are first priorities targets for the forthcoming planets imagers on 10-m class telescopes. Young stars rotate more rapidly and are more active than their older counterparts. Both effects can limit the capability to detect planets using RV. We wish to explore the planet detection capabilities of a representative sample of stars in close and young associations with radial velocity data and explore the complementarity between this technique and direct imaging. We observed 26 such targets with spectral types from A to K and ages from 8 to 300 Myr with HARPS. We compute the detection limits. We also attempt to improve the detection limits in a few cases by correcting for the stellar activity. Our A-type stars RV show high frequency variations due to pulsations, while our F-K stars clearly show activity wit...

  17. Detection of radial velocity shifts due to black hole binaries near merger

    CERN Document Server

    McKernan, B

    2015-01-01

    The barycenter of a massive black hole binary will lie outside the event horizon of the primary black hole for modest values of mass ratio and binary separation. Analagous to radial velocity shifts in stellar emission lines caused by the tug of planets, the radial velocity of the primary black hole around the barycenter can leave a tell-tale oscillation in the broad component of Fe K$\\alpha$ emission from accreting gas. Near-future X-ray telescopes such as Astro-H and Athena will have the energy resolution ($\\delta E/E \\lesssim 10^{-3}$) to search nearby active galactic nuclei (AGN) for the presence of binaries with mass ratios $q \\gtrsim 0.01$, separated by several hundred gravitational radii. The general-relativistic and Lense-Thirring precession of the periapse of the secondary orbit imprints a detectable modulation on the oscillations. The lowest mass binaries in AGN will oscillate many times within typical X-ray exposures, leading to a broadening of the line wings and an over-estimate of black hole spin ...

  18. VizieR Online Data Catalog: Radial velocities of TYC 4110-01037-1 (Wisniewski+, 2012)

    Science.gov (United States)

    Wisniewski, J. P.; Ge, J.; Crepp, J. R.; de, Lee N.; Eastman, J.; Esposito, M.; Fleming, S. W.; Gaudi, B. S.; Ghezzi, L.; Gonzalez Hernandez, J. I.; Lee, B. L.; Stassun, K. G.; Agol, E.; Prieto, C. A.; Barnes, R.; Bizyaev, D.; Cargile, P.; Chang, L.; da Costa, L. N.; Porto de Mello, G. F.; Femenia, B.; Ferreira, L. D.; Gary, B.; Hebb, L.; Holtzman, J.; Liu, J.; Ma, B.; Mack, C. E.; Mahadevan, S.; Maia, M. A. G.; Nguyen, D. C.; Ogando, R. L. C.; Oravetz, D. J.; Paegert, M.; Pan, K.; Pepper, J.; Rebolo, R.; Santiago, B.; Schneider, D. P.; Shelden, A. C.; Simmons, A.; Tofflemire, B. M.; Wan, X.; Wang, J.; Zhao, B.

    2013-06-01

    The Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS), one of the three surveys being executed during the Sloan Digital Sky Survey (SDSS) III (Eisenstein et al., 2011AJ....142...72E), is a four-year program which is monitoring the radial velocities of ~3300 V=7.6-12 FGK-type dwarfs and subgiants. Our primary RV observations of TYC 4110-01037-1 were obtained during the first two years of the SDSS-III MARVELS survey, which uses a dispersed fixed-delay interferometer on the SDSS 2.5m telescope. A total of 32 observations were obtained over the course of ~2 years. Each 50minute observation yielded two fringing spectra from the interferometer spanning the wavelength regime ~500-570nm with R~12000. Supporting RV observations were obtained with the 3.6m Telescopio Nazionale Galileo (TNG) using its SARG spectrograph. The 0.8"*5.3" slit provided R~57000 spectroscopy between 462-792nm. (1 data file).

  19. Searching for Earth-mass planets around $\\alpha$ Centauri: precise radial velocities from contaminated spectra

    CERN Document Server

    Bergmann, Christoph; Hearnshaw, John B; Wittenmyer, Robert A; Wright, Duncan J

    2014-01-01

    This work is part of an ongoing project which aims to detect terrestrial planets in our neighbouring star system $\\alpha$ Centauri using the Doppler method. Owing to the small angular separation between the two components of the $\\alpha$ Cen AB binary system, the observations will to some extent be contaminated with light coming from the other star. We are accurately determining the amount of contamination for every observation by measuring the relative strengths of the H-$\\alpha$ and NaD lines. Furthermore, we have developed a modified version of a well established Doppler code that is modelling the observations using two stellar templates simultaneously. With this method we can significantly reduce the scatter of the radial velocity measurements due to spectral cross-contamination and hence increase our chances of detecting the tiny signature caused by potential Earth-mass planets. After correcting for the contamination we achieve radial velocity precision of $\\sim 2.5\\,\\mathrm{m\\,s^{-1}}$ for a given night...

  20. Origins of Solar Systems: Removing Activity-Related Radial Velocity Noise to Improve Extrasolar Planet Searches

    Science.gov (United States)

    Saar, Steven; Lindstrom, David (Technical Monitor)

    2003-01-01

    We have continued the super high resolution (R is approximately 200,000), high S/N (> 300) echelle study of joint line bisector and radial velocity variations using the McDonald 2-D coude. A long observing run in October 2002 was quite successful (8 clear nights). We now have close to three years of data, which begins to sample a good fraction of the magnetic cycle timescales for some of our targets (e.g., K Ceti; P(sub cyc)=5.6 yrs). This will be very helpful in unraveling the complex relationships between plage and v(sub r), changes which we have uncovered. A preliminary analysis of the limited data in hand, and find some tantalizing evidence for correlations between median line bisector displacement and radial velocity v(sub r). The correlation appears to be specific to the particular star being considered, probably since it is a function of both spectral type and rotation rate. Additional information regarding progress on the grant is included.

  1. WIYN Open Cluster Study XXXII: Stellar Radial Velocities in the Old Open Cluster NGC 188

    CERN Document Server

    Geller, Aaron M; Harris, Hugh C; McClure, Robert D

    2015-01-01

    (Abridged) We present the results of our ongoing radial-velocity (RV) survey of the old (7 Gyr) open cluster NGC 188. Our WIYN 3.5m data set spans a time baseline of 11 years, a magnitude range of 12<=V<=16.5 (1.18-0.94 MSun), and a 1 deg. diameter region on the sky. With the addition of a Dominion Astrophysical Observatory (DAO) data set we extend our bright limit to V = 10.8 and, for some stars, extend our time baseline to 35 years. Our magnitude limits include solar-mass main-sequence stars, subgiants, giants, and blue stragglers (BSs), and our spatial coverage extends radially to 17 pc (~13 core radii). For the WIYN data we find a measurement precision of 0.4 km/s for narrow-lined stars. We have measured RVs for 1046 stars in the direction of NGC 188, finding 473 to be likely cluster members. We detect 124 velocity-variable cluster members, all of which are likely to be dynamically hard-binary stars. Using our single member stars, we find an average cluster RV of -42.36 +/- 0.04 km/s. We use our pre...

  2. Twenty Years of Precise Radial Velocities at Keck and Lick Observatories

    CERN Document Server

    Wright, Jason T

    2016-01-01

    The precise radial velocity survey at Keck Observatory began over 20 years ago. Its survey of thousands of stars now has the time baseline to be sensitive to planets with decade-long orbits, including Jupiter analogs. I present several newly-finished orbital solutions for long-period giant planets. Although hot Jupiters are generally "lonely" (i.e. they are not part of multiplanet systems), those that are not appear to often have giant companions at 5 AU or beyond. I present two of the highest period- ratios among planets in a two-planet system, and some of the longest orbital periods ever measured for exoplanets. In many cases, combining Keck radial velocities from those from other long-term surveys at Lick Observatory, McDonald Observatory, HARPS, and, of course, OHP spectrographs, produces superior orbital fits, constraining both period and eccentricity better than could be possible with any single set alone. Stellar magnetic activity cycles can masquerade as long-period planets. In most cases this effect ...

  3. A RAVE Investigation on Galactic open Clusters I. Radial velocities and metallicities

    CERN Document Server

    Conrad, C; Kharchenko, N V; Piskunov, A E; Schilbach, E; Röser, S; Boeche, C; Kordopatis, G; Siebert, A; Williams, M; Munari, U; Matijevič, G; Grebel, E K; Zwitter, T; de Jong, R S; Steinmetz, M; Gilmore, G; Seabroke, G; Freeman, K; Navarro, J F; Parker, Q; Reid, W; Watson, F; Gibson, B K; Bienaymé, O; Wyse, R; Bland-Hawthorn, J; Siviero, A

    2013-01-01

    Context. Galactic open clusters (OCs) mainly belong to the young stellar population in the Milky Way disk, but are there groups and complexes of OCs that possibly define an additional level in hierarchical star formation? Current compilations are too incomplete to address this question, especially regarding radial velocities (RVs) and metallicities ($[M/H]$). Aims. Here we provide and discuss newly obtained RV and $[M/H]$ data, which will enable us to reinvestigate potential groupings of open clusters and associations. Methods.We extracted additional RVs and $[M/H]$ from the RAdial Velocity Experiment (RAVE) via a cross-match with the Catalogue of Stars in Open Cluster Areas (CSOCA). For the identified OCs in RAVE we derived RV and $[M/H]$ from a cleaned working sample and compared the results with previous findings. Results. Although our RAVE sample does not show the same accuracy as the entire survey, we were able to derive reliable RV for 110 Galactic open clusters. For 37 OCs we publish RV for the first t...

  4. Precision near-infrared radial velocity instrumentation I: Absorption Gas Cells

    CERN Document Server

    Plavchan, Peter P; White, Russel; Gao, Peter; Davison, Cassy; Mills, Sean; Beichman, Chas; Brinkworth, Carolyn; Johnson, John Asher; Bottom, Michael; Ciardi, David; Wallace, J Kent; Mennesson, Bertrand; von Braun, Kaspar; Vasisht, Gautum; Prato, LIsa; Kane, Stephen; Tanner, Angelle; Walp, Bernie; Crawford, Sam; Lin, Sean

    2013-01-01

    We have built and commissioned gas absorption cells for precision spectroscopic radial velocity measurements in the near-infrared in the H and K bands. We describe the construction and installation of three such cells filled with 13CH4, 12CH3D, and 14NH3 for the CSHELL spectrograph at the NASA Infrared Telescope Facility (IRTF). We have obtained their high-resolution laboratory Fourier Transform spectra, which can have other practical uses. We summarize the practical details involved in the construction of the three cells, and the thermal and mechanical control. In all cases, the construction of the cells is very affordable. We are carrying out a pilot survey with the 13CH4 methane gas cell on the CSHELL spectrograph at the IRTF to detect exoplanets around low mass and young stars. We discuss the current status of our survey, with the aim of photon-noise limited radial velocity precision. For adequately bright targets, we are able to probe a noise floor of 7 m/s with the gas cell with CSHELL at cassegrain foc...

  5. Theoretical and Experimental Study of Radial Velocity Generation for Extending Bandwidth of Magnetohydrodynamic Angular Rate Sensor at Low Frequency

    Directory of Open Access Journals (Sweden)

    Yue Ji

    2015-12-01

    Full Text Available The magnetohydrodynamics angular rate sensor (MHD ARS has received much attention for its ultra-low noise in ultra-broad bandwidth and its impact resistance in harsh environments; however, its poor performance at low frequency hinders its work in long time duration. The paper presents a modified MHD ARS combining Coriolis with MHD effect to extend the measurement scope throughout the whole bandwidth, in which an appropriate radial flow velocity should be provided to satisfy simplified model of the modified MHD ARS. A method that can generate radial velocity by an MHD pump in MHD ARS is proposed. A device is designed to study the radial flow velocity generated by the MHD pump. The influence of structure and physical parameters are studied by numerical simulation and experiment of the device. The analytic expression of the velocity generated by the energized current drawn from simulation and experiment are consistent, which demonstrates the effectiveness of the method generating radial velocity. The study can be applied to generate and control radial velocity in modified MHD ARS, which is essential for the two effects combination throughout the whole bandwidth.

  6. Theoretical and Experimental Study of Radial Velocity Generation for Extending Bandwidth of Magnetohydrodynamic Angular Rate Sensor at Low Frequency.

    Science.gov (United States)

    Ji, Yue; Li, Xingfei; Wu, Tengfei; Chen, Cheng

    2015-12-15

    The magnetohydrodynamics angular rate sensor (MHD ARS) has received much attention for its ultra-low noise in ultra-broad bandwidth and its impact resistance in harsh environments; however, its poor performance at low frequency hinders its work in long time duration. The paper presents a modified MHD ARS combining Coriolis with MHD effect to extend the measurement scope throughout the whole bandwidth, in which an appropriate radial flow velocity should be provided to satisfy simplified model of the modified MHD ARS. A method that can generate radial velocity by an MHD pump in MHD ARS is proposed. A device is designed to study the radial flow velocity generated by the MHD pump. The influence of structure and physical parameters are studied by numerical simulation and experiment of the device. The analytic expression of the velocity generated by the energized current drawn from simulation and experiment are consistent, which demonstrates the effectiveness of the method generating radial velocity. The study can be applied to generate and control radial velocity in modified MHD ARS, which is essential for the two effects combination throughout the whole bandwidth.

  7. Theoretical and Experimental Study of Radial Velocity Generation for Extending Bandwidth of Magnetohydrodynamic Angular Rate Sensor at Low Frequency

    Science.gov (United States)

    Ji, Yue; Li, Xingfei; Wu, Tengfei; Chen, Cheng

    2015-01-01

    The magnetohydrodynamics angular rate sensor (MHD ARS) has received much attention for its ultra-low noise in ultra-broad bandwidth and its impact resistance in harsh environments; however, its poor performance at low frequency hinders its work in long time duration. The paper presents a modified MHD ARS combining Coriolis with MHD effect to extend the measurement scope throughout the whole bandwidth, in which an appropriate radial flow velocity should be provided to satisfy simplified model of the modified MHD ARS. A method that can generate radial velocity by an MHD pump in MHD ARS is proposed. A device is designed to study the radial flow velocity generated by the MHD pump. The influence of structure and physical parameters are studied by numerical simulation and experiment of the device. The analytic expression of the velocity generated by the energized current drawn from simulation and experiment are consistent, which demonstrates the effectiveness of the method generating radial velocity. The study can be applied to generate and control radial velocity in modified MHD ARS, which is essential for the two effects combination throughout the whole bandwidth. PMID:26694393

  8. Sensitivities of surface wave velocities to the medium parameters in a radially anisotropic spherical Earth and inversion strategies

    Directory of Open Access Journals (Sweden)

    Sankar N. Bhattacharya

    2015-11-01

    Full Text Available Sensitivity kernels or partial derivatives of phase velocity (c and group velocity (U with respect to medium parameters are useful to interpret a given set of observed surface wave velocity data. In addition to phase velocities, group velocities are also being observed to find the radial anisotropy of the crust and mantle. However, sensitivities of group velocity for a radially anisotropic Earth have rarely been studied. Here we show sensitivities of group velocity along with those of phase velocity to the medium parameters VSV, VSH , VPV, VPH , h and density in a radially anisotropic spherical Earth. The peak sensitivities for U are generally twice of those for c; thus U is more efficient than c to explore anisotropic nature of the medium. Love waves mainly depends on VSH while Rayleigh waves is nearly independent of VSH . The sensitivities show that there are trade-offs among these parameters during inversion and there is a need to reduce the number of parameters to be evaluated independently. It is suggested to use a nonlinear inversion jointly for Rayleigh and Love waves; in such a nonlinear inversion best solutions are obtained among the model parameters within prescribed limits for each parameter. We first choose VSH, VSV and VPH within their corresponding limits; VPV and h can be evaluated from empirical relations among the parameters. The density has small effect on surface wave velocities and it can be considered from other studies or from empirical relation of density to average P-wave velocity.

  9. Radial Velocities and Kinematic Membership in the Open Cluster NGC 3114

    Science.gov (United States)

    González, Jorge Federico; Lapasset, Emilio

    2001-05-01

    Echelle spectroscopic observations for 30 bright stars in the field of the sparse open cluster NGC 3114 are presented. The sample includes main-sequence stars, yellow and red giants, and blue straggler candidates. Radial velocities are derived by cross-correlations using high signal-to-noise ratio standard spectra as templates. The cluster mean velocity is well defined from eight giants and several main-sequence stars whose average is =-3.52+/-0.25 km s-1. The membership probabilities of the observed stars are computed on the basis of the velocity distributions of the cluster and field stars, and the expected percentage of contamination at each position. We classified 19 cluster members and 10 nonmembers; the remaining star is a known spectroscopic binary for which no membership probability was assigned. Among the members, there is a bright yellow giant, seven red giants, and four blue straggler candidates, although they should be considered as turn-off stars. The location of two of them in the color-magnitude diagram (slightly blueward of the turn-off) can be explained by their low rotational velocities. No velocity variations were detected in the 16 stars measured more than once, which indicates that NGC 3114 possess an abnormally low binary frequency. From spectral types of cluster members, a distance modulus (V-Mv)=9.8+/-0.2 mag and a reddening E(B-V)=0.07+/-0.01 mag are derived. The cluster age is estimated to be 1.6×108 yr. The observations presented here were obtained at the Complejo Astronómico El Leoncito (CASLEO), which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina (CONICET) and the National Universities of La Plata, Córdoba and San Juan.

  10. Softverski model estimatora radijalne brzine ciljeva / Software model of a radial velocity estimator

    Directory of Open Access Journals (Sweden)

    Dejan S. Ivković

    2010-04-01

    Full Text Available U radu je softverski modelovan novi blok u delu za obradu signala softverskog radarskog prijemnika, koji je nazvan estimator radijalne brzine. Detaljno je opisan način procene Doplerove frekvencije na osnovu MUSIC algoritma i ukratko prikazan način rada pri merenju. Svi parametri pri merenju klatera i detekcije simuliranih i realnih ciljeva dati su tabelarno, a rezultati grafički. Na osnovu analize prikazanih rezultata može se zaključiti da se pomoću projektovanog estimatora radijalne brzine može precizno proceniti Doplerov pomak u reflektovanom signalu od pokretnog cilja, a samim tim može se precizno odrediti njegova brzina. / In all analyses the MUSIC method has given better results than the FFT method. The MUSIC method proved to be better at estimation precision as well as at resolving two adjacent Doppler frequencies. On the basis of the obtained results, the designed estimator of radial velocity can be said to estimate Doppler frequency in the reflected signal from a moving target precisely, and, consequently, the target velocity. It is thus possible to improve the performances of the current radar as far as a precise estimation of velocity of detected moving targets is concerned.

  11. The M4 Core Project with HST - IV. Internal Kinematics from Accurate Radial Velocities of 2771 Cluster Members

    CERN Document Server

    Malavolta, L; Bedin, L R; Sneden, C; Nascimbeni, V; Sommariva, V

    2015-01-01

    We present a detailed study of the internal kinematics of the Galactic Globular Cluster M 4 (NGC 6121), by deriving the radial velocities from 7250 spectra for 2771 stars distributed from the upper part of the Red Giant Branch down to the Main Sequence. We describe new approaches to determine the wavelength solution from day-time calibrations and to determine the radial velocity drifts that can occur between calibration and science observations when observing with the GIRAFFE spectrograph at VLT. Two techniques to determine the radial velocity are compared, after a qualitative description of their advantages with respect to other commonly used algorithm, and a new approach to remove the sky contribution from the spectra obtained with fibre-fed spectrograph and further improve the radial velocity precision is presented. The average radial velocity of the cluster is $\\langle v \\rangle = 71.08 \\pm 0.08$ km s$^{-1}$ with an average dispersion of $\\mu_{v_c} = 3.97$ km s$^{-1}$. Using the same dataset and the same ...

  12. Analytical determination of orbital elements using Fourier analysis. I. The radial velocity case

    Science.gov (United States)

    Delisle, J.-B.; Ségransan, D.; Buchschacher, N.; Alesina, F.

    2016-05-01

    We describe an analytical method for computing the orbital parameters of a planet from the periodogram of a radial velocity signal. The method is very efficient and provides a good approximation of the orbital parameters. The accuracy is mainly limited by the accuracy of the computation of the Fourier decomposition of the signal which is sensitive to sampling and noise. Our method is complementary with more accurate (and more expensive in computer time) numerical algorithms (e.g. Levenberg-Marquardt, Markov chain Monte Carlo, genetic algorithms). Indeed, the analytical approximation can be used as an initial condition to accelerate the convergence of these numerical methods. Our method can be applied iteratively to search for multiple planets in the same system.

  13. An efficient, compact, and versatile fiber double scrambler for high precision radial velocity instruments

    CERN Document Server

    Halverson, Samuel; Mahadevan, Suvrath; Ramsey, Lawrence; Levi, Eric; Schwab, Christian; Hearty, Fred; MacDonald, Nick

    2015-01-01

    We present the design and test results of a compact optical fiber double-scrambler for high-resolution Doppler radial velocity instruments. This device consists of a single optic: a high-index $n$$\\sim$2 ball lens that exchanges the near and far fields between two fibers. When used in conjunction with octagonal fibers, this device yields very high scrambling gains and greatly desensitizes the fiber output from any input illumination variations, thereby stabilizing the instrument profile of the spectrograph and improving the Doppler measurement precision. The system is also highly insensitive to input pupil variations, isolating the spectrograph from telescope illumination variations and seeing changes. By selecting the appropriate glass and lens diameter the highest efficiency is achieved when the fibers are practically in contact with the lens surface, greatly simplifying the alignment process when compared to classical double-scrambler systems. This prototype double-scrambler has demonstrated significant pe...

  14. Radial-Velocity Fitting Challenge. II. First results of the analysis of the data set

    CERN Document Server

    Dumusque, X; Damasso, M; Diaz, R; Gregory, P C; Hara, N C; Hatzes, A; Rajpaul, V; Tuomi, M; Aigrain, S; Anglada-Escude, G; Bonomo, A S; Boue, G; Dauvergne, F; Frustagli, G; Giacobbe, P; Haywood, R D; Jones, H R A; Pinamonti, M; Poretti, E; Rainer, M; Segransan, D; Sozzetti, A; Udry, S

    2016-01-01

    Radial-velocity (RV) signals induce RV variations an order of magnitude larger than the signal created by the orbit of Earth-twins, thus preventing their detection. The goal of this paper is to compare the efficiency of the different methods used to deal with stellar signals to recover extremely low-mass planets despite. However, because observed RV variations at the m/s precision level or below is a combination of signals induced by unresolved orbiting planets, by the star, and by the instrument, performing such a comparison using real data is extremely challenging. To circumvent this problem, we generated simulated RV measurements including realistic stellar and planetary signals. Different teams analyzed blindly those simulated RV measurements, using their own method to recover planetary signals despite stellar RV signals. By comparing the results obtained by the different teams with the planetary and stellar parameters used to generate the simulated RVs, it is therefore possible to compare the efficiency ...

  15. Red Optical Planet Survey: A radial velocity search for low mass M dwarf planets

    Science.gov (United States)

    Barnes, J. R.; Jenkins, J. S.; Jones, H. R. A.; Rojo, P.; Arriagada, P.; Jordán, A.; Minniti, D.; Tuomi, M.; Jeffers, S. V.; Pinfield, D.

    2013-04-01

    We present radial velocity results from our Red Optical Planet Survey (ROPS), aimed at detecting low-mass planets orbiting mid-late M dwarfs. The ˜10 ms-1 precision achieved over 2 consecutive nights with the MIKE spectrograph at Magellan Clay is also found on week long timescales with UVES at VLT. Since we find that UVES is expected to attain photon limited precision of order 2 ms-1 using our novel deconvolution technique, we are limited only by the (≤10 ms-1) stability of atmospheric lines. Rocky planet frequencies of η⊕ = 0.3-0.7 lead us to expect high planet yields, enabling determination of η⊕ for the uncharted mid-late M dwarfs with modest surveys.

  16. HD 101065, the Most Peculiar Star: First Results from Precise Radial Velocity Study

    Indian Academy of Sciences (India)

    D. E. Mkrtichian; A. P. Hatzes

    2005-06-01

    In this paper we discuss the prospects for asteroseismology with spatial resolution and motivate studies of the most chemically peculiar roAp star HD 101065. We present the first results from a high-precision radial velocity (RV) study of HD 101065 based on data spanning four nights that were acquired using the HARPS echelle-spectrometer at the ESO 3.6 m telescope. The analysis of individual nights showed the amplitude and phase modulation of the dominant mode. The analysis of the whole data set showed the presence of multi-periodic oscillations with two groups of equally-spaced modes. We find = 65.2 Hz and = 7.3 Hz for the large and the small spacing, respectively. HD 101065 is the only roAp star to show the existence of two groups of = 0, 2 and = 1, 3 excited modes.

  17. A comprehensive radial velocity error budget for next generation Doppler spectrometers

    CERN Document Server

    Halverson, Samuel; Mahadevan, Suvrath; Roy, Arpita; Bender, Chad; Stefánsson, Guðmundur Kári; Monson, Andrew; Levi, Eric; Hearty, Fred; Blake, Cullen; McElwain, Michael; Schwab, Christian; Ramsey, Lawrence; Wright, Jason; Wang, Sharon; Gong, Qian; Robertson, Paul

    2016-01-01

    We describe a detailed radial velocity error budget for the NASA-NSF Extreme Precision Doppler Spectrometer instrument concept NEID (NN-explore Exoplanet Investigations with Doppler spectroscopy). Such an instrument performance budget is a necessity for both identifying the variety of noise sources currently limiting Doppler measurements, and estimating the achievable performance of next generation exoplanet hunting Doppler spectrometers. For these instruments, no single source of instrumental error is expected to set the overall measurement floor. Rather, the overall instrumental measurement precision is set by the contribution of many individual error sources. We use a combination of numerical simulations, educated estimates based on published materials, extrapolations of physical models, results from laboratory measurements of spectroscopic subsystems, and informed upper limits for a variety of error sources to identify likely sources of systematic error and construct our global instrument performance erro...

  18. A WEAVE Radial Velocity Survey to Unravel the Nature of the Milky Way's Spiral Arms

    Science.gov (United States)

    Monguió, M.; Figueras, F.; Grosbøl, P.

    2016-10-01

    The nature of the spiral arms of our Milky Way Galaxy is still a matter of debate. Different theories have been suggested (density waves, swing amplification, invariant manifolds...) which impose several constraints on the observables. For the first time it will be possible to disentangle these theories by combining Gaia and WEAVE data. Great advantage comes from the fact that WEAVE is in the Northern Hemisphere, that is with good coverage towards the galactic anticenter. We plan to quantify the kinematic perturbation induced by the Perseus spiral arm through radial velocity measurements. We show how, for the first time, we have detected the stellar overdensity associated with the Perseus arm using a Strömgren photometric survey with the Wide Field Camera on the Isaac Newton Telescope. This survey has allowed us to perform first tests on WEAVE capabilities.

  19. Retrieval of Precise Radial Velocities from Near-Infrared High Resolution Spectra of Low Mass Stars

    CERN Document Server

    Gao, Peter; Gagné, Jonathan; Furlan, Elise; Bottom, Michael; Anglada-Escudé, Guillem; White, Russel; Davison, Cassy; Beichman, Charles; Brinkworth, Carolyn; Johnson, John; Ciardi, David; Wallace, James; Mennesson, Bertrand; von Braun, Kaspar; Vasisht, Gautam; Prato, Lisa; Kane, Stephen; Tanner, Angelle; Crawford, Timothy; Latham, David; Rougeot, Raphaël; Geneser, Claire; Catanzarite, Joseph

    2016-01-01

    Given that low-mass stars have intrinsically low luminosities at optical wavelengths and a propensity for stellar activity, it is advantageous for radial velocity (RV) surveys of these objects to use near-infrared (NIR) wavelengths. In this work we describe and test a novel RV extraction pipeline dedicated to retrieving RVs from low mass stars using NIR spectra taken by the CSHELL spectrograph at the NASA Infrared Telescope Facility, where a methane isotopologue gas cell is used for wavelength calibration. The pipeline minimizes the residuals between the observations and a spectral model composed of templates for the target star, the gas cell, and atmospheric telluric absorption; models of the line spread function, continuum curvature, and sinusoidal fringing; and a parameterization of the wavelength solution. The stellar template is derived iteratively from the science observations themselves without a need for separate observations dedicated to retrieving it. Despite limitations from CSHELL's narrow wavelen...

  20. On the Determination of Transiting Planet Properties from Light and Radial Velocity Curves

    Science.gov (United States)

    Southworth, John

    2017-02-01

    A recent publication has suggested a method to determine the masses and radii of the components of an eclipsing system using only a light curve and radial velocities of one component. If true, this would have immediate impact in expediting the study of transiting extrasolar planet and brown dwarf systems. The method is intended for situations where the mass ratio is significantly different from zero, but implicitly also requires the assumption that the mass ratio is negligible. We investigate both cases, finding that when the mass ratio is significant the method is mathematically identical to existing approaches, and when the mass ratio is negligible the equations become undefined. We therefore conclude that the method cannot be used to measure the physical properties of such systems from observations alone.

  1. Sensitivity bias in the mass-radius distribution from Transit Timing Variations and Radial Velocity measurements

    CERN Document Server

    Steffen, Jason H

    2015-01-01

    Motivated by recent discussions, both in private and in the literature, we use a Monte Carlo simulation of planetary systems to investigate sources of bias in determining the mass-radius distribution of exoplanets for the two primary techniques used to measure planetary masses---Radial Velocities (RVs) and Transit Timing Variations (TTVs). We assert that mass measurements derived from these two methods are comparably reliable---as the physics underlying their respective signals is well understood. Nevertheless, their sensitivity to planet mass varies with the properties of the planets themselves. We find that for a given planet size, the RV method tends to find planets with higher mass while the sensitivity of TTVs is more uniform. This ``sensitivity bias'' implies that a complete census of TTV systems is likely to yield a more robust estimate of the mass-radius distribution provided there are not important physical differences between planets near and far from mean-motion resonance. We discuss differences in...

  2. Bayesian Planet Searches for the 10 cm/s Radial Velocity Era

    Science.gov (United States)

    Gregory, Philip C.

    2016-10-01

    A new apodized Keplerian model is proposed for the analysis of precision radial velocity (RV) data to model both planetary and stellar activity (SA) induced RV signals. A symmetrical Gaussian apodization function with unknown width and center can distinguish planetary signals from SA signals on the basis of the width of the apodization function. The general model for m apodized Keplerian signals also includes a linear regression term between RV and the stellar activity diagnostic In (R'hk), as well as an extra Gaussian noise term with unknown standard deviation. The model parameters are explored using a Bayesian fusion MCMC code. A differential version of the Generalized Lomb-Scargle periodogram provides an additional way of distinguishing SA signals and helps guide the choice of new periods. Sample results are reported for a recent international RV blind challenge which included multiple state of the art simulated data sets supported by a variety of stellar activity diagnostics.

  3. Red Optical Planet Survey: A radial velocity search for low mass M dwarf planets

    Directory of Open Access Journals (Sweden)

    Minniti D.

    2013-04-01

    Full Text Available We present radial velocity results from our Red Optical Planet Survey (ROPS, aimed at detecting low-mass planets orbiting mid-late M dwarfs. The ∼10 ms−1 precision achieved over 2 consecutive nights with the MIKE spectrograph at Magellan Clay is also found on week long timescales with UVES at VLT. Since we find that UVES is expected to attain photon limited precision of order 2 ms−1 using our novel deconvolution technique, we are limited only by the (≤10 ms−1 stability of atmospheric lines. Rocky planet frequencies of η⊕ = 0.3−0.7 lead us to expect high planet yields, enabling determination of η⊕ for the uncharted mid-late M dwarfs with modest surveys.

  4. Extracting kinetic freeze-out temperature and radial flow velocity from an improved Tsallis distribution

    CERN Document Server

    Lao, Hai-Ling; Lacey, Roy A

    2016-01-01

    We analyze the transverse momentum ($p_T$) spectra of identified particles ($\\pi^{\\pm}$, $K^{\\pm}$, $p$, and $\\bar p$) produced in gold-gold (Au-Au) and lead-lead (Pb-Pb) collisions over a $\\sqrt{s_{NN}}$ (center-of-mass energy per nucleon pair) range from 14.5 GeV [one of the Relativistic Heavy Ion Collider (RHIC) energies] to 2.76 TeV [one of the Large Hadron Collider (LHC) energies]. For the spectra with a narrow $p_T$ range, an improved Tsallis distribution which is in fact the Tsallis distribution with radial flow is used. For the spectra with a wide $p_T$ range, a superposition of the improved Tsallis distribution and an inverse power-law is used. Both the extracted kinetic freeze-out temperature ($T_0$) and radial flow velocity ($\\beta_T$) increase with the increase of $\\sqrt{s_{NN}}$, which indicate a higher excitation and larger expansion of the interesting system at the LHC. Both the values of $T_0$ and $\\beta_T$ in central collisions are slightly larger than those in peripheral collisions, and they...

  5. The SDSS-III APOGEE radial velocity survey of M dwarfs. I. Description of the survey and science goals

    Energy Technology Data Exchange (ETDEWEB)

    Deshpande, R.; Bender, C. F.; Mahadevan, S.; Terrien, R. C.; Schneider, D. P.; Fleming, S. W. [Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, University Park, PA 16802 (United States); Blake, C. H. [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 (United States); Carlberg, J. K. [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015 (United States); Zasowski, G.; Hearty, F. [University of Virginia, 530 McCormick Road, Charlottesville, VA 22904 (United States); Crepp, J. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Rajpurohit, A. S.; Reylé, C. [Institut UTINAM, CNRS UMR 6213, Observatoire des Sciences de l' Univers THETA Franche-Comt é-Bourgogne, Université de Franche Comté, Observatoire de Besançon, BP 1615, F-25010 Besançon Cedex (France); Nidever, D. L. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Prieto, C. Allende; Hernández, J. [Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife (Spain); Bizyaev, D. [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349-0059 (United States); Ebelke, G. [Department of Physics and Astronomy, Texas Christian University, TCU Box 298840, Fort Worth, TX 76129 (United States); Frinchaboy, P. M. [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055 (United States); Ge, J. [Department of Astronomy, Ohio State University, Columbus, OH 43210 (United States); and others

    2013-12-01

    We are carrying out a large ancillary program with the Sloan Digital Sky Survey, SDSS-III, using the fiber-fed multi-object near-infrared APOGEE spectrograph, to obtain high-resolution H-band spectra of more than 1200 M dwarfs. These observations will be used to measure spectroscopic rotational velocities, radial velocities, physical stellar parameters, and variability of the target stars. Here, we describe the target selection for this survey, as well as results from the first year of scientific observations based on spectra that will be publicly available in the SDSS-III DR10 data release. As part of this paper we present radial velocities and rotational velocities of over 200 M dwarfs, with a vsin i precision of ∼2 km s{sup –1} and a measurement floor at vsin i = 4 km s{sup –1}. This survey significantly increases the number of M dwarfs studied for rotational velocities and radial velocity variability (at ∼100-200 m s{sup –1}), and will inform and advance the target selection for planned radial velocity and photometric searches for low-mass exoplanets around M dwarfs, such as the Habitable Zone Planet Finder, CARMENES, and TESS. Multiple epochs of radial velocity observations enable us to identify short period binaries, and adaptive optics imaging of a subset of stars enables the detection of possible stellar companions at larger separations. The high-resolution APOGEE spectra, covering the entire H band, provide the opportunity to measure physical stellar parameters such as effective temperatures and metallicities for many of these stars. At the culmination of this survey, we will have obtained multi-epoch spectra and radial velocities for over 1400 stars spanning the spectral range M0-L0, providing the largest set of near-infrared M dwarf spectra at high resolution, and more than doubling the number of known spectroscopic vsin i values for M dwarfs. Furthermore, by modeling telluric lines to correct for small instrumental radial velocity shifts, we

  6. The VLT-FLAMES Tarantula Survey XVIII. Classifications and radial velocities of the B-type stars

    CERN Document Server

    Evans, C J; Dufton, P L; Howarth, I D; Walborn, N R; Markova, N; Clark, J S; de Mink, S E; de Koter, A; Dunstall, P R; Hénault-Brunet, V; Apellániz, J Maíz; McEvoy, C M; Sana, H; Simón-Díaz, S; Taylor, W D; Vink, J S

    2015-01-01

    We present spectral classifications for 438 B-type stars observed as part of the VLT-FLAMES Tarantula Survey (VFTS) in the 30 Doradus region of the Large Magellanic Cloud. Radial velocities are provided for 307 apparently single stars, and for 99 targets with radial-velocity variations which are consistent with them being spectroscopic binaries. We investigate the spatial distribution of the radial velocities across the 30 Dor region, and use the results to identify candidate runaway stars. Excluding potential runaways and members of two older clusters in the survey region (SL 639 and Hodge 301), we determine a systemic velocity for 30 Dor of 271.6 +/- 12.2 km/s from 273 presumed single stars. Employing a 3-sigma criterion we identify nine candidate runaway stars (2.9% of the single stars with radial-velocity estimates). The projected rotational velocities of the candidate runaways appear to be significantly different to those of the full B-type sample, with a strong preference for either large (>345 km/s) or...

  7. The catalog of radial velocity standard stars for the Gaia RVS: status and progress of the observations

    CERN Document Server

    Chemin, L; Crifo, F; Jasniewicz, G; Veltz, L; Hestroffer, D; Udry, S; Berthier, J; Vigneron, A; Katz, D; Siebert, A

    2010-01-01

    A new full-sky catalog of Radial Velocity standard stars is being built for the determination of the Radial Velocity Zero Point of the RVS on board of Gaia. After a careful selection of 1420 candidates matching well defined criteria, we are now observing all of them to verify that they are stable enough over several years to be qualified as reference stars. We present the status of this long-term observing programme on three spectrographs : SOPHIE, NARVAL and CORALIE, complemented by the ELODIE and HARPS archives. Because each instrument has its own zero-point, we observe intensively IAU RV standards and asteroids to homogenize the radial velocity measurements. We can already estimate that ~8% of the candidates have to be rejected because of variations larger than the requested level of 300 m/s.

  8. Suppression of Fiber Modal Noise Induced Radial Velocity Errors for Bright Emission-line Calibration Sources

    Science.gov (United States)

    Mahadevan, Suvrath; Halverson, Samuel; Ramsey, Lawrence; Venditti, Nick

    2014-05-01

    Modal noise in optical fibers imposes limits on the signal-to-noise ratio (S/N) and velocity precision achievable with the next generation of astronomical spectrographs. This is an increasingly pressing problem for precision radial velocity spectrographs in the near-infrared (NIR) and optical that require both high stability of the observed line profiles and high S/N. Many of these spectrographs plan to use highly coherent emission-line calibration sources like laser frequency combs and Fabry-Perot etalons to achieve precision sufficient to detect terrestrial-mass planets. These high-precision calibration sources often use single-mode fibers or highly coherent sources. Coupling light from single-mode fibers to multi-mode fibers leads to only a very low number of modes being excited, thereby exacerbating the modal noise measured by the spectrograph. We present a commercial off-the-shelf solution that significantly mitigates modal noise at all optical and NIR wavelengths, and which can be applied to spectrograph calibration systems. Our solution uses an integrating sphere in conjunction with a diffuser that is moved rapidly using electrostrictive polymers, and is generally superior to most tested forms of mechanical fiber agitation. We demonstrate a high level of modal noise reduction with a narrow bandwidth 1550 nm laser. Our relatively inexpensive solution immediately enables spectrographs to take advantage of the innate precision of bright state-of-the art calibration sources by removing a major source of systematic noise.

  9. Starspot distributions on fully convective M dwarfs: implications for radial velocity planet searches

    CERN Document Server

    Barnes, J R; Jones, H R A; Pavlenko, Ya V; Jenkins, J S; Haswell, C A; Lohr, M E

    2015-01-01

    Since M4.5 - M9 dwarfs exhibit equatorial rotation velocities of order 10 km/s on average, radial velocity surveys targeting this stellar population will likely need to find methods to effectively remove starspot jitter. We present the first high resolution Doppler images of the M4.5 dwarf, GJ 791.2A, and the M9 dwarf, LP 944-20. The time series spectra of both objects reveal numerous line profile distortions over the rotation period of each star which we interpret as starspots. The transient distortions are modelled with spot/photosphere contrast ratios that correspond to model atmosphere temperature differences of Tphot-Tspot = 200 and 300 K. GJ 791.2A is a fully convective star with vsini = 35.1 km/s. Although we find more starspot structure at high latitudes, we reconstruct spots at a range of phases and latitudes with a mean spot filling of ~3%. LP 944-20 is one of the brightest known late-M dwarfs, with spectral type M9V and vsini = 30.8 km/s. Its spectral time series exhibits two dominant transient lin...

  10. The PRL Stabilized High Resolution Echelle Fiber-fed Spectrograph: Instrument Description & First Radial Velocity Results

    CERN Document Server

    Chakraborty, Abhijit; Roy, Arpita; Dixit, Vaibhav; Richardson, Eric Harvey; Dongre, Varun; Pathan, F M; Chaturvedi, Priyanka; Shah, Vishal; Ubale, Girish P; Anandarao, B G

    2013-01-01

    We present spectrograph design details and initial radial velocity results from the PRL optical fiber-fed high-resolution cross-dispersed echelle spectrograph (PARAS), which has recently been commissioned at the Mt Abu 1.2 m telescope, in India. Data obtained as part of the post-commissioning tests with PARAS show velocity precision better than 2m/s over a period of several months on bright RV standard stars. For observations of sigma-Dra we report 1.7m/s precision for a period of seven months and 2.1m/s for HD 9407 over a period of 2 months. PARAS is capable of a single-shot spectral coverage of 3800A - 9500A at a resolution of about 67,000. The RV results were obtained between 3800A and 6900A using simultaneous wavelength calibration with a Thorium-Argon (ThAr) hollow cathode lamp. The spectrograph is maintained under stable conditions of temperature with a precision of 0.01 - 0.02C (rms) at 25.55C, and enclosed in a vacuum vessel at pressure of 0.1 +/-0.03 mbar. The blaze peak efficiency of the spectrograp...

  11. VizieR Online Data Catalog: IN-SYNC. III. Radial velocities of IC348 stars (Cottaar+, 2015)

    Science.gov (United States)

    Cottaar, M.; Covey, K. R.; Foster, J. B.; Meyer, M. R.; Tan, J. C.; Nidever, D. L.; Drew Chojnowski, S.; da Rio, N.; Flaherty, K. M.; Frinchaboy, P. M.; Majewski, S.; Skrutskie, M. F.; Wilson, J. C.; Zasowski, G.

    2015-11-01

    Cottaar et al. (Paper I, 2014, J/ApJ/794/125) describes the analysis of the high-resolution near-infrared spectra obtained by the APOGEE multi-object spectrograph from stars in IC 348, NGC 1333, NGC 2264, and Orion A as part of the INfrared Spectroscopy of Young Nebulous Clusters (IN-SYNC) ancillary program. Using radial velocities determined from APOGEE spectra of 380 likely cluster members, we have measured the radial velocity distribution of the young (2-6Myr) cluster IC 348. (2 data files).

  12. Astrometry, radial velocity, and photometry: the HD 128311 system remixed with data from HST, HET, and APT

    Energy Technology Data Exchange (ETDEWEB)

    McArthur, Barbara E.; Benedict, G. Fritz.; Cochran, William D. [McDonald Observatory, University of Texas at Austin, Austin, TX 78712 (United States); Henry, Gregory W. [Center of Excellence in Information Systems, Tennessee State University, 3500 John A. Merritt Blvd., P.O. Box 9501, Nashville, TN 37209 (United States); Hatzes, Artie [Thüringer Landessternwarte, Sternwarte 5, D-07778 Tautenburg (Germany); Harrison, Tom E. [Department of Astronomy, New Mexico State, Las Cruces, NM 88003 (United States); Johns-Krull, Chris [Department of Physics and Astronomy, Rice University, MS-108, 6100 Main Street, Houston, TX 77005 (United States); Nelan, Ed, E-mail: mca@astro.as.utexas.edu [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2014-11-01

    We have used high-cadence radial velocity measurements from the Hobby-Eberly Telescope with published velocities from the Lick 3 m Shane Telescope, combined with astrometric data from the Hubble Space Telescope (HST) Fine Guidance Sensors to refine the orbital parameters of the HD 128311 system, and determine an inclination of 55.°95 ± 14.°55 and true mass of 3.789 {sub −0.432}{sup +0.924} M {sub JUP} for HD 128311 c. The combined radial velocity data also reveal a short period signal which could indicate a third planet in the system with an Msin i of 0.133 ± 0.005 M {sub JUP} or stellar phenomena. Photometry from the T12 0.8 m automatic photometric telescope at the Fairborn Observatory and HST are used to determine a photometric period close to, but not within the errors of the radial velocity signal. We performed a cross-correlation bisector analysis of the radial velocity data to look for correlations with the photometric period and found none. Dynamical integrations of the proposed system show long-term stability with the new orbital parameters of over 10 million years. Our new orbital elements do not support the claims of HD 128311 b and c being in mean motion resonance.

  13. Application of a probabilistic neural network in analysis of the radial velocity curve of spectroscopic binary stars

    Institute of Scientific and Technical Information of China (English)

    Kamal Ghaderi; Kayoomars Karami; Ali Pirkhedri; Hamid Haj Seyyed Javadi; Touba Rostami

    2012-01-01

    Using measured radial velocity data of five double-lined spectroscopic binary systems,HD 89959,HD 143705,HD 146361,HD 165052 and HD 152248,we find corresponding orbital and spectroscopic elements via a Probabilistic Neural Network.Our numerical results are in good agreement with those obtained by others using more traditional methods.

  14. A comprehensive radial velocity error budget for next generation Doppler spectrometers

    Science.gov (United States)

    Halverson, Samuel; Terrien, Ryan; Mahadevan, Suvrath; Roy, Arpita; Bender, Chad; Stefánsson, Gudmundur K.; Monson, Andrew; Levi, Eric; Hearty, Fred; Blake, Cullen; McElwain, Michael; Schwab, Christian; Ramsey, Lawrence; Wright, Jason; Wang, Sharon; Gong, Qian; Roberston, Paul

    2016-08-01

    We describe a detailed radial velocity error budget for the NASA-NSF Extreme Precision Doppler Spectrometer instrument concept NEID (NN-explore Exoplanet Investigations with Doppler spectroscopy). Such an instrument performance budget is a necessity for both identifying the variety of noise sources currently limiting Doppler measurements, and estimating the achievable performance of next generation exoplanet hunting Doppler spectrometers. For these instruments, no single source of instrumental error is expected to set the overall measurement floor. Rather, the overall instrumental measurement precision is set by the contribution of many individual error sources. We use a combination of numerical simulations, educated estimates based on published materials, extrapolations of physical models, results from laboratory measurements of spectroscopic subsystems, and informed upper limits for a variety of error sources to identify likely sources of systematic error and construct our global instrument performance error budget. While natively focused on the performance of the NEID instrument, this modular performance budget is immediately adaptable to a number of current and future instruments. Such an approach is an important step in charting a path towards improving Doppler measurement precisions to the levels necessary for discovering Earth-like planets.

  15. Radial velocity studies of HeII and Hβ emission from cataclysmic variables

    Science.gov (United States)

    Schwarz, C.; Montgomery, M. M.

    2014-02-01

    Radial velocity (RV) plots of HeII and Hβ emission lines from non-magnetic Cataclysmic Variable (CV) systems are frequently fit with a sin curve but sometimes contain outlying data points around phase ϕ∼1.0. A lack of consensus exists on the origin of these outlying points. In this work, we develop an analytical model that is based upon our 3D Smoothed Particle Hydrodynamic (SPH) numerical model to simulate these RV curves. Our chosen targets are CV SW Sextanis-like systems UX Uma and RW Tri as well as SU UMa dwarf novae systems Hα0242-28 and 1RXSJ1808+10, which have secondary-to-primary mass ratios of q = (0.43, 0.86, 0.27, 0.18), respectively. In our model, we include disk eccentricity, inclination angle, degree of disk-tilt, bright spot (s), and/or gas stream overflow. Our model provides good non-sinusoidal fits to the observed RV data, including outlying data points near ϕ∼1.0, suggesting these excess points may be caused by gas-stream overflow.

  16. SOAP: A Tool for the Fast Computation of Photometry and Radial Velocity Induced by Stellar Spots

    Science.gov (United States)

    Boisse, I.; Bonfils, X.; Santos, N. C.; Figueira, P.

    2013-04-01

    Dark spots and bright plages are present on the surface of dwarf stars from spectral types F to M, even in their low-active phase (like the Sun). Their appearance and disappearance on the stellar photosphere, combined with the stellar rotation, may lead to errors and uncertainties in the characterization of planets both in radial velocity (RV) and photometry. Spot Oscillation and Planet (SOAP) is a tool offered to the community that enables to simulate spots and plages on rotating stars and computes their impact on RV and photometric measurements. This tool will help to understand the challenges related to the knowledge of stellar activity for the next decade: detect telluric planets in the habitable zone of their stars (from G to M dwarfs), understand the activity in the low-mass end of M dwarf (on which future projects, like SPIRou or CARMENES, will focus), limitation to the characterization of the exoplanetary atmosphere (from the ground or with Spitzer, JWST), search for planets around young stars. These can be simulated with SOAP in order to search for indices and corrections to the effect of activity.

  17. VizieR Online Data Catalog: HIRES radial velocity measurements (Knutson+, 2014)

    Science.gov (United States)

    Knutson, H. A.; Fulton, B. J.; Montet, B. T.; Kao, M.; Ngo, H.; Howard, A. W.; Crepp, J. R.; Hinkley, S.; Bakos, G. A.; Batygin, K.; Johnson, J. A.; Morton, T. D.; Muirhead, P. S.

    2017-06-01

    We observed our target stars using the High Resolution Echelle Spectrometer (HIRES) (Vogt et al. 1994SPIE.2198..362V) on the 10 m Keck I telescope over a period of two years beginning in 2011; many of our targets also had existing HIRES observations taken prior to 2011 by other programs. We used the standard HIRES setup and reduction pipeline employed by the California Planet Search (CPS) consortium (Wright et al. 2004, J/ApJS/152/261; Howard et al. 2009ApJ...696...75H; Johnson et al. 2010PASP..122..149J). Observations were typically obtained with a slit width of 0.86" with integration times optimized to obtain typical signal to noise ratios of 70 per pixel. An iodine cell mounted in front of the spectrometer entrance slit provided a wavelength scale and instrumental profile for the observations (Marcy & Butler, 1992PASP..104..270M; Valenti et al. 1995PASP..107..966V). We obtained a total of approximately 270 new radial velocity measurements for our target sample, with a minimum of four observations per target separated by at least six months. (3 data files).

  18. TOWARD UNDERSTANDING STELLAR RADIAL VELOCITY JITTER AS A FUNCTION OF WAVELENGTH: THE SUN AS A PROXY

    Energy Technology Data Exchange (ETDEWEB)

    Marchwinski, Robert C.; Mahadevan, Suvrath; Robertson, Paul; Ramsey, Lawrence [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Harder, Jerald, E-mail: rcm236@psu.edu, E-mail: suvrath@astro.psu.edu, E-mail: pmr19@psu.edu, E-mail: lwr@psu.edu, E-mail: Jerry.Harder@lasp.colorado.edu [Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, 1234 Innovation Drive, Boulder, CO 80803 (United States)

    2015-01-01

    Using solar spectral irradiance measurements from the SORCE spacecraft and the F/F' technique, we have estimated the radial velocity (RV) scatter induced on the Sun by stellar activity as a function of wavelength. Our goal was to evaluate the potential advantages of using new near-infrared (NIR) spectrographs to search for low-mass planets around bright F, G, and K stars by beating down activity effects. Unlike M dwarfs, which have higher fluxes and therefore greater RV information content in the NIR, solar-type stars are brightest at visible wavelengths, and, based solely on information content, are better suited to traditional optical RV surveys. However, we find that the F/F' estimated RV noise induced by stellar activity is diminished by up to a factor of four in the NIR versus the visible. Observations with the upcoming future generation of NIR instruments can be a valuable addition to the search for low-mass planets around bright FGK stars in reducing the amount of stellar noise affecting RV measurements.

  19. Precise radial velocities of Proxima Centauri. Strong constraints on a substellar companion

    CERN Document Server

    Kürster, M; Cochran, W D; Döbereiner, S; Dennerl, K; Endl, M

    1999-01-01

    We present differential radial velocity measurements of Proxima Centauri collected over 4 years with the ESO CES with a mean precision of $54 ms^{-1}$. We find no evidence of a periodic signal that could corroborate the existence of a sub-stellar companion. We put upper limits (97% confidence) to the companion mass ranging from 1.1 to 22 M_{Jup} at orbital periods of 0.75 to 3000 d, i.e. separations 0.008-2 AU from Prox Cen. Our mass limits concur with limits found by precise astrometry (Benedict et al. 1998a and priv. comm.) which strongly constrain the period range 50-600 d to 1.1-0.22 M_{Jup}. Combining both results we exclude a brown dwarf or supermassive planet at separations 0.008-0.69 AU from Prox Cen. We also find that, at the level of our precision, the RV data are not affected by stellar activity.

  20. The catalogue of radial velocity variable hot subluminous stars from the MUCHFUSS project

    CERN Document Server

    Geier, S; Heber, U; Schaffenroth, V; Barlow, B N; stensen, R H O; O'Toole, S J; Ziegerer, E; Heuser, C; Maxted, P F L; Gänsicke, B T; Marsh, T R; Napiwotzki, R; Brünner, P; Schindewolf, M; Niederhofer, F

    2015-01-01

    The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims to find sdBs with compact companions like massive white dwarfs, neutron stars or black holes. Here we provide classifications, atmospheric parameters and a complete radial velocity (RV) catalogue containing 1914 single measurements for an sample of 177 hot subluminous stars discovered based on SDSS DR7. 110 stars show significant RV variability, while 67 qualify as candidates. We constrain the fraction of close massive compact companions {of hydrogen-rich hot subdwarfs} in our sample to be smaller than $\\sim1.3\\%$, which is already close to the theoretical predictions. However, the sample might still contain such binaries with longer periods exceeding $\\sim8\\,{\\rm d}$. We detect a mismatch between the $\\Delta RV_{\\rm max}$-distribution of the sdB and the more evolved sdOB and sdO stars, which challenges our understanding of their evolutionary connection. Furthermore, irregular RV variations of unknown origin with ...

  1. AN EFFICIENT, COMPACT, AND VERSATILE FIBER DOUBLE SCRAMBLER FOR HIGH PRECISION RADIAL VELOCITY INSTRUMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Halverson, Samuel; Roy, Arpita; Mahadevan, Suvrath; Ramsey, Lawrence; Levi, Eric; Schwab, Christian; Hearty, Fred [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); MacDonald, Nick, E-mail: shalverson@psu.edu, E-mail: aur17@psu.edu [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States)

    2015-06-10

    We present the design and test results of a compact optical fiber double-scrambler for high-resolution Doppler radial velocity instruments. This device consists of a single optic: a high-index n ∼ 2 ball lens that exchanges the near and far fields between two fibers. When used in conjunction with octagonal fibers, this device yields very high scrambling gains (SGs) and greatly desensitizes the fiber output from any input illumination variations, thereby stabilizing the instrument profile of the spectrograph and improving the Doppler measurement precision. The system is also highly insensitive to input pupil variations, isolating the spectrograph from telescope illumination variations and seeing changes. By selecting the appropriate glass and lens diameter the highest efficiency is achieved when the fibers are practically in contact with the lens surface, greatly simplifying the alignment process when compared to classical double-scrambler systems. This prototype double-scrambler has demonstrated significant performance gains over previous systems, achieving SGs in excess of 10,000 with a throughput of ∼87% using uncoated Polymicro octagonal fibers. Adding a circular fiber to the fiber train further increases the SG to >20,000, limited by laboratory measurement error. While this fiber system is designed for the Habitable-zone Planet Finder spectrograph, it is more generally applicable to other instruments in the visible and near-infrared. Given the simplicity and low cost, this fiber scrambler could also easily be multiplexed for large multi-object instruments.

  2. GIARPS: the unique VIS-NIR high precision radial velocity facility in this world

    CERN Document Server

    Claudi, Riccardo; Carleo, Ilaria; Ghedina, Adriano; Molinari, Emilio; Oliva, Ernesto; Tozzi, Andrea; Baruffolo, Andrea; Cecconi, Massimo; Cosentino, Rosario; Fantinel, Daniela; Fini, Luca; Ghinassi, Francesca; Gonzalez, Manuel; Gratton, Raffaele; Guerra, Jose; Harutyunyan, Avet; Hernandez, Nauzet; Iuzzolino, Marcella; Lodi, Marcello; Malavolta, Luca; Maldonado, Jesus; Micela, Giusi; Sanna, Nicoletta; Sanjuan, Jose; Scuderi, Salvo; Sozzetti, Alessandro; Ventura, Hector Perez; Diaz, Marcos Hernandez; Galli, Alberto; Gonzalez, Carlos; Riverol, Luis; Riverol, Carlos

    2016-01-01

    GIARPS (GIAno & haRPS) is a project devoted to have on the same focal station of the Telescopio Nazionale Galileo (TNG) both the high resolution spectrographs HARPS-N (VIS) and GIANO (NIR) working simultaneously. This could be considered the first and unique worldwide instrument providing cross-dispersed echelle spectroscopy at a high resolution (R=115,000 in the visual and R=50,000 in the IR) and over in a wide spectral range (0.383 - 2.45 micron) in a single exposure. The science case is very broad, given the versatility of such an instrument and the large wavelength range. A number of outstanding science cases encompassing mainly extra-solar planet science starting from rocky planet search and hot Jupiters, atmosphere characterization can be considered. Furthermore both instrument can measure high precision radial velocity by means the simultaneous thorium technique (HARPS - N) and absorbing cell technique (GIANO) in a single exposure. Other science cases are also possible. Young stars and proto-planet...

  3. No evidence for activity correlations in the radial velocities of Kapteyn's star

    CERN Document Server

    Anglada-Escudé, Guillem; Arriagada, Pamela; Zechmeister, Mathias; Jenkins, James S; Ofir, Aviv; Dreizler, Stefan; Gerlach, Enrico; Marvin, Chistopher J; Reiners, Ansgar; Jeffers, Sandra V; Butler, Paul; Vogt, Steven S; Amado, Pedro J; Rodríguez-López, Cristina; Berdiñas, Zaira M; Morin, Julien; Crane, Jeffrey D; Shectman, Stephen A; Díaz, Matías; Sarmiento, Luis F; Jones, Hugh R A

    2015-01-01

    Stellar activity may induce Doppler variability at the level of a few m/s which can then be confused by the Doppler signal of an exoplanet orbiting the star. To first order, linear correlations between radial velocity measurements and activity indices have been proposed to account for any such correlation. The likely presence of two super-Earths orbiting Kapteyn's star was reported in Anglada et al. (2014, MNRAS 443L, 89A), but this claim was recently challenged by Robertson et al. (2015, ApJ 805L, 22R) arguing evidence of a rotation period (143 days) at three times the orbital period of one of the proposed planets (Kapteyn's b, P=48.6 days), and the existence of strong linear correlations between its Doppler signal and activity data. By re-analyzing the data using global optimization methods and model comparison, we show that such claim is incorrect given that; 1) the choice of a rotation period at 143 days is unjustified, and 2) the presence of linear correlations is not supported by the data. We conclude t...

  4. Metallicity Distribution Functions, Radial Velocities, and Alpha Element Abundances in Three Off-Axis Bulge Fields

    CERN Document Server

    Johnson, Christian I; Kobayashi, Chiaki; Kunder, Andrea; Pilachowski, Catherine A; Koch, Andreas; De Propris, Roberto

    2013-01-01

    We present radial velocities and chemical abundance ratios of [Fe/H], [O/Fe], [Si/Fe], and [Ca/Fe] for 264 red giant branch (RGB) stars in three Galactic bulge off-axis fields located near (l,b)=(-5.5,-7), (-4,-9), and (+8.5,+9). The results are based on equivalent width and spectrum synthesis analyses of moderate resolution (R~18,000), high signal-to-noise ratio (S/N~75-300) spectra obtained with the Hydra spectrographs on the Blanco 4m and WIYN 3.5m telescopes. The targets were selected from the blue side of the giant branch to avoid cool stars that would be strongly affected by CN and TiO; however, a comparison of the color-metallicity distribution in literature samples suggests our selection of bluer targets should not present a significant bias against metal-rich stars. We find a full range in metallicity that spans [Fe/H]\\approx-1.5 to +0.5, and that, in accordance with the previously observed minor-axis vertical metallicity gradient, the median [Fe/H] also declines with increasing Galactic latitude in ...

  5. BACHES - a compact \\'echelle spectrograph for radial velocity surveys with small telescopes

    CERN Document Server

    Kozłowski, S K; Ratajczak, M; Sybilski, P; Pawłaszek, R K; Hełminiak, K G

    2014-01-01

    We evaluate a pre-production BACHES \\'{e}chelle spectrograph in terms of its usefulness for radial velocity surveys of binary stars with small telescopes in a remote and autonomous. We use the Solaris-4 observatory located in Casleo, Argentina, that is part of a global network of autonomous observatories as the test-bed for the instrument. The setup is designed in such a way that spectroscopy and photometry can be carried out using the same telescope without the need to mechanically modify the imaging train. We observe single spectroscopic standard stars as well as binary stars up to 9.75 mag. We present results of mechanical tests of the instruments and spectroscopic observations carried out between Nov 26th and Dec 8th 2013. We conclude that BACHES is a very compact and capable spectrograph well suited for remote and autonomous operation. Coupled to a 0.5-m telescope it is capable of obtaining spectra of 10 mag targets with a SNR of 20 for 30-minute exposures. This is a very good result considering the pric...

  6. High-Contrast Imaging for Intermediate-Mass Giants with Long-Term Radial Velocity Trends

    CERN Document Server

    Ryu, Tsuguru; Kuzuhara, Masayuki; Narita, Norio; Takahashi, Yasuhiro H; Uyama, Taichi; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Hashimoto, Jun; Omiya, Masashi; Harakawa, Hiroki; Abe, Lyu; Ando, Hiroyasu; Brandner, Wolfgang; Brandt, Timothy D; Carson, Joseph C; Currie, Thayne; Egner, Sebastian; Feldt, Markus; Goto, Miwa; Grady, Carol A; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S; Hełminiak, Krzysztof G; Henning, Thomas; Hodapp, Klaus W; Ida, Shigeru; Ishii, Miki; Itoh, Yoichi; Iye, Masanori; Izumiura, Hideyuki; Janson, Markus; Kambe, Eiji; Kandori, Ryo; Knapp, Gillian R; Kokubo, Eiichiro; Kwon, Jungmi; Matsuo, Taro; Mayama, Satoshi; McElwain, Michael W; Mede, Kyle; Miyama, Shoken; Morino, Jun-Ichi; Moro-Martin, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suenaga, Takuya; Suto, Hiroshi; Suzuki, Ryuji; Takami, Michihiro; Takato, Naruhisa; Takeda, Yoichi; Terada, Hiroshi; Thalmann, Christian; Turner, Edwin L; Watanabe, Makoto; Wisniewski, John; Yamada, Toru; Yoshida, Michitoshi; Takami, Hideki; Usuda, Tomonori; Tamura, Motohide

    2016-01-01

    A radial velocity (RV) survey for intermediate-mass giants has been operated for over a decade at Okayama Astrophysical Observatory (OAO). The OAO survey has revealed that some giants show long-term linear RV accelerations (RV trends), indicating the presence of outer companions. Direct imaging observations can help clarify what objects generate these RV trends. We present the results of high-contrast imaging observations or six intermediate-mass giants with long-term RV trends using the Subaru Telescope and HiCIAO camera. We detected co-moving companions to $\\gamma$ Hya B ($0.61^{+0.12}_{-0.14} M_\\odot$), HD 5608 B ($0.10 \\pm 0.01 M_\\odot$), and HD 109272 B ($0.28 \\pm 0.06 M_\\odot$). For the remaining targets($\\iota$ Dra, 18 Del, and HD 14067) we exclude companions more massive than 30-60 $M_\\mathrm{Jup}$ at projected separations of 1arcsec-7arcsec. We examine whether these directly imaged companions or unidentified long-period companions can account for the RV trends observed around the six giants. We find ...

  7. The impact of red noise in radial velocity planet searches: Only three planets orbiting GJ581?

    CERN Document Server

    Baluev, Roman V

    2012-01-01

    We perform a detailed analysis of the latest HARPS and Keck radial velocity data for the planet-hosting red dwarf GJ581, which attracted a lot of attention in recent time. We show that these data contain important correlated noise component ("red noise") with the correlation timescale of the order of 10 days. This red noise imposes a lot of misleading effects while we work in the traditional white-noise model. To eliminate these misleading effects, we propose a maximum-likelihood algorithm equipped by an extended model of the noise structure. We treat the red noise as a Gaussian random process with exponentially decaying correlation function. Using this method we prove that: (i) planets b and c do exist in this system, since they can be independently detected in the HARPS and Keck data, and regardless of the assumed noise models; (ii) planet e can also be confirmed independently by the both datasets, although to reveal it in the Keck data it is mandatory to take the red noise into account; (iii) the recently ...

  8. Asymmetric Orbital Distribution near Mean Motion Resonance: Application to Planets Observed by Kepler and Radial Velocities

    CERN Document Server

    Xie, Ji-Wei

    2016-01-01

    Many multiple-planet systems have been found by the Kepler transit survey and various radial velocity (RV) surveys. Kepler planets show an asymmetric feature, namely, there are small but significant deficits/excesses of planet pairs with orbital period spacing slightly narrow/wide of the exact resonance, particularly near the first order mean motion resonance (MMR), such as 2:1 and 3:2 MMR. Similarly, if not exactly the same, an asymmetric feature (pileup wide of 2:1 MMR) is also seen in RV planets, but only for massive ones. We analytically and numerically study planets' orbital evolutions near and in the MMR. We find that their orbital period ratios could be asymmetrically distributed around the MMR center regardless of dissipation. In the case of no dissipation, Kepler planets' asymmetric orbital distribution could be partly reproduced for 3:2 MMR but not for 2:1 MMR, implying that dissipation might be more important to the latter. The pileup of massive RV planets just wide of 2:1 MMR is found to be consis...

  9. A stable and inexpensive wavelength reference for precise wavelength calibration of radial velocity spectrographs

    Science.gov (United States)

    Feger, Tobias; Ireland, Michael J.; Bento, Joao; Bacigalupo, Carlos

    2014-08-01

    We present a stable, inexpensive wavelength reference, based on a white-light interferometer for the use on current and future (arrays of) diffraction-limited radial velocity (RV) spectrographs. The primary aim of using an interferometer is to obtain a dense sinusoidal wavelength reference with spectral coverage between 450-650 nm. Its basic setup consists of an unbalanced fiber Mach-Zehnder interferometer (FMZI) that creates an interference pattern in the spectral domain due to superposition of phase delayed light, set by a fixed optical path-length difference (OPD). To achieve long-term stability, the interferometer is actively locked to a stable atomic line. The system operates in closed-loop using a thermo-optic modulator as the phase feedback component. We conducted stability measurements by superimposing the wavelength reference with thorium-argon (ThAr) emission lines and found the differential RMS shift to be ~5 m s-1 within 30 minute bins in an experiment lasting 5 hours.

  10. GIARPS: the unique VIS-NIR high precision radial velocity facility in this world

    Science.gov (United States)

    Claudi, R.; Benatti, S.; Carleo, I.; Ghedina, A.; Molinari, E.; Oliva, E.; Tozzi, A.; Baruffolo, A.; Cecconi, M.; Cosentino, R.; Fantinel, D.; Fini, L.; Ghinassi, F.; Gonzalez, M.; Gratton, R.; Guerra, J.; Harutyunyan, A.; Hernandez, N.; Iuzzolino, M.; Lodi, M.; Malavolta, L.; Maldonado, J.; Micela, G.; Sanna, N.; Sanjuan, J.; Scuderi, S.; Sozzetti, A.; Pérez Ventura, H.; Diaz Marcos, H.; Galli, A.; Gonzalez, C.; Riverol, L.; Riverol, C.

    2016-08-01

    GIARPS (GIAno and haRPS) is a project devoted to have on the same focal station of the Telescopio Nazionale Galileo (TNG) both the high resolution spectrographs HARPS-N (VIS) and GIANO (NIR) working simultaneously. This could be considered the first and unique worldwide instrument providing cross-dispersed echelle spectroscopy at a high resolution (R=115,000 in the visual and R=50,000 in the IR) and over in a wide spectral range (0.383 - 2.45 μm) in a single exposure. The science case is very broad, given the versatility of such an instrument and the large wavelength range. A number of outstanding science cases encompassing mainly extra-solar planet science starting from rocky planet search and hot Jupiters, atmosphere characterization can be considered. Furthermore both instrument can measure high precision radial velocity by means the simultaneous thorium technique (HARPS - N) and absorbing cell technique (GIANO) in a single exposure. Other science cases are also possible. Young stars and proto- planetary disks, cool stars and stellar populations, moving minor bodies in the solar system, bursting young stellar objects, cataclysmic variables and X-ray binary transients in our Galaxy, supernovae up to gamma-ray bursts in the very distant and young Universe, can take advantage of the unicity of this facility both in terms of contemporaneous wide wavelength range and high resolution spectroscopy.

  11. Detecting planets around active stars: impact of magnetic fields on radial velocities and line bisectors

    Science.gov (United States)

    Hébrard, É. M.; Donati, J.-F.; Delfosse, X.; Morin, J.; Boisse, I.; Moutou, C.; Hébrard, G.

    2014-09-01

    Although technically challenging, detecting Earth-like planets around very low mass stars is in principle accessible to the existing velocimeters of highest radial-velocity (RV) precision. However, low-mass stars being active, they often feature dark spots and magnetic regions at their surfaces generating a noise level in RV curves (called activity jitter) that can severely limit our practical ability at detecting Earth-like planets. Whereas the impact of dark spots on RV data has been extensively studied in the literature, that of magnetic features only received little attention up to now. In this paper, we aim at quantifying the impact of magnetic fields (and the Zeeman broadening they induce) on line profiles, line bisectors and RV data. With a simple model, we quantitatively study the RV signals and bisector distortions that small magnetic regions or global magnetic dipoles can generate, especially at infrared wavelengths where the Zeeman broadening is much larger than that in the visible. We report in particular that the impact of magnetic features on line bisectors can be different from that of cool spots when the rotational broadening is comparable to or larger than the Zeeman broadening; more specifically, we find in this case that the top and bottom sections of the bisectors are anticorrelated, i.e. the opposite behaviour of what is observed for cool spots. We finally suggest new options to show and ultimately filter the impact of the magnetic activity on RV curves.

  12. Radial velocity curve of the spectroscopic binary HD 25639 (ADS 2984A)

    Science.gov (United States)

    Gorda, S. Yu.

    2016-10-01

    We present the results of the reduction of our observations for the spectroscopic binary ADS 2984A (B0 II-B0 III), which along with its visual component ADS 2984B (SZ Cam) are the brightest members of the open star cluster NGC 1502. The spectroscopic data were obtained with a fiber-fed echelle spectrograph ( R = 15 000) at the 1.2-m telescope of the Astronomical Observatory of the Ural Federal University. The period of ADS 2984A ( P orb = 57.24 ± 0.05 days) has been found for the first time. This spectroscopic binary is shown to belong to the SB1 type. We have determined the parameters of the radial velocity curve for the visible spectroscopic component, V 0 = -5.5 ± 1.2 km s-1 and K = 41.5 ± 1.7 km s-1. The lower mass limit for the invisible spectroscopic component has been estimated to be 5M_ ⊙ . Evidence for the presence of a stellar wind outflowing from the surface of this blue giant is presented.

  13. Near-infrared calibration systems for precise radial-velocity measurements

    Science.gov (United States)

    Redman, Stephen L.; Kerber, Florian; Nave, Gillian; Mahadevan, Suvrath; Ramsey, Lawrence W.; Smoker, Jonathan; Käufl, Hans-Ulrich; Figueira, P. R. L.

    2012-09-01

    We present work done to prepare two new near-infrared calibration sources for use on high-precision astrophysical spectrographs. Uranium-neon is an atomic calibration source, commercially available as a hollow-cathode lamp, with over 10 000 known emission lines between 0.85 and 4 μm. Four gas cells — containing C2H2, H13CN, 12CO, and 13CO, respectively—are available as National Institute of Standards and Technology (nist) Standard Reference Materials (SRMs), and provide narrow absorption lines between 1.5 and 1.65 μm. These calibration sources may prove useful for wavelength-calibrating the future near-infrared high-precision radial-velocity spectrometers, including the Calar Alto high-Resolution search for M dwarfs with Exo-earths with a Near-infrared Echelle Spectrograph (CARMENES),1 the SpectroPolarimetre InfraROUge (SPIRou)∗, and the Habitable-Zone Planet Finder (HPF).2

  14. Sensitivity bias in the mass-radius distribution from transit timing variations and radial velocity measurements

    Science.gov (United States)

    Steffen, Jason H.

    2016-04-01

    Motivated by recent discussions, both in private and in the literature, we use a Monte Carlo simulation of planetary systems to investigate sources of bias in determining the mass-radius distribution of exoplanets for the two primary techniques used to measure planetary masses - radial velocities (RVs) and transit timing variations (TTVs). We assert that mass measurements derived from these two methods are comparably reliable - as the physics underlying their respective signals is well understood. Nevertheless, their sensitivity to planet mass varies with the properties of the planets themselves. We find that for a given planet size, the RV method tends to find planets with higher mass while the sensitivity of TTVs is more uniform. This `sensitivity bias' implies that a complete census of TTV systems is likely to yield a more robust estimate of the mass-radius distribution provided there are not important physical differences between planets near and far from mean-motion resonance. We discuss differences in the sensitivity of the two methods with orbital period and system architecture, which may compound the discrepancies between them (e.g. short-period planets detectable by RVs may be more dense due to atmospheric loss). We advocate for continued mass measurements using both approaches as a means both to measure the masses of more planets and to identify potential differences in planet structure that may result from their dynamical and environmental histories.

  15. Extracting Radial Velocities of A- and B-type Stars from Echelle Spectrograph Calibration Spectra

    Science.gov (United States)

    Becker, Juliette C.; Johnson, John Asher; Vanderburg, Andrew; Morton, Timothy D.

    2015-04-01

    We present a technique to extract radial velocity (RV) measurements from echelle spectrograph observations of rapidly rotating stars (V sin i≳ 50 km s-1). This type of measurement is difficult because the line widths of such stars are often comparable to the width of a single echelle order. To compensate for the scarcity of lines and Doppler information content, we have developed a process that forward-models the observations, fitting the RV shift of the star for all echelle orders simultaneously with the echelle blaze function. We use our technique to extract RV measurements from a sample of rapidly rotating A- and B-type stars used as calibrator stars observed by the California Planet Survey observations. We measure absolute RVs with a precision ranging from 0.5-2.0 km s-1 per epoch for more than 100 A- and B-type stars. In our sample of 10 well-sampled stars with RV scatter in excess of their measurement uncertainties, three of these are single-lined binaries with long observational baselines. From this subsample, we present detections of two previously unknown spectroscopic binaries and one known astrometric system. Our technique will be useful in measuring or placing upper limits on the masses of sub-stellar companions discovered by wide-field transit surveys, and conducting future spectroscopic binarity surveys and Galactic space-motion studies of massive and/or young, rapidly rotating stars.

  16. The iLocater cryostat: design and thermal control strategy for precision radial velocity measurements

    CERN Document Server

    Crass, Jonathan; Hearty, Frederick R; Crepp, Justin R; Nelson, Matthew J; Wall, Sheila M; Cavalieri, David A; Koca, Corina; King, David L; Reynolds, Robert O; Stapelfeldt, Karl R

    2016-01-01

    The current generation of precision radial velocity (RV) spectrographs are seeing-limited instruments. In order to achieve high spectral resolution on 8m class telescopes, these spectrographs require large optics and in turn, large instrument volumes. Achieving milli-Kelvin thermal stability for these systems is challenging but is vital in order to obtain a single measurement RV precision of better than 1m/s. This precision is crucial to study Earth-like exoplanets within the habitable zone. iLocater is a next generation RV instrument being developed for the Large Binocular Telescope. Unlike seeing-limited RV instruments, iLocater uses adaptive optics (AO) to inject a diffraction-limited beam into single-mode fibers. These fibers illuminate the instrument spectrograph, facilitating a diffraction-limited design and a small instrument volume compared to present-day instruments. This enables intrinsic instrument stability and facilitates precision thermal control. We present the current design of the iLocater cr...

  17. The Latest Results from Project NIRRVS: Precise Near Infrared Radial Velocity Surveys

    Science.gov (United States)

    Plavchan, Peter; NIRRVS Collaboration

    2016-06-01

    We will present the latest results from a prototype PRV survey with CSHELL. With CSHELL at the NASA Infrared Telescope Facility atop Mauna Kea (R~46,000), we have completed a PRV 2.3 micron survey to detect exoplanets around ~30 red, low mass, and young stars. We are able to reach long-term radial velocity dispersions of ~30 m/s on our survey targets. We are following up candidate RV variables, and have confirmed other previously known RV variables. With a spectral grasp of only 5 nm at 2.3 microns, this performance with CSHELL is limited by detector artifacts, and fringing in the data and flatfields. iSHELL will replace CSHELL at IRTF, with first light expected in May 2016. iSHELL is a 1.15-5.4 micron high spectral resolution (R~70,000) immersion grating, cross-dispersed, white pupil spectrograph. With iSHELL we should be able to obtain a precision of less than 5 m/s in the NIR with iSHELL from the improvements in spectral grasp alone.

  18. Near-infrared Metallicities, Radial Velocities and Spectral Types for 447 Nearby M Dwarfs

    CERN Document Server

    Newton, Elisabeth R; Irwin, Jonathan; Berta-Thompson, Zachory K; Rojas-Ayala, Barbara; Covey, Kevin; Lloyd, James P

    2013-01-01

    We present metallicities, radial velocities and near-infrared spectral types for 447 M dwarfs determined from moderate resolution (R~2000) near-infrared (NIR) spectra obtained with IRTF/SpeX. These M dwarfs are targets of the MEarth Survey, a transiting planet survey searching for super Earths around mid-to-late M dwarfs within 33pc. We present NIR spectral types and new IRTF spectral templates in the Z, J, H and K-bands, created using M dwarfs with near-solar metallicities. We developed two spectroscopic distance calibrations that use NIR spectral type or an index based on the curvature of the K-band continuum. Our distance calibration has a scatter of 14%. We searched 27 NIR spectral lines and 10 spectral indices for metallicity sensitive features, taking into account correlated noise in our estimates of the errors on these parameters. We calibrated our relation using 36 M dwarfs in common proper pairs with an F, G or K-type star of known metallicity. We validated the physical association of these pairs usi...

  19. Radial velocity information content of M dwarf spectra in the near-infrared

    CERN Document Server

    Figueira, P; Oshagh, M; Neal, J J; Rojas-Ayala, B; Lovis, C; Melo, C; Pepe, F; Santos, N C; Tsantaki, M

    2015-01-01

    Aims: We evaluate the radial velocity (RV) information content and achievable precision on M0-M9 spectra covering the ZYJHK bands. We do so while considering both a perfect atmospheric transmission correction and discarding areas polluted by deep telluric features, as done in previous works. Methods: To simulate the M-dwarf spectra, PHOENIX-ACES model spectra were employed; they were convolved with rotational kernels and instrumental profiles to reproduce stars with a $v.sin{i}$ of 1.0, 5.0, and 10.0 km/s when observed at resolutions of 60 000, 80 000, and 100 000. We considered the RV precision as calculated on the whole spectra, after discarding strongly polluted areas, and after applying a perfect telluric correction. In our simulations we paid particular attention to the details of the convolution and sampling of the spectra, and we discuss their impact on the final spectra. Results: Our simulations show that the most important parameter ruling the difference in attainable precision between the considered...

  20. High-contrast Imaging of Intermediate-mass Giants with Long-term Radial Velocity Trends

    Science.gov (United States)

    Ryu, Tsuguru; Sato, Bun'ei; Kuzuhara, Masayuki; Narita, Norio; Takahashi, Yasuhiro H.; Uyama, Taichi; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Hashimoto, Jun; Omiya, Masashi; Harakawa, Hiroki; Abe, Lyu; Ando, Hiroyasu; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph C.; Currie, Thayne; Egner, Sebastian; Feldt, Markus; Goto, Miwa; Grady, Carol A.; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S.; Hełminiak, Krzysztof G.; Henning, Thomas; Hodapp, Klaus W.; Ida, Shigeru; Ishii, Miki; Itoh, Yoichi; Iye, Masanori; Izumiura, Hideyuki; Janson, Markus; Kambe, Eiji; Kandori, Ryo; Knapp, Gillian R.; Kokubo, Eiichiro; Kwon, Jungmi; Matsuo, Taro; Mayama, Satoshi; McElwain, Michael W.; Mede, Kyle; Miyama, Shoken; Morino, Jun-Ichi; Moro-Martin, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suenaga, Takuya; Suto, Hiroshi; Suzuki, Ryuji; Takami, Michihiro; Takato, Naruhisa; Takeda, Yoichi; Terada, Hiroshi; Thalmann, Christian; Turner, Edwin L.; Watanabe, Makoto; Wisniewski, John; Yamada, Toru; Yoshida, Michitoshi; Takami, Hideki; Usuda, Tomonori; Tamura, Motohide

    2016-07-01

    A radial velocity (RV) survey for intermediate-mass giants has been in operation for over a decade at Okayama Astrophysical Observatory (OAO). The OAO survey has revealed that some giants show long-term linear RV accelerations (RV trends), indicating the presence of outer companions. Direct-imaging observations can help clarify what objects generate these RV trends. We present the results of high-contrast imaging observations of six intermediate-mass giants with long-term RV trends using the Subaru Telescope and HiCIAO camera. We detected co-moving companions to γ Hya B ({0.61}-0.14+0.12{M}⊙ ), HD 5608 B (0.10+/- 0.01{M}⊙ ), and HD 109272 B (0.28+/- 0.06{M}⊙ ). For the remaining targets (ι Dra, 18 Del, and HD 14067), we exclude companions more massive than 30-60 M Jup at projected separations of 1″-7″. We examine whether these directly imaged companions or unidentified long-period companions can account for the RV trends observed around the six giants. We find that the Kozai mechanism can explain the high eccentricity of the inner planets ι Dra b, HD 5608 b, and HD 14067 b.

  1. The impact of red noise in radial velocity planet searches: only three planets orbiting GJ 581?

    Science.gov (United States)

    Baluev, Roman V.

    2013-03-01

    We perform a detailed analysis of the latest HARPS and Keck radial velocity data for the planet-hosting red dwarf GJ 581, which attracted a lot of attention in recent time. We show that these data contain important correlated noise component (`red noise') with the correlation time-scale of the order of 10 d. This red noise imposes a lot of misleading effects while we work in the traditional white-noise model. To eliminate these misleading effects, we propose a maximum-likelihood algorithm equipped by an extended model of the noise structure. We treat the red noise as a Gaussian random process with an exponentially decaying correlation function. Using this method we prove that (i) planets b and c do exist in this system, since they can be independently detected in the HARPS and Keck data, and regardless of the assumed noise models; (ii) planet e can also be confirmed independently by both the data sets, although to reveal it in the Keck data it is mandatory to take the red noise into account; (iii) the recently announced putative planets f and g are likely just illusions of the red noise; (iv) the reality of the planet candidate GJ 581 d is questionable, because it cannot be detected from the Keck data, and its statistical significance in the HARPS data (as well as in the combined data set) drops to a marginal level of ˜2σ, when the red noise is taken into account. Therefore, the current data for GJ 581 really support the existence of no more than four (or maybe even only three) orbiting exoplanets. The planet candidate GJ 581 d requests serious observational verification.

  2. Efficient scheduling of astronomical observations. Application to the CARMENES radial-velocity survey

    Science.gov (United States)

    Garcia-Piquer, A.; Morales, J. C.; Ribas, I.; Colomé, J.; Guàrdia, J.; Perger, M.; Caballero, J. A.; Cortés-Contreras, M.; Jeffers, S. V.; Reiners, A.; Amado, P. J.; Quirrenbach, A.; Seifert, W.

    2017-08-01

    Context. Targeted spectroscopic exoplanet surveys face the challenge of maximizing their planet detection rates by means of careful planning. For a large planet survey, the number of possible observation combinations, i.e., the sequence of observations night after night, both in total time and amount of targets, is enormous. Aims: Sophisticated scheduling tools and the improved understanding of the exoplanet population are employed to investigate an efficient and optimal way to plan the execution of observations. This is applied to the CARMENES instrument, which is an optical and infrared high-resolution spectrograph that has started a survey of about 300 M-dwarf stars in search of terrestrial exoplanets. Methods: We used evolutionary computation techniques to create an automatic scheduler that minimizes the idle periods of the telescope and distributes the observations among all the targets using configurable criteria. We simulated the case of the CARMENES survey with a realistic sample of targets, and we estimated the efficiency of the planning tool both in terms of telescope operations and planet detection. Results: Our scheduling simulations produce plans that use about 99% of the available telescope time (including overheads) and optimally distribute the observations among the different targets. Under such conditions, and using current planet statistics, the optimized plan using this tool should allow the CARMENES survey to discover about 65% of the planets with radial-velocity semi-amplitudes greater than 1 ms-1 when considering only photon noise. Conclusions: The simulations using our scheduling tool show that it is possible to optimize the survey planning by minimizing idle instrument periods and fulfilling the science objectives in an efficient manner to maximize the scientific return.

  3. A Hectochelle Radial Velocity Survey of Cep OB3b: An ONC like cluster at late gas dispersal phase

    Science.gov (United States)

    Karnath, Nicole; Allen, Thomas; Prchlik, Jakub; Gutermuth, Robert A.; Megeath, Samuel Thomas; Pipher, Judith; Wolk, Scott J.

    2016-01-01

    Cep OB3b is a young (~3-5 Myr), late gas dispersal cluster of roughly 3000 members broken into two sub-clusters (Eastern and Western) at a distance of 700pc; it is a rare example of nearby cluster in the late stages of gas dispersal and appears to be a more evolved analog to the Orion Nebular Cluster. As part of an ongoing multi wavelength study, we focus on Hectochelle data from the MMT to measure the radial velocities of 499 stars. After removing binaries, outliers, and imposing a minimum R value to the cross correlation, we obtain radial velocities of 57 previously identified members, with an average error of 1.7 km/s. There is no observed variation in radial velocity across the cluster in right ascension or declination. The preferred mechanism for this type of kinematic evolution is that any initial kinematic structure from formation may have been erased and that minimal or no rotation is present in the cluster. However, the Eastern sub-cluster, containing the most massive star in the field, an O7 star, has a higher velocity dispersion than the Western sub-cluster, which contains several B stars. We will compare these results to CO maps of the residual gas in the cluster and discuss possible reasons for this difference. Finally, we will assess whether the cluster is bound or in a state of expansion.

  4. Theoretical fit of Cepheid light an radial velocity curves in the Large Magellanic Cloud cluster NGC 1866

    CERN Document Server

    Marconi, Marcella; Ripepi, Vincenzo; Musella, Ilaria; Brocato, Enzo

    2012-01-01

    We present a theoretical investigation of multifilter (U,B,V, I and K) light and radial velocity curves of five Classical Cepheids in NGC 1866, a young massive cluster of the Large Magellanic Cloud. The best fit models accounting for the luminosity and radial velocity variations of the five selected variables, four pulsating in the fundamental mode and one in the first overtone, provide direct estimates of their intrinsic stellar parameters and individual distances. The resulting stellar properties indicate a slightly brighter Mass Luminosity relation than the canonical one, possibly due to mild overshooting and/or mass loss. As for the inferred distances, the individual values are consistent within the uncertainties. Moreover, their weighted mean value corresponds to a distance modulus of 18.56 + - 0.03 (stat) + - 0.1 (syst) mag, in agreement with several independent results in the literature.

  5. Seven new binaries discovered in the Kepler light curves through the BEER method confirmed by radial-velocity observations

    CERN Document Server

    Faigler, S; Quinn, S N; Latham, D W; Tal-Or, L

    2011-01-01

    We present seven newly discovered non-eclipsing short-period binary systems with low-mass companions, identified by the recently introduced BEER algorithm, applied to the publicly available 138-day photometric light curves obtained by the Kepler mission. The detection is based on the beaming effect (sometimes called Doppler boosting), which increases (decreases) the brightness of any light source approaching (receding from) the observer, enabling a prediction of the stellar Doppler radial-velocity modulation from its precise photometry. The BEER algorithm identifies the BEaming periodic modulation, with a combination of the well known Ellipsoidal and Reflection/heating periodic effects, induced by short-period companions. The seven detections were confirmed by spectroscopic radial-velocity follow-up observations, indicating minimum secondary masses in the range of 0.07-0.4 Msun. The discovered binaries establish for the first time the feasibility of the BEER algorithm as a new detection method for short-perio...

  6. Method of radial velocities for the estimation of aircraft wake vortex parameters from data measured by coherent Doppler lidar.

    Science.gov (United States)

    Smalikho, I N; Banakh, V A; Holzäpfel, F; Rahm, S

    2015-09-21

    The method of radial velocities (RV) is applied to estimate aircraft wake vortex parameters from measurements conducted with pulsed coherent Doppler lidar (PCDL). Operations of the Stream Line lidar and the 2-µm PCDL are simulated numerically to analyze the accuracy of the estimated wake vortex parameters with the RV method. The RV method is also used to estimate wake vortex trajectories and circulation from lidar measurements at Tomsk and Munich airports. The method of velocity envelopes and the RV method are compared employing data gathered with the 2-µm PCDL. The domain of applicability of the RV method is determined.

  7. An updated survey of globular clusters in M 31. I. Classification and radial velocity for 76 candidate clusters

    Science.gov (United States)

    Galleti, S.; Federici, L.; Bellazzini, M.; Buzzoni, A.; Fusi Pecci, F.

    2006-09-01

    Aims.We present the first results of a large spectroscopic survey of globular clusters and candidate globular clusters in the nearby M 31 galaxy. The survey is aimed at the classification of known candidate M 31 clusters and at the study of their kinematic properties. Methods: .We obtained low-resolution spectroscopy (λ/Δλ ≃ 800-1300) for 133 targets, including 76 yet-to-be-confirmed candidate clusters (i.e. with no previous spectroscopic information), 55 already-confirmed genuine M 31 clusters, and 2 uncertain candidates. Our observations allowed a reliable estimate of the target radial velocity, within a typical accuracy of ~± 20 km s-1. The observed candidates have been robustly classified according to their radial velocity and shape parameters that allowed us to confidently discriminate between point sources and extended objects even from low-spatial-resolution imagery. Results: .In our set of 76 candidate clusters we found: 42 newly-confirmed bona-fide M 31 clusters, 12 background galaxies, 17 foreground Galactic stars, 2 Hii regions belonging to M 31 and 3 unclassified (possibly M 31 clusters or foreground stars) objects. The classification of a few other candidates not included in our survey has been also reassessed on various observational bases. All the sources of radial velocity estimates for M 31 known globular clusters available in the literature have been compared and checked, and a homogeneous general list has been obtained for 349 confirmed clusters with radial velocity. Conclusions: .Our results suggest that a significant number of genuine clusters (≳100) is still hidden among the plethora of known candidates proposed by various authors. Hence our knowledge of the globular cluster system of the M 31 galaxy is still far from complete even in terms of simple membership.

  8. High-resolution spectroscopy of RGB stars in the Sagittarius Streams. I. Radial velocities and chemical abundances

    OpenAIRE

    Monaco, L.; Bellazzini, M; Bonifacio, P.; A. Buzzoni; Ferraro, F. R.; Marconi, G; Sbordone, L.; S. Zaggia

    2006-01-01

    Context. The Sagittarius (Sgr) dwarf spheroidal galaxy is currently being disrupted under the strain of the Milky Way. A reliable reconstruction of Sgr star formation history can only be obtained by combining core and stream information. Aims. We present radial velocities for 67 stars belonging to the Sgr Stream. For 12 stars in the sample we also present iron (Fe) and $\\alpha$-element (Mg, Ca) abundances. Methods. Spectra were secured using different high resolution facilities: UVES@VLT, HAR...

  9. Friends of Hot Jupiters I: A Radial Velocity Search for Massive, Long-Period Companions in Hot Jupiter Systems

    CERN Document Server

    Knutson, Heather A; Montet, Benjamin T; Kao, Melodie; Ngo, Henry; Howard, Andrew W; Crepp, Justin R; Hinkley, Sasha; Bakos, Gaspar A; Batygin, Konstantin; Johnson, John Asher; Morton, Timothy D; Muirhead, Philip S

    2013-01-01

    In this paper we search for distant massive companions to known transiting hot Jupiters that may have influenced the dynamical evolution of these systems. We present new radial velocity observations for a sample of 51 hot Jupiters obtained using the Keck HIRES instrument, and use these observations to search for long-term radial velocity accelerations. We find new, statistically significant accelerations in seven systems, including: HAT-P-10, HAT-P-20, HAT-P-22, HAT-P-29, HAT-P-32, WASP-10, and XO-2. We combine our radial velocity fits with Keck NIRC2 AO imaging data to place constraints on the allowed masses and orbital periods of the companions. The estimated masses of the companions range between 1-500 M_Jup, with orbital semi-major axes typically between 1-75 AU. A significant majority of the companions detected by our survey are constrained to have minimum masses comparable to or larger than those of the short-period hot Jupiters in these systems, making them candidates for influencing the orbital evolut...

  10. VizieR Online Data Catalog: Radial velocities of 35 cataclysmic variables (Thorstensen+, 2016)

    Science.gov (United States)

    Thorstensen, J. R.; Alper, E. H.; Weil, K. E.

    2017-02-01

    We present spectroscopic follow-up observations of 35 newly discovered cataclysmic variables (CVs), 32 of which were found by the Catalina Real Time Transient Surveys (CRTS; Drake et al. 2009, Cat. J/ApJ/696/870; Drake et al. 2014, Cat. J/MNRAS/441/1186; Breedt et al. 2014, Cat. J/MNRAS/443/3174), ASAS-SN (Shappee et al. 2014ApJ...788...48S), and/or MASTER (Lipunov et al. 2010AdAst2010E..30L). All our observations are from Michigan-Dartmouth-MIT (MDM) Observatory on Kitt Peak, Arizona. For nearly all the spectra, we used the "modspec" spectrograph (a description of the modspec can be found at http://mdm.kpno.noao.edu/Manuals/ModSpec/modspec_man.html) with a 600line/mm grating. We mostly used a SITe 20482 CCD detector, which yielded 2Å/pixel from 4210 to 7500Å, with declining throughput toward the ends of the spectral range. When this detector was unavailable, we used a very similar 10242 SITe detector ("Templeton"), which covered 4660 to 6730Å. The modspec was mounted mostly on the 2.4m Hiltner telescope, but for some of the brighter objects, we used the 1.3m McGraw-Hill telescope. For a few of the 1.3m spectra, we used the Mark III grism spectrograph, which covered 4580 to 6850Å at 2.3Å/pixel. On both telescopes and with both spectrographs, we used an Andor Ikon camera to view the reflective slit jaws through a microscope and guided the telescope with a separate off-axis guider. With this arrangement we could place any object that was bright enough for a usable spectrum in the slit and track it accurately even if the portion of the light spilling onto the slit jaws was invisible. Our emission-line radial velocities are almost entirely of Hα, since it almost always gives the best signal-to-noise ratio with our instrument. (3 data files).

  11. Hide and Seek: Radial-velocity searches for planets around active stars

    Science.gov (United States)

    Haywood, Raphaelle

    2017-01-01

    The ultimate obstacle to determining the masses of small, rocky exoplanets through radial-velocity (RV) monitoring is the intrinsic variability of the host stars themselves. For my PhD, I developed an intuitive and robust data analysis framework in which the activity-induced variations are modelled with a Gaussian process that has the frequency structure of the stellar magnetic activity. This allowed me to determine precise and accurate masses of the planets in the CoRoT-7, Kepler-78 and Kepler-10 systems. In parallel, I explored the physical origin of activity-induced RV variations of our best-known star: the Sun. I conducted the first systematic RV campaign of the Sun seen as an exoplanet host star using the 3.6m/HARPS spectrograph, by observing sunlight reflected off the bright asteroid 4/Vesta. I used images from the Solar Dynamics Observatory to reconstruct the RV signals incurred by individual surface features such as sunspots, faculae and granulation. I found that the activity-induced RV variations are driven by the suppression of convective blueshift arising dominantly from the presence of faculae. I also identified the full-disc magnetic flux as an excellent proxy for activity-induced RV variations.I am now pursuing my solar investigations using Sun-as-a-star RV observations acquired with the new solar telescope feed at HARPS-N. In particular, I am investigating the impact of magnetic surface features on the shapes of the spectral line profiles, rather than on the RVs themselves (which are a single moment of these lines). This work is key to developing physically-driven, better-tailored models for activity-induced RV variations, in preparation for the potentially habitable, Earth-like planets to be discovered and characterised in the coming years with TESS and GMT/G-CLEF.This work was funded by the Science and Technology Facilities Council in the United Kingdom and the John Templeton Foundation.

  12. Radial-velocity fitting challenge. II. First results of the analysis of the data set

    Science.gov (United States)

    Dumusque, X.; Borsa, F.; Damasso, M.; Díaz, R. F.; Gregory, P. C.; Hara, N. C.; Hatzes, A.; Rajpaul, V.; Tuomi, M.; Aigrain, S.; Anglada-Escudé, G.; Bonomo, A. S.; Boué, G.; Dauvergne, F.; Frustagli, G.; Giacobbe, P.; Haywood, R. D.; Jones, H. R. A.; Laskar, J.; Pinamonti, M.; Poretti, E.; Rainer, M.; Ségransan, D.; Sozzetti, A.; Udry, S.

    2017-02-01

    Context. Radial-velocity (RV) signals arising from stellar photospheric phenomena are the main limitation for precise RV measurements. Those signals induce RV variations an order of magnitude larger than the signal created by the orbit of Earth-twins, thus preventing their detection. Aims: Different methods have been developed to mitigate the impact of stellar RV signals. The goal of this paper is to compare the efficiency of these different methods to recover extremely low-mass planets despite stellar RV signals. However, because observed RV variations at the meter-per-second precision level or below is a combination of signals induced by unresolved orbiting planets, by the star, and by the instrument, performing such a comparison using real data is extremely challenging. Methods: To circumvent this problem, we generated simulated RV measurements including realistic stellar and planetary signals. Different teams analyzed blindly those simulated RV measurements, using their own method to recover planetary signals despite stellar RV signals. By comparing the results obtained by the different teams with the planetary and stellar parameters used to generate the simulated RVs, it is therefore possible to compare the efficiency of these different methods. Results: The most efficient methods to recover planetary signals take into account the different activity indicators, use red-noise models to account for stellar RV signals and a Bayesian framework to provide model comparison in a robust statistical approach. Using the most efficient methodology, planets can be found down to K/N= Kpl/RV_{rms×√{Nobs}=5} with a threshold of K/N = 7.5 at the level of 80-90% recovery rate found for a number of methods. These recovery rates drop dramatically for K/N smaller than this threshold. In addition, for the best teams, no false positives with K/N > 7.5 were detected, while a non-negligible fraction of them appear for smaller K/N. A limit of K/N = 7.5 seems therefore a safe

  13. Photospheric modeling through spectral line inversion. temperature and radial velocity stratifications and fluctuations

    NARCIS (Netherlands)

    Koza, J.; Kucera, A.; Rybák, J.; Wöhl, H.

    2006-01-01

    We aim to determine average radial stratifications of various physical parameters throughout the solar photosphere at high angular resolution for non-magnetic and magnetic areas and to compare these with standard semiempirical 1D modeling and with 3D hydrodynamics (HD) and magnetohydrodynamics (MHD)

  14. High-resolution spectroscopy of RGB stars in the Sagittarius Streams. I. Radial velocities and chemical abundances

    CERN Document Server

    Monaco, L; Bonifacio, P; Buzzoni, A; Ferraro, F R; Marconi, G; Sbordone, L; Zaggia, S

    2006-01-01

    Aims. The Sagittarius (Sgr) dwarf spheroidal galaxy is currently disrupting under the strain of the Milky Way. A reliable reconstructions of Sgr star formation history can only be obtained joining core and stream informations. We present radial velocities for 67 stars belonging to the Sgr Stream. For 12 stars in the sample we also present iron (Fe) and $\\alpha$-element (Mg, Ca) abundances. Methods. Spectra were secured using different high resolution facilities: UVES@VLT, HARPS@3.6m and SARG@TNG. Radial velocities are obtained through cross correlation with a template spectra. Concerning chemical analysis, for the various elements, selected line equivalent widths (EWs) were measured and abundances computed using the WIDTH code and ATLAS model atmospheres. Results. The velocity dispersion of the trailing tail is found to be $\\sigma$=8.3$\\pm$0.9 km s$^{-1}, i.e. significantly lower than in the core of the Sgr galaxy and marginally lower than previous estimates in the same portion of the stream. Stream stars fol...

  15. The SDSS-III APOGEE Radial Velocity Survey of M dwarfs I: Description of Survey and Science Goals

    CERN Document Server

    Deshpande, R; Bender, C F; Mahadevan, S; Terrien, R C; Carlberg, J; Zasowski, G; Crepp, J; Rajpurohit, A S; Reyle, C; Nidever, D L; Schneider, D P; Prieto, C Allende; Bizyaev, D; Ebelke, G; Fleming, S W; Frinchaboy, P M; Ge, J; Hearty, F; Hernandez, J; Malanushenko, E; Malanushenko, V; Majewski, S R; Oravetz, D; Pan, K; Schiavon, R P; Shetrone, M; Simmons, A; Stassun, K G; Wilson, J C; Wisniewski, J

    2013-01-01

    We are carrying out a large ancillary program with the SDSS-III, using the fiber-fed multi-object NIR APOGEE spectrograph, to obtain high-resolution H-band spectra of more than 1200 M dwarfs. These observations are used to measure spectroscopic rotational velocities, radial velocities, physical stellar parameters, and variability of the target stars. Here, we describe the target selection for this survey and results from the first year of scientific observations based on spectra that is publicly available in the SDSS-III DR10 data release. As part of this paper we present RVs and vsini of over 200 M dwarfs, with a vsini precision of ~2 km/s and a measurement floor at vsini = 4 km/s. This survey significantly increases the number of M dwarfs studied for vsini and RV variability (at ~100-200 m/s), and will advance the target selection for planned RV and photometric searches for low mass exoplanets around M dwarfs, such as HPF, CARMENES, and TESS. Multiple epochs of radial velocity observations enable us to iden...

  16. Stress wave velocity patterns in the longitudinal-radial plane of trees for defect diagnosis

    Science.gov (United States)

    Guanghui Li; Xiang Weng; Xiaocheng Du; Xiping Wang; Hailin Feng

    2016-01-01

    Acoustic tomography for urban tree inspection typically uses stress wave data to reconstruct tomographic images for the trunk cross section using interpolation algorithm. This traditional technique does not take into account the stress wave velocity patterns along tree height. In this study, we proposed an analytical model for the wave velocity in the longitudinal–...

  17. VizieR Online Data Catalog: Radial velocities of HD 133131A and HD 133131B (Teske+, 2016)

    Science.gov (United States)

    Teske, J. K.; Shectman, S. A.; Vogt, S. S.; Diaz, M.; Butler, R. P.; Crane, J. D.; Thompson, I. B.; Arriagada, P.

    2017-05-01

    The radial velocity observations of HD133131A and B are part of the large Magellan Planet Search Program, which began in 2002 and is surveying a sample of ~500 of the nearest stars (Clay), 6.5m telescopes at Las Campanas Observatory. In 2010, the survey switched to using the Carnegie Planet Finder Spectrograph (PFS), a temperature-controlled high-resolution echelle spectrograph built for precision radial velocity observations, on Magellan II. Only HD133131A observations from MIKE are included here. Using a 0.35*5'' slit, MIKE provides spectra with R~70000 in the blue and ~50000 in the red and covers 3900-6200Å. Only the red MIKE orders are used for radial velocity determination, while the blue orders provide coverage of the CaIIH and K lines for monitoring stellar activity. The MIKE observations of HD133131A span 2003 June to 2009 July, with total exposure times ranging from 150 to 600s, depending on observing conditions. Both HD133131A and B were observed with PFS, the former observations ranging from 2010 February to 2015 September, and the latter from 2010 August to 2015 September. PFS has a more limited wavelength range than MIKE (3880-6680Å), but still covers the entire iodine wavelength region, CaIIH and K, and Hα. We use a 0.5*2.5'' slit for target observations, providing R~80000 in the iodine region. The total exposure times for the A component range from 285 to 720s, and for the B component range from 282 to 800s. (6 data files).

  18. Metallicities and radial velocities of two stellar clusters located in the outer regions of the Small Magellanic Cloud

    Science.gov (United States)

    Gramajo, L. V.; Parisi, M. C.; Clariá, J. J.; Geisler, D.; Vásquez, S.; Da Costa, G.; Grebel, E. K.

    2016-08-01

    We studied near-infrared spectra of red giant stars in two Small Magellanic Cloud (SMC) clusters. We used the Caii lines to measure radial velocities as well as the equivalent widths of these lines to determine metallicity. The two studied clusters (L32 and L38) are projected on the outer regions of the SMC so they are particularly interesting to examine the possible existence of a change of sign in the metallicity gradient in the outer regions, as suggested by a recent study.

  19. Estimation of the Radial Distribution of the Tangential Velocity in a Vortex Chamber

    Institute of Scientific and Technical Information of China (English)

    Akira OGAWA; Tsuyoshi IKARI; Hiroyuki MURAKAMI; Kouhei SATHO

    2009-01-01

    The estimation of maximum tangential velocity becomes a very important factor for the estimation of performances of the vortex chamber. In this paper, a proposed flow model of how to estimate the maximum tangential velocity in the special form of the vortex chamber is described in detail. The pressure drop basing upon the rapid expansion by flowing from the inlet pipe into the cyclone body is estimated as half of the dynamic pressure in the inlet pipe.

  20. Eclipsing binaries and fast rotators in the Kepler sample. Characterization via radial velocity analysis from Calar Alto

    CERN Document Server

    Lillo-Box, J; Mancini, L; Henning, Th; Figueira, P; Ciceri, S; Santos, N

    2015-01-01

    The Kepler mission has provided high-accurate photometric data in a long time span for more than two hundred thousands stars, looking for planetary transits. Among the detected candidates, the planetary nature of around 15% has been established or validated by different techniques. But additional data is needed to characterize the rest of the candidates and reject other possible configurations. We started a follow-up program to validate, confirm, and characterize some of the planet candidates. In this paper we present the radial velocity analysis (RV) of those presenting large variations, compatible with being eclipsing binaries. We also study those showing large rotational velocities, which prevents us from obtaining the necessary precision to detect planetary-like objects. We present new RV results for 13 Kepler objects of interest (KOIs) obtained with the CAFE spectrograph at the Calar Alto Observatory, and analyze their high-spatial resolution images and the Kepler light curves of some interesting cases. ...

  1. Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter

    CERN Document Server

    Martinez-Arnaiz, R; Montes, D; Eiroa, C; Montesinos, B

    2010-01-01

    Context: Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These spots clearly affect the spectral line profiles and their perturbations alter the line centroids creating a radial velocity jitter that might contaminate" the variations induced by a planet. Precise chromospheric activity measurements are needed to estimate the activity-induced noise that should be expected for a given star. Aims: We obtain precise chromospheric activity measurements and projected rotational velocities for nearby (d < 25 pc) cool (spectral types F to K) stars, to estimate their expected activity-related jitter. As a complementary objective, we attempt to obtain relationships between fluxes in different activity indicator lines, that permit a transformation of traditional activity indicators, i.e, CaII H & K lines, to others that hold noteworthy advanta...

  2. Extrasolar planets and brown dwarfs around A-F type stars - VII. Theta Cygni radial velocity variations: planets or stellar phenomenon?

    CERN Document Server

    Desort, M; Galland, F; Udry, S; Montagnier, G; Beust, H; Boisse, I; Bonfils, X; Bouchy, F; Delfosse, X; Eggenberger, A; Ehrenreich, D; Forveille, T; Hébrard, G; Loeillet, B; Lovis, C; Mayor, M; Meunier, N; Moutou, C; Pepe, F; Perrier, C; Pont, F; Queloz, D; Santos, N C; Ségransan, D; Vidal-Madjar, A

    2009-01-01

    (abridged) In the frame of the search for extrasolar planets and brown dwarfs around early-type main-sequence stars, we present the results obtained on the early F-type star Theta Cygni. Elodie and Sophie at OHP were used to obtain the spectra. Our dedicated radial-velocity measurement method was used to monitor the star's radial velocities over five years. We also use complementary, high angular resolution and high-contrast images taken with PUEO at CFHT. We show that Theta Cygni radial velocities are quasi-periodically variable, with a ~150-day period. These variations are not due to the ~0.35-Msun stellar companion that we detected in imaging at more than 46 AU from the star. The absence of correlation between the bisector velocity span variations and the radial velocity variations for this 7 km/s vsini star, as well as other criteria indicate that the observed radial velocity variations are not due to stellar spots. The observed amplitude of the bisector velocity span variations also seems to rule out ste...

  3. Synthesizing Exoplanet Demographics from Radial Velocity and Microlensing Surveys, II: The Frequency of Planets Orbiting M Dwarfs

    CERN Document Server

    Clanton, Christian

    2014-01-01

    In contrast to radial velocity surveys, results from microlensing surveys indicate that giant planets with masses greater than the critical mass for core accretion ($\\sim 0.1~M_{\\rm Jup}$) are relatively common around low-mass stars. Using the methodology developed in the first paper, we predict the sensitivity of M-dwarf radial velocity (RV) surveys to analogs of the population of planets inferred by microlensing. We find that RV surveys should detect a handful of super-Jovian ($>M_{\\rm Jup}$) planets at the longest periods being probed. These planets are indeed found by RV surveys, implying that the demographic constraints inferred from these two methods are consistent. We combine the results from both methods to estimate planet frequencies spanning wide regions of parameter space. We find that the frequency of Jupiters and super-Jupiters ($1\\lesssim m_p\\sin{i}/M_{\\rm Jup}\\lesssim 13$) with periods $1\\leq P/{\\rm days}\\leq 10^4$ is $f_{\\rm J}=0.029^{+0.013}_{-0.015}$, a median factor of 4.3 ($1.5-14$ at 95% ...

  4. Orbital structure of the GJ876 extrasolar planetary system, based on the latest Keck and HARPS radial velocity data

    CERN Document Server

    Baluev, Roman V

    2011-01-01

    We use full available array of radial velocity data, including recently published HARPS and Keck observatory sets, to characterize the orbital configuration of the planetary system orbiting GJ876. First, we propose and describe in detail a fast method to fit perturbed orbital configuration, based on the integration of the sensitivity equations inferred by the equations of the original $N$-body problem. Further, we find that it is unsatisfactory to treat the available radial velocity data for GJ876 in the traditional white noise model, because the actual noise appears autocorrelated (and demonstrates non-white frequency spectrum). The time scale of this correlation is about a few days, and the contribution of the correlated noise is about 2 m/s (i.e., similar to the level of internal errors in the Keck data). We propose a variation of the maximum-likelihood algorithm to estimate the orbital configuration of the system, taking into account the red noise effects. We show, in particular, that the non-zero orbital...

  5. An updated survey of globular clusters in M 31. I. Classification and radial velocity for 76 candidate clusters

    CERN Document Server

    Galleti, S; Bellazzini, M; Buzzoni, A; Pecci, F F

    2006-01-01

    Aims - We present the first results of a large spectroscopic survey of globular clusters and candidate globular clusters in the nearby M~31 galaxy. The survey is aimed at the classification of known candidate M~31 clusters and at the study of their kinematic properties. Methods - We obtained low-resolution spectroscopy (lambda/Dlambda~800-1300) for 133 targets, including 76 yet-to-confirm candidate clusters (i.e. with no previous spectroscopic information), 55 already-confirmed genuine M31 clusters, and 2 uncertain candidates. Our observations allowed a reliable estimate of the target radial velocity, within a typical accuracy of ~+-20km/s. The observed candidates have been robustly classified according to their radial velocity and shape parameters that allowed us to confidently discriminate between point sources and extended objects even from low-spatial-resolution imagery. Results - In our set of 76 candidates clusters we found: 42 newly-confirmed bona-fide M~31 clusters, 12 background galaxies, 17 foregrou...

  6. A rubidium-traced white-light etalon calibrator for radial velocity measurements at the cm/s level

    CERN Document Server

    Stürmer, Julian; Schwab, Christian; Bean, Jacob L

    2016-01-01

    We report on the construction and testing of a vacuum-gap Fabry-P\\'erot etalon calibrator for high precision radial velocity spectrographs. Our etalon is traced against a rubidium frequency standard to provide a cost effective, yet ultra-precise wavelength reference. We describe here a turn-key system working at 500 nm to 900 nm, ready to be installed at any current and next generation radial velocity spectrograph that requires calibration over a wide spectral bandpass. Where appropriate, we have used off-the-shelf, commercial components with demonstrated long-term performance to accelerate the development timescale of this instrument. Our system combines for the first time the advantages of passively stabilized etalons for optical and near-infrared wavelengths with the laser-locking technique demonstrated for single-mode fiber etalons. We realize uncertainties in the position of one etalon line at the 10 cm/s level in individual measurements taken at 4 Hz. When binning the data over 10 s, we are able to trac...

  7. The Space Interferometry Mission Astrometric Grid Giant-Star Survey. I. Stellar Parameters and Radial Velocity Variability

    CERN Document Server

    Bizyaev, D; Cunha, K; Geisler, D; Gieren, W; Majewski, S R; Pardo, C D; Patterson, R J; Smith, V V; Suntzeff, N B; Arenas, Jose; Bizyaev, Dmitry; Cunha, Katia; Geisler, Doug; Gieren, Wolfgang; Majewski, Steven R.; Pardo, Cecilia Del; Patterson, Richard J.; Smith, Verne V.; Suntzeff, Nicholas B.

    2005-01-01

    We present results from a campaign of multiple epoch echelle spectroscopy of relatively faint (V = 9.5-13.5 mag) red giants observed as potential astrometric grid stars for the Space Interferometry Mission (SIM PlanetQuest). Data are analyzed for 775 stars selected from the Grid Giant Star Survey spanning a wide range of effective temperatures (Teff), gravities and metallicities. The spectra are used to determine these stellar parameters and to monitor radial velocity (RV) variability at the 100 m/s level. The degree of RV variation measured for 489 stars observed two or more times is explored as a function of the inferred stellar parameters. The percentage of radial velocity unstable stars is found to be very high -- about 2/3 of our sample. It is found that the fraction of RV-stable red giants (at the 100 m/s level) is higher among stars with Teff \\sim 4500 K, corresponding to the calibration-independent range of infrared colors 0.59 < (J-K_s)_0 < 0.73. A higher percentage of RV-stable stars is found ...

  8. High-resolution spectroscopy of RGB stars in the Sagittarius streams. I. Radial velocities and chemical abundances

    Science.gov (United States)

    Monaco, L.; Bellazzini, M.; Bonifacio, P.; Buzzoni, A.; Ferraro, F. R.; Marconi, G.; Sbordone, L.; Zaggia, S.

    2007-03-01

    Context: The Sagittarius (Sgr) dwarf spheroidal galaxy is currently being disrupted under the strain of the Milky Way. A reliable reconstruction of Sgr star formation history can only be obtained by combining core and stream information. Aims: We present radial velocities for 67 stars belonging to the Sgr Stream. For 12 stars in the sample we also present iron (Fe) and α-element (Mg, Ca) abundances. Methods: Spectra were secured using different high resolution facilities: UVES@VLT, HARPS@3.6 m, and SARG@TNG. Radial velocities are obtained through cross correlation with a template spectra. Concerning chemical analysis, for the various elements, selected line equivalent widths were measured and abundances computed using the WIDTH code and ATLAS model atmospheres. Results: The velocity dispersion of the trailing tail is found to be σ = 8.3 ± 0.9 km s-1, i.e., significantly lower than in the core of the Sgr galaxy and marginally lower than previous estimates in the same portion of the stream. Stream stars follow the same trend as Sgr main body stars in the [ α/Fe] vs. [Fe/H] plane. However, stars are, on average, more metal poor in the stream than in the main body. This effect is slightly stronger in stars belonging to more ancient wraps of the stream, according to currently accepted models of Sgr disruption. Based on observations taken at ESO VLT Kueyen telescope (Cerro Paranal, Chile, program: 075.B-0127(A)) and 3.6 m telescope (La Silla, Chile). Also based on spectroscopic observations taken at the Telescopio Nazionale Galileo, operated by the Fundación G. Galilei of INAF at the Spanish Observatorio del Roque de los Muchachos of the IAC (La Palma, Spain). Appendix A and Table [see full text] are only available in electronic form at http://www.aanda.org

  9. Where are the Binaries? Results of a Long-term Search for Radial Velocity Binaries in Proto-planetary Nebulae

    Science.gov (United States)

    Hrivnak, Bruce J.; Van de Steene, Griet; Van Winckel, Hans; Sperauskas, Julius; Bohlender, David; Lu, Wenxian

    2017-09-01

    We present the results of an expanded, long-term radial velocity search (25 years) for evidence of binarity in a sample of seven bright proto-planetary nebulae (PPNe). The goal is to investigate the widely held view that the bipolar or point-symmetric shapes of planetary nebulae (PNe) and PPNe are due to binary interactions. Observations from three observatories were combined from 2007 to 2015 to search for variations on the order of a few years and then combined with earlier observations from 1991 to 1995 to search for variations on the order of decades. All seven show velocity variations due to periodic pulsation in the range of 35–135 days. However, in only one PPN, IRAS 22272+5435, did we find even marginal evidence for multi-year variations that might be due to a binary companion. This object shows marginally significant evidence of a two-year period of low semi-amplitude, which could be due to a low-mass companion, and it also displays some evidence of a much longer period of >30 years. The absence of evidence in the other six objects for long-period radial velocity variations due to a binary companion sets significant constraints on the properties of any undetected binary companions: they must be of low mass, ≤0.2 M ⊙, or long period, >30 years. Thus the present observations do not provide direct support for the binary hypothesis to explain the shapes of PNe and PPNe and severely constrains the properties of any such undetected companions.

  10. VizieR Online Data Catalog: M4 Core Project with HST. Radial velocities (Malavolta+, 2015)

    Science.gov (United States)

    Malavolta, L.; Piotto, G.; Bedin, L. R.; Sneden, C.; Nascimbeni, V.; Sommariva, V.

    2016-07-01

    The spectra for our project were originally used by Sommariva et al. (2009A&A...493..947S) to study the internal velocity dispersion of M4 and to search for spectroscopic binaries. A total of 2771 stars covering colour-magnitude diagram (CMD) positions from the upper RGB to about 1mag fainter than the main-sequence turnoff (TO) luminosity were observed between 2003 and 2009, including 306 new spectra obtained in 2009 and targeting MS stars already observed in the previous epochs. Determination of the M 4 velocity dispersion and binary star fraction were the prime motivators for obtaining these data. Therefore nearly all stars were observed at least twice, and three or more spectra were obtained for nearly 40 per cent of the sample. (2 data files).

  11. Detection, photometry and slitless radial velocities of 535 planetary nebulae in the flattened elliptical galaxy NGC 4697

    CERN Document Server

    Méndez, R H; Kudritzki, R P; Matthias, M; Freeman, K C; Arnaboldi, M; Capaccioli, M; Gerhard, O E

    2001-01-01

    We have detected 535 planetary nebulae (PNs) in NGC 4697, using the classic on-band, off-band filter technique with the Focal Reducer and Spectrograph (FORS) at the Cassegrain focus of the first 8-meter telescope unit of the ESO Very Large Telescope. From our photometry we have built the [O III] 5007 planetary nebula luminosity function (PNLF) of NGC 4697. It indicates a distance of 10.5 Mpc, substantially smaller than a previous estimate of 24 Mpc used in earlier dynamical studies. The PNLF also provides an estimate of the specific PN formation rate. Combining the information from on-band images with PN positions on dispersed, slitless grism images, we have obtained radial velocities for 531 of the 535 PNs. They provide kinematic information up to a distance of almost three effective radii from the nucleus. Some rotation is detected in the outer regions, but the rotation curve of this galaxy appears to drop beyond one effective radius. Assuming an isotropic velocity distribution, the velocity dispersion prof...

  12. The Radial Velocity Profiles of some Proplyds in the Orion Nebula

    Directory of Open Access Journals (Sweden)

    E. de la Fuente

    2003-01-01

    Full Text Available Usamos los datos obtenidos con un interferómetro de Fabry-Perot de barrido en la parte central de la Nebulosa de Orión para estudiar los proplyds de esta región. Encontramos que la interferometría de Fabry-Perot es una técnica efectiva para detectar e identificar a los proplyds. Muchos proplyds y objetos candidatos se detectan sólo después de aplicar técnicas de procesamiento a los cubos de velocidades de Fabry-Perot. Adicionalmente, presentamos los perfiles de velocidad radial, sustraídos de la región H II, de la mayoría de los proplyds detectados (13, así como de los candidatos (3. A partir de éstos, estimamos las propiedades cinemáticas más importantes de estos objetos. Encontramos que todos los proplyds tienen velocidades corridas al rojo con respecto a la Nebulosa de Orión. Encontramos también que los proplyds que estudiamos tienen valores típicos de pérdida de masa y de escala temporal del disco y discutimos las implicaciones de esto, tomando en cuenta que nuestro estudio es sobre una buena proporción de proplyds. Finalmente, vemos que nuestros perfiles de velocidad sugieren que una buena fracción de proplyds presentan microjets monopolares.

  13. An astro-comb calibrated solar telescope to study solar activity and search for the radial velocity signature of Venus

    Science.gov (United States)

    Phillips, David; HARPS-N Collaboration

    2017-01-01

    We recently demonstrated sub-m/s sensitivity in measuring the radial velocity (RV) between the Earth and Sun using a simple solar telescope feeding the HARPS-N spectrograph at the Italian National Telescope, which is calibrated with a laser frequency comb calibrator optimized for calibrating high resolution spectrographs and referred to as an astro-comb. We are using the solar telescope to characterize the effects of stellar (solar) RV jitter due to activity on the solar surface over the course of many hours every clear day. With the help of solar satellites such as the Solar Dynamics Observatory (SDO), we are characterizing the correlation between observed RV and detailed imaging of the solar photosphere. We plan to use these tools to mitigate the effects of stellar jitter with the goal of the detection of Venus from its solar RV signature, thus showing the potential of the RV technique to detect true Earth-twins.

  14. A Quick Study of the Characterization of Radial Velocity Giant Planets in Reflected Light by Forward and Inverse Modeling

    CERN Document Server

    Marley, Mark; Lewis, Nikole; Line, Michael; Morley, Caroline; Fortney, Jonathan

    2014-01-01

    We explored two aspects of the problem of characterizing cool extrasolar giant planets in scattered optical light with a space based coronagraph. First, for a number of the known radial velocity (RV) giants we computed traditional forward models of their atmospheric structure and clouds, given various input assumptions, and computed model albedo spectra. Such models have been computed before, but mostly for generic planets. Our new models demonstrate that there is likely interesting spectral diversity among those planets that are most favorable for direct detection. Second, we applied a powerful Markov Chain Monte Carlo (MCMC) retrieval technique to synthetic noisy data of cool giants to better understand how well various atmospheric parameters--particularly molecular abundances and cloud properties--could be constrained. This is the first time such techniques have been applied to this problem. The process is time consuming, so only a dozen or so cases could be completed in the limited time available. Neverth...

  15. Predicted Space Motions for Hypervelocity and Runaway Stars: Proper Motions and Radial Velocities for the GAIA Era

    CERN Document Server

    Kenyon, Scott J; Brown, Warren R; Geller, Margaret J

    2014-01-01

    We predict the distinctive three dimensional space motions of hypervelocity stars (HVSs) and runaway stars moving in a realistic Galactic potential. For nearby stars with distances less than 10~kpc, unbound stars are rare; however, proper motions isolate bound HVSs and runaways from indigenous halo stars. Towards the Galactic Center, high proper motion stars are a unique signature of HVSs or runaways. At larger distances of 20-100 kpc, unbound HVSs are much more common than runaways; radial velocities easily distinguish both from indigenous halo stars. Comparisons of the predictions with existing observations are encouraging. Although the models fail to match observations of solar-type HVS candidates from SEGUE, they agree well with data for B-type HVS and runaways from other surveys. Complete samples of g <= 20 stars with GAIA should provide clear tests of formation models for HVSs and runaways and will enable accurate probes of the shape of the Galactic potential.

  16. Predicted space motions for hypervelocity and runaway stars: proper motions and radial velocities for the Gaia Era

    Energy Technology Data Exchange (ETDEWEB)

    Kenyon, Scott J.; Brown, Warren R.; Geller, Margaret J. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Bromley, Benjamin C., E-mail: skenyon@cfa.harvard.edu, E-mail: wbrown@cfa.harvard.edu, E-mail: mgeller@cfa.harvard.edu, E-mail: bromley@physics.utah.edu [Department of Physics, University of Utah, 115 S 1400 E, Rm 201, Salt Lake City, UT 84112 (United States)

    2014-10-01

    We predict the distinctive three-dimensional space motions of hypervelocity stars (HVSs) and runaway stars moving in a realistic Galactic potential. For nearby stars with distances less than 10 kpc, unbound stars are rare; proper motions alone rarely isolate bound HVSs and runaways from indigenous halo stars. At large distances of 20-100 kpc, unbound HVSs are much more common than runaways; radial velocities easily distinguish both from indigenous halo stars. Comparisons of the predictions with existing observations are encouraging. Although the models fail to match observations of solar-type HVS candidates from SEGUE, they agree well with data for B-type HVS and runaways from other surveys. Complete samples of g ≲ 20 stars with Gaia should provide clear tests of formation models for HVSs and runaways and will enable accurate probes of the shape of the Galactic potential.

  17. Radial velocity confirmation of Kepler-91 b. Additional evidence of its planetary nature using the Calar Alto/CAFE instrument

    CERN Document Server

    Lillo-Box, J; Henning, Th; Mancini, L; Ciceri, S; Figueira, P; Santos, N C; Aceituno, J; Sánchez, S

    2014-01-01

    The object transiting the star Kepler-91 was recently assessed as being of planetary nature. The confirmation was achieved by analysing the light-curve modulations observed in the Kepler data. However, quasi-simultaneous studies claimed a self-luminous nature for this object, thus rejecting it as a planet. In this work, we apply an {independent} approach to confirm the planetary mass of Kepler-91b by using multi-epoch high-resolution spectroscopy obtained with the Calar Alto Fiber-fed Echelle spectrograph (CAFE). We obtain the physical and orbital parameters with the radial velocity technique. In particular, we derive a value of $1.09 \\pm 0.20\\,M_{\\mathrm{Jup}}$ for the mass of Kepler-91b, in excellent agreement with our previous estimate that was based on the orbital brightness modulation.

  18. Radial velocity confirmation of Kepler-91 b. Additional evidence of its planetary nature using the Calar Alto/CAFE instrument

    Science.gov (United States)

    Lillo-Box, J.; Barrado, D.; Henning, Th.; Mancini, L.; Ciceri, S.; Figueira, P.; Santos, N. C.; Aceituno, J.; Sánchez, S. F.

    2014-08-01

    The object transiting the star Kepler-91 was recently assessed as being of planetary nature. The confirmation was achieved by analysing the light-curve modulations observed in the Kepler data. However, quasi-simultaneous studies claimed a self-luminous nature for this object, thus rejecting it as a planet. In this work, we apply anindependent approach to confirm the planetary mass of Kepler-91b by using multi-epoch high-resolution spectroscopy obtained with the Calar Alto Fiber-fed Echelle spectrograph (CAFE). We obtain the physical and orbital parameters with the radial velocity technique. In particular, we derive a value of 1.09 ± 0.20 MJup for the mass of Kepler-91b, in excellent agreement with our previous estimate that was based on the orbital brightness modulation.

  19. Tuning in on Cepheids: Radial velocity amplitude modulations. A source of systematic uncertainty for Baade-Wesselink distances

    CERN Document Server

    Anderson, Richard I

    2014-01-01

    [Abridged] I report the discovery of modulations in radial velocity (RV) curves of four Galactic classical Cepheids and investigate their impact as a systematic uncertainty for Baade-Wesselink distances. Highly precise Doppler measurements were obtained using the Coralie high-resolution spectrograph since 2011. Particular care was taken to sample all phase points in order to very accurately trace the RV curve during multiple epochs and to search for differences in linear radius variations derived from observations obtained at different epochs. Different timescales are sampled, ranging from cycle-to-cycle to months and years. The unprecedented combination of excellent phase coverage obtained during multiple epochs and high precision enabled the discovery of significant modulation in the RV curves of the short-period s-Cepheids QZ Normae and V335 Puppis, as well as the long-period fundamental mode Cepheids l Carinae and RS Puppis. The modulations manifest as shape and amplitude variations that vary smoothly on ...

  20. “MODAL NOISE” IN SINGLE-MODE FIBERS: A CAUTIONARY NOTE FOR HIGH PRECISION RADIAL VELOCITY INSTRUMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Halverson, Samuel; Roy, Arpita; Mahadevan, Suvrath [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Schwab, Christian, E-mail: shalverson@psu.edu [Macquarie University, Sydney, NSW 2109 (Australia)

    2015-12-01

    Exploring the use of single-mode fibers (SMFs) in high precision Doppler spectrometers has become increasingly attractive since the advent of diffraction-limited adaptive optics systems on large-aperture telescopes. Spectrometers fed with these fibers can be made significantly smaller than typical “seeing-limited” instruments, greatly reducing cost and overall complexity. Importantly, classical mode interference and speckle issues associated with multi-mode fibers, also known as “modal noise,” are mitigated when using SMFs, which also provide perfect radial and azimuthal image scrambling. However, SMFs do support multiple polarization modes, an issue that is generally ignored for larger-core fibers given the large number of propagation modes. Since diffraction gratings used in most high resolution astronomical instruments have dispersive properties that are sensitive to incident polarization changes, any birefringence variations in the fiber can cause variations in the efficiency profile, degrading illumination stability. Here we present a cautionary note outlining how the polarization properties of SMFs can affect the radial velocity (RV) measurement precision of high resolution spectrographs. This work is immediately relevant to the rapidly expanding field of diffraction-limited, extreme precision RV spectrographs that are currently being designed and built by a number of groups.

  1. The VMC survey - XXIII. Model fitting of light and radial velocity curves of Small Magellanic Cloud classical Cepheids

    Science.gov (United States)

    Marconi, M.; Molinaro, R.; Ripepi, V.; Cioni, M.-R. L.; Clementini, G.; Moretti, M. I.; Ragosta, F.; de Grijs, R.; Groenewegen, M. A. T.; Ivanov, V. D.

    2017-04-01

    We present the results of the χ2 minimization model fitting technique applied to optical and near-infrared photometric and radial velocity data for a sample of nine fundamental and three first overtone classical Cepheids in the Small Magellanic Cloud (SMC). The near-infrared photometry (JK filters) was obtained by the European Southern Observatory (ESO) public survey 'VISTA near-infrared Y, J, Ks survey of the Magellanic Clouds system' (VMC). For each pulsator, isoperiodic model sequences have been computed by adopting a non-linear convective hydrodynamical code in order to reproduce the multifilter light and (when available) radial velocity curve amplitudes and morphological details. The inferred individual distances provide an intrinsic mean value for the SMC distance modulus of 19.01 mag and a standard deviation of 0.08 mag, in agreement with the literature. Moreover, the intrinsic masses and luminosities of the best-fitting model show that all these pulsators are brighter than the canonical evolutionary mass-luminosity relation (MLR), suggesting a significant efficiency of core overshooting and/or mass-loss. Assuming that the inferred deviation from the canonical MLR is only due to mass-loss, we derive the expected distribution of percentage mass-loss as a function of both the pulsation period and the canonical stellar mass. Finally, a good agreement is found between the predicted mean radii and current period-radius (PR) relations in the SMC available in the literature. The results of this investigation support the predictive capabilities of the adopted theoretical scenario and pave the way for the application to other extensive data bases at various chemical compositions, including the VMC Large Magellanic Cloud pulsators and Galactic Cepheids with Gaia parallaxes.

  2. Photoelectric Radial Velocities, Paper XVIII Spectroscopic Orbits for Another 52 Binaries in the Hyades Field

    Indian Academy of Sciences (India)

    R. F. Griffin

    2012-03-01

    Spectroscopic orbits are presented for 52 stars in the Hyades field, of which 41 prove to be actual members of the Hyades (with some reservations in two cases). Most of the stars concerned have not had orbits published for them previously. Three of them are of higher multiplicity. The already-known double-lined eclipsing system van Bueren 22 is demonstrated to be a triple system, as was obliquely announced 25 years ago; its `outer’ orbit, which has a period of about 8 years, is now determined. Van Bueren 75 is already known to be triple, but here the visual secondary is shown to be the (single-lined) spectroscopic sub-system, and an independent spectroscopic solution is given for the 40-year orbit of what has hitherto been regarded as the `visual’ pair. Van Bueren 102, for which a close visual companion was discovered comparatively recently, is a single-lined binary whose -velocity has shown a steady drift over at least the last 30 (probably 50) years. Three stars, vB 39, 50 and 59, have notably high eccentricities of 0.85, 0.98 and 0.94, respectively; they have quite long periods (especially vB 50, which is over 100 years), and every one of them contrived to pass the whole of its recent periastron passage (about 180° of true anomaly) between seasons, at the time of year when the Hyades are unobservable!

  3. Rotational and radial velocities of 1.3-2.2 M {sub ☉} red giants in open clusters

    Energy Technology Data Exchange (ETDEWEB)

    Carlberg, Joleen K., E-mail: jcarlberg@dtm.ciw.edu [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015 (United States)

    2014-06-01

    This study presents the rotational distribution of red giant (RG) stars in 11 old to intermediate age open clusters. The masses of these stars are all above the Kraft break, so they lose negligible amounts of their birth angular momentum (AM) during the main-sequence (MS) evolution. However, they do span a mass range with quite different AM distributions imparted during formation, with the stars less massive than ∼1.6M {sub ☉} arriving on the MS with lower rotation rates than the more massive stars. The majority of RGs in this study are slow rotators across the entire red giant branch regardless of mass, supporting the picture that intermediate-mass stars rapidly spin down when they evolve off the MS and develop convection zones capable of driving a magnetic dynamo. Nevertheless, a small fraction of RGs in open clusters show some level of enhanced rotation, and faster rotators are as common in these clusters as in the field RG population. Most of these enhanced rotators appear to be red clump stars, which is also true of the underlying stellar sample, while others are clearly RGs that are above or below the clump. In addition to rotational velocities, the radial velocities (RVs) and membership probabilities of individual stars are also presented. Cluster heliocentric RVs for NGC 6005 and Pismis 18 are reported for the first time.

  4. Detection of the 128 day radial velocity variations in the supergiant {\\alpha} Persei. Rotational modulations, pulsations, or a planet?

    CERN Document Server

    Lee, Byeong-Cheol; Park, Myeong-Gu; Kim, Kang-Min; Mkrtichian, David E

    2012-01-01

    Aims. In order to search for and study the nature of the low-amplitude and long-periodic radial velocity (RV) variations of massive stars, we have been carrying out a precise RV survey for supergiants that lie near or inside the Cepheid instability strip. Methods. We have obtained high-resolution spectra of {\\alpha} Per (F5 Ib) from November 2005 to September 2011 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory (BOAO). Results. Our measurements reveal that {\\alpha} Per shows a periodic RV variation of 128 days and a semi-amplitude of 70 m/s. We find no strong correlation between RV variations and bisector velocity span (BVS), but the 128-d peak is indeed present in the BVS variations among several other significant peaks in periodogram. Conclusions. {\\alpha} Per may have an exoplanet, but the combined data spanning over 20 years seem to suggest that the 128-d RV variations have not been stable on long-term scale, which is somewhat difficult to r...

  5. The Sun as a planet-host star: Proxies from SDO images for HARPS radial-velocity variations

    CERN Document Server

    Haywood, R D; Unruh, Y C; Lovis, C; Lanza, A F; Llama, J; Deleuil, M; Fares, R; Gillon, M; Moutou, C; Pepe, F; Pollacco, D; Queloz, D; Segransan, D

    2016-01-01

    The Sun is the only star whose surface can be directly resolved at high resolution, and therefore constitutes an excellent test case to explore the physical origin of stellar radial-velocity (RV) variability. We present HARPS observations of sunlight scattered off the bright asteroid 4/Vesta, from which we deduced the Sun's activity-driven RV variations. In parallel, the HMI instrument onboard the Solar Dynamics Observatory provided us with simultaneous high spatial resolution magnetograms, Dopplergrams, and continuum images of the Sun in the Fe I 6173A line. We determine the RV modulation arising from the suppression of granular blueshift in magnetised regions and the flux imbalance induced by dark spots and bright faculae. The rms velocity amplitudes of these contributions are 2.40 m/s and 0.41 m/s, respectively, which confirms that the inhibition of convection is the dominant source of activity-induced RV variations at play, in accordance with previous studies. We find the Doppler imbalances of spot and pl...

  6. Low-amplitude and long-period radial velocity variations in giants HD 3574, 63 Cygni, and HD 216946 (Research Note)

    CERN Document Server

    Lee, B -C; Park, M -G; Hatzes, A P; Kim, K -M

    2014-01-01

    Aims. We study the low-amplitude and long-period variations in evolved stars using precise radial velocity measurements. Methods. The high-resolution, fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) was used from September 2004 to May 2014 as part of the exoplanet search program at the Bohyunsan Optical Astronomy Observatory (BOAO). Results. We report the detection of low-amplitude and long-period orbital radial velocity variations in three evolved stars, HD 3574, 63 Cyg, and HD 216946. They have periods of 1061, 982, and 1382 days and semi-amplitudes of 376, 742, and 699 m/s, respectively.

  7. G 112-29 (=NLTT 18149), a Very Wide Companion to GJ 282 AB with a Common Proper Motion, Common Parallax, Common Radial Velocity and Common Age

    CERN Document Server

    Poveda, A; Costero, R; Echevarria, J; Hernandez-Alcantara, A

    2009-01-01

    We have made a search for common proper motion (CPM) companions to the wide binaries in the solar vicinity. We found that the binary GJ 282AB has a very distant CPM companion (NLTT 18149) at a separation $s=1.09 \\arcdeg$. Improved spectral types and radial velocities are obtained, and ages determined for the three components. The Hipparcos trigonometric parallaxes and the new radial velocities and ages turn out to be very similar for the three stars, and provide strong evidence that they form a physical system. At a projected separation of 55733AU from GJ 282AB, NLTT 18149 ranks among the widest physical companions known.

  8. Radial velocity observations of the 2015 Mar. 20 eclipse. A benchmark Rossiter-McLaughlin curve with zero free parameters

    Science.gov (United States)

    Reiners, A.; Lemke, U.; Bauer, F.; Beeck, B.; Huke, P.

    2016-10-01

    Spectroscopic observations of a solar eclipse can provide unique information for solar and exoplanet research; the huge amplitude of the Rossiter-McLaughlin (RM) effect during solar eclipse and the high precision of solar radial velocities (RVs) allow detailed comparison between observations and RV models, and they provide information about the solar surface and about spectral line formation that are otherwise difficult to obtain. On March 20, 2015, we obtained 159 spectra of the Sun as a star with the solar telescope and the Fourier Transform Spectrograph at the Institut für Astrophysik Göttingen, 76 spectra were taken during partial solar eclipse. We obtained RVs using I2 as wavelength reference and determined the RM curve with a peak-to-peak amplitude of almost 1.4 km s-1 at typical RV precision better than 1 m s-1. We modeled the disk-integrated solar RVs using well-determined parameterizations of solar surface velocities, limb darkening, and information about convective blueshift from 3D magnetohydrodynamic simulations. We confirm that convective blueshift is crucial to understand solar RVs during eclipse. Our best model reproduced the observations to within a relative precision of 10% with residuals lower than 30 m s-1. We cross-checked parameterizations of velocity fields using a Dopplergram from the Solar Dynamics Observatory and conclude that disk-integration of the Dopplergram does not provide correct information about convective blueshift necessary for m s-1 RV work. As main limitation for modeling RVs during eclipses, we identified limited knowledge about convective blueshift and line shape as functions of solar limb angle. We suspect that our model line profiles are too shallow at limb angles larger than μ = 0.6, resulting in incorrect weighting of the velocities across the solar disk. Alternative explanations cannot be excluded, such as suppression of convection in magnetic areas and undiscovered systematics during eclipse observations. To make

  9. The radial velocity dispersion profile of the Galactic halo : constraining the density profile of the dark halo of the Milky Way

    NARCIS (Netherlands)

    Battaglia, G; Helmi, A; Morrison, H; Harding, P; Olszewski, EW; Mateo, M; Freeman, KC; Norris, J; Shectman, SA

    2005-01-01

    We have compiled a new sample of 240 halo objects with accurate distance and radial velocity measurements, including globular clusters, satellite galaxies, field blue horizontal branch (FHB) stars and red giant stars from the Spaghetti survey. The new data lead to a significant increase in the numbe

  10. Radial Velocity Prospects Current and Future: A White Paper Report prepared by the Study Analysis Group 8 for the Exoplanet Program Analysis Group (ExoPAG)

    CERN Document Server

    Plavchan, Peter; Gaudi, Scott; Crepp, Justin; Xavier, Dumusque; Furesz, Gabor; Vanderburg, Andrew; Blake, Cullen; Fischer, Debra; Prato, Lisa; White, Russel; Makarov, Valeri; Marcy, Geoff; Stapelfeldt, Karl; Haywood, Raphaëlle; Collier-Cameron, Andrew; Quirrenbach, Andreas; Mahadevan, Suvrath; Anglada, Guillem; Muirhead, Philip

    2015-01-01

    [Abridged] The Study Analysis Group 8 of the NASA Exoplanet Analysis Group was convened to assess the current capabilities and the future potential of the precise radial velocity (PRV) method to advance the NASA goal to "search for planetary bodies and Earth-like planets in orbit around other stars.: (U.S. National Space Policy, June 28, 2010). PRVs complement other exoplanet detection methods, for example offering a direct path to obtaining the bulk density and thus the structure and composition of transiting exoplanets. Our analysis builds upon previous community input, including the ExoPlanet Community Report chapter on radial velocities in 2008, the 2010 Decadal Survey of Astronomy, the Penn State Precise Radial Velocities Workshop response to the Decadal Survey in 2010, and the NSF Portfolio Review in 2012. The radial-velocity detection of exoplanets is strongly endorsed by both the Astro 2010 Decadal Survey "New Worlds, New Horizons" and the NSF Portfolio Review, and the community has recommended robust...

  11. The radial velocity dispersion profile of the Galactic halo : constraining the density profile of the dark halo of the Milky Way

    NARCIS (Netherlands)

    Battaglia, G; Helmi, A; Morrison, H; Harding, P; Olszewski, EW; Mateo, M; Freeman, KC; Norris, J; Shectman, SA

    2005-01-01

    We have compiled a new sample of 240 halo objects with accurate distance and radial velocity measurements, including globular clusters, satellite galaxies, field blue horizontal branch (FHB) stars and red giant stars from the Spaghetti survey. The new data lead to a significant increase in the numbe

  12. SOAP 2.0: A tool to estimate the photometric and radial velocity variations induced by stellar spots and plages

    CERN Document Server

    Dumusque, X; Santos, N C

    2014-01-01

    This paper presents SOAP 2.0, a new version of the SOAP code that estimates in a simple way the photometric and radial velocity variations induced by active regions. The inhibition of the convective blueshift inside active regions is considered, as well as the limb brightening effect of plages, a quadratic limb darkening law, and a realistic spot and plage contrast ratio. SOAP 2.0 shows that the activity-induced variation of plages is dominated by the inhibition of the convective blueshift effect. For spots, this effect becomes significant only for slow rotators. In addition, in the case of a major active region dominating the activity-induced signal, the ratio between the full width at half maximum (FWHM) and the RV peak-to-peak amplitudes of the cross correlation function can be used to infer the type of active region responsible for the signal for stars with \\vsini$\\le8$\\kms. A ratio smaller than three implies a spot, while a larger ratio implies a plage. Using the observation of HD189733, we show that SOA...

  13. The effects of ischemia with and without remote conditioning on hyperemia induced decline in carotid-radial pulse wave velocity.

    Science.gov (United States)

    Onegbu, Nwamaka; Kamran, Haroon; Sharma, Bhawna; Bapat, Manasi; Littman, Stephen; Warrier, Nikhil; Patel, Rinkesh; Khalid, Muhammad Tanweer; Salciccioli, Louis; Lazar, Jason M

    2012-01-01

    Ischemic conditioning has long held promise for preventing ischemic-reperfusion (I-R) injury. Although a number of studies have evaluated the effects of brief repeated episodes of ischemia before a prolonged ischemic episode on the cardiovascular system using clinical endpoints, more sensitive techniques by which to measure its effects are lacking. Since endothelial function is sensitive to I-R injury, flow mediated dilation of the brachial artery has been proposed for this purpose, but has significant limitations. Hyperemia normally decreases carotid to radial pulse wave velocity (PWV). Accordingly, we sought to determine the effects of I-R injury and ischemic conditioning on the hyperemic change (Δ) in PWV. We induced hyperemia by release of arterial cuff occlusion before and after ipsilateral arm I-R injury (7.5min occlusion) in 25 healthy males, age 29±6 years. The protocol was repeated on 2 occasions in combination with either pre- or post- conditioning stimuli (3× 30s contralateral arm occlusions). Hyperemia resulted in a significant decrease (-13.7%, pconditioning restored the PWV decline (pre: -11.0%, pconditioning restores this response. This technique may be useful for the assessment of novel treatment strategies and mechanisms underlying remote pre- and post-ischemic conditioning in protecting the cardiovascular system.

  14. Radial velocity planets de-aliased. A new, short period for Super-Earth 55 Cnc e

    CERN Document Server

    Dawson, Rebekah I

    2010-01-01

    Radial velocity measurements of stellar reflex motion have revealed many extra-solar planets, but gaps in the observations produce aliases, spurious frequencies that are frequently confused with the planets' orbital frequencies. In the case of Gl 581d, the distinction between an alias and the true frequency was the distinction between a dead, frozen planet and a planet likely hospitable to life (Udry et al. 2007; Mayor et al. 2009). To improve the characterization of planetary systems, we describe how aliases originate and present a new approach for distinguishing between orbital frequencies and their aliases. Our approach harnesses features in the spectral window function to compare the amplitude and phase of predicted aliases with peaks present in the data. We apply it to confirm prior alias distinctions for the planets GJ 876d and HD 75898b. We find that the true periods of Gl 581c and HD 73526b/c remain ambiguous. We revise the periods of HD 156668b and 55 Cnc e, which were afflicted by daily aliases. For...

  15. PlanetPack: a radial-velocity time-series analysis tool facilitating exoplanets detection, characterization, and dynamical simulations

    CERN Document Server

    Baluev, Roman V

    2013-01-01

    We present PlanetPack, a new software tool that we developed to facilitate and standardize the advanced analysis of radial velocity (RV) data for the goal of exoplanets detection, characterization, and basic dynamical $N$-body simulations. PlanetPack is a command-line interpreter, that can run either in an interactive mode or in a batch mode of automatic script interpretation. Its major abilities include: (i) Advanced RV curve fitting with the proper maximum-likelihood treatment of unknown RV jitter; (ii) User-friendly multi-Keplerian as well as Newtonian $N$-body RV fits; (iii) Use of more efficient maximum-likelihood periodograms that involve the full multi-planet fitting (sometimes called as ``residual'' or ``recursive'' periodograms); (iv) Easily calculatable parametric 2D likelihood function level contours, reflecting the asymptotic confidence regions; (v) Fitting under some useful functional constraints is user-friendly; (vi) Basic tasks of short- and long-term planetary dynamical simulation using a fas...

  16. Analysis of combined radial velocities and activity of BD+20 1790: evidence supporting the existence of a planetary companion

    CERN Document Server

    Hernán-Obispo, M; Gálvez-Ortiz, M C; Golovin, A; Barnes, J R; Jones, H R A; Kane, S R; Pinfield, D; Jenkins, J S; Petit, P; Anglada-Escudé, G; Marsden, S C; Catalán, S; Jeffers, S V; de Castro, E; Cornide, M; Garcés, A; Jones, M I; Gorlova, N; Andreev, M

    2015-01-01

    This paper presents the simultaneous Bayesian analysis of the radial velocity and activity indices for the K5Ve active star BD+20 1790, that was proposed to host a close-in massive planet by Hern\\'an-Obispo et al. (2010). The Bayesian analysis supports the hypothesis of a planetary companion. We present a new orbital solution after removing the two main contributions to the stellar jitter, one that varies with the photometric period and another that varies with the synodic period of the star+planet system. We use a new method to determine these jitter components, considering them as a second and third signals in the system. A discussion on possible magnetic star-planet-interaction is included, based on the Bayesian analysis of the activity indices. We propose two possible sources for flare events of this star: one related to the geometry of the system and the relative movement of the star+planet, and a second one purely stochastic source that is related to the evolution of stellar active regions. Also, we obs...

  17. Search for Close-in Planets around Evolved Stars with Phase-curve variations and Radial Velocity Measurements

    Science.gov (United States)

    Hirano, Teruyuki; Sato, Bun'ei; Masuda, Kento; Benomar, Othman Michel; Takeda, Yoichi; Omiya, Masashi; Harakawa, Hiroki

    2016-10-01

    Tidal interactions are a key process to understand the evolution history of close-in exoplanets. But tidals still have a large uncertainty in their prediction for the damping timescales of stellar obliquity and semi-major axis. We have worked on a search for transiting giant planets around evolved stars, for which few close-in planets were discovered. It has been reported that evolved stars lack close-in planets, which is often attributed to the tidal evolution and/or engulfment of close-in planets by the hosts. Meanwhile, Kepler has detected a certain fraction of transiting planet candidates around evolved stars. Confirming the planetary nature for these candidates is especially important since the comparison between the occurrence rates of close-in planets around main sequence stars and evolved stars provides a unique opportunity to discuss the final stage of close-in planets. With the aim of confirming KOI planet candidates around evolved stars, we measured precision radial velocities (RVs) for evolved stars with transiting planet candidates using Subaru/HDS. We also developed a new code which simultaneously models and fits the observed RVs and phase-curve variations in the Kepler data (e.g., transits, stellar ellipsoidal variations, and planet emission/reflected light). As a result of applying the global fit to KOI giants/subgiants, we confirmed two giant planets around evolved stars (Kepler-91 and KOI-1894), as well as revealed that KOI-977 is more likely a false positive.

  18. A laser frequency comb that enables radial velocity measurements with a precision of 1 cm s(-1).

    Science.gov (United States)

    Li, Chih-Hao; Benedick, Andrew J; Fendel, Peter; Glenday, Alexander G; Kärtner, Franz X; Phillips, David F; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L

    2008-04-03

    Searches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision of 60 cm s(-1) (ref. 1), which is sufficient to find a 5-Earth-mass planet in a Mercury-like orbit around a Sun-like star. To find a 1-Earth-mass planet in an Earth-like orbit, a precision of approximately 5 cm s(-1) is necessary. The combination of a laser frequency comb with a Fabry-Pérot filtering cavity has been suggested as a promising approach to achieve such Doppler shift resolution via improved spectrograph wavelength calibration, with recent encouraging results. Here we report the fabrication of such a filtered laser comb with up to 40-GHz (approximately 1-A) line spacing, generated from a 1-GHz repetition-rate source, without compromising long-term stability, reproducibility or spectral resolution. This wide-line-spacing comb, or 'astro-comb', is well matched to the resolving power of high-resolution astrophysical spectrographs. The astro-comb should allow a precision as high as 1 cm s(-1) in astronomical radial velocity measurements.

  19. Constraining the Frequency of Free-Floating Planets from a Synthesis of Microlensing, Radial Velocity, and Direct Imaging Survey Results

    CERN Document Server

    Clanton, Christian

    2016-01-01

    A microlensing survey by Sumi et al. (2011) exhibits an overabundance of short-timescale events (STEs; t_E~10 AU) and free-floating planets. Assuming these STEs are indeed due to planetary-mass objects, we aim to constrain the fraction of these events that can be explained by bound but wide-separation planets. We fit the observed timescale distribution with a lens mass function comprised of brown dwarfs, main-sequence stars, and stellar remnants, finding and thus corroborating the initial identification of an excess of STEs. We then include a population of bound planets that are expected not to show signatures of the primary lens (host) in their microlensing light curves and that are also consistent with results from representative microlensing, radial velocity, and direct imaging surveys. We find that bound planets alone cannot explain the entire STE excess without violating the constraints from the surveys we consider and thus some fraction of these events must be due to free-floating planets, if our model ...

  20. Metal Abundances, Radial Velocities and other Physical Characteristics for the RR Lyrae Stars in the Kepler Field

    CERN Document Server

    Nemec, James M; Ripepi, Vincenzo; Derekas, Aliz; Moskalik, Pawel; Sesar, Branimir; Chadid, Merieme; Bruntt, Hans

    2013-01-01

    Spectroscopic iron-to-hydrogen ratios, radial velocities, atmospheric parameters, and new photometric analyses are presented for 41 RR Lyrae stars (and one probable high-amplitude delta Scuti star) located in the field-of-view of the Kepler space telescope. Thirty-seven of the RR Lyrae stars are fundamental-mode pulsators (i.e., RRab stars) of which 16 exhibit the Blazhko effect. Four of the stars are multiperiodic RRc pulsators oscillating primarily in the first-overtone mode. Spectroscopic [Fe/H] values for the 34 stars for which we were able to derive estimates range from -2.54 +/- 0.13 (NR Lyr) to -0.05 +/- 0.13 dex (V784 Cyg), and for the 19 Kepler-field non-Blazhko stars studied by Nemec et al.(2011) the abundances agree will with their photometric [Fe/H] values. Four non-Blazhko RR Lyrae stars that they identified as metal-rich (KIC 6100702, V2470 Cyg, V782 Cyg and V784 Cyg) are confirmed as such, and four additional stars (V839 Cyg, KIC 5520878, KIC 8832417, KIC 3868420) are also shown here to be meta...

  1. How eclipse time variations, eclipse duration variations, and radial velocities can reveal S-type planets in close eclipsing binaries

    CERN Document Server

    Oshagh, M; Dreizler, S

    2016-01-01

    While about a dozen transiting planets have been found in wide orbits around an inner, close stellar binary (so-called "P-type planets"), no planet has yet been detected orbiting only one star (a so-called "S-type planet") in an eclipsing binary. This is despite a large number of eclipsing binary systems discovered with the Kepler telescope. Here we propose a new detection method for these S-type planets, which uses a correlation between the stellar radial velocities (RVs), eclipse timing variations (ETVs), and eclipse duration variations (EDVs). We test the capability of this technique by simulating a realistic benchmark system and demonstrate its detectability with existing high-accuracy RV and photometry instruments. We illustrate that, with a small number of RV observations, the RV-ETV diagrams allows us to distinguish between prograde and retrograde planetary orbits and also the planetary mass can be estimated if the stellar cross-correlation functions can be disentangled. We also identify a new (though ...

  2. SEVEN NEW BINARIES DISCOVERED IN THE KEPLER LIGHT CURVES THROUGH THE BEER METHOD CONFIRMED BY RADIAL-VELOCITY OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Faigler, S.; Mazeh, T.; Tal-Or, L. [School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978 (Israel); Quinn, S. N.; Latham, D. W. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States)

    2012-02-20

    We present seven newly discovered non-eclipsing short-period binary systems with low-mass companions, identified by the recently introduced BEER algorithm, applied to the publicly available 138-day photometric light curves obtained by the Kepler mission. The detection is based on the beaming effect (sometimes called Doppler boosting), which increases (decreases) the brightness of any light source approaching (receding from) the observer, enabling a prediction of the stellar Doppler radial-velocity (RV) modulation from its precise photometry. The BEER algorithm identifies the BEaming periodic modulation, with a combination of the well-known Ellipsoidal and Reflection/heating periodic effects, induced by short-period companions. The seven detections were confirmed by spectroscopic RV follow-up observations, indicating minimum secondary masses in the range 0.07-0.4 M{sub Sun }. The binaries discovered establish for the first time the feasibility of the BEER algorithm as a new detection method for short-period non-eclipsing binaries, with the potential to detect in the near future non-transiting brown-dwarf secondaries, or even massive planets.

  3. The precision radial velocity error budget for the Gemini High-resolution Optical SpecTrograph (GHOST)

    Science.gov (United States)

    Ireland, Michael J.; Artigau, Étienne; Burley, Greg; Edgar, Michael; Margheim, Steve; Robertson, Gordon; Pazder, John; McDermid, Richard; Zhelem, Ross

    2016-08-01

    The Gemini High-resolution Optical SpecTrograph (GHOST) is a fiber fed spectrograph primarily designed for high efficiency and broad wavelength coverage (363 -1000nm), with an anticipated commissioning early in 2018. The primary scientific goal of the Precision Radial Velocity (PRV) mode will be follow-up of relatively faint (R>12) transiting exoplanet targets, especially from the TESS mission. In the PRV mode, the 1.2 arcsec diameter stellar image will be split 19 ways, combined in a single slit with a simultaneous Th/Xe reference source, dispersed at a resolving power of 80,000 and imaged onto two detectors. The spectrograph will be thermally stabilized in the Gemini pier laboratory, and modal noise will be reduced below other sources through the use of a fiber agitator. Unlike other precision high resolution spectrographs, GHOST will not be pressure controlled (although pressure will be monitored precisely), and there will be no double scrambler or shaped (e.g. octagonal) fibers. Instead, GHOST will have to rely on simultaneous two-color imaging of the slit and the simultaneous Th/Xe fiber to correct for variable fiber illumination and focal-ratio degradation. This configuration presents unique challenges in estimating a PRV error budget.

  4. SOAP 2.0: A Tool to Estimate the Photometric and Radial Velocity Variations Induced by Stellar Spots and Plages

    Science.gov (United States)

    Dumusque, X.; Boisse, I.; Santos, N. C.

    2014-12-01

    This paper presents SOAP 2.0, a new version of the Spot Oscillation And Planet (SOAP) code that estimates in a simple way the photometric and radial velocity (RV) variations induced by active regions. The inhibition of the convective blueshift (CB) inside active regions is considered, as well as the limb brightening effect of plages, a quadratic limb darkening law, and a realistic spot and plage contrast ratio. SOAP 2.0 shows that the activity-induced variation of plages is dominated by the inhibition of the CB effect. For spots, this effect becomes significant only for slow rotators. In addition, in the case of a major active region dominating the activity-induced signal, the ratio between the FWHM and the RV peak-to-peak amplitudes of the cross correlation function can be used to infer the type of active region responsible for the signal for stars with v sin i SOAP 2.0 manages to reproduce the activity variation as well as previous simulations when a spot is dominating the activity-induced variation. In addition, SOAP 2.0 also reproduces the activity variation induced by a plage on the slowly rotating star α Cen B, which is not possible using previous simulations. Following these results, SOAP 2.0 can be used to estimate the signal induced by spots and plages, but also to correct for it when a major active region is dominating the RV variation. . The work in this paper is based on observations made with the MOST satellite, the HARPS instrument on the ESO 3.6 m telescope at La Silla Observatory (Chile), and the SOPHIE instrument at the Observatoire de Haute Provence (France).

  5. SOAP 2.0: a tool to estimate the photometric and radial velocity variations induced by stellar spots and plages

    Energy Technology Data Exchange (ETDEWEB)

    Dumusque, X. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Boisse, I. [Laboratoire d' Astrophysique de Marseille (UMR 6110), Technopole de Château-Gombert, 38 rue Frédéric Joliot-Curie, F-13388 Marseille Cedex 13 (France); Santos, N. C., E-mail: xdumusque@cfa.harvard.edu [Centro de Astrofìsica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal)

    2014-12-01

    This paper presents SOAP 2.0, a new version of the Spot Oscillation And Planet (SOAP) code that estimates in a simple way the photometric and radial velocity (RV) variations induced by active regions. The inhibition of the convective blueshift (CB) inside active regions is considered, as well as the limb brightening effect of plages, a quadratic limb darkening law, and a realistic spot and plage contrast ratio. SOAP 2.0 shows that the activity-induced variation of plages is dominated by the inhibition of the CB effect. For spots, this effect becomes significant only for slow rotators. In addition, in the case of a major active region dominating the activity-induced signal, the ratio between the FWHM and the RV peak-to-peak amplitudes of the cross correlation function can be used to infer the type of active region responsible for the signal for stars with v sin i ≤8 km s{sup –1}. A ratio smaller than three implies a spot, while a larger ratio implies a plage. Using the observation of HD 189733, we show that SOAP 2.0 manages to reproduce the activity variation as well as previous simulations when a spot is dominating the activity-induced variation. In addition, SOAP 2.0 also reproduces the activity variation induced by a plage on the slowly rotating star α Cen B, which is not possible using previous simulations. Following these results, SOAP 2.0 can be used to estimate the signal induced by spots and plages, but also to correct for it when a major active region is dominating the RV variation.

  6. Radial Velocity Fiber-Fed Spectrographs Towards the Discovery of Compact Planets and Pulsations on M Stars

    Science.gov (United States)

    Berdiñas, Zaira M.

    2016-11-01

    This thesis is developed in the framework of the paradigm that seeks for the discovery of an Earth analog. Nowadays, low mass stars, and in particular M dwarf stars, are key targets towards achieving this goal. In this thesis, I focus on the study of the short-time domain of M dwarf stars with the aim of searching for short period planets, but also for the first detection of stellar pulsations on this spectral type. Both science goals are the primary objectives of the “Cool Tiny Beats” (CTB) survey, which has produced most of the data used in this thesis. CTB data consist in high resolution and high-cadence spectroscopic Doppler measurements taken either with HARPS or HARPS-N spectrographs. First of all, a thorough understanding of the spectrographs response in the short time domain was performed to characterize the sources of noise in our range of study. Our first approach to the goals of this thesis consisted in the design of an observational experiment to delve into the HARPS-N sub-night performance. Results unveiled variability of the spectra continuum correlated with instabilities of the spectrograph illumination associated to the airmass. Such distortions, which are wavelength and time dependent, are also present in at least one of the data-products given by the HARPS-N reduction software: the width of the mean-line profiles (i.e. the so-called FWHM index), an index commonly used as a proxy of the stellar activity. As a consequence, we searched for an alternative approach to measure the width index. In particular, we calculated the mean-line profile of the spectrum with a least-squares-deconvolution technique and we obtained the profile indices as the moments of the profile distribution. As part of this study, we also corroborated that the radial velocities calculated with our template matching algorithm TERRA are not affected by the illumination stability. This work unveiled a possible failure of the HARPS-N atmospheric dispersion corrector (or ADC) and

  7. Retrieval of Precise Radial Velocities from Near-infrared High-resolution Spectra of Low-mass Stars

    Science.gov (United States)

    Gao, Peter; Plavchan, P.; Gagné, J.; Furlan, E.; Bottom, M.; Anglada-Escudé, G.; White, R.; Davison, C. L.; Beichman, C.; Brinkworth, C.; Johnson, J.; Ciardi, D.; Wallace, K.; Mennesson, B.; von Braun, K.; Vasisht, G.; Prato, L.; Kane, S. R.; Tanner, A.; Crawford, T. J.; Latham, D.; Rougeot, R.; Geneser, C. S.; Catanzarite, J.

    2016-10-01

    Given that low-mass stars have intrinsically low luminosities at optical wavelengths and a propensity for stellar activity, it is advantageous for radial velocity (RV) surveys of these objects to use near-infrared (NIR) wavelengths. In this work, we describe and test a novel RV extraction pipeline dedicated to retrieving RVs from low-mass stars using NIR spectra taken by the CSHELL spectrograph at the NASA Infrared Telescope Facility, where a methane isotopologue gas cell is used for wavelength calibration. The pipeline minimizes the residuals between the observations and a spectral model composed of templates for the target star, the gas cell, and atmospheric telluric absorption; models of the line-spread function, continuum curvature, and sinusoidal fringing; and a parameterization of the wavelength solution. The stellar template is derived iteratively from the science observations themselves without a need for separate observations dedicated to retrieving it. Despite limitations from CSHELL’s narrow wavelength range and instrumental systematics, we are able to (1) obtain an RV precision of 35 m s-1 for the RV standard star GJ 15 A over a time baseline of 817 days, reaching the photon noise limit for our attained signal-to-noise ratio; (2) achieve ˜3 m s-1 RV precision for the M giant SV Peg over a baseline of several days and confirm its long-term RV trend due to stellar pulsations, as well as obtain nightly noise floors of ˜2-6 m s-1 and (3) show that our data are consistent with the known masses, periods, and orbital eccentricities of the two most massive planets orbiting GJ 876. Future applications of our pipeline to RV surveys using the next generation of NIR spectrographs, such as iSHELL, will enable the potential detection of super-Earths and mini-Neptunes in the habitable zones of M dwarfs.

  8. METAL ABUNDANCES, RADIAL VELOCITIES, AND OTHER PHYSICAL CHARACTERISTICS FOR THE RR LYRAE STARS IN THE KEPLER FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Nemec, James M. [Department of Physics and Astronomy, Camosun College, Victoria, British Columbia, V8P 5J2 (Canada); Cohen, Judith G.; Sesar, Branimir [Department of Physics and Astronomy, Caltech, Pasadena, CA (United States); Ripepi, Vincenzo [INAF-Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli (Italy); Derekas, Aliz [Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, H-1121 Budapest (Hungary); Moskalik, Pawel [Copernicus Astronomical Centre, ul.Bartycka 18, 00-716, Warsaw (Poland); Chadid, Merieme [Observatoire de la Cote d' Azur, Universite de Nice, Sophia-Antipolis, UMR 6525, Parc Valrose, F-06108 Nice Cedex 02 (France); Bruntt, Hans, E-mail: nemec@camosun.ca, E-mail: jmn@isr.bc.ca, E-mail: jlc@astro.caltech.edu, E-mail: bsesar@astro.caltech.edu, E-mail: ripepi@na.astro.it, E-mail: derekas@konkoly.hu, E-mail: pam@camk.edu.pl, E-mail: chadid@marseille.fr, E-mail: bruntt@phys.au.dk [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)

    2013-08-20

    Spectroscopic iron-to-hydrogen ratios, radial velocities, atmospheric parameters, and new photometric analyses are presented for 41 RR Lyrae stars (and one probable high-amplitude {delta} Sct star) located in the field-of-view of the Kepler space telescope. Thirty-seven of the RR Lyrae stars are fundamental-mode pulsators (i.e., RRab stars) of which sixteen exhibit the Blazhko effect. Four of the stars are multiperiodic RRc pulsators oscillating primarily in the first-overtone mode. Spectroscopic [Fe/H] values for the 34 stars for which we were able to derive estimates range from -2.54 {+-} 0.13 (NR Lyr) to -0.05 {+-} 0.13 dex (V784 Cyg), and for the 19 Kepler-field non-Blazhko stars studied by Nemec et al. the abundances agree will with their photometric [Fe/H] values. Four non-Blazhko RR Lyrae stars that they identified as metal-rich (KIC 6100702, V2470 Cyg, V782 Cyg and V784 Cyg) are confirmed as such, and four additional stars (V839 Cyg, KIC 5520878, KIC 8832417, KIC 3868420) are also shown here to be metal-rich. Five of the non-Blazhko RRab stars are found to be more metal-rich than [Fe/H] {approx}-0.9 dex while all of the 16 Blazhko stars are more metal-poor than this value. New P-{phi}{sub 31}{sup s}-[Fe/H] relationships are derived based on {approx}970 days of quasi-continuous high-precision Q0-Q11 long- and short-cadence Kepler photometry. With the exception of some Blazhko stars, the spectroscopic and photometric [Fe/H] values are in good agreement. Several stars with unique photometric characteristics are identified, including a Blazhko variable with the smallest known amplitude and frequency modulations (V838 Cyg)

  9. RUN DMC: An efficient, parallel code for analyzing Radial Velocity Observations using N-body Integrations and Differential Evolution Markov chain Monte Carlo

    CERN Document Server

    Nelson, Benjamin E; Payne, Matthew J

    2013-01-01

    In the 20+ years of Doppler observations of stars, scientists have uncovered a diverse population of extrasolar multi-planet systems. A common technique for characterizing the orbital elements of these planets is Markov chain Monte Carlo (MCMC), using a Keplerian model with random walk proposals and paired with the Metropolis-Hastings algorithm. For approximately a couple of dozen planetary systems with Doppler observations, there are strong planet-planet interactions due to the system being in or near a mean-motion resonance (MMR). An N-body model is often required to accurately describe these systems. Further computational difficulties arise from exploring a high-dimensional parameter space ($\\sim$7 x number of planets) that can have complex parameter correlations. To surmount these challenges, we introduce a differential evolution MCMC (DEMCMC) applied to radial velocity data while incorporating self-consistent N-body integrations. Our Radial velocity Using N-body DEMCMC (RUN DMC) algorithm improves upon t...

  10. Radial velocities and metallicities from infrared Ca II triplet spectroscopy of open clusters II. Berkeley 23, King 1, NGC 559, NGC 6603 and NGC 7245

    CERN Document Server

    Carrera, R; Ospina, N; Balaguer-Nuñez, L; Jordi, C; Monteagudo, L

    2015-01-01

    Context: Open clusters are key to studying the formation and evolution of the Galactic disc. However, there is a deficiency of radial velocity and chemical abundance determinations for open clusters in the literature. Aims: We intend to increase the number of determinations of radial velocities and metallicities from spectroscopy for open clusters. Methods: We acquired medium-resolution spectra (R~8000) in the infrared region Ca II triplet lines (~8500 AA) for several stars in five open clusters with the long-slit IDS spectrograph on the 2.5~m Isaac Newton Telescope (Roque de los Muchachos Observatory, Spain). Radial velocities were obtained by cross-correlation fitting techniques. The relationships available in the literature between the strength of infrared Ca II lines and metallicity were also used to derive the metallicity for each cluster. Results: We obtain = 48.6+/-3.4, -58.4+/-6.8, 26.0+/-4.3 and -65.3+/-3.2 km s-1 for Berkeley 23, NGC 559, NGC 6603 and NGC 7245, respectively. We found [Fe/H] =-0.25+...

  11. The CRIRES Search for Planets Around the Lowest-Mass Stars. I. High-Precision Near-Infrared Radial Velocities with an Ammonia Gas Cell

    CERN Document Server

    Bean, Jacob L; Hartman, Henrik; Nilsson, Hampus; Wiedemann, Guenter; Reiners, Ansgar; Dreizler, Stefan; Henry, Todd J

    2009-01-01

    Radial velocities measured from near-infrared spectra are a potentially powerful tool to search for planets around cool stars and sub-stellar objects. However, no technique currently exists that yields near-infrared radial velocity precision comparable to that which is routinely obtained in the visible. We describe a method for measuring high-precision relative radial velocities of cool stars from K-band spectra. The method makes use of a glass cell filled with ammonia gas to calibrate the spectrograph response similar to the iodine cell technique that has been used so successfully in the visible. Stellar spectra are obtained through the ammonia cell and modeled as the product of a Doppler-shifted template spectrum of the object and a spectrum of the cell, convolved with a variable instrumental profile model. A complicating factor is that a significant number of telluric absorption lines are present in the spectral regions containing useful stellar and ammonia lines. The telluric lines are modeled simultaneou...

  12. The CORALIE survey for Southern extra-solar planets. IV. Intrinsic stellar limitations to planet searches with radial-velocity techniques

    Science.gov (United States)

    Santos, N. C.; Mayor, M.; Naef, D.; Pepe, F.; Queloz, D.; Udry, S.; Blecha, A.

    2000-09-01

    Activity related phenomena can induce radial-velocity variations, which can be very important when dealing with extra-solar planet search programmes requiring high-precision radial-velocity measurements. In this paper we present a new chromospheric activity index, SCOR, based on the Ca Ii H line central reemission, and constructed using CORALIE spectra. After one year of measurements, values of SCOR are available for a sub-sample of stars of the Geneva extra-solar planet search programme. After transforming the SCOR values into the Mount-Wilson ``S'' scale we obtained values of the Ca Ii H and K flux corrected from photospheric emission (R'HK) for the stars. The first results are presented, and in particular we focus on the study of the relation between the observed radial-velocity scatter and the chromospheric activity index R'HK, for F, G and K dwarfs. Based on observations collected at the La Silla Observatory, ESO (Chile), with the echelle spectrograph CORALIE at the 1.2-m Euler Swiss telescope

  13. Constraining the Frequency of Free-floating Planets from a Synthesis of Microlensing, Radial Velocity, and Direct Imaging Survey Results

    Science.gov (United States)

    Clanton, Christian; Gaudi, B. Scott

    2017-01-01

    A microlensing survey by Sumi et al. exhibits an overabundance of short-timescale events (STEs; tE < 2 days) relative to what is expected from known stellar populations and a smooth power-law extrapolation down to the brown dwarf regime. This excess has been interpreted as a population of approximately Jupiter-mass objects that outnumber main-sequence stars nearly twofold; however the microlensing data alone cannot distinguish between events due to wide-separation (a ≳ 10 au) and free-floating planets. Assuming these STEs are indeed due to planetary-mass objects, we aim to constrain the fraction of these events that can be explained by bound but wide-separation planets. We fit the observed timescale distribution with a lens mass function comprised of brown dwarfs, main-sequence stars, and stellar remnants, finding and thus corroborating the initial identification of an excess of STEs. We then include a population of bound planets that are expected not to show signatures of the primary lens (host) in their microlensing light curves and that are also consistent with results from representative microlensing, radial velocity, and direct imaging surveys. We find that bound planets alone cannot explain the entire STE excess without violating the constraints from the surveys we consider and thus some fraction of these events must be due to free-floating planets, if our model for bound planets holds. We estimate a median fraction of STEs due to free-floating planets to be f = 0.67 (0.23 ≤ f ≤ 0.85 at 95% confidence) when assuming “hot-start” planet evolutionary models and f = 0.58 (0.14 ≤ f ≤ 0.83 at 95% confidence) for “cold-start” models. Assuming a delta-function distribution of free-floating planets of mass {m}p=2 {M}{Jup} yields a number of free-floating planets per main-sequence star of N = 1.4 (0.48 ≤ N ≤ 1.8 at 95% confidence) in the “hot-start” case and N = 1.2 (0.29 ≤ N ≤ 1.8 at 95% confidence) in the “cold-start” case.

  14. A six-beam method to measure turbulence statistics using ground-based wind lidars

    Directory of Open Access Journals (Sweden)

    A. Sathe

    2014-10-01

    Full Text Available A so-called six-beam method is proposed to measure atmospheric turbulence using a ground-based wind lidar. This method requires measurement of the radial velocity variances at five equally spaced azimuth angles on the base of a scanning cone and one measurement at the center of the scanning circle, i.e.using a vertical beam at the same height. The scanning configuration is optimized to minimize the sum of the random errors in the measurement of the second-order moments of the components (u,v, w of the wind field. We present this method as an alternative to the so-called velocity azimuth display (VAD method that is routinely used in commercial wind lidars, and which usually results in significant averaging effects of measured turbulence. In the VAD method, the high frequency radial velocity measurements are used instead of their variances. The measurements are performed using a pulsed lidar (WindScanner, and the derived turbulence statistics (using both methods such as the u and v variances are compared with those obtained from a reference cup anemometer and a wind vane at 89 m height under different atmospheric stabilities. The measurements show that in comparison to the reference cup anemometer, depending on the atmospheric stability and the wind field component, the six-beam method measures between 85–101% of the reference turbulence, whereas the VAD method measures between 66–87% of the reference turbulence.

  15. A six-beam method to measure turbulence statistics using ground-based wind lidars

    Science.gov (United States)

    Sathe, A.; Mann, J.; Vasiljevic, N.; Lea, G.

    2015-02-01

    A so-called six-beam method is proposed to measure atmospheric turbulence using a ground-based wind lidar. This method requires measurement of the radial velocity variances at five equally spaced azimuth angles on the base of a scanning cone and one measurement at the centre of the scanning circle, i.e.using a vertical beam at the same height. The scanning configuration is optimized to minimize the sum of the random errors in the measurement of the second-order moments of the components (u,v, w) of the wind field. We present this method as an alternative to the so-called velocity azimuth display (VAD) method that is routinely used in commercial wind lidars, and which usually results in significant averaging effects of measured turbulence. In the VAD method, the high frequency radial velocity measurements are used instead of their variances. The measurements are performed using a pulsed lidar (WindScanner), and the derived turbulence statistics (using both methods) such as the u and v variances are compared with those obtained from a reference cup anemometer and a wind vane at 89 m height under different atmospheric stabilities. The measurements show that in comparison to the reference cup anemometer, depending on the atmospheric stability and the wind field component, the six-beam method measures between 85 and 101% of the reference turbulence, whereas the VAD method measures between 66 and 87% of the reference turbulence.

  16. Ground based materials science experiments

    Science.gov (United States)

    Meyer, M. B.; Johnston, J. C.; Glasgow, T. K.

    1988-01-01

    The facilities at the Microgravity Materials Science Laboratory (MMSL) at the Lewis Research Center, created to offer immediate and low-cost access to ground-based testing facilities for industrial, academic, and government researchers, are described. The equipment in the MMSL falls into three categories: (1) devices which emulate some aspect of low gravitational forces, (2) specialized capabilities for 1-g development and refinement of microgravity experiments, and (3) functional duplicates of flight hardware. Equipment diagrams are included.

  17. Ground based materials science experiments

    Science.gov (United States)

    Meyer, M. B.; Johnston, J. C.; Glasgow, T. K.

    1988-01-01

    The facilities at the Microgravity Materials Science Laboratory (MMSL) at the Lewis Research Center, created to offer immediate and low-cost access to ground-based testing facilities for industrial, academic, and government researchers, are described. The equipment in the MMSL falls into three categories: (1) devices which emulate some aspect of low gravitational forces, (2) specialized capabilities for 1-g development and refinement of microgravity experiments, and (3) functional duplicates of flight hardware. Equipment diagrams are included.

  18. An ML-Based Radial Velocity Estimation Algorithm for Moving Targets in Spaceborne High-Resolution and Wide-Swath SAR Systems

    Directory of Open Access Journals (Sweden)

    Tingting Jin

    2017-04-01

    Full Text Available Multichannel synthetic aperture radar (SAR is a significant breakthrough to the inherent limitation between high-resolution and wide-swath (HRWS compared with conventional SAR. Moving target indication (MTI is an important application of spaceborne HRWS SAR systems. In contrast to previous studies of SAR MTI, the HRWS SAR mainly faces the problem of under-sampled data of each channel, causing single-channel imaging and processing to be infeasible. In this study, the estimation of velocity is equivalent to the estimation of the cone angle according to their relationship. The maximum likelihood (ML based algorithm is proposed to estimate the radial velocity in the existence of Doppler ambiguities. After that, the signal reconstruction and compensation for the phase offset caused by radial velocity are processed for a moving target. Finally, the traditional imaging algorithm is applied to obtain a focused moving target image. Experiments are conducted to evaluate the accuracy and effectiveness of the estimator under different signal-to-noise ratios (SNR. Furthermore, the performance is analyzed with respect to the motion ship that experiences interference due to different distributions of sea clutter. The results verify that the proposed algorithm is accurate and efficient with low computational complexity. This paper aims at providing a solution to the velocity estimation problem in the future HRWS SAR systems with multiple receive channels.

  19. Precise radial velocities of giant stars IX. HD 59686 Ab: a massive circumstellar planet orbiting a giant star in a ~13.6 au eccentric binary system

    CERN Document Server

    Ortiz, Mauricio; Trifonov, Trifon; Quirrenbach, Andreas; Mitchell, David; Nowak, Grzegorz; Buenzli, Esther; Zimmerman, Neil; Bonnefoy, Mickael; Skemer, Andy; Defrère, Denis; Lee, Man Hoi; Fischer, Debra; Hinz, Philip

    2016-01-01

    Context: For over 12 years, we have carried out a precise radial velocity survey of a sample of 373 G and K giant stars using the Hamilton \\'Echelle Spectrograph at Lick Observatory. There are, among others, a number of multiple planetary systems in our sample as well as several planetary candidates in stellar binaries. Aims: We aim at detecting and characterizing substellar+stellar companions to the giant star HD 59686 A (HR 2877, HIP 36616). Methods: We obtained high precision radial velocity (RV) measurements of the star HD 59686 A. By fitting a Keplerian model to the periodic changes in the RVs, we can assess the nature of companions in the system. In order to discriminate between RV variations due to non-radial pulsation or stellar spots we used infrared RVs taken with the CRIRES spectrograph at the Very Large Telescope. Additionally, to further characterize the system, we obtain high-resolution images with LMIRCam at the Large Binocular Telescope. Results: We report the likely discovery of a giant plane...

  20. The Demographics of Exoplanetary Companions to M Dwarfs: Synthesizing Results from Microlensing, Radial Velocity, and Direct Imaging Surveys

    Science.gov (United States)

    Clanton, Christian Dwain

    Over the past 20 years, we have learned that exoplanets are ubiquitous throughout our Galaxy and show a diverse set of demographics, yet there is much work to be done to understand this diversity. Determining the distributions of the fundamental properties of exoplanets will provide vital clues regarding their formation and evolution. This is a difficult task, as exoplanet surveys are not uniformly sensitive to the full range of planet parameter space. Various observational biases and selection effects intrinsic to each of the different discovery techniques constrain the types of planets to which they are sensitive. Herein, I record a collection of the first studies to develop and apply the methodology of synthesizing results from multiple detection techniques to construct a statistically-complete census of planetary companions to M dwarfs that samples a wide region of their parameter space. I present a robust comparison of exoplanet discoveries from microlensing and radial velocity (RV) surveys of M dwarfs which infer giant planet frequencies that differ by more than an order of magnitude and are, prima facie, in direct conflict. I demonstrate that current, state-of-the-art RV surveys are capable of detecting only the high-mass tail of the population of planets beyond the ice line inferred by microlensing studies, engendering a large, apparent difference in giant planet frequency. This comparison further establishes that results from these types of surveys are, in fact, consistent over the region of parameter space wherein their sensitivities overlap. A synthesis of results from microlensing and RV surveys yields planet occurrence rates for M dwarfs that span several orders of magnitude in mass and orbital period. On average, each M dwarf hosts about two planets, and while Jupiter and super-Jupiter companions are relatively rare ( 3%), gas giants, in general, are quite common ( 15%). These occurrence rates are significantly lower than those inferred around FGK

  1. A six-beam method to measure turbulence statistics using ground-based wind lidars

    DEFF Research Database (Denmark)

    Sathe, Ameya; Mann, Jakob; Vasiljevic, Nikola

    2015-01-01

    A so-called six-beam method is proposed to measure atmospheric turbulence using a ground-based wind lidar. This method requires measurement of the radial velocity variances at five equally spaced azimuth angles on the base of a scanning cone and one measurement at the centre of the scanning circle...... lidar (WindScanner), and the derived turbulence statistics (using both methods) such as the u and v variances are compared with those obtained from a reference cup anemometer and a wind vane at 89m height under different atmospheric stabilities. The measurements show that in comparison to the reference...... cup anemometer, depending on the atmospheric stability and the wind field component, the six-beam method measures between 85 and 101% of the reference turbulence, whereas the VAD method measures between 66 and 87% of the reference turbulence....

  2. A six-beam method to measure turbulence statistics using ground-based wind lidars

    DEFF Research Database (Denmark)

    Sathe, Ameya; Mann, Jakob; Vasiljevic, Nikola

    2014-01-01

    A so-called six-beam method is proposed to measure atmospheric turbulence using a ground-based wind lidar. This method requires measurement of the radial velocity variances at five equally spaced azimuth angles on the base of a scanning cone and one measurement at the center of the scanning circle...... lidar (WindScanner), and the derived turbulence statistics (using both methods) such as the u and v variances are compared with those obtained from a reference cup anemometer and a wind vane at 89m height under different atmospheric stabilities. The measurements show that in comparison to the reference...... cup anemometer, depending on the atmospheric stability and the wind field component, the six-beam method measures between 85–101% of the reference turbulence, whereas the VAD method measures between 66–87% of the reference turbulence....

  3. The association of 25(OH)D with blood pressure, pulse pressure and carotid–radial pulse wave velocity in African women

    OpenAIRE

    Iolanthé M Kruger; Schutte, Aletta E.; Huisman, Hugo W.; Van Rooyen, Johannes M.; Schutte, Rudolph; Malan, Leoné; Malan, Nicolaas T.; Carla M T Fourie; Kruger, Annamarie

    2013-01-01

    High susceptibility of the African population to develop cardiovascular disease obliges us to investigate possible contributing risk factors. Our aim was to determine whether low 25(OH)D status is associated with increased blood pressure and carotid-radial pulse wave velocity in black South African women. We studied 291 urban women (mean age: 57.5669.00 yrs.). 25(OH)D status was determined by serum 25(OH)D levels. Women were stratified into sufficient (.30 ng/ ml), and insufficien...

  4. The Progress in High Precision Astronomical Radial Velocity Technique%高精度天体视向速度测量技术研究进展

    Institute of Scientific and Technical Information of China (English)

    姜明达; 肖东; 朱永田

    2012-01-01

    近年来,尽管对太阳系外行星探测的手段层出不穷,视向速度测量依然是探测太阳系外行星卓有成效的方法.随着探测太阳系外类地行星的呼声日益高涨,大幅度提高视向速度测量精度的任务迫在眉睫.为了提高天文光谱仪的稳定性,人们采用真空或恒温、恒压的仪器工作环境来确保视向速度的测量精度;同时,激光频率梳技术的出现又为天体视向速度测量系统提供了一个高精度的光谱定标源.将激光频率梳技术应用于天体视向速度测量是今后一段时间内的研究重点.%Discovering extrasolar planet has been pursued for a long time. Since the detection of the first extrasolar planet was reported two decades ago, over seven hundred extrasolar planets were reported. Although the new technique is emerging, the radial velocity measurement is still the most productive technique for extrasolar planet hunting. As the earth 'twin' is becoming the next goal, the precision of radial velocity measurement has to be dramatically improved. First of all, varies techniques were adopted to guarantee the stability of an astronomical spectrograph. One successful spectrograph is the HARPS, ESO operating in a vacuum tank. Another effort is put the spectrograph into a regulated instrument case whose temperature and air pressure are kept constant, like the PEPSI spectrograph. In the last decade, the laser frequency comb emerges as an ideal calibration source for the astronomical spectrograph. Based on a femtosecond laser referencing to a stable oscillator such as atomic clocks, the laser frequency comb could generate evenly distributed calibration lines in a wide spectral range with the precision of absolute frequencies better than 10-10. It would ensure the precision of radial velocity measurement achieving centimeters per second, much better than current precision, meter per second. As a broad range of laser frequency combs suitable for astronomical

  5. A ground-based measurement of the relativistic beaming effect in a detached double WD binary

    CERN Document Server

    Shporer, Avi; Steinfadt, Justin D R; Bildsten, Lars; Howell, Steve B; Mazeh, Tsevi

    2010-01-01

    We report on the first ground-based measurement of the relativistic beaming effect (aka Doppler boosting). We observed the beaming effect in the detached, non-interacting eclipsing double white dwarf (WD) binary NLTT 11748. Our observations were motivated by the system's high mass ratio and low luminosity ratio, leading to a large beaming-induced variability amplitude at the orbital period of 5.6 hr. We observed the system during 3 nights at the 2.0m Faulkes Telescope North with the SDSS-g' filter, and fitted the data simultaneously for the beaming, ellipsoidal and reflection effects. Our fitted relative beaming amplitude is (3.0 +/- 0.4) x 10^(-3), consistent with the expected amplitude from a blackbody spectrum given the photometric primary radial velocity amplitude and effective temperature. This result is a first step in testing the relation between the photometric beaming amplitude and the spectroscopic radial velocity amplitude in NLTT 11748 and similar systems. We did not identify any variability due t...

  6. Frequency-modulated continuous-wave laser radar using dual vertical-cavity surface-emitting laser diodes for real-time measurements of distance and radial velocity

    Science.gov (United States)

    Kakuma, Seiichi

    2017-02-01

    A frequency-modulated continuous-wave (FMCW) laser radar capable of real-time displaying the distance to a target object and its radial velocity as their corresponding frequency spectra is developed. The system employs a pair of oppositely frequency-swept vertical-cavity surface-emitting laser diodes (VCSELs). This makes possible simultaneous detection of beat signals induced by the increment (up-ramp) and decrement (down-ramp) in laser frequencies. By mixing these two beat signals, their sum and difference frequencies are directly obtained without arithmetic processing such as averaging and subtraction. Results of the test experiments adopting axially moving block gauges as target objects show that both the distance and given velocities are accurately determined from the spectrum of the frequency mixer.

  7. BANYAN. III. Radial velocity, Rotation and X-ray emission of low-mass star candidates in nearby young kinematic groups

    CERN Document Server

    Malo, Lison; Doyon, René; Lafrenière, David; Albert, Loïc; Gagné, Jonathan

    2014-01-01

    Based on high-resolution spectra obtained with PHOENIX at Gemini-South, CRIRES at VLT-UT1, and ESPaDOnS at CFHT, we present new measurements of the radial and projected rotational velocities of 219 low-mass stars. The target likely membership was initially established using the Bayesian analysis tool recently presented in \\citet{2013malo}, taking into account only the position, proper motion and photometry of the stars to assess their membership probability. In the present study, we include radial velocity as an additional input to our analysis, and in doing so we confirm the high membership probability for 130 candidates: 27 in $\\beta$ Pictoris, 22 in Tucana-Horologium, 25 in Columba, 7 in Carina, 18 in Argus and 18 in AB Doradus and 13 with an ambiguous membership. Our analysis also confirms the membership of 57 stars proposed in the literature. A subsample of 16 candidates was observed at three or more epochs, allowing us to discover 6 new spectroscopic binaries. The fraction of binaries in our sample is 2...

  8. The SDSS-III DR12 MARVELS radial velocity data release: the first data release from the multiple object Doppler exoplanet survey

    Science.gov (United States)

    Ge, Jian; Thomas, Neil B.; Li, Rui; Senan Seieroe Grieves, Nolan; Ma, Bo; de Lee, Nathan M.; Lee, Brian C.; Liu, Jian; Bolton, Adam S.; Thakar, Aniruddha R.; Weaver, Benjamin; SDSS-Iii Marvels Team

    2015-01-01

    We present the first data release from the SDSS-III Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) through the SDSS-III DR12. The data include 181,198 radial velocity (RV) measurements for a total of 5520 different FGK stars with V~7.6-12, of which more than 80% are dwarfs and subdwarfs while remainders are GK giants, among a total of 92 fields nearly randomly spread out over the entire northern sky taken with a 60-object MARVELS dispersed fixed-delay interferometer instrument over four years (2008-2012). There were 55 fields with a total of 3300 FGK stars which had 14 or more observations over about 2-year survey window. The median number of observations for these plates is 27 RV measurements. This represents the largest homogeneous sample of precision RV measurements of relatively bright stars. In this first released data, a total of 18 giant planet candidates, 16 brown dwarfs, and over 500 binaries with additional 96 targets having RV variability indicative of a giant planet companion are reported. The released data were produced by the MARVELS finalized 1D pipeline. We will also report preliminary statistical results from the MARVELS 2D data pipeline which has produced a median RV precision of ~30 m/s for stable stars.

  9. Mass determination of K2-19b and K2-19c from radial velocities and transit timing variations

    CERN Document Server

    Nespral, D; Deeg, H J; Borsato, L; Fridlund, M C V; Barragan, O; Grziwa, S; Korth, J; Cabrera, J; Csizmadia, Sz; Nowak, G; Kuutma, T; Saario, J; Eigmuller, P; Erikson, A; Guenther, E W; Hatzes, A P; Rodriguez, P Montanes; Palle, E; Patzold, M; Prieto-Arranz, J; Rauer, H; Sebastian, D

    2016-01-01

    We present FIES@NOT and HARPS-N@TNG radial velocity follow-up observations of K2-19, a compact planetary system hosting three planets, of which the two larger ones, namely K2-19b and K2-19c, are close to the 3:2 mean motion resonance. The masses of these larger planets have previously been derived from transit timing only. An analysis considering only the radial velocity measurements is able to detect only K2-19b, the largest and more massive planet in the system, with a mass of $71.7\\pm6.3$ M${_\\oplus}$. We also used the TRADES code to simultaneously model both our RV measurements and the existing transit-timing measurements. We derived a mass of K2-19b of $59.5^{+7.2}_{-11.4}$ M${_\\oplus}$ and of K2-19c of $9.7^{+3.9}_{-2.0}$ M${_\\oplus}$. A prior K2-19b mass estimated by Barros 2015, based exclusively on transit timing measurements, is only consistent with our combined TTV and RV analysis, but not with our analysis based purely on RV measurements. K2-19b supports the suspicion that planet masses and densit...

  10. A RADIAL VELOCITY TEST FOR SUPERMASSIVE BLACK HOLE BINARIES AS AN EXPLANATION FOR BROAD, DOUBLE-PEAKED EMISSION LINES IN ACTIVE GALACTIC NUCLEI

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jia; Halpern, Jules P. [Astronomy Department, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Eracleous, Michael [Department of Astronomy and Institute for Gravitation and The Cosmos, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)

    2016-01-20

    One of the proposed explanations for the broad, double-peaked Balmer emission lines observed in the spectra of some active galactic nuclei (AGNs) is that they are associated with sub-parsec supermassive black hole (SMBH) binaries. Here, we test the binary broad-line region hypothesis through several decades of monitoring of the velocity structure of double-peaked Hα emission lines in 13 low-redshift, mostly radio-loud AGNs. This is a much larger set of objects compared to an earlier test by Eracleous et al. and we use much longer time series for the three objects studied in that paper. Although systematic changes in radial velocity can be traced in many of their lines, they are demonstrably not like those of a spectroscopic binary in a circular orbit. Any spectroscopic binary period must therefore be much longer than the span of the monitoring (assuming a circular orbit), which in turn would require black hole masses that exceed by 1–2 orders of magnitude the values obtained for these objects using techniques such as reverberation mapping and stellar velocity dispersion. Moreover, the response of the double-peaked Balmer line profiles to fluctuations of the ionizing continuum and the shape of the Lyα profiles are incompatible with an SMBH binary. The binary broad-line region hypothesis is therefore disfavored. Other processes evidently shape these line profiles and cause the long-term velocity variations of the double peaks.

  11. The Brown Dwarf Kinematics Project (BDKP). IV. Radial Velocities of 85 Late-M and L dwarfs with MagE

    CERN Document Server

    Burgasser, Adam J; Gagne, Jonathan; Bochanski, John J; Faherty, Jaqueline K; West, Andrew A; Mamajek, Eric E; Schmidt, Sarah J; Cruz, Kelle L

    2015-01-01

    Radial velocity measurements are presented for 85 late M- and L-type very low mass stars and brown dwarfs obtained with the Magellan Echellette (MagE) spectrograph. Targets primarily have distances within 20 pc of the Sun, with more distant sources selected for their unusual spectral energy distributions. We achieved precisions of 2--3 km/s, and combined these with astrometric and spectrophotometric data to calculate $UVW$ velocities. Most are members of the thin disk of the Galaxy, and velocity dispersions indicate a mean age of 5.2$\\pm$0.2 Gyr for sources within 20 pc. We find significantly different kinematic ages between late-M dwarfs (4.0$\\pm$0.2 Gyr) and L dwarfs (6.5$\\pm$0.4 Gyr) in our sample that are contrary to predictions from prior simulations. This difference appears to be driven by a dispersed population of unusually blue L dwarfs which may be more prevalent in our local volume-limited sample than in deeper magnitude-limited surveys. The L dwarfs exhibit an asymmetric $U$ velocity distribution w...

  12. Estimación de la velocidad de propagación aórtica basada en el análisis de la onda de pulso radial Velocity estimation of aortic propagation based on radial pulse wave analysis

    Directory of Open Access Journals (Sweden)

    Fernando Clara

    2011-06-01

    Full Text Available Se exploró la posibilidad de utilizar la morfología del registro de onda de pulso radial obtenida mediante un transductor de movimiento para evaluar la velocidad de propagación aórtica. Se efectuó el registro de onda de pulso en arteria radial mediante un transductor apoyado sobre la zona de palpación del pulso, sobre un conjunto de 167 voluntarios varones sanos normotensos de edades comprendidas entre la 2ª y la 7ª década. Se identificó en los registros la onda reflejada y se definió un coeficiente de velocidad como el cociente entre la talla del individuo y el tiempo transcurrido entre el máximo de la onda sistólica y el instante de llegada de dicha onda. Se halló que en los normotensos el coeficiente mencionado aumentó en forma lineal con la edad, en una proporción similar al aumento de velocidad de propagación aórtica medido con otros métodos. Se repitió el procedimiento en otro conjunto de 125 varones hipertensos sin otros factores de riesgo, de edades entre la 3ª y la 7ª década, hallándose valores similares a los normotensos solamente en la 3ª década, a partir de la cual se registró un incremento significativo de dicho índice. Tales hallazgos sustentan la factibilidad de utilizar tal tipo de registros para evaluar indirectamente la velocidad de propagación junto con el índice de aumentación, un parámetro habitualmente utilizado en el análisis de onda de pulso.We analyzed the possibility of using the radial pulse wave morphology, obtained by a movement transducer, to evaluate the aortic pulse wave velocity. The radial pulse wave signals were obtained by using a transducer, located on the pulse palpation area, in 167 healthy normotensive male volunteers, ages 20 to 70. The reflected wave was identified in every case. Also, a speed coefficient was defined as the ratio between the individual's height and the time between the maximum systolic wave and the arrival time of the reflected wave. We found that the

  13. 'Modal-noise' in single-mode fibers: A cautionary note for high precision radial velocity instruments

    CERN Document Server

    Halverson, Samuel; Mahadevan, Suvrath; Schwab, Christian

    2015-01-01

    Exploring the use of single-mode fibers (SMFs) in high precision Doppler spectrometers has become increasingly attractive since the advent of diffraction-limited adaptive optics systems on large-aperture telescopes. Spectrometers fed with these fibers can be made significantly smaller than typical 'seeing-limited' instruments, greatly reducing cost and overall complexity. Importantly, classical mode interference and speckle issues associated with multi-mode fibers, also known as 'modal noise', are mitigated when using SMFs, which also provide perfect radial and azimuthal image scrambling. However, these fibers do support multiple polarization modes, an issue that is generally ignored for larger-core fibers given the large number of propagation modes. Since diffraction gratings used in most high resolution astronomical instruments have dispersive properties that are sensitive to incident polarization changes, any birefringence variations in the fiber can cause variations in the efficiency profile, degrading il...

  14. THE BROWN DWARF KINEMATICS PROJECT (BDKP). IV. RADIAL VELOCITIES OF 85 LATE-M AND L DWARFS WITH MagE

    Energy Technology Data Exchange (ETDEWEB)

    Burgasser, Adam J. [Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093 (United States); Logsdon, Sarah E. [Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States); Gagné, Jonathan [Institute for Research on Exoplanets (iREx), Université de Montréal, Département de Physique, C.P. 6128 Succ. Centre-ville, Montréal, QC H3C 3J7 (Canada); Bochanski, John J. [Rider University, 2083 Lawrenceville Road, Lawrenceville, NJ 08648 (United States); Faherty, Jaqueline K. [Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 (United States); West, Andrew A. [Department of Astronomy, Boston University, 725 Commonwealth Avenue Boston, MA 02215 (United States); Mamajek, Eric E. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Schmidt, Sarah J. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Cruz, Kelle L., E-mail: aburgasser@ucsd.edu [Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10034 (United States)

    2015-09-15

    Radial velocity measurements are presented for 85 late M- and L-type very low-mass stars and brown dwarfs obtained with the Magellan Echellette spectrograph. Targets primarily have distances within 20 pc of the Sun, with more distant sources selected for their unusual spectral energy distributions. We achieved precisions of 2–3 km s{sup −1}, and combined these with astrometric and spectrophotometric data to calculate UVW velocities. Most are members of the thin disk of the Galaxy, and velocity dispersions indicate a mean age of 5.2 ± 0.2 Gyr for sources within 20 pc. We find signficantly different kinematic ages between late-M dwarfs (4.0 ± 0.2 Gyr) and L dwarfs (6.5 ± 0.4 Gyr) in our sample that are contrary to predictions from prior simulations. This difference appears to be driven by a dispersed population of unusually blue L dwarfs which may be more prevalent in our local volume-limited sample than in deeper magnitude-limited surveys. The L dwarfs exhibit an asymmetric U velocity distribution with a net inward flow, similar to gradients recently detected in local stellar samples. Simulations incorporating brown dwarf evolution and Galactic orbital dynamics are unable to reproduce the velocity asymmetry, suggesting non-axisymmetric perturbations or two distinct L dwarf populations. We also find the L dwarfs to have a kinematic age-activity correlation similar to more massive stars. We identify several sources with low surface gravities, and two new substellar candidate members of nearby young moving groups: the astrometric binary DENIS J08230313–4912012AB, a low-probability member of the β Pictoris Moving Group; and 2MASS J15104786–2818174, a moderate-probability member of the 30–50 Myr Argus Association.

  15. A laser frequency comb that enables radial velocity measurements with a precision of 1 cm s$^{-1}$

    CERN Document Server

    Li, Chih-Hao; Fendel, Peter; Glenday, Alexander G; Kaertner, Franz X; Phillips, David F; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L

    2008-01-01

    Searches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision of 60 cm/s (ref 1), which is sufficient to find a 5-Earth-mass planet in a Mercury-like orbit around a Sun-like star. To find a 1-Earth-mass planet in an Earthlike orbit, a precision of 5 cm/s is necessary. The combination of a laser frequency comb with a Fabry-Perot filtering cavity has been suggested as a promising approach to achieve such Doppler shift resolution via improved spectrograph wavelength calibration, with recent encouraging results. Here we report the fabrication of such a filtered laser comb with up to 40- GHz (1-A) line spacing, generated from a 1- GHz repetition-rate source, without compromising long-term stability, reproducibility or spectral resolution. This wide-line-spacing comb, or `astro-comb', is well matched to the resolving power of high-resolution astrophysical spectrographs. The astro-comb should allow a precision as high as 1 cm/s in astronomical radial ve...

  16. Radial velocity observations of the 2015 Mar 20 eclipse - A benchmark Rossiter-McLaughlin curve with zero free parameters

    CERN Document Server

    Reiners, Ansgar; Bauer, Florian; Beeck, Benjamin; Huke, Philipp

    2016-01-01

    On March 20, 2015, we obtained 159 spectra of the Sun as a star with the solar telescope and the FTS at the Institut f\\"ur Astrophysik G\\"ottingen, 76 spectra were taken during partial solar eclipse. We obtained RVs using $I_2$ as wavelength reference and determined the RM curve with a peak-to-peak amplitude of almost 1.4 km s$^{-1}$ at typical RV precision better than 1 m s$^{-1}$. We modeled disk-integrated solar RVs using surface velocities, limb darkening, and information about convective blueshift from 3D magneto-hydrodynamic simulations. We confirm that convective blueshift is crucial to understand solar RVs during eclipse. Our best model reproduced the observations to within a relative precision of 10% with residuals less than 30 m s$^{-1}$. We cross-checked parameterizations of velocity fields using a Dopplergram from the Solar Dynamics Observatory and conclude that disk-integration of the Dopplergram does not provide correct information about convective blueshift necessary for m s$^{-1}$ RV work. As ...

  17. SOAP-T: A tool to study the light-curve and radial velocity of a system with a transiting planet and a rotating spotted star

    CERN Document Server

    Oshagh, M; Boué, G; Montalto, M; Santos, N C; Bonfils, X; Haghighipour, N

    2012-01-01

    We present an improved version of SOAP (Boisse et al. 2012) named "SOAP-T", which can generate the radial velocity variations and light-curves for systems consisting of a rotating spotted star with a transiting planet. This tool can be used to study the anomalies inside transit light-curves and the Rossiter-McLaughlin effect, to better constrain the orbital configuration and properties of planetary systems and active zones of their host stars. Tests of the code are presented to illustrate its performance and to validate its capability when compared with analytical models and real data. Finally, we apply SOAP-T to the active star, HAT-P-11, observed by the NASA Kepler space telescope and use this system to discuss the capability of this tool in analyzing light-curves for the cases where the transiting planet overlaps with the star's spots.

  18. SOAP-T: a tool to study the light curve and radial velocity of a system with a transiting planet and a rotating spotted star

    Science.gov (United States)

    Oshagh, M.; Boisse, I.; Boué, G.; Montalto, M.; Santos, N. C.; Bonfils, X.; Haghighipour, N.

    2013-01-01

    We present an improved version of SOAP named "SOAP-T", which can generate the radial velocity variations and light curves for systems consisting of a rotating spotted star with a transiting planet. This tool can be used to study the anomalies inside transit light curves and the Rossiter-McLaughlin effect, to better constrain the orbital configuration and properties of planetary systems and the active zones of their host stars. Tests of the code are presented to illustrate its performance and to validate its capability when compared with analytical models and real data. Finally, we apply SOAP-T to the active star, HAT-P-11, observed by the NASA Kepler space telescope and use this system to discuss the capability of this tool in analyzing light curves for the cases where the transiting planet overlaps with the star's spots. The tool's public interface is available at http://www.astro.up.pt/resources/soap-t/

  19. TRADES: a new software to derive orbital parameters from observed Transit Times and Radial Velocities. Revisiting Kepler-11 and Kepler-9

    CERN Document Server

    Borsato, Luca; Nascimbeni, Valerio; Piotto, Giampaolo; Granata, Valentina; Bedin, Luigi Rolly; Malavolta, Luca

    2014-01-01

    Aims. With the purpose of determining the orbital parameters of exoplanetary systems from observational data, we have developed a software, named TRADES (TRAnsits and Dynamics of Exoplanetary Systems) to simultaneously fit observed radial velocities and transit times data. Methods. We implemented a dynamical simulator for N-body system which also fits the available data during the orbital integration and determines the best combination of the orbital parameters using grid search, $\\chi^2$ minimization, genetic algorithms, particle swarm optimization, and bootstrap analysis. Results. To validate TRADES, we tested the code on a synthetic three-body system and on two real systems discovered by the Kepler mission: Kepler-9 and Kepler-11. These systems are good benchmarks to test multiple exoplanet systems showing transit time variations (TTVs) due to the gravitational interaction among planets. We have found orbital parameters of Kepler-11 planets in good agreement with the values proposed in the discovery paper ...

  20. Precise Stellar Radial Velocities of an M Dwarf with a Michelson Interferometer and a Medium-resolution Near-infrared Spectrograph

    CERN Document Server

    Muirhead, Philip S; Erskine, David J; Wright, Jason T; Muterspaugh, Matthew W; Covey, Kevin R; Wishnow, Edward H; Hamren, Katherine; Andelson, Phillip; Kimber, David; Mercer, Tony; Halverson, Sam; Vanderburg, Andrew; Mondo, Danny; Czeszumska, Agnieszka; Lloyd, James P

    2011-01-01

    Precise infrared radial velocimetry enables the detection and transit verification of low mass extrasolar planets orbiting mid-to-late M dwarf hosts, which are too faint for V-band radial velocity surveys. The TripleSpec Exoplanet Discovery Instrument, or TEDI, is the combination of a variable-delay Michelson interferometer and a medium-resolution (R=2700) near-infrared spectrograph on the Palomar 200" Hale Telescope. We used TEDI to monitor GJ 699, a nearby mid-M dwarf, over 11 nights spread across 3 months. Analysis of 106 independent observations reveals a root-mean-square precision of less than 37 m/s for 5 minutes of integration time. This performance is within a factor of 2 of our expected photon-limited precision. We further decompose the residuals into a 33 m/s white noise component, and a 15 m/s systematic noise component, which we identify as likely due to contamination by telluric absorption lines. With further development this technique holds promise for broad implementation on medium-resolution n...

  1. Synthesizing Exoplanet Demographics: A Single Population of Long-period Planetary Companions to M Dwarfs Consistent with Microlensing, Radial Velocity, and Direct Imaging Surveys

    Science.gov (United States)

    Clanton, Christian; Gaudi, B. Scott

    2016-03-01

    We present the first study to synthesize results from five different exoplanet surveys using three independent detection methods: microlensing, radial velocity, and direct imaging. The constraints derived herein represent the most comprehensive picture of the demographics of large-separation (≳2 AU) planets orbiting the most common stars in our Galaxy that has been constructed to date. We assume a simple, joint power-law planet distribution function of the form {d}2{N}{{pl}}/(d{log} {m}p d{log} a)={ A }{({m}p/{M}{{Sat}})}α {(a/2.5{{AU}})}β with an outer cutoff radius of the separation distribution function of aout. Generating populations of planets from these models and mapping them into the relevant observables for each survey, we use actual or estimated detection sensitivities to determine the expected observations for each survey. Comparing with the reported results, we derive constraints on the parameters \\{α ,β ,{ A },{a}{{out}}\\} that describe a single population of planets that is simultaneously consistent with the results of microlensing, radial velocity, and direct imaging surveys. We find median and 68% confindence intervals of α =-{0.86}-0.19+0.21 (-{0.85}-0.19+0.21), β ={1.1}-1.4+1.9 ({1.1}-1.3+1.9), { A }={0.21}-0.15+0.20 {{dex}}-2 ({0.21}-0.15+0.20 {{dex}}-2), and {a}{{out}}={10}-4.7+26 AU ({12}-6.2+50 AU) assuming “hot-start” (“cold-start”) planet evolutionary models. These values are consistent with all current knowledge of planets on orbits beyond ∼2 AU around single M dwarfs.

  2. A radial velocity survey of low Galactic latitude structures: II. The Monoceros Ring behind the Canis Major dwarf galaxy

    CERN Document Server

    Conn, B C; Lewis, G F; Ibata, R A; Bellazzini, M; Irwin, M J; Conn, Blair C.; Martin, Nicolas F.; Lewis, Geraint F.; Ibata, Rodrigo A.; Bellazzini, Michele; Irwin, Mike J.

    2005-01-01

    An AAT/2dF Spectrograph Survey of low Galactic latitudes targeting the putative Canis Major dwarf galaxy, and the (possibly) associated tidal debris of stars known as the Monoceros Ring, covering Galactic coordinates 231.5$^{\\circ}< ${\\it l} $<$ 247.5$^{\\circ}$ and -11.8$^{\\circ}<${\\it b}$<-3.8^{\\circ}$, has revealed the presence of the Monoceros Ring in the background of the Canis Major dwarf galaxy. This detection resides at a galactocentric distance of $\\sim18.9\\pm$0.3\\kpc (13.5$\\pm$0.3\\kpc heliocentric), exhibiting a velocity of $\\sim132.8\\pm$1.3 $\\kms$ with a dispersion of $\\sim22.7\\pm1.7\\kms$; both of these comparable with previous measurements of the Monoceros Ring in nearby fields. This detection highlights the increasing complexity of structure being revealed in recent surveys of the Milky Way thick disk and Halo.

  3. A New Calculation Method of the Axial and Radial Velocity and Grade—Efficiency for High—Efficiency Cyclones

    Institute of Scientific and Technical Information of China (English)

    ZhangCOngzhi; WangZijie

    1995-01-01

    At present in China,the cyclones are widely used in the dust removal ventilation system of boilers,industry funaces of pits etc.,because of their simple structure,long life and cost efficiency,In order to improve efficiency of the cyclones,new theoretical calculation method is very important.In this paper,the concept of down-flow quantity is introduced and new formula is decuted based on Kilven law and the work has done by Zhao Weizhong[1],The formula is not only of advantage theoretically but also fit with experimental results quite well.On the basis,the effect of three-dimensional velocity distribution in the flow field within cyclones and other parameters on the grade-efficiency calcuation are analyzed and a new equation for grade-efficiency estimation is introduced.The calculating accuracy of the equation is better than the others theoretically and experimentally.

  4. Ground-based observations of exoplanet atmospheres

    NARCIS (Netherlands)

    Mooij, Ernst Johan Walter de

    2011-01-01

    This thesis focuses on the properties of exoplanet atmospheres. The results for ground-based near-infrared secondary eclipse observations of three different exoplanets, TrES-3b, HAT-P-1b and WASP-33b, are presented which have been obtained with ground-based telescopes as part of the GROUSE project.

  5. Ground-based observations of exoplanet atmospheres

    NARCIS (Netherlands)

    Mooij, Ernst Johan Walter de

    2011-01-01

    This thesis focuses on the properties of exoplanet atmospheres. The results for ground-based near-infrared secondary eclipse observations of three different exoplanets, TrES-3b, HAT-P-1b and WASP-33b, are presented which have been obtained with ground-based telescopes as part of the GROUSE project.

  6. Estimation of C*-Integral for Radial Cracks in Annular Discs under Constant Angular Velocity and Internal Pressure

    Directory of Open Access Journals (Sweden)

    A. R. Gowhari-Anaraki

    2008-01-01

    Full Text Available The finite element method has been used to predict the creep rupture parameter, C*-Integral for single and double-edge cracks in eight annular rotating discs under constant angular velocity with and without internal pressure. In this study, a new dimensionless creeping crack configuration factor, Q* has been introduced. Power law creeping finite element analyses have been performed and the results are presented in the form of Q* for a wide range of components and crack geometry parameters. These parameters are chosen to be representative of typical practical situations and have been determined from evidence presented in the open literature. The extensive range of Q* obtained from the analyses are then used to obtain equivalent prediction equations using a statistical multiple non-linear regression model. The predictive equations for Q*, can also be used easily to calculate the C*-Integral values for extensive range of geometric parameters. The C*-Integral values obtained from predictive equations were also compared with those obtained from reference stress method (RSM. Finally, creep zone growth behavior was studied in the component during transient time.

  7. Toward Complete Statistics of Massive Binary Stars: Penultimate Results from the Cygnus OB2 Radial Velocity Survey

    Science.gov (United States)

    Kobulnicky, Henry A.; Kiminki, Daniel C.; Lundquist, Michael J.; Burke, Jamison; Chapman, James; Keller, Erica; Lester, Kathryn; Rolen, Emily K.; Topel, Eric; Bhattacharjee, Anirban; Smullen, Rachel A.; Vargas Álvarez, Carlos A.; Runnoe, Jessie C.; Dale, Daniel A.; Brotherton, Michael M.

    2014-08-01

    We analyze orbital solutions for 48 massive multiple-star systems in the Cygnus OB2 association, 23 of which are newly presented here, to find that the observed distribution of orbital periods is approximately uniform in log P for P power law provides a statistically compelling prescription, but if features are ignored, a power law with exponent β ~= -0.22 provides a crude approximation over P = 1.4-2000 days, as does a piece-wise linear function with a break near 45 days. The cumulative period distribution flattens at P > 45 days, even after correction for completeness, indicating either a lower binary fraction or a shift toward low-mass companions. A high degree of similarity (91% likelihood) between the Cyg OB2 period distribution and that of other surveys suggests that the binary properties at P period P < 45 days. Completeness corrections imply a binary fraction near 55% for P < 5000 days. The observed distribution of mass ratios 0.2 < q < 1 is consistent with uniform, while the observed distribution of eccentricities 0.1 < e < 0.6 is consistent with uniform plus an excess of e ~= 0 systems. We identify six stars, all supergiants, that exhibit aperiodic velocity variations of ~30 km s-1 attributed to atmospheric fluctuations.

  8. Vetting Galactic Leavitt Law Calibrators Using Radial Velocities: On the Variability, Binarity, and Possible Parallax Error of 19 Long-period Cepheids

    Science.gov (United States)

    Anderson, R. I.; Casertano, S.; Riess, A. G.; Melis, C.; Holl, B.; Semaan, T.; Papics, P. I.; Blanco-Cuaresma, S.; Eyer, L.; Mowlavi, N.; Palaversa, L.; Roelens, M.

    2016-10-01

    We investigate the radial velocity (RV) variability and spectroscopic binarity of 19 Galactic long-period ({P}{puls} ≳ 10 days) classical Cepheid variable stars whose trigonometric parallaxes are being measured using the Hubble Space Telescope and Gaia. Our primary objective is to constrain possible parallax error due to undetected orbital motion. Using over 1600 high-precision RVs measured between 2011 and 2016, we find no indication of orbital motion on ≲5 year timescales for 18 Cepheids and determine upper limits on allowed configurations for a range of input orbital periods. The results constrain the unsigned parallax error due to orbital motion to 10 years) variations in pulsation-averaged velocity v γ via a template fitting approach using both new and literature RVs. We discover the spectroscopic binarity of XZ Car and CD Cyg, find first tentative evidence for AQ Car, and reveal KN Cen’s orbital signature. Further (mostly tentative) evidence of time-variable v γ is found for SS CMa, VY Car, SZ Cyg, and X Pup. We briefly discuss considerations regarding a vetting process of Galactic Leavitt law calibrators and show that light contributions by companions are insignificant for most distance scale applications.

  9. Vetting Galactic Leavitt Law Calibrators using Radial Velocities: On the Variability, Binarity, and Possible Parallax Error of 19 Long-period Cepheids

    CERN Document Server

    Anderson, R I; Riess, A G; Melis, C; Holl, B; Semaan, T; Papics, P I; Blanco-Cuaresma, S; Eyer, L; Mowlavi, N; Palaversa, L; Roelens, M

    2016-01-01

    We investigate the radial velocity (RV) variability and spectroscopic binarity of 19 Galactic long-period ($P_{\\rm{puls}} \\gtrsim 10$ d) classical Cepheid variable stars whose trigonometric parallaxes are being measured using the Hubble Space Telescope and Gaia. Our primary objective is to constrain possible parallax error due to undetected orbital motion. Using $>1600$ high-precision RVs measured between 2011 and 2016, we find no indication of orbital motion on $\\lesssim 5$ yr timescales for 18 Cepheids and determine upper limits on allowed configurations for a range of input orbital periods. The results constrain the unsigned parallax error due to orbital motion to $ 10$ yr) variations in pulsation-averaged velocity $v_\\gamma$ via a template fitting approach using both new and literature RVs. We discover the spectroscopic binarity of XZ Car and CD Cyg, find first tentative evidence for AQ Car, and reveal KN Cen's orbital signature. Further (mostly tentative) evidence of time-variable $v_\\gamma$ is found for...

  10. Effect of reactive hyperemia on carotid-radial pulse wave velocity in hypertensive participants and direct comparison with flow-mediated dilation: a pilot study.

    Science.gov (United States)

    Kamran, Haroon; Salciccioli, Louis; Ko, Eun Hee; Qureshi, Ghazanfar; Kazmi, Haris; Kassotis, John; Lazar, Jason

    2010-01-01

    This pilot study assessed the effects of hyperemia on carotid-radial pulse wave velocity (PWV) in 39 normotensive (NT) and 23 hypertensive (HT) participants using applanation tonometry. Pulse wave velocity was measured at 1- and at 2-minute intervals. Baseline PWV was similar between the groups (P = .59). At 1 minute, PWV decreased (8.5 +/- 1.2 to 7.1 +/- 1.4 m/s, P < .001) in NT but not in HT (P = .83). Hyperemic PWV (DeltaPWV) response differed between the groups (-16% vs + 1.0%, P < .001). On multivariate analysis, HT, not age or blood pressure was independently related to DeltaPWV (R(2) = .43, P < .01). Among patients with cardiovascular risk factors/disease, DeltaPWV was inversely related to flow-mediated dilation (FMD; R( 2) = .43, P < .003). hyperemia decreases PWV(1min) in NT but not in HT. DeltaPWV is inversely related to FMD. Blunted hyperemic PWV response may represent impaired vasodilatory reserve.

  11. A Versatile Technique to Enable sub-milli-Kelvin Instrument Stability for Precise Radial Velocity Measurements: Tests with the Habitable-zone Planet Finder

    CERN Document Server

    Stefansson, Gudmundur; Robertson, Paul; Mahadevan, Suvrath; Anderson, Tyler; Levi, Eric; Bender, Chad; Nelson, Matthew; Monson, Andrew; Blank, Basil; Halverson, Samuel; Henderson, Chuck; Ramsey, Lawrence; Roy, Arpita; Schwab, Christian; Terrien, Ryan

    2016-01-01

    Insufficient instrument thermo-mechanical stability is one of the many roadblocks for achieving 10cm/s Doppler radial velocity (RV) precision, the precision needed to detect Earth-twins orbiting Solar-type stars. Highly temperature and pressure stabilized spectrographs allow us to better calibrate out instrumental drifts, thereby helping in distinguishing instrumental noise from astrophysical stellar signals. We present the design and performance of the Environmental Control System (ECS) for the Habitable-zone Planet Finder (HPF), a high-resolution (R=50,000) fiber-fed near infrared (NIR) spectrograph for the 10m Hobby Eberly Telescope at McDonald Observatory. HPF will operate at 180K, driven by the choice of an H2RG NIR detector array with a 1.7micron cutoff. This ECS has demonstrated 0.6mK RMS stability over 15 days at both 180K and 300K, and maintained high quality vacuum (<$10^{-7}$Torr) over months, during long-term stability tests conducted without a planned passive thermal enclosure surrounding the ...

  12. The conjectured S-type retrograde planet in nu Octantis: more evidence including four years of iodine-cell radial velocities

    CERN Document Server

    Ramm, D J; Endl, M; Hearnshaw, J B; Wittenmyer, R A; Gunn, F; Bergmann, C; Kilmartin, P; Brogt, E

    2016-01-01

    We report 1212 radial-velocity (RV) measurements obtained in the years 2009-2013 using an iodine cell for the spectroscopic binary nu Octantis (K1III/IV). This system (a_bin~2.6 au, P~1050 days) is conjectured to have a Jovian planet with a semi-major axis half that of the binary host. The extreme geometry only permits long-term stability if the planet is in a retrograde orbit. Whilst the reality of the planet (P~415 days) remains uncertain, other scenarios (stellar variability or apsidal motion caused by a yet unobserved third star) continue to appear substantially less credible based on CCF bisectors, line-depth ratios and many other independent details. If this evidence is validated but the planet is disproved, the claims of other planets using RVs will be seriously challenged. We also describe a significant revision to the previously published RVs and the full set of 1437 RVs now encompasses nearly 13 years. The sensitive orbital dynamics allow us to constrain the three-dimensional architecture with a bro...

  13. A High-precision Near-infrared Survey for Radial Velocity Variable Low-mass Stars Using CSHELL and a Methane Gas Cell

    Science.gov (United States)

    Gagné, Jonathan; Plavchan, Peter; Gao, Peter; Anglada-Escude, Guillem; Furlan, Elise; Davison, Cassy; Tanner, Angelle; Henry, Todd J.; Riedel, Adric R.; Brinkworth, Carolyn; Latham, David; Bottom, Michael; White, Russel; Mills, Sean; Beichman, Chas; Johnson, John A.; Ciardi, David R.; Wallace, Kent; Mennesson, Bertrand; von Braun, Kaspar; Vasisht, Gautam; Prato, Lisa; Kane, Stephen R.; Mamajek, Eric E.; Walp, Bernie; Crawford, Timothy J.; Rougeot, Raphaël; Geneser, Claire S.; Catanzarite, Joseph

    2016-05-01

    We present the results of a precise near-infrared (NIR) radial velocity (RV) survey of 32 low-mass stars with spectral types K2-M4 using CSHELL at the NASA InfraRed Telescope Facility in the K band with an isotopologue methane gas cell to achieve wavelength calibration and a novel, iterative RV extraction method. We surveyed 14 members of young (≈25-150 Myr) moving groups, the young field star ɛ Eridani, and 18 nearby (GJ 876 bc and independently retrieve orbital parameters consistent with previous studies. We recovered RV variabilities for HD 160934 AB and GJ 725 AB that are consistent with their known binary orbits, and nine other targets are candidate RV variables with a statistical significance of 3σ-5σ. Our method, combined with the new iSHELL spectrograph, will yield long-term RV precisions of ≲5 m s-1 in the NIR, which will allow the detection of super-Earths near the habitable zone of mid-M dwarfs.

  14. Combining direct imaging and radial velocity data towards a full exploration of the giant planet population. I. Method and first results

    Science.gov (United States)

    Lannier, J.; Lagrange, A. M.; Bonavita, M.; Borgniet, S.; Delorme, P.; Meunier, N.; Desidera, S.; Messina, S.; Chauvin, G.; Keppler, M.

    2017-07-01

    Context. Thanks to the detections of more than 3000 exoplanets these last 20 yr, statistical studies have already highlighted some properties of the distribution of the planet parameters. Nevertheless, few studies have yet investigated the planet populations from short to large separations around the same star since this requires the use of different detection techniques that usually target different types of stars. Aims: We wish to develop a tool that combines direct and indirect methods so as to correctly investigate the giant planet populations at all separations. Methods: We developed the MESS2 code, a Monte Carlo simulation code combining radial velocity and direct imaging data obtained at different epochs for a given star to estimate the detection probability of giant planets spanning a wide range of physical separations. It is based on the generation of synthetic planet populations. Results: We apply MESS2 on a young M1-type, the nearby star AU Mic observed with HARPS and NACO/ESO. We show that giant planet detection limits are significantly improved at intermediate separations (≈20 au in the case of AU Mic). We show that the traditional approach of analyzing the RV and DI detection limits independently systematically overestimates the planet detection limits and hence planet occurrence rates. The use of MESS2 allows us to obtain correct planet occurrence rates in statistical studies, making use of multi-epoch DI data and/or RV measurements. We also show that MESS2 can optimize the schedule of future DI observations.

  15. Kepler 18-b, c, and d: A System Of Three Planets Confirmed by Transit Timing Variations, Lightcurve Validation, Spitzer Photometry and Radial Velocity Measurements

    CERN Document Server

    Cochran, William D; Torres, Guillermo; Fressin, Francois; Desert, Jean-Michel; Ragozzine, Darin; Sasselov, Dimitar; Fortney, Jonathan J; Rowe, Jason F; Brugamyer, Erik J; Bryson, Stephen T; Carter, Joshua A; Ciardi, David R; Howell, Steve B; Steffen, Jason H; Borucki, William J; Koch, David G; Winn, Joshua N; Welsh, William F; Uddin, Kamal; Tenenbaum, Peter; Still, M; Seager, Sara; Quinn, Samuel N; Mullally, F; Miller, Neil; Marcy, Geoffrey W; MacQueen, Phillip J; Lucas, Philip; Lissauer, Jack J; Latham, David W; Knutson, Heather; Kinemuchi, K; Johnson, John A; Jenkins, Jon M; Isaacson, Howard; Howard, Andrew; Horch, Elliott; Holman, Matthew J; Henze, Christopher E; Haas, Michael R; Gilliland, Ronald L; Gautier, Thomas N; Ford, Eric B; Fischer, Debra A; Everett, Mark; Endl, Michael; Demory, Brice-Oliver; Deming, Drake; Charbonneau, David; Caldwell, Douglas; Buchhave, Lars; Brown, Timothy M; Batalha, Natalie

    2011-01-01

    We report the detection of three transiting planets around a Sunlike star, which we designate Kepler-18. The transit signals were detected in photometric data from the Kepler satellite, and were confirmed to arise from planets using a combination of large transit-timing variations, radial-velocity variations, Warm-Spitzer observations, and statistical analysis of false-positive probabilities. The Kepler-18 star has a mass of 0.97M_sun, radius 1.1R_sun, effective temperature 5345K, and iron abundance [Fe/H]= +0.19. The planets have orbital periods of approximately 3.5, 7.6 and 14.9 days. The innermost planet "b" is a "super-Earth" with mass 6.9 \\pm 3.4M_earth, radius 2.00 \\pm 0.10R_earth, and mean density 4.9 \\pm 2.4 g cm^-3. The two outer planets "c" and "d" are both low-density Neptune-mass planets. Kepler-18c has a mass of 17.3 \\pm 1.9M_earth, radius 5.49 \\pm 0.26R_earth, and mean density 0.59 \\pm 0.07 g cm^-3, while Kepler-18d has a mass of 16.4 \\pm 1.4M_earth, radius 6.98 \\pm 0.33R_earth, and mean density...

  16. On the radial velocity detection of additional planets in transiting, slowly rotating M-dwarf systems: the case of GJ 1132

    CERN Document Server

    Cloutier, Ryan; Menou, Kristen; Delfosse, Xavier; Dumusque, Xavier; Artigau, Étienne

    2016-01-01

    M-dwarfs are known to commonly host high-multiplicity planetary systems. Therefore M-dwarf planetary systems with a known transiting planet are expected to contain additional small planets ($r_p \\le 4$ R$_{\\oplus}$, $m_p \\lesssim 20$ M$_{\\oplus}$) that are not seen in transit. In this study we investigate the effort required to detect such planets using precision velocimetry around the sizable subset of M-dwarfs which are slowly rotating ($P_{\\mathrm{rot}} \\gtrsim 40$ days) and hence more likely to be inactive. We focus on the test case of GJ 1132. Specifically, we perform a suite of Monte-Carlo simulations of the star's radial velocity signal featuring astrophysical contributions from stellar jitter due to rotationally modulated active regions and keplarian signals from the known transiting planet and hypothetical additional planets not seen in transit. We then compute the detection completeness of non-transiting planets around GJ 1132 and consequently estimate the number of RV measurements required to detec...

  17. Synthesizing Exoplanet Demographics: A Single Population of Long-Period Planetary Companions to M Dwarfs Consistent with Microlensing, Radial Velocity, and Direct Imaging Surveys

    CERN Document Server

    Clanton, Christian

    2015-01-01

    We present the first study to synthesize results from five different exoplanet surveys using three independent detection methods: microlensing, radial velocity, and direct imaging. The constraints derived herein represent the most comprehensive picture of the demographics of large-separation (>~ 2 AU) planets orbiting the most common stars in our Galaxy that has been constructed to date. We assume a simple, joint power-law planet distribution function of the form d^2N_{pl}/[dlog(m_p)dlog(a)] = A(m_p/M_{Sat})^{alpha}(a/2.5 AU)^{beta} with an outer cutoff radius of the separation distribution function of a_{out}. Generating populations of planets from these models and mapping them into the relevant observables for each survey, we use actual or estimated detection sensitivities to determine the expected observations for each survey. Comparing with the reported results, we derive constraints on the parameters {alpha, beta, A, a_{out}} that describe a single population of planets that is simultaneously consistent ...

  18. The Magellan PFS Planet Search Program: Radial Velocity and Stellar Abundance Analyses of the 360 AU, Metal-Poor Binary "Twins" HD 133131A & B

    CERN Document Server

    Teske, Johanna K; Vogt, Steve S; Díaz, Matías; Butler, R Paul; Crane, Jeffrey D; Thompson, Ian B; Arriagada, Pamela

    2016-01-01

    We present a new precision radial velocity (RV) dataset that reveals multiple planets orbiting the stars in the $\\sim$360 AU, G2$+$G2 "twin" binary HD 133131AB. Our 6 years of high-resolution echelle observations from MIKE and 5 years from PFS on the Magellan telescopes indicate the presence of two eccentric planets around HD 133131A with minimum masses of 1.43$\\pm$0.03 and 0.63$\\pm$0.15 $\\mathcal{M}_{\\rm J}$ at 1.44$\\pm$0.005 and 4.79$\\pm$0.92 AU, respectively. Additional PFS observations of HD 133131B spanning 5 years indicate the presence of one eccentric planet of minimum mass 2.50$\\pm$0.05 $\\mathcal{M}_{\\rm J}$ at 6.40$\\pm$0.59 AU, making it one of the longest period planets detected with RV to date. These planets are the first to be reported primarily based on data taken with PFS on Magellan, demonstrating the instrument's precision and the advantage of long-baseline RV observations. We perform a differential analysis between the Sun and each star, and between the stars themselves, to derive stellar par...

  19. MARVELS-1: A face-on double-lined binary star masquerading as a resonant planetary system; and consideration of rare false positives in radial velocity planet searches

    CERN Document Server

    Wright, Jason T; Mahadevan, Suvrath; Wang, Sharon X; Ford, Eric B; Payne, Matt; Lee, Brian L; Wang, Ji; Crepp, Justin R; Gaudi, B Scott; Eastman, Jason; Pepper, Joshua; Ge, Jian; Fleming, Scott W; Ghezzi, Luan; Gonzalez-Hernandez, Jonay I; Cargile, Phillip; Stassun, Keivan G; Wisniewski, John; Dutra-Ferreira, Leticia; de Mello, Gustavo F Porto; Maia, Marcio A G; da Costa, Luiz Nicolaci; Ogando, Ricardo L C; Santiago, Basilio X; Schneider, Donald P; Hearty, Fred R

    2013-01-01

    We have analyzed new and previously published radial velocity observations of MARVELS-1, known to have an ostensibly substellar companion in a ~6- day orbit. We find significant (~100 m/s) residuals to the best-fit model for the companion, and these residuals are naively consistent with an interior giant planet with a P = 1.965d in a nearly perfect 3:1 period commensuribility (|Pb/Pc - 3| < 10^{-4}). We have performed several tests for the reality of such a companion, including a dynamical analysis, a search for photometric variability, and a hunt for contaminating stellar spectra. We find many reasons to be critical of a planetary interpretation, including the fact that most of the three-body dynamical solutions are unstable. We find no evidence for transits, and no evidence of stellar photometric variability. We have discovered two apparent companions to MARVELS-1 with adaptive optics imaging at Keck; both are M dwarfs, one is likely bound, and the other is likely a foreground object. We explore false-al...

  20. MARVELS-1: A Face-on Double-lined Binary Star Masquerading as a Resonant Planetary System and Consideration of Rare False Positives in Radial Velocity Planet Searches

    Science.gov (United States)

    Wright, Jason T.; Roy, Arpita; Mahadevan, Suvrath; Wang, Sharon X.; Ford, Eric B.; Payne, Matt; Lee, Brian L.; Wang, Ji; Crepp, Justin R.; Gaudi, B. Scott; Eastman, Jason; Pepper, Joshua; Ge, Jian; Fleming, Scott W.; Ghezzi, Luan; González-Hernández, Jonay I.; Cargile, Phillip; Stassun, Keivan G.; Wisniewski, John; Dutra-Ferreira, Leticia; Porto de Mello, Gustavo F.; Maia, Márcio A. G.; Nicolaci da Costa, Luiz; Ogando, Ricardo L. C.; Santiago, Basilio X.; Schneider, Donald P.; Hearty, Fred R.

    2013-06-01

    We have analyzed new and previously published radial velocity (RV) observations of MARVELS-1, known to have an ostensibly substellar companion in a ~6 day orbit. We find significant (~100 m s-1) residuals to the best-fit model for the companion, and these residuals are naïvely consistent with an interior giant planet with a P = 1.965 days in a nearly perfect 3:1 period commensurability (|Pb /Pc - 3| MARVELS-1 with adaptive optics imaging at Keck; both are M dwarfs, one is likely bound, and the other is likely a foreground object. We explore false-alarm scenarios inspired by various curiosities in the data. Ultimately, a line profile and bisector analysis lead us to conclude that the ~100 m s-1 residuals are an artifact of spectral contamination from a stellar companion contributing ~15%-30% of the optical light in the system. We conclude that origin of this contamination is the previously detected RV companion to MARVELS-1, which is not, as previously reported, a brown dwarf, but in fact a G dwarf in a face-on orbit.

  1. The Posterior Distribution of sin(i) for Exoplanets with M_T sin(i) Determined from Radial Velocity Data

    CERN Document Server

    Ho, Shirley

    2010-01-01

    Radial velocity (RV) observations of an exoplanet system giving a value of M_T sin(i) condition (ie. give information about) not only the planet's true mass M_T but also the value of sin(i) for that system (where i is the orbital inclination angle). Thus the value of sin(i) for a system with any particular observed value of M_T sin(i) cannot be assumed to be drawn randomly from a distribution corresponding to an isotropic i distribution, i.e. the presumptive prior distribution . Rather, the posterior distribution from which it is drawn depends on the intrinsic distribution of M_T for the exoplanet population being studied. We give a simple Bayesian derivation of this relationship and apply it to several "toy models" for the (currently unknown) intrinsic distribution of M_T. The results show that the effect can be an important one. For example, even for simple power-law distributions of M_T, the median value of sin(i) in an observed RV sample can vary between 0.860 and 0.023 (as compared to the 0.866 value for...

  2. Precise radial velocities of giant stars. IX. HD 59686 Ab: a massive circumstellar planet orbiting a giant star in a 13.6 au eccentric binary system

    Science.gov (United States)

    Ortiz, Mauricio; Reffert, Sabine; Trifonov, Trifon; Quirrenbach, Andreas; Mitchell, David S.; Nowak, Grzegorz; Buenzli, Esther; Zimmerman, Neil; Bonnefoy, Mickaël; Skemer, Andy; Defrère, Denis; Lee, Man Hoi; Fischer, Debra A.; Hinz, Philip M.

    2016-10-01

    Context. For over 12 yr, we have carried out a precise radial velocity (RV) survey of a sample of 373 G- and K-giant stars using the Hamilton Échelle Spectrograph at the Lick Observatory. There are, among others, a number of multiple planetary systems in our sample as well as several planetary candidates in stellar binaries. Aims: We aim at detecting and characterizing substellar and stellar companions to the giant star HD 59686 A (HR 2877, HIP 36616). Methods: We obtained high-precision RV measurements of the star HD 59686 A. By fitting a Keplerian model to the periodic changes in the RVs, we can assess the nature of companions in the system. To distinguish between RV variations that are due to non-radial pulsation or stellar spots, we used infrared RVs taken with the CRIRES spectrograph at the Very Large Telescope. Additionally, to characterize the system in more detail, we obtained high-resolution images with LMIRCam at the Large Binocular Telescope. Results: We report the probable discovery of a giant planet with a mass of mp sin i = 6.92-0.24+0.18 MJup orbiting at ap = 1.0860-0.0007+0.0006 au from the giant star HD 59686 A. In addition to the planetary signal, we discovered an eccentric (eB = 0.729-0.003+0.004) binary companion with a mass of mB sin i = 0.5296-0.0008+0.0011 M⊙ orbiting at a close separation from the giant primary with a semi-major axis of aB = 13.56-0.14+0.18 au. Conclusions: The existence of the planet HD 59686 Ab in a tight eccentric binary system severely challenges standard giant planet formation theories and requires substantial improvements to such theories in tight binaries. Otherwise, alternative planet formation scenarios such as second-generation planets or dynamical interactions in an early phase of the system's lifetime need to be seriously considered to better understand the origin of this enigmatic planet. Based on observations collected at the Lick Observatory, University of California.Based on observations collected at the

  3. MARVELS-1: A FACE-ON DOUBLE-LINED BINARY STAR MASQUERADING AS A RESONANT PLANETARY SYSTEM AND CONSIDERATION OF RARE FALSE POSITIVES IN RADIAL VELOCITY PLANET SEARCHES

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Jason T.; Roy, Arpita; Mahadevan, Suvrath; Wang, Sharon X.; Fleming, Scott W. [Center for Exoplanets and Habitable Worlds, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16802 (United States); Ford, Eric B.; Payne, Matt; Lee, Brian L.; Ge, Jian [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055 (United States); Wang, Ji [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Crepp, Justin R. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556-5670 (United States); Gaudi, B. Scott; Eastman, Jason [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Pepper, Joshua; Cargile, Phillip; Stassun, Keivan G. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Ghezzi, Luan [Observatorio Nacional, Rua General Jose Cristino, 77, Rio de Janeiro, RJ 20921-400 (Brazil); Gonzalez-Hernandez, Jonay I. [Instituto de Astrofisica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain); Wisniewski, John [HL Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W Brooks St, Norman, OK 73019 (United States); Dutra-Ferreira, Leticia, E-mail: jtwright@astro.psu.edu [Laboratorio Interinstitucional de e-Astronomia (LIneA), Rua General Jose Cristino 77, Rio de Janeiro, RJ 20921-400 (Brazil); and others

    2013-06-20

    We have analyzed new and previously published radial velocity (RV) observations of MARVELS-1, known to have an ostensibly substellar companion in a {approx}6 day orbit. We find significant ({approx}100 m s{sup -1}) residuals to the best-fit model for the companion, and these residuals are naievely consistent with an interior giant planet with a P = 1.965 days in a nearly perfect 3:1 period commensurability (|P{sub b} /P{sub c} - 3| < 10{sup -4}). We have performed several tests for the reality of such a companion, including a dynamical analysis, a search for photometric variability, and a hunt for contaminating stellar spectra. We find many reasons to be critical of a planetary interpretation, including the fact that most of the three-body dynamical solutions are unstable. We find no evidence for transits, and no evidence of stellar photometric variability. We have discovered two apparent companions to MARVELS-1 with adaptive optics imaging at Keck; both are M dwarfs, one is likely bound, and the other is likely a foreground object. We explore false-alarm scenarios inspired by various curiosities in the data. Ultimately, a line profile and bisector analysis lead us to conclude that the {approx}100 m s{sup -1} residuals are an artifact of spectral contamination from a stellar companion contributing {approx}15%-30% of the optical light in the system. We conclude that origin of this contamination is the previously detected RV companion to MARVELS-1, which is not, as previously reported, a brown dwarf, but in fact a G dwarf in a face-on orbit.

  4. Accurate Group Delay Measurement for Radial Velocity Instruments Using the Dispersed Fixed Delay Interferometer Method. II. Application of Heterodyne Combs Using an External Interferometer Filter

    Science.gov (United States)

    Wang, Ji; Ge, Jian; Wan, Xiaoke; De Lee, Nathan; Lee, Brian

    2012-11-01

    A fixed delay interferometer is the key component in a DFDI (dispersed fixed delay interferometer) instrument for an exoplanet search using the radial velocity (RV) technique. Although the group delay (GD) of the interferometer can be measured with white light combs (WLCs), the measurement precision is limited by the comb visibility, and the wavelength coverage is constrained by the comb sampling. For instance, this method can calibrate only half of the SDSS-III MARVELS spectra and reach a precision of 2.2 m s-1. This article introduces an innovative method using a sine source for precision delay calibration over very broad wavelengths. The sine source is made of a monolithic Michelson interferometer fed with white light. The interferometer modulated white light (in a sinusoidal form) is fed into a DFDI instrument for calibration. Due to an optimal GD of the sine source, Fourier components from the DFDI interferometer, the sine source, and their frequency beating can be clearly separated and effectively extracted with a chirped Fourier transform to allow precision measurements of the interferometer GD over the entire range of operation wavelengths. The measurements of the MARVELS interferometer with a sine source show that this new calibration method has improved the wavelength coverage by a factor of 2 and the precision by a factor of 3. The RV measurement error induced by GD measurement uncertainties is controlled to be less than 1 m s-1, which has met the requirements for MARVELS moderate-to-high Doppler precision (∼5–30 m s-1) for exoplanet search around V ∼ 8–12 solar-type stars. Heterodyne combs using an external interferometer source can be applied in other areas of optics measurement and calibration.

  5. Search for Exoplanets around Northern Circumpolar Stars. II. The Detection of Radial Velocity Variations in M Giant Stars HD 36384, HD 52030, and HD 208742

    Science.gov (United States)

    Lee, Byeong-Cheol; Jeong, Gwanghui; Park, Myeong-Gu; Han, Inwoo; Mkrtichian, David E.; Hatzes, Artie P.; Gu, Shenghong; Bai, Jinming; Lee, Sang-Min; Oh, Hyeong-Il; Kim, Kang-Min

    2017-07-01

    We present the detection of long-period RV variations in HD 36384, HD 52030, and HD 208742 by using the high-resolution, fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) for the precise radial velocity (RV) survey of about 200 northern circumpolar stars. Analyses of RV data, chromospheric activity indicators, and bisector variations spanning about five years suggest that the RV variations are compatible with planet or brown dwarf companions in Keplerian motion. However, HD 36384 shows photometric variations with a period very close to that of RV variations as well as amplitude variations in the weighted wavelet Z-transform (WWZ) analysis, which argues that the RV variations in HD 36384 are from the stellar pulsations. Assuming that the companion hypothesis is correct, HD 52030 hosts a companion with minimum mass 13.3 M Jup orbiting in 484 days at a distance of 1.2 au. HD 208742 hosts a companion of 14.0 M Jup at 1.5 au with a period of 602 days. All stars are located at the asymptotic giant branch (AGB) stage on the H-R diagram after undergoing the helium flash and leaving the giant clump.With stellar radii of 53.0 R ⊙ and 57.2 R ⊙ for HD 52030 and HD 208742, respectively, these stars may be the largest yet, in terms of stellar radius, found to host substellar companions. However, given possible RV amplitude variations and the fact that these are highly evolved stars, the planet hypothesis is not yet certain.

  6. On the Radial Velocity Detection of Additional Planets in Transiting, Slowly Rotating M-dwarf Systems: The Case of GJ 1132

    Science.gov (United States)

    Cloutier, Ryan; Doyon, René; Menou, Kristen; Delfosse, Xavier; Dumusque, Xavier; Artigau, Étienne

    2017-01-01

    M-dwarfs are known to commonly host high-multiplicity planetary systems. Therefore, M-dwarf planetary systems with a known transiting planet are expected to contain additional small planets (rp ≤ 4 R⊕, mp ≲ 20 M⊕) that are not seen in transit. In this study, we investigate the effort required to detect such planets using precision velocimetry around the sizable subset of M-dwarfs that are slowly rotating (Prot ≳ 40 days), and hence more likely to be inactive. We focus on the test case of GJ 1132. Specifically, we perform a suite of Monte-Carlo simulations of the star’s radial velocity signal, featuring astrophysical contributions from stellar jitter due to rotationally modulated active regions, as well as Keplerian signals from the known transiting planet and hypothetical additional planets not seen in transit. We then compute the detection completeness of non-transiting planets around GJ 1132 and consequently estimate the number of RV measurements required to detect those planets. We show that, with 1 m s‑1 precision per measurement, only ∼50 measurements are required to achieve a 50% detection completeness for all non-transiting planets in the system, as well as planets that are potentially habitable. Throughout this work, we advocate the use of Gaussian process regression as an effective tool for mitigating the effects of stellar jitter including stars with high activity. Given that GJ 1132 is representative of a large population of slowly rotating M-dwarfs, we conclude with a discussion of how our results may be extended to other systems with known transiting planets, such as those that will be discovered with TESS.

  7. Augmenting WFIRST Microlensing with a Ground-Based Telescope Network

    Science.gov (United States)

    Zhu, Wei; Gould, Andrew

    2016-06-01

    Augmenting the Wide Field Infrared Survey Telescope (WFIRST) microlensing campaigns with intensive observations from a ground-based network of wide-field survey telescopes would have several major advantages. First, it would enable full two-dimensional (2-D) vector microlens parallax measurements for a substantial fraction of low-mass lenses as well as planetary and binary events that show caustic crossing features. For a significant fraction of the free-floating planet (FFP) events and all caustic-crossing planetary/binary events, these 2-D parallax measurements directly lead to complete solutions (mass, distance, transverse velocity) of the lens object (or lens system). For even more events, the complementary ground-based observations will yield 1-D parallax measurements. Together with the 1-D parallaxes from WFIRST alone, they can probe the entire mass range M > M_Earth. For luminous lenses, such 1-D parallax measurements can be promoted to complete solutions (mass, distance, transverse velocity) by high-resolution imaging. This would provide crucial information not only about the hosts of planets and other lenses, but also enable a much more precise Galactic model. Other benefits of such a survey include improved understanding of binaries (particularly with low mass primaries), and sensitivity to distant ice-giant and gas-giant companions of WFIRST lenses that cannot be detected by WFIRST itself due to its restricted observing windows. Existing ground-based microlensing surveys can be employed if WFIRST is pointed at lower-extinction fields than is currently envisaged. This would come at some cost to the event rate. Therefore the benefits of improved characterization of lenses must be weighed against these costs.

  8. Fresnel zones for ground-based antennas

    DEFF Research Database (Denmark)

    Andersen, J. Bach

    1964-01-01

    The ordinary Fresnel zone concept is modified to include the influence of finite ground conductivity. This is important for ground-based antennas because the influence on the radiation pattern of irregularities near the antenna is determined by the amplitude and phase of the groundwave. A new...

  9. Calibration of Ground-based Lidar instrument

    DEFF Research Database (Denmark)

    Villanueva, Héctor; Gómez Arranz, Paula

    This report presents the result of the lidar calibration performed for the given Ground-based Lidar at DTU’s test site for large wind turbines at Høvsøre, Denmark. Calibration is here understood as the establishment of a relation between the reference wind speed measurements with measurement unce...

  10. Calibration of Ground -based Lidar instrument

    DEFF Research Database (Denmark)

    Villanueva, Héctor; Yordanova, Ginka

    This report presents the result of the lidar calibration performed for the given Ground-based Lidar at DTU’s test site for large wind turbines at Høvsøre, Denmark. Calibration is here understood as the establishment of a relation between the reference wind speed measurements with measurement unce...

  11. The Magellan PFS Planet Search Program: Radial Velocity and Stellar Abundance Analyses of the 360 au, Metal-poor Binary “Twins” HD 133131A & B

    Science.gov (United States)

    Teske, Johanna K.; Shectman, Stephen A.; Vogt, Steve S.; Díaz, Matías; Butler, R. Paul; Crane, Jeffrey D.; Thompson, Ian B.; Arriagada, Pamela

    2016-12-01

    We present a new precision radial velocity (RV) data set that reveals multiple planets orbiting the stars in the ˜360 au, G2+G2 “twin” binary HD 133131AB. Our six years of high-resolution echelle observations from MIKE and five years from the Planet Finder Spectrograph (PFS) on the Magellan telescopes indicate the presence of two eccentric planets around HD 133131A with minimum masses of 1.43 ± 0.03 and 0.63 ± 0.15 {{ M }}{{J}} at 1.44 ± 0.005 and 4.79 ± 0.92 au, respectively. Additional PFS observations of HD 133131B spanning five years indicate the presence of one eccentric planet of minimum mass 2.50 ± 0.05 {{ M }}{{J}} at 6.40 ± 0.59 au, making it one of the longest-period planets detected with RV to date. These planets are the first to be reported primarily based on data taken with the PFS on Magellan, demonstrating the instrument’s precision and the advantage of long-baseline RV observations. We perform a differential analysis between the Sun and each star, and between the stars themselves, to derive stellar parameters and measure a suite of 21 abundances across a wide range of condensation temperatures. The host stars are old (likely ˜9.5 Gyr) and metal-poor ([Fe/H] ˜ -0.30), and we detect a ˜0.03 dex depletion in refractory elements in HD 133131A versus B (with standard errors ˜0.017). This detection and analysis adds to a small but growing sample of binary “twin” exoplanet host stars with precise abundances measured, and represents the most metal-poor and likely oldest in that sample. Overall, the planets around HD 133131A and B fall in an unexpected regime in planet mass-host star metallicity space and will serve as an important benchmark for the study of long-period giant planets. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  12. KELT-8b: A Highly Inflated Transiting Hot Jupiter and a New Technique for Extracting High-precision Radial Velocities from Noisy Spectra

    Science.gov (United States)

    Fulton, Benjamin J.; Collins, Karen A.; Gaudi, B. Scott; Stassun, Keivan G.; Pepper, Joshua; Beatty, Thomas G.; Siverd, Robert J.; Penev, Kaloyan; Howard, Andrew W.; Baranec, Christoph; Corfini, Giorgio; Eastman, Jason D.; Gregorio, Joao; Law, Nicholas M.; Lund, Michael B.; Oberst, Thomas E.; Penny, Matthew T.; Riddle, Reed; Rodriguez, Joseph E.; Stevens, Daniel J.; Zambelli, Roberto; Ziegler, Carl; Bieryla, Allyson; D'Ago, Giuseppe; DePoy, Darren L.; Jensen, Eric L. N.; Kielkopf, John F.; Latham, David W.; Manner, Mark; Marshall, Jennifer; McLeod, Kim K.; Reed, Phillip A.

    2015-09-01

    We announce the discovery of a highly inflated transiting hot Jupiter by the KELT-North survey. A global analysis including constraints from isochrones indicates that the V = 10.8 host star (HD 343246) is a mildly evolved, G dwarf with {T}{eff}={5754}-55+54 K, {log} g={4.078}-0.054+0.049, [{Fe}/{{H}}]=0.272+/- 0.038, an inferred mass {M}*={1.211}-0.066+0.078 {M}⊙ , and radius {R}*={1.67}-0.12+0.14 {R}⊙ . The planetary companion has a mass {M}{{P}}={0.867}-0.061+0.065 MJ, radius {R}{{P}}={1.86}-0.16+0.18 RJ, surface gravity {log} {g}{{P}}={2.793}-0.075+0.072, and density {ρ }{{P}}={0.167}-0.038+0.047 g cm-3. The planet is on a roughly circular orbit with semimajor axis a={0.04571}-0.00084+0.00096 AU and eccentricity e={0.035}-0.025+0.050. The best-fit linear ephemeris is {T}0=2456883.4803+/- 0.0007 {{BJD}}{TDB} and P=3.24406+/- 0.00016 days. This planet is one of the most inflated of all known transiting exoplanets, making it one of the few members of a class of extremely low density, highly irradiated gas giants. The low stellar {log} g and large implied radius are supported by stellar density constraints from follow-up light curves, as well as an evolutionary and space motion analysis. We also develop a new technique to extract high-precision radial velocities from noisy spectra that reduces the observing time needed to confirm transiting planet candidates. This planet boasts deep transits of a bright star, a large inferred atmospheric scale height, and a high equilibrium temperature of {T}{eq}={1675}-55+61 K, assuming zero albedo and perfect heat redistribution, making it one of the best targets for future atmospheric characterization studies.

  13. A Versatile Technique to Enable Sub-milli-Kelvin Instrument Stability for Precise Radial Velocity Measurements: Tests with the Habitable-zone Planet Finder

    Science.gov (United States)

    Stefansson, Gudmundur; Hearty, Frederick; Robertson, Paul; Mahadevan, Suvrath; Anderson, Tyler; Levi, Eric; Bender, Chad; Nelson, Matthew; Monson, Andrew; Blank, Basil; Halverson, Samuel; Henderson, Chuck; Ramsey, Lawrence; Roy, Arpita; Schwab, Christian; Terrien, Ryan

    2016-12-01

    Insufficient instrument thermomechanical stability is one of the many roadblocks for achieving 10 cm s-1 Doppler radial velocity precision, the precision needed to detect Earth-twins orbiting solar-type stars. Highly temperature and pressure stabilized spectrographs allow us to better calibrate out instrumental drifts, thereby helping in distinguishing instrumental noise from astrophysical stellar signals. We present the design and performance of the Environmental Control System (ECS) for the Habitable-zone Planet Finder (HPF), a high-resolution (R = 50,000) fiber-fed near-infrared (NIR) spectrograph for the 10 {{m}} Hobby-Eberly Telescope at McDonald Observatory. HPF will operate at 180 {{K}}, driven by the choice of an H2RG NIR detector array with a 1.7 μ {{m}} cutoff. This ECS has demonstrated 0.6 {mK} rms stability over 15 days at both 180 and 300 {{K}}, and maintained high-quality vacuum (\\lt {10}-7 {Torr}) over months, during long-term stability tests conducted without a planned passive thermal enclosure surrounding the vacuum chamber. This control scheme is versatile and can be applied as a blueprint to stabilize future NIR and optical high-precision Doppler instruments over a wide temperature range from ˜77 {{K}} to elevated room temperatures. A similar ECS is being implemented to stabilize NEID, the NASA/NSF NN-EXPLORE spectrograph for the 3.5 {{m}} WIYN telescope at Kitt Peak, operating at 300 {{K}}. A [full SolidWorks 3D-CAD model] and a comprehensive parts list of the HPF ECS are included with this manuscript to facilitate the adaptation of this versatile environmental control scheme in the broader astronomical community. Certain commercial equipment, instruments, or materials are identified in this paper in order to specify the experimental procedure adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the materials or equipment

  14. Estimación de la velocidad de propagación aórtica basada en el análisis de la onda de pulso radial Velocity estimation of aortic propagation based on radial pulse wave analysis

    National Research Council Canada - National Science Library

    Fernando Clara; Gustavo Blanco; Alfredo Casarini; Pablo Corral; Gustavo Meschino; Adriana Scandurra

    2011-01-01

    Se exploró la posibilidad de utilizar la morfología del registro de onda de pulso radial obtenida mediante un transductor de movimiento para evaluar la velocidad de propagación aórtica. Se efectuó...

  15. Space and Ground-Based Infrastructures

    Science.gov (United States)

    Weems, Jon; Zell, Martin

    This chapter deals first with the main characteristics of the space environment, outside and inside a spacecraft. Then the space and space-related (ground-based) infrastructures are described. The most important infrastructure is the International Space Station, which holds many European facilities (for instance the European Columbus Laboratory). Some of them, such as the Columbus External Payload Facility, are located outside the ISS to benefit from external space conditions. There is only one other example of orbital platforms, the Russian Foton/Bion Recoverable Orbital Capsule. In contrast, non-orbital weightless research platforms, although limited in experimental time, are more numerous: sounding rockets, parabolic flight aircraft, drop towers and high-altitude balloons. In addition to these facilities, there are a number of ground-based facilities and space simulators, for both life sciences (for instance: bed rest, clinostats) and physical sciences (for instance: magnetic compensation of gravity). Hypergravity can also be provided by human and non-human centrifuges.

  16. Development of Ground-Based Plant Sentinels

    Science.gov (United States)

    2007-11-02

    plants in response to different strains of Pseudomonas syringae. Planta . 217:767-775. De Moraes CM, Schultz JC, Mescher MC, Tumlinson JH. (2004...09-30-2004 Final Technical _ April 2001 - April 2003 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Developing Plants as Ground-based Sentinels 5b. GRANT...SUPPLEMENTARY NOTES 14. ABSTRACT 9 "Z Plants emit volatile mixes characteristic of exposure to both plant and animal (insect) pathogens (bacteria and fungi). The

  17. Illumination compensation in ground based hyperspectral imaging

    Science.gov (United States)

    Wendel, Alexander; Underwood, James

    2017-07-01

    Hyperspectral imaging has emerged as an important tool for analysing vegetation data in agricultural applications. Recently, low altitude and ground based hyperspectral imaging solutions have come to the fore, providing very high resolution data for mapping and studying large areas of crops in detail. However, these platforms introduce a unique set of challenges that need to be overcome to ensure consistent, accurate and timely acquisition of data. One particular problem is dealing with changes in environmental illumination while operating with natural light under cloud cover, which can have considerable effects on spectral shape. In the past this has been commonly achieved by imaging known reference targets at the time of data acquisition, direct measurement of irradiance, or atmospheric modelling. While capturing a reference panel continuously or very frequently allows accurate compensation for illumination changes, this is often not practical with ground based platforms, and impossible in aerial applications. This paper examines the use of an autonomous unmanned ground vehicle (UGV) to gather high resolution hyperspectral imaging data of crops under natural illumination. A process of illumination compensation is performed to extract the inherent reflectance properties of the crops, despite variable illumination. This work adapts a previously developed subspace model approach to reflectance and illumination recovery. Though tested on a ground vehicle in this paper, it is applicable to low altitude unmanned aerial hyperspectral imagery also. The method uses occasional observations of reference panel training data from within the same or other datasets, which enables a practical field protocol that minimises in-field manual labour. This paper tests the new approach, comparing it against traditional methods. Several illumination compensation protocols for high volume ground based data collection are presented based on the results. The findings in this paper are

  18. Ground based spectroscopy of hot Jupiters

    Science.gov (United States)

    Waldmann, Ingo

    2010-05-01

    It has been shown in recent years with great success that spectroscopy of exoplanetary atmospheres is feasible using space based observatories such as the HST and Spitzer. However, with the end of the Spitzer cold-phase, space based observations in the near to mid infra-red are limited, which will remain true until the the onset of the JWST. The importance of developing methods of ground based spectroscopic analysis of known hot Jupiters is therefore apparent. In the past, various groups have attempted exoplanetary spectroscopy using ground based facilities and various techniques. Here I will present results using a novel spectral retrieval method for near to mid infra-red emission and transmission spectra of exoplanetary atmospheres taken from the ground and discuss the feasibility of future ground-based spectroscopy in a broader context. My recently commenced PhD project is under the supervision of Giovanna Tinetti (University College London) and in collaboration with J. P. Beaulieu (Institut d'Astrophysique de Paris), Mark Swain and Pieter Deroo (Jet Propulsion Laboratory, Caltech).

  19. WISDOM: the WIYN spectrograph for Doppler monitoring: a NASA-NSF concept for an extreme precision radial velocity instrument in support of TESS

    Science.gov (United States)

    Fżrész, Gábor; Simcoe, Robert; Barnes, Stuart I.; Buchhave, Lars A.; Egan, Mark; Foster, Rick; Hellickson, Tim; Malonis, Andrew; Phillips, David; Shectman, Stephen; Walsworth, Ronald; Winn, Josh; Woods, Deborah

    2016-08-01

    The Kepler mission highlighted that precision radial velocity (PRV) follow-up is a real bottleneck in supporting transiting exoplanet surveys. The limited availability of PRV instruments, and the desire to break the "1 m/s" precision barrier, prompted the formation of a NASA-NSF collaboration `NN-EXPLORE' to call for proposals designing a new Extreme Precision Doppler Spectrograph (EPDS). By securing a significant fraction of telescope time on the 3.5m WIYN at Kitt Peak, and aiming for unprecedented long-term precision, the EPDS instrument will provide a unique tool for U.S. astronomers in characterizing exoplanet candidates identified by TESS. One of the two funded instrument concept studies is led by the Massachusetts Institute of Technology, in consortium with Lincoln Laboratories, Harvard-Smithsonian Center for Astrophysics and the Carnegie Observatories. This paper describes the instrument concept WISDOM (WIYN Spectrograph for DOppler Monitoring) prepared by this team. WISDOM is a fiber fed, environmentally controlled, high resolution (R=110k), asymmetric white-pupil echelle spectrograph, covering a wide 380-1300nm wavelength region. Its R4 and R6 echelle gratings provide the main dispersion, symmetrically mounted on either side of a vertically aligned, vacuum-enclosed carbon fiber optical bench. Each grating feeds two cameras and thus the resulting wavelength range per camera is narrow enough that the VPHG cross-dispersers and employed anti-reflection coatings are highly efficient. The instrument operates near room temperature, and so thermal background for the near-infrared arm is mitigated by thermal blocking filters and a short (1.7μm) cutoff HgCdTe detector. To achieve high resolution while maintaining small overall instrument size (100/125mm beam diameter), imposed by the limited available space within the observatory building, we chose to slice the telescope pupil 6 ways before coupling light into fibers. An atmospheric dispersion corrector and fast

  20. Calibration of Ground-based Lidar instrument

    DEFF Research Database (Denmark)

    Yordanova, Ginka; Gómez Arranz, Paula

    This report presents the result of the lidar calibration performed for the given Ground-based Lidar at DTU’s test site for large wind turbines at Høvsøre, Denmark. Calibration is here understood as the establishment of a relation between the reference wind speed measurements with measurement...... uncertainties provided by measurement standard and corresponding lidar wind speed indications with associated measurement uncertainties. The lidar calibration concerns the 10 minute mean wind speed measurements. The comparison of the lidar measurements of the wind direction with that from wind vanes...

  1. Calibration of Ground-based Lidar instrument

    DEFF Research Database (Denmark)

    Yordanova, Ginka; Gómez Arranz, Paula

    This report presents the result of a test of a ground-based lidar of other type. The test was performed at DTU’s test site for large wind turbines at Høvsøre, Denmark. The result as an establishment of a relation between the reference wind speed measurements with measurement uncertainties provided...... by measurement standard and corresponding lidar wind speed indications with associated measurement uncertainties. The comparison of the lidar measurements of the wind direction with that from the wind vanes is also given....

  2. Calibration of Ground -based Lidar instrument

    DEFF Research Database (Denmark)

    Villanueva, Héctor; Yordanova, Ginka

    This report presents the result of the lidar calibration performed for the given Ground-based Lidar at DTU’s test site for large wind turbines at Høvsøre, Denmark. Calibration is here understood as the establishment of a relation between the reference wind speed measurements with measurement...... uncertainties provided by measurement standard and corresponding lidar wind speed indications with associated measurement uncertainties. The lidar calibration concerns the 10 minute mean wind speed measurements. The comparison of the lidar measurements of the wind direction with that from wind vanes...

  3. Calibration of Ground-based Lidar instrument

    DEFF Research Database (Denmark)

    Yordanova, Ginka; Gómez Arranz, Paula

    This report presents the result of the lidar calibration performed for the given Ground-based Lidar at DTU’s test site for large wind turbines at Høvsøre, Denmark. Calibration is here understood as the establishment of a relation between the reference wind speed measurements with measurement...... uncertainties provided by measurement standard and corresponding lidar wind speed indications with associated measurement uncertainties. The lidar calibration concerns the 10 minute mean wind speed measurements. The comparison of the lidar measurements of the wind direction with that from wind vanes...

  4. Calibration of Ground -based Lidar instrument

    DEFF Research Database (Denmark)

    Villanueva, Héctor; Georgieva Yankova, Ginka

    This report presents the result of the lidar calibration performed for the given Ground-based Lidar at DTU’s test site for large wind turbines at Høvsøre, Denmark. Calibration is here understood as the establishment of a relation between the reference wind speed measurements with measurement...... uncertainties provided by measurement standard and corresponding lidar wind speed indications with associated measurement uncertainties. The lidar calibration concerns the 10 minute mean wind speed measurements. The comparison of the lidar measurements of the wind direction with that from wind vanes...

  5. A Coordinated X-ray and Optical Campaign of the Nearest Massive Eclipsing Binary, delta Orionis Aa: III. Analysis of Optical Photometric MOST and Spectroscopic (Ground Based) Variations

    CERN Document Server

    Pablo, Herbert; Moffat, Anthony F J; Corcoran, Michael; Shenar, Tomer; Benvenuto, Omar; Fuller, Jim; Naze, Yael; Hoffman, Jennifer L; Miroshnichenko, Anatoly; Apellaniz, Jesus Maiz; Evans, Nancy; Eversberg, Thomas; Gayley, Ken; Gull, Ted; Hamaguch, Kenji; Hamann, Wolf-Rainer; Henrichs, Huib; Hole, Tabetha; Ignace, Richard; Iping, Rosina; Lauer, Jennifer; Leutenegger, Maurice; Lomax, Jamie; Nichols, Joy; Oskinova, Lida; Owocki, Stan; Pollock, Andy; Russell, Christopher M P; Waldron, Wayne; Buil, Christian; Garrel, Thierry; Graham, Keith; Heathcote, Bernard; Lemoult, Thierry; Li, Dong; Mauclaire, Benjamin; Potter, Mike; Ribeiro, Jose; Matthews, Jaymie; Cameron, Chris; Guenther, David; Kuschnig, Rainer; Rowe, Jason; Rucinski, Slavek; Sasselov, Dimitar; Weiss, Werner

    2015-01-01

    We report on both high-precision photometry from the MOST space telescope and ground-based spectroscopy of the triple system delta Ori A consisting of a binary O9.5II+early-B (Aa1 and Aa2) with P = 5.7d, and a more distant tertiary (O9 IV P > 400 yrs). This data was collected in concert with X-ray spectroscopy from the Chandra X-ray Observatory. Thanks to continuous coverage for 3 weeks, the MOST light curve reveals clear eclipses between Aa1 and Aa2 for the ?first time in non-phased data. From the spectroscopy we have a well constrained radial velocity curve of Aa1. While we are unable to recover radial velocity variations of the secondary star, we are able to constrain several fundamental parameters of this system and determine an approximate mass of the primary using apsidal motion. We also detected second order modulations at 12 separate frequencies with spacings indicative of tidally influenced oscillations. These spacings have never been seen in a massive binary, making this system one of only a handful...

  6. Study of two-phase flows in reduced gravity using ground based experiments

    Energy Technology Data Exchange (ETDEWEB)

    Vasavada, S.; Ishii, M. [Purdue University, School of Nuclear Engineering, West Lafayette, IN (United States); Sun, X. [Ohio State University, Department of Mechanical Engineering, Columbus, OH (United States); Duval, W. [NASA Glenn Research Center, Fluid Physics and Transport Branch, Cleveland, OH (United States)

    2007-07-15

    Experimental studies have been carried out to support the development of a framework of the two-fluid model along with an interfacial area transport equation applicable to reduced gravity two-phase flows. The experimental study simulates the reduced gravity condition in ground based facilities by using two immiscible liquids of similar density namely, water as the continuous phase and Therminol 59 {sup registered} as the dispersed phase. We have acquired a total of eleven data sets in the bubbly flow and bubbly to slug flow transition regimes. These flow conditions have area-averaged void (volume) fractions ranging from 3 to 30% and channel Reynolds number for the continuous phase between 2,900 and 8,800. Flow visualization has been performed and a flow regime map developed which is compared with relevant bubbly to slug flow regime transition criteria. The comparison shows that the transition boundary is well predicted by the criterion based on critical void fraction. The value of the critical void fraction at transition was experimentally determined to be approximately 25%. In addition, important two-phase flow local parameters, including the void fraction, interfacial area concentration, droplet number frequency and droplet velocity, have been acquired at two axial locations using state-of-the-art multi-sensor conductivity probe. The radial profiles and axial development of the two-phase flow parameters show that the coalescence mechanism is enhanced by either increasing the continuous or dispersed phase Reynolds number. Evidence of turbulence induced particle interaction mechanism is highlighted. The data presented in this paper clearly show the marked differences in terms of bubble (droplet) size, phase distribution and phase interaction in two-phase flow between normal and reduced gravity conditions. (orig.)

  7. Two New Long-Period Giant Planets from the McDonald Observatory Planet Search and Two Stars with Long-Period Radial Velocity Signals Related to Stellar Activity Cycles

    CERN Document Server

    Endl, Michael; Cochran, William D; MacQueen, Phillip J; Robertson, Paul; Meschiari, Stefano; Ramirez, Ivan; Shetrone, Matthew; Gullikson, Kevin; Johnson, Marshall C; Wittenmyer, Robert; Horner, Jonathan; Ciardi, David R; Horch, Elliott; Simon, Attila E; Howell, Steve B; Everett, Mark; Caldwell, Caroline; Castanheira, Barbara G

    2015-01-01

    We report the detection of two new long-period giant planets orbiting the stars HD 95872 and HD 162004 (psi1 Draconis B) by the McDonald Observatory planet search. The planet HD 95872b has a minimum mass of 4.6 M_Jup and an orbital semi-major axis of 5.2 AU. The giant planet psi1 Dra Bb has a minimum mass of 1.5 M_Jup and an orbital semi-major axis of 4.4 AU. Both of these planets qualify as Jupiter analogs. These results are based on over one and a half decades of precise radial velocity measurements collected by our program using the McDonald Observatory Tull Coude spectrograph at the 2.7 m Harlan J. Smith telescope. In the case of psi1 Draconis B we also detect a long-term non-linear trend in our data that indicates the presence of an additional giant planet, similar to the Jupiter-Saturn pair. The primary of the binary star system, psi1 Dra A, exhibits a very large amplitude radial velocity variation due to another stellar companion. We detect this additional member using speckle imaging. We also report t...

  8. Optical fiber modal noise in the 0.8 to 1.5 micron region and implications for near infrared precision radial velocity measurements

    CERN Document Server

    McCoy, Keegan; Mahadevan, Suvrath; Halverson, Samuel; Redman, Stephen L

    2012-01-01

    Modal noise in fibers has been shown to limit the signal-to-noise ratio achievable in fiber-coupled, high-resolution spectrographs if it is not mitigated via modal scrambling techniques. Modal noise become significantly more important as the wavelength increases and presents a risk to the new generation of near-infrared precision radial spectrographs under construction or being proposed to search for planets around cool M-dwarf stars, which emit most of their light in the NIR. We present experimental results of tests at Penn State University characterizing modal noise in the far visible out to 1.5 microns and the degree of modal scrambling we obtained using mechanical scramblers. These efforts are part of a risk mitigation effort for the Habitable Zone Planet Finder spectrograph currently under development at Penn State University.

  9. Detection of water absorption in the dayside atmosphere of HD 189733 b using ground-based high-resolution spectroscopy at 3.2 microns

    CERN Document Server

    Birkby, J L; Brogi, M; de Mooij, E J W; Schwarz, H; Albrecht, S; Snellen, I A G

    2013-01-01

    We report a 5 sigma detection of water absorption features in the dayside spectrum of the hot Jupiter HD 189733 b. We used high-resolution (R~100,000) spectra taken at 3.2 microns with CRIRES on the VLT to trace the radial velocity shift of the water features in the planet's dayside atmosphere during 5 hours of its 2.2 day orbit as it approached secondary eclipse. Despite considerable telluric contamination in this wavelength regime, we detect the signal within our uncertainties at the expected combination of systemic velocity (Vsys=-3 +5-6 km/s) and planet orbital velocity (Kp=154 +14-10 km/s), and determine a H2O line contrast ratio of (1.3+/-0.2)x10^-3 with respect to the stellar continuum. We find no evidence of significant absorption or emission from other carbon-bearing molecules, such as methane, although we do note a marginal increase in the significance of our detection with the inclusion of carbon dioxide in our template spectrum. This result demonstrates that ground-based, high-resolution spectrosc...

  10. A globular cluster toward M87 with a radial velocity < – 1000 km s{sup –1}: the first hypervelocity cluster

    Energy Technology Data Exchange (ETDEWEB)

    Caldwell, Nelson [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Strader, Jay [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Romanowsky, Aaron J. [Department of Physics and Astronomy, San José State University, San Jose, CA 95192 (United States); Brodie, Jean P. [University of California Observatories, Santa Cruz, CA 95064 (United States); Moore, Ben; Diemand, Jurg [Institute for Theoretical Physics, University of Zurich, CH-8057 Zurich (Switzerland); Martizzi, Davide, E-mail: caldwell@cfa.harvard.edu [Department of Astronomy, University of California, Berkeley, CA 94720 (United States)

    2014-05-20

    We report the discovery of an object near M87 in the Virgo Cluster with an extraordinary blueshift of –1025 km s{sup –1}, offset from the systemic velocity by >2300 km s{sup –1}. Evaluation of photometric and spectroscopic data provides strong evidence that this object is a distant massive globular cluster, which we call HVGC-1 in analogy to Galactic hypervelocity stars. We consider but disfavor more exotic interpretations, such as a system of stars bound to a recoiling black hole. The odds of observing an outlier as extreme as HVGC-1 in a virialized distribution of intracluster objects are small; it appears more likely that the cluster was (or is being) ejected from Virgo following a three-body interaction. The nature of the interaction is unclear, and could involve either a subhalo or a binary supermassive black hole at the center of M87.

  11. Ground-based observations of Kepler asteroseismic targets

    DEFF Research Database (Denmark)

    Uyttterhoeven , K.; Karoff, Christoffer

    2010-01-01

    We present the ground-based activities within the different working groups of the Kepler Asteroseismic Science Consortium (KASC). The activities aim at the systematic characterization of the 5000+ KASC targets, and at the collection of ground-based follow-up time-series data of selected promising...

  12. Movable Ground Based Recovery System for Reuseable Space Flight Hardware

    Science.gov (United States)

    Sarver, George L. (Inventor)

    2013-01-01

    A reusable space flight launch system is configured to eliminate complex descent and landing systems from the space flight hardware and move them to maneuverable ground based systems. Precision landing of the reusable space flight hardware is enabled using a simple, light weight aerodynamic device on board the flight hardware such as a parachute, and one or more translating ground based vehicles such as a hovercraft that include active speed, orientation and directional control. The ground based vehicle maneuvers itself into position beneath the descending flight hardware, matching its speed and direction and captures the flight hardware. The ground based vehicle will contain propulsion, command and GN&C functionality as well as space flight hardware landing cushioning and retaining hardware. The ground based vehicle propulsion system enables longitudinal and transverse maneuverability independent of its physical heading.

  13. Integrated interpretation of helicopter and ground-based geophysical data recorded within the Okavango Delta, Botswana

    DEFF Research Database (Denmark)

    Podgorski, Joel E.; Green, Alan G.; Kalscheuer, Thomas

    2015-01-01

    ) data recorded across most of the delta, (ii) 2D models and images derived from ground-based electrical resistance tomographic, transient electromagnetic, and high resolution seismic reflection/refraction tomographic data acquired at four selected sites in western and north-central regions of the delta...... resistivities and very low to low P-wave velocities. Except for images of several buried abandoned river channels, it is non-reflective. The laterally extensive underlying unit of low resistivities, low P-wave velocity, and subhorizontal reflectors very likely contains saline-water-saturated sands and clays...... reflectivity. The interface between the POM unit and basement is a prominent seismic reflector....

  14. Determinação da velocidade de condução nervosa motora dos nervos radial e ulnar de cães clinicamente sadios Determination of the motor nerve conduction velocity of the radial and ulnar nerves in clinically normal dogs

    Directory of Open Access Journals (Sweden)

    M.M. Feitosa

    2000-06-01

    Full Text Available O presente trabalho teve como objetivo a padronização dos valores de referência de velocidade de condução nervosa motora dos nervos radial e ulnar em cães clinicamente sadios. Para tanto, foram utilizados 30 cães, 11 machos e 19 fêmeas, sem raça definida, com idade entre dois e seis anos. Os valores médios das medidas do potencial muscular produzidos por meio de estimulação proximal e distal do nervo radial foram, respectivamente: latência inicial, 2,46+0,72ms e 1,58+0,62ms, amplitude de pico a pico, 8,79+2,26mV e 9,52+2,42mV e duração, 2,85+0,76ms e 2,71+0,75ms. Os respectivos valores do nervo ulnar foram: latência inicial, 4,17+0,53ms e 2,67+0,38ms; amplitude de pico a pico, 10,72+2,60mV e 11,72+2,81mV e duração, 2,23+0,38ms e 2,04+0,35ms. Os valores médios das medidas de velocidade de condução nervosa motora dos nervos radial e ulnar foram, respectivamente, 66,18+7,26m/s e 60,50+7,86m/s.The radial and ulnar nerves were examined electrophysiologically in 30 normal mongrel dogs, 11 males and 19 females, aged between two and six years. The proximal and distal evoked muscle potentials of motor stimulation of the radial nerve had an average latency of 2.46+0.72ms and 1.58+0.62ms, an average amplitude of 8.79+2.26mV and 9.52+2.42mV, and an average duration of 2.85+0.76ms and 2.71+0.75ms, respectively. The proximal and distal evoked muscle potentials of motor stimulation of the ulnar nerve had an average latency of 4.17+0.53ms and 2.67+0.38ms, an average amplitude of 10.72+2.60mV and 11.72+2.81mV, and an average duration of 2.23+0.38ms and 2.04+0.35ms, respectively. The average motor conduction velocity was 66.18+7.26m/s for the radial nerve and 60.50+7.86m/s for the ulnar nerve.

  15. The impact of T-TREC-retrieved wind and radial velocity data assimilation using EnKF and effects of assimilation window on the analysis and prediction of Typhoon Jangmi (2008)

    Science.gov (United States)

    Wang, Mingjun; Xue, Ming; Zhao, Kun

    2016-01-01

    This study examines the relative impact of assimilating T-TREC-retrieved winds (VTREC) versus radial velocity (Vr) on the analysis and forecast of Typhoon Jangmi (2008) using an ensemble Kalman filter (EnKF). The VTREC and Vr data at 30 min intervals are assimilated into the ARPS model at 3 km grid spacing over four different assimilation windows that cover, respectively, 0000-0200, 0200-0400, 0400-0600, and 0000-0600 UTC, 28 September 2008. The assimilation of VTREC data produces better analyses of the typhoon structure and intensity than the assimilation of Vr data during the earlier assimilation windows, but during the later assimilation windows when the coverage of Vr data on the typhoon from four Doppler radars is much improved, the assimilation of Vr outperforms VTREC data. The combination of VTREC and Vr data, either by assimilating both VTREC and Vr data in all cycles or by assimilating VTREC in the first cycle and Vr in the remaining cycles (labeled VTFVR), further improves the analyses of the typhoon structure and intensity compared to assimilating VTREC or Vr data alone. Quantitative verifications of 24 h forecasts of the typhoon show that the VTFVR assimilation experiments produces forecasts that best match the best track data and also have the highest precipitation prediction skills. The track forecast errors in experiment that assimilate VTREC data through the later cycles are the largest. The behaviors are discussed based on the coverage, information content, and accuracy of the various forms of data.

  16. A radial velocity survey for post-common-envelope Wolf-Rayet central stars of planetary nebulae: First results and discovery of the close binary nucleus of NGC 5189

    CERN Document Server

    Manick, Rajeev; McBride, Vanessa

    2015-01-01

    The formation of Wolf-Rayet central stars of planetary nebulae ([WR] CSPNe) whose spectroscopic appearance mimics massive WR stars remains poorly understood. Least understood is the nature and frequency of binary companions to [WR] CSPNe that may explain their H-deficiency. We have conducted a systematic radial velocity (RV) study of 6 [WR] CSPNe to search for post-common-envelope (post-CE) [WR] binaries. We used a cross-correlation method to construct the RV time-series as successfully done for massive close binary WR stars. No significant RV variability was detected for the late-[WC] type nuclei of Hen 2-113, Hen 3-1333, PMR~2 and Hen 2-99. Significant, large-amplitude variability was found in the [WC4] nucleus of NGC 5315. In the [WO1] nucleus of NGC 5189 we discovered significant periodic variability that reveals a close binary with $P_\\mathrm{orb}=4.04\\pm0.1$ d. We measured a semi-amplitude of $62.3\\pm1.3$ km s$^{-1}$ that gives a companion mass of $m_2\\ge0.5$ $M_\\odot$ or $m_2=0.84$ $M_\\odot$ (assuming ...

  17. A Ground-based Measurement of the Relativistic Beaming Effect in a Detached Double White Dwarf Binary

    Science.gov (United States)

    Shporer, Avi; Kaplan, David L.; Steinfadt, Justin D. R.; Bildsten, Lars; Howell, Steve B.; Mazeh, Tsevi

    2010-12-01

    We report on the first ground-based measurement of the relativistic beaming effect (aka Doppler boosting). We observed the beaming effect in the detached, non-interacting eclipsing double white dwarf (WD) binary NLTT 11748. Our observations were motivated by the system's high mass-ratio and low-luminosity ratio, leading to a large beaming-induced variability amplitude at the orbital period of 5.6 hr. We observed the system during three nights at the 2.0 m Faulkes Telescope North with the SDSS-g' filter and fitted the data simultaneously for the beaming, ellipsoidal, and reflection effects. Our fitted relative beaming amplitude is (3.0 ± 0.4) × 10-3, consistent with the expected amplitude from a blackbody spectrum given the photometric primary radial velocity (RV) amplitude and effective temperature. This result is a first step in testing the relation between the photometric beaming amplitude and the spectroscopic RV amplitude in NLTT 11748 and similar systems. We did not identify any variability due to the ellipsoidal or reflection effects, consistent with their expected undetectable amplitude for this system. Low-mass, helium-core WDs are expected to reside in binary systems, where in some of those systems the binary companion is a faint C/O WD and the two stars are detached and non-interacting, as in the case of NLTT 11748. The beaming effect can be used to search for the faint binary companion in those systems using wide-band photometry.

  18. Precision Radial Velocities for the Kepler Era

    Directory of Open Access Journals (Sweden)

    A. H. Szentgyorgyi

    2007-01-01

    Full Text Available La misi n Kepler realizar la fotometr a de 100,000 enanas hasta la magnitud 14 en b squeda de exoplanetas del tama o terrestre en un campo del norte de 107 grados cuadrados. Esta b squeda requiere de fotometr a masiva y reconocimiento espectrosc pico para poder as identificar las enanas de entre un millon de estrellas en el campo y post facto poder desenmascarar a las binarias impostoras que asemejan a los tr nsitos de exoplanetas del tama o terrestre. En este art culo discutimos diversos instrumentos nuevos que ha puesto en operaci n o est construyendo el Smithsonian Astrophysical Observatory (SAO y que son piedras angulares en esta b squeda espectrosc pica: el Hectochelle y el TRES

  19. Ground-Based Gas-Liquid Flow Research in Microgravity Conditions: State of Knowledge

    Science.gov (United States)

    McQuillen, J.; Colin, C.; Fabre, J.

    1999-01-01

    During the last decade, ground-based microgravity facilities have been utilized in order to obtain predictions for spacecraft system designers and further the fundamental understanding of two-phase flow. Although flow regime, pressure drop and heat transfer coefficient data has been obtained for straight tubes and a limited number of fittings, measurements of the void fraction, film thickness, wall shear stress, local velocity and void information are also required in order to develop general mechanistic models that can be utilized to ascertain the effects of fluid properties, tube geometry and acceleration levels. A review of this research is presented and includes both empirical data and mechanistic models of the flow behavior.

  20. Weighing Rocky Exoplanets with Improved Radial Velocimetry

    Science.gov (United States)

    Xuesong Wang, Sharon; Wright, Jason; California Planet Survey Consortium

    2016-01-01

    The synergy between Kepler and the ground-based radial velocity (RV) surveys have made numerous discoveries of small and rocky exoplanets, opening the age of Earth analogs. However, most (29/33) of the RV-detected exoplanets that are smaller than 3 Earth radii do not have their masses constrained to better than 20% - limited by the current RV precision (1-2 m/s). Our work improves the RV precision of the Keck telescope, which is responsible for most of the mass measurements for small Kepler exoplanets. We have discovered and verified, for the first time, two of the dominant terms in Keck's RV systematic error budget: modeling errors (mostly in deconvolution) and telluric contamination. These two terms contribute 1 m/s and 0.6 m/s, respectively, to the RV error budget (RMS in quadrature), and they create spurious signals at periods of one sidereal year and its harmonics with amplitudes of 0.2-1 m/s. Left untreated, these errors can mimic the signals of Earth-like or Super-Earth planets in the Habitable Zone. Removing these errors will bring better precision to ten-year worth of Keck data and better constraints on the masses and compositions of small Kepler planets. As more precise RV instruments coming online, we need advanced data analysis tools to overcome issues like these in order to detect the Earth twin (RV amplitude 8 cm/s). We are developing a new, open-source RV data analysis tool in Python, which uses Bayesian MCMC and Gaussian processes, to fully exploit the hardware improvements brought by new instruments like MINERVA and NASA's WIYN/EPDS.

  1. Observing the planet formation time-scale by ground-based direct imaging of planetary companions to young nearby stars Gemini\\/Hokupa'a image of TWA-5

    CERN Document Server

    Neuhäuser, R; Brandner, W; Neuhaeuser, Ralph; Potter, Dan; Brandner, Wolfgang

    2001-01-01

    Many extra-solar planets and a few planetary systems have been found indirectly by small periodic radial velocity variations around old nearby stars. The orbital characteristics of most of them are different from the planets in our solar system. Hence, planet formation theories have to be revised. Therefore, observational constraints regarding young planets would be very valuable. We have started a ground-based direct imaging search for giant planets in orbit around young nearby stars. Here, we will motivate the sample selection and will present our direct imaging observation of the very low-mass (15 to 40 Jupiter masses) brown dwarf companion TWA-5 B in orbit around the nearby young star TWA-5 A, recently obtained with the 36-element curvature-sensing AO instrument Hokupa'a of the University of Hawai'i at the 8.3m Gemini-North telescope on Mauna Kea. We could achieve a FWHM of 64 mas and 25 % Strehl. We find significance evidence for orbital motion of B around A.

  2. GLAST and Ground-Based Gamma-Ray Astronomy

    Science.gov (United States)

    McEnery, Julie

    2008-01-01

    The launch of the Gamma-ray Large Area Space Telescope together with the advent of a new generation of ground-based gamma-ray detectors such as VERITAS, HESS, MAGIC and CANGAROO, will usher in a new era of high-energy gamma-ray astrophysics. GLAST and the ground based gamma-ray observatories will provide highly complementary capabilities for spectral, temporal and spatial studies of high energy gamma-ray sources. Joint observations will cover a huge energy range, from 20 MeV to over 20 TeV. The LAT will survey the entire sky every three hours, allowing it both to perform uniform, long-term monitoring of variable sources and to detect flaring sources promptly. Both functions complement the high-sensitivity pointed observations provided by ground-based detectors. Finally, the large field of view of GLAST will allow a study of gamma-ray emission on large angular scales and identify interesting regions of the sky for deeper studies at higher energies. In this poster, we will discuss the science returns that might result from joint GLAST/ground-based gamma-ray observations and illustrate them with detailed source simulations.

  3. GLAST and Ground-Based Gamma-Ray Astronomy

    Science.gov (United States)

    McEnery, Julie

    2008-01-01

    The launch of the Gamma-ray Large Area Space Telescope together with the advent of a new generation of ground-based gamma-ray detectors such as VERITAS, HESS, MAGIC and CANGAROO, will usher in a new era of high-energy gamma-ray astrophysics. GLAST and the ground based gamma-ray observatories will provide highly complementary capabilities for spectral, temporal and spatial studies of high energy gamma-ray sources. Joint observations will cover a huge energy range, from 20 MeV to over 20 TeV. The LAT will survey the entire sky every three hours, allowing it both to perform uniform, long-term monitoring of variable sources and to detect flaring sources promptly. Both functions complement the high-sensitivity pointed observations provided by ground-based detectors. Finally, the large field of view of GLAST will allow a study of gamma-ray emission on large angular scales and identify interesting regions of the sky for deeper studies at higher energies. In this poster, we will discuss the science returns that might result from joint GLAST/ground-based gamma-ray observations and illustrate them with detailed source simulations.

  4. Ground-based observations of Kepler asteroseismic targets

    CERN Document Server

    Uytterhoeven, K; Southworth, J; Randall, S; Ostensen, R; Molenda-Zakowicz, J; Marconi, M; Kurtz, D W; Kiss, L; Gutierrez-Soto, J; Frandsen, S; De Cat, P; Bruntt, H; Briquet, M; Zhang, X B; Telting, J H; Steslicki, M; Ripepi, V; Pigulski, A; Paparo, M; Oreiro, R; Choong, Ngeow Chow; Niemczura, E; Nemec, J; Narwid, A; Mathias, P; Martin-Ruiz, S; Lehman, H; Kopacki, G; Karoff, C; Jackiewicz, J; Henden, A A; Handler, G; Grigachene, A; Green, E M; Garrido, R; Machado, L Fox; Debosscher, J; Creevey, O L; Catanzaro, G; Bognar, Z; Biazzo, K; Bernabei, S

    2010-01-01

    We present the ground-based activities within the different working groups of the Kepler Asteroseismic Science Consortium (KASC). The activities aim at the systematic characterization of the 5000+ KASC targets, and at the collection of ground-based follow-up time-series data of selected promising Kepler pulsators. So far, 35 different instruments at 30 telescopes on 22 different observatories in 12 countries are in use, and a total of more than 530 observing nights has been awarded. (Based on observations made with the Isaac Newton Telescope, William Herschel Telescope, Nordic Optical Telescope, Telescopio Nazionale Galileo, Mercator Telescope (La Palma, Spain), and IAC-80 (Tenerife, Spain). Also based on observations taken at the observatories of Sierra Nevada, San Pedro Martir, Vienna, Xinglong, Apache Point, Lulin, Tautenburg, Loiano, Serra la Nave, Asiago, McDonald, Skinakas, Pic du Midi, Mauna Kea, Steward Observatory, Bialkow Observatory of the Wroclaw University, Piszkesteto Mountain Station, Observato...

  5. Ground-based Nuclear Detonation Detection (GNDD) Technology Roadmap

    Energy Technology Data Exchange (ETDEWEB)

    Casey, Leslie A.

    2014-01-13

    This GNDD Technology Roadmap is intended to provide guidance to potential researchers and help management define research priorities to achieve technology advancements for ground-based nuclear explosion monitoring science being pursued by the Ground-based Nuclear Detonation Detection (GNDD) Team within the Office of Nuclear Detonation Detection in the National Nuclear Security Administration (NNSA) of the U.S. Department of Energy (DOE). Four science-based elements were selected to encompass the entire scope of nuclear monitoring research and development (R&D) necessary to facilitate breakthrough scientific results, as well as deliver impactful products. Promising future R&D is delineated including dual use associated with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Important research themes as well as associated metrics are identified along with a progression of accomplishments, represented by a selected bibliography, that are precursors to major improvements to nuclear explosion monitoring.

  6. Ground-Based Calibration Of A Microwave Landing System

    Science.gov (United States)

    Kiriazes, John J.; Scott, Marshall M., Jr.; Willis, Alfred D.; Erdogan, Temel; Reyes, Rolando

    1996-01-01

    System of microwave instrumentation and data-processing equipment developed to enable ground-based calibration of microwave scanning-beam landing system (MSBLS) at distances of about 500 to 1,000 ft from MSBLS transmitting antenna. Ensures accuracy of MSBLS near touchdown point, without having to resort to expense and complex logistics of aircraft-based testing. Modified versions prove useful in calibrating aircraft instrument landing systems.

  7. Ground-Based Lidar for Atmospheric Boundary Layer Ozone Measurements

    Science.gov (United States)

    Kuang, Shi; Newchurch, Michael J.; Burris, John; Liu, Xiong

    2013-01-01

    Ground-based lidars are suitable for long-term ozone monitoring as a complement to satellite and ozonesonde measurements. However, current ground-based lidars are unable to consistently measure ozone below 500 m above ground level (AGL) due to both engineering issues and high retrieval sensitivity to various measurement errors. In this paper, we present our instrument design, retrieval techniques, and preliminary results that focus on the high-temporal profiling of ozone within the atmospheric boundary layer (ABL) achieved by the addition of an inexpensive and compact mini-receiver to the previous system. For the first time, to the best of our knowledge, the lowest, consistently achievable observation height has been extended down to 125 m AGL for a ground-based ozone lidar system. Both the analysis and preliminary measurements demonstrate that this lidar measures ozone with a precision generally better than 10% at a temporal resolution of 10 min and a vertical resolution from 150 m at the bottom of the ABL to 550 m at the top. A measurement example from summertime shows that inhomogeneous ozone aloft was affected by both surface emissions and the evolution of ABL structures.

  8. Ground-based lidar for atmospheric boundary layer ozone measurements.

    Science.gov (United States)

    Kuang, Shi; Newchurch, Michael J; Burris, John; Liu, Xiong

    2013-05-20

    Ground-based lidars are suitable for long-term ozone monitoring as a complement to satellite and ozonesonde measurements. However, current ground-based lidars are unable to consistently measure ozone below 500 m above ground level (AGL) due to both engineering issues and high retrieval sensitivity to various measurement errors. In this paper, we present our instrument design, retrieval techniques, and preliminary results that focus on the high-temporal profiling of ozone within the atmospheric boundary layer (ABL) achieved by the addition of an inexpensive and compact mini-receiver to the previous system. For the first time, to the best of our knowledge, the lowest, consistently achievable observation height has been extended down to 125 m AGL for a ground-based ozone lidar system. Both the analysis and preliminary measurements demonstrate that this lidar measures ozone with a precision generally better than ±10% at a temporal resolution of 10 min and a vertical resolution from 150 m at the bottom of the ABL to 550 m at the top. A measurement example from summertime shows that inhomogeneous ozone aloft was affected by both surface emissions and the evolution of ABL structures.

  9. Pc5 Oscillation Analysis by the Satellite and Ground-Based Data

    Institute of Scientific and Technical Information of China (English)

    A. Potapov; T. Polyushkina; T. L. Zhang; H. Zhao; A. Guglielmi; J. Kultima

    2005-01-01

    Large amplitude Pc5 event was observed in the space and on ground on August 3, 2001, about three hours after contact of the strong discontinuity in the solar wind with the magnetosphere according to data from ACE and Wind satellites. The Pc5 amplitude was as high as 15 nT in the tail of magnetosphere and about 5 nT at the ground based stations. In the magnetosphere Pc5 waves were observed by Cluster and Polar satellites, which occupied positions in the morning part of the near tail at the close field lines but were parted by distance of 11.5 Re, mainly along the x-axis of the GSM coordinate system. Both compressional and transverse components of the Pc5 wave activity were observed in the space, with the transverse component having the larger amplitude. Time delay between the Cluster and Polar satellites was about 8 minutes, which could be interpreted as a wave propagation from the geomagnetic tail to the Earth with the 150km/s group velocity.The ground-based Pc5 activity was analysed by using data from the Image magnetometer network. Doubtless demonstrations of a field line resonant structure were found in variations of amplitude and polarization with latitude. Finnish chain of search coil magnetometers observed modulated Pc1 emission simultaneously with the Pc5 wave train. A possibility of non-linear impact of Pc5 wave energy on the plasma and waves in the magnetosphere is discussed.

  10. CRRES/Ground-based multi-instrument observations of an interval of substorm activity

    Directory of Open Access Journals (Sweden)

    T. K. Yeoman

    Full Text Available Observations are presented of data taken during a 3-h interval in which five clear substorm onsets/intensifications took place. During this interval ground-based data from the EISCAT incoherent scatter radar, a digital CCD all sky camera, and an extensive array of magnetometers were recorded. In addition data from the CRRES and DMSP spacecraft, whose footprints passed over Scandinavia very close to most of the ground-based instrumentation, are available. The locations and movements of the substorm current system in latitude and longitude, determined from ground and spacecraft magnetic field data, have been correlated with the locations and propagation of increased particle precipitation in the E-region at EISCAT, increased particle fluxes measured by CRRES and DMSP, with auroral luminosity and with ionospheric convection velocities. The onsets and propagation of the injection of magnetospheric particle populations and auroral luminosity have been compared. CRRES was within or very close to the substorm expansion phase onset sector during the interval. The onset region was observed at low latitudes on the ground, and has been confirmed to map back to within L=7 in the magnetotail. The active region was then observed to propagate tailward and poleward. Delays between the magnetic signature of the substorm field aligned currents and field dipolarisation have been measured. The observations support a near-Earth plasma instability mechanism for substorm expansion phase onset.

  11. Augmenting WFIRST Microlensing with a Ground-based Optical Telescope Network

    CERN Document Server

    Zhu, Wei

    2016-01-01

    Augmenting the WFIRST microlensing campaigns with intensive observations from a ground-based network of wide-field survey telescopes would have several major advantages. First, it would enable one-dimensional (1-D) microlens parallax measurements over the entire mass range $M\\gtrsim M_\\oplus$. For luminous lenses, such 1-D parallax measurements can be promoted to complete solutions (mass, distance, transverse velocity) by high-resolution imaging a few years after the observations. This would provide crucial information not only about the hosts of planets and other lenses, but also enable a much more precise Galactic model. The addition of such a ground-based survey would also yield full 2-D vector parallax measurements, with largest sensitivity to low-mass lenses, which (being non-luminous) are not subject to followup imaging. These 2-D parallax measurements will directly yield mass and distance measurements for most planetary and binary events. It would also yield additional complete solutions for single-len...

  12. Radial gas turbine design

    Energy Technology Data Exchange (ETDEWEB)

    Krausche, S.; Ohlsson, Johan

    1998-04-01

    The objective of this work was to develop a program dealing with design point calculations of radial turbine machinery, including both compressor and turbine, with as few input data as possible. Some simple stress calculations and turbine metal blade temperatures were also included. This program was then implanted in a German thermodynamics program, Gasturb, a program calculating design and off-design performance of gas turbines. The calculations proceed with a lot of assumptions, necessary to finish the task, concerning pressure losses, velocity distribution, blockage, etc., and have been correlated with empirical data from VAT. Most of these values could have been input data, but to prevent the user of the program from drowning in input values, they are set as default values in the program code. The output data consist of geometry, Mach numbers, predicted component efficiency etc., and a number of graphical plots of geometry and velocity triangles. For the cases examined, the error in predicted efficiency level was within {+-} 1-2% points, and quite satisfactory errors in geometrical and thermodynamic conditions were obtained Examination paper. 18 refs, 36 figs

  13. Coordinated studies of the geospace environment using Cluster, satellite and ground-based data: an interim review

    Directory of Open Access Journals (Sweden)

    O. Amm

    2005-09-01

    Full Text Available A little more than four years after its launch, the first magnetospheric, multi-satellite mission Cluster has already tremendously contributed to our understanding about the coupled solar wind - magnetosphere - ionosphere system. This is mostly due to its ability, for the first time, to provide instantaneous spatial views of structures in the system, to separate temporal and spatial variations, and to derive velocities and directions of moving structures. Ground-based data have an important complementary impact on Cluster-related research, as they provide a larger-scale context to put the spacecraft data in, allow to virtually enlarge the spacecrafts' field of view, and make it possible to study in detail the coupling between the magnetosphere and the ionosphere in a spatially extended domain. With this paper we present an interim review of cooperative research done with Cluster and ground-based instruments, including the support of other space-based data. We first give a short overview of the instrumentation used, and present some specific data analysis and modeling techniques that have been devised for the combined analysis of Cluster and ground-based data. Then we review highlighted results of the research using Cluster and ground-based data, ordered into dayside and nightside processes. Such highlights include, for example, the identification of the spatio-temporal signatures of the different modes of reconnection on the dayside, and the detailed analysis of the electrodynamic magnetosphere-ionosphere coupling of bursty bulk flows in the tail plasma sheet on the nightside. The aim of this paper is to provide a "sourcebook" for the Cluster and ground-based community that summarises the work that has been done in this field of research, and to identify open questions and possible directions for future studies.

    Keywords. Ionosphere (Auroral ionosphere – Magnetospheric physics (Magnetosphere-ionosphere interactions; General or

  14. Analysis of non-thermal velocities in the solar corona

    Directory of Open Access Journals (Sweden)

    L. Contesse

    2004-09-01

    Full Text Available We describe new ground-based spectroscopic observations made using a 40-cm aperture coronagraph over a whole range of radial distances (up to heights of 12' above the limb and along four different heliocentric directions N, E, S and W. The analysis is limited to the study of the brightest forbidden emission line of Fe XIV at 530.3nm, in order to reach the best possible signal-to-noise ratio. To make the results statistically more significant, the extracted parameters are averaged over the whole length of the slit, and measurements are repeated fives times at each position; the corresponding dispersions in the results obtained along the slit are given. Central line profile intensities and full line widths (FWHM are plotted and compared to measurements published by other authors closer to the limb. We found widths and turbulent (non-thermal velocities of significantly higher values above the polar regions, especially when a coronal hole is present along the line of sight. We do not see a definitely decreasing behaviour of widths and turbulent velocities in equatorial directions for larger radial distances, as reported in the literature, although lower values are measured compared to the values in polar regions. The variation in the high corona is rather flat and a correlation diagram indicates that it is different for different regions and different radial distances. This seems to be the first analysis of the profiles of this coronal line, up to large heights above the limb for both equatorial and polar regions.

  15. Concurrent aerial and ground-based optical turbulence measurements along a long elevated path

    Science.gov (United States)

    Nowlin, Scott R.; Hahn, Ila L.; Hugo, Ronald J.; Bishop, Kenneth P.

    1999-08-01

    We report concurrent ground-based scintillator/airborne constant-current anemometer (CCA) measurements made along a 51.4 km-long slant path between Salinas and North Oscura peaks, NM. Simultaneous path-averaged refractive index structure parameter (Cn2) measurements from the CCA and the scintillometer show good agreement, with deviations apparently due to localized effects of underlying topography and metrology. Statistics from both data sets are presented in the form of histograms and cumulative distribution functions. CCA Cn2 point measurements are compared to underlying surface topography. We discuss possible effects of instruments anomalies, analysis methods, and atmospheric velocity fluctuation levels. We present conclusions and made recommendations for future similar experimental efforts.

  16. Bubble motion in a rotating liquid body. [ground based tests for space shuttle experiments

    Science.gov (United States)

    Annamalai, P.; Subramanian, R. S.; Cole, R.

    1982-01-01

    The behavior of a single gas bubble inside a rotating liquid-filled sphere has been investigated analytically and experimentally as part of ground-based investigations aimed at aiding in the design and interpretation of Shuttle experiments. In the analysis, a quasi-static description of the motion of a bubble was developed in the limit of small values of the Taylor number. A series of rotation experiments using air bubbles and silicone oils were designed to match the conditions specified in the analysis, i.e., the bubble size, sphere rotation rate, and liquid kinematic viscosity were chosen such that the Taylor number was much less than unity. The analytical description predicts the bubble velocity and its asymptotic location. It is shown that the asymptotic position is removed from the axis of rotation.

  17. Intermittency of the turbulent processes in the Earth's magnetosphere detected from the ground-based measurements

    Science.gov (United States)

    Stepanova, Marina; Foppiano, Alberto; Ovalle, Elias; Antonova, Elizavieta; Troshichev, Oleg

    2008-11-01

    Turbulent processes in the Earth's magnetosphere are reflected in the dynamical behavior of the geomagnetic indices and other parameters determined from ground based observations. Intermittent properties of one minute Polar Cap (PC) index and auroral radio wave absorption are studied using 1995-2000 data sets. It was found that the probability distribution functions (PDFs) of both PC-index and absorption fluctuations display a strong non-Gaussian shape. This indicates that they are not characterized by a global time self-similarity but rather exhibit intermittency, as previously reported for solar wind velocity and auroral electrojet index values. In the case of the auroral absorption it was also found that intermittency strongly depends on the magnetic local time, being largest in the nighttime sector. This shows that the acceleration of precipitating particles is intermittent, especially near the substorm eye, where the level of turbulence increases. Application of the Local Intermittency Measure (LIM) technique confirms the aforementioned results to a better precision.

  18. Dynamical study of low Earth orbit debris collision avoidance using ground based laser

    Directory of Open Access Journals (Sweden)

    N.S. Khalifa

    2015-06-01

    Full Text Available The objective of this paper was to investigate the orbital velocity changes due to the effect of ground based laser force. The resulting perturbations of semi-major axis, miss distance and collision probability of two approaching objects are studied. The analytical model is applied for low Earth orbit debris of different eccentricities and area to mass ratio and the numerical test shows that laser of medium power ∼5 kW can perform a small change ΔV‾ of an average magnitude of 0.2 cm/s which can be accumulated over time to be about 3 cm/day. Moreover, it is confirmed that applying laser ΔV‾ results in decreasing collision probability and increasing miss distance in order to avoid collision.

  19. The STACEE-32 Ground Based Gamma-ray Detector

    CERN Document Server

    Hanna, D S; Boone, L M; Chantell, M C; Conner, Z; Covault, C E; Dragovan, M; Fortin, P; Gregorich, D T; Hinton, J A; Mukherjee, R; Ong, R A; Oser, S; Ragan, K; Scalzo, R A; Schütte, D R; Theoret, C G; Tümer, T O; Williams, D A; Zweerink, J A

    2002-01-01

    We describe the design and performance of the Solar Tower Atmospheric Cherenkov Effect Experiment detector in its initial configuration (STACEE-32). STACEE is a new ground-based gamma ray detector using the atmospheric Cherenkov technique. In STACEE, the heliostats of a solar energy research array are used to collect and focus the Cherenkov photons produced in gamma-ray induced air showers. The large Cherenkov photon collection area of STACEE results in a gamma-ray energy threshold below that of previous detectors.

  20. The STACEE Ground-Based Gamma-Ray Detector

    CERN Document Server

    Gingrich, D M; Bramel, D; Carson, J; Covault, C E; Fortin, P; Hanna, D S; Hinton, J A; Jarvis, A; Kildea, J; Lindner, T; Müller, C; Mukherjee, R; Ong, R A; Ragan, K; Scalzo, R A; Theoret, C G; Williams, D A; Zweerink, J A

    2005-01-01

    We describe the design and performance of the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) in its complete configuration. STACEE uses the heliostats of a solar energy research facility to collect and focus the Cherenkov photons produced in gamma-ray induced air showers. The light is concentrated onto an array of photomultiplier tubes located near the top of a tower. The large Cherenkov photon collection area of STACEE results in a gamma-ray energy threshold below that of previous ground-based detectors. STACEE is being used to observe pulsars, supernova remnants, active galactic nuclei, and gamma-ray bursts.

  1. Research on target accuracy for ground-based lidar

    Science.gov (United States)

    Zhu, Ling; Shi, Ruoming

    2009-05-01

    In ground based Lidar system, the targets are used in the process of registration, georeferencing for point cloud, and also can be used as check points. Generally, the accuracy of capturing the flat target center is influenced by scanning range and scanning angle. In this research, the experiments are designed to extract accuracy index of the target center with 0-90°scan angles and 100-195 meter scan ranges using a Leica HDS3000 laser scanner. The data of the experiments are listed in detail and the related results are analyzed.

  2. Overview and Initial Results from the DEEPWAVE Airborne and Ground-Based Measurement Program

    Science.gov (United States)

    Fritts, D. C.

    2015-12-01

    The deep-propagating gravity wave experiment (DEEPWAVE) was performed on and over New Zealand, the Tasman Sea, and the Southern Ocean with core airborne measurements extending from 5 June to 21 July 2014 and supporting ground-based measurements spanning a longer interval. The NSF/NCAR GV employed standard flight-level measurements and new airborne lidar and imaging measurements of gravity waves (GWs) from sources at lower altitudes throughout the stratosphere and into the mesosphere and lower thermosphere (MLT). The new GV lidars included a Rayleigh lidar measuring atmospheric density and temperature from ~20-60 km and a sodium resonance lidar measuring sodium density and temperature at ~75-105 km. An airborne Advanced Mesosphere Temperature Mapper (AMTM) and two IR "wing" cameras imaged the OH airglow temperature and/or intensity fields extending ~900 km across the GV flight track. The DLR Falcon was equipped with its standard flight-level instruments and an aerosol Doppler lidar measuring radial winds below the Falcon. DEEPWAVE also included extensive ground-based measurements in New Zealand, Tasmania, and Southern Ocean Islands. DEEPWAVE performed 26 GV flights and 13 Falcon flights, and ground-based measurements occurred whether or not the aircraft were flying. Collectively, many diverse cases of GW forcing, propagation, refraction, and dissipation spanning altitudes of 0-100 km were observed. Examples include strong mountain wave (MW) forcing and breaking in the lower and middle stratosphere, weak MW forcing yielding MW penetration into the MLT having very large amplitudes and momentum fluxes, MW scales at higher altitudes ranging from ~10-250 km, large-scale trailing waves from orography refracting into the polar vortex and extending to high altitudes, GW generation by deep convection, large-scale GWs arising from jet stream sources, and strong MWs in the MLT arising from strong surface flow over a small island. DEEPWAVE yielded a number of surprises, among

  3. Ground-based Optical Observations of Geophysical Phenomena: Aurora Borealis and Meteors

    Science.gov (United States)

    Samara, Marilia

    2010-10-01

    Advances in low-light level imaging technology have enabled significant improvements in the ground based study of geophysical phenomena. In this talk we focus on two such phenomena that occur in the Earth's ionosphere: aurorae and meteors. Imaging the aurora which is created by the interplay of the Earth's magnetosphere, ionosphere and atmosphere, provides a tool for remote sensing physical processes that are otherwise very difficult to study. By quantifying the intensities, scale sizes and lifetimes of auroral structures, we can gain significant insight into the physics behind the generation of the aurora and the interaction of the magnetosphere with the solar wind. Additionally, the combination of imaging with radars provides complimentary data and therefore more information than either method on its own. Meteor observations are a perfect example of this because the radar can accurately determine only the line-of-sight component of velocity, while imaging provides the direction of motion, the perpendicular velocity and brightness (a proxy for mass), therefore enabling a much more accurate determination of the full velocity vector and mass.

  4. Ground-Based Global Positioning System (GPS) Meteorology Integrated Precipitable Water Vapor (IPW)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ground-Based Global Positioning System (GPS) Meteorology Integrated Precipitable Water Vapor (IPW) data set measures atmospheric water vapor using ground-based...

  5. Statistical Studies of Ground-Based Optical Lightning Signatures

    Science.gov (United States)

    Hunt, C. R.; Nemzek, R. J.; Suszcynsky, D. M.

    2005-12-01

    Most extensive optical studies of lightning have been conducted from orbit, and the statistics of events collected from earth are relatively poorly documented. The time signatures of optical power measured in the presence of clouds are inevitably affected by scattering,which can distort the signatures by extending and delaying the amplitude profile in time. We have deployed two all-sky photodiode detectors, one in New Mexico and one in Oklahoma, which are gathering data alongside electric field change monitors as part of the LANL EDOTX Great Plains Array. Preliminary results show that the photodiode is sensitive to approximately 50% or more of RF events detected at ranges of up to 30 km, and still has some sensitivity at ranges in excess of 60 km (distances determined by the EDOTX field-change array). The shapes of events within this range were assessed, with focus on rise time, width, peak power, and their correlation to corresponding electric field signatures, and these are being compared with published on-orbit and ground-based data. Initial findings suggest a mean characteristic width (ratio of total detected optical energy to peak power) of 291 +/- 12 microseconds and a mean delay between the RF signal peak and optical peak of 121 +/- 17 microseconds. These values fall between prior ground-based measurements of direct return stroke emissions, and scattering-dominated on-orbit measurements. This work will promote better understanding of the correspondence between radio and optical measurements of lightning.

  6. The Radial Velocity Measurement Accuracy of Different Spectral Type Low Resolution Stellar Spectra at Different Signal-to-Noise Ratio%不同光谱型的低分辨率恒星光谱在不同信噪比条件下视向速度测量精度的分析

    Institute of Scientific and Technical Information of China (English)

    王凤飞; 罗阿理; 赵永恒

    2014-01-01

    The radial velocity of the star is very important for the study of the dynamics structure and chemistry evolution of the Milky Way ,is also an useful tool for looking for variable or special objects .In the present work ,we focus on calculating the ra-dial velocity of different spectral types of low-resolution stellar spectra by adopting a template matching method ,so as to provide effective and reliable reference to the different aspects of scientific research .We choose high signal-to-noise ratio (SNR) spectra of different spectral type stellar from the Sloan Digital Sky Survey (SDSS) ,and add different noise to simulate the stellar spectra with different SNR .Then we obtain the radial velocity measurement accuracy of different spectral type stellar spectra at different SNR by employing a template matching method .Meanwhile ,the radial velocity measurement accuracy of white dwarf stars is an-alyzed as well .We concluded that the accuracy of radial velocity measurements of early-type stars is much higher than late-type ones .For example ,the 1-sigma standard error of radial velocity measurements of A-type stars is 5~8 times as large as K-type and M-type stars .We discuss the reason and suggest that the very narrow lines of late-type stars ensure the accuracy of measure-ment of radial velocities ,while the early-type stars with very wide Balmer lines ,such as A-type stars ,become sensitive to noise and obtain low accuracy of radial velocities .For the spectra of white dwarfs stars ,the standard error of radial velocity measure-ment could be over 50 km · s-1 because of their extremely wide Balmer lines .The above conclusion will provide a good reference for stellar scientific study .%恒星的视向速度对于研究银河系的演化结构和动力学有很重要的意义,同时也是寻找变源和特殊天体的一种手段。不同的研究对其测量精度有不一样的要求。使用模板匹配的方法计算不同类型的低分辨率可见光波段恒

  7. The STACEE Ground-Based Gamma-ray Observatory

    Science.gov (United States)

    Ragan, Ken

    2002-04-01

    The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is a ground-based instrument designed to study astrophysical sources of gamma rays in the energy range from 50 to 500 GeV using an array of heliostat mirrors at the National Solar Thermal Test Facility in New Mexico. The mirrors collect Cherenkov light generated by gamma-ray air showers and concentrate it onto cameras composed of photomultiplier tubes. The STACEE instrument is now complete, and uses a total of 64 heliostats. Prototype instruments, using smaller numbers of heliostats, have previously detected gamma emission from both the Crab Nebula and the Active Galactic Nucleus Mrk421. The complete instrument has a lower threshold -- approximately 50 GeV -- than those prototypes due to superior triggering and electronics, including flash ADCs for every channel.We will discuss the performance of the complete instrument in its first full season of operation, and present preliminary results of selected observations.

  8. Atmospheric contamination for CMB ground-based observations

    CERN Document Server

    Errard, J; Akiba, Y; Arnold, K; Atlas, M; Baccigalupi, C; Barron, D; Boettger, D; Borrill, J; Chapman, S; Chinone, Y; Cukierman, A; Delabrouille, J; Dobbs, M; Ducout, A; Elleflot, T; Fabbian, G; Feng, C; Feeney, S; Gilbert, A; Goeckner-Wald, N; Halverson, N W; Hasegawa, M; Hattori, K; Hazumi, M; Hill, C; Holzapfel, W L; Hori, Y; Inoue, Y; Jaehnig, G C; Jaffe, A H; Jeong, O; Katayama, N; Kaufman, J; Keating, B; Kermish, Z; Keskitalo, R; Kisner, T; Jeune, M Le; Lee, A T; Leitch, E M; Leon, D; Linder, E; Matsuda, F; Matsumura, T; Miller, N J; Myers, M J; Navaroli, M; Nishino, H; Okamura, T; Paar, H; Peloton, J; Poletti, D; Puglisi, G; Rebeiz, G; Reichardt, C L; Richards, P L; Ross, C; Rotermund, K M; Schenck, D E; Sherwin, B D; Siritanasak, P; Smecher, G; Stebor, N; Steinbach, B; Stompor, R; Suzuki, A; Tajima, O; Takakura, S; Tikhomirov, A; Tomaru, T; Whitehorn, N; Wilson, B; Yadav, A; Zahn, O

    2015-01-01

    Atmosphere is one of the most important noise sources for ground-based Cosmic Microwave Background (CMB) experiments. By increasing optical loading on the detectors, it amplifies their effective noise, while its fluctuations introduce spatial and temporal correlations between detected signals. We present a physically motivated 3d-model of the atmosphere total intensity emission in the millimeter and sub-millimeter wavelengths. We derive an analytical estimate for the correlation between detectors time-ordered data as a function of the instrument and survey design, as well as several atmospheric parameters such as wind, relative humidity, temperature and turbulence characteristics. Using numerical computation, we examine the effect of each physical parameter on the correlations in the time series of a given experiment. We then use a parametric-likelihood approach to validate the modeling and estimate atmosphere parameters from the POLARBEAR-I project first season data set. We compare our results to previous st...

  9. Observational Selection Effects with Ground-based Gravitational Wave Detectors

    CERN Document Server

    Chen, Hsin-Yu; Vitale, Salvatore; Holz, Daniel E; Katsavounidis, Erik

    2016-01-01

    Ground-based interferometers are not perfectly all-sky instruments, and it is important to account for their behavior when considering the distribution of detected events. In particular, the LIGO detectors are most sensitive to sources above North America and the Indian Ocean and, as the Earth rotates, the sensitive regions are swept across the sky. However, because the detectors do not acquire data uniformly over time, there is a net bias on detectable sources' right ascensions. Both LIGO detectors preferentially collect data during their local night; it is more than twice as likely to be local midnight than noon when both detectors are operating. We discuss these selection effects and how they impact LIGO's observations and electromagnetic follow-up. Beyond galactic foregrounds associated with seasonal variations, we find that equatorial observatories can access over $80\\%$ of the localization probability, while mid-latitudes will access closer to $70\\%$. Facilities located near the two LIGO sites can obser...

  10. Progress in the ULTRA 1-m ground-based telescope

    Science.gov (United States)

    Romeo, Robert C.; Martin, Robert N.; Twarog, Bruce; Anthony-Twarog, Barbara; Taghavi, Ray; Hale, Rick; Etzel, Paul; Fesen, Rob; Shawl, Steve

    2006-06-01

    We present the technical status of the Ultra Lightweight Telescope for Research in Astronomy (ULTRA) program. The program is a 3-year Major Research Instrumentation (MRI) program funded by NSF. The MRI is a collaborative effort involving Composite Mirror Applications, Inc. (CMA), University of Kansas, San Diego State University and Dartmouth College. Objectives are to demonstrate the feasibility of carbon fiber reinforced plastic (CFRP) composite mirror technology for ground-based optical telescopes. CMA is spearheading the development of surface replication techniques to produce the optics, fabricating the 1m glass mandrel, and constructing the optical tube assembly (OTA). Presented will be an overview and status of the 1-m mandrel fabrication, optics development, telescope design and CFRP telescope fabrication by CMA for the ULTRA Telescope.

  11. Ground-based optical observation system for LEO objects

    Science.gov (United States)

    Yanagisawa, T.; Kurosaki, H.; Oda, H.; Tagawa, M.

    2015-08-01

    We propose a ground-based optical observation system for monitoring LEO objects, which uses numerous optical sensors to cover a vast region of the sky. Its potential in terms of detection and orbital determination were examined. About 30 cm LEO objects at 1000 km altitude are detectable using an 18 cm telescope, a CCD camera and the analysis software developed. Simulations and a test observation showed that two longitudinally separate observation sites with arrays of optical sensors can identify the same objects from numerous data sets and determine their orbits precisely. The proposed system may complement or replace the current radar observation system for monitoring LEO objects, like space-situation awareness, in the near future.

  12. Identification of rainy periods from ground based microwave radiometry

    Directory of Open Access Journals (Sweden)

    Ada Vittoria Bosisio

    2012-03-01

    Full Text Available In this paper the authors present the results of a study aiming at detecting rainy data in measurements collected by a dual band ground-based radiometer. The proposed criterion is based on the ratio of the brightness temperatures observed in the 20-30 GHz band without need of any ancillary information. A major result obtained from the probability density of the ratio computed over one month of data is the identification of threshold values between clear sky, cloudy sky and rainy sky, respectively. A linear fit performed by using radiometric data and concurrent rain gauge measurements shows a correlation coefficient equal to 0.56 between the temperature ratio and the observed precipitation.

  13. Optical vortex coronagraphs on ground-based telescopes

    CERN Document Server

    Jenkins, Charles

    2007-01-01

    The optical vortex coronagraph is potentially a remarkably effective device, at least for an ideal unobstructed telescope. Most ground-based telescopes however suffer from central obscuration and also have to operate through the aberrations of the turbulent atmosphere. This note analyzes the performance of the optical vortex in these circumstances and compares to some other designs, showing that it performs similarly in this situation. There is a large class of coronagraphs of this general type, and choosing between them in particular applications depends on details of performance at small off-axis distances and uniformity of response in the focal plane. Issues of manufacturability to the necessary tolerances are also likely to be important.

  14. Observational Selection Effects with Ground-based Gravitational Wave Detectors

    Science.gov (United States)

    Chen, Hsin-Yu; Essick, Reed; Vitale, Salvatore; Holz, Daniel; Katsavounidis, Erik

    2017-01-01

    Ground-based interferometers are not perfectly all-sky instruments, and it is important to account for their behavior when considering the distribution of detected events. In particular, the LIGO detectors are most sensitive to sources above North America and the Indian Ocean and, as the Earth rotates, the sensitive regions are swept across the sky. However, because the detectors do not acquire data uniformly over time, there is a net bias on detectable sources' right ascensions. Both LIGO detectors preferentially collect data during their local night; it is more than twice as likely to be local midnight than noon when both detectors are operating. We discuss these selection effects and how they impact LIGO's observations and electromagnetic follow-up. These effects can inform electromagnetic follow-up activities and optimization, including the possibility of directing observations even before gravitational-wave events occur.

  15. Unique cell culture systems for ground based research

    Science.gov (United States)

    Lewis, Marian L.

    1990-01-01

    The horizontally rotating fluid-filled, membrane oxygenated bioreactors developed at NASA Johnson for spacecraft applications provide a powerful tool for ground-based research. Three-dimensional aggregates formed by cells cultured on microcarrier beads are useful for study of cell-cell interactions and tissue development. By comparing electron micrographs of plant seedlings germinated during Shuttle flight 61-C and in an earth-based rotating bioreactor it is shown that some effects of microgravity are mimicked. Bioreactors used in the UAH Bioreactor Laboratory will make it possible to determine some of the effects of altered gravity at the cellular level. Bioreactors can be valuable for performing critical, preliminary-to-spaceflight experiments as well as medical investigations such as in vitro tumor cell growth and chemotherapeutic drug response; the enrichment of stem cells from bone marrow; and the effect of altered gravity on bone and muscle cell growth and function and immune response depression.

  16. Spatial-angular modeling of ground-based biaxial lidar

    Science.gov (United States)

    Agishev, Ravil R.

    1997-10-01

    Results of spatial-angular LIDAR modeling based on an efficiency criterion introduced are represented. Their analysis shows that a low spatial-angular efficiency of traditional VIS and NIR systems is a main cause of a low S/BR ratio at the photodetector input. It determines the considerable measurements errors and the following low accuracy of atmospheric optical parameters retrieval. As we have shown, the most effective protection against intensive sky background radiation for ground-based biaxial LIDAR's consist in forming of their angular field according to spatial-angular efficiency criterion G. Some effective approaches to high G-parameter value achievement to achieve the receiving system optimization are discussed.

  17. Soil moisture retrieval using ground based bistatic scatterometer data at X-band

    Science.gov (United States)

    Gupta, Dileep Kumar; Prasad, Rajendra; Kumar, Pradeep; Vishwakarma, Ajeet Kumar

    2017-02-01

    Several hydrological phenomenon and applications need high quality soil moisture information of the top Earth surface. The advent of technologies like bistatic scatterometer can retrieve soil moisture information with high accuracy and hence used in present study. The radar data is acquired by specially designed ground based bistatic scatterometer system in the specular direction of 20-70° incidence angles at steps of 5° for HH and VV polarizations. This study provides first time comprehensive evaluation of different machine learning algorithms for the retrieval of soil moisture using the X-band bistatic scatterometer measurements. The comparison of different artificial neural network (ANN) models such as back propagation artificial neural network (BPANN), radial basis function artificial neural network (RBFANN), generalized regression artificial neural network (GRANN) along with linear regression model (LRM) are used to estimate the soil moisture. The performance indices such as %Bias, Root Mean Squared Error (RMSE) and Nash-Sutcliffe Efficiency (NSE) are used to evaluate the performances of the machine learning techniques. Among different models employed in this study, the BPANN is found to have marginally higher performance in case of HH polarization while RBFANN is found suitable with VV polarization followed by GRANN and LRM. The results obtained are of considerable scientific and practical value to the wider scientific community for the number of practical applications and research studies in which radar datasets are used.

  18. Robust Image Restoration for Ground-Based Space Surveillance

    Science.gov (United States)

    2013-09-01

    the Earth’s atmosphere requires careful mitigation of the turbulence-induced aberration in the observed wave fronts. This is typically achieved...BACKGROUND As we discuss in Jefferies et al. [3], high spatial frequency aberrations of the wave-front phase become increasingly damaging to image...large values of D/r0 where chromatic radial streaking of the PSF speckles is a large part of the PSF morphology. By including temporal and spectral

  19. Dynamical interstellar medium with Gaia and ground-based massive spectroscopic stellar surveys

    CERN Document Server

    Zwitter, Tomaž

    2015-01-01

    The ongoing Gaia mission of ESA will provide accurate spatial and kinematical information for a large fraction of stars in the Galaxy. Interstellar extinction and line absorption studies toward a large number of stars at different distances and directions can give a 3-dimensional distribution map of interstellar absorbers, and thus reach a similar spatial perfection. Under certain morphologies (e.g. geometrically thin absorption curtains) one can infer a complete velocity vector from its radial velocity component and so obtain a dynamical information comparable to stars. But observations of a large number of stars at different distances are needed to determine the location of the absorption pockets. Therefore, techniques to measure interstellar absorptions towards (abundant) cool stars are needed. A complex mix of colliding absorption clouds is found in the Galactic plane. Thus, one would wish to start with deep observations to detect the weak, but simpler interstellar absorptions at high Galactic latitudes. ...

  20. Probing Pluto's Atmosphere Using Ground-Based Stellar Occultations

    Science.gov (United States)

    Sicardy, Bruno; Rio de Janeiro Occultation Team, Granada Team, International Occultation and Timing Association, Royal Astronomical Society New Zealand Occultation Section, Lucky Star associated Teams

    2016-10-01

    Over the last three decades, some twenty stellar occultations by Pluto have been monitored from Earth. They occur when the dwarf planet blocks the light from a star for a few minutes as it moves on the sky. Such events led to the hint of a Pluto's atmosphere in 1985, that was fully confirmed during another occultation in 1988, but it was only in 2002 that a new occultation could be recorded. From then on, the dwarf planet started to move in front of the galactic center, which amplified by a large factor the number of events observable per year.Pluto occultations are essentially refractive events during which the stellar rays are bent by the tenuous atmosphere, causing a gradual dimming of the star. This provides the density, pressure and temperature profiles of the atmosphere from a few kilometers above the surface up to about 250 km altitude, corresponding respectively to pressure levels of about 10 and 0.1 μbar. Moreover, the extremely fine spatial resolution (a few km) obtained through this technique allows the detection of atmospheric gravity waves, and permits in principle the detection of hazes, if present.Several aspects make Pluto stellar occultations quite special: first, they are the only way to probe Pluto's atmosphere in detail, as the dwarf planet is far too small on the sky and the atmosphere is far too tenuous to be directly imaged from Earth. Second, they are an excellent example of participative science, as many amateurs have been able to record those events worldwide with valuable scientific returns, in collaboration with professional astronomers. Third, they reveal Pluto's climatic changes on decade-scales and constrain the various seasonal models currently explored.Finally, those observations are fully complementary to space exploration, in particular with the New Horizons (NH) mission. I will show how ground-based occultations helped to better calibrate some NH profiles, and conversely, how NH results provide some key boundary conditions

  1. Independet Component Analyses of Ground-based Exoplanetary Transits

    Science.gov (United States)

    Silva Martins-Filho, Walter; Griffith, Caitlin Ann; Pearson, Kyle; Waldmann, Ingo; Biddle, Lauren; Zellem, Robert Thomas; Alvarez-Candal, Alvaro

    2016-10-01

    Most observations of exoplanetary atmospheres are conducted when a "Hot Jupiter" exoplanet transits in front of its host star. These Jovian-sized planets have small orbital periods, on the order of days, and therefore a short transit time, making them more ameanable to observations. Measurements of Hot Jupiter transits must achieve a 10-4 level of accuracy in the flux to determine the spectral modulations of the exoplanetary atmosphere. In order to accomplish this level of precision, we need to extract systematic errors, and, for ground-based measurements, the effects of Earth's atmosphere, from the signal due to the exoplanet, which is several orders of magnitudes smaller. Currently, the effects of the terrestrial atmosphere and the some of the time-dependent systematic errors are treated by dividing the host star by a reference star at each wavelength and time step of the transit. More recently, Independent Component Analyses (ICA) have been used to remove systematic effects from the raw data of space-based observations (Waldmann 2014,2012; Morello et al.,2015,2016). ICA is a statistical method born from the ideas of the blind-source separation studies, which can be used to de-trend several independent source signals of a data set (Hyvarinen and Oja, 2000). One strength of this method is that it requires no additional prior knowledge of the system. Here, we present a study of the application of ICA to ground-based transit observations of extrasolar planets, which are affected by Earth's atmosphere. We analyze photometric data of two extrasolar planets, WASP-1b and GJ3470b, recorded by the 61" Kuiper Telescope at Stewart Observatory using the Harris B and U filters. The presentation will compare the light curve depths and their dispersions as derived from the ICA analysis to those derived by analyses that ratio of the host star to nearby reference stars.References: Waldmann, I.P. 2012 ApJ, 747, 12, Waldamann, I. P. 2014 ApJ, 780, 23; Morello G. 2015 ApJ, 806

  2. Assessment of radial movement of left ventricle with velocity vector imaging in patients with dilated cardiomyopathy%速度向量成像技术评价扩张型心肌病患者径向室壁运动

    Institute of Scientific and Technical Information of China (English)

    王玮; 施仲伟; 胡厚达; 许燕; 张凤如

    2010-01-01

    Objective To assess the radial systolic function of left ventricle(LV) in patients with dilated cardiomyopathy(DCM) by velocity vector imaging(VVI).Methods Sixteen patients with DCM and twenty control subjects were detected by VVI.VVI data were collected from the six basal segments and six mid segments in parastenal LV short axis views.The radial systolic velocity(V) ,strain(ε) ,strain rate(SR),the time to peak systolic velocity(PTV) and the time to maximum strain(PTε) were measured with special software.The differene of the earliest and the latest time to peak velocity(T-max) and the standard deviation of time to peak velocity(T-SD) of 12 segments were calculated.Results Compared to the controlled group,patients with DCM had significantly lower radial V,ε and SR (P <0.01) in all the 12 segments,significantly longer PTV and PTε (P < 0.05) in most segments, and significantly larger T-max and T-SD (P <0.05).Conclusions VVI is useful to assess the abnormalities in LV radial movement in patients with DCM and could provide more information about regional cardiac function.%目的 应用速度向量成像技术(velocity vector imaging,VVI)评价扩张型心肌病(dilated cardiomyopathy,DCM)径向局部心肌收缩功能和同步性.方法 16例DCM患者和20例对照者进行超声心动图检查,脱机分析左室短轴观中6个基底节段和6个中间节段共12个节段的径向收缩期峰值速度(V)、应变(ε)、应变率(SR)、径向速度达峰时间(PTV)、应变达峰时间(PTε),计算12节段的最早与最晚速度达峰时间差值(T-max)及速度达峰时间标准差(T-SD).结果 ①DCM组各节段的V、ε、SR的平均值均显著低于对照组相应节段(P<0.01);②DCM组的PTV除乳头肌水平前间隔及后间隔外,其余节段均大于对照组(P<0.05),PTε除前间隔二尖瓣水平、乳头肌水平和后间隔二尖瓣水平、乳头肌水平外,其余节段均显著延长(P<0.05);③DCM组的T-max

  3. Transverse velocity shifts in protostellar jets: rotation or velocity asymmetries?

    CERN Document Server

    De Colle, Fabio; Riera, Angels

    2016-01-01

    Observations of several protostellar jets show systematic differences in radial velocity transverse to the jet propagation direction, which have been interpreted as evidence of rotation in the jets. In this paper we discuss the origin of these velocity shifts, and show that they could be originated by rotation in the flow, or by side to side asymmetries in the shock velocity, which could be due to asymmetries in the jet ejection velocity/density or in the ambient medium. For typical poloidal jet velocities (~ 100-200 km/s), an asymmetry >~ 10% can produce velocity shifts comparable to those observed. We also present three dimensional numerical simulations of rotating, precessing and asymmetric jets, and show that, even though for a given jet there is a clear degeneracy between these effects, a statistical analysis of jets with different inclination angles can help to distinguish between the alternative origins of transverse velocity shifts. Our analysis indicate that side to side velocities asymmetries could ...

  4. Radial interchange motions of plasma filaments

    DEFF Research Database (Denmark)

    Garcia, O.E.; Bian, N.H.; Fundamenski, W.

    2006-01-01

    reduces the radial velocity of isolated filaments. The results are discussed in the context of convective transport in scrape-off layer plasmas, comprising both blob-like structures in low confinement modes and edge localized mode filaments in unstable high confinement regimes. (c) 2006 American Institute...

  5. Observing Tsunamis in the Ionosphere Using Ground Based GPS Measurements

    Science.gov (United States)

    Galvan, D. A.; Komjathy, A.; Song, Y. Tony; Stephens, P.; Hickey, M. P.; Foster, J.

    2011-01-01

    Ground-based Global Positioning System (GPS) measurements of ionospheric Total Electron Content (TEC) show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following recent seismic events, including the Tohoku tsunami of March 11, 2011. We observe fluctuations correlated in time, space, and wave properties with this tsunami in TEC estimates processed using JPL's Global Ionospheric Mapping Software. These TEC estimates were band-pass filtered to remove ionospheric TEC variations with periods outside the typical range of internal gravity waves caused by tsunamis. Observable variations in TEC appear correlated with the Tohoku tsunami near the epicenter, at Hawaii, and near the west coast of North America. Disturbance magnitudes are 1-10% of the background TEC value. Observations near the epicenter are compared to estimates of expected tsunami-driven TEC variations produced by Embry Riddle Aeronautical University's Spectral Full Wave Model, an atmosphere-ionosphere coupling model, and found to be in good agreement. The potential exists to apply these detection techniques to real-time GPS TEC data, providing estimates of tsunami speed and amplitude that may be useful for future early warning systems.

  6. Tissue Engineering of Cartilage on Ground-Based Facilities

    Science.gov (United States)

    Aleshcheva, Ganna; Bauer, Johann; Hemmersbach, Ruth; Egli, Marcel; Wehland, Markus; Grimm, Daniela

    2016-06-01

    Investigations under simulated microgravity offer the opportunity for a better understanding of the influence of altered gravity on cells and the scaffold-free three-dimensional (3D) tissue formation. To investigate the short-term influence, human chondrocytes were cultivated for 2 h, 4 h, 16 h, and 24 h on a 2D Fast-Rotating Clinostat (FRC) in DMEM/F-12 medium supplemented with 10 % FCS. We detected holes in the vimentin network, perinuclear accumulations of vimentin after 2 h, and changes in the chondrocytes shape visualised by F-actin staining after 4 h of FRC-exposure. Scaffold-free cultivation of chondrocytes for 7 d on the Random Positioning Machine (RPM), the FRC and the Rotating Wall Vessel (RWV) resulted in spheroid formation, a phenomenon already known from spaceflight experiments with chondrocytes (MIR Space Station) and thyroid cancer cells (SimBox/Shenzhou-8 space mission). The experiments enabled by the ESA-CORA-GBF programme gave us an optimal opportunity to study gravity-related cellular processes, validate ground-based facilities for our chosen cell system, and prepare long-term experiments under real microgravity conditions in space

  7. Theoretical validation of ground-based microwave ozone observations

    Directory of Open Access Journals (Sweden)

    P. Ricaud

    Full Text Available Ground-based microwave measurements of the diurnal and seasonal variations of ozoneat 42±4.5 and 55±8 km are validated by comparing with results from a zero-dimensional photochemical model and a two-dimensional (2D chemical/radiative/dynamical model, respectively. O3 diurnal amplitudes measured in Bordeaux are shown to be in agreement with theory to within 5%. For the seasonal analysis of O3 variation, at 42±4.5 km, the 2D model underestimates the yearly averaged ozone concentration compared with the measurements. A double maximum oscillation (~3.5% is measured in Bordeaux with an extended maximum in September and a maximum in February, whilst the 2D model predicts only a single large maximum (17% in August and a pronounced minimum in January. Evidence suggests that dynamical transport causes the winter O3 maximum by propagation of planetary waves, phenomena which are not explicitly reproduced by the 2D model. At 55±8 km, the modeled yearly averaged O3 concentration is in very good agreement with the measured yearly average. A strong annual oscillation is both measured and modeled with differences in the amplitude shown to be exclusively linked to temperature fields.

  8. Models of ionospheric VLF absorption of powerful ground based transmitters

    Science.gov (United States)

    Cohen, M. B.; Lehtinen, N. G.; Inan, U. S.

    2012-12-01

    Ground based Very Low Frequency (VLF, 3-30 kHz) radio transmitters play a role in precipitation of energetic Van Allen electrons. Initial analyses of the contribution of VLF transmitters to radiation belt losses were based on early models of trans-ionospheric propagation known as the Helliwell absorption curves, but some recent studies have found that the model overestimates (by 20-100 dB) the VLF energy reaching the magnetosphere. It was subsequently suggested that conversion of wave energy into electrostatic modes may be responsible for the error. We utilize a newly available extensive record of VLF transmitter energy reaching the magnetosphere, taken from the DEMETER satellite, and perform a direct comparison with a sophisticated full wave model of trans-ionospheric propagation. Although the model does not include the effect of ionospheric irregularities, it correctly predicts the average total power injected into the magnetosphere within several dB. The results, particularly at nighttime, appear to be robust against the variability of the ionospheric electron density. We conclude that the global effect of irregularity scattering on whistler mode conversion to quasi-electrostatic may be no larger than 6 dB.

  9. Atmospheric Refraction Path Integrals in Ground-Based Interferometry

    CERN Document Server

    Mathar, R J

    2004-01-01

    The basic effect of the earth's atmospheric refraction on telescope operation is the reduction of the true zenith angle to the apparent zenith angle, associated with prismatic aberrations due to the dispersion in air. If one attempts coherent superposition of star images in ground-based interferometry, one is in addition interested in the optical path length associated with the refracted rays. In a model of a flat earth, the optical path difference between these is not concerned as the translational symmetry of the setup means no net effect remains. Here, I evaluate these interferometric integrals in the more realistic arrangement of two telescopes located on the surface of a common earth sphere and point to a star through an atmosphere which also possesses spherical symmetry. Some focus is put on working out series expansions in terms of the small ratio of the baseline over the earth radius, which allows to bypass some numerics which otherwise is challenged by strong cancellation effects in building the opti...

  10. Experiments on a Ground-Based Tomographic Synthetic Aperture Radar

    Directory of Open Access Journals (Sweden)

    Hoonyol Lee

    2016-08-01

    Full Text Available This paper presents the development and experiment of three-dimensional image formation by using a ground-based tomographic synthetic aperture radar (GB-TomoSAR system. GB-TomoSAR formulates two-dimensional synthetic aperture by the motion of antennae, both in azimuth and vertical directions. After range compression, three-dimensional image focusing is performed by applying Deramp-FFT (Fast Fourier Transform algorithms, both in azimuth and vertical directions. Geometric and radiometric calibrations were applied to make an image cube, which is then projected into range-azimuth and range-vertical cross-sections for visualization. An experiment with a C-band GB-TomoSAR system with a scan length of 2.49 m and 1.86 m in azimuth and vertical-direction, respectively, shows distinctive three-dimensional radar backscattering of stable buildings and roads with resolutions similar to the theoretical values. Unstable objects such as trees and moving cars generate severe noise due to decorrelation during the eight-hour image-acquisition time.

  11. A comparative study of satellite and ground-based phenology.

    Science.gov (United States)

    Studer, S; Stöckli, R; Appenzeller, C; Vidale, P L

    2007-05-01

    Long time series of ground-based plant phenology, as well as more than two decades of satellite-derived phenological metrics, are currently available to assess the impacts of climate variability and trends on terrestrial vegetation. Traditional plant phenology provides very accurate information on individual plant species, but with limited spatial coverage. Satellite phenology allows monitoring of terrestrial vegetation on a global scale and provides an integrative view at the landscape level. Linking the strengths of both methodologies has high potential value for climate impact studies. We compared a multispecies index from ground-observed spring phases with two types (maximum slope and threshold approach) of satellite-derived start-of-season (SOS) metrics. We focus on Switzerland from 1982 to 2001 and show that temporal and spatial variability of the multispecies index correspond well with the satellite-derived metrics. All phenological metrics correlate with temperature anomalies as expected. The slope approach proved to deviate strongly from the temporal development of the ground observations as well as from the threshold-defined SOS satellite measure. The slope spring indicator is considered to indicate a different stage in vegetation development and is therefore less suited as a SOS parameter for comparative studies in relation to ground-observed phenology. Satellite-derived metrics are, however, very susceptible to snow cover, and it is suggested that this snow cover should be better accounted for by the use of newer satellite sensors.

  12. Satellite Type Estination from Ground-based Photometric Observation

    Science.gov (United States)

    Endo, T.; Ono, H.; Suzuki, J.; Ando, T.; Takanezawa, T.

    2016-09-01

    The optical photometric observation is potentially a powerful tool for understanding of the Geostationary Earth Orbit (GEO) objects. At first, we measured in laboratory the surface reflectance of common satellite materials, for example, Multi-layer Insulation (MLI), mono-crystalline silicon cells, and Carbon Fiber Reinforced Plastic (CFRP). Next, we calculated visual magnitude of a satellite by simplified shape and albedo. In this calculation model, solar panels have dimensions of 2 by 8 meters, and the bus area is 2 meters squared with measured optical properties described above. Under these conditions, it clarified the brightness can change the range between 3 and 4 magnitudes in one night, but color index changes only from 1 to 2 magnitudes. Finally, we observed the color photometric data of several GEO satellites visible from Japan multiple times in August and September 2014. We obtained that light curves of GEO satellites recorded in the B and V bands (using Johnson filters) by a ground-base optical telescope. As a result, color index changed approximately from 0.5 to 1 magnitude in one night, and the order of magnitude was not changed in all cases. In this paper, we briefly discuss about satellite type estimation using the relation between brightness and color index obtained from the photometric observation.

  13. Ground-based measurements of UV Index (UVI at Helwan

    Directory of Open Access Journals (Sweden)

    H. Farouk

    2012-12-01

    Full Text Available On October 2010 UV Index (UVI ground-based measurements were carried out by weather station at solar laboratory in NRIAG. The daily variation has maximum values in spring and summer days, while minimum values in autumn and winter days. The low level of UVI between 2.55 and 2.825 was found in December, January and February. The moderate level of UVI between 3.075 and 5.6 was found in March, October and November. The high level of UVI between 6.7 and 7.65 was found in April, May and September. The very high level of UVI between 8 and 8.6 was found in June, July and August. High level of radiation over 6 months per year including 3 months with a very high level UVI. According to the equation {UVI=a[SZA]b} the UVI increases with decreasing SZA by 82% on a daily scale and 88% on a monthly scale. Helwan exposure to a high level of radiation over 6 months per year including 3 months with a very high level UVI, so it is advisable not to direct exposure to the sun from 11 am to 2:00 pm.

  14. Physical mechanism determining the radial electric field and its radial structure in a toroidal plasma

    Energy Technology Data Exchange (ETDEWEB)

    Ida, Katsumi; Miura, Yukitoshi; Itoh, Sanae [and others

    1994-10-01

    Radial structures of plasma rotation and radial electric field are experimentally studied in tokamak, heliotron/torsatron and stellarator devices. The perpendicular and parallel viscosities are measured. The parallel viscosity, which is dominant in determining the toroidal velocity in heliotron/torsatron and stellarator devices, is found to be neoclassical. On the other hand, the perpendicular viscosity, which is dominant in dictating the toroidal rotation in tokamaks, is anomalous. Even without external momentum input, both a plasma rotation and a radial electric field exist in tokamaks and heliotrons/torsatrons. The observed profiles of the radial electric field do not agree with the theoretical prediction based on neoclassical transport. This is mainly due to the existence of anomalous perpendicular viscosity. The shear of the radial electric field improves particle and heat transport both in bulk and edge plasma regimes of tokamaks. (author) 95 refs.

  15. Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. 8: An intensive HST, IUE, and ground-based study of NGC 5548

    Science.gov (United States)

    Korista, K.; Alloin, D.; Barr, P.; Clavel, J.; Cohen, R. D.; Crenshaw, D. M.; Evans, I. N.; Horne, K.; Koratkar, A. P.; Kriss, G. A.

    1994-01-01

    We present the data and initial results from a combined HST/IUE/ground-based spectroscopic monitoring campaign on the Seyfert 1 galaxy NGC 5548 that was undertaken in order to address questions that require both higher temporal resolution and higher signal-to-noise ratios than were obtained in our previous multiwavelength monitoring of this galaxy in 1988-89. IUE spectra were obtained once every two days for a period of 74 days beginning on 14 March 1993. During the last 39 days of this campaign, spectroscopic observations were also made with the HST Faint Object Spectrograph (FOS) on a daily basis. Ground-based observations, consisting of 165 optical spectra and 77 photometric observations (both CCD imaging and aperture photometry), are reported for the period 1992 October to 1993 September, although much of the data are concentrated around the time of the satellite-based program. These data constitute a fifth year of intensive optical monitoring of this galaxy. In this contribution, we describe the acquisition and reduction of all of the satellite and ground-based data obtained in this program. We describe in detail various photometric problems with the FOS and explain how we identified and corrected for various anomalies. During the HST portion of the monitoring campaign, the 1350 A continuum flux is found to have varied by nearly a factor of two. In other wavebands, the continuum shows nearly identical behavior, except that the amplitude of variability is larger at shorter wavelengths, and the continuum light curves appear to show more short time-scale variability at shorter wavelengths. The broad emission lines also vary in flux, with amplitudes that are slightly smaller than the UV continuum variations and with a small time delay relative to the UV continuum. On the basis of simple time-series analysis of the UV and optical continuum and emission line light curves, we find (1) that the ultraviolet and optical continuum variations are virtually simultaneous

  16. Evaluation of radial systolic function of left ventricular with myocardial infarction by velocity vector imaging%速度向量成像技术评价心肌梗死节段室壁径向收缩能力的价值

    Institute of Scientific and Technical Information of China (English)

    杨娅; 谢谨捷; 李治安; 孟圆峰; 郝晓晔; 张京岚

    2010-01-01

    目的 探讨速度向量成像(VVI)技术评价心肌梗死节段径向收缩能力的价值.方法 将雄性Wister大鼠分为两组,一组结扎冠状动脉制成心肌梗死模型组(10只),另一组同样进行手术但不结扎冠状动脉作为对照组(14只).应用VVI技术对左室短轴乳头肌水平室壁径向应变及应变率进行分析.结果 心肌梗死组梗死节段(左室前壁及前间隔)径向应变及应变率较对照组相应节段明显减低,两组间差异具有统计学意义(P0.05).结论 VVI技术能够定量评价心肌梗死节段室壁的径向收缩能力.%Objective To explore the value of velocity vector imaging(VVI)in evaluating radial systolic function of left ventricular with myocardial infarction(MI).Methods Twenty-four male Wister rats were divided into MI group(n=10)and control group(n=14).Left main coronary artery of MI group were ligated,and the similar operation were performed in control group without coronary artery ligation.VVI was used to analyse the radial strain and strain rate of regional left ventricule in rata.Results Compared with control group,the radial strain and strain rate of infarcted segments(anterior wall and anterior septal)were decreased significantly(P0.05)was found when compared radial strain and strain rate in different left ventricle segments in control group.Conclusions VVI can be used as a quantitive tool in evaluating the radial systolic function of left ventricular with MI.

  17. Observational Selection Effects with Ground-based Gravitational Wave Detectors

    Science.gov (United States)

    Chen, Hsin-Yu; Essick, Reed; Vitale, Salvatore; Holz, Daniel E.; Katsavounidis, Erik

    2017-01-01

    Ground-based interferometers are not perfect all-sky instruments, and it is important to account for their behavior when considering the distribution of detected events. In particular, the LIGO detectors are most sensitive to sources above North America and the Indian Ocean, and as the Earth rotates, the sensitive regions are swept across the sky. However, because the detectors do not acquire data uniformly over time, there is a net bias on detectable sources’ right ascensions. Both LIGO detectors preferentially collect data during their local night; it is more than twice as likely to be local midnight than noon when both detectors are operating. We discuss these selection effects and how they impact LIGO’s observations and electromagnetic (EM) follow-up. Beyond galactic foregrounds associated with seasonal variations, we find that equatorial observatories can access over 80% of the localization probability, while mid-latitudes will access closer to 70%. Facilities located near the two LIGO sites can observe sources closer to their zenith than their analogs in the south, but the average observation will still be no closer than 44° from zenith. We also find that observatories in Africa or the South Atlantic will wait systematically longer before they can begin observing compared to the rest of the world though, there is a preference for longitudes near the LIGOs. These effects, along with knowledge of the LIGO antenna pattern, can inform EM follow-up activities and optimization, including the possibility of directing observations even before gravitational-wave events occur.

  18. Ground-based Measurements of Next Generation Spectroradiometric Standard Stars

    Science.gov (United States)

    McGraw, John T.

    2013-01-01

    Accurate, radiometric standards are essential to the future of ground- and space-based astronomy and astrophysics. While astronomers tend to think of “standard stars” as available calibration sources, progress at NIST to accurately calibrate inexpensive, easy to use photodiode detectors as spectroradiometric standards from 200 nm to 1800 nm allows referencing astronomical measurements to these devices. Direction-, time-, and wavelength-dependent transmission of Earth’s atmosphere is the single largest source of error for ground-based radiometric measurement of astronomical objects. Measurements and impacts of atmospheric extinction - scattering and absorption - on imaging radiometric and spectroradiometric measurements are described. The conclusion is that accurate real-time measurement of extinction in the column of atmosphere through which standard star observations are made, over the spectral region being observed and over the field of view of the telescope are required. New techniques to directly and simultaneously measure extinction in the column of atmosphere through which observations are made are required. Our direct extinction measurement solution employs three small facility-class instruments working in parallel: a lidar to measure rapidly time variable transmission at three wavelengths with uncertainty of 0.25% per airmass, a spectrophotometer to measure rapidly wavelength variable extinction with sub-1% precision per nanometer resolution element from 350 to 1050nm, and a wide-field camera to measure angularly variable extinction over the field of view. These instruments and their operation will be described. We assert that application of atmospheric metadata provided by this instrument suite corrects for a significant fraction of systematic errors currently limiting radiometric precision, and provides a major step towards measurements that are provably dominated by random noise.

  19. Ozone profiles above Kiruna from two ground-based radiometers

    Science.gov (United States)

    Ryan, Niall J.; Walker, Kaley A.; Raffalski, Uwe; Kivi, Rigel; Gross, Jochen; Manney, Gloria L.

    2016-09-01

    This paper presents new atmospheric ozone concentration profiles retrieved from measurements made with two ground-based millimetre-wave radiometers in Kiruna, Sweden. The instruments are the Kiruna Microwave Radiometer (KIMRA) and the Millimeter wave Radiometer 2 (MIRA 2). The ozone concentration profiles are retrieved using an optimal estimation inversion technique, and they cover an altitude range of ˜ 16-54 km, with an altitude resolution of, at best, 8 km. The KIMRA and MIRA 2 measurements are compared to each other, to measurements from balloon-borne ozonesonde measurements at Sodankylä, Finland, and to measurements made by the Microwave Limb Sounder (MLS) aboard the Aura satellite. KIMRA has a correlation of 0.82, but shows a low bias, with respect to the ozonesonde data, and MIRA 2 shows a smaller magnitude low bias and a 0.98 correlation coefficient. Both radiometers are in general agreement with each other and with MLS data, showing high correlation coefficients, but there are differences between measurements that are not explained by random errors. An oscillatory bias with a peak of approximately ±1 ppmv is identified in the KIMRA ozone profiles over an altitude range of ˜ 18-35 km, and is believed to be due to baseline wave features that are present in the spectra. A time series analysis of KIMRA ozone for winters 2008-2013 shows the existence of a local wintertime minimum in the ozone profile above Kiruna. The measurements have been ongoing at Kiruna since 2002 and late 2012 for KIMRA and MIRA 2, respectively.

  20. Project management for complex ground-based instruments: MEGARA plan

    Science.gov (United States)

    García-Vargas, María. Luisa; Pérez-Calpena, Ana; Gil de Paz, Armando; Gallego, Jesús; Carrasco, Esperanza; Cedazo, Raquel; Iglesias, Jorge

    2014-08-01

    The project management of complex instruments for ground-based large telescopes is a challenge itself. A good management is a clue for project success in terms of performance, schedule and budget. Being on time has become a strict requirement for two reasons: to assure the arrival at the telescope due to the pressure on demanding new instrumentation for this first world-class telescopes and to not fall in over-costs. The budget and cash-flow is not always the expected one and has to be properly handled from different administrative departments at the funding centers worldwide distributed. The complexity of the organizations, the technological and scientific return to the Consortium partners and the participation in the project of all kind of professional centers working in astronomical instrumentation: universities, research centers, small and large private companies, workshops and providers, etc. make the project management strategy, and the tools and procedures tuned to the project needs, crucial for success. MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is a facility instrument of the 10.4m GTC (La Palma, Spain) working at optical wavelengths that provides both Integral-Field Unit (IFU) and Multi-Object Spectrograph (MOS) capabilities at resolutions in the range R=6,000-20,000. The project is an initiative led by Universidad Complutense de Madrid (Spain) in collaboration with INAOE (Mexico), IAA-CSIC (Spain) and Universidad Politécnica de Madrid (Spain). MEGARA is being developed under contract with GRANTECAN.

  1. Accuracy of vertical radial plume mapping technique in measuring lagoon gas emission

    Science.gov (United States)

    Recently, the U.S. Environmental Protection Agency (USEPA) posted a ground-based optical remote sensing method on its website called OTM 10 for measuring fugitive gas emission flux from area sources such as closed landfills. The OTM 10 utilizes the vertical radial plume mapping (VRPM) technique to c...

  2. An empirical RBF model of the magnetosphere parameterized by interplanetary and ground-based drivers

    Science.gov (United States)

    Tsyganenko, N. A.; Andreeva, V. A.

    2016-11-01

    In our recent paper (Andreeva and Tsyganenko, 2016), a novel method was proposed to model the magnetosphere directly from spacecraft data, with no a priori knowledge nor ad hoc assumptions about the geometry of the magnetic field sources. The idea was to split the field into the toroidal and poloidal parts and then expand each part into a weighted sum of radial basis functions (RBF). In the present work we take the next step forward by having developed a full-fledged model of the near magnetosphere, based on a multiyear set of space magnetometer data (1995-2015) and driven by ground-based and interplanetary input parameters. The model consolidates the largest ever amount of data and has been found to provide the best ever merit parameters, in terms of both the overall RMS residual field and record-high correlation coefficients between the observed and model field components. By experimenting with different combinations of input parameters and their time-averaging intervals, we found the best so far results to be given by the ram pressure Pd, SYM-H, and N-index by Newell et al. (2007). In addition, the IMF By has also been included as a model driver, with a goal to more accurately represent the IMF penetration effects. The model faithfully reproduces both externally and internally induced variations in the global distribution of the geomagnetic field and electric currents. Stronger solar wind driving results in a deepening of the equatorial field depression and a dramatic increase of its dawn-dusk asymmetry. The Earth's dipole tilt causes a consistent deformation of the magnetotail current sheet and a significant north-south asymmetry of the polar cusp depressions on the dayside. Next steps to further develop the new approach are also discussed.

  3. Combined ground-based optical support for the aurora (DELTA) sounding rocket campaign

    Science.gov (United States)

    Griffin, Eoghan; Kosch, Mike; Aruliah, Anasuya; Kavanagh, Andrew; McWhirter, Ian; Senior, Andrew; Ford, Elaina; Davis, Chris; Abe, Takumi; Kurihara, Junichi; Kauristie, Kirsti; Ogawa, Yasunobu

    2006-09-01

    The Japan Aerospace Exploration Agency (JAXA) DELTA rocket experiment, successfully launched from Andøya at 0033 UT on December 13, 2004, supported by ground based optical instruments, primarily 2 Fabry- Perot Interferometers (FPIs) located at Skibotn, Norway (69.3°N, 20.4°E) and the KEOPS Site, Esrange, Kiruna, Sweden (67.8°N, 20.4°E). Both these instruments sampled the 557.7 nm lower thermosphere atomic oxygen emission and provided neutral temperatures and line-of-sight wind velocities, with deduced vector wind patterns over each site. All sky cameras allow contextual auroral information to be acquired. The proximity of the sites provided overlapping fields of view, adjacent to the trajectory of the DELTA rocket. This allowed independent verification of the absolute temperatures in the relatively quiet conditions early in the night, especially important given the context provided by co-located EISCAT ion temperature measurements which allow investigation of the likely emission altitude of the passive FPI measurements. The results demonstrate that this altitude changes from 120 km pre-midnight to 115 km post-midnight. Within this large scale context the results from the FPIs also demonstrate smaller scale structure in neutral temperatures, winds and intensities consistent with localised heating. These results present a challenge to the representation of thermospheric variability for the existing models of the region.

  4. Ground Based Investigation of Electrostatic Accelerometer in HUST

    Science.gov (United States)

    Bai, Y.; Zhou, Z.

    2013-12-01

    High-precision electrostatic accelerometers with six degrees of freedom (DOF) acceleration measurement were successfully used in CHAMP, GRACE and GOCE missions which to measure the Earth's gravity field. In our group, space inertial sensor based on the capacitance transducer and electrostatic control technique has been investigated for test of equivalence principle (TEPO), searching non-Newtonian force in micrometer range, and satellite Earth's field recovery. The significant techniques of capacitive position sensor with the noise level at 2×10-7pF/Hz1/2 and the μV/Hz1/2 level electrostatic actuator are carried out and all the six servo loop controls by using a discrete PID algorithm are realized in a FPGA device. For testing on ground, in order to compensate one g earth's gravity, the fiber torsion pendulum facility is adopt to measure the parameters of the electrostatic controlled inertial sensor such as the resolution, and the electrostatic stiffness, the cross couple between different DOFs. A short distance and a simple double capsule equipment the valid duration about 0.5 second is set up in our lab for the free fall tests of the engineering model which can directly verify the function of six DOF control. Meanwhile, high voltage suspension method is also realized and preliminary results show that the horizontal axis of acceleration noise is about 10-8m/s2/Hz1/2 level which limited mainly by the seismic noise. Reference: [1] Fen Gao, Ze-Bing Zhou, Jun Luo, Feasibility for Testing the Equivalence Principle with Optical Readout in Space, Chin. Phys. Lett. 28(8) (2011) 080401. [2] Z. Zhu, Z. B. Zhou, L. Cai, Y. Z. Bai, J. Luo, Electrostatic gravity gradiometer design for the advanced GOCE mission, Adv. Sp. Res. 51 (2013) 2269-2276. [3] Z B Zhou, L Liu, H B Tu, Y Z Bai, J Luo, Seismic noise limit for ground-based performance measurements of an inertial sensor using a torsion balance, Class. Quantum Grav. 27 (2010) 175012. [4] H B Tu, Y Z Bai, Z B Zhou, L Liu, L

  5. Ground-Based Observing Campaign of Briz-M Debris

    Science.gov (United States)

    Lederer, S. M.; Buckalew, B.; Frith, J.; Cowardin, H. M.; Hickson, P.; Matney, M.; Anz-Meador, P.

    2017-01-01

    In 2015, NASA's Orbital Debris Program Office (ODPO) completed the installation of the Meter Class Autonomous Telescope (MCAT) on Ascension Island. MCAT is a 1.3m optical telescope designed with a fast tracking capability for observing orbital debris at all orbital regimes (Low-Erath orbits to Geosyncronous (GEO) orbits) from a low latitude site. This new asset is dedicated year-round for debris observations, and its location fills a geographical gap in the Ground-based Electro Optical Space Surveillance (GEODSS) network. A commercial off the shelf (COTS) research grade 0.4m telescope (named the Benbrook telescope) will also be installed on Ascension at the end of 2016. This smaller version is controlled by the same master software, designed by Euclid Research, and can be tasked to work independently or in concert with MCAT. Like MCAT, it has a the same suite of filters, a similar field of view, and a fast-tracking Astelco mount, and is also capable of tracking debris at all orbital regimes. These assets are well suited for targeted campagins or surveys of debris. Since 2013, NASA's ODPO has also had extensive access to the 3.8m infrared UKIRT telescope, located on Mauna Kea. At nearly 14,000-ft, this site affords excellent conditions for collecting both photometery and spectroscopy at near-IR (0.9 - 2.5 micrometers SWIR) and thermal-IR (8 - 25 micrometers; LWIR) regimes, ideal for investigating material properties as well as thermal characteristics and sizes of debris. For the purposes of understanding orbital debris, taking data in both survey mode as well as targeting individual objects for more in-depth characterizations are desired. With the recent break-ups of Briz-M rocket bodies, we have collected a suite of data in the optical, near-infrared, and mid-infrared of in-tact objects as well as those classified as debris. A break-up at GEO of a Briz-M rocket occurred in January, 2016, well timed for the first remote observing survey-campaign with MCAT. Access to

  6. Computer program calculates transonic velocities in turbomachines

    Science.gov (United States)

    Katsanis, T.

    1971-01-01

    Computer program, TSONIC, combines velocity gradient and finite difference methods to obtain numerical solution for ideal, transonic, compressible flow for axial, radial, or mixed flow cascade of turbomachinery blades.

  7. Energy velocity and group velocity

    Institute of Scientific and Technical Information of China (English)

    陈宇

    1995-01-01

    A new Lagrangian method for studying the relationship between the energy velocity and the group velocity is described. It is proved that under the usual quasistatic electric field, the energy velocity is identical to the group velocity for acoustic waves in anisotropic piezoelectric (or non-piezoelectric) media.

  8. Ground-based monitoring of solar radiation in Moldova

    Science.gov (United States)

    Aculinin, Alexandr; Smicov, Vladimir

    2010-05-01

    Integrated measurements of solar radiation in Kishinev, Moldova have been started by Atmospheric Research Group (ARG) at the Institute of Applied Physics from 2003. Direct, diffuse and total components of solar and atmospheric long-wave radiation are measured by using of the radiometric complex at the ground-based solar radiation monitoring station. Measurements are fulfilled at the stationary and moving platforms equipped with the set of 9 broadband solar radiation sensors overlapping wavelength range from UV-B to IR. Detailed description of the station can be found at the site http://arg.phys.asm.md. Ground station is placed in an urban environment of Kishinev city (47.00N; 28.56E). Summary of observation data acquired at the station in the course of short-term period from 2004 to 2009 are presented below. Solar radiation measurements were fulfilled by using CM11(280-3000 nm) and CH1 sensors (Kipp&Zonen). In the course of a year maximum and minimum of monthly sums of total radiation was ~706.4 MJm-2 in June and ~82.1MJm-2 in December, respectively. Monthly sums of direct solar radiation (on horizontal plane) show the maximum and minimum values of the order ~456.9 MJm-2 in July and ~25.5MJm-2 in December, respectively. In an average, within a year should be marked the predominance of direct radiation over the scattered radiation, 51% and 49%, respectively. In the course of a year, the percentage contribution of the direct radiation into the total radiation is ~55-65% from May to September. In the remaining months, the percentage contribution decreases and takes the minimum value of ~ 28% in December. In an average, annual sum of total solar radiation is ~4679.9 MJm-2. For the period from April to September accounts for ~76% of the annual amount of total radiation. Annual sum of sunshine duration accounts for ~2149 hours, which is of ~ 48% from the possible sunshine duration. In an average, within a year maximum and minimum of sunshine duration is ~ 304 hours in

  9. Biosensors for EVA: Improved Instrumentation for Ground-based Studies

    Science.gov (United States)

    Soller, B.; Ellerby, G.; Zou, F.; Scott, P.; Jin, C.; Lee, S. M. C.; Coates, J.

    2010-01-01

    During lunar excursions in the EVA suit, real-time measurement of metabolic rate is required to manage consumables and guide activities to ensure safe return to the base. Metabolic rate, or oxygen consumption (VO2), is normally measured from pulmonary parameters but cannot be determined with standard techniques in the oxygen-rich environment of a spacesuit. Our group has developed novel near infrared spectroscopic (NIRS) methods to calculate muscle oxygen saturation (SmO 2), hematocrit, and pH, and we recently demonstrated that we can use our NIRS sensor to measure VO 2 on the leg during cycling. Our NSBRI project has 4 objectives: (1) increase the accuracy of the metabolic rate calculation through improved prediction of stroke volume; (2) investigate the relative contributions of calf and thigh oxygen consumption to metabolic rate calculation for walking and running; (3) demonstrate that the NIRS-based noninvasive metabolic rate methodology is sensitive enough to detect decrement in VO 2 in a space analog; and (4) improve instrumentation to allow testing within a spacesuit. Over the past year we have made progress on all four objectives, but the most significant progress was made in improving the instrumentation. The NIRS system currently in use at JSC is based on fiber optics technology. Optical fiber bundles are used to deliver light from a light source in the monitor to the patient, and light reflected back from the patient s muscle to the monitor for spectroscopic analysis. The fiber optic cables are large and fragile, and there is no way to get them in and out of the test spacesuit used for ground-based studies. With complimentary funding from the US Army, we undertook a complete redesign of the sensor and control electronics to build a novel system small enough to be used within the spacesuit and portable enough to be used by a combat medic. In the new system the filament lamp used in the fiber optic system was replaced with a novel broadband near infrared

  10. Biosensors for EVA: Improved Instrumentation for Ground-based Studies

    Science.gov (United States)

    Soller, B.; Ellerby, G.; Zou, F.; Scott, P.; Jin, C.; Lee, S. M. C.; Coates, J.

    2010-01-01

    During lunar excursions in the EVA suit, real-time measurement of metabolic rate is required to manage consumables and guide activities to ensure safe return to the base. Metabolic rate, or oxygen consumption (VO2), is normally measured from pulmonary parameters but cannot be determined with standard techniques in the oxygen-rich environment of a spacesuit. Our group has developed novel near infrared spectroscopic (NIRS) methods to calculate muscle oxygen saturation (SmO 2), hematocrit, and pH, and we recently demonstrated that we can use our NIRS sensor to measure VO 2 on the leg during cycling. Our NSBRI project has 4 objectives: (1) increase the accuracy of the metabolic rate calculation through improved prediction of stroke volume; (2) investigate the relative contributions of calf and thigh oxygen consumption to metabolic rate calculation for walking and running; (3) demonstrate that the NIRS-based noninvasive metabolic rate methodology is sensitive enough to detect decrement in VO 2 in a space analog; and (4) improve instrumentation to allow testing within a spacesuit. Over the past year we have made progress on all four objectives, but the most significant progress was made in improving the instrumentation. The NIRS system currently in use at JSC is based on fiber optics technology. Optical fiber bundles are used to deliver light from a light source in the monitor to the patient, and light reflected back from the patient s muscle to the monitor for spectroscopic analysis. The fiber optic cables are large and fragile, and there is no way to get them in and out of the test spacesuit used for ground-based studies. With complimentary funding from the US Army, we undertook a complete redesign of the sensor and control electronics to build a novel system small enough to be used within the spacesuit and portable enough to be used by a combat medic. In the new system the filament lamp used in the fiber optic system was replaced with a novel broadband near infrared

  11. Ground-based Space Weather Monitoring with LOFAR

    Science.gov (United States)

    Wise, Michael; van Haarlem, Michiel; Lawrence, Gareth; Reid, Simon; Bos, Andre; Rawlings, Steve; Salvini, Stef; Mitchell, Cathryn; Soleimani, Manuch; Amado, Sergio; Teresa, Vital

    As one of the first of a new generation of radio instruments, the International LOFAR Telescope (ILT) will provide a number of unique and novel capabilities for the astronomical community. These include remote configuration and operation, dynamic real-time processing and system response, and the ability to provide multiple simultaneous streams of data to a community whose scientific interests run the gamut from lighting in the atmospheres of distant planets to the origins of the universe itself. The LOFAR (LOw Frequency ARray) system is optimized for a frequency range from 30-240 MHz and consists of multiple antenna fields spread across Europe. In the Netherlands, a total 36 LOFAR stations are nearing completion with an initial 8 international stations currently being deployed in Germany, France, Sweden, and the UK. Digital beam-forming techniques make the LOFAR system agile and allow for rapid repointing of the telescope as well as the potential for multiple simultaneous observations. With its dense core array and long interferometric baselines, LOFAR has the potential to achieve unparalleled sensitivity and spatial resolution in the low frequency radio regime. LOFAR will also be one of the first radio observatories to feature automated processing pipelines to deliver fully calibrated science products to its user community. As we discuss in this presentation, the same capabilities that make LOFAR a powerful tool for radio astronomy also provide an excellent platform upon which to build a ground-based monitoring system for space weather events. For example, the ability to monitor Solar activity in near real-time is one of the key scientific capabilities being developed for LOFAR. With only a fraction of its total observing capacity, LOFAR will be able to provide continuous monitoring of the Solar spectrum over the entire 10-240 MHz band down to microsecond timescales. Autonomous routines will scan these incoming spectral data for evidence of Solar flares and be

  12. Radial heat flux transformer

    Science.gov (United States)

    Basiulis, A.; Buzzard, R. J.

    1971-01-01

    Unit moves heat radially from small diameter shell to larger diameter shell, or vice versa, with negligible temperature drop, making device useful wherever heating or cooling of concentrically arranged materials, substances, and structures is desired.

  13. Model Predictions and Ground-based Observations for Jupiter's Magnetospheric Environment: Application to the JUICE and Juno Missions

    Science.gov (United States)

    Achilleos, Nicholas; Guio, Patrick; Arridge, Christopher S.; Ray, Licia C.; Yates, Japheth N.; Fossey, Stephen J.; Savini, Giorgio; Pearson, Mick; Fernando, Nathalie; Gerasimov, Roman; Murat, Thomas

    2016-10-01

    The advent of new missions to the Jovian system such as Juno (recently arrived) and JUICE (scheduled for 2022 launch) makes timely the provision of model-based predictions for the physical conditions to be encountered by these spacecraft; as well as the planning of simultaneous, ground-based observations of the Jovian system.Using the UCL Jovian magnetodisc model, which calculates magnetic field and plasma distributionsaccording to Caudal's (1986) force-balance formalism, we provide predictions of the following quantities along representative Juno / JUICE orbits through the middle magnetosphere: (i) Magnetic field strength and direction; (ii) Density and / or pressure of the 'cold' and 'hot' particle populations; (iii) Plasma angular velocity.The characteristic variation in these parameters is mainly influenced by the periodic approaches towards and recessions from the magnetodisc imposed on the 'synthetic spacecraft' by the planet's rotating, tilteddipole field. We also include some corresponding predictions for ionospheric / thermospheric conditions at the magnetic footpoint of the spacecraft, using the JASMIN model (Jovian Atmospheric Simulatorwith Magnetosphere, Ionosphere and Neutrals).We also present preliminary imaging results from 'IoSpot', a planned, ground-based programme of observations based at the University College London Observatory (UCLO) which targets ionized sulphur emissions from the Io plasma torus. Such programmes, conducted simultaneously with the above missions, will provide valuable context for the overall physical conditions within the Jovian magnetosphere, for which Io's volcanoes are the principal source of plasma.

  14. Close-up of primary and secondary asteroseismic CoRoT targets and the ground-based follow-up observations

    CERN Document Server

    Uytterhoeven, K; Rainer, M; Mantegazza, L; Zima, W; Aerts, C; Morel, T; Miglio, A; Lefever, K; Amado, P J; Mathias, P; Valtier, J C; Paparo, M; Benko, J M; CoRoT/SWG, the

    2007-01-01

    To optimise the science results of the asteroseismic part of the CoRoT satellite mission a complementary simultaneous ground-based observational campaign is organised for selected CoRoT targets. The observations include both high-resolution spectroscopic and multi-colour photometric data. We present the preliminary results of the analysis of the ground-based observations of three targets. A line-profile analysis of 216 high-resolution FEROS spectra of the delta Sct star HD 50844 reveals more than ten pulsation frequencies in the frequency range 5-18 c/d, including possibly one radial fundamental mode (6.92 c/d). Based on more than 600 multi-colour photometric datapoints of the beta Cep star HD180642, spanning about three years and obtained with different telescopes and different instruments, we confirm the presence of a dominant radial mode nu1=5.48695 c/d, and detect also its first two harmonics. We find evidence for a second mode nu2=0.3017 c/d, possibly a g-mode, and indications for two more frequencies in...

  15. Initial Results from the DEEPWAVE Airborne and Ground-Based Measurement Program in New Zealand in 2014

    Science.gov (United States)

    Fritts, Dave; Smith, Ron; Taylor, Mike; Doyle, Jim; Eckermann, Steve; Dörnbrack, Andreas; Rapp, Markus; Williams, Biff; Bossert, Katrina; Pautet, Dominique

    2015-04-01

    The deep-propagating gravity wave experiment (DEEPWAVE) was performed on and over New Zealand, Tasmania, the Tasman Sea, and the Southern Ocean with core airborne measurements extending from 5 June to 21 July 2014 and supporting ground-based measurements beginning in late May and extending beyond the airborne component. DEEPWAVE employed two aircraft, the NSF/NCAR GV and the German DLR Falcon. The GV carried the standard flight-level instruments, dropsondes, and the Microwave Temperature Profiler (MTP). It also hosted new airborne lidar and imaging instruments built specifically to allow quantification of gravity waves (GWs) from sources at lower altitudes (e.g., orography, convection, jet streams, fronts, and secondary GW generation) throughout the stratosphere and into the mesosphere and lower thermosphere (MLT). The new GV lidars included a Rayleigh lidar measuring atmospheric density and temperature from ~20-60 km and a sodium resonance lidar measuring sodium density and temperature at ~75-100 km. An airborne Advanced Mesosphere Temperature Mapper (AMTM) was also developed for the GV, and together with additional IR "wing" cameras, imaged the OH airglow temperature and/or intensity fields extending ~900 km across the GV flight track. The DLR Falcon was equipped with its standard flight-level instruments and an aerosol Doppler lidar able to measure radial winds below the Falcon where aerosol backscatter was sufficient. Additional ground-based instruments included a 449 MHz boundary layer radar, balloons at multiple sites, two ground-based Rayleigh lidars, a second ground-based AMTM, a Fabry Perot interferometer measuring winds and temperatures at ~87 and 95 km, and a meteor radar measuring winds from ~80-100 km. DEEPWAVE performed 26 GV flights, 13 Falcon flights, and an extensive series of ground-based measurements whether or not the aircraft were flying. Together, these observed many diverse cases of GW forcing, propagation, refraction, and dissipation

  16. [Approaches to radial shaft].

    Science.gov (United States)

    Bartoníček, J; Naňka, O; Tuček, M

    2015-10-01

    In the clinical practice, radial shaft may be exposed via two approaches, namely the posterolateral Thompson and volar (anterior) Henry approaches. A feared complication of both of them is the injury to the deep branch of the radial nerve. No consensus has been reached, yet, as to which of the two approaches is more beneficial for the proximal half of radius. According to our anatomical studies and clinical experience, Thompson approach is safe only in fractures of the middle and distal thirds of the radial shaft, but highly risky in fractures of its proximal third. Henry approach may be used in any fracture of the radial shaft and provides a safe exposure of the entire lateral and anterior surfaces of the radius.The Henry approach has three phases. In the first phase, incision is made along the line connecting the biceps brachii tendon and the styloid process of radius. Care must be taken not to damage the lateral cutaneous nerve of forearm.In the second phase, fascia is incised and the brachioradialis identified by the typical transition from the muscle belly to tendon and the shape of the tendon. On the lateral side, the brachioradialis lines the space with the radial artery and veins and the superficial branch of the radial nerve running at its bottom. On the medial side, the space is defined by the pronator teres in the proximal part and the flexor carpi radialis in the distal part. The superficial branch of the radial nerve is retracted together with the brachioradialis laterally, and the radial artery medially.In the third phase, the attachment of the pronator teres is identified by its typical tendon in the middle of convexity of the lateral surface of the radial shaft. The proximal half of the radius must be exposed very carefully in order not to damage the deep branch of the radial nerve. Dissection starts at the insertion of the pronator teres and proceeds proximally along its lateral border in interval between this muscle and insertion of the supinator

  17. Endoscopic versus open radial artery harvest and mammario-radial versus aorto-radial grafting in patients undergoing coronary artery bypass surgery

    DEFF Research Database (Denmark)

    Carranza, Christian L; Ballegaard, Martin; Werner, Mads U

    2014-01-01

    , it is unknown whether the endoscopic technique results in fewer complications or a graft patency comparable to open harvest. When the radial artery has been harvested, there are two ways to use the radial artery as a graft. One way is sewing it onto the aorta and another is sewing it onto the mammary artery......) mammario-radial open surgery group; and (4) aorto-radial open surgery group.The hand function will be assessed by a questionnaire, a clinical examination, the change in cutaneous sensibility, and the measurement of both sensory and motor nerve conduction velocity at 3 months postoperatively. All...... the postoperative complications will be registered, and we will evaluate muscular function, scar appearance, vascular supply to the hand, and the graft patency including the patency of the central radial artery anastomosis. A patency evaluation by multi-slice computer tomography will be done at one year...

  18. Experiments Using a Ground-Based Electrostatic Levitator and Numerical Modeling of Melt Convection for the Iron-Cobalt System in Support of Space Experiments

    Science.gov (United States)

    Lee, Jonghyun; SanSoucie, Michael P.

    2017-08-01

    Materials research is being conducted using an electromagnetic levitator installed in the International Space Station. Various metallic alloys were tested to elucidate unknown links among the structures, processes, and properties. To accomplish the mission of these space experiments, several ground-based activities have been carried out. This article presents some of our ground-based supporting experiments and numerical modeling efforts. Mass evaporation of Fe50Co50, one of flight compositions, was predicted numerically and validated by the tests using an electrostatic levitator (ESL). The density of various compositions within the Fe-Co system was measured with ESL. These results are being served as reference data for the space experiments. The convection inside a electromagnetically-levitated droplet was also modeled to predict the flow status, shear rate, and convection velocity under various process parameters, which is essential information for designing and analyzing the space experiments of some flight compositions influenced by convection.

  19. Crustal radial anisotropy beneath Cameroon from ambient noise tomography

    Science.gov (United States)

    Ojo, Adebayo Oluwaseun; Ni, Sidao; Li, Zhiwei

    2017-01-01

    To increase the understanding of crustal deformation and crustal flow patterns due to tectonic processes in Cameroon, we study the lateral variability of the crustal isotropic velocity and radial anisotropy estimated using Ambient Noise Tomography (ANT). Rayleigh and Love wave Noise Correlation Functions (NCFs) were retrieved from the cross-correlation of seismic ambient noise data recorded in Cameroon, and phase velocities at periods of 8 to 30 s were measured to perform surface wave tomography. Joint inversion of Rayleigh and Love wave data for isotropic velocity models could not fit the observed dispersions simultaneously. We attribute the Love-Rayleigh discrepancy to the presence of radial anisotropy in the crust and estimated its magnitude. Our 3-D radial anisotropic model reveals the spatial variation of strong to weak positive (Vsh > Vsv) and negative (Vsv > Vsh) radial anisotropy in the crust. We observe negative radial anisotropy in the upper crust that is associated mainly with the location of a previously reported mantle plume. The anisotropy could be attributed to the vertical alignment of fossil microcracks or metamorphic foliations due to the upwelling of plume material. A strong positive radial anisotropy is centered at the location of an inferred boundary between the Congo Craton and the Oubanguides Belt that might be related to the preferred orientation of crustal anisotropic minerals associated with shearing in this fault zone. The middle crust is characterized by a widespread negative radial anisotropy that is likely caused by the flow-induced alignment of anisotropic minerals that crystallized during magma intrusion. The magnitude of the radial anisotropy varies systematically from predominantly negative in the middle crust to positive in the lower crust. The imaged patterns of the isotropic velocity and radial anisotropy are consistent with previous studies and agree with regional tectonics.

  20. Improving the atmospheric wind speed measured accuracy by the ground-based airglow imaging interferometer

    Science.gov (United States)

    Tang, Yuanhe; Yang, Rui; Gao, Haiyang; Zhai, Fengtao; Yu, Yang; Cui, Jin

    2017-02-01

    A prototype ground based airglow imaging interferometer (GBAII) has been constructed to observe the upper atmospheric wind velocity and temperature at an altitude of 90-100 km, but the GBAII's wind speed accuracy was found to be unsatisfactory with a value of 21.0 m/s. Three theoretical aspects have been investigated to improve the accuracy, with the following finding: 1) By replacing the surface coatings of the GBAII's 6 lenses and Michelson interferometer (MI) with a new wind-speed infrared film rather than the original visible light film, the accuracy can be increased by 3.0 m/s. 2) By replacing the original charge-coupled device (CCD) with a quantum efficiency (QE) of 0.38 at the wavelength of approximately 866 nm by an electron multiplying CCD (EMCCD) with QE of 0.95, the accuracy can be increased by 6.7 m/s. By adding all the factors that improve the accuracy of the GBAII, it can be improved by 15.0 m/s, which realizes the original aim of wind speed accuracy of 6.0 m/s. Experimental results have been obtained for two aspects: 1) By replacing the surface film on the GBAII's 6 lenses and MI interface, the wind speed accuracy has been increased by 3.8 m/s. 2) A new GBAII temperature controller has been constructed to control the environmental temperature in 0.2 K steps. The results obtained by the GBAII on Dec. 6, 2013 show an average atmospheric temperature of 206.5 K, zonal wind speed of -26.8 m/s and meridional wind speed of 28.1 m/s. These results are close to those of the TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics) satellite Doppler interferometer (TIDI) data collected at almost the same time.

  1. Fast Radial Flows in Transition Disk Holes

    CERN Document Server

    Rosenfeld, Katherine A; Andrews, Sean M

    2013-01-01

    Protoplanetary "transition" disks have large, mass-depleted central cavities, yet also deliver gas onto their host stars at rates comparable to disks without holes. The paradox of simultaneous transparency and accretion can be explained if gas flows inward at much higher radial speeds inside the cavity than outside the cavity, since surface density (and by extension optical depth) varies inversely with inflow velocity at fixed accretion rate. Radial speeds within the cavity might even have to approach free-fall values to explain the huge surface density contrasts inferred for transition disks. We identify observational diagnostics of fast radial inflow in channel maps made in optically thick spectral lines. Signatures include (1) twisted isophotes in maps made at low systemic velocities and (2) rotation of structures observed between maps made in high-velocity line wings. As a test case, we apply our new diagnostic tools to archival ALMA data on the transition disk HD 142527, and uncover evidence for free-fal...

  2. Sentinel-1 and ground-based sensors for a continuous monitoring of the Corvara landslide kinematic (South Tirol, Italy)

    Science.gov (United States)

    Schlögel, Romy; Darvishi, Mehdi; Cuozzo, Giovanni; Kofler, Christian; Rutzinger, Martin; Zieher, Thomas; Toschi, Isabella; Remondino, Fabio

    2017-04-01

    Sentinel-1 mission allows us to have Synthetic Aperture Radar (SAR) acquisitions over large areas every 6 days with spatial resolution of 20 m. This new open-source generation of satellites has enhanced the capabilities for continuously studying earth surface changes. Over the past two decades, several studies have demonstrated the potential of Differential Synthetic Aperture Radar Interferometry (DInSAR) for detecting and quantifying land surface deformation. DInSAR limitations and challenges are linked to the SAR properties and the field conditions (especially in Alpine environments) leading to spatial and temporal decorrelation of the SAR signal. High temporal decorrelation can be caused by changes in vegetation (particularly in non-urban areas), atmospheric conditions or high ground surface velocity. In this study, kinematics of the complex and vegetated Corvara landslide, situated in Val Badia (South Tirol, Italy), are monitored by a network of 3 permanent and 13 monthly Differential Global Positioning System (DGPS) stations. The slope displacement rates are found to be highly unsteady and reach several meters a year. This analysis focuses on evaluating the limitations of Sentinel-1 imagery processed with Small Baseline Subset (SBAS) technique in comparison to ground-based measurements for assessing the landslide kinematic linked to meteorological conditions. Selecting some particular acquisitions, coherence thresholds and unwrapping processes gives various results in terms of reliability and accuracy supporting the understanding of the landslide velocity field. The evolution of the coherence and phase signals are studied according to the changing field conditions and the monitored ground-based displacements. DInSAR deformation maps and residual topographic heights are finally compared with difference of high resolution Digital Elevation Models at local scale. This research is conducted within the project LEMONADE (http://lemonade.mountainresearch.at) funded

  3. Ground-based Infrared Observations of Water Vapor and Hydrogen Peroxide in the Atmosphere of Mars

    Science.gov (United States)

    Encrenaz, T.; Greathouse, T. K.; Bitner, M.; Kruger, A.; Richter, M. J.; Lacy, J. H.; Bézard, B.; Fouchet, T.; Lefevre, F.; Forget, F.; Atreya, S. K.

    2008-11-01

    Ground-based observations of water vapor and hydrogen peroxide have been obtained in the thermal infrared range, using the TEXES instrument at the NASA Infrared Telescope Facility, for different times of the seasonal cycle.

  4. Informing hydrological models with ground-based time-lapse relative gravimetry: potential and limitations

    DEFF Research Database (Denmark)

    Bauer-Gottwein, Peter; Christiansen, Lars; Rosbjerg, Dan

    2011-01-01

    Coupled hydrogeophysical inversion emerges as an attractive option to improve the calibration and predictive capability of hydrological models. Recently, ground-based time-lapse relative gravity (TLRG) measurements have attracted increasing interest because there is a direct relationship between ...

  5. Changes in ground-based solar ultraviolet radiation during fire episodes: a case study

    CSIR Research Space (South Africa)

    Wright, CY

    2013-09-01

    Full Text Available about the relationship between fires and solar UVR without local high-quality column or ground-based ambient air pollution (particulate matter in particular) data; however, the threat to public health from fires was acknowledged....

  6. System Identification and Automatic Mass Balancing of Ground-Based Three-Axis Spacecraft Simulator

    Science.gov (United States)

    2006-08-01

    System Identification and Automatic Mass Balancing of Ground-Based Three-Axis Spacecraft Simulator Jae-Jun Kim∗ and Brij N. Agrawal † Department of...TITLE AND SUBTITLE System Identification and Automatic Mass Balancing of Ground-Based Three-Axis Spacecraft Simulator 5a. CONTRACT NUMBER 5b...and Dynamics, Vol. 20, No. 4, July-August 1997, pp. 625-632. 6Schwartz, J. L. and Hall, C. D., “ System Identification of a Spherical Air-Bearing

  7. Radial wedge flange clamp

    Science.gov (United States)

    Smith, Karl H.

    2002-01-01

    A radial wedge flange clamp comprising a pair of flanges each comprising a plurality of peripheral flat wedge facets having flat wedge surfaces and opposed and mating flat surfaces attached to or otherwise engaged with two elements to be joined and including a series of generally U-shaped wedge clamps each having flat wedge interior surfaces and engaging one pair of said peripheral flat wedge facets. Each of said generally U-shaped wedge clamps has in its opposing extremities apertures for the tangential insertion of bolts to apply uniform radial force to said wedge clamps when assembled about said wedge segments.

  8. VizieR Online Data Catalog: STELLA-SES Radial Veocities of HD 208472 (Ozdarcan+, 2016)

    Science.gov (United States)

    Ozdarcan, O.; Carroll, T. A.; Kunstler, A.; Strassmeier, K. G.; Evren, S.; Weber, M.; Granzer, T.

    2016-07-01

    Precise radial velocity measurement of HD 208472 based on 229 high resolution Stella Echelle Spectrograph (SES) spectra obtained at STELLA robotic observatory on Tenerife, Spain from March 22, 2009 to July 20, 2011 are presented. High precision radial velocities allow one to trace spot jitter effect on measured radial velocities via residuals from spectroscopic orbit solution. In case of HD 208472, removing spot jitter effect from measured velocities, precision on calculated orbital parameters were improved by factor of 4 without changing the actual value of parameters. (1 data file).

  9. Radial Halbach Magnetic Bearings

    Science.gov (United States)

    Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

    2009-01-01

    Radial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Radial Halbach magnetic bearings are based on the same principle as that of axial Halbach magnetic bearings, differing in geometry as the names of these two types of bearings suggest. Both radial and axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control. Axial Halbach magnetic bearings were described in Axial Halbach Magnetic Bearings (LEW-18066-1), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), page 85. In the remainder of this article, the description of the principle of operation from the cited prior article is recapitulated and updated to incorporate the present radial geometry. In simplest terms, the basic principle of levitation in an axial or radial Halbach magnetic bearing is that of the repulsive electromagnetic force between (1) a moving permanent magnet and (2) an electric current induced in a stationary electrical conductor by the motion of the magnetic field. An axial or radial Halbach bearing includes multiple permanent magnets arranged in a Halbach array ("Halbach array" is defined below) in a rotor and multiple conductors in the form of wire coils in a stator, all arranged so the rotary motion produces an axial or radial repulsion that is sufficient to levitate the rotor. A basic Halbach array (see Figure 1) consists of a row of permanent magnets, each oriented so that its magnetic field is at a right angle to that of the adjacent magnet, and the right-angle turns are sequenced so as to maximize the magnitude of the magnetic flux density on one side of the row while

  10. Radial Velocities and Binarity of Southern SIM Grid Stars

    Science.gov (United States)

    2015-01-01

    of RV measurements only capture the instrumental part of the error budget, mostly the photon shot noise. A significant part, and in fact , the larger...the range 0.005–0.008M of companion mass, thus, these data should be sensitive to super- Jupiters and brown dwarf companions in 1-yr orbits. The absence...freedom. Hence, these results do not preclude the exis- tence of a limited number (∼20) of super- Jupiter planets or brown dwarf companions in our

  11. A survey of radial velocities in the zodiacal dust cloud

    CERN Document Server

    May, Brian Harold

    2008-01-01

    The Zodiacal Light, that misty diffuse cone of light seen in the West after Sunset and the East before Sunrise, is a beautiful and intriguing phenomenon. Even though everyone can enjoy the sight from a suitably dark location, it is poorly understood, and has been the subject of relatively little research. Brian May began his research into the subject in 1970, and was finally awarded his PhD in 2007, after a hiatus of more than 30 years pursuing his other career as guitarist with his rock band Queen. This book is Brian 's thesis, and as such presents the results of his research for astronomers.

  12. Interpolation of the Radial Velocity Data from Coastal HF Radars

    Science.gov (United States)

    2013-01-01

    similar to the ones used in [20] for OMA processing of HFR observations in the Bodega Bay. The coordinate system is rotated clockwise (north is on...geometry of the 3-radar experiment in the Bodega Bay conducted in spring and summer of 2003 (Fig. 1). In the second series real data acquired on...July 30, 2003 in the Bodega Bay and offshore the coast of Brittany has been used. 2.2.1. Experiments with Simulated Data Simulated data experiments

  13. Improved Lattice Radial Quantization

    CERN Document Server

    Brower, Richard C; Fleming, George T

    2014-01-01

    Lattice radial quantization was proposed in a recent paper by Brower, Fleming and Neuberger[1] as a nonperturbative method especially suited to numerically solve Euclidean conformal field theories. The lessons learned from the lattice radial quantization of the 3D Ising model on a longitudinal cylinder with 2D Icosahedral cross-section suggested the need for an improved discretization. We consider here the use of the Finite Element Methods(FEM) to descretize the universally-equivalent $\\phi^4$ Lagrangian on $\\mathbb R \\times \\mathbb S^2$. It is argued that this lattice regularization will approach the exact conformal theory at the Wilson-Fisher fixed point in the continuum. Numerical tests are underway to support this conjecture.

  14. The ARCS radial collimator

    OpenAIRE

    Stone M.B.; Niedziela J.L.; Overbay M.A.; Abernathy D.L.

    2015-01-01

    We have designed, installed, and commissioned a scattered beam radial collimator for use at the ARCS Wide Angular Range Chopper Spectrometer at the Spallation Neutron Source. The collimator has been designed to work effectively for thermal and epithermal neutrons and with a range of sample environments. Other design considerations include the accommodation of working within a high vacuum environment and having the ability to quickly install and remove the collimator from the scattered beam. W...

  15. Gravitational-Wave Tests of General Relativity with Ground-Based Detectors and Pulsar-Timing Arrays

    Directory of Open Access Journals (Sweden)

    Nicolás Yunes

    2013-11-01

    Full Text Available This review is focused on tests of Einstein's theory of general relativity with gravitational waves that are detectable by ground-based interferometers and pulsar-timing experiments. Einstein’s theory has been greatly constrained in the quasi-linear, quasi-stationary regime, where gravity is weak and velocities are small. Gravitational waves will allow us to probe a complimentary, yet previously unexplored regime: the non-linear and dynamical strong-field regime. Such a regime is, for example, applicable to compact binaries coalescing, where characteristic velocities can reach fifty percent the speed of light and gravitational fields are large and dynamical. This review begins with the theoretical basis and the predicted gravitational-wave observables of modified gravity theories. The review continues with a brief description of the detectors, including both gravitational-wave interferometers and pulsar-timing arrays, leading to a discussion of the data analysis formalism that is applicable for such tests. The review ends with a discussion of gravitational-wave tests for compact binary systems.

  16. Gravitational-Wave Tests of General Relativity with Ground-Based Detectors and Pulsar-Timing Arrays.

    Science.gov (United States)

    Yunes, Nicolás; Siemens, Xavier

    2013-01-01

    This review is focused on tests of Einstein's theory of general relativity with gravitational waves that are detectable by ground-based interferometers and pulsar-timing experiments. Einstein's theory has been greatly constrained in the quasi-linear, quasi-stationary regime, where gravity is weak and velocities are small. Gravitational waves will allow us to probe a complimentary, yet previously unexplored regime: the non-linear and dynamical strong-field regime. Such a regime is, for example, applicable to compact binaries coalescing, where characteristic velocities can reach fifty percent the speed of light and gravitational fields are large and dynamical. This review begins with the theoretical basis and the predicted gravitational-wave observables of modified gravity theories. The review continues with a brief description of the detectors, including both gravitational-wave interferometers and pulsar-timing arrays, leading to a discussion of the data analysis formalism that is applicable for such tests. The review ends with a discussion of gravitational-wave tests for compact binary systems.

  17. Perceived radial translation during centrifugation

    NARCIS (Netherlands)

    Bos, J.E.; Correia Grácio, B.J.

    2015-01-01

    BACKGROUND: Linear acceleration generally gives rise to translation perception. Centripetal acceleration during centrifugation, however, has never been reported giving rise to a radial, inward translation perception. OBJECTIVE: To study whether centrifugation can induce a radial translation percepti

  18. Ground-based Radar Detection of Near-Earth Asteroids%近地小行星地基雷达探测研究现状

    Institute of Scientific and Technical Information of China (English)

    张翔; 季江徽

    2014-01-01

    Ground-based radar detection may act as a powerful means to determine the shape and physical properties of the asteroids in our Solar system. By measuring time delay and doppler frequency of the received echoes, radar systems provide information in ranging and radial velocity of the asteroids. Over the past few decades, more than 500 asteroids (mostly near-Earth ob jects) were detected using radar observations. There are two categories of radar detection: (1) The continuous wave detection, which is adopted to determine the roughness of an asteroid’s surface. (2) The delay-Doppler de-tection,which is likely to produce its three-dimensional model, and to define the rotational state. In the delay-Doppler detection, target asteroids are resolved in line-of-sight distance and line-of-sight velocity, providing two-dimensional images with spatial resolution as fine as meter-scale. Besides radar detection, several other techniques would also provide the shape model of the asteroids, among which the lightcurve inverse method is the most popular one to do that. In comparison with other methods, radar observation may have an advantage on spacial resolution. The lightcurves cannot reveal elaborate information on small features, and the intermediate-scale features of the inversed model are only suggestive. By contrast, radar detection produces resolved images. In this review, we present the radar observation technique and the method for recon-structing three-dimensional models of asteroids from radar measurements. In addition, we also provide several examples of asteroid models by radar detection, and then compare them with other observations for the shape reconstruction for the asteroids.%地基雷达探测是研究太阳系中小行星的重要方法。雷达探测主要有两种方式:(1)连续波探测,可得到小行星表面的粗糙度等参数;(2)延迟多普勒探测,用于反演小行星的三维形状模型并确定自转轴状态。与其他探测方法

  19. Antiproton compression and radial measurements

    Science.gov (United States)

    Andresen, G. B.; Bertsche, W.; Bowe, P. D.; Bray, C. C.; Butler, E.; Cesar, C. L.; Chapman, S.; Charlton, M.; Fajans, J.; Fujiwara, M. C.; Funakoshi, R.; Gill, D. R.; Hangst, J. S.; Hardy, W. N.; Hayano, R. S.; Hayden, M. E.; Humphries, A. J.; Hydomako, R.; Jenkins, M. J.; Jørgensen, L. V.; Kurchaninov, L.; Lambo, R.; Madsen, N.; Nolan, P.; Olchanski, K.; Olin, A.; Page, R. D.; Povilus, A.; Pusa, P.; Robicheaux, F.; Sarid, E.; El Nasr, S. Seif; Silveira, D. M.; Storey, J. W.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.; Yamazaki, Y.

    2008-08-01

    Control of the radial profile of trapped antiproton clouds is critical to trapping antihydrogen. We report detailed measurements of the radial manipulation of antiproton clouds, including areal density compressions by factors as large as ten, achieved by manipulating spatially overlapped electron plasmas. We show detailed measurements of the near-axis antiproton radial profile, and its relation to that of the electron plasma. We also measure the outer radial profile by ejecting antiprotons to the trap wall using an octupole magnet.

  20. Mesoscale ionospheric electrodynamics of omega bands determined from ground-based electromagnetic and satellite optical observations

    Directory of Open Access Journals (Sweden)

    O. Amm

    2005-02-01

    Full Text Available We present ground-based electromagnetic data from the MIRACLE and BEAR networks and satellite optical observations from the UVI and PIXIE instruments on the Polar satellite of an omega band event over Northern Scandinavia on 26 June 1998, which occured close to the morning side edge of a substorm auroral bulge. Our analysis of the data concentrates on one omega band period from 03:18-03:27 UT, for which we use the method of characteristics combined with an analysis of the UVI and PIXIE data to derive a time series of instantaneous, solely data-based distributions of the mesoscale ionospheric electrodynamic parameters with a 1-min time resolution. In addition, the AMIE method is used to derive global Hall conductance patterns. Our results show that zonally alternating regions of enhanced ionospheric conductances ("tongues" up to ~60S and low conductance regions are associated with the omega bands. The tongues have a poleward extension of ~400km from their base and a zonal extension of ~380km. While they are moving coherently eastward with a velocity of ~770ms-1, the structures are not strictly stationary. The current system of the omega band can be described as a superposition of two parts: one consists of anticlockwise rotating Hall currents around the tongues, along with Pedersen currents, with a negative divergence in their centers. The sign of this system is reversing in the low conductance areas. It causes the characteristic ground magnetic signature. The second part consists of zonally aligned current wedges of westward flowing Hall currents and is mostly magnetically invisible below the ionosphere. This system dominates the field-aligned current (FAC pattern and causes alternating upward and downward FAC at the flanks of the tongues with maximum upward FAC of ~25µA m-2. The total FAC of ~2MA are comparable to the ones diverted inside a westward traveling surge. Throughout the event, the overwhelming part of the FAC