WorldWideScience

Sample records for broadband stellar photometry

  1. Stellar photometry and polarimetry

    International Nuclear Information System (INIS)

    Golay, M.; Serkowski, K.

    1976-01-01

    A critical review of progress made in stellar photometry and polarimetry over the period 1973-1975 is presented. Reports of photometric measurements from various observatories throughout the world are summarized. The summary of work on stellar polarimetry lists the review papers, the catalogues and lists of standard stars, and descriptions of new observing techniques. (B.R.H.)

  2. THE ESTIMATION OF STAR FORMATION RATES AND STELLAR POPULATION AGES OF HIGH-REDSHIFT GALAXIES FROM BROADBAND PHOTOMETRY

    International Nuclear Information System (INIS)

    Lee, Seong-Kook; Ferguson, Henry C.; Somerville, Rachel S.; Wiklind, Tommy; Giavalisco, Mauro

    2010-01-01

    We explore methods to improve the estimates of star formation rates and mean stellar population ages from broadband photometry of high-redshift star-forming galaxies. We use synthetic spectral templates with a variety of simple parametric star formation histories to fit broadband spectral energy distributions. These parametric models are used to infer ages, star formation rates, and stellar masses for a mock data set drawn from a hierarchical semi-analytic model of galaxy evolution. Traditional parametric models generally assume an exponentially declining rate of star formation after an initial instantaneous rise. Our results show that star formation histories with a much more gradual rise in the star formation rate are likely to be better templates, and are likely to give better overall estimates of the age distribution and star formation rate distribution of Lyman break galaxies (LBGs). For B- and V-dropouts, we find the best simple parametric model to be one where the star formation rate increases linearly with time. The exponentially declining model overpredicts the age by 100% and 120% for B- and V-dropouts, on average, while for a linearly increasing model, the age is overpredicted by 9% and 16%, respectively. Similarly, the exponential model underpredicts star formation rates by 56% and 60%, while the linearly increasing model underpredicts by 15% and 22%, respectively. For U-dropouts, the models where the star formation rate has a peak (near z ∼ 3) provide the best match for age-overprediction is reduced from 110% to 26%-and star formation rate-underprediction is reduced from 58% to 22%. We classify different types of star formation histories in the semi-analytic models and show how the biases behave for the different classes. We also provide two-band calibration formulae for stellar mass and star formation rate estimations.

  3. The STAGGER-grid: A grid of 3D stellar atmosphere models. V. Synthetic stellar spectra and broad-band photometry

    Science.gov (United States)

    Chiavassa, A.; Casagrande, L.; Collet, R.; Magic, Z.; Bigot, L.; Thévenin, F.; Asplund, M.

    2018-03-01

    Context. The surface structures and dynamics of cool stars are characterised by the presence of convective motions and turbulent flows which shape the emergent spectrum. Aims: We used realistic three-dimensional (3D) radiative hydrodynamical simulations from the STAGGER-grid to calculate synthetic spectra with the radiative transfer code OPTIM3D for stars with different stellar parameters to predict photometric colours and convective velocity shifts. Methods: We calculated spectra from 1000 to 200 000 Å with a constant resolving power of λ/Δλ = 20 000 and from 8470 and 8710 Å (Gaia Radial Velocity Spectrometer - RVS - spectral range) with a constant resolving power of λ/Δλ = 300 000. Results: We used synthetic spectra to compute theoretical colours in the Johnson-Cousins UBV (RI)C, SDSS, 2MASS, Gaia, SkyMapper, Strömgren systems, and HST-WFC3. Our synthetic magnitudes are compared with those obtained using 1D hydrostatic models. We showed that 1D versus 3D differences are limited to a small percent except for the narrow filters that span the optical and UV region of the spectrum. In addition, we derived the effect of the convective velocity fields on selected Fe I lines. We found the overall convective shift for 3D simulations with respect to the reference 1D hydrostatic models, revealing line shifts of between -0.235 and +0.361 km s-1. We showed a net correlation of the convective shifts with the effective temperature: lower effective temperatures denote redshifts and higher effective temperatures denote blueshifts. We conclude that the extraction of accurate radial velocities from RVS spectra need an appropriate wavelength correction from convection shifts. Conclusions: The use of realistic 3D hydrodynamical stellar atmosphere simulations has a small but significant impact on the predicted photometry compared with classical 1D hydrostatic models for late-type stars. We make all the spectra publicly available for the community through the POLLUX database

  4. The Space Stellar Photometry Mission COROT: Asteroseismology ...

    Indian Academy of Sciences (India)

    tribpo

    detect giant extra solar planets (detectable by spectroscopy from the ground) and determine their albedo. As COROT is devoted to stellar photometry, aiming at both a high precision and a long observation time, the search for exoplanets by the transit method can easily be integrated in the payload and in the mission profile.

  5. Ultraviolet photometry of stellar populations in galaxies

    International Nuclear Information System (INIS)

    Deharveng, J.M.

    1981-01-01

    The UV flux of stellar populations, which is essentially emitted by young stars, conveys information on the process of star formation and its recent history. However, the evaluation of the flux arising from the young stellar component may be difficult. In the case of late type galaxies it is hampered by the extinction and the effect of scattered stellar radiation. In the case of early type galaxies, the star formation, if any, has to be disentangled from the contribution of hot evolved stars and of a possible 'active' phenomenon. A review of observations and results relevant two cases is presented [fr

  6. Stellar CCD Photometry: New Approach, Principles and Application

    Science.gov (United States)

    El-Bassuny Alawy, A.

    A new approach is proposed and developed to handle pre-processed CCD frames in order to identify stellar images and derive their relevant parameters. It relies on: 1) Identifying stellar images and assigning approximate positions of their centres using an artificial intelligence technique, (Knowledge Based System), 2) Accurate determination of the centre co-ordinates applying an elementary statistical concept and 3) Estimating the image peak intensity as a stellar magnitude measure employing simple numerical analysis approach. The method has been coded for personal computer users. A CCD frame of the star cluster M67 was adopted as a test case. The results obtained are discussed in comparison with the DAOPHOTII ones and the corresponding published data. Exact coincidence has been found between both results except in very few cases. These exceptions have been discussed in the light of the basis of both methods and the cluster plates. It has been realised that the method suggested represents a very simple, extremely fast, high precision method of stellar CCD photometry. Moreover, it is more capable than DAOPHOTII of handling blended and distorted stellar images. These characteristics show the usefulness of the present method in some astronomical applications, such as auto-focusing and auto-guiding, beside the main purpose, viz. stellar photometry.

  7. Contamination of Broad-Band Photometry by Nebular Emission in High Redshift Galaxies: Investigations with Keck's MOSFIRE Near-Infrared Spectrograph

    OpenAIRE

    Schenker, Matthew A.; Ellis, Richard S.; Konidaris, Nick P.; Stark, Daniel P.

    2013-01-01

    Earlier work has raised the potential importance of nebular emission in the derivation of the physical characteristics of high-redshift Lyman break galaxies. Within certain redshift ranges, and especially at z ≃ 6-7, such lines may be strong enough to reduce estimates of the stellar masses and ages of galaxies compared with those derived assuming the broadband photometry represents stellar light alone. To test this hypothesis at the highest redshifts where such lines can be probed with ground...

  8. STELLAR ACTIVITY IN THE BROADBAND ULTRAVIOLET

    International Nuclear Information System (INIS)

    Findeisen, K.; Hillenbrand, L.; Soderblom, D.

    2011-01-01

    The completion of the GALEX All-Sky Survey in the ultraviolet allows activity measurements to be acquired for many more stars than is possible with the limited sensitivity of ROSAT or the limited sky coverage of Chandra, XMM, or spectroscopic surveys for line emission in the optical or ultraviolet. We have explored the use of GALEX photometry as an activity indicator, using stars within 50 pc as a calibration sample representing the field and in selected nearby associations representing the youngest stages of stellar evolution. We present preliminary relations between UV flux and the optical activity indicator R' HK and between UV flux and age. We demonstrate that far-UV (FUV, 1350-1780 A) excess flux is roughly proportional to R' HK . We also detect a correlation between near-UV (NUV, 1780-2830 A) flux and activity or age, but the effect is much more subtle, particularly for stars older than ∼0.5-1 Gyr. Both the FUV and NUV relations show large scatter, ∼0.2 mag when predicting UV flux, ∼0.18 dex when predicting R' HK , and ∼0.4 dex when predicting age. This scatter appears to be evenly split between observational errors in current state-of-the-art data and long-term activity variability in the sample stars.

  9. Applicability of Broad-Band Photometry for Determining the Properties of Stars and Interstellar Extinction

    Science.gov (United States)

    Sichevskij, S. G.

    2018-01-01

    The feasibility of the determination of the physical conditions in star's atmosphere and the parameters of interstellar extinction from broad-band photometric observations in the 300-3000 nm wavelength interval is studied using SDSS and 2MASS data. The photometric accuracy of these surveys is shown to be insufficient for achieving in practice the theoretical possibility of estimating the atmospheric parameters of stars based on ugriz and JHK s photometry exclusively because such determinations result in correlations between the temperature and extinction estimates. The uncertainty of interstellar extinction estimates can be reduced if prior data about the temperature are available. The surveys considered can nevertheless be potentially valuable sources of information about both stellar atmospheric parameters and the interstellar medium.

  10. Stellar photometry with the Wide Field/Planetary Camera of the Hubble Space Telescope

    International Nuclear Information System (INIS)

    Holtzman, J.A.

    1990-01-01

    Simulations of Wide Field/Planetary Camera (WF/PC) images are analyzed in order to discover the most effective techniques for stellar photometry and to evaluate the accuracy and limitations of these techniques. The capabilities and operation of the WF/PC and the simulations employed in the study are described. The basic techniques of stellar photometry and methods to improve these techniques for the WF/PC are discussed. The correct parameters for star detection, aperture photometry, and point-spread function (PSF) fitting with the DAOPHOT software of Stetson (1987) are determined. Consideration is given to undersampling of the stellar images by the detector; variations in the PSF; and the crowding of the stellar images. It is noted that, with some changes DAOPHOT, is able to generate photometry almost to the level of photon statistics. 10 refs

  11. CHARACTERIZATION OF SLOAN DIGITAL SKY SURVEY STELLAR PHOTOMETRY

    International Nuclear Information System (INIS)

    Fukugita, Masataka; Yasuda, Naoki; Doi, Mamoru; Gunn, James E.; York, Donald G.

    2011-01-01

    We study the photometric properties of stars in the data archive of the Sloan Digital Sky Survey (SDSS), the prime aim being to understand the photometric calibration over the entire data set. It is confirmed that the photometric calibration of point sources is accurately on the system defined by the SDSS standard stars. We have also confirmed that the photometric synthesis of the SDSS spectrophotometric data gives broadband fluxes that agree with the photometry with errors of no more than 0.04 mag and little systematic tilt with wavelength. This verifies that the response functions of the 2.5 m telescope system are well characterized. We locate stars in the SDSS photometric system, so that stars can roughly be classified into spectral classes from the color information. We show how metallicity and surface gravity affect colors, and that stars contained in the SDSS general catalog, plotted in color space, show a distribution that matches well with what is anticipated from the variations of metallicity and surface gravity. The color-color plots are perfectly consistent among the three samples-stars in the SDSS general catalog, SDSS standard stars, and spectrophotometric stars of Gunn and Stryker-especially when some considerations are taken into account of the differences (primarily metallicity) of the samples. We show that the g - r-inverse temperature relation is tight and can be used as a good estimator of the effective temperature of stars over a fairly wide range of effective temperatures. We also confirm that the colors of G2V stars in the SDSS photometric system match well with the Sun.

  12. Deriving Physical Properties from Broadband Photometry with Prospector: Description of the Model and a Demonstration of its Accuracy Using 129 Galaxies in the Local Universe

    Energy Technology Data Exchange (ETDEWEB)

    Leja, Joel; Johnson, Benjamin D.; Conroy, Charlie [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Dokkum, Pieter G. van [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Byler, Nell [Department of Astronomy, University of Washington, Seattle, WA 98185 (United States)

    2017-03-10

    Broadband photometry of galaxies measures an unresolved mix of complex stellar populations, gas, and dust. Interpreting these data is a challenge for models: many studies have shown that properties derived from modeling galaxy photometry are uncertain by a factor of two or more, and yet answering key questions in the field now requires higher accuracy than this. Here, we present a new model framework specifically designed for these complexities. Our model, Prospector- α , includes dust attenuation and re-radiation, a flexible attenuation curve, nebular emission, stellar metallicity, and a six-component nonparametric star formation history. The flexibility and range of the parameter space, coupled with Monte Carlo Markov chain sampling within the Prospector inference framework, is designed to provide unbiased parameters and realistic error bars. We assess the accuracy of the model with aperture-matched optical spectroscopy, which was excluded from the fits. We compare spectral features predicted solely from fits to the broadband photometry to the observed spectral features. Our model predicts H α luminosities with a scatter of ∼0.18 dex and an offset of ∼0.1 dex across a wide range of morphological types and stellar masses. This agreement is remarkable, as the H α luminosity is dependent on accurate star formation rates, dust attenuation, and stellar metallicities. The model also accurately predicts dust-sensitive Balmer decrements, spectroscopic stellar metallicities, polycyclic aromatic hydrocarbon mass fractions, and the age- and metallicity-sensitive features D{sub n}4000 and H δ . Although the model passes all these tests, we caution that we have not yet assessed its performance at higher redshift or the accuracy of recovered stellar masses.

  13. CONTAMINATION OF BROADBAND PHOTOMETRY BY NEBULAR EMISSION IN HIGH-REDSHIFT GALAXIES: INVESTIGATIONS WITH KECK'S MOSFIRE NEAR-INFRARED SPECTROGRAPH

    International Nuclear Information System (INIS)

    Schenker, Matthew A; Ellis, Richard S; Konidaris, Nick P; Stark, Daniel P

    2013-01-01

    Earlier work has raised the potential importance of nebular emission in the derivation of the physical characteristics of high-redshift Lyman break galaxies. Within certain redshift ranges, and especially at z ≅ 6-7, such lines may be strong enough to reduce estimates of the stellar masses and ages of galaxies compared with those derived assuming the broadband photometry represents stellar light alone. To test this hypothesis at the highest redshifts where such lines can be probed with ground-based facilities, we examine the near-infrared spectra of a representative sample of 28 3.0 < z < 3.8 Lyman break galaxies using the newly commissioned MOSFIRE near-infrared spectrograph at the Keck I telescope. We use these data to derive the rest-frame equivalent widths (EWs) of [O III] emission and show that these are comparable with estimates derived using the spectral energy distribution (SED) fitting technique introduced for sources of known redshift by Stark et al. Although our current sample is modest, its [O III] EW distribution is consistent with that inferred for Hα based on SED fitting of Stark et al.'s larger sample of 3.8 < z < 5 galaxies. For a subset of survey galaxies, we use the combination of optical and near-infrared spectroscopy to quantify kinematics of outflows in z ≅ 3.5 star-forming galaxies and discuss the implications for reionization measurements. The trends we uncover underline the dangers of relying purely on broadband photometry to estimate the physical properties of high-redshift galaxies and emphasize the important role of diagnostic spectroscopy

  14. A general method of estimating stellar astrophysical parameters from photometry

    NARCIS (Netherlands)

    Belikov, A. N.; Roeser, S.

    2008-01-01

    Context. Applying photometric catalogs to the study of the population of the Galaxy is obscured by the impossibility to map directly photometric colors into astrophysical parameters. Most of all-sky catalogs like ASCC or 2MASS are based upon broad-band photometric systems, and the use of broad

  15. CONTAMINATION OF BROADBAND PHOTOMETRY BY NEBULAR EMISSION IN HIGH-REDSHIFT GALAXIES: INVESTIGATIONS WITH KECK'S MOSFIRE NEAR-INFRARED SPECTROGRAPH

    Energy Technology Data Exchange (ETDEWEB)

    Schenker, Matthew A; Ellis, Richard S; Konidaris, Nick P [Department of Astrophysics, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Stark, Daniel P, E-mail: schenker@astro.caltech.edu [Department of Astronomy and Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)

    2013-11-01

    Earlier work has raised the potential importance of nebular emission in the derivation of the physical characteristics of high-redshift Lyman break galaxies. Within certain redshift ranges, and especially at z ≅ 6-7, such lines may be strong enough to reduce estimates of the stellar masses and ages of galaxies compared with those derived assuming the broadband photometry represents stellar light alone. To test this hypothesis at the highest redshifts where such lines can be probed with ground-based facilities, we examine the near-infrared spectra of a representative sample of 28 3.0 < z < 3.8 Lyman break galaxies using the newly commissioned MOSFIRE near-infrared spectrograph at the Keck I telescope. We use these data to derive the rest-frame equivalent widths (EWs) of [O III] emission and show that these are comparable with estimates derived using the spectral energy distribution (SED) fitting technique introduced for sources of known redshift by Stark et al. Although our current sample is modest, its [O III] EW distribution is consistent with that inferred for Hα based on SED fitting of Stark et al.'s larger sample of 3.8 < z < 5 galaxies. For a subset of survey galaxies, we use the combination of optical and near-infrared spectroscopy to quantify kinematics of outflows in z ≅ 3.5 star-forming galaxies and discuss the implications for reionization measurements. The trends we uncover underline the dangers of relying purely on broadband photometry to estimate the physical properties of high-redshift galaxies and emphasize the important role of diagnostic spectroscopy.

  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.

    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

  17. 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.

  18. THE 100 Myr STAR FORMATION HISTORY OF NGC 5471 FROM CLUSTER AND RESOLVED STELLAR PHOTOMETRY

    International Nuclear Information System (INIS)

    Garcia-Benito, Ruben; Perez, Enrique; Maiz Apellaniz, Jesus; Cervino, Miguel; Diaz, Angeles I.

    2011-01-01

    We show that star formation in the giant H II region NGC 5471 has been ongoing during the past 100 Myr. Using Hubble Space Telescope/Wide-Field Planetary Camera 2 F547M and F675W, ground-based JHK s , and GALEX FUV and NUV images, we have conducted a photometric study of the star formation history (SFH) in the massive giant extragalactic H II region NGC 5471 in M101. We perform a photometric study of the color-magnitude diagram (CMD) of the resolved stars and an integrated analysis of the main individual star-forming clusters and of NGC 5471 as a whole. The integrated UV-optical-NIR photometry for the whole region provides two different reference ages, 8 Myr and 60 Myr, revealing a complex SFH, clearly confirmed by the CMD-resolved stellar photometry analysis. The spatial distribution of the stars shows that the star formation in NGC 5471 has proceeded along the whole region during, at least, the last 100 Myr. The current ionizing clusters are enclosed within a large bubble, which is likely to have been produced by the stars that formed in a major event ∼20 Myr ago.

  19. THE STELLAR METALLICITY DISTRIBUTION FUNCTION OF THE GALACTIC HALO FROM SDSS PHOTOMETRY

    International Nuclear Information System (INIS)

    An, Deokkeun; Beers, Timothy C.; Johnson, Jennifer A.; Pinsonneault, Marc H.; Lee, Young Sun; Bovy, Jo; Ivezić, Željko; Carollo, Daniela; Newby, Matthew

    2013-01-01

    We explore the stellar metallicity distribution function of the Galactic halo based on SDSS ugriz photometry. A set of stellar isochrones is calibrated using observations of several star clusters and validated by comparisons with medium-resolution spectroscopic values over a wide range of metal abundance. We estimate distances and metallicities for individual main-sequence stars in the multiply scanned SDSS Stripe 82, at heliocentric distances in the range 5-8 kpc and |b| > 35°, and find that the in situ photometric metallicity distribution has a shape that matches that of the kinematically selected local halo stars from Ryan and Norris. We also examine independent kinematic information from proper-motion measurements for high Galactic latitude stars in our sample. We find that stars with retrograde rotation in the rest frame of the Galaxy are generally more metal poor than those exhibiting prograde rotation, which is consistent with earlier arguments by Carollo et al. that the halo system comprises at least two spatially overlapping components with differing metallicity, kinematics, and spatial distributions. The observed photometric metallicity distribution and that of Ryan and Norris can be described by a simple chemical evolution model by Hartwick (or by a single Gaussian distribution); however, the suggestive metallicity-kinematic correlation contradicts the basic assumption in this model that the Milky Way halo consists primarily of a single stellar population. When the observed metallicity distribution is deconvolved using two Gaussian components with peaks at [Fe/H] ≈ –1.7 and –2.3, the metal-poor component accounts for ∼20%-35% of the entire halo population in this distance range.

  20. PHAT STELLAR CLUSTER SURVEY. I. YEAR 1 CATALOG AND INTEGRATED PHOTOMETRY

    International Nuclear Information System (INIS)

    Johnson, L. Clifton; Dalcanton, Julianne J.; Fouesneau, Morgan; Hodge, Paul W.; Weisz, Daniel R.; Williams, Benjamin F.; Beerman, Lori C.; Seth, Anil C.; Caldwell, Nelson; Gouliermis, Dimitrios A.; Larsen, Søren S.; Olsen, Knut A. G.; San Roman, Izaskun; Sarajedini, Ata; Bianchi, Luciana; Dolphin, Andrew E.; Girardi, Léo; Guhathakurta, Puragra; Kalirai, Jason; Lang, Dustin

    2012-01-01

    The Panchromatic Hubble Andromeda Treasury (PHAT) survey is an ongoing Hubble Space Telescope (HST) multi-cycle program to obtain high spatial resolution imaging of one-third of the M31 disk at ultraviolet through near-infrared wavelengths. In this paper, we present the first installment of the PHAT stellar cluster catalog. When completed, the PHAT cluster catalog will be among the largest and most comprehensive surveys of resolved star clusters in any galaxy. The exquisite spatial resolution achieved with HST has allowed us to identify hundreds of new clusters that were previously inaccessible with existing ground-based surveys. We identify 601 clusters in the Year 1 sample, representing more than a factor of four increase over previous catalogs within the current survey area (390 arcmin 2 ). This work presents results derived from the first ∼25% of the survey data; we estimate that the final sample will include ∼2500 clusters. For the Year 1 objects, we present a catalog with positions, radii, and six-band integrated photometry. Along with a general characterization of the cluster luminosities and colors, we discuss the cluster luminosity function, the cluster size distributions, and highlight a number of individually interesting clusters found in the Year 1 search.

  1. PHAT STELLAR CLUSTER SURVEY. I. YEAR 1 CATALOG AND INTEGRATED PHOTOMETRY

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, L. Clifton; Dalcanton, Julianne J.; Fouesneau, Morgan; Hodge, Paul W.; Weisz, Daniel R.; Williams, Benjamin F.; Beerman, Lori C. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Seth, Anil C. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Caldwell, Nelson [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gouliermis, Dimitrios A. [Institut fuer Theoretische Astrophysik, Zentrum fuer Astronomie der Universitaet Heidelberg, Albert-Ueberle-Strasse 2, D-69120 Heidelberg (Germany); Larsen, Soren S. [Department of Astrophysics, IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen (Netherlands); Olsen, Knut A. G. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); San Roman, Izaskun; Sarajedini, Ata [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055 (United States); Bianchi, Luciana [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Dolphin, Andrew E. [Raytheon Company, 1151 East Hermans Road, Tucson, AZ 85756 (United States); Girardi, Leo [Osservatorio Astronomico di Padova-INAF, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Guhathakurta, Puragra [Department of Astronomy and Astrophysics, University of California Observatories/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Kalirai, Jason [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Lang, Dustin, E-mail: lcjohnso@astro.washington.edu [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); and others

    2012-06-20

    The Panchromatic Hubble Andromeda Treasury (PHAT) survey is an ongoing Hubble Space Telescope (HST) multi-cycle program to obtain high spatial resolution imaging of one-third of the M31 disk at ultraviolet through near-infrared wavelengths. In this paper, we present the first installment of the PHAT stellar cluster catalog. When completed, the PHAT cluster catalog will be among the largest and most comprehensive surveys of resolved star clusters in any galaxy. The exquisite spatial resolution achieved with HST has allowed us to identify hundreds of new clusters that were previously inaccessible with existing ground-based surveys. We identify 601 clusters in the Year 1 sample, representing more than a factor of four increase over previous catalogs within the current survey area (390 arcmin{sup 2}). This work presents results derived from the first {approx}25% of the survey data; we estimate that the final sample will include {approx}2500 clusters. For the Year 1 objects, we present a catalog with positions, radii, and six-band integrated photometry. Along with a general characterization of the cluster luminosities and colors, we discuss the cluster luminosity function, the cluster size distributions, and highlight a number of individually interesting clusters found in the Year 1 search.

  2. STELLAR POPULATIONS IN MEDIUM REDSHIFT CLUSTERS .2. OPTICAL-INFRARED PHOTOMETRY AND SPECTRA

    NARCIS (Netherlands)

    PICKLES, AJ; VANDERKRUIT, PC

    1991-01-01

    We present optical and infrared photometry (BV RI, J H K) and spectra of galaxies in 6 medium redshift clusters covering the redshift range 0.19 less-than-or-equal-to z less-than-or-equal-to 0.4. The array photometry is used to note the radial distribution of the cluster galaxies with optical and

  3. Broad-band time-resolved near infrared spectroscopy in the TJ-II stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, M.C.; Pastor, I.; Cal, E. de la; McCarthy, K.J. [Laboratorio Nacional de Fusion, CIEMAT, Madrid (Spain); Diaz, D. [Universidad Autonoma de Madrid, Dept Quimica Fisica Aplicada, Madrid (Spain)

    2014-11-15

    First experimental results on broad-band, time-resolved Near Infrared (NIR;here loosely defined as covering from 750 to 1650 nm) passive spectroscopy using a high sensitivity InGaAs detector are reported for the TJ-II Stellarator. Experimental set-up is described together with its main characteristics, the most remarkable ones being its enhanced NIR response, broadband spectrum acquisition in a single shot, and time-resolved measurements with up to 1.8 kHz spectral rate. Prospects for future work and more extended physics studies in this newly open spectral region in TJ-II are discussed. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. A 'Rosetta Stone' to Interpret the UV-HST Photometry of Multiple Stellar Populations in Globular Clusters

    Science.gov (United States)

    Renzini, Alvio

    2011-10-01

    In this proposal we intend to firmly identify the chemical species responsible for the UV and UV-optical color differences exhibited by the multiple stellar populations harboured by two Galactic globular clusters: omega Centauri and 47 Tucanae, one with highly helium enriched sub-populations {omega Centauri}, the other not.We plan to collect ultraviolet STIS spectra for stars in the crowded cores of the clusters, where HST photometry is already available for thousands of stars in more than 10 filters, from F225W to F850LP. This WFC3+ACS photometric database has allowed us to show that UV colors are remarkably effective in separating the different cluster sub-populations, and with the proposed STIS spectroscopy we can quantify the chemical abundance differences among such sub-populations, most notably in Nitrogen and Oxygen. The resulting calibration of the UV colors in terms of CNO abundances will provide a new effective tool for the chemical characterization of large numbers of globular cluster stars belonging to the various sub-populations in each cluster, and to better isolate the specific role of the helium abundance.The plan is to observe at least one star for each of the main principal stellar sub-populations in each of the two clusters. These objects are selected on the basis of their accurate photometry and astrometry already in hand, based on existing UV-HST images.

  5. The Stellar Populations of Two Ultra-diffuse Galaxies from Optical and Near-infrared Photometry

    Science.gov (United States)

    Pandya, Viraj; Romanowsky, Aaron J.; Laine, Seppo; Brodie, Jean P.; Johnson, Benjamin D.; Glaccum, William; Villaume, Alexa; Cuillandre, Jean-Charles; Gwyn, Stephen; Krick, Jessica; Lasker, Ronald; Martín-Navarro, Ignacio; Martinez-Delgado, David; van Dokkum, Pieter

    2018-05-01

    We present observational constraints on the stellar populations of two ultra-diffuse galaxies (UDGs) using optical through near-infrared (NIR) spectral energy distribution (SED) fitting. Our analysis is enabled by new Spitzer-IRAC 3.6 and 4.5 μm imaging, archival optical imaging, and the prospector fully Bayesian SED fitting framework. Our sample contains one field UDG (DGSAT I), one Virgo cluster UDG (VCC 1287), and one Virgo cluster dwarf elliptical for comparison (VCC 1122). We find that the optical–NIR colors of the three galaxies are significantly different from each other. We infer that VCC 1287 has an old (≳7.7 Gyr) and surprisingly metal-poor ([Z/Z ⊙] ≲ ‑1.0) stellar population, even after marginalizing over uncertainties on diffuse interstellar dust. In contrast, the field UDG DGSAT I shows evidence of being younger than the Virgo UDG, with an extended star formation history and an age posterior extending down to ∼3 Gyr. The stellar metallicity of DGSAT I is sub-solar but higher than that of the Virgo UDG, with [Z/{Z}ȯ ]=-{0.63}-0.62+0.35; in the case of exactly zero diffuse interstellar dust, DGSAT I may even have solar metallicity. With VCC 1287 and several Coma UDGs, a general picture is emerging where cluster UDGs may be “failed” galaxies, but the field UDG DGSAT I seems more consistent with a stellar feedback-induced expansion scenario. In the future, our approach can be applied to a large and diverse sample of UDGs down to faint surface brightness limits, with the goal of constraining their stellar ages, stellar metallicities, and circumstellar and diffuse interstellar dust content.

  6. A PETAL OF THE SUNFLOWER: PHOTOMETRY OF THE STELLAR TIDAL STREAM IN THE HALO OF MESSIER 63 (NGC 5055)

    International Nuclear Information System (INIS)

    Chonis, Taylor S.; Martínez-Delgado, David; Gabany, R. Jay; Majewski, Steven R.; Hill, Gary J.; Gralak, Ray; Trujillo, Ignacio

    2011-01-01

    We present deep surface photometry of a very faint, giant arc-loop feature in the halo of the nearby spiral galaxy NGC 5055 (M63) that is consistent with being a part of a stellar stream resulting from the disruption of a dwarf satellite galaxy. This faint feature was first detected in early photographic studies by van der Kruit; more recently, in the study of Martínez-Delgado and as presented in this work, from the loop has been realized to be the result of a recent minor merger through evidence obtained by wide-field, deep images taken with a telescope of only 0.16 m aperture. The stellar stream is clearly confirmed in additional deep images taken with the 0.5 m telescope of the BlackBird Remote Observatory and the 0.8 m telescope of the McDonald Observatory. This low surface brightness (μ R ≈ 26 mag arcsec –2 ) arc-like structure around the disk of the galaxy extends 14.'0 (∼29 kpc projected) from its center, with a projected width of 1.'6 (∼3.3 kpc). The stream's morphology is consistent with that of the visible part of a giant, 'great-circle' type stellar stream originating from the recent accretion of a ∼10 8 M ☉ dwarf satellite in the last few Gyr. The progenitor satellite's current position and final fate are not conclusive from our data. The color of the stream's stars is consistent with dwarfs in the Local Group and is similar to the outer faint regions of M63's disk and stellar halo. From our photometric study, we detect other low surface brightness 'plumes'; some of these may be extended spiral features related to the galaxy's complex spiral structure, and others may be tidal debris associated with the disruption of the galaxy's outer stellar disk as a result of the accretion event. We are able to differentiate between features related to the tidal stream and faint, blue extended features in the outskirts of the galaxy's disk previously detected by the Galaxy Evolution Explorer satellite. With its highly warped H I gaseous disk (∼20

  7. Stellar mass estimation based on IRAC photometry for Spitzer SWIRE-field galaxies

    International Nuclear Information System (INIS)

    Zhu Yinan; Wu Hong; Li Haining; Cao Chen

    2010-01-01

    We analyze the feasibility of estimating the stellar mass of galaxies by mid-infrared luminosities based on a large sample of galaxies cross-identified from Spitzer SWIRE fields and the SDSS spectrographic survey. We derived the formulae to calculate the stellar mass by using IRAC 3.6 μm and 4.5 μm luminosities. The mass-to-luminosity ratios of IRAC 3.6 μm and 4.5 μm luminosities are more sensitive to the star formation history of galaxies than to other factors, such as the intrinsic extinction, metallicity and star formation rate. To remove the effect of star formation history, we used g - r color to recalibrate the formulae and obtain a better result. Researchers must be more careful when estimating the stellar mass of low metallicity galaxies using our formulae. Due to the emission from dust heated by the hottest young stars, luminous infrared galaxies present higher IRAC 4.5 μm luminosities compared to IRAC 3.6 μm luminosities. For most of type-II AGNs, the nuclear activity cannot enhance 3.6 μm and 4.5 μm luminosities compared with normal galaxies. Star formation in our AGN-hosting galaxies is also very weak, almost all of which are early-type galaxies.

  8. Ultraviolet photometry from the Orbiting Astronomical Observatory. XXXII - An atlas of ultraviolet stellar spectra

    Science.gov (United States)

    Code, A. D.; Meade, M. R.

    1979-01-01

    Ultraviolet stellar fluxes are presented in graphs and tables for 164 bright stars in the spectral region from 1200 to 3600 A. The spectra represent a subset of OAO 2 spectrometer data on file at the National Space Science Data Center. The monochromatic flux is given in units of erg per (sq cm-s-A) with a spectral resolution of about 22 A in the region from 3600 to 1850 A and of approximately 12 A in the region from 1850 to 1160 A.

  9. CAPELLA: Software for stellar photometry in dense fields with an irregular background

    Science.gov (United States)

    Debray, B.; Llebaria, A.; Dubout-Crillon, R.; Petit, M.

    1994-01-01

    We describe CAPELLA, a photometric reduction package developed top automatically process images of very crowded stellar fields with an irregular background. Detection is performed by the use of a derivative filter (the laplacian of a gaussian), the measuring of position and flux of the stars uses a profile fitting technique. The Point Spread Function (PSF) is empirical. The traditional multiparmetric non-linear fit is replaced by a set of individual linear fits. The determination of the background, the detection, the definition of the PSF and the basics of the methods are successively addressed in details. The iterative procedure as well as some aspects of the sampling problem are also discussed. Precision tests, performances in uncrowded and crowded fields are given CAPELLA has been used to process crowded stellar fields obtained with different detectors such as electronographic cameras, CCD's photographic films coupled to image intensifiers. It has been applied successfully in the extreme cases of close associations of the galaxy M33, of the composite Wolf-Rayet Brey 73 in the Large Magellanic Cloud (LMC) and of the central parts of globular clusters as 47 TUC and M15.

  10. Ultraviolet photometry from the orbiting astronomical observatory. XVI - The stellar Lyman-alpha absorption line

    Science.gov (United States)

    Savage, B. D.; Panek, R. J.

    1974-01-01

    The stellar Lyman-alpha line at 1216 A was observed in 29 lightly reddened stars of spectral type B2.5 to B9 by a far-UV spectrophotometer on OAO-2. The equivalent widths obtained range from 15 A at type B2.5 to 65 A at type B8; in the late-B stars, the L-alpha line removes 2 to 3% of the total stellar flux. In this sampling, the strength of the L-alpha line correlates well with measures of the Balmer discontinuity and Balmer line strengths; luminosity classification does not seem to affect the line strength. The observed line widths also agree with the predictions of Mihala's grid of non-LTE model atmospheres. In some cases, the L-alpha line influences the interstellar column densities reported in the interstellar OAO-2 L-alpha survey. Hence, these data toward lightly reddened B2 and B1.5 stars should be regarded as upper limits only.

  11. M13 multiple stellar populations seen with the eyes of Strömgren photometry

    Science.gov (United States)

    Savino, A.; Massari, D.; Bragaglia, A.; Dalessandro, E.; Tolstoy, E.

    2018-03-01

    We present a photometric study of M13 multiple stellar populations over a wide field of view, covering approximately 6.5 half-light radii, using archival Isaac Newton Telescope observations to build an accurate multiband Strömgren catalogue. The use of the Strömgren index cy permits us to separate the multiple populations of M13 on the basis of their position on the red giant branch. The comparison with medium and high resolution spectroscopic analysis confirms the robustness of our selection criterion. To determine the radial distribution of stars in M13, we complemented our data set with Hubble Space Telescope observations of the cluster core, to compensate for the effect of incompleteness affecting the most crowded regions. From the analysis of the radial distributions, we do not find any significant evidence of spatial segregation. Some residuals may be present in the external regions where we observe only a small number of stars. This finding is compatible with the short dynamical time-scale of M13 and represents, to date, one of the few examples of fully spatially mixed multiple populations in a massive globular cluster.

  12. Galactic globular cluster NGC 6752 and its stellar population as inferred from multicolor photometry

    Energy Technology Data Exchange (ETDEWEB)

    Kravtsov, Valery [Instituto de Astronomía, Universidad Católica del Norte, Avenida Angamos 0610, Casilla 1280, Antofagasta (Chile); Alcaíno, Gonzalo [Isaac Newton Institute of Chile, Ministerio de Educación de Chile, Casilla 8-9, Correo 9, Santiago (Chile); Marconi, Gianni; Alvarado, Franklin, E-mail: vkravtsov@ucn.cl, E-mail: inewton@terra.cl, E-mail: falvarad@eso.org, E-mail: gmarconi@eso.org [ESO-European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile)

    2014-03-01

    This paper is devoted to photometric study of the Galactic globular cluster (GGC) NGC 6752 in UBVI, focusing on the multiplicity of its stellar population. We emphasize that our U passband is (1) narrower than the standard one due to its smaller extension blueward and (2) redshifted by ∼300 Å relative to its counterparts, such as the HST F336W filter. Accordingly, both the spectral features encompassed by it and photometric effects of the multiplicity revealed in our study are somewhat different than in recent studies of NGC 6752. Main sequence stars bluer in U – B are less centrally concentrated, as red giants are. We find a statistically significant increasing luminosity of the red giant branch (RGB) bump of ΔU ≈ 0.2 mag toward the cluster outskirts with no so obvious effect in V. The photometric results are correlated with spectroscopic data: the bluer RGB stars in U – B have lower nitrogen abundances. We draw attention to a larger width of the RGB than the blue horizontal branch (BHB) in U – B. This seems to agree with the effects predicted to be caused by molecular bands produced by nitrogen-containing molecules. We find that brighter BHB stars, especially the brightest ones, are more centrally concentrated. This implies that red giants that are redder in U – B, i.e., more nitrogen enriched and centrally concentrated, are the main progenitors of the brighter BHB stars. However, such a progenitor-progeny relationship disagrees with theoretical predictions and with the results on the elemental abundances in horizontal branch stars. We isolated the asymptotic giant branch clump and estimated the parameter ΔV{sub ZAHB}{sup clump} = 0.98 ± 0.12.

  13. The Masses and Stellar Content of Nuclei in Early-Type Galaxies from Multi-Band Photometry and Spectroscopy

    Science.gov (United States)

    Spengler, Chelsea; Côté, Patrick; Roediger, Joel; Ferrarese, Laura; Sánchez-Janssen, Rubén; Toloba, Elisa; Liu, Yiqing; Guhathakurta, Puragra; Cuillandre, Jean-Charles; Gwyn, Stephen; Zirm, Andrew; Muñoz, Roberto; Puzia, Thomas; Lançon, Ariane; Peng, Eric; Mei, Simona; Powalka, Mathieu

    2018-01-01

    It is now established that most, if not all, massive galaxies host central supermassive black holes (SMBHs), and that these SMBHs are linked to the growth their host galaxies as shown by several scaling relations. Within the last couple of decades, it has become apparent that most lower-mass galaxies without obvious SMBHs nevertheless contain some sort of central massive object in the form of compact stellar nuclei that also follow identical (or similar) scaling relations. These nuclei are challenging to study given their small sizes and relatively faint magnitudes, but understanding their origins and relationship to their hosts is critical to gaining a more complete picture of galaxy evolution. To that end, we highlight selected results from an analysis of 39 nuclei and their early-type hosts in the Virgo Cluster using ten broadband filters: F300W, F475W, F850LP, F160W, u*griz, and Ks. We estimate masses, metallicities and ages using simple stellar population (SSP) models. For 19 nuclei, we compare to SSP parameters derived from Keck and Gemini spectra and find reasonable agreement between the photometric and spectroscopic metallicity: the RMS scatter is 0.3 dex. We reproduce the nucleus-galaxy mass fraction of 0.33 ± 0.08% for galaxy stellar masses 108.4-1010.3 M⊙ with a typical precision of ~35% for the nuclei masses. Based on available model predictions, there is no single preferred formation scenario for nuclei, suggesting that nuclei are formed stochastically through a mix of processes. Nuclei metallicities are statistically identical to those of their hosts, appearing 0.07 ± 0.3 dex more metal-rich on average — although, omitting galaxies with unusual origins (i.e., compact ellipticals), nuclei are 0.20 ± 0.28 dex more metal-rich. We find no clear age difference between nuclei and their galaxies, with nuclei displaying a broad range of ages. Interestingly, we find that the most massive nuclei may be flatter and more closely aligned with the semi

  14. New BVI C photometry of low-mass pleiades stars: Exploring the effects of rotation on broadband colors

    International Nuclear Information System (INIS)

    Kamai, Brittany L.; Stassun, Keivan G.; Vrba, Frederick J.; Stauffer, John R.

    2014-01-01

    We present new BVI C photometry for 350 Pleiades proper motion members with 9 < V ≲ 17. Importantly, our new catalog includes a large number of K- and early M-type stars, roughly doubling the number of low-mass stars with well-calibrated Johnson/Cousins photometry in this benchmark cluster. We combine our new photometry with existing photometry from the literature to define a purely empirical isochrone at Pleiades age (≈100 Myr) extending from V = 9 to 17. We use the empirical isochrone to identify 48 new probable binaries and 14 likely nonmembers. The photometrically identified single stars are compared against their expected positions in the color-magnitude diagram (CMD). At 100 Myr, the mid K and early M stars are predicted to lie above the zero-age main sequence (ZAMS) having not yet reached the ZAMS. We find in the B – V versus V CMD that mid K and early M dwarfs are instead displaced below (or blueward of) the ZAMS. Using the stars' previously reported rotation periods, we find a highly statistically significant correlation between rotation period and CMD displacement, in the sense that the more rapidly rotating stars have the largest displacements in the B – V CMD.

  15. Optical photometry of galaxies

    International Nuclear Information System (INIS)

    Comte, G.

    1981-01-01

    The present status of the optical and near-infrared photometry of galaxies is reviewed. Part I introduces to the goals and general methods of both photographic surface photometry and integrated multicolor aperture photoelectric photometry for extended stellar systems, with a summary of the necessary corrections to the observed magnitudes and colors. Part II (surface photometry) summarizes recent results on the empirical luminosity laws for spheroidal systems and the separation of components in disk-plus-bulge systems. Part III (color problems) discusses integrated color effects (color and gas content, color-absolute magnitude relation for early-type systems, colors of interacting galaxies) and color gradient across spheroidal and disk galaxies. In part IV are summarized some constraints on the luminosity function of the stellar population in spheroidal systems given by narrow-band photometry [fr

  16. High-resolution imaging and crowded-field photometry of the stellar populations in the cores of the Globular Clusters M15 and M4

    Science.gov (United States)

    Butler, R. F.

    1999-02-01

    This thesis presents work performed at the Department of Physics, University College Galway from 1992 to 1997. It is concerned with ground- and space-based high-resolution optical imaging of globular cluster cores, and the subsequent application of image-restoration and crowded-field photometry techniques; thus we may gain an improved understanding of the nature of their stellar populations, by either monitoring their temporal behaviour over moderate periods for the first time, or by obtaining a more precise "static" picture than was hitherto possible. These goals can be achieved by the development of innovative instrumentation and data analysis techniques. The particularly unique aspect of this work is that it deals with the first application of two-dimensional photon-counting detectors (2D-PCDs) and post-exposure image sharpening (PEIS) for crowded-field photometry. The thesis starts by introducing some basic concepts and characteristics of globular clusters and the diverse stellar species which they contain, in particular those predicted to have formed as a result of dynamical processes in the cluster cores, and those which exhibit variability in emission over time. It then reviews the fields of high-resolution imaging through the turbulent atmosphere & image deconvolution, optical stellar photometry, and Hubble Space Telescope observing and data reduction, each concluded with a description of the systems used in the work reported here (for the HST chapter this involves photometry of WFPC2 (Wide Field & Planetary Camera 2) observations of M15 (NGC 7078) released into the archives in 1995). The core of the thesis begins with a review of the observations to date of the objects with which this thesis is chiefly concerned, M15 and M4 (NGC 6121). In the following sections we describe the observations of these clusters which were made using the TRIFFID camera between 1992 and 1995, the image sharpening and calibration steps performed, and the photometric techniques

  17. OTELO SURVEY: DEEP BVRI BROADBAND PHOTOMETRY OF THE GROTH STRIP. II. OPTICAL PROPERTIES OF X-RAY EMITTERS

    International Nuclear Information System (INIS)

    Povic, M.; Perez GarcIa, A. M.; Bongiovanni, A.; Castaneda, H.; Lorenzo, M. Fernandez; Lara-Lopez, M. A.; Sanchez-Portal, M.; Cepa, J.; Alfaro, E.; Gallego, J.; Gonzalez-Serrano, J. I.; Gonzalez, J. J.

    2009-01-01

    The Groth field is one of the sky regions that will be targeted by the OSIRIS Tunable Filter Emission Line Object survey in the optical 820 nm and 920 nm atmospheric windows. In the present paper, public Chandra X-ray data with total exposure time of 200 ks are analyzed and combined with optical broadband data of the Groth field, in order to study a set of optical structural parameters of the X-ray emitters and its relation with X-ray properties. To this aim, we processed the raw, public X-ray data using the Chandra Interactive Analysis of Observations, and determined and analyzed different structural parameters, in order to produce a morphological classification of X-ray sources. We present the morphology of 340 X-ray emitters with optical counterpart detected. Objects have been classified by X-ray type using a diagnostic diagram relating X-ray-to-optical ratio (X/O) to hardness ratio. We did not find any clear correlation between X-ray and morphological types. We analyzed the angular clustering of X-ray sources with optical counterpart using two-point correlation functions. A significant positive angular clustering was obtained from a preliminary analysis of four subsamples of the X-ray sources catalog. The clustering signal of the optically extended counterparts is similar to that of strongly clustered populations like red and very red galaxies, suggesting that the environment plays an important role in active galactic nuclei phenomena. Finally, we combined optical structural parameters with other X-ray and optical properties, and we confirmed an anticorrelation between the X/O ratio and the Abraham concentration index, which might suggest that early-type galaxies have lower Eddington rates than those of late-type galaxies.

  18. 3D-HST WFC3-SELECTED PHOTOMETRIC CATALOGS IN THE FIVE CANDELS/3D-HST FIELDS: PHOTOMETRY, PHOTOMETRIC REDSHIFTS, AND STELLAR MASSES

    Energy Technology Data Exchange (ETDEWEB)

    Skelton, Rosalind E. [South African Astronomical Observatory, PO Box 9, Observatory, Cape Town 7935 (South Africa); Whitaker, Katherine E. [Astrophysics Science Division, Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Momcheva, Ivelina G.; Van Dokkum, Pieter G.; Bezanson, Rachel; Leja, Joel; Nelson, Erica J.; Oesch, Pascal [Department of Astronomy, Yale University, 260 Whitney Avenue, New Haven, CT 06511 (United States); Brammer, Gabriel B. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Labbé, Ivo; Franx, Marijn; Fumagalli, Mattia [Leiden Observatory, Leiden University, Leiden (Netherlands); Van der Wel, Arjen; Da Cunha, Elisabete; Maseda, Michael V. [Max Planck Institute for Astronomy (MPIA), Königstuhl 17, D-69117, Heidelberg (Germany); Förster Schreiber, Natascha [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Kriek, Mariska [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Lundgren, Britt F. [Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706 (United States); Magee, Daniel [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA (United States); Marchesini, Danilo, E-mail: ros@saao.ac.za [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); and others

    2014-10-01

    The 3D-HST and CANDELS programs have provided WFC3 and ACS spectroscopy and photometry over ≈900 arcmin{sup 2} in five fields: AEGIS, COSMOS, GOODS-North, GOODS-South, and the UKIDSS UDS field. All these fields have a wealth of publicly available imaging data sets in addition to the Hubble Space Telescope (HST) data, which makes it possible to construct the spectral energy distributions (SEDs) of objects over a wide wavelength range. In this paper we describe a photometric analysis of the CANDELS and 3D-HST HST imaging and the ancillary imaging data at wavelengths 0.3-8 μm. Objects were selected in the WFC3 near-IR bands, and their SEDs were determined by carefully taking the effects of the point-spread function in each observation into account. A total of 147 distinct imaging data sets were used in the analysis. The photometry is made available in the form of six catalogs: one for each field, as well as a master catalog containing all objects in the entire survey. We also provide derived data products: photometric redshifts, determined with the EAZY code, and stellar population parameters determined with the FAST code. We make all the imaging data that were used in the analysis available, including our reductions of the WFC3 imaging in all five fields. 3D-HST is a spectroscopic survey with the WFC3 and ACS grisms, and the photometric catalogs presented here constitute a necessary first step in the analysis of these grism data. All the data presented in this paper are available through the 3D-HST Web site (http://3dhst.research.yale.edu)

  19. 3D-HST WFC3-selected Photometric Catalogs in the Five CANDELS/3D-HST Fields: Photometry, Photometric Redshifts, and Stellar Masses

    Science.gov (United States)

    Skelton, Rosalind E.; Whitaker, Katherine E.; Momcheva, Ivelina G.; Brammer, Gabriel B.; van Dokkum, Pieter G.; Labbé, Ivo; Franx, Marijn; van der Wel, Arjen; Bezanson, Rachel; Da Cunha, Elisabete; Fumagalli, Mattia; Förster Schreiber, Natascha; Kriek, Mariska; Leja, Joel; Lundgren, Britt F.; Magee, Daniel; Marchesini, Danilo; Maseda, Michael V.; Nelson, Erica J.; Oesch, Pascal; Pacifici, Camilla; Patel, Shannon G.; Price, Sedona; Rix, Hans-Walter; Tal, Tomer; Wake, David A.; Wuyts, Stijn

    2014-10-01

    The 3D-HST and CANDELS programs have provided WFC3 and ACS spectroscopy and photometry over ≈900 arcmin2 in five fields: AEGIS, COSMOS, GOODS-North, GOODS-South, and the UKIDSS UDS field. All these fields have a wealth of publicly available imaging data sets in addition to the Hubble Space Telescope (HST) data, which makes it possible to construct the spectral energy distributions (SEDs) of objects over a wide wavelength range. In this paper we describe a photometric analysis of the CANDELS and 3D-HST HST imaging and the ancillary imaging data at wavelengths 0.3-8 μm. Objects were selected in the WFC3 near-IR bands, and their SEDs were determined by carefully taking the effects of the point-spread function in each observation into account. A total of 147 distinct imaging data sets were used in the analysis. The photometry is made available in the form of six catalogs: one for each field, as well as a master catalog containing all objects in the entire survey. We also provide derived data products: photometric redshifts, determined with the EAZY code, and stellar population parameters determined with the FAST code. We make all the imaging data that were used in the analysis available, including our reductions of the WFC3 imaging in all five fields. 3D-HST is a spectroscopic survey with the WFC3 and ACS grisms, and the photometric catalogs presented here constitute a necessary first step in the analysis of these grism data. All the data presented in this paper are available through the 3D-HST Web site (http://3dhst.research.yale.edu).

  20. 3D-HST WFC3-SELECTED PHOTOMETRIC CATALOGS IN THE FIVE CANDELS/3D-HST FIELDS: PHOTOMETRY, PHOTOMETRIC REDSHIFTS, AND STELLAR MASSES

    International Nuclear Information System (INIS)

    Skelton, Rosalind E.; Whitaker, Katherine E.; Momcheva, Ivelina G.; Van Dokkum, Pieter G.; Bezanson, Rachel; Leja, Joel; Nelson, Erica J.; Oesch, Pascal; Brammer, Gabriel B.; Labbé, Ivo; Franx, Marijn; Fumagalli, Mattia; Van der Wel, Arjen; Da Cunha, Elisabete; Maseda, Michael V.; Förster Schreiber, Natascha; Kriek, Mariska; Lundgren, Britt F.; Magee, Daniel; Marchesini, Danilo

    2014-01-01

    The 3D-HST and CANDELS programs have provided WFC3 and ACS spectroscopy and photometry over ≈900 arcmin 2 in five fields: AEGIS, COSMOS, GOODS-North, GOODS-South, and the UKIDSS UDS field. All these fields have a wealth of publicly available imaging data sets in addition to the Hubble Space Telescope (HST) data, which makes it possible to construct the spectral energy distributions (SEDs) of objects over a wide wavelength range. In this paper we describe a photometric analysis of the CANDELS and 3D-HST HST imaging and the ancillary imaging data at wavelengths 0.3-8 μm. Objects were selected in the WFC3 near-IR bands, and their SEDs were determined by carefully taking the effects of the point-spread function in each observation into account. A total of 147 distinct imaging data sets were used in the analysis. The photometry is made available in the form of six catalogs: one for each field, as well as a master catalog containing all objects in the entire survey. We also provide derived data products: photometric redshifts, determined with the EAZY code, and stellar population parameters determined with the FAST code. We make all the imaging data that were used in the analysis available, including our reductions of the WFC3 imaging in all five fields. 3D-HST is a spectroscopic survey with the WFC3 and ACS grisms, and the photometric catalogs presented here constitute a necessary first step in the analysis of these grism data. All the data presented in this paper are available through the 3D-HST Web site (http://3dhst.research.yale.edu)

  1. THE HIGH A{sub V} Quasar Survey: Reddened Quasi-Stellar Objects selected from optical/near-infrared photometry. II

    Energy Technology Data Exchange (ETDEWEB)

    Krogager, J.-K.; Fynbo, J. P. U.; Vestergaard, M. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø (Denmark); Geier, S. [Instituto de Astrofísica de Canarias (IAC), E-38205 La Laguna, Tenerife (Spain); Venemans, B. P. [Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Ledoux, C. [European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19 (Chile); Møller, P. [European Southern Observatory, Karl-Schwarzschildstrasse 2, D-85748 Garching bei München (Germany); Noterdaeme, P. [Institut d’Astrophysique de Paris, CNRS-UPMC, UMR7095, 98bis bd Arago, F-75014 Paris (France); Kangas, T.; Pursimo, T.; Smirnova, O. [Nordic Optical Telescope, Apartado 474, E-38700 Santa Cruz de La Palma (Spain); Saturni, F. G. [Tuorla Observatory, Department of Physics and Astronomy, University of Turku, Väisäläntie 20, 21500 Piikkiö (Finland)

    2015-03-15

    Quasi-stellar objects (QSOs) whose spectral energy distributions (SEDs) are reddened by dust either in their host galaxies or in intervening absorber galaxies are to a large degree missed by optical color selection criteria like the ones used by the Sloan Digital Sky Survey (SDSS). To overcome this bias against red QSOs, we employ a combined optical and near-infrared (near-IR) color selection. In this paper, we present a spectroscopic follow-up campaign of a sample of red candidate QSOs which were selected from the SDSS and the UKIRT Infrared Deep Sky Survey (UKIDSS). The spectroscopic data and SDSS/UKIDSS photometry are supplemented by mid-infrared photometry from the Wide-field Infrared Survey Explorer. In our sample of 159 candidates, 154 (97%) are confirmed to be QSOs. We use a statistical algorithm to identify sightlines with plausible intervening absorption systems and identify nine such cases assuming dust in the absorber similar to Large Magellanic Cloud sightlines. We find absorption systems toward 30 QSOs, 2 of which are consistent with the best-fit absorber redshift from the statistical modeling. Furthermore, we observe a broad range in SED properties of the QSOs as probed by the rest-frame 2 μm flux. We find QSOs with a strong excess as well as QSOs with a large deficit at rest-frame 2 μm relative to a QSO template. Potential solutions to these discrepancies are discussed. Overall, our study demonstrates the high efficiency of the optical/near-IR selection of red QSOs.

  2. VIRIAL BLACK HOLE MASS ESTIMATES FOR 280,000 AGNs FROM THE SDSS BROADBAND PHOTOMETRY AND SINGLE-EPOCH SPECTRA

    Energy Technology Data Exchange (ETDEWEB)

    Kozłowski, Szymon, E-mail: simkoz@astrouw.edu.pl [Warsaw University Observatory, Al. Ujazdowskie, 4 00-478 Warszawa (Poland)

    2017-01-01

    We use the Sloan Digital Sky Survey (SDSS) Quasar Data Release 12 (DR12Q), containing nearly 300,000 active galactic nuclei (AGNs), to calculate the monochromatic luminosities at 5100, 3000, and 1350 Å, derived from the broadband extinction-corrected SDSS magnitudes. After matching these sources to their counterparts from the SDSS Quasar Data Release 7 (DR7Q), we find very high correlations between our luminosities and DR7Q spectra-based luminosities with minute mean offsets (∼0.01 dex) and dispersions of differences of 0.11, 0.10, and 0.12 dex, respectively, across a luminosity range of 2.5 dex. We then estimate the black hole (BH) masses of the AGNs using the broad line region radius–disk luminosity relations and the FWHM of the Mg ii and C iv emission lines, to provide a catalog of 283,033 virial BH mass estimates (132,451 for Mg ii, 213,071 for C iv, and 62,489 for both) along with the estimates of the bolometric luminosity and Eddington ratio for 0.1 <  z  < 5.5 and for roughly a quarter of the sky covered by SDSS. The BH mass estimates from Mg ii turned out to be closely matched to the ones from DR7Q with a dispersion of differences of 0.34 dex across a BH mass range of ∼2 dex. We uncovered a bias in the derived C iv FWHMs from DR12Q as compared to DR7Q, which we correct empirically. The C iv BH mass estimates should be used with caution because the C iv line is known to cause problems in the estimation of BH mass from single-epoch spectra. Finally, after the FWHM correction, the AGN BH mass estimates from C iv closely match the DR7Q ones (with a dispersion of 0.28 dex), and more importantly the Mg ii and C iv BH masses agree internally with a mean offset of 0.07 dex and a dispersion of 0.39 dex.

  3. Multiple stellar populations of globular clusters from homogeneous Ca-Cn photometry. II. M5 (NGC 5904) and a new filter system

    OpenAIRE

    Lee, Jae-Woo

    2017-01-01

    Using our ingeniously designed new filter systems, we investigate the multiple stellar populations of the RGB and AGB in the GC M5. Our results are the following. (1) Our cn_jwl index accurately traces the nitrogen abundances in M5, while other color indices fail to do so. (2) We find bimodal CN distributions both in the RGB and the AGB sequences, with the number ratios between the CN-weak (CN-w) and the CN-strong (CN-s) of n(CN-w):n(CN-s) = 29:71(+/- 2) and 21:79(+/- 7), respectively. (3) We...

  4. The Effect of Broadband Soft X-Rays in SO2-Containing Ices: Implications on the Photochemistry of Ices toward Young Stellar Objects

    Science.gov (United States)

    Pilling, S.; Bergantini, A.

    2015-10-01

    We investigate the effects produced mainly by broadband soft X-rays up to 2 keV (plus fast (˜keV) photoelectrons and low-energy (˜eV) induced secondary electrons) in the ice mixtures containing H2O:CO2:NH3:SO2 (10:1:1:1) at two different temperatures (50 and 90 K). The experiments are an attempt to simulate the photochemical processes induced by energetic photons in SO2-containing ices present in cold environments in the ices surrounding young stellar objects (YSO) and in molecular clouds in the vicinity of star-forming regions, which are largely illuminated by soft X-rays. The measurements were performed using a high-vacuum portable chamber from the Laboratório de Astroquímica e Astrobiologia (LASA/UNIVAP) coupled to the spherical grating monochromator beamline at the Brazilian Synchrotron Light Source (LNLS) in Campinas, Brazil. In situ analyses were performed by a Fourier transform infrared spectrometer. Sample processing revealed the formation of several organic molecules, including nitriles, acids, and other compounds such as H2O2, H3O+, SO3, CO, and OCN-. The dissociation cross section of parental species was on the order of (2-7) × 10-18 cm2. The ice temperature does not seem to affect the stability of SO2 in the presence of X-rays. Formation cross sections of new species produced were also determined. Molecular half-lives at ices toward YSOs due to the presence of incoming soft X-rays were estimated. The low values obtained employing two different models of the radiation field of YSOs (TW Hydra and typical T-Tauri star) reinforce that soft X-rays are indeed a very efficient source of molecular dissociation in such environments.

  5. THE EFFECT OF BROADBAND SOFT X-RAYS IN SO2-CONTAINING ICES: IMPLICATIONS ON THE PHOTOCHEMISTRY OF ICES TOWARD YOUNG STELLAR OBJECTS

    International Nuclear Information System (INIS)

    Pilling, S.; Bergantini, A.

    2015-01-01

    We investigate the effects produced mainly by broadband soft X-rays up to 2 keV (plus fast (∼keV) photoelectrons and low-energy (∼eV) induced secondary electrons) in the ice mixtures containing H 2 O:CO 2 :NH 3 :SO 2 (10:1:1:1) at two different temperatures (50 and 90 K). The experiments are an attempt to simulate the photochemical processes induced by energetic photons in SO 2 -containing ices present in cold environments in the ices surrounding young stellar objects (YSO) and in molecular clouds in the vicinity of star-forming regions, which are largely illuminated by soft X-rays. The measurements were performed using a high-vacuum portable chamber from the Laboratório de Astroquímica e Astrobiologia (LASA/UNIVAP) coupled to the spherical grating monochromator beamline at the Brazilian Synchrotron Light Source (LNLS) in Campinas, Brazil. In situ analyses were performed by a Fourier transform infrared spectrometer. Sample processing revealed the formation of several organic molecules, including nitriles, acids, and other compounds such as H 2 O 2 , H 3 O + , SO 3 , CO, and OCN − . The dissociation cross section of parental species was on the order of (2–7) × 10 −18 cm 2 . The ice temperature does not seem to affect the stability of SO 2 in the presence of X-rays. Formation cross sections of new species  produced were also determined. Molecular half-lives at ices toward YSOs due to the presence of incoming soft X-rays were estimated. The low values obtained employing two different models of the radiation field of YSOs (TW Hydra and typical T-Tauri star) reinforce that soft X-rays are indeed a very efficient source of molecular dissociation in such environments

  6. SURFACE PHOTOMETRY OF LOW SURFACE BRIGHTNESS GALAXIES

    NARCIS (Netherlands)

    DEBLOK, WJG; VANDERHULST, JM; BOTHUN, GD

    1995-01-01

    Low surface brightness (LSB) galaxies are galaxies dominated by an exponential disc whose central surface brightness is much fainter than the value of mu(B)(0) = 21.65 +/- 0.30 mag arcsec(-2) found by Freeman. In this paper we present broadband photometry of a sample of 21 late-type LSB galaxies.

  7. Multiple Stellar Populations of Globular Clusters from Homogeneous Ca-CN Photometry. II. M5 (NGC 5904) and a New Filter System

    Science.gov (United States)

    Lee, Jae-Woo

    2017-07-01

    Using our ingeniously designed new filter systems, we investigate multiple stellar populations of the red giant branch (RGB) and the asymptotic giant branch (AGB) in the globular cluster (GC) M5. Our results are the following. (1) Our {{cn}}{JWL} index accurately traces nitrogen abundances in M5, while other color indices fail to do so. (2) We find bimodal CN distributions in both RGB and AGB sequences, with number ratios between CN-weak (CN-w) and CN-strong (CN-s) of n(CN-w):n(CN-s) = 29:71 (±2) and 21:79 (±7), respectively. (3) We also find a bimodal photometric [N/Fe] distribution for M5 RGB stars. (4) Our {{cn}}{JWL}-[O/Fe] and {{cn}}{JWL}-[Na/Fe] relations show clear discontinuities between the two RGB populations. (5) Although small, the RGB bump of CN-s is slightly brighter, {{Δ }}{V}{bump} = 0.07 ± 0.04 mag. If real, the difference in the helium abundance becomes {{Δ }}Y = 0.028 ± 0.016, in the sense that CN-s is more helium enhanced. (6) Very similar radial but different spatial distributions with comparable center positions are found for the two RGB populations. The CN-s RGB and AGB stars are more elongated along the NW-SE direction. (7) The CN-s population shows a substantial net projected rotation, while that of the CN-w population is nil. (8) Our results confirm the deficiency of CN-w AGB stars previously noted by others. We show that it is most likely due to stochastic truncation in the outer part of the cluster. Finally, we discuss the formation scenario of M5. Based on observations made with the Cerro Tololo Inter-American Observatory (CTIO) 1 m telescope, which is operated by the SMARTS consortium.

  8. HFF-DeepSpace Photometric Catalogs of the 12 Hubble Frontier Fields, Clusters, and Parallels: Photometry, Photometric Redshifts, and Stellar Masses

    Science.gov (United States)

    Shipley, Heath V.; Lange-Vagle, Daniel; Marchesini, Danilo; Brammer, Gabriel B.; Ferrarese, Laura; Stefanon, Mauro; Kado-Fong, Erin; Whitaker, Katherine E.; Oesch, Pascal A.; Feinstein, Adina D.; Labbé, Ivo; Lundgren, Britt; Martis, Nicholas; Muzzin, Adam; Nedkova, Kalina; Skelton, Rosalind; van der Wel, Arjen

    2018-03-01

    We present Hubble multi-wavelength photometric catalogs, including (up to) 17 filters with the Advanced Camera for Surveys and Wide Field Camera 3 from the ultra-violet to near-infrared for the Hubble Frontier Fields and associated parallels. We have constructed homogeneous photometric catalogs for all six clusters and their parallels. To further expand these data catalogs, we have added ultra-deep K S -band imaging at 2.2 μm from the Very Large Telescope HAWK-I and Keck-I MOSFIRE instruments. We also add post-cryogenic Spitzer imaging at 3.6 and 4.5 μm with the Infrared Array Camera (IRAC), as well as archival IRAC 5.8 and 8.0 μm imaging when available. We introduce the public release of the multi-wavelength (0.2–8 μm) photometric catalogs, and we describe the unique steps applied for the construction of these catalogs. Particular emphasis is given to the source detection band, the contamination of light from the bright cluster galaxies (bCGs), and intra-cluster light (ICL). In addition to the photometric catalogs, we provide catalogs of photometric redshifts and stellar population properties. Furthermore, this includes all the images used in the construction of the catalogs, including the combined models of bCGs and ICL, the residual images, segmentation maps, and more. These catalogs are a robust data set of the Hubble Frontier Fields and will be an important aid in designing future surveys, as well as planning follow-up programs with current and future observatories to answer key questions remaining about first light, reionization, the assembly of galaxies, and many more topics, most notably by identifying high-redshift sources to target.

  9. THE EFFECT OF BROADBAND SOFT X-RAYS IN SO{sub 2}-CONTAINING ICES: IMPLICATIONS ON THE PHOTOCHEMISTRY OF ICES TOWARD YOUNG STELLAR OBJECTS

    Energy Technology Data Exchange (ETDEWEB)

    Pilling, S.; Bergantini, A., E-mail: sergiopilling@pq.cnpq.br [Universidade do Vale do Paraíba (UNIVAP), Laboratório de Astroquímica e Astrobiologia (LASA), São José dos Campos, SP (Brazil)

    2015-10-01

    We investigate the effects produced mainly by broadband soft X-rays up to 2 keV (plus fast (∼keV) photoelectrons and low-energy (∼eV) induced secondary electrons) in the ice mixtures containing H{sub 2}O:CO{sub 2}:NH{sub 3}:SO{sub 2} (10:1:1:1) at two different temperatures (50 and 90 K). The experiments are an attempt to simulate the photochemical processes induced by energetic photons in SO{sub 2}-containing ices present in cold environments in the ices surrounding young stellar objects (YSO) and in molecular clouds in the vicinity of star-forming regions, which are largely illuminated by soft X-rays. The measurements were performed using a high-vacuum portable chamber from the Laboratório de Astroquímica e Astrobiologia (LASA/UNIVAP) coupled to the spherical grating monochromator beamline at the Brazilian Synchrotron Light Source (LNLS) in Campinas, Brazil. In situ analyses were performed by a Fourier transform infrared spectrometer. Sample processing revealed the formation of several organic molecules, including nitriles, acids, and other compounds such as H{sub 2}O{sub 2}, H{sub 3}O{sup +}, SO{sub 3}, CO, and OCN{sup −}. The dissociation cross section of parental species was on the order of (2–7) × 10{sup −18} cm{sup 2}. The ice temperature does not seem to affect the stability of SO{sub 2} in the presence of X-rays. Formation cross sections of new species  produced were also determined. Molecular half-lives at ices toward YSOs due to the presence of incoming soft X-rays were estimated. The low values obtained employing two different models of the radiation field of YSOs (TW Hydra and typical T-Tauri star) reinforce that soft X-rays are indeed a very efficient source of molecular dissociation in such environments.

  10. Broadband Access

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Broadband Access. Worldwide market for broadband access $30 Billion! Over 200 million broadband subscribers worldwide! Various Competing Broadband access. Digital Subscriber line; Wireless; Optical Fiber.

  11. The galaxy population of Abell 1367: the stellar mass-metallicity relation

    Science.gov (United States)

    Mouhcine, M.; Kriwattanawong, W.; James, P. A.

    2011-04-01

    Using wide baseline broad-band photometry, we analyse the stellar population properties of a sample of 72 galaxies, spanning a wide range of stellar masses and morphological types, in the nearby spiral-rich and dynamically young galaxy cluster Abell 1367. The sample galaxies are distributed from the cluster centre out to approximately half the cluster Abell radius. The optical/near-infrared colours are compared with simple stellar population synthesis models from which the luminosity-weighted stellar population ages and metallicities are determined. The locus of the colours of elliptical galaxies traces a sequence of varying metallicity at a narrow range of luminosity-weighted stellar ages. Lenticular galaxies in the red sequence, however, exhibit a substantial spread of luminosity-weighted stellar metallicities and ages. For red-sequence lenticular galaxies and blue cloud galaxies, low-mass galaxies tend to be on average dominated by stellar populations of younger luminosity-weighted ages. Sample galaxies exhibit a strong correlation between integrated stellar mass and luminosity-weighted stellar metallicity. Galaxies with signs of morphological disturbance and ongoing star formation activity, tend to be underabundant with respect to passive galaxies in the red sequence of comparable stellar masses. We argue that this could be due to tidally driven gas flows towards the star-forming regions, carrying less enriched gas and diluting the pre-existing gas to produce younger stellar populations with lower metallicities than would be obtained prior to the interaction. Finally, we find no statistically significant evidence for changes in the luminosity-weighted ages and metallicities for either red-sequence or blue-cloud galaxies, at fixed stellar mass, with location within the cluster. We dedicate this work to the memory of our friend and colleague C. Moss who died suddenly recently.

  12. Deriving stellar parameters with the SME software package

    Science.gov (United States)

    Piskunov, N.

    2017-09-01

    Photometry and spectroscopy are complementary tools for deriving accurate stellar parameters. Here I present one of the popular packages for stellar spectroscopy called SME with the emphasis on the latest developments and error assessment for the derived parameters.

  13. Models for stellar flares

    International Nuclear Information System (INIS)

    Cram, L.E.; Woods, D.T.

    1982-01-01

    We study the response of certain spectral signatures of stellar flares (such as Balmer line profiles and the broad-band continuum) to changes in atmospheric structure which might result from physical processes akin to those thought to occur in solar flares. While each physical process does not have a unique signature, we can show that some of the observed properties of stellar flares can be explained by a model which involves increased pressures and temperatures in the flaring stellar chromosphere. We suggest that changes in stellar flare area, both with time and with depth in the atmosphere, may play an important role in producing the observed flare spectrum

  14. Nebular Continuum and Line Emission in Stellar Population Synthesis Models

    Energy Technology Data Exchange (ETDEWEB)

    Byler, Nell; Dalcanton, Julianne J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Conroy, Charlie; Johnson, Benjamin D., E-mail: ebyler@astro.washington.edu [Department of Astronomy, Harvard University, Cambridge, MA 02138 (United States)

    2017-05-01

    Accounting for nebular emission when modeling galaxy spectral energy distributions (SEDs) is important, as both line and continuum emissions can contribute significantly to the total observed flux. In this work, we present a new nebular emission model integrated within the Flexible Stellar Population Synthesis code that computes the line and continuum emission for complex stellar populations using the photoionization code Cloudy. The self-consistent coupling of the nebular emission to the matched ionizing spectrum produces emission line intensities that correctly scale with the stellar population as a function of age and metallicity. This more complete model of galaxy SEDs will improve estimates of global gas properties derived with diagnostic diagrams, star formation rates based on H α , and physical properties derived from broadband photometry. Our models agree well with results from other photoionization models and are able to reproduce observed emission from H ii regions and star-forming galaxies. Our models show improved agreement with the observed H ii regions in the Ne iii/O ii plane and show satisfactory agreement with He ii emission from z = 2 galaxies, when including rotating stellar models. Models including post-asymptotic giant branch stars are able to reproduce line ratios consistent with low-ionization emission regions. The models are integrated into current versions of FSPS and include self-consistent nebular emission predictions for MIST and Padova+Geneva evolutionary tracks.

  15. MASSCLEANage-STELLAR CLUSTER AGES FROM INTEGRATED COLORS

    International Nuclear Information System (INIS)

    Popescu, Bogdan; Hanson, M. M.

    2010-01-01

    We present the recently updated and expanded MASSCLEANcolors, a database of 70 million Monte Carlo models selected to match the properties (metallicity, ages, and masses) of stellar clusters found in the Large Magellanic Cloud (LMC). This database shows the rather extreme and non-Gaussian distribution of integrated colors and magnitudes expected with different cluster age and mass and the enormous age degeneracy of integrated colors when mass is unknown. This degeneracy could lead to catastrophic failures in estimating age with standard simple stellar population models, particularly if most of the clusters are of intermediate or low mass, like in the LMC. Utilizing the MASSCLEANcolors database, we have developed MASSCLEANage, a statistical inference package which assigns the most likely age and mass (solved simultaneously) to a cluster based only on its integrated broadband photometric properties. Finally, we use MASSCLEANage to derive the age and mass of LMC clusters based on integrated photometry alone. First, we compare our cluster ages against those obtained for the same seven clusters using more accurate integrated spectroscopy. We find improved agreement with the integrated spectroscopy ages over the original photometric ages. A close examination of our results demonstrates the necessity of solving simultaneously for mass and age to reduce degeneracies in the cluster ages derived via integrated colors. We then selected an additional subset of 30 photometric clusters with previously well-constrained ages and independently derive their age using the MASSCLEANage with the same photometry with very good agreement. The MASSCLEANage program is freely available under GNU General Public License.

  16. Automated galaxy surface photometry

    International Nuclear Information System (INIS)

    Cawson, M.G.M.; Kibblewhite, E.J.; Disney, M.J.; Phillipps, S.

    1987-01-01

    Two-dimensional surface photometry of a very large number of galaxies on a deep Schmidt plate has been obtained using the Automatic Plate Measuring System (APM). A method of photometric calibration, suitable for APM measurements, via pixel-by-pixel comparison with CCD frames of a number of the brighter galaxies is described and its advantages are discussed. The same method is used to demonstrate the consistency of measurement of the APM machine when used for surface photometry. (author)

  17. APPHi: Automated Photometry Pipeline for High Cadence Large Volume Data

    Science.gov (United States)

    Sánchez, E.; Castro, J.; Silva, J.; Hernández, J.; Reyes, M.; Hernández, B.; Alvarez, F.; García T.

    2018-04-01

    APPHi (Automated Photometry Pipeline) carries out aperture and differential photometry of TAOS-II project data. It is computationally efficient and can be used also with other astronomical wide-field image data. APPHi works with large volumes of data and handles both FITS and HDF5 formats. Due the large number of stars that the software has to handle in an enormous number of frames, it is optimized to automatically find the best value for parameters to carry out the photometry, such as mask size for aperture, size of window for extraction of a single star, and the number of counts for the threshold for detecting a faint star. Although intended to work with TAOS-II data, APPHi can analyze any set of astronomical images and is a robust and versatile tool to performing stellar aperture and differential photometry.

  18. APT: Aperture Photometry Tool

    Science.gov (United States)

    Laher, Russ

    2012-08-01

    Aperture Photometry Tool (APT) is software for astronomers and students interested in manually exploring the photometric qualities of astronomical images. It has a graphical user interface (GUI) which allows the image data associated with aperture photometry calculations for point and extended sources to be visualized and, therefore, more effectively analyzed. Mouse-clicking on a source in the displayed image draws a circular or elliptical aperture and sky annulus around the source and computes the source intensity and its uncertainty, along with several commonly used measures of the local sky background and its variability. The results are displayed and can be optionally saved to an aperture-photometry-table file and plotted on graphs in various ways using functions available in the software. APT is geared toward processing sources in a small number of images and is not suitable for bulk processing a large number of images, unlike other aperture photometry packages (e.g., SExtractor). However, APT does have a convenient source-list tool that enables calculations for a large number of detections in a given image. The source-list tool can be run either in automatic mode to generate an aperture photometry table quickly or in manual mode to permit inspection and adjustment of the calculation for each individual detection. APT displays a variety of useful graphs, including image histogram, and aperture slices, source scatter plot, sky scatter plot, sky histogram, radial profile, curve of growth, and aperture-photometry-table scatter plots and histograms. APT has functions for customizing calculations, including outlier rejection, pixel “picking” and “zapping,” and a selection of source and sky models. The radial-profile-interpolation source model, accessed via the radial-profile-plot panel, allows recovery of source intensity from pixels with missing data and can be especially beneficial in crowded fields.

  19. Luminosities and temperatures of M dwarf stars from infrared photometry

    Science.gov (United States)

    Veeder, G. J.

    1974-01-01

    Bolometric magnitudes for a large number of M type dwarf stars, obtained by broadband infrared photometry at 1.65, 2.2, and 3.5 microns, are reviewed. The data obtained indicate that one parameter is sufficient to describe the blanketing in all of the UBVRI bands for all types of M dwarfs. In general, late M dwarfs seem to have lower effective temperatures than are predicted by theoretical models.

  20. Aperture Photometry Tool

    Science.gov (United States)

    Laher, Russ R.; Gorjian, Varoujan; Rebull, Luisa M.; Masci, Frank J.; Fowler, John W.; Helou, George; Kulkarni, Shrinivas R.; Law, Nicholas M.

    2012-07-01

    Aperture Photometry Tool (APT) is software for astronomers and students interested in manually exploring the photometric qualities of astronomical images. It is a graphical user interface (GUI) designed to allow the image data associated with aperture photometry calculations for point and extended sources to be visualized and, therefore, more effectively analyzed. The finely tuned layout of the GUI, along with judicious use of color-coding and alerting, is intended to give maximal user utility and convenience. Simply mouse-clicking on a source in the displayed image will instantly draw a circular or elliptical aperture and sky annulus around the source and will compute the source intensity and its uncertainty, along with several commonly used measures of the local sky background and its variability. The results are displayed and can be optionally saved to an aperture-photometry-table file and plotted on graphs in various ways using functions available in the software. APT is geared toward processing sources in a small number of images and is not suitable for bulk processing a large number of images, unlike other aperture photometry packages (e.g., SExtractor). However, APT does have a convenient source-list tool that enables calculations for a large number of detections in a given image. The source-list tool can be run either in automatic mode to generate an aperture photometry table quickly or in manual mode to permit inspection and adjustment of the calculation for each individual detection. APT displays a variety of useful graphs with just the push of a button, including image histogram, x and y aperture slices, source scatter plot, sky scatter plot, sky histogram, radial profile, curve of growth, and aperture-photometry-table scatter plots and histograms. APT has many functions for customizing the calculations, including outlier rejection, pixel “picking” and “zapping,” and a selection of source and sky models. The radial-profile-interpolation source

  1. Microlensing and the physics of stellar atmospheres

    NARCIS (Netherlands)

    Sackett, PD; Menzies, JW; Sackett, PD

    2001-01-01

    The simple physics of microlensing provides a well understood tool with which to probe the atmospheres of distant stars in the Galaxy and Local Group with high magnification and resolution. Recent results in measuring stellar surface structure through broad band photometry and spectroscopy of high

  2. Photometry with NICMOS

    Science.gov (United States)

    Calzetti, D.; Dickinson, M. E.; Bergeron, L. E.; Colina, L.

    1998-12-01

    We summarize the performance of the NICMOS instrument and discuss the measured sensitivity, and the photometric performance and stability. We also present a method for removing an instrument artifact termed ``pedestal'', a bias instability that is present at a low level in most NICMOS images. The characteristics of dark frames will also be discussed, in particular as they relate to pedestal correction. NICMOS is capable of achieving the advertised performance in most areas. As an example, typical 3 sigma detection limits for a 5 orbit observation with NIC2 are 1.47 mJy arcsec(-2) in F110W, 1.67 mJy arcsec(-2) in F160W, and 12.6 mJy arcsec(-2) in F222M. The absence of time-dependent backgrounds makes infrared photometry from NICMOS highly stable, reaching an accuracy of 2% or better. NICMOS absolute calibration has been accomplished with a combination of solar analog stars and white dwarf standard stars and achieves 5% absolute photometry. An exception to these accuracies occurs for NIC3 at short wavelengths where intra-pixel sensitivity variations produces variations in relative photometry as large as 20%.

  3. ARCHANGEL: Galaxy Photometry System

    Science.gov (United States)

    Schombert, James

    2011-07-01

    ARCHANGEL is a Unix-based package for the surface photometry of galaxies. While oriented for large angular size systems (i.e. many pixels), its tools can be applied to any imaging data of any size. The package core contains routines to perform the following critical galaxy photometry functions: sky determination; frame cleaning; ellipse fitting; profile fitting; and total and isophotal magnitudes. The goal of the package is to provide an automated, assembly-line type of reduction system for galaxy photometry of space-based or ground-based imaging data. The procedures outlined in the documentation are flux independent, thus, these routines can be used for non-optical data as well as typical imaging datasets. ARCHANGEL has been tested on several current OS's (RedHat Linux, Ubuntu Linux, Solaris, Mac OS X). A tarball for installation is available at the download page. The main routines are Python and FORTRAN based, therefore, a current installation of Python and a FORTRAN compiler are required. The ARCHANGEL package also contains Python hooks to the PGPLOT package, an XML processor and network tools which automatically link to data archives (i.e. NED, HST, 2MASS, etc) to download images in a non-interactive manner.

  4. UBVRI photometry in NGC6791

    DEFF Research Database (Denmark)

    Brogaard, K.; Vandenberg, D. A.; Bruntt, H.

    2012-01-01

    New reduction of photometric B, V, I observations from Stetson et al. (2003, Cat. J/PASP/115/413) with updated photometry zero-points according to Stetson et al. (2005PASP..117..563S), and the same photometry, but empirically corrected for differential reddening using the procedure described in M...

  5. Evolution of Intrinsic Scatter in the SFR-Stellar Mass Correlation at 0.5 less than z Less Than 3

    Science.gov (United States)

    Kurczynski, Peter; Gawiser, Eric; Acquaviva, Viviana; Bell, Eric F.; Dekel, Avishai; De Mello, Duilia F.; Ferguson, Henry C.; Gardner, Jonathan P.; Grogin, Norman A.

    2016-01-01

    We present estimates of intrinsic scatter in the star formation rate (SFR)--stellar mass (M*) correlation in the redshift range 0.5 less than z less than 3.0 and in the mass range 10(exp 7) less than M* less than 10(exp 11) solar mass. We utilize photometry in the Hubble Ultradeep Field (HUDF12) and Ultraviolet Ultra Deep Field (UVUDF) campaigns and CANDELS/GOODS-S and estimate SFR, M* from broadband spectral energy distributions and the best-available redshifts. The maximum depth of the UDF photometry (F160W 29.9 AB, 5 sigma depth) probes the SFR--M* correlation down to M* approximately 10(exp 7) solar mass, a factor of 10-100 x lower in M* than previous studies, and comparable to dwarf galaxies in the local universe. We find the slope of the SFR-M* relationship to be near unity at all redshifts and the normalization to decrease with cosmic time. We find a moderate increase in intrinsic scatter with cosmic time from 0.2 to 0.4 dex across the epoch of peak cosmic star formation. None of our redshift bins show a statistically significant increase in intrinsic scatter approximately 100 Myr. Our results are consistent with a picture of gradual and self-similar assembly of galaxies across more than three orders of magnitude in stellar mass from as low as 10(exp 7) solar mass.

  6. TNO Photometry and Spectroscopy at ESO and Calar Alto

    Science.gov (United States)

    Boehnhardt, H.; Sekiguchi, T.; Vair, M.; Hainaut, O.; Delahodde, C.; West, R. M.; Tozzi, G. P.; Barrera, L.; Birkle, K.; Watanabe, J.; Meech, K.

    New photometry and spectroscopy of Transneptunian objects (TNO) has been obtained at ESO (VLT+FORS1, NTT+SOFI) and the Calar Alto (3.5m+MOSCA) observatory. BVRI photometry of more than 10 objects confirms the general colour-colour distribution of TNOs found previously. Quasi-simultaneous spectroscopy in the visible wavelength range of 5 TNOs did not reveal any spectral signature apart from the spetral gradients which are in agreement with the broadband colours. JHK filter photometry of 3 objects indicates that the reddening may only occur in the near-IR at least in some cases. Using new observations from the ESO VLT the lightcurve, colours and spectrum of 1996TO66 are investigated: the rotation period of 6.25h is confirmed, also the change in the lightcurve between 1997 and 1998 which indicates an exceptional behaviour in this object (temporary cometary activity ?). The 1999 photometry and spectroscopy in the visible revealed solar colours, no reddening and no spectral features. V-R colour changes over the rotation phase are not found. This works is done in colaboration with:

  7. SCIENCE OF SUN PHOTOMETRY

    Directory of Open Access Journals (Sweden)

    Alexandru Dan Toma

    2013-07-01

    Full Text Available Typically, the total amount of gases and particles in a column of atmosphere cannot be determined from measurements just at Earth's surface, by a single measurement essentially at the bottom of the atmosphere column. Balloons, airplanes, and rockets are all used to perform direct measurements in the atmosphere at altitudes up to and beyond the stratosphere. Satellite-based instruments provide global views, but it is difficult to infer surface and column distributions from space-based measurements, so such measurements must still be supplemented by ground-based measurements. Sun photometry is an important way of probing the atmosphere from the ground to measure the effects of the atmosphere on Sun radiation crossing through the atmosphere to Earth's surface. These indirect technique provide information about the entire atmosphere above the observer, not just the atmosphere that can be sampled directly close to Earth's surface.

  8. Adoption of Broadband Services

    DEFF Research Database (Denmark)

    Falch, Morten

    2008-01-01

    Broadband is seen as a key infrastructure for developing the information society. For this reason many Governments are actively engaged in stimulating investments in broadband infrastructures and use of broadband services. This chapter compares a wide range of broadband strategies in the most suc....... Many countries have provided active support for stimulating diffusion of broadband and national variants of this type of policies in different countries are important for an explanation of national differences in adoption of broadband....

  9. BAGLIN ANNIE, The space stellar photometry mission COROT ...

    Indian Academy of Sciences (India)

    Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately.

  10. Photometry of faint blue stars

    International Nuclear Information System (INIS)

    Kilkenny, D.; Hill, P.W.; Brown, A.

    1977-01-01

    Photometry on the uvby system is given for 61 faint blue stars. The stars are classified by means of the Stromgren indices, using criteria described in a previous paper (Kilkenny and Hill (1975)). (author)

  11. Copernicus spectra and infrared photometry of 42 Orionis

    International Nuclear Information System (INIS)

    Johnson, H.M.; Snow, T.P. Jr.; Gehrz, R.D.; Hackwell, J.A.

    1977-01-01

    The Orion sword star 42 Ori is embedded in a nebula north of and separated from the Orion nebula. The B1 V star is probably normal. Other members of the multiple remain poorly defined, and the nebula may exhibit some peculiarities that may depend on them. Copernicus ultraviolet spectra of the star are described here, especially in the form of tables of wavelength identifications. The properties of the interstellar material in the line of sight are also discussed. We present infrared photometry which suggests that 3 less than or equal to R less than or equal to 3.5 for the interstellar matter in the direction of 42 Ori. The IR photometry provides no evidence for companion stellar or circumstellar components

  12. The Resolved Stellar Populations Early Release Science Program

    Science.gov (United States)

    Gilbert, Karoline; Weisz, Daniel; Resolved Stellar Populations ERS Program Team

    2018-06-01

    The Resolved Stellar Populations Early Release Science Program (PI D. Weisz) will observe Local Group targets covering a range of stellar density and star formation histories, including a globular cluster, and ultra-faint dwarf galaxy, and a star-forming dwarf galaxy. Using observations of these diverse targets we will explore a broad science program: we will measure star formation histories, the sub-solar stellar initial mass function, and proper motions, perform studies of evolved stars, and map extinction in the target fields. Our observations will be of high archival value for other science such as calibrating stellar evolution models, studying variable stars, and searching for metal-poor stars. We will determine optimal observational setups and develop data reduction techniques that will be common to JWST studies of resolved stellar populations. We will also design, test, and release point spread function (PSF) fitting software specific to NIRCam and NIRISS, required for the crowded stellar regime. Prior to the Cycle 2 Call for Proposals, we will release PSF fitting software, matched HST and JWST catalogs, and clear documentation and step-by-step tutorials (such as Jupyter notebooks) for reducing crowded stellar field data and producing resolved stellar photometry catalogs, as well as for specific resolved stellar photometry science applications.

  13. A new study of stellar substructures in the Fornax dwarf spheroidal galaxy

    NARCIS (Netherlands)

    de Boer, T. J. L.; Tolstoy, E.; Saha, A.; Olszewski, E. W.

    Using deep V, B - V wide-field photometry, we have conducted a new study of stellar over-densities in the Fornax dwarf spheroidal galaxy by determining detailed star formation histories from colour-magnitude diagram analysis. We have concentrated on the relatively young stellar component ( We have

  14. Stellar formation

    CERN Document Server

    Reddish, V C

    1978-01-01

    Stellar Formation brings together knowledge about the formation of stars. In seeking to determine the conditions necessary for star formation, this book examines questions such as how, where, and why stars form, and at what rate and with what properties. This text also considers whether the formation of a star is an accident or an integral part of the physical properties of matter. This book consists of 13 chapters divided into two sections and begins with an overview of theories that explain star formation as well as the state of knowledge of star formation in comparison to stellar structure

  15. A NEAR-INFRARED SPECTROSCOPIC SURVEY OF K-SELECTED GALAXIES AT z∼ 2.3: COMPARISON OF STELLAR POPULATION SYNTHESIS CODES AND CONSTRAINTS FROM THE REST-FRAME NIR

    International Nuclear Information System (INIS)

    Muzzin, Adam; Marchesini, Danilo; Van Dokkum, Pieter G.; Labbe, Ivo; Kriek, Mariska; Franx, Marijn

    2009-01-01

    We present spectral energy distribution (SED) modeling of a sample of 34 K-selected galaxies at z∼ 2.3. These galaxies have near-infrared (NIR) spectroscopy that samples the rest-frame Balmer/4000 A break as well as deep photometry in 13 broadband filters. New to our analysis is Infrared Array Camera (IRAC) data that extend the SEDs into the rest-frame NIR. Comparing parameters determined from SED fits with and without the IRAC data we find that the IRAC photometry significantly improves the confidence intervals of τ, A v , M star , and SFR for individual galaxies, but does not systematically alter the mean parameters of the sample. We use the IRAC data to assess how well current stellar population synthesis codes describe the rest-frame NIR SEDs of young galaxies where discrepancies between treatments of the thermally pulsating asymptotic giant branch phase of stellar evolution are most pronounced. The models of Bruzual and Charlot, Maraston, and Charlot and Bruzual all successfully reproduce the SEDs of our galaxies with ≤5% differences in the quality of fit; however, the best-fit masses from each code differ systematically by as much as a factor of 1.5, and other parameters vary more, up to factors of 2-3. A comparison of best-fit stellar population parameters from different stellar population synthesis (SPS) codes, dust laws, and metallicities shows that the choice of SPS code is the largest systematic uncertainty in most parameters, and that systematic uncertainties are typically larger than the formal random uncertainties. The SED fitting confirms our previous result that galaxies with strongly suppressed SF account for ∼50% of the K-bright population at z∼ 2.3; however, the uncertainty in this fraction is large due to systematic differences in the specific star formation rates derived from the three SPS models.

  16. Stellar remnants

    CERN Document Server

    Kawaler, S D; Srinivasan, G

    1997-01-01

    This volume examines the internal structure, origin and evolution of white dwarfs, neutron stars and black holes, all objects at the final stage of stellar evolution. It covers topics such as: pulsation of white dwarfs; millisecond pulsars; and the dynamics around black holes.

  17. Peering through the veil: near-infrared photometry and extinction for the Galactic nuclear star cluster. Accurate near infrared H, Ks, and L' photometry and the near-infrared extinction-law toward the central parsec of the Galaxy

    Science.gov (United States)

    Schödel, R.; Najarro, F.; Muzic, K.; Eckart, A.

    2010-02-01

    Context. The nuclear star cluster of the Galaxy is an important template for understanding its extragalactic counterparts, which can currently not be resolved into individual stars. Important drawbacks of observations of the Galactic center are, however, the presence of strong and spatially highly variable interstellar extinction and extreme crowding of the sources, which makes the use of adaptive optics techniques necessary. Both points pose serious obstacles to precise photometry that is needed for analyzing the stellar population. Aims: The aims of this work are to provide accurate photometry in multiple near-infrared broadband filters, to determine the power-law index of the extinction-law toward the central parsec of the Galaxy, to provide measurements of the absolute extinction toward the Galactic center, and finally to measure the spatial variability of extinction on arcsecond scales. Methods: We use observations of the central parsec of the Milky Way that were obtained with the near-infrared camera and adaptive optics system NAOS/CONICA at the ESO VLT unit telescope 4. The photometric method takes into account anisoplanatic effects and limits the corresponding systematic uncertainties to ≲2%. Absolute values for the extinction in the H, Ks, and L'-bands as well as of the power-law indices of the H to Ks and Ks to L' extinction-laws are measured based on the well-known properties of red clump stars. Extinction maps are derived based on H-Ks and Ks-L' colors. Results: We present Ks-band photometry for ~7700 stars, and additionally photometry for stars detected in the H and/or L'-bands. From a number of recently published values we compute a mean distance of the Galactic center of R0=8.03±0.15 kpc, which has an uncertainty of just 2%. Based on this R0 and on the RC method, we derive absolute mean extinction values toward the central parsec of the Galaxy of AH=4.48±0.13 mag, AKs=2.54±0.12 mag, and AL'=1.27±0.18 mag. We estimate values of the power

  18. Measuring the Stellar Masses of z ~ 7 Galaxies with the Spitzer UltRaFaint SUrvey Program (SURFS UP)

    Science.gov (United States)

    Ryan, R. E., Jr.; Gonzalez, A. H.; Lemaux, B. C.; Bradač, M.; Casertano, S.; Allen, S.; Cain, B.; Gladders, M.; Hall, N.; Hildebradt, H.; Hinz, J.; Huang, K.-H.; Lubin, L.; Schrabback, T.; Stiavelli, M.; Treu, T.; von der Linden, A.; Zaritsky, D.

    2014-05-01

    We present Spitzer/IRAC observations of nine z'-band dropouts highly magnified (2 ~ 7. By modeling the broadband photometry, we estimate the galaxy has an intrinsic star formation rate (SFR) of SFR ~ 1.3 M ⊙ yr-1 and stellar mass of M ~ 2.0 × 109 M ⊙, which gives a specific star formation rate of sSFR ~ 0.7 Gyr-1. If this galaxy had sustained this SFR since z ~ 20, it could have formed the observed stellar mass (to within a factor of ~2). We also discuss alternate star formation histories and argue that the exponentially increasing model is unlikely. Finally, based on the intrinsic SFR, we estimate that this galaxy has a likely [C II] flux of langf [C II]rang = 1.6 mJy. Observations were carried out using the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This research is also based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555 and NNX08AD79G. These observations are associated with programs Spitzer 3550, 60034, 90009, HST GO 10200, GO 10863, 11099, and 11591, and ESO Large Program 181.A-0485.

  19. BV RI CCD photometry of 361,281 objects in the field of M 31

    Science.gov (United States)

    Magnier, E. A.; Lewin, W. H. G.; Van Paradijs, J.; Hasinger, G.; Jain, A.; Pietsch, W.; Truemper, J.

    1992-01-01

    Deep BV RI CCD photometry was performed on a 1 sq deg region of M 31. A catalog of photometry and astrometry of a total of 361,281 stars is presented, with typical completion limits of BV RI = (22.3, 22.2, 22.2, 20.9). Photometric accuracy is about 2 percent at V = 19. This catalog allows detailed studies of stellar populations and reddening. The data are currently being used to assist in finding the optical counterparts of Einstein and ROSAT X-ray sources.

  20. Deep and accurate near-infrared photometry of the Galactic globular cluster omega Cen .

    Science.gov (United States)

    Calamida, A.; Bono, G.; Corsi, C. E.; Stetson, P. B.; Prada Moroni, P. G.; Degl'Innocenti, S.; Marchetti, E.; Amico, P.; Ferraro, I.; Iannicola, G.; Monelli, M.; Buonanno, R.; Caputo, F.; Dall'Ora, M.; Freyhammer, L. M.; Koester, D.; Nonino, M.; Piersimoni, A. M.; Pulone, L.; Romaniello, M.

    We present deep and accurate Near-Infrared (NIR) photometry of the Galactic Globular Cluster omega Cen . Data were collected using the Multi-Conjugate Adaptive Optics Demonstrator (MAD) mounted on the VLT (ESO). We combined the NIR photometry with optical space data collected with the Advanced Camera for Surveys (ACS) for the same region of the cluster. Our deep optical-NIR CMD indicates that the spread in age among the different stellar populations in omega Cen is at most of the order of 2 Gyr.

  1. Stellar winds

    International Nuclear Information System (INIS)

    Weymann, R.J.

    1978-01-01

    It is known that a steady outflow of material at comparable rates of mass loss but vastly different speeds is now known to be ubiquitous phenomenon among both the luminous hot stars and the luminous but cool red giants. The flows are probably massive enough in both cases to give rise to significant effects on stellar evolution and the mass balance between stars and the interstellar medium. The possible mechanisms for these phenomena as well as the methods of observation used are described. In particular, the mass-loss processes in stars other than the sun that also involve a steady flow of matter are considered. The evidence for their existence is described, and then the question of whether the process thought to produce the solar wind is also responsible for producing these stellar winds is explored

  2. Stellarator physics

    International Nuclear Information System (INIS)

    1990-07-01

    This document consists of the proceedings of the Seventh International Workshop on Stellarators, held in Oak Ridge, Tennessee, USA, 10-14 April, 1989. The document consists of a summary of presentations, an overview of experimental results, and papers presented at the workshop on transport, impurities and divertors, diagnostics, ECH confinement experiments, equilibrium and stability studies, RF heating, confinement, magnetic configurations, and new experiments. Refs, figs and tabs

  3. REVISED STELLAR PROPERTIES OF KEPLER TARGETS FOR THE QUARTER 1-16 TRANSIT DETECTION RUN

    Energy Technology Data Exchange (ETDEWEB)

    Huber, Daniel [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Aguirre, Victor Silva [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Matthews, Jaymie M. [Department of Physics and Astronomy, University of British Columbia, Vancouver (Canada); Pinsonneault, Marc H. [Department of Astronomy, Ohio State University, OH 43210 (United States); Gaidos, Eric [Department of Geology and Geophysics, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); García, Rafael A. [Laboratoire AIM, CEA/DSM-CNRS, Université Paris 7 Diderot, IRFU/SAp, Centre de Saclay, F-91191 Gif-sur-Yvette (France); Hekker, Saskia [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Mathur, Savita [Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 (United States); Mosser, Benoit [LESIA, CNRS, Université Pierre et Marie Curie, Université Denis, Diderot, Observatoire de Paris, F-92195 Meudon cedex (France); Torres, Guillermo [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Bastien, Fabienne A. [Department of Physics and Astronomy, Vanderbilt University, 1807 Station B, Nashville, TN 37235 (United States); Basu, Sarbani [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Bedding, Timothy R. [Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006 (Australia); Chaplin, William J. [School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT (United Kingdom); Demory, Brice-Olivier [Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Fleming, Scott W., E-mail: daniel.huber@nasa.gov [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); and others

    2014-03-01

    We present revised properties for 196,468 stars observed by the NASA Kepler mission and used in the analysis of Quarter 1-16 (Q1-Q16) data to detect and characterize transiting planets. The catalog is based on a compilation of literature values for atmospheric properties (temperature, surface gravity, and metallicity) derived from different observational techniques (photometry, spectroscopy, asteroseismology, and exoplanet transits), which were then homogeneously fitted to a grid of Dartmouth stellar isochrones. We use broadband photometry and asteroseismology to characterize 11,532 Kepler targets which were previously unclassified in the Kepler Input Catalog (KIC). We report the detection of oscillations in 2762 of these targets, classifying them as giant stars and increasing the number of known oscillating giant stars observed by Kepler by ∼20% to a total of ∼15,500 stars. Typical uncertainties in derived radii and masses are ∼40% and ∼20%, respectively, for stars with photometric constraints only, and 5%-15% and ∼10% for stars based on spectroscopy and/or asteroseismology, although these uncertainties vary strongly with spectral type and luminosity class. A comparison with the Q1-Q12 catalog shows a systematic decrease in radii of M dwarfs, while radii for K dwarfs decrease or increase depending on the Q1-Q12 provenance (KIC or Yonsei-Yale isochrones). Radii of F-G dwarfs are on average unchanged, with the exception of newly identified giants. The Q1-Q16 star properties catalog is a first step toward an improved characterization of all Kepler targets to support planet-occurrence studies.

  4. Stellar evolution

    CERN Document Server

    Meadows, A J

    2013-01-01

    Stellar Evolution, Second Edition covers the significant advances in the understanding of birth, life, and death of stars.This book is divided into nine chapters and begins with a description of the characteristics of stars according to their brightness, distance, size, mass, age, and chemical composition. The next chapters deal with the families, structure, and birth of stars. These topics are followed by discussions of the chemical composition and the evolution of main-sequence stars. A chapter focuses on the unique features of the sun as a star, including its evolution, magnetic fields, act

  5. Real time 3D photometry

    Science.gov (United States)

    Fernandez-Balbuena, A. A.; Vazquez-Molini, D.; García-Botella, A.; Romo, J.; Serrano, Ana

    2017-09-01

    The photometry and radiometry measurement is a well-developed field. The necessity of measuring optical systems performance involves the use of several techniques like Gonio-photometry. The Gonio photometers are a precise measurement tool that is used in the lighting area like office, luminaire head car lighting, concentrator /collimator measurement and all the designed and fabricated optical systems that works with light. There is one disadvantage in this kind of measurements that obtain the intensity polar curves and the total flux of the optical system. In the industry, there are good Gonio photometers that are precise and reliable but they are very expensive and the measurement time is long. In industry the cost can be of minor importance but measuring time that is around 30 minutes is of major importance due to trained staff cost. We have designed a system to measure photometry in real time; it consists in a curved screen to get a huge measurement angle and a CCD. The system to be measured projects light onto the screen and the CCD records a video of the screen obtaining an image of the projected profile. A complex calibration permits to trace screen data (x,y,z) to intensity polar curve (I,αγ). This intensity is obtained in candels (cd) with an image + processing time below one second.

  6. Broadband Radiometric LED Measurements

    OpenAIRE

    Eppeldauer, G. P.; Cooksey, C. C.; Yoon, H. W.; Hanssen, L. M.; Podobedov, V. B.; Vest, R. E.; Arp, U.; Miller, C. C.

    2016-01-01

    At present, broadband radiometric measurements of LEDs with uniform and low-uncertainty results are not available. Currently, either complicated and expensive spectral radiometric measurements or broadband photometric LED measurements are used. The broadband photometric measurements are based on the CIE standardized V(��) function, which cannot be used in the UV range and leads to large errors when blue or red LEDs are measured in its wings, where the realization is always poor. Reference irr...

  7. Multiple Stellar Populations in Star Clusters

    Science.gov (United States)

    Piotto, G.

    2013-09-01

    For half a century it had been astronomical dogma that a globular cluster (GC) consists of stars born at the same time out of the same material, and this doctrine has borne rich fruits. In recent years, high resolution spectroscopy and high precision photometry (from space and ground-based observations) have shattered this paradigm, and the study of GC populations has acquired a new life that is now moving it in new directions. Evidence of multiple stellar populations have been identified in the color-magnitude diagrams of several Galactic and Magellanic Cloud GCs where they had never been imagined before.

  8. Broadband Faraday isolator.

    Science.gov (United States)

    Berent, Michał; Rangelov, Andon A; Vitanov, Nikolay V

    2013-01-01

    Driving on an analogy with the technique of composite pulses in quantum physics, we theoretically propose a broadband Faraday rotator and thus a broadband optical isolator, which is composed of sequences of ordinary Faraday rotators and achromatic quarter-wave plates rotated at the predetermined angles.

  9. Stellar astrophysics

    International Nuclear Information System (INIS)

    1988-01-01

    Enhanced mass loss occurs at critical stages in the evolution of stars over a wide range of stellar mass. Observationally, these stages are difficult to identify because of their short duration and because the star is often obscured by dust which condenses in the ejecta. A study of a G-type star, of which only the outer envelope was directly visible, was undertaken by the South African Astronomical Observatory (SAAO). The star itself was obscured by dust clouds and its light was only feebly seen by reflection from some of these clouds. Other studies of the galaxy undertaken by the SAAO include observations of the following: the extreme carbon star IRAS 15194-5115; RV Tauri and T Tauri stars; pre-main sequence stars; the properties of circumstellar dust; rotational modulation and flares on RS CVn and BY Dra stars; heavy-element stars; hydrogen-deficient stars; the open cluster NGC6192; stars in Omega Centauri, and lunar occulations of stars. Simultaneous x-ray, radio and optical data of the flare star YZ CMi were also obtained. 1 fig

  10. Stellar physics with the ALHAMBRA photometric system

    International Nuclear Information System (INIS)

    Villegas, T Aparicio; Alfaro, E J; Moles, M; Benítez, N; Perea, J; Olmo, A del; Cristóbal-Hornillos, D; Cervio, M; Delgado, R M González; Márquez, I; Masegosa, J; Prada, F; Cabrera-Caño, J; Fernández-Soto, A; Aguerri, J A L; Cepa, J; Broadhurst, T; Castander, F J; Infante, L; Martínez, V J

    2011-01-01

    The ALHAMBRA photometric system was specifically designed to perform a tomography of the Universe in some selected areas. Although mainly designed for extragalactic purposes, its 20 contiguous, equal-width, medium-band photometric system in the optical wavelength range, shows a great capacity for stellar classification. In this contribution we propose a methodology for stellar classification and physical parameter estimation (T eff , log g, [Fe/H], and color excess E(B – V)) based on 18 independent reddening-free Q-values from the ALHAMBRA photometry. Based on the theoretical Spectral library BaSeL 2.2, and applied to 288 stars from the Next Generation spectral Library (NGSL), we discuss the reliability of the method and its dependence on the extinction law used.

  11. Recovering physical properties from narrow-band photometry

    Science.gov (United States)

    Schoenell, W.; Cid Fernandes, R.; Benítez, N.; Vale Asari, N.

    2013-05-01

    Our aim in this work is to answer, using simulated narrow-band photometry data, the following general question: What can we learn about galaxies from these new generation cosmological surveys? For instance, can we estimate stellar age and metallicity distributions? Can we separate star-forming galaxies from AGN? Can we measure emission lines, nebular abundances and extinction? With what precision? To accomplish this, we selected a sample of about 300k galaxies with good S/N from the SDSS and divided them in two groups: 200k objects and a template library of 100k. We corrected the spectra to z = 0 and converted them to filter fluxes. Using a statistical approach, we calculated a Probability Distribution Function (PDF) for each property of each object and the library. Since we have the properties of all the data from the STARLIGHT-SDSS database, we could compare them with the results obtained from summaries of the PDF (mean, median, etc). Our results shows that we retrieve the weighted average of the log of the galaxy age with a good error margin (σ ≈ 0.1 - 0.2 dex), and similarly for the physical properties such as mass-to-light ratio, mean stellar metallicity, etc. Furthermore, our main result is that we can derive emission line intensities and ratios with similar precision. This makes this method unique in comparison to the other methods on the market to analyze photometry data and shows that, from the point of view of galaxy studies, future photometric surveys will be much more useful than anticipated.

  12. McDonald 2.1-m and CRTS Photometry of Eclipsing Polars

    Science.gov (United States)

    Wells, Natalie; Mason, Paul

    2018-01-01

    We present broadband optical photometry of five polars made using the 2.1-m telescope of McDonald Observatory. Four of the polars are eclipsing (EP Dra, FL Cet, V2301 Oph, and a Catalina Sky Survey (CSS) polar candidate). In addition, a pre-polar (MQ Dra) was observed. Typical integration times were 1-3 seconds with no dead time. At this time resolution, eclipse structure can be seen in both one- and two-pole accretors. McDonald 2.1-m data over several years is phased together with CSS photometry covering up to 7 years, in search of indications of period variation. Combining the high-resolution, high-speed photometry obtained using the ProEm camera on the McDonald 2.1-m with the sparse, but high-quality multi-year baseline photometry of the CSS places strong constraints on the time variability of the eclipse periods in these binary systems. In most cases, eclipse variations do not perfectly fit a linear ephemeris. We investigate the source of variations using standard O-C diagram techniques and period search algorithms.

  13. CCD photometry of NGC 2419

    International Nuclear Information System (INIS)

    Christian, C.A.; Heasley, J.N.

    1988-01-01

    The properties of the globular cluster NGC 2419 are reexamined using CCD photometry deepened to the vicinity of the main-sequence turnoff. A new color-magnitude diagram is derived that extends to V = 24.5 mag. It is concluded that NGC 2419 is an outer-halo analog of the metal-poor globulars closer to the Galactic center. NGC 2419 is probably nearly the same age as M15 and differs only slightly, if at all, in metallicity. NGC 2419 has many similarities with the clusters NGC 5466, M15, and M92. Comparison of the data with the isochrones of VandenBerg and Bell (1985) implies a distance modulus of 20.1 with Delta (B-V) = 0.18 mag. Oxygen-rich models can be fit to the data; such a comparison yields a lower limit to the acceptable distance modulus of the cluster. 26 references

  14. Stochastic 2-D galaxy disk evolution models. Resolved stellar populations in the galaxy M33

    Science.gov (United States)

    Mineikis, T.; Vansevičius, V.

    We improved the stochastic 2-D galaxy disk models (Mineikis & Vansevičius 2014a) by introducing enriched gas outflows from galaxies and synthetic color-magnitude diagrams of stellar populations. To test the models, we use the HST/ACS stellar photometry data in four fields located along the major axis of the galaxy M33 (Williams et al. 2009) and demonstrate the potential of the models to derive 2-D star formation histories in the resolved disk galaxies.

  15. Stellar Metamorphosis:

    Science.gov (United States)

    2002-01-01

    [TOP LEFT AND RIGHT] The Hubble Space Telescope's Wide Field and Planetary Camera 2 has captured images of the birth of two planetary nebulae as they emerge from wrappings of gas and dust, like butterflies breaking out of their cocoons. These images highlight a fleeting phase in the stellar burnout process, occurring just before dying stars are transformed into planetary nebulae. The left-hand image is the Cotton Candy nebula, IRAS 17150-3224; the right-hand image, the Silkworm nebula, IRAS 17441-2411. Called proto-planetary nebulae, these dying stars have been caught in a transition phase between a red giant and a planetary nebula. This phase is only about 1,000 years long, very short in comparison to the 1 billion-year lifetime of a star. These images provide the earliest snapshots of the transition process. Studying images of proto-planetary nebulae is important to understanding the process of star death. A star begins to die when it has exhausted its thermonuclear fuel - hydrogen and helium. The star then becomes bright and cool (red giant phase) and swells to several tens of times its normal size. It begins puffing thin shells of gas off into space. These shells become the star's cocoon. In the Hubble images, the shells are the concentric rings seen around each nebula. But the images also reveal the nebulae breaking out from those shells. The butterfly-like wings of gas and dust are a common shape of planetary nebulae. Such butterfly shapes are created by the 'interacting winds' process, in which a more recent 'fast wind' - material propelled by radiation from the hot central star - punches a hole in the cocoon, allowing the nebula to emerge. (This 'interacting wind' theory was first proposed by Dr. Sun Kwok to explain the origin of planetary nebulae, and has been subsequently proven successful in explaining their shapes.) The nebulae are being illuminated by light from the invisible central star, which is then reflected toward us. We are viewing the nebulae

  16. Broadband Electromagnetic Technology

    Science.gov (United States)

    2011-06-23

    The objectives of this project are to continue the enhancements to the combined Broadband Electromagnetic and Full Encirclement Unit (BEM-FEU) technologies and to evaluate the systems capability in the laboratory and the field. The BEM instrument ...

  17. Broadband radiometric LED measurements

    Science.gov (United States)

    Eppeldauer, G. P.; Cooksey, C. C.; Yoon, H. W.; Hanssen, L. M.; Podobedov, V. B.; Vest, R. E.; Arp, U.; Miller, C. C.

    2016-09-01

    At present, broadband radiometric LED measurements with uniform and low-uncertainty results are not available. Currently, either complicated and expensive spectral radiometric measurements or broadband photometric LED measurements are used. The broadband photometric measurements are based on the CIE standardized V(λ) function, which cannot be used in the UV range and leads to large errors when blue or red LEDs are measured in its wings, where the realization is always poor. Reference irradiance meters with spectrally constant response and high-intensity LED irradiance sources were developed here to implement the previously suggested broadband radiometric LED measurement procedure [1, 2]. Using a detector with spectrally constant response, the broadband radiometric quantities of any LEDs or LED groups can be simply measured with low uncertainty without using any source standard. The spectral flatness of filtered-Si detectors and low-noise pyroelectric radiometers are compared. Examples are given for integrated irradiance measurement of UV and blue LED sources using the here introduced reference (standard) pyroelectric irradiance meters. For validation, the broadband measured integrated irradiance of several LED-365 sources were compared with the spectrally determined integrated irradiance derived from an FEL spectral irradiance lamp-standard. Integrated responsivity transfer from the reference irradiance meter to transfer standard and field UV irradiance meters is discussed.

  18. ASTROPOP: ASTROnomical Polarimetry and Photometry pipeline

    Science.gov (United States)

    Campagnolo, Julio C. N.

    2018-05-01

    AstroPoP reduces almost any CCD photometry and image polarimetry data. For photometry reduction, the code performs source finding, aperture and PSF photometry, astrometry calibration using different automated and non-automated methods and automated source identification and magnitude calibration based on online and local catalogs. For polarimetry, the code resolves linear and circular Stokes parameters produced by image beam splitter or polarizer polarimeters. In addition to the modular functions, ready-to-use pipelines based in configuration files and header keys are also provided with the code. AstroPOP was initially developed to reduce the IAGPOL polarimeter data installed at Observatório Pico dos Dias (Brazil).

  19. The Universal Stellar Mass-Stellar Metallicity Relation for Dwarf Galaxies

    OpenAIRE

    Kirby, Evan N.; Cohen, Judith G.; Guhathakurta, Puragra; Cheng, Lucy; Bullock, James S.; Gallazzi, Anna

    2013-01-01

    We present spectroscopic metallicities of individual stars in seven gas-rich dwarf irregular galaxies (dIrrs), and we show that dIrrs obey the same massmetallicity relation as the dwarf spheroidal (dSph) satellites of both the Milky Way and M31: Z * σ M * 0.30±0. 02 . The uniformity of the relation is in contradiction to previous estimates of metallicity based on photometry. This relationship is roughly continuous with the stellar massstellar metallicity relation for galaxies as massive asM*...

  20. macula: Rotational modulations in the photometry of spotted stars

    Science.gov (United States)

    Kipping, David M.

    2012-09-01

    Photometric rotational modulations due to starspots remain the most common and accessible way to study stellar activity. Modelling rotational modulations allows one to invert the observations into several basic parameters, such as the rotation period, spot coverage, stellar inclination and differential rotation rate. The most widely used analytic model for this inversion comes from Budding (1977) and Dorren (1987), who considered circular, grey starspots for a linearly limb darkened star. That model is extended to be more suitable in the analysis of high precision photometry such as that by Kepler. Macula, a Fortran 90 code, provides several improvements, such as non-linear limb darkening of the star and spot, a single-domain analytic function, partial derivatives for all input parameters, temporal partial derivatives, diluted light compensation, instrumental offset normalisations, differential rotation, starspot evolution and predictions of transit depth variations due to unocculted spots. The inclusion of non-linear limb darkening means macula has a maximum photometric error an order-of-magnitude less than that of Dorren (1987) for Sun-like stars observed in the Kepler-bandpass. The code executes three orders-of-magnitude faster than comparable numerical codes making it well-suited for inference problems.

  1. Near Continuous Photometry with the Whole Earth Telescope (WET

    Directory of Open Access Journals (Sweden)

    Solheim J. E.

    2003-12-01

    Full Text Available The Whole Earth Telescope (WET saw first light in 1988. It was invented by scientists from the Astronomy Department, University of Texas at Austin. The idea was to generate a world-wide network of cooperating astronomical observatories to obtain uninterrupted time-series measurements of some variable stars. The technological goal was to resolve the multi-periodic oscillations in these objects into their individual components; the scientific goal was to construct accurate theoretical models of the target objects, constrained by their observed behavior, from which fundamental astrophysical parameters could be derived. This approach has been extremely successful, and has placed stellar seismology at the forefront of stellar astrophysics. The network is run as a single astronomical instrument with many operators, and the collaboration includes scientists from all continents on our planet, taking part in the observations, data reduction, analysis and theoretical interpretation. The expertise of Lithuanian astronomers in photometry, and their access to the observing station Mt. Maidanak in Uzbekistan, has been important for the success of the network.

  2. The impact of Spitzer infrared data on stellar mass estimates - and a revised galaxy stellar mass function at 0 < z < 5

    Science.gov (United States)

    Elsner, F.; Feulner, G.; Hopp, U.

    2008-01-01

    Aims:We estimate stellar masses of galaxies in the high redshift universe with the intention of determining the influence of newly available Spitzer/IRAC infrared data on the analysis. Based on the results, we probe the mass assembly history of the universe. Methods: We use the GOODS-MUSIC catalog, which provides multiband photometry from the U-filter to the 8 μm Spitzer band for almost 15 000 galaxies with either spectroscopic (for ≈7% of the sample) or photometric redshifts, and apply a standard model fitting technique to estimate stellar masses. We than repeat our calculations with fixed photometric redshifts excluding Spitzer photometry and directly compare the outcomes to look for systematic deviations. Finally we use our results to compute stellar mass functions and mass densities up to redshift z = 5. Results: We find that stellar masses tend to be overestimated on average if further constraining Spitzer data are not included into the analysis. Whilst this trend is small up to intermediate redshifts z ⪉ 2.5 and falls within the typical error in mass, the deviation increases strongly for higher redshifts and reaches a maximum of a factor of three at redshift z ≈ 3.5. Thus, up to intermediate redshifts, results for stellar mass density are in good agreement with values taken from literature calculated without additional Spitzer photometry. At higher redshifts, however, we find a systematic trend towards lower mass densities if Spitzer/IRAC data are included.

  3. Constraining stellar physics from red-giant stars in binaries – stellar rotation, mixing processes and stellar activity

    Directory of Open Access Journals (Sweden)

    Beck P. G.

    2017-01-01

    Full Text Available The unparalleled photometric data obtained by NASA’s Kepler Space Telescope has led to an improved understanding of stellar structure and evolution - in particular for solar-like oscillators in this context. Binary stars are fascinating objects. Because they were formed together, binary systems provide a set of two stars with very well constrained parameters. Those can be used to study properties and physical processes, such as the stellar rotation, dynamics and rotational mixing of elements and allows us to learn from the differences we find between the two components. In this work, we discussed a detailed study of the binary system KIC 9163796, discovered through Kepler photometry. The ground-based follow-up spectroscopy showed that this system is a double-lined spectroscopic binary, with a mass ratio close to unity. However, the fundamental parameters of the components of this system as well as their lithium abundances differ substantially. Kepler photometry of this system allows to perform a detailed seismic analysis as well as to derive the orbital period and the surface rotation rate of the primary component of the system. Indications of the seismic signature of the secondary are found. The differing parameters are best explained with both components located in the early and the late phase of the first dredge up at the bottom of the red-giant branch. Observed lithium abundances in both components are in good agreement with prediction of stellar models including rotational mixing. By combining observations and theory, a comprehensive picture of the system can be drawn.

  4. Stroemgren and BV photometry of potential halo blue horizontal branch field stars

    Energy Technology Data Exchange (ETDEWEB)

    Flynn, C; Sommer-Larsen, J

    1988-11-01

    Stroemgren four-colour and broadband BV photoelectric photometry has been obtained for a sample of potential halo blue horizontal branch stars in two high galactic latitude fields. The large majority of the stars observed are classified as blue horizontal branch stars on the basis of two different surface gravity indicators. Measurements of Ca K-line equivalent widths from medium-dispersion spectra of the stars confirm that most are Population II objects. No metal-rich A-stars were found beyond a few kpc from the galactic disc in the study of faint blue stars.

  5. Advanced stellarator power plants

    International Nuclear Information System (INIS)

    Miller, R.L.

    1994-01-01

    The stellarator is a class of helical/toroidal magnetic fusion devices. Recent international progress in stellarator power plant conceptual design is reviewed and comparisons in the areas of physics, engineering, and economics are made with recent tokamak design studies

  6. The stellar content of the isolated transition dwarf galaxy DDO210

    NARCIS (Netherlands)

    McConnachie, Alan W.; Arimoto, Nobuo; Irwin, Mike; Tolstoy, Eline

    2006-01-01

    We use Subaru Suprime-Cam and VLT FORS1 photometry of the dwarf galaxy DDO210 to study the global stellar content and structural properties of a transition-type galaxy (with properties intermediate between dwarf irregular and dwarf spheroidal systems). This galaxy is sufficiently isolated that tidal

  7. Flattening and truncation of stellar discs in edge-on spiral galaxies

    NARCIS (Netherlands)

    Kregel, M; van der Kruit, PC; de Grijs, R

    We analyse the global structure of the old stellar discs in 34 edge-on spiral galaxies. The radial and vertical exponential scale parameters of the discs are obtained by applying an improved two-dimensional decomposition technique to our I -band photometry. We find a clear increase in the disc

  8. Astronomical Photometry Past, Present, and Future

    CERN Document Server

    Milone, Eugene F

    2011-01-01

    This book brings together experts in the field of astronomical photometry to discuss how their subfields provide the precision and accuracy in astronomical energy flux measurements that are needed to permit tests of astrophysical theories. Differential photometers and photometry, improvements in infrared precision, the improvements in precision and accuracy of CCD photometry, the absolute calibration of flux, the development of the Johnson UBVRI photometric system and other passband systems to measure and precisely classify specific types of stars and astrophysical quantities, and the current capabilities of spectrophotometry and polarimetry to provide precise and accurate data, are all discussed in this volume. The discussion of `differential’ or `two-star’ photometers ranges from early experiments in visual photometry through the Harvard and Princeton polarizing photometers to the pioneering work of Walraven and differential photometers designed to minimize effects of atmospheric extinction and to count...

  9. THE IMPACT OF CONTAMINATED RR LYRAE/GLOBULAR CLUSTER PHOTOMETRY ON THE DISTANCE SCALE

    Energy Technology Data Exchange (ETDEWEB)

    Majaess, D.; Turner, D.; Lane, D. [Department of Astronomy and Physics, Saint Mary' s University, Halifax, NS B3H 3C3 (Canada); Gieren, W., E-mail: dmajaess@ap.smu.ca [Departamento de Astronomia, Universidad de Concepcion, Casilla 160-C, CL Concepcion (Chile)

    2012-06-10

    RR Lyrae variables and the stellar constituents of globular clusters are employed to establish the cosmic distance scale and age of the universe. However, photometry for RR Lyrae variables in the globular clusters M3, M15, M54, M92, NGC 2419, and NGC 6441 exhibit a dependence on the clustercentric distance. For example, variables and stars positioned near the crowded high-surface brightness cores of the clusters may suffer from photometric contamination, which invariably affects a suite of inferred parameters (e.g., distance, color excess, absolute magnitude, etc.). The impetus for this study is to mitigate the propagation of systematic uncertainties by increasing awareness of the pernicious impact of contaminated and radial-dependent photometry.

  10. Infrared photometry of galaxies in the Butcher-Oemler cluster 0024+1654

    International Nuclear Information System (INIS)

    Lilly, S.J.; Gunn, J.E.

    1985-01-01

    Infrared photometry is presented for 21 galaxies that are spectroscopically confirmed members of the Butcher-Oemler cluster C10024+1654 at z=0.39. These data are combined with optical CCD photometry and transformed to produce rest-frame UBVK colours. The distribution of colours in the (U-V)/(V-K) plane is analysed. The 11 'red' galaxies have colours that are broadly similar to those of nearby elliptical galaxies. All but one of the 10 'blue' galaxies have the colours of nearby spiral galaxies, including one Im-type galaxy, and other interpretations, e.g. a young age, may be discounted. The (V-K) colour of the remaining 'blue' galaxy, however, suggests the presence of a substantial intermediate age (approx. 1 Gyr) stellar population. (author)

  11. Isochrone Fitting of Hubble Photometry in UV–VIS–IR Bands

    Science.gov (United States)

    Barker, Hallie; Paust, Nathaniel E. Q.

    2018-03-01

    We present new isochrone fits to color–magnitude diagrams from Hubble Space Telescope Wide Field Camera 3 and Advanced Camera for Surveys photometry of the globular clusters M13 and M80 in five bands from the ultraviolet to near-infrared. Isochrone fits to the photometry using the Dartmouth Stellar Evolution Program (DSEP), the PAdova and TRieste Stellar Evolution Code (PARSEC), and MESA Isochrones and Stellar Tracks (MIST) are examined to study the isochrone morphology. Additionally, cluster ages, extinctions, and distances are found from the visible-infrared color–magnitude diagrams. We conduct careful qualitative analysis on the inconsistencies of the fits across twelve color combinations of the five observed bands, and find that the (F606W‑F814W) color generally produces very good fits, but that there are large discrepancies when the data is fit using colors including UV bands for all three models. We also find that the best fits in the UV are achieved using MIST isochrones, but that they require metallicities that are lower than the other two models, as well published spectroscopic values. Finally, we directly compare DSEP and PARSEC by performing isochrone-isochrone fitting, and find that, for globular cluster aged populations, similar appearing PARSEC isochrones are on average 1.5 Gyr younger than DSEP isochrones. We find that the two models become less discrepant at lower metallicities.

  12. Direct UV-written broadband directional broadband planar waveguide couplers

    DEFF Research Database (Denmark)

    Olivero, Massimo; Svalgaard, Mikael

    2005-01-01

    We report the fabrication of broadband directional couplers by direct UV-writing. The fabrication process is shown to be beneficial, robust and flexible. The components are compact and show superior performance in terms of loss and broadband operation.......We report the fabrication of broadband directional couplers by direct UV-writing. The fabrication process is shown to be beneficial, robust and flexible. The components are compact and show superior performance in terms of loss and broadband operation....

  13. Broadband Internet and Income Inequality

    OpenAIRE

    HOUNGBONON , Georges Vivien; Liang , Julienne

    2017-01-01

    Policy makers are aiming for a large coverage of high-speed broadband Internet. However , there is still a lack of evidence about its effects on income distribution. In this paper, we investigate the effects of fixed broadband Internet on mean income and income inequality using a unique town-level data on broadband adoption and quality in France. We find that broadband adoption and quality raise mean income and lower income inequality. These results are robust to initial conditions, and yield...

  14. First evidence of multiple populations along the AGB from Strömgren photometry

    Science.gov (United States)

    Gruyters, Pieter; Casagrande, Luca; Milone, Antonino P.; Hodgkin, Simon T.; Serenelli, Aldo; Feltzing, Sofia

    2017-07-01

    Spectroscopic studies have demonstrated that nearly all Galactic globular clusters (GCs) harbour multiple stellar populations with different chemical compositions. Moreover, colour-magnitude diagrams based exclusively on Strömgrem photometry have allowed us to identify and characterise multiple populations along the RGB of a large number of clusters. In this paper we show for the first time that Strömgren photometry is also very efficient at identifying multiple populations along the AGB, and demonstrate that the AGB of M 3, M 92, NGC 362, NGC 1851, and NGC 6752 are not consistent with a single stellar population. We also provide a catalogue of RGB and AGB stars photometrically identified in these clusters for further spectroscopic follow-up studies. We combined photometry and elemental abundances from the literature for RGB and AGB stars in NGC 6752 where the presence of multiple populations along the AGB has been widely debated. We find that, while the MS, SGB, and RGB host three stellar populations with different helium and light element abundances, only two populations of AGB stars are present in the cluster. These results are consistent with standard evolutionary theory. Based on observations made with the Isaac Newton Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.Full Tables B.1 and B.2 are only 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/603/A37

  15. Broadband waveguided light sources

    NARCIS (Netherlands)

    Pollnau, Markus

    In recent years, broadband fiber interferometers have become very popular as basic instruments used in optical low-coherence reflectometry for diagnostics of fiber and integrated optics devices or in optical coherence tomography (OCT) for imaging applications in the biomedical field. The

  16. BVRI SURFACE PHOTOMETRY OF ISOLATED GALAXY TRIPLETS

    International Nuclear Information System (INIS)

    Hernandez-Toledo, H. M.; Mendez-Hernandez, H.; Aceves, H.; OlguIn, L.

    2011-01-01

    Optical broadband BVRI observations of 54 galaxies selected from the Catalog of Isolated Triplets of Galaxies in the Northern Hemisphere have been carried out at San Pedro Martir National Observatory to evaluate their photometric and morphological properties. We complement our analysis with Two-Micron All Sky Survey (2MASS) and Sloan Digital Sky Survey (SDSS) images and look for signatures likely related to interactions/mergers. We report apparent/absolute BVRI magnitudes and colors for the 54 galaxies. The membership of these galaxies is re-evaluated by imposing a reasonable condition of concordant redshifts upon the original selection criteria, rendering a final sample of 34 galaxies in 13 triplets, 12 galaxies in close pairs, and 8 galaxy outliers. The triplets are spiral-dominated systems in different dynamical stages from loosely interacting to almost merged objects. The incidence fraction of features likely associated with interactions is ∼56%, similar to those found in northern and southern compact groups. The average fraction of bars is 35% with a mean value of maximum bar ellipticity ε max ∼ 0.4. Bars are hosted in the late-type triplet spirals, almost twice more than in early-type spirals. The global fraction of rings is 20%, all in the late-type components. The overdensity of triplets with respect to the background and their current dynamical status, as devised from our estimate of their dynamical parameters, namely the harmonic radius R H , velocity dispersion σ, dimensionless crossing time H 0 τ c , and virial mass M V , appear to be sufficient to favor galaxy transformations similar to those seen in dense groups and clusters. By contrast, the lower fraction of bonafide ellipticals and the relatively higher fraction of late-type spirals make these triplets essentially different from the Hickson Compact Groups and more representative of the field. A modest 1.6 enhancement factor in the optical luminosity of the late-type triplet components

  17. Systematic main sequence photometry of globular cluster stars for age determination

    International Nuclear Information System (INIS)

    Alcaino, G.; Liller, W.

    1984-01-01

    The individual photometric study of the coeval stars in globular clusters presents one of the best observational tests of the stellar evolution theory. Our own globular cluster system provides fundamental clues to the dynamical and chemical evolutionary history of the galaxy, and the study of their ages give a lower limit to the age of the galaxy as well as to that of the universe. The authors have undertaken a systematic research program, and discuss the ages deduced by fitting main sequence photometry to theoretical isochrones of six galactic globular clusters: M4, M22, M30, NGC 288, NGC 3201 and NGC 6397. (Auth.)

  18. THE ACCURACY OF Hβ CCD PHOTOMETRY

    Directory of Open Access Journals (Sweden)

    C. Kim

    1994-12-01

    Full Text Available We have undertaken CCD observations of field standard stars with Hβ photometric system to investigate the reliability of Hβ CCD photometry. Flat fielding with dome flat and sky flat for Hβw and Hβn filter was compared with that of B filter in UBV system and, from these, we have not found any difference. It was confirmed that there is a good linear relationship between our Hβ values observed with 2.3m reflector and standard values. However, Hβ values observed with 60cm reflector at Sobaeksan Astronomy Observatory showed very poor relationship. To investigate the accuracy of Hβ CCD photometry for fainter objects, open cluster NGC2437 was observed and reduced with DoPHOT, and the results were compared with those for photoelectric photometry of Stetson (1981.

  19. Stellar structure and evolution

    International Nuclear Information System (INIS)

    Kippernhahn, R.; Weigert, A.

    1990-01-01

    This book introduces the theory of the internal structure of stars and their evolution in time. It presents the basic physics of stellar interiors, methods for solving the underlying equations, and the most important results necessary for understanding the wide variety of stellar types and phenomena. The evolution of stars is discussed from their birth through normal evolution to possibly spectacular final stages. Chapters on stellar oscillations and rotation are included

  20. Spitzer Photometry of WISE-Selected Brown Dwarf and Hyper-Lumninous Infrared Galaxy Candidates

    Science.gov (United States)

    Griffith, Roger L.; Kirkpatrick, J. Davy; Eisenhardt, Peter R. M.; Gelino, Christopher R.; Cushing, Michael C.; Benford, Dominic; Blain, Andrew; Bridge, Carrie R.; Cohen, Martin; Cutri, Roc M.; hide

    2012-01-01

    We present Spitzer 3.6 and 4.5 micrometer photometry and positions for a sample of 1510 brown dwarf candidates identified by the Wide-field Infrared Survey Explorer (WISE) all-sky survey. Of these, 166 have been spectroscopically classified as objects with spectral types M(1), L(7), T(146), and Y(12). Sixteen other objects are non-(sub)stellar in nature. The remainder are most likely distant L and T dwarfs lacking spectroscopic verification, other Y dwarf candidates still awaiting follow-up, and assorted other objects whose Spitzer photometry reveals them to be background sources. We present a catalog of Spitzer photometry for all astrophysical sources identified in these fields and use this catalog to identify seven fainter (4.5 m to approximately 17.0 mag) brown dwarf candidates, which are possibly wide-field companions to the original WISE sources. To test this hypothesis, we use a sample of 919 Spitzer observations around WISE-selected high-redshift hyper-luminous infrared galaxy candidates. For this control sample, we find another six brown dwarf candidates, suggesting that the seven companion candidates are not physically associated. In fact, only one of these seven Spitzer brown dwarf candidates has a photometric distance estimate consistent with being a companion to the WISE brown dwarf candidate. Other than this, there is no evidence for any widely separated (greater than 20 AU) ultra-cool binaries. As an adjunct to this paper, we make available a source catalog of 7.33 x 10(exp 5) objects detected in all of these Spitzer follow-up fields for use by the astronomical community. The complete catalog includes the Spitzer 3.6 and 4.5 m photometry, along with positionally matched B and R photometry from USNO-B; J, H, and Ks photometry from Two Micron All-Sky Survey; and W1, W2, W3, and W4 photometry from the WISE all-sky catalog.

  1. Jonckheere Double Star Photometry - Part VII: Aquarius

    Science.gov (United States)

    Knapp, Wilfried R. A.

    2017-10-01

    If any double star discoverer is in urgent need of photometry then it is Jonckheere. There are over 3000 Jonckheere objects listed in the WDS catalog and a good part of them with magnitudes obviously far too bright. This report covers the Jonckheere objects in the constellation Aquarius. One image per object was taken with V-filter to allow for visual magnitude measurement by differential pho-tometry. All objects were additionally checked for common proper motion by comparing 2MASS to GAIA DR1 positions and a rather surprisingly large part of the objects qualify indeed as potential CPM pairs. For a few objects also WDS position errors were found.

  2. Stellar Physics 2: Stellar Evolution and Stability

    CERN Document Server

    Bisnovatyi-Kogan, Gennady S

    2011-01-01

    "Stellar Physics" is a an outstanding book in the growing body of literature on star formation and evolution. Not only does the author, a leading expert in the field, very thoroughly present the current state of knowledge on stellar physics, but he handles with equal care the many problems that this field of research still faces. A bibliography with well over 1000 entries makes this book an unparalleled reference source. "Stellar Evolution and Stability" is the second of two volumes and can be read, as can the first volume "Fundamental Concepts and Stellar Equilibrium," as a largely independent work. It traces in great detail the evolution of protostars towards the main sequence and beyond this to the last stage of stellar evolution, with the corresponding vast range from white dwarfs to supernovae explosions, gamma-ray bursts and black hole formation. The book concludes with special chapters on the dynamical, thermal and pulsing stability of stars. This second edition is carefully updated in the areas of pre...

  3. STRESS - STEREO TRansiting Exoplanet and Stellar Survey

    Science.gov (United States)

    Sangaralingam, Vinothini; Stevens, Ian R.; Spreckley, Steve; Debosscher, Jonas

    2010-02-01

    The Heliospheric Imager (HI) instruments on board the two STEREO (Solar TErrestrial RElations Observatory) spacecraft provides an excellent opportunity for space based stellar photometry. The HI instruments provide a wide area coverage (20° × 20° for the two HI-1 instruments and 70° × 70° for the two HI-2 instruments) and long continuous periods of observations (20 days and 70 days respectively). Using HI-1A which has a pass band of 6500Å to 7500Å and a cadence of 40 minutes, we have gathered photometric information for more than a million stars brighter than 12th magnitude for a period of two years. Here we present some early results from this study on a range of variable stars and the future prospects for the data.

  4. SPARC: MASS MODELS FOR 175 DISK GALAXIES WITH SPITZER PHOTOMETRY AND ACCURATE ROTATION CURVES

    Energy Technology Data Exchange (ETDEWEB)

    Lelli, Federico; McGaugh, Stacy S. [Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106 (United States); Schombert, James M., E-mail: federico.lelli@case.edu [Department of Physics, University of Oregon, Eugene, OR 97403 (United States)

    2016-12-01

    We introduce SPARC ( Spitzer Photometry and Accurate Rotation Curves): a sample of 175 nearby galaxies with new surface photometry at 3.6  μ m and high-quality rotation curves from previous H i/H α studies. SPARC spans a broad range of morphologies (S0 to Irr), luminosities (∼5 dex), and surface brightnesses (∼4 dex). We derive [3.6] surface photometry and study structural relations of stellar and gas disks. We find that both the stellar mass–H i mass relation and the stellar radius–H i radius relation have significant intrinsic scatter, while the H i   mass–radius relation is extremely tight. We build detailed mass models and quantify the ratio of baryonic to observed velocity ( V {sub bar}/ V {sub obs}) for different characteristic radii and values of the stellar mass-to-light ratio (ϒ{sub ⋆}) at [3.6]. Assuming ϒ{sub ⋆} ≃ 0.5 M {sub ⊙}/ L {sub ⊙} (as suggested by stellar population models), we find that (i) the gas fraction linearly correlates with total luminosity; (ii) the transition from star-dominated to gas-dominated galaxies roughly corresponds to the transition from spiral galaxies to dwarf irregulars, in line with density wave theory; and (iii)  V {sub bar}/ V {sub obs} varies with luminosity and surface brightness: high-mass, high-surface-brightness galaxies are nearly maximal, while low-mass, low-surface-brightness galaxies are submaximal. These basic properties are lost for low values of ϒ{sub ⋆} ≃ 0.2 M {sub ⊙}/ L {sub ⊙} as suggested by the DiskMass survey. The mean maximum-disk limit in bright galaxies is ϒ{sub ⋆} ≃ 0.7 M {sub ⊙}/ L {sub ⊙} at [3.6]. The SPARC data are publicly available and represent an ideal test bed for models of galaxy formation.

  5. SMASH: Survey of the MAgellanic Stellar History

    Science.gov (United States)

    Nidever, David L.; Olsen, Knut; Walker, Alistair R.; Vivas, A. Katherina; Blum, Robert D.; Kaleida, Catherine; Choi, Yumi; Conn, Blair C.; Gruendl, Robert A.; Bell, Eric F.; Besla, Gurtina; Muñoz, Ricardo R.; Gallart, Carme; Martin, Nicolas F.; Olszewski, Edward W.; Saha, Abhijit; Monachesi, Antonela; Monelli, Matteo; de Boer, Thomas J. L.; Johnson, L. Clifton; Zaritsky, Dennis; Stringfellow, Guy S.; van der Marel, Roeland P.; Cioni, Maria-Rosa L.; Jin, Shoko; Majewski, Steven R.; Martinez-Delgado, David; Monteagudo, Lara; Noël, Noelia E. D.; Bernard, Edouard J.; Kunder, Andrea; Chu, You-Hua; Bell, Cameron P. M.; Santana, Felipe; Frechem, Joshua; Medina, Gustavo E.; Parkash, Vaishali; Serón Navarrete, J. C.; Hayes, Christian

    2017-11-01

    The Large and Small Magellanic Clouds are unique local laboratories for studying the formation and evolution of small galaxies in exquisite detail. The Survey of the MAgellanic Stellar History (SMASH) is an NOAO community Dark Energy Camera (DECam) survey of the Clouds mapping 480 deg2 (distributed over ˜2400 square degrees at ˜20% filling factor) to ˜24th mag in ugriz. The primary goals of SMASH are to identify low surface brightness stellar populations associated with the stellar halos and tidal debris of the Clouds, and to derive spatially resolved star formation histories. Here, we present a summary of the survey, its data reduction, and a description of the first public Data Release (DR1). The SMASH DECam data have been reduced with a combination of the NOAO Community Pipeline, the PHOTRED automated point-spread-function photometry pipeline, and custom calibration software. The astrometric precision is ˜15 mas and the accuracy is ˜2 mas with respect to the Gaia reference frame. The photometric precision is ˜0.5%-0.7% in griz and ˜1% in u with a calibration accuracy of ˜1.3% in all bands. The median 5σ point source depths in ugriz are 23.9, 24.8, 24.5, 24.2, and 23.5 mag. The SMASH data have already been used to discover the Hydra II Milky Way satellite, the SMASH 1 old globular cluster likely associated with the LMC, and extended stellar populations around the LMC out to R ˜ 18.4 kpc. SMASH DR1 contains measurements of ˜100 million objects distributed in 61 fields. A prototype version of the NOAO Data Lab provides data access and exploration tools.

  6. SMASH: Survey of the MAgellanic Stellar History

    Energy Technology Data Exchange (ETDEWEB)

    Nidever, David L.; Olsen, Knut; Blum, Robert D.; Saha, Abhijit [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Walker, Alistair R.; Vivas, A. Katherina [Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena (Chile); Kaleida, Catherine [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Choi, Yumi; Besla, Gurtina; Olszewski, Edward W. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson AZ, 85721 (United States); Conn, Blair C. [Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia); Gruendl, Robert A. [National Center for Supercomputing Applications, 1205 West Clark Street, Urbana, IL 61801 (United States); Bell, Eric F. [Department of Astronomy, University of Michigan, 1085 S. University Avenue, Ann Arbor, MI 48109-1107 (United States); Muñoz, Ricardo R. [Departamento de Astronomía, Universidad de Chile, Camino del Observatorio 1515, Las Condes, Santiago (Chile); Gallart, Carme; Monelli, Matteo [Instituto de Astrofísica de Canarias, La Laguna, Tenerife (Spain); Martin, Nicolas F. [Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, F-67000 Strasbourg (France); Monachesi, Antonela [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany); De Boer, Thomas J. L. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Johnson, L. Clifton, E-mail: dnidever@noao.edu [Center for Astrophysics and Space Sciences, UC San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0424 (United States); and others

    2017-11-01

    The Large and Small Magellanic Clouds are unique local laboratories for studying the formation and evolution of small galaxies in exquisite detail. The Survey of the MAgellanic Stellar History (SMASH) is an NOAO community Dark Energy Camera (DECam) survey of the Clouds mapping 480 deg{sup 2} (distributed over ∼2400 square degrees at ∼20% filling factor) to ∼24th mag in ugriz . The primary goals of SMASH are to identify low surface brightness stellar populations associated with the stellar halos and tidal debris of the Clouds, and to derive spatially resolved star formation histories. Here, we present a summary of the survey, its data reduction, and a description of the first public Data Release (DR1). The SMASH DECam data have been reduced with a combination of the NOAO Community Pipeline, the PHOTRED automated point-spread-function photometry pipeline, and custom calibration software. The astrometric precision is ∼15 mas and the accuracy is ∼2 mas with respect to the Gaia reference frame. The photometric precision is ∼0.5%–0.7% in griz and ∼1% in u with a calibration accuracy of ∼1.3% in all bands. The median 5 σ point source depths in ugriz are 23.9, 24.8, 24.5, 24.2, and 23.5 mag. The SMASH data have already been used to discover the Hydra II Milky Way satellite, the SMASH 1 old globular cluster likely associated with the LMC, and extended stellar populations around the LMC out to R  ∼ 18.4 kpc. SMASH DR1 contains measurements of ∼100 million objects distributed in 61 fields. A prototype version of the NOAO Data Lab provides data access and exploration tools.

  7. Advanced broadband baffle materials

    International Nuclear Information System (INIS)

    Seals, R.D.

    1991-01-01

    In this paper broadband performance characteristics of robust, light-weight, diffuse-absorptive baffle surfaces fabricated from sputter-deposited beryllium on cross-rolled Be ingot sheet material and on Be foam, plasma sprayed beryllium, plasma sprayed boron-on-beryllium, and chemical vapor deposited boron carbide on graphite are described and compared to Martin Black. An overview of the Optics Manufacturing Operations Development and Integration Laboratory (MODIL) Advanced Optical Baffle Program will be discussed

  8. Oscillations of stellar extinction caused by disturbances in the Earth's atmosphere

    International Nuclear Information System (INIS)

    Clarke, D.

    1980-01-01

    Photometry of bright stars has revealed the possible presence of short period oscillations on the extinction by the Earth's atmosphere. From the colour dependence of the observed effects, it is suggested that the waves affect the aerosol contribution to the extinction more than the contribution by air molecules. The size of the effects presents a challenge to pursuing stellar photometry to accuracies of the order of 0.001 mag. The effects have parallels to the recently discovered brightness oscillations in the daytime sky which have been ascribed to buoyancy or gravity waves in the atmosphere. (author)

  9. Photographic infrared spectroscopy and near infrared photometry of Be stars

    International Nuclear Information System (INIS)

    Swings, J.P.

    1976-01-01

    Two topics are tackled in this presentation: spectroscopy and photometry. The following definitions are chosen: photographic infrared spectroscopy (wavelengths Hα<=lambda<1.2 μ); near infrared photometry (wavebands: 1.6 μ<=lambda<=20 μ). Near infrared spectroscopy and photometry of classical and peculiar Be stars are discussed and some future developments in the field are outlined. (Auth.)

  10. Photometry and polarimetry of Nova Andromedae 1986

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, Sen; Mikami, Yoshitaka; Kondo, Masayuki

    1988-01-01

    We have carried out photometry of Nova Andromedae 1986 and find that it should be classified as a fast nova. We have also made polarimetry simultaneously at six wavelengths between 0.36-0.70 ..mu..m. The polarization increased between 2 and 22 days after the light maximum showing that dust formation was associated with the nova explosion.

  11. L' AND M' Photometry Of Ultracool Dwarfs

    National Research Council Canada - National Science Library

    Marley, M

    2004-01-01

    We have compiled L' (3.4-4.1 microns) and M' (4.6-4.8 microns) photometry of 63 single and binary M, L, and T dwarfs obtained at the United Kingdom Infrared Telescope using the Mauna Kea Observatory filter set...

  12. Compact stellarators as reactors

    International Nuclear Information System (INIS)

    Lyon, J.F.; Valanju, P.; Zarnstorff, M.C.; Hirshman, S.; Spong, D.A.; Strickler, D.; Williamson, D.E.; Ware, A.

    2001-01-01

    Two types of compact stellarators are examined as reactors: two- and three-field-period (M=2 and 3) quasi-axisymmetric devices with volume-average =4-5% and M=2 and 3 quasi-poloidal devices with =10-15%. These low-aspect-ratio stellarator-tokamak hybrids differ from conventional stellarators in their use of the plasma-generated bootstrap current to supplement the poloidal field from external coils. Using the ARIES-AT model with B max =12T on the coils gives Compact Stellarator reactors with R=7.3-8.2m, a factor of 2-3 smaller R than other stellarator reactors for the same assumptions, and neutron wall loadings up to 3.7MWm -2 . (author)

  13. Broadband Radio Service (BRS) and Educational Broadband Service (EBS) Transmitters

    Data.gov (United States)

    Department of Homeland Security — The Broadband Radio Service (BRS), formerly known as the Multipoint Distribution Service (MDS)/Multichannel Multipoint Distribution Service (MMDS), is a commercial...

  14. Multicolor photometry of the nearby galaxy cluster A119

    International Nuclear Information System (INIS)

    Tian Jintao; Zhou Xu; Jiang Zhaoji; Ma Jun; Wu Zhenyu; Fan Zhou; Zhang Tianmeng; Zou Hu; Yuan Qirong; Wu Jianghua

    2012-01-01

    This paper presents multicolor optical photometry of the nearby galaxy cluster Abell 119 (z = 0.0442) with the Beijing-Arizona-Taiwan-Connecticut system of 15 intermediate bands. Within the BATC field of view of 58' × 58', there are 368 galaxies with known spectroscopic redshifts, including 238 member galaxies (called sample I). Based on the spectral energy distributions of 1376 galaxies brighter than i BATC = 19.5, the photometric redshift technique and the color-magnitude relation of early-type galaxies are applied to select faint member galaxies. As a result, 117 faint galaxies were selected as new member galaxies. Combined with sample I, an enlarged sample (called sample II) of 355 member galaxies is obtained. Spatial distribution and localized velocity structure for two samples demonstrate that A119 is a dynamically complex cluster with at least three prominent substructures in the central region within 1 Mpc. A large velocity dispersion for the central clump indicates a merging along the line of sight. No significant evidence for morphology or luminosity segregations is found in either sample. With the PEGASE evolutionary synthesis model, the environmental effect on the properties of star formation is confirmed. Faint galaxies in the low-density region tend to have longer time scales of star formation, smaller mean stellar ages, and lower metallicities in their interstellar medium, which is in agreement with the context of the hierarchical cosmological scenario. (research papers)

  15. Calibration of the MACHO Photometry Database

    International Nuclear Information System (INIS)

    Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Geha, M.

    1999-01-01

    The MACHO Project is a microlensing survey that monitors the brightnesses of ∼60 million stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud, and Galactic bulge. Our database presently contains about 80 billion photometric measurements, a significant fraction of all astronomical photometry. We describe the calibration of MACHO two-color photometry and transformation to the standard Kron-Cousins V and R system. Calibrated MACHO photometry may be properly compared with all other observations on the Kron-Cousins standard system, enhancing the astrophysical value of these data. For ∼9 million stars in the LMC bar, independent photometric measurements of ∼20,000 stars with V(less-or-similar sign)18 mag in field-overlap regions demonstrate an internal precision σ V =0.021, σ R =0.019, σ V-R =0.028 mag. The accuracy of the zero point in this calibration is estimated to be ±0.035 mag for stars with colors in the range -0.1 mag< V-R<1.2 mag. A comparison of calibrated MACHO photometry with published photometric sequences and new Hubble Space Telescope observations shows agreement. The current calibration zero-point uncertainty for the remainder of the MACHO photometry database is estimated to be ±0.10 mag in V or R and ±0.04 mag in V-R. We describe the first application of calibrated MACHO data: the construction of a color-magnitude diagram used to calculate our experimental sensitivity for detecting microlensing in the LMC. (c) (c) 1999. The Astronomical Society of the Pacific

  16. Calibration of the MACHO Photometry Database

    Energy Technology Data Exchange (ETDEWEB)

    Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Geha, M. (and others)

    1999-12-01

    The MACHO Project is a microlensing survey that monitors the brightnesses of {approx}60 million stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud, and Galactic bulge. Our database presently contains about 80 billion photometric measurements, a significant fraction of all astronomical photometry. We describe the calibration of MACHO two-color photometry and transformation to the standard Kron-Cousins V and R system. Calibrated MACHO photometry may be properly compared with all other observations on the Kron-Cousins standard system, enhancing the astrophysical value of these data. For {approx}9 million stars in the LMC bar, independent photometric measurements of {approx}20,000 stars with V(less-or-similar sign)18 mag in field-overlap regions demonstrate an internal precision {sigma}{sub V} =0.021, {sigma}{sub R} =0.019, {sigma}{sub V-R} =0.028 mag. The accuracy of the zero point in this calibration is estimated to be {+-}0.035 mag for stars with colors in the range -0.1 magphotometry with published photometric sequences and new Hubble Space Telescope observations shows agreement. The current calibration zero-point uncertainty for the remainder of the MACHO photometry database is estimated to be {+-}0.10 mag in V or R and {+-}0.04 mag in V-R. We describe the first application of calibrated MACHO data: the construction of a color-magnitude diagram used to calculate our experimental sensitivity for detecting microlensing in the LMC. (c) (c) 1999. The Astronomical Society of the Pacific.

  17. VizieR Online Data Catalog: From optical to infrared photometry of SN 2013dy (Pan+, 2015)

    Science.gov (United States)

    Pan, Y.-C.; Foley, R. J.; Kromer, M.; Fox, O. D.; Zheng, W.; Challis, P.; Clubb, K. I.; Filippenko, A. V.; Folatelli, G.; Graham, M. L.; Hillebrandt, W.; Kirshner, R. P.; Lee, W. H.; Pakmor, R.; Patat, F.; Phillips, M. M.; Pignata, G.; Ropke, F.; Seitenzahl, I.; Silverman, J. M.; Simon, J. D.; Sternberg, A.; Stritzinger, M. D.; Taubenberger, S.; Vinko, J.; Wheeler, J. C.

    2017-11-01

    We obtained broad-band BVRI photometry of SN 2013dy with the 0.76m Katzman Automatic Imaging Telescope (KAIT; Filippenko et al. 2001ASPC..246..121F). The multiband images were observed with the KAIT4 filter set from -16d to +337d relative to B-band maximum (MJD=56501.105). We also obtained riZYJH photometry of SN 2013dy with the multichannel Reionization And Transients InfraRed camera (RATIR; Butler et al. 2012SPIE.8446E..10B) mounted on the 1.5m Johnson telescope at the Mexican Observatorio Astronomico Nacional on Sierra San Pedro Martir in Baja California, Mexico (Watson et al. 2012SPIE.8444E..5LW). Typical observations include a series of 80s exposures in the ri bands and 60s exposures in the ZYJH bands, with dithering between exposures. (2 data files).

  18. A standard stellar library for evolutionary synthesis. III. Metallicity calibration

    Science.gov (United States)

    Westera, P.; Lejeune, T.; Buser, R.; Cuisinier, F.; Bruzual, G.

    2002-01-01

    We extend the colour calibration of the widely used BaSeL standard stellar library (Lejeune et al. 1997, 1998) to non-solar metallicities, down to [Fe/H] ~ -2.0 dex. Surprisingly, we find that at the present epoch it is virtually impossible to establish a unique calibration of UBVRIJHKL colours in terms of stellar metallicity [Fe/H] which is consistent simultaneously with both colour-temperature relations and colour-absolute magnitude diagrams (CMDs) based on observed globular cluster photometry data and on published, currently popular standard stellar evolutionary tracks and isochrones. The problem appears to be related to the long-standing incompleteness in our understanding of convection in late-type stellar evolution, but is also due to a serious lack of relevant observational calibration data that would help resolve, or at least further significant progress towards resolving this issue. In view of the most important applications of the BaSeL library, we here propose two different metallicity calibration versions: (1) the ``WLBC 99'' library, which consistently matches empirical colour-temperature relations and which, therefore, should make an ideal tool for the study of individual stars; and (2), the ``PADOVA 2000'' library, which provides isochrones from the Padova 2000 grid (Girardi et al. \\cite{padova}) that successfully reproduce Galactic globular-cluster colour-absolute magnitude diagrams and which thus should prove particularly useful for studies of collective phenomena in stellar populations in clusters and galaxies.

  19. Handheld Broadband Electromagnetic UXO Sensor

    National Research Council Canada - National Science Library

    Won, I. J; San Filipo, William A; Marqusee, Jeffrey; Andrews, Anne; Robitaille, George; Fairbanks, Jeffrey; Overbay, Larry

    2005-01-01

    The broadband electromagnetic sensor improvement and demonstration undertaken in this project took the prototype GEM-3 and evolved it into an operational sensor with increased bandwidth and dynamic...

  20. BRITE Constellation: data processing and photometry

    Science.gov (United States)

    Popowicz, A.; Pigulski, A.; Bernacki, K.; Kuschnig, R.; Pablo, H.; Ramiaramanantsoa, T.; Zocłońska, E.; Baade, D.; Handler, G.; Moffat, A. F. J.; Wade, G. A.; Neiner, C.; Rucinski, S. M.; Weiss, W. W.; Koudelka, O.; Orleański, P.; Schwarzenberg-Czerny, A.; Zwintz, K.

    2017-09-01

    Context. The BRIght Target Explorer (BRITE) mission is a pioneering space project aimed at the long-term photometric monitoring of the brightest stars in the sky by means of a constellation of nanosatellites. Its main advantage is high photometric accuracy and time coverage which are inaccessible from the ground. Its main drawback is the lack of cooling of the CCD detectors and the absence of good shielding that would protect them from energetic particles. Aims: The main aim of this paper is the presentation of procedures used to obtain high-precision photometry from a series of images acquired by the BRITE satellites in two modes of observing, stare and chopping. The other aim is a comparison of the photometry obtained with two different pipelines and a comparison of the real scatter with expectations. Methods: We developed two pipelines corresponding to the two modes of observing. They are based on aperture photometry with a constant aperture, circular for stare mode of observing and thresholded for chopping mode. Impulsive noise is a serious problem for observations made in the stare mode of observing and therefore in the pipeline developed for observations made in this mode, hot pixels are replaced using the information from shifted images in a series obtained during a single orbit of a satellite. In the other pipeline, the hot pixel replacement is not required because the photometry is made in difference images. Results: The assessment of the performance of both pipelines is presented. It is based on two comparisons, which use data from six runs of the UniBRITE satellite: (I) comparison of photometry obtained by both pipelines on the same data, which were partly affected by charge transfer inefficiency (CTI), (II) comparison of real scatter with theoretical expectations. It is shown that for CTI-affected observations, the chopping pipeline provides much better photometry than the other pipeline. For other observations, the results are comparable only for data

  1. Stellarator-Spheromak

    International Nuclear Information System (INIS)

    Moroz, P.E.

    1997-03-01

    A novel concept for magnetic plasma confinement, Stellarator-Spheromak (SSP), is proposed. Numerical analysis with the classical-stellarator-type outboard stellarator windings demonstrates a number of potential advantages of SSP for controlled nuclear fusion. Among the main ones are: simple and compact magnet coil configuration, absence of material structures (e.g. magnet coils or conducting walls) in the center of the torus, high rotational transform, and a possibility of MHD equilibria with very high β (pressure/magnetic pressure) of the confined plasma

  2. Double-helix stellarator

    International Nuclear Information System (INIS)

    Moroz, P.E.

    1997-09-01

    A new stellarator configuration, the Double-Helix Stellarator (DHS), is introduced. This novel configuration features a double-helix center post as the only helical element of the stellarator coil system. The DHS configuration has many unique characteristics. One of them is the extreme low plasma aspect ratio, A ∼ 1--1.2. Other advantages include a high enclosed volume, appreciable rotational transform, and a possibility of extreme-high-β MHD equilibria. Moreover, the DHS features improved transport characteristics caused by the absence of the magnetic field ripple on the outboard of the torus. Compactness, simplicity and modularity of the coil system add to the DHS advantages for fusion applications

  3. Optical Monitoring of Young Stellar Objects

    Science.gov (United States)

    Kar, Aman; Jang-Condell, Hannah; Kasper, David; Findlay, Joseph; Kobulnicky, Henry A.

    2018-06-01

    Observing Young Stellar Objects (YSOs) for variability in different wavelengths enables us to understand the evolution and structure of the protoplanetary disks around stars. The stars observed in this project are known YSOs that show variability in the Infrared. Targets were selected from the Spitzer Space Telescope Young Stellar Object Variability (YSOVAR) Program, which monitored star-forming regions in the mid-infrared. The goal of our project is to investigate any correlation between the variability in the infrared versus the optical. Infrared variability of YSOs is associated with the heating of the protoplanetary disk while accretion signatures are observed in the H-alpha region. We used the University of Wyoming’s Red Buttes Observatory to monitor these stars for signs of accretion using an H-alpha narrowband filter and the Johnson-Cousins filter set, over the Summer of 2017. We perform relative photometry and inspect for an image-to-image variation by observing these targets for a period of four months every two to three nights. The study helps us better understand the link between accretion and H-alpha activity and establish a disk-star connection.

  4. Infrared Extinction and Stellar Populations in the Milky Way Midplane

    Science.gov (United States)

    Zasowski, Gail; Majewski, S. R.; Benjamin, R. A.; Nidever, D. L.; Skrutskie, M. F.; Indebetouw, R.; Patterson, R. J.; Meade, M. R.; Whitney, B. A.; Babler, B.; Churchwell, E.; Watson, C.

    2012-01-01

    The primary laboratory for developing and testing models of galaxy formation, structure, and evolution is our own Milky Way, the closest large galaxy and the only one in which we can resolve large numbers of individual stars. The recent availability of extensive stellar surveys, particularly infrared ones, has enabled precise, contiguous measurement of large-scale Galactic properties, a major improvement over inferences based on selected, but scattered, sightlines. However, our ability to fully exploit the Milky Way as a galactic laboratory is severely hampered by the fact that its midplane and central bulge -- where most of the Galactic stellar mass lies -- is heavily obscured by interstellar dust. Therefore, proper consideration of the interstellar extinction is crucial. This thesis describes a new extinction-correction method (the RJCE method) that measures the foreground extinction towards each star and, in many cases, enables recovery of its intrinsic stellar type. We have demonstrated the RJCE Method's validity and used it to produce new, reliable extinction maps of the heavily-reddened Galactic midplane. Taking advantage of the recovered stellar type information, we have generated maps probing the extinction at different heliocentric distances, thus yielding information on the elusive three-dimensional distribution of the interstellar dust. We also performed a study of the interstellar extinction law itself which revealed variations previously undetected in the diffuse ISM and established constraints on models of ISM grain formation and evolution. Furthermore, we undertook a study of large-scale stellar structure in the inner Galaxy -- the bar(s), bulge(s), and inner spiral arms. We used observed and extinction-corrected infrared photometry to map the coherent stellar features in these heavily-obscured parts of the Galaxy, placing constraints on models of the central stellar mass distribution.

  5. Wimps and stellar structure

    International Nuclear Information System (INIS)

    Bouquet, A.; Salati, P.

    1988-01-01

    We present the results of an analytic approximation to compute the effects of WIMPs on stellar structures in a self-consistent way. We examine in particular the case of the Sun and of horizontal branch stars

  6. Principles of Stellar Interferometry

    CERN Document Server

    Glindemann, Andreas

    2011-01-01

    Over the last decade, stellar interferometry has developed from a specialist tool to a mainstream observing technique, attracting scientists whose research benefits from milliarcsecond angular resolution. Stellar interferometry has become part of the astronomer’s toolbox, complementing single-telescope observations by providing unique capabilities that will advance astronomical research. This carefully written book is intended to provide a solid understanding of the principles of stellar interferometry to students starting an astronomical research project in this field or to develop instruments and to astronomers using interferometry but who are not interferometrists per se. Illustrated by excellent drawings and calculated graphs the imaging process in stellar interferometers is explained starting from first principles on light propagation and diffraction wave propagation through turbulence is described in detail using Kolmogorov statistics the impact of turbulence on the imaging process is discussed both f...

  7. Convection and stellar oscillations

    DEFF Research Database (Denmark)

    Aarslev, Magnus Johan

    2017-01-01

    for asteroseismology, because of the challenges inherent in modelling turbulent convection in 1D stellar models. As a result of oversimplifying the physics near the surface, theoretical calculations systematically overestimate the oscillation frequencies. This has become known as the asteroseismic surface effect. Due...... to lacking better options, this frequency difference is typically corrected for with ad-hoc formulae. The topic of this thesis is the improvement of 1D stellar convection models and the effects this has on asteroseismic properties. The source of improvements is 3D simulations of radiation...... atmospheres to replace the outer layers of stellar models. The additional turbulent pressure and asymmetrical opacity effects in the atmosphere model, compared to convection in stellar evolution models, serve to expand the atmosphere. The enlarged acoustic cavity lowers the pulsation frequencies bringing them...

  8. Dust Production of Comet 21P/Giacobini Zinner Using Broadband Photometry

    Science.gov (United States)

    Blaauw, Rhiannon; Suggs, Robert M.; Cooke, William

    2012-01-01

    Comet 21P/Giacobini-Zinner is a Jupiter family comet that was discovered in December of 1900 by the French astronomer Michel Giacobini, and rediscovered two orbits later by German astronomer Ernst Zinner in 1913. 21P is approximately 2 km in diameter, and is the parent of the Draconids, a meteor shower known to undergo dramatic outbursts. In 1933 and 1946, up to 10,000 meteors per hour were reported for the Draconids; and 2011 saw a minor Draconid outburst. As meteor stream modeling/ forecasting is a primary focus for the NASA Meteoroid Environment Office, it was decided to monitor 21P for three purposes: firstly to find the apparent and absolute magnitude with respect to heliocentric distance; second to calculate Af(rho), a quantity that describes the dust production rate and is used in models to predict the activity of the Draconids; thirdly to detect possible increases in cometary activity, which could correspond to future Draconid meteor outbursts. Giacobini-Zinner is unique in several ways. It was the first comet to have measurements made in situ. Comet 21P was visited by ICE (International Cometary Explorer) in 1985 to study the interaction of the cometary atmosphere with the flowing solar-wind plasma. It is a carbon-depleted comet, and most studies show that it peaks in gas and dust production pre-perihelion, specifically in two very studied passages; 1985 and 1998. A prior study was conducted by Pittichova et al (2008) for 21P during its 2004-2006 close approach to the Sun. Apparent and absolute magnitudes were measured at various heliocentric distances as well as the dust production. At 2.32 AU from the Sun, 21P exhibited an apparent magnitude of 17.05 and Af of 83 cm, and an apparent magnitude of 15.91/Af(rho) of 130.66 cm at 1.76 AU. Another such study performed by Lara et al.on 21P s 1998 apparition found values of Af(rho) of 1010 cm when 1.05 AU from the Sun, two weeks before perihelion, and 669 cm at perihelion, when 1.03 AU from the Sun

  9. Dust Production of Comet 21P/Giacobini-Zinner Using Broadband Photometry

    Science.gov (United States)

    Blaauw, R. C.; Suggs, R. M.; Cooke, W.

    2012-01-01

    Comet 21P/Giacobini-Zinner is a Jupiter family comet, approximately 2 km in diameter, and is established to be the parent of the Draconids, a meteor shower known to outburst. In 1933 and 1946 up to 10,000 meteors per hour were reported for the Draconids, and 2011 saw a minor Draconid outburst. Meteor stream modeling/forecasting being a primary focus for the NASA Meteoroid Environment Office, it was decided to monitor 21P for three purposes: firstly to find the apparent and absolute magnitude with respect to heliocentric distance; second to calculate Af , a quantity that describes the dust production rate and is used in models to predict the activity of the Draconids; and thirdly to detect possible increases in cometary activity, which could correspond to future Draconid meteor outbursts. A similar study was done for 21P during its 2004-2006 close approach to the Sun in which apparent and absolute magnitudes were found with various heliocentric distances, as well as the dust production. At 2.32 AU from the Sun, 21P possessed an apparent magnitude of 17.05 and Af of 83 cm, and an apparent magnitude of 15.91 and Af of 130.66 cm at 1.76 AU from the sun.

  10. NEW BV(RI)C PHOTOMETRY FOR PRAESEPE: FURTHER TESTS OF BROADBAND PHOTOMETRIC CONSISTENCY

    International Nuclear Information System (INIS)

    Joner, Michael D.; Taylor, Benjamin J.; Laney, C. David; Van Wyk, Francois

    2011-01-01

    New BV(RI) C measurements of Praesepe made at the South African Astronomical Observatory (SAAO) are presented. When those measurements are combined with those reported in previous papers in this series, it is found that they support previously determined V zero points for Praesepe, M67, and the Hyades. Support is also found for joint (V – R) C and (R – I) C zero points established previously for Praesepe and NGC 752. For the SAAO system of standard stars, a B – V correction to the Johnson system of about –9 mmag appears to be reasonably well established. The preferred (though not definitive) V correction is about +7 mmag. For the Landolt V system, zero-point identity with the Johnson system at a 2σ level of 4.8 mmag is found, and no color term as large as 4 mmag (mag) –1 is detected. Updated CDS data files for Praesepe are briefly described.

  11. Oscillations in stellar atmospheres

    International Nuclear Information System (INIS)

    Costa, A.; Ringuelet, A.E.; Fontenla, J.M.

    1989-01-01

    Atmospheric excitation and propagation of oscillations are analyzed for typical pulsating stars. The linear, plane-parallel approach for the pulsating atmosphere gives a local description of the phenomenon. From the local analysis of oscillations, the minimum frequencies are obtained for radially propagating waves. The comparison of the minimum frequencies obtained for a variety of stellar types is in good agreement with the observed periods of the oscillations. The role of the atmosphere in the globar stellar pulsations is thus emphasized. 7 refs

  12. Photometric Separation of Stellar Properties Using SDSS Filters

    Science.gov (United States)

    Lenz, Dawn D.; Newberg, Jo; Rosner, Robert; Richards, Gordon T.; Stoughton, Chris

    1998-12-01

    Using synthetic photometry of Kurucz model spectra, we explore the colors of stars as a function of temperature, metallicity, and surface gravity with Sloan Digital Sky Survey (SDSS) filters, u'g'r'i'z'. The synthetic colors show qualitative agreement with the few published observations in these filters. We find that the locus of synthetic stars is basically two-dimensional for 4500 advantageous to use more than two colors when determining stellar properties by color. Strategic observations in SDSS filters are required to resolve the source of a ~5% discrepancy between synthetic colors of Gunn-Stryker stars, Kurucz models, and external determinations of the metallicities and surface gravities. The synthetic star colors can be used to investigate the properties of any normal star and to construct analytic expressions for the photometric prediction of stellar properties in special cases.

  13. A Photometric Machine-Learning Method to Infer Stellar Metallicity

    Science.gov (United States)

    Miller, Adam A.

    2015-01-01

    Following its formation, a star's metal content is one of the few factors that can significantly alter its evolution. Measurements of stellar metallicity ([Fe/H]) typically require a spectrum, but spectroscopic surveys are limited to a few x 10(exp 6) targets; photometric surveys, on the other hand, have detected > 10(exp 9) stars. I present a new machine-learning method to predict [Fe/H] from photometric colors measured by the Sloan Digital Sky Survey (SDSS). The training set consists of approx. 120,000 stars with SDSS photometry and reliable [Fe/H] measurements from the SEGUE Stellar Parameters Pipeline (SSPP). For bright stars (g' learning method is similar to the scatter in [Fe/H] measurements from low-resolution spectra..

  14. A Photometric Machine-Learning Method to Infer Stellar Metallicity

    Science.gov (United States)

    Miller, Adam A.

    2015-01-01

    Following its formation, a star's metal content is one of the few factors that can significantly alter its evolution. Measurements of stellar metallicity ([Fe/H]) typically require a spectrum, but spectroscopic surveys are limited to a few x 10(exp 6) targets; photometric surveys, on the other hand, have detected > 10(exp 9) stars. I present a new machine-learning method to predict [Fe/H] from photometric colors measured by the Sloan Digital Sky Survey (SDSS). The training set consists of approx. 120,000 stars with SDSS photometry and reliable [Fe/H] measurements from the SEGUE Stellar Parameters Pipeline (SSPP). For bright stars (g' machine-learning method is similar to the scatter in [Fe/H] measurements from low-resolution spectra..

  15. Laser flare photometry in clinical practice

    Directory of Open Access Journals (Sweden)

    Yury S Astakhov

    2016-06-01

    Full Text Available Laser flare photometry (LFP is the only quantitative and objective method for the evaluation of aqueous flare. There are numerous opportunities to use LFP in clinical practice, and they are discussed in the paper. It is especially helpful in management of uveitis patients, because it allows estimating the correct diagnosis, managing the patient during the treatment with noninvasive method and predicting relapses and complications.

  16. Improved moving source photometry with TRIPPy

    Science.gov (United States)

    Alexandersen, Mike; Fraser, Wesley Cristopher

    2017-10-01

    Photometry of moving sources is more complicated than for stationary sources, because the sources trail their signal out over more pixels than a point source of the same magnitude. Using a circular aperture of same size as would be appropriate for point sources can cut out a large amount of flux if a moving source moves substantially relative to the size of the aperture during the exposure, resulting in underestimated fluxes. Using a large circular aperture can mitigate this issue at the cost of a significantly reduced signal to noise compared to a point source, as a result of the inclusion of a larger background region within the aperture.Trailed Image Photometry in Python (TRIPPy) solves this problem by using a pill-shaped aperture: the traditional circular aperture is sliced in half perpendicular to the direction of motion and separated by a rectangle as long as the total motion of the source during the exposure. TRIPPy can also calculate the appropriate aperture correction (which will depend both on the radius and trail length of the pill-shaped aperture), and has features for selecting good PSF stars, creating a PSF model (convolved moffat profile + lookup table) and selecting a custom sky-background area in order to ensure no other sources contribute to the background estimate.In this poster, we present an overview of the TRIPPy features and demonstrate the improvements resulting from using TRIPPy compared to photometry obtained by other methods with examples from real projects where TRIPPy has been implemented in order to obtain the best-possible photometric measurements of Solar System objects. While TRIPPy has currently mainly been used for Trans-Neptunian Objects, the improvement from using the pill-shaped aperture increases with source motion, making TRIPPy highly relevant for asteroid and centaur photometry as well.

  17. Determination of palladium by flame photometry

    International Nuclear Information System (INIS)

    Parellada Bellod, R.

    1964-01-01

    A study on the determination of palladium by lame photometry, fixing the most convent experimental conditions and using solvents to increase the emission of this elements is carried out. Among the organic solvents, acetone has been found the most efficient. The interferences produced by anions and cations have also been studied and an analytical method is related, in which lines of calibration of 0 to 100 ppm palladium re used. (Author) 7 refs

  18. Lightcurve Photometry Opportunities: 2018 April-June

    Science.gov (United States)

    Warner, Brian D.; Harris, Alan W.; Durech, Josef; Benner, Lance A. M.

    2018-04-01

    We present lists of asteroid photometry opportunities for objects reaching a favorable apparition and having either none or poorly-defined lightcurve parameters. Additional data on these objects will help with shape and spin axis modeling via lightcurve inversion. We also include lists of objects that will be the target of radar observations. Lightcurves for these objects can help constrain pole solutions and/or remove rotation period ambiguities that might not come from using radar data alone.

  19. Thirteen-colour photometry of Be stars

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, M; Schuster, W J [Universidad Nacional Autonoma de Mexico, Mexico City. Inst. de Astronomia

    1981-01-01

    Thirteen-colour photometry made at the San Pedro Martir Observatory in Baja California, for a number of spectroscopically variable Be and shell stars is presented. Several of these stars also show photometric variability in the ultraviolet and/or infrared over a time base of two to three years. We analyze the more interesting stars in terms of colour-colour diagrams, colour excesses, spectral characteristics and changes in their energy distributions. Prospects for future research are discussed.

  20. Optical photometry of TX0506+056

    Science.gov (United States)

    Keel, William; Santander, Marcos

    2017-10-01

    The blazar TX0506+056 has attracted recent attention through its location in the error box of a high-energy Ice Cube neutrino detection (https://gcn.gsfc.nasa.gov/gcn3/21916.gcn3) and gamma-ray flaring (Atel #10791) We report recent photometry of TX0506+056 obtained in Johnson V and Cousins R passbands using the 1-meter Kapteyn telescope at La Palma, operated remotely by the SARA consortium.

  1. Recent photometry of selected symbiotic stars

    Science.gov (United States)

    Vrašťák, M.

    2018-04-01

    A new multicolour (BVRcIc) photometric observations of symbiotic stars UV Aur, YY Her, V443 Her, V1016 Cyg, PU Vul, V407 Cyg, V471 Per and suspected symbiotic stars ZZ CMi, NQ Gem, V934 Her, V335 Vul, V627 Cas is presented. The data were obtained from 2016 October to 2018 January by the metod of classical CCD photometry. The monitoring program is still running, so on this paper partial light curves are presented.

  2. Thirteen-colour photometry of Be stars

    International Nuclear Information System (INIS)

    Alvarez, M.; Schuster, W.J.

    1981-01-01

    Thirteen-colour photometry made at the San Pedro Martir Observatory in Baja California, for a number of spectroscopically variable Be and shell stars is presented. Several of these stars also show photometric variability in the ultraviolet and/or infrared over a time base of two to three years. We analyze the more interesting stars in terms of colour-colour diagrams, colour excesses, spectral characteristics and changes in their energy distributions. Prospects for future research are discussed. (author)

  3. WISE PHOTOMETRY FOR 400 MILLION SDSS SOURCES

    International Nuclear Information System (INIS)

    Lang, Dustin; Hogg, David W.; Schlegel, David J.

    2016-01-01

    We present photometry of images from the Wide-Field Infrared Survey Explorer (WISE) of over 400 million sources detected by the Sloan Digital Sky Survey (SDSS). We use a “forced photometry” technique, using measured SDSS source positions, star–galaxy classification, and galaxy profiles to define the sources whose fluxes are to be measured in the WISE images. We perform photometry with The Tractor image modeling code, working on our “unWISE” coaddds and taking account of the WISE point-spread function and a noise model. The result is a measurement of the flux of each SDSS source in each WISE band. Many sources have little flux in the WISE bands, so often the measurements we report are consistent with zero given our uncertainties. However, for many sources we get 3σ or 4σ measurements; these sources would not be reported by the “official” WISE pipeline and will not appear in the WISE catalog, yet they can be highly informative for some scientific questions. In addition, these small-signal measurements can be used in stacking analyses at the catalog level. The forced photometry approach has the advantage that we measure a consistent set of sources between SDSS and WISE, taking advantage of the resolution and depth of the SDSS images to interpret the WISE images; objects that are resolved in SDSS but blended together in WISE still have accurate measurements in our photometry. Our results, and the code used to produce them, are publicly available at http://unwise.me

  4. An Assessment of Emerging Wireless Broadband Technologies

    National Research Council Canada - National Science Library

    Fountanas, Leonidas

    2001-01-01

    ... technologies in providing broadband services today, emerging wireless broadband technologies are expected to significantly increase their market share over the next years, Deploying a wireless network...

  5. A tidally stripped stellar component of the Magellanic bridge

    Energy Technology Data Exchange (ETDEWEB)

    Nidever, David L.; Monachesi, Antonela; Bell, Eric F. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48104 (United States); Majewski, Steven R.; Beaton, Rachael L. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States); Muñoz, Ricardo R., E-mail: dnidever@umich.edu, E-mail: rmunoz@das.uchile.cl [Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago (Chile)

    2013-12-20

    Deep photometry of the Small Magellanic Cloud (SMC) stellar periphery (R = 4°, 4.2 kpc) is used to study its line-of-sight depth with red clump (RC) stars. The RC luminosity function is affected little by young (≲1 Gyr) blue-loop stars in these regions because their main-sequence counterparts are not observed in the color-magnitude diagrams. The SMCs eastern side is found to have a large line-of-sight depth (∼23 kpc) while the western side has a much shallower depth (∼10 kpc), consistent with previous photographic plate photometry results. We use a model SMC RC luminosity function to deconvolve the observed RC magnitudes and construct the density function in distance for our fields. Three of the eastern fields show a distance bimodality with one component at the 'systemic' ∼67 kpc SMC distance and a second component at ∼55 kpc. Our data are not reproduced well by the various extant Magellanic Cloud and Stream simulations. However, the models predict that the known H I Magellanic Bridge (stretching from the SMC eastward toward the Large Magellanic Cloud, LMC) has a decreasing distance with angle from the SMC and should be seen in both the gaseous and stellar components. From comparison with these models, we conclude that the most likely explanation for our newly identified ∼55 kpc stellar structure in the eastern SMC is a stellar counterpart of the H I Magellanic Bridge that was tidally stripped from the SMC ∼200 Myr ago during a close encounter with the LMC. This discovery has important implications for microlensing surveys of the SMC.

  6. Broadband unidirectional ultrasound propagation

    Science.gov (United States)

    Sinha, Dipen N.; Pantea, Cristian

    2017-12-12

    A passive, linear arrangement of a sonic crystal-based apparatus and method including a 1D sonic crystal, a nonlinear medium, and an acoustic low-pass filter, for permitting unidirectional broadband ultrasound propagation as a collimated beam for underwater, air or other fluid communication, are described. The signal to be transmitted is first used to modulate a high-frequency ultrasonic carrier wave which is directed into the sonic crystal side of the apparatus. The apparatus processes the modulated signal, whereby the original low-frequency signal exits the apparatus as a collimated beam on the side of the apparatus opposite the sonic crystal. The sonic crystal provides a bandpass acoustic filter through which the modulated high-frequency ultrasonic signal passes, and the nonlinear medium demodulates the modulated signal and recovers the low-frequency sound beam. The low-pass filter removes remaining high-frequency components, and contributes to the unidirectional property of the apparatus.

  7. Deriving Stellar Masses for the ALFALFA α.100 Sample

    Science.gov (United States)

    Hess, Logan; Cornell 2017 Summer REU

    2018-01-01

    For this project, we explore different methods of deriving the stellar masses of galaxies in the ALFALFA (Arecibo Legacy Fast ALFA) α.100 survey. In particular, we measure the effectiveness of SED (Spectral Energy Distribution) on the sample. SED fitting was preformed by MAGPHYS (Multi-wavelength Analysis of Galaxy Physical Properties), utilizing a wide range of photometry in the UV, optical, and IR bands. Photometry was taken from GALAX GR6/7 (UV), SDSS DR13 (optical), WISE All-Sky (near-IR), and Herschel PACS/SPIRE (far-IR). The efficiency of SED fitting increases with a broader range of photometry, however detection rates varied significantly across the different bands. Using a more “comprehensive” sample of galaxies, the GSWLC-A (GALAX, SDSS, WISE Legacy Catalog All-Sky Survey), we aimed to measure which combination of bands provided the largest sample return with the lowest amount of uncertainty, which could then be used to estimate the masses of the galaxies in the α.100 sample.

  8. Discovering transits of HD 209458-b type planets with Hipparcos and FAME photometry

    Science.gov (United States)

    Castellano, Timothy Paul

    The motivation and prospects for success of a search for transits of short-period extrasolar planets of late-type main sequence stars in the Hipparcos satellite photometry archive is outlined. Recent extrasolar planet discoveries by the radial velocity (RV) method reveal that 1 in 20 spectral type F, G and K dwarfs possess short-period planets. Careful consideration of the transit detection probability as a function of stellar spectral type and planet orbit size results in the expectation that 6 to 24 transiting planets may be found among the 118,204 Hipparcos catalog stars. A search algorithm based on the known properties of the single known transiting extrasolar planet HD 209458-b was applied to carefully- selected samples of stars. The results of these searches and simulations of the detection efficiency for idealized transits are presented. Statistical and catalog-based methods for discriminating transits from intrinsic stellar variability and eclipses due to stellar companions are developed and described. Candidate lists that are the results of these searches are presented. Each candidate is placed in a color magnitude diagram based on Hipparcos derived distances and absolute magnitudes in order to clearly identify evolved stars. The effect of Lutz-Kelker bias on this main sequence membership determination is discussed in an Appendix. A Hipparcos-photometry-based intrinsic stellar variability determination is performed and compared to ground-based measurements. It is shown that intrinsic stellar variability of late-type main sequence stars is not a major concern for extrasolar jovian planet transit searches. The prospects for transit detection by the higher precision measurements of several hundred thousand main sequence stars to be made by the upcoming Full Sky Astrometric Explorer (FAME) satellite are similarly explored. A novel method for directly determining the mass of a transiting planet's parent star from timing measurements is introduced briefly in an

  9. PREFACE: A Stellar Journey A Stellar Journey

    Science.gov (United States)

    Asplund, M.

    2008-10-01

    The conference A Stellar Journey was held in Uppsala, Sweden, 23 27June 2008, in honour of Professor Bengt Gustafsson's 65th birthday. The choice of Uppsala as the location for this event was obvious given Bengt's long-standing association with the city stemming back to his school days. With the exception of a two-year postdoc stint in Copenhagen, five years as professor at Stockholm University and two years as director of the Sigtuna foundation, Bengt has forged his illustrious professional career at Uppsala University. The symposium venue was Museum Gustavianum, once the main building of the oldest university in Scandinavia. The title of the symposium is a paraphrasing of Bengt's popular astronomy book Kosmisk Resa (in English: Cosmic Journey) written in the early eighties. I think this aptly symbolizes his career that has been an astronomical voyage from near to far, from the distant past to the present. The original book title was modified slightly to reflect that most of his work to date has dealt with stars in one way or another. In addition it also gives credit to Bengt's important role as a guiding light for a very large number of students, colleagues and collaborators, indeed for several generations of astronomers. For me personally, the book Kosmisk Resa bears particular significance as it has shaped my life rather profoundly. Although I had already decided to become an astronomer, when I first read the book as a 14-year-old I made up my mind then and there that I would study under Bengt Gustafsson and work on stars. Indeed I have remained true to this somewhat audacious resolution. I suspect that a great number of us have similar stories how Bengt has had a major influence on our lives, whether on the professional or personal level. Perhaps Bengt's most outstanding characteristic is his enthralling enthusiasm. This is equally true whether he is pondering some scientific conundrum, supervising students or performing in front of an audience, be it an

  10. Stellar magnetic activity

    International Nuclear Information System (INIS)

    Schrijver, C.J.

    1986-01-01

    The stellar emission in the chromospheric Ca II H+K lines is compared with the coronal soft X-ray emission, measuring the effects of non-radiative heating in the outer atmosphere at temperatures differing two orders of magnitude. The comparison of stellar flux densities in Ca II H+K and X-rays is extended to fluxes from the transition-region and the high-temperature chromosphere. The stellar magnetic field is probably generated in the differentially rotating convective envelope. The relation between rotation rate and the stellar level of activity measured in chromospheric, transition-region, and coronal radiative diagnostics is discovered. X-ray observations of the binary λ Andromedae are discussed. The departure of M-type dwarfs from the main relations, and the implications for the structure of the chromospheres of these stars are discussed. Variations of the average surface flux densities of the Sun during the 11-year activity cycle agree with flux-flux relations derived for other cool stars, suggesting that the interpretation of the stellar relations may be furthered by studying the solar analogue in more detail. (Auth.)

  11. USING STELLAR DENSITIES TO EVALUATE TRANSITING EXOPLANETARY CANDIDATES

    International Nuclear Information System (INIS)

    Tingley, B.; Deeg, H. J.; Bonomo, A. S.

    2011-01-01

    One of the persistent complications in searches for transiting exoplanets is the low percentage of the detected candidates that ultimately prove to be planets, which significantly increases the load on the telescopes used for the follow-up observations to confirm or reject candidates. Several attempts have been made at creating techniques that can pare down candidate lists without the need of additional observations. Some of these techniques involve a detailed analysis of light curve characteristics; others estimate the stellar density or some proxy thereof. In this paper, we extend upon this second approach, exploring the use of independently calculated stellar densities to identify the most promising transiting exoplanet candidates. We use a set of CoRoT candidates and the set of known transiting exoplanets to examine the potential of this approach. In particular, we note the possibilities inherent in the high-precision photometry from space missions, which can detect stellar asteroseismic pulsations from which accurate stellar densities can be extracted without additional observations.

  12. Exploring Algorithms for Stellar Light Curves With TESS

    Science.gov (United States)

    Buzasi, Derek

    2018-01-01

    The Kepler and K2 missions have produced tens of thousands of stellar light curves, which have been used to measure rotation periods, characterize photometric activity levels, and explore phenomena such as differential rotation. The quasi-periodic nature of rotational light curves, combined with the potential presence of additional periodicities not due to rotation, complicates the analysis of these time series and makes characterization of uncertainties difficult. A variety of algorithms have been used for the extraction of rotational signals, including autocorrelation functions, discrete Fourier transforms, Lomb-Scargle periodograms, wavelet transforms, and the Hilbert-Huang transform. In addition, in the case of K2 a number of different pipelines have been used to produce initial detrended light curves from the raw image frames.In the near future, TESS photometry, particularly that deriving from the full-frame images, will dramatically further expand the number of such light curves, but details of the pipeline to be used to produce photometry from the FFIs remain under development. K2 data offers us an opportunity to explore the utility of different reduction and analysis tool combinations applied to these astrophysically important tasks. In this work, we apply a wide range of algorithms to light curves produced by a number of popular K2 pipeline products to better understand the advantages and limitations of each approach and provide guidance for the most reliable and most efficient analysis of TESS stellar data.

  13. The Resolved Stellar Populations Early Release Science Program

    Science.gov (United States)

    Weisz, Daniel; Anderson, J.; Boyer, M.; Cole, A.; Dolphin, A.; Geha, M.; Kalirai, J.; Kallivayalil, N.; McQuinn, K.; Sandstrom, K.; Williams, B.

    2017-11-01

    We propose to obtain deep multi-band NIRCam and NIRISS imaging of three resolved stellar systems within 1 Mpc (NOI 104). We will use this broad science program to optimize observational setups and to develop data reduction techniques that will be common to JWST studies of resolved stellar populations. We will combine our expertise in HST resolved star studies with these observations to design, test, and release point spread function (PSF) fitting software specific to JWST. PSF photometry is at the heart of resolved stellar populations studies, but is not part of the standard JWST reduction pipeline. Our program will establish JWST-optimized methodologies in six scientific areas: star formation histories, measurement of the sub-Solar mass stellar IMF, extinction maps, evolved stars, proper motions, and globular clusters, all of which will be common pursuits for JWST in the local Universe. Our observations of globular cluster M92, ultra-faint dwarf Draco II, and star-forming dwarf WLM, will be of high archival value for other science such as calibrating stellar evolution models, measuring properties of variable stars, and searching for metal-poor stars. We will release the results of our program, including PSF fitting software, matched HST and JWST catalogs, clear documentation, and step-by-step tutorials (e.g., Jupyter notebooks) for data reduction and science application, to the community prior to the Cycle 2 Call for Proposals. We will host a workshop to help community members plan their Cycle 2 observations of resolved stars. Our program will provide blueprints for the community to efficiently reduce and analyze JWST observations of resolved stellar populations.

  14. Updated 34-band Photometry for the SINGS/KINGFISH Samples of Nearby Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Dale, D. A.; Turner, J. A. [Department of Physics and Astronomy, University of Wyoming, Laramie WY (United States); Cook, D. O. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena CA (United States); Roussel, H. [Institut d’Astrophysique de Paris, Sorbonne Universités, Paris (France); Armus, L.; Helou, G. [Spitzer Science Center, California Institute of Technology, Pasadena, CA (United States); Bolatto, A. D. [Department of Astronomy, University of Maryland, College Park, MD (United States); Boquien, M. [Unidad de Astronomía, Universidad de Antofagasta, Antofagasta (Chile); Brown, M. J. I. [School of Physics and Astronomy, Monash University, Victoria 3800 (Australia); Calzetti, D. [Department of Astronomy, University of Massachusetts, Amherst MA (United States); Looze, I. De [Sterrenkundig Observatorium, Universiteit Gent, Gent (Belgium); Galametz, M. [European Southern Observatory, Garching (Germany); Gordon, K. D. [Space Telescope Science Institute, Baltimore MD (United States); Groves, B. A. [Research School of Astronomy and Astrophysics, Australian National University, Canberra (Australia); Jarrett, T. H. [Astronomy Department, University of Capetown, Rondebosch (South Africa); Herrera-Camus, R. [Max-Planck-Institut für Extraterrestrische Physik, Garching (Germany); Hinz, J. L. [Steward Observatory, University of Arizona, Tucson AZ (United States); Hunt, L. K. [INAF—Osservatorio Astrofisico di Arcetri, Firenze (Italy); Kennicutt, R. C. [Institute of Astronomy, University of Cambridge, Cambridge (United Kingdom); Murphy, E. J., E-mail: ddale@uwyo.edu [National Radio Astronomy Observatory, Charlottesville, VA (United States); and others

    2017-03-01

    We present an update to the ultraviolet-to-radio database of global broadband photometry for the 79 nearby galaxies that comprise the union of the KINGFISH (Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel ) and SINGS ( Spitzer Infrared Nearby Galaxies Survey) samples. The 34-band data set presented here includes contributions from observational work carried out with a variety of facilities including GALEX , SDSS, Pan-STARRS1, NOAO , 2MASS, Wide-Field Infrared Survey Explorer , Spitzer , Herschel , Planck , JCMT , and the VLA. Improvements of note include recalibrations of previously published SINGS BVR {sub C} I {sub C} and KINGFISH far-infrared/submillimeter photometry. Similar to previous results in the literature, an excess of submillimeter emission above model predictions is seen primarily for low-metallicity dwarf or irregular galaxies. This 33-band photometric data set for the combined KINGFISH+SINGS sample serves as an important multiwavelength reference for the variety of galaxies observed at low redshift. A thorough analysis of the observed spectral energy distributions is carried out in a companion paper.

  15. Updated 34-band Photometry for the SINGS/KINGFISH Samples of Nearby Galaxies

    International Nuclear Information System (INIS)

    Dale, D. A.; Turner, J. A.; Cook, D. O.; Roussel, H.; Armus, L.; Helou, G.; Bolatto, A. D.; Boquien, M.; Brown, M. J. I.; Calzetti, D.; Looze, I. De; Galametz, M.; Gordon, K. D.; Groves, B. A.; Jarrett, T. H.; Herrera-Camus, R.; Hinz, J. L.; Hunt, L. K.; Kennicutt, R. C.; Murphy, E. J.

    2017-01-01

    We present an update to the ultraviolet-to-radio database of global broadband photometry for the 79 nearby galaxies that comprise the union of the KINGFISH (Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel ) and SINGS ( Spitzer Infrared Nearby Galaxies Survey) samples. The 34-band data set presented here includes contributions from observational work carried out with a variety of facilities including GALEX , SDSS, Pan-STARRS1, NOAO , 2MASS, Wide-Field Infrared Survey Explorer , Spitzer , Herschel , Planck , JCMT , and the VLA. Improvements of note include recalibrations of previously published SINGS BVR C I C and KINGFISH far-infrared/submillimeter photometry. Similar to previous results in the literature, an excess of submillimeter emission above model predictions is seen primarily for low-metallicity dwarf or irregular galaxies. This 33-band photometric data set for the combined KINGFISH+SINGS sample serves as an important multiwavelength reference for the variety of galaxies observed at low redshift. A thorough analysis of the observed spectral energy distributions is carried out in a companion paper.

  16. PHOTOMETRY AND PHOTOMETRIC REDSHIFT CATALOGS FOR THE LOCKMAN HOLE DEEP FIELD

    International Nuclear Information System (INIS)

    Fotopoulou, S.; Salvato, M.; Hasinger, G.; Rovilos, E.; Brusa, M.; Lutz, D.; Burwitz, V.; Egami, E.; Henry, J. P.; Huang, J. H.; Rigopoulou, D.; Vaccari, M.

    2012-01-01

    We present broadband photometry and photometric redshifts for 187,611 sources located in ∼0.5 deg 2 in the Lockman Hole area. The catalog includes 388 X-ray-detected sources identified with the very deep XMM-Newton observations available for an area of 0.2 deg 2 . The source detection was performed on the R c -, z'-, and B-band images and the available photometry is spanning from the far-ultraviolet to the mid-infrared, reaching in the best-case scenario 21 bands. Astrometry corrections and photometric cross-calibrations over the entire data set allowed the computation of accurate photometric redshifts. Special treatment is undertaken for the X-ray sources, the majority of which are active galactic nuclei (AGNs). For normal galaxies, comparing the photometric redshifts to the 253 available spectroscopic redshifts, we achieve an accuracy of σ Δz/(1+z) = 0.036, with 12.6% outliers. For the X-ray-detected sources, compared to 115 spectroscopic redshifts, the accuracy is σ Δz/(1+z) = 0.069, with 18.3% outliers, where the outliers are defined as sources with |z phot – z spec | > 0.15 × (1 + z spec ). These results are a significant improvement over the previously available photometric redshifts for normal galaxies in the Lockman Hole, while it is the first time that photometric redshifts are computed and made public for AGNs for this field.

  17. Introduction to stellar structure

    CERN Document Server

    Maciel, Walter J

    2016-01-01

    In the first part of this book, the author presents the basic properties of the stellar interior and describes them thoroughly, along with deriving the main stellar structure equations of temperature, density, pressure and luminosity, among others. The process and application of solving these equations is explained, as well as linking these results with actual observations.  The second part of the text describes what happens to a star over time, and how to determine this by solving the same equations at different points during a star’s lifetime. The fate of various stars is quite different depending on their masses, and this is described in the final parts of the book. This text can be used for an upper level undergraduate course or an introductory graduate course on stellar physics.

  18. The Galactic stellar disc

    International Nuclear Information System (INIS)

    Feltzing, S; Bensby, T

    2008-01-01

    The study of the Milky Way stellar discs in the context of galaxy formation is discussed. In particular, we explore the properties of the Milky Way disc using a new sample of about 550 dwarf stars for which we have recently obtained elemental abundances and ages based on high-resolution spectroscopy. For all the stars we also have full kinematic information as well as information about their stellar orbits. We confirm results from previous studies that the thin and the thick discs have distinct abundance patterns. But we also explore a larger range of orbital parameters than what has been possible in our previous studies. Several new results are presented. We find that stars that reach high above the Galactic plane and have eccentric orbits show remarkably tight abundance trends. This implies that these stars formed out of well-mixed gas that had been homogenized over large volumes. We find some evidence that suggest that the event that most likely caused the heating of this stellar population happened a few billion years ago. Through a simple, kinematic exploration of stars with super-solar [Fe/H], we show that the solar neighbourhood contains metal-rich, high velocity stars that are very likely associated with the thick disc. Additionally, the HR1614 moving group and the Hercules and Arcturus stellar streams are discussed and it is concluded that, probably, a large fraction of the groups and streams so far identified in the disc are the result of evolution and interactions within the stellar disc rather than being dissolved stellar clusters or engulfed dwarf galaxies.

  19. Transport in stellarators

    International Nuclear Information System (INIS)

    Maassberg, H.; Brakel, R.; Burhenn, R.; Gasparino, U.; Grigull, P.; Kick, M.; Kuehner, G.; Ringler, H.; Sardei, F.; Stroth, U.; Weller, A.

    1993-01-01

    The local electron and ion heat transport as well as the particle and impurity transport properties in stellarators are reviewed. In this context, neoclassical theory is used as a guideline for the comparison of the experimental results of the quite different confinement concepts. At sufficiently high temperatures depending on the specific magnetic configuration, neoclassical predictions are confirmed by experimental findings. The confinement properties in the LMFP collisionality regime are discussed with respect to the next stellarator generation, for which at higher temperatures the neoclassical transport is expected to become more important. (orig.)

  20. Solar and stellar oscillations

    International Nuclear Information System (INIS)

    Fossat, E.

    1981-01-01

    We try to explain in simple words what a stellar oscillation is, what kind of restoring forces and excitation mechanisms can be responsible for its occurence, what kind of questions the theoretician asks to the observer and what kind of tools the latter is using to look for the answers. A selected review of the most striking results obtained in the last few years in solar seismology and the present status of their consequences on solar models is presented. A brief discussion on the expected extension towards stellar seismology will end the paper. A selected bibliography on theory as well as observations and recent papers is also included. (orig.)

  1. Stroemgren photometry of southern white dwarfs

    International Nuclear Information System (INIS)

    Bessell, M.S.; Wickramasinghe, D.T.

    1978-01-01

    Colours of southern white dwarfs in the uvby (Stroemgren four-colour) system have been obtained. The results are compared with those of Graham. The extensive absolute photometry of white dwarfs published by Greenstein has also been transferred into the four-colour system and both sets of results are compared with model atmosphere calculations. The scatter in log (g) is higher than previously supposed, and the evidence for an increase in at the cooler (Tsub(e) < 10 000 K) end of the DA sequence is discussed. (author)

  2. Broadband accelerator control network

    International Nuclear Information System (INIS)

    Skelly, J.; Clifford, T.; Frankel, R.

    1983-01-01

    A broadband data communications network has been implemented at BNL for control of the Alternating Gradient Synchrotron (AG) proton accelerator, using commercial CATV hardware, dual coaxial cables as the communications medium, and spanning 2.0 km. A 4 MHz bandwidth Digital Control channel using CSMA-CA protocol is provided for digital data transmission, with 8 access nodes available over the length of the RELWAY. Each node consists of an rf modem and a microprocessor-based store-and-forward message handler which interfaces the RELWAY to a branch line implemented in GPIB. A gateway to the RELWAY control channel for the (preexisting) AGS Computerized Accelerator Operating system has been constructed using an LSI-11/23 microprocessor as a device in a GPIB branch line. A multilayer communications protocol has been defined for the Digital Control Channel, based on the ISO Open Systems Interconnect layered model, and a RELWAY Device Language defined as the required universal language for device control on this channel

  3. The fundamentals of stellar astrophysics

    International Nuclear Information System (INIS)

    Collins, G.W. II.

    1989-01-01

    A broad overview of theoretical stellar astrophysics is presented in a textbook intended for graduate students. Chapters are devoted to fundamental principles, assumptions, theorems, and polytropes; energy sources and sinks; the flow of energy through the star and the construction of stellar models; the theory of stellar evolution; relativistic stellar structure; the structure of distorted stars; stellar pulsation and oscillation. Also discussed are the flow of radiation through the stellar atmosphere, the solution of the radiative-transfer equation, the environment of the radiation field, the construction of a stellar model atmosphere, the formation and shape of spectral lines, LTE breakdown, illuminated and extended stellar atmospheres, and the transfer of polarized radiation. Diagrams, graphs, and sample problems are provided. 164 refs

  4. Being WISE. I. Validating stellar population models and M */L ratios at 3.4 and 4.6 μm

    International Nuclear Information System (INIS)

    Norris, Mark A.; Meidt, Sharon; Van de Ven, Glenn; Schinnerer, Eva; Groves, Brent; Querejeta, Miguel

    2014-01-01

    Using data from the Wide-field Infrared Survey Explorer mission, we have measured near infra-red (NIR) photometry of a diverse sample of dust-free stellar systems (globular clusters, dwarf and giant early-type galaxies) which have metallicities that span the range -2.2 < [Fe/H] (dex) < 0.3. This dramatically increases the sample size and broadens the metallicity regime over which the 3.4 (W1) and 4.6 μm (W2) photometry of stellar populations have been examined. We find that the W1 – W2 colors of intermediate and old (>2 Gyr) stellar populations are insensitive to the age of the stellar population, but that the W1 – W2 colors become bluer with increasing metallicity, a trend not well reproduced by most stellar population synthesis (SPS) models. In common with previous studies, we attribute this behavior to the increasing strength of the CO absorption feature located in the 4.6 μm bandpass with metallicity. Having used our sample to validate the efficacy of some of the SPS models, we use these models to derive stellar mass-to-light ratios in the W1 and W2 bands. Utilizing observational data from the SAURON and ATLAS3D surveys, we demonstrate that these bands provide extremely simple, yet robust stellar mass tracers for dust free older stellar populations that are freed from many of the uncertainties common among optical estimators.

  5. Being WISE. I. Validating stellar population models and M {sub *}/L ratios at 3.4 and 4.6 μm

    Energy Technology Data Exchange (ETDEWEB)

    Norris, Mark A.; Meidt, Sharon; Van de Ven, Glenn; Schinnerer, Eva; Groves, Brent; Querejeta, Miguel, E-mail: norris@mpia.de [Max Planck Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany)

    2014-12-10

    Using data from the Wide-field Infrared Survey Explorer mission, we have measured near infra-red (NIR) photometry of a diverse sample of dust-free stellar systems (globular clusters, dwarf and giant early-type galaxies) which have metallicities that span the range -2.2 < [Fe/H] (dex) < 0.3. This dramatically increases the sample size and broadens the metallicity regime over which the 3.4 (W1) and 4.6 μm (W2) photometry of stellar populations have been examined. We find that the W1 – W2 colors of intermediate and old (>2 Gyr) stellar populations are insensitive to the age of the stellar population, but that the W1 – W2 colors become bluer with increasing metallicity, a trend not well reproduced by most stellar population synthesis (SPS) models. In common with previous studies, we attribute this behavior to the increasing strength of the CO absorption feature located in the 4.6 μm bandpass with metallicity. Having used our sample to validate the efficacy of some of the SPS models, we use these models to derive stellar mass-to-light ratios in the W1 and W2 bands. Utilizing observational data from the SAURON and ATLAS3D surveys, we demonstrate that these bands provide extremely simple, yet robust stellar mass tracers for dust free older stellar populations that are freed from many of the uncertainties common among optical estimators.

  6. Progress Toward Attractive Stellarators

    International Nuclear Information System (INIS)

    Neilson, G.H.; Bromberg, L.; Brown, T.G.; Gates, D.A.; Ku, L.P.; Zarnstorff, M.C.; Boozer, A.H.; Harris, J.H.; Meneghini, O.; Mynick, H.E.; Pomphrey, N.; Reiman, A.H.; Xanthopoulos, P.

    2011-01-01

    The quasi-axisymmetric stellarator (QAS) concept offers a promising path to a more compact stellarator reactor, closer in linear dimensions to tokamak reactors than previous stellarator designs. Concept improvements are needed, however, to make it more maintainable and more compatible with high plant availability. Using the ARIES-CS design as a starting point, compact stellarator designs with improved maintenance characteristics have been developed. While the ARIES-CS features a through-the-port maintenance scheme, we have investigated configuration changes to enable a sector-maintenance approach, as envisioned for example in ARIES AT. Three approaches are reported. The first is to make tradeoffs within the QAS design space, giving greater emphasis to maintainability criteria. The second approach is to improve the optimization tools to more accurately and efficiently target the physics properties of importance. The third is to employ a hybrid coil topology, so that the plasma shaping functions of the main coils are shared more optimally, either with passive conductors made of high-temperature superconductor or with local compensation coils, allowing the main coils to become simpler. Optimization tools are being improved to test these approaches.

  7. Stellar population synthesis

    International Nuclear Information System (INIS)

    Pickles, A.J.

    1989-01-01

    The techniques used to derive astrophysically useful information from observations of the integrated light of composite stellar systems are briefly reviewed. A synthesis technique, designed to separate and describe on a standard system the competing effects of age and metallicity variations is introduced, and illustrated by its application to the study of the history of star formation in bright elliptical galaxies in clusters. (author)

  8. Relativistic stellar dynamics

    International Nuclear Information System (INIS)

    Contopoulos, G.

    1983-01-01

    In this paper, three main areas of relativistic stellar dynamics are reviewed: (a) The dynamics of clusters, or nuclei of galaxies, of very high density; (b) The dynamics of systems containing a massive black hole; and (c) The dynamics of particles (and photons) in an expanding Universe. The emphasis is on the use of orbit perturbations. (Auth.)

  9. Compact stellarator coils

    International Nuclear Information System (INIS)

    Pomphrey, N.; Berry, L.A.; Boozer, A.H.

    2001-01-01

    Experimental devices to study the physics of high-beta (β>∼4%), low aspect ratio (A<∼4.5) stellarator plasmas require coils that will produce plasmas satisfying a set of physics goals, provide experimental flexibility, and be practical to construct. In the course of designing a flexible coil set for the National Compact Stellarator Experiment, we have made several innovations that may be useful in future stellarator design efforts. These include: the use of Singular Value Decomposition methods for obtaining families of smooth current potentials on distant coil winding surfaces from which low current density solutions may be identified; the use of a Control Matrix Method for identifying which few of the many detailed elements of the stellarator boundary must be targeted if a coil set is to provide fields to control the essential physics of the plasma; the use of Genetic Algorithms for choosing an optimal set of discrete coils from a continuum of potential contours; the evaluation of alternate coil topologies for balancing the tradeoff between physics objective and engineering constraints; the development of a new coil optimization code for designing modular coils, and the identification of a 'natural' basis for describing current sheet distributions. (author)

  10. Stellar Structure and Evolution

    CERN Document Server

    Kippenhahn, Rudolf; Weiss, Achim

    2013-01-01

    This long-awaited second edition of the classical textbook on Stellar Structure and Evolution by Kippenhahn and Weigert is a thoroughly revised version of the original text. Taking into account modern observational constraints as well as additional physical effects such as mass loss and diffusion, Achim Weiss and Rudolf Kippenhahn have succeeded in bringing the book up to the state-of-the-art with respect to both the presentation of stellar physics and the presentation and interpretation of current sophisticated stellar models. The well-received and proven pedagogical approach of the first edition has been retained. The book provides a comprehensive treatment of the physics of the stellar interior and the underlying fundamental processes and parameters. The models developed to explain the stability, dynamics and evolution of the stars are presented and great care is taken to detail the various stages in a star’s life. Just as the first edition, which remained a standard work for more than 20 years after its...

  11. 8. stellarator workshop

    International Nuclear Information System (INIS)

    1991-07-01

    The technical reports in this collection of papers were presented at the 8th International Workshop on Stellarators, and International Atomic Energy Agency Technical Committee Meeting. They include presentations on transport, magnetic configurations, fluctuations, equilibrium, stability, edge plasma and wall aspects, heating, diagnostics, new concepts and reactor studies. Refs, figs and tabs

  12. The ATLAS3D project - XXI. Correlations between gradients of local escape velocity and stellar populations in early-type galaxies

    NARCIS (Netherlands)

    Scott, Nicholas; Cappellari, Michele; Davies, Roger L.; Kleijn, Gijs Verdoes; Bois, Maxime; Alatalo, Katherine; Blitz, Leo; Bournaud, Frédéric; Bureau, Martin; Crocker, Alison; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnović, Davor; Kuntschner, Harald; McDermid, Richard M.; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M.

    We explore the connection between the local escape velocity, Vesc, and the stellar population properties in the ATLAS3D survey, a complete, volume-limited sample of nearby early-type galaxies. We make use of ugriz photometry to construct Multi-Gaussian Expansion models of the surface brightnesses of

  13. The ATLAS(3D) project : XXI. Correlations between gradients of local escape velocity and stellar populations in early-type galaxies

    NARCIS (Netherlands)

    Scott, Nicholas; Cappellari, Michele; Davies, Roger L.; Kleijn, Gijs Verdoes; Bois, Maxime; Alatalo, Katherine; Blitz, Leo; Bournaud, Frederic; Bureau, Martin; Crocker, Alison; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnovic, Davor; Kuntschner, Harald; McDermid, Richard M.; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M.

    2013-01-01

    We explore the connection between the local escape velocity, V-esc, and the stellar population properties in the ATLAS(3D) survey, a complete, volume-limited sample of nearby early-type galaxies. We make use of ugriz photometry to construct Multi-Gaussian Expansion models of the surface brightnesses

  14. Photometry of Southern Hemisphere red dwarf stars

    Science.gov (United States)

    Weistrop, D.

    1980-01-01

    Results are presented for a photometric investigation of a spectroscopically selected sample of red dwarf stars in the Southern Hemisphere. Absolute magnitudes and distances for the stars are estimated from broadband red colors. Three stars which may be subluminous are identified, as are several stars which may be within 25 pc. The tangential velocity and velocity dispersion of the sample are similar to values found in other studies of nearby late-type stars.

  15. Stellar wind theory

    International Nuclear Information System (INIS)

    Summers, D.

    1980-01-01

    The theory of stellar winds as given by the equations of classical fluid dynamics is considered. The equations of momentum and energy describing a steady, spherically symmetric, heat-conducting, viscous stellar wind are cast in a dimensionless form which involves a thermal conduction parameter E and a viscosity parameter γ. An asymptotic analysis is carried out, for fixed γ, in the cases E→O and E→infinity (corresponding to small and large thermal conductivity, respectively), and it is found that it is possible to construct critical solutions for the wind velocity and temperature over the entire flow. The E→O solution represents a wind which emanates from the star at low, subsonic speeds, accelerates through a sonic point, and then approaches a constant asymptotic speed, with its temperature varying as r/sup -4/3/ at large distances r from the star; the E→infinity solution represents a wind which, after reaching an approximately constant speed, with temperature varying as r/sup -2/7/, decelerates through a diffuse shock and approaches a finite pressure at infinity. A categorization is made of all critical stellar wind solutions for given values of γ and E, and actual numerical examples are given. Numerical solutions are obtained by integrating upstream 'from infinity' from initial values of the flow parameters given by appropriate asymptotic expansions. The role of viscosity in stellar wind theory is discussed, viscous and inviscid stellar wind solutions are compared, and it is suggested that with certain limitations, the theory presented may be useful in analyzing winds from solar-type stars

  16. Flatfielding Errors in Strömvil CCD Photometry

    Directory of Open Access Journals (Sweden)

    Boyle R. P.

    2003-12-01

    Full Text Available The importance of determining the error of the flat field in CCD photometry is detailed and our methods of doing this are described. We now have reached a precision of 1-1.5 % in our photometry. Color-magnitude diagrams of the open cluster M67 (ours and Laugalys et al. 2003 are compared.

  17. Broadband Rotational Spectroscopy

    Science.gov (United States)

    Pate, Brooks

    2014-06-01

    The past decade has seen several major technology advances in electronics operating at microwave frequencies making it possible to develop a new generation of spectrometers for molecular rotational spectroscopy. High-speed digital electronics, both arbitrary waveform generators and digitizers, continue on a Moore's Law-like development cycle that started around 1993 with device bandwidth doubling about every 36 months. These enabling technologies were the key to designing chirped-pulse Fourier transform microwave (CP-FTMW) spectrometers which offer significant sensitivity enhancements for broadband spectrum acquisition in molecular rotational spectroscopy. A special feature of the chirped-pulse spectrometer design is that it is easily implemented at low frequency (below 8 GHz) where Balle-Flygare type spectrometers with Fabry-Perot cavity designs become technologically challenging due to the mirror size requirements. The capabilities of CP-FTMW spectrometers for studies of molecular structure will be illustrated by the collaborative research effort we have been a part of to determine the structures of water clusters - a project which has identified clusters up to the pentadecamer. A second technology trend that impacts molecular rotational spectroscopy is the development of high power, solid state sources in the mm-wave/THz regions. Results from the field of mm-wave chirped-pulse Fourier transform spectroscopy will be described with an emphasis on new problems in chemical dynamics and analytical chemistry that these methods can tackle. The third (and potentially most important) technological trend is the reduction of microwave components to chip level using monolithic microwave integrated circuits (MMIC) - a technology driven by an enormous mass market in communications. Some recent advances in rotational spectrometer designs that incorporate low-cost components will be highlighted. The challenge to the high-resolution spectroscopy community - as posed by Frank De

  18. A PSF photometry tool for NASA's Kepler, K2, and TESS missions

    Science.gov (United States)

    Cardoso, Jose Vinicius De Miranda; Barentsen, Geert; Hedges, Christina L.; Gully-Santiago, Michael A.; Cody, Ann Marie; Montet, Ben

    2018-01-01

    NASA's Kepler and K2 missions have impacted all areas of astrophysics in unique and important ways by delivering high-precision time series data on asteroids, stars, and galaxies. For example, both the official Kepler pipeline and the various community-owned pipelines have been successful at discovering a myriad of transiting exoplanets around a wide range of stellar types. However, the existing pipelines tend to focus on studying isolated stars using simple aperture photometry, and often perform sub-optimally in crowded fields where objects are blended. To address this issue, we present a Point Spread Function (PSF) photometry toolkit for Kepler and K2 which is able to extract light curves from crowded regions, such as the Beehive Cluster, the Lagoon Nebula, and the M67 globular cluster, which were all recently observed by Kepler. We present a detailed discussion on the theory, the practical use, and demonstrate our tool on various levels of crowding. Finally, we discuss the future use of the tool on data from the TESS mission. The code is open source and available on GitHub as part of the PyKE toolkit for Kepler/K2 data analysis.

  19. Compact Starburst Galaxies with Fast Outflows: Spatially Resolved Stellar Mass Profiles

    Science.gov (United States)

    Gottlieb, Sophia; Diamond-Stanic, Aleksandar; Lipscomb, Charles; Ohene, Senyo; Rines, Josh; Moustakas, John; Sell, Paul; Tremonti, Christy; Coil, Alison; Rudnick, Gregory; Hickox, Ryan C.; Geach, James; Kepley, Amanda

    2018-01-01

    Powerful galactic winds driven by stellar feedback and black hole accretion are thought to play an important role in regulating star formation in galaxies. In particular, strong stellar feedback from supernovae, stellar winds, radiation pressure, and cosmic rays is required by simulations of star-forming galaxies to prevent the vast majority of baryons from cooling and collapsing to form stars. However, it remains unclear whether these stellar processes play a significant role in expelling gas and shutting down star formation in massive progenitors of quiescent galaxies. What are the limits of stellar feedback? We present multi-band photometry with HST/WFC3 (F475W, F814W, F160W) for a dozen compact starburst galaxies at z~0.6 with half-light radii that suggest incredibly large central escape velocities. These massive galaxies are driving fast (>1000 km/s) outflows that have been previously attributed to stellar feedback associated with the compact (r~100 pc) starburst. But how compact is the stellar mass? In the context of the stellar feedback hypothesis, it is unclear whether these fast outflows are being driven at velocities comparable to the escape velocity of an incredibly dense stellar system (as predicted by some models of radiation-pressure winds) or at velocities that exceed the central escape velocity by large factor. Our spatially resolved measurements with HST show that the stellar mass is more extended than the light, and this requires that the physical mechanism responsible for driving the winds must be able to launch gas at velocities that are factors of 5-10 beyond the central escape velocity.

  20. Driving demand for broadband networks and services

    CERN Document Server

    Katz, Raul L

    2014-01-01

    This book examines the reasons why various groups around the world choose not to adopt broadband services and evaluates strategies to stimulate the demand that will lead to increased broadband use. It introduces readers to the benefits of higher adoption rates while examining the progress that developed and emerging countries have made in stimulating broadband demand. By relying on concepts such as a supply and demand gap, broadband price elasticity, and demand promotion, this book explains differences between the fixed and mobile broadband demand gap, introducing the notions of substitution and complementarity between both platforms. Building on these concepts, ‘Driving Demand for Broadband Networks and Services’ offers a set of best practices and recommendations aimed at promoting broadband demand.  The broadband demand gap is defined as individuals and households that could buy a broadband subscription because they live in areas served by telecommunications carriers but do not do so because of either ...

  1. Massive stellar content of some Galactic supershells

    Science.gov (United States)

    Kaltcheva, Nadejda; Golev, Valeri

    2015-08-01

    The giant Galactic H II regions provide a unique opportunity to study the OB-star influence on the surrounding interstellar matter. In this contribution, several multi-wavelength surveys (Wisconsin H-α Mapper Northern Sky Survey, Southern H-α Sky Survey Atlas, MSX Mid-IR Galactic Plane Survey, WISE All-Sky Data Release, CO survey of the Milky Way, and the Southern Galactic Plane HI Survey) are combined with available intermediate-band uvbyβ photometry to attempt a precise spatial correlation between the OB-stars and the neutral and ionized material. Our study is focused on the H I supershell GSH 305+01-24 in Centaurus, the Car OB2 supershell, the Cygnus star-forming complex and the GSH 224-01+24 shell toward the GMN 39/Seagull nebula region. We refine the massive stellar content of these star-forming fields and study the energetics of its interaction with the shells’ material.

  2. Infrared photometry of cool white dwarfs

    International Nuclear Information System (INIS)

    Wickramasinghe, D.T.; Allen, D.A.; Bessell, M.S.

    1982-01-01

    The results are presented of a search for the effects of pressure induced H 2 dipole opacity on the infrared JHK magnitudes of cool white dwarfs. LHS 1126 is found to be a very cool (Tsub(e) approximately 4250 K) DC white dwarf with a H rich atmospheric composition dominated by H 2 dipole opacity in the infrared. JHK photometry also favours a H rich atmospheric composition for the DK white dwarfs LP 658-2 and W 489. The surprisingly high proportion of hydrogen rich white dwarfs in the sample appears to suggest that the mechanism which inhibits the accretion of hydrogen in the hotter helium stars becomes less effective at low (Tsub(e) approximately 3 + ion in cool hydrogen rich white dwarf atmospheres is pointed out and it is suggested that the opacity due to this ion may be responsible for the blanketing observed in the U and B magnitudes of some cool white dwarfs. (author)

  3. Multicolor surface photometry of 17 ellipticals

    International Nuclear Information System (INIS)

    Franx, M.; Illingworth, G.; Heckman, T.

    1989-01-01

    Multicolor two-dimensional surface photometry was used to obtain radial profiles for surface brightness, color, ellipticity, position angle, and the residuals from the fitted ellipses described by the cos(n phi) and sin(n phi) terms (where n = 3 and 4) for 17 elliptical galaxies. It is found that at radii as large as five times the seeing FWHM, seeing can affect the ellipticity at the 10 percent level and introduce uncertainty in the position angles of several degrees, particularly for very round ellipticals. The present profiles are found to agree well with previous data, with rms differences of 0.02 in ellipticity and 2 deg in position angle. The observed color gradients are consistent with a decrease in the metallicity by a factor of about 2 per decade in radius. 61 refs

  4. Direct illumination LED calibration for telescope photometry

    International Nuclear Information System (INIS)

    Barrelet, E.; Juramy, C.

    2008-01-01

    A calibration method for telescope photometry, based on the direct illumination of a telescope with a calibrated light source regrouping multiple LEDs, is proposed. Its purpose is to calibrate the instrument response. The main emphasis of the proposed method is the traceability of the calibration process and a continuous monitoring of the instrument in order to maintain a 0.2% accuracy over a period of years. Its specificity is to map finely the response of the telescope and its camera as a function of all light ray parameters. This feature is essential to implement a computer model of the instrument representing the variation of the overall light collection efficiency of each pixel for various filter configurations. We report on hardware developments done for SNDICE, the first application of this direct illumination calibration system which will be installed in Canada France Hawaii telescope (CFHT) for its leading supernova experiment (SNLS)

  5. Ion transport in stellarators

    International Nuclear Information System (INIS)

    Ho, D.D.M.; Kulsrud, R.M.

    1985-09-01

    Stellarator ion transport in the low-collisionality regime with a radial electric field is calculated by a systematic expansion of the drift-Boltzmann equation. The shape of the helical well is taken into account in this calculation. It is found that the barely trapped ions with three to four times the thermal energy give the dominant contribution to the diffusion. Expressions for the ion particle and energy fluxes are derived

  6. Status of stellarator research

    International Nuclear Information System (INIS)

    Wobig, H.

    1985-01-01

    In recent years main activities in stellarator research were focussed on production and investigation of currentless plasmas. Several heating methods have been applied: electron cyclotron heating, ion cyclotron heating and neutral beam injection. The parameters achieved in HELIOTRON E and W VII-A are: antin 20 m 3 , Tsub(i) <= 1 keV. The confinement is improved as compared with ohmically heated discharges. By ECRH (P = 200 kW) it is possible to heat electrons up to 1.4 keV, confinement in this regime is dominated already by trapped particle effects. Toroidal currents up to 2 kA - either bootstrap currents or externally driven currents - were observed. High β-values (antiβ = 2%) have been obtained in HELIOTRON E, in this regime already pressure driven MHD-modes were observed. Future experiments (ATF-1 and W VII-AS) will extend the parameter regime to temperatures of several keV. These experiments will give important information about critical problems of the stellarator line (β-limit, neoclassical confinement impurity transport). A few reactor studies of stellarators exist, attention is mainly concentrated on technical problems of the modular coil system

  7. Femtosecond Broadband Stimulated Raman Spectroscopy

    International Nuclear Information System (INIS)

    Lee, Soo-Y; Yoon, Sagwoon; Mathies, Richard A

    2006-01-01

    Femtosecond broadband stimulated Raman spectroscopy (FSRS) is a new technique where a narrow bandwidth picosecond Raman pump pulse and a red-shifted broadband femtosecond Stokes probe pulse (with or without time delay between the pulses) act on a sample to produce a high resolution Raman gain spectrum with high efficiency and speed, free from fluorescence background interference. It can reveal vibrational structural information and dynamics of stationary or transient states. Here, the quantum picture for femtosecond broadband stimulated Raman spectroscopy (FSRS) is used to develop the semiclassical coupled wave theory of the phenomenon and to derive an expression for the measurable Raman gain in FSRS. The semiclassical theory is applied to study the dependence of lineshapes in FSRS on the pump-probe time delay and to deduce vibrational dephasing times in cyclohexane in the ground state

  8. Observations involving broadband impedance modelling

    Energy Technology Data Exchange (ETDEWEB)

    Berg, J S [Stanford Linear Accelerator Center, Menlo Park, CA (United States)

    1996-08-01

    Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impedance. This paper discusses three aspects of broadband impedance modelling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f. cavity. The last is a discussion of requirements for the mathematical form of an impedance which follow from the general properties of impedances. (author)

  9. Observations involving broadband impedance modelling

    International Nuclear Information System (INIS)

    Berg, J.S.

    1995-08-01

    Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impendance. This paper discusses three aspects of broadband impendance modeling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f cavity. The last is a discussion of requirements for the mathematical form of an impendance which follow from the general properties of impendances

  10. SMSS J130522.47-293113.0: a high-latitude stellar X-ray source with pc-scale outflow relics?

    Science.gov (United States)

    Da Costa, G. S.; Soria, R.; Farrell, S. A.; Bayliss, D.; Bessell, M. S.; Vogt, F. P. A.; Zhou, G.; Points, S. D.; Beers, T. C.; López-Sánchez, Á. R.; Bannister, K. W.; Bell, M.; Hancock, P. J.; Burlon, D.; Gaensler, B. M.; Sadler, E. M.; Tingay, S.; Keller, S. C.; Schmidt, B. P.; Tisserand, P.

    2018-06-01

    We report the discovery of an unusual stellar system SMSS J130522.47-293113.0. The optical spectrum is dominated by a blue continuum together with emission lines of hydrogen, neutral, and ionized helium, and the N III, C III blend at ˜4640-4650 Å. The emission-line profiles vary in strength and position on time-scales as short as 1 d, while optical photometry reveals fluctuations of as much as ˜0.2 mag in g on time-scales as short as 10-15 min. The system is a weak X-ray source (f0.3-10 = (1.2 ± 0.1) × 10-13 ergs cm2 s-1 in the 0.3-10 keV band) but is not detected at radio wavelengths (3σ upper limit of 50 μJy at 5.5 GHz). The most intriguing property of the system, however, is the existence of two `blobs', a few arcsec in size, that are symmetrically located 3{^'.}8 (2.2 pc for our preferred system distance of ˜2 kpc) each side of the central object. The blobs are detected in optical and near-IR broad-band images but do not show any excess emission in H α images. We discuss the interpretation of the system, suggesting that the central object is most likely a nova-like CV, and that the blobs are relics of a pc-scale accretion-powered collimated outflow.

  11. Extended Aperture Photometry of K2 RR Lyrae stars

    Directory of Open Access Journals (Sweden)

    Plachy Emese

    2017-01-01

    Full Text Available We present the method of the Extended Aperture Photometry (EAP that we applied on K2 RR Lyrae stars. Our aim is to minimize the instrumental variations of attitude control maneuvers by using apertures that cover the positional changes in the field of view thus contain the stars during the whole observation. We present example light curves that we compared to the light curves from the K2 Systematics Correction (K2SC pipeline applied on the automated Single Aperture Photometry (SAP and on the Pre-search Data Conditioning Simple Aperture Photometry (PDCSAP data.

  12. Extended Aperture Photometry of K2 RR Lyrae stars

    Science.gov (United States)

    Plachy, Emese; Klagyivik, Péter; Molnár, László; Sódor, Ádám; Szabó, Róbert

    2017-10-01

    We present the method of the Extended Aperture Photometry (EAP) that we applied on K2 RR Lyrae stars. Our aim is to minimize the instrumental variations of attitude control maneuvers by using apertures that cover the positional changes in the field of view thus contain the stars during the whole observation. We present example light curves that we compared to the light curves from the K2 Systematics Correction (K2SC) pipeline applied on the automated Single Aperture Photometry (SAP) and on the Pre-search Data Conditioning Simple Aperture Photometry (PDCSAP) data.

  13. ASSESSMENT OF STELLAR STRATIFICATION IN THREE YOUNG STAR CLUSTERS IN THE LARGE MAGELLANIC CLOUD

    International Nuclear Information System (INIS)

    Gouliermis, Dimitrios A.; Rochau, Boyke; Mackey, Dougal; Xin Yu

    2010-01-01

    We present a comprehensive study of stellar stratification in young star clusters in the Large Magellanic Cloud (LMC). We apply our recently developed effective radius method for the assessment of stellar stratification on imaging data obtained with the Advanced Camera for Surveys of three young LMC clusters to characterize the phenomenon and develop a comparative scheme for its assessment in such clusters. The clusters of our sample, NGC 1983, NGC 2002, and NGC 2010, are selected on the basis of their youthfulness, and their variety in appearance, structure, stellar content, and surrounding stellar ambient. Our photometry is complete for magnitudes down to m 814 ≅ 23 mag, allowing the calculation of the structural parameters of the clusters, the estimation of their ages, and the determination of their stellar content. Our study shows that each cluster in our sample demonstrates stellar stratification in a quite different manner and at different degree from the others. Specifically, NGC 1983 shows partial segregation, with the effective radius increasing with fainter magnitudes only for the faintest stars of the cluster. Our method on NGC 2002 provides evidence of strong stellar stratification for both bright and faint stars; the cluster demonstrates the phenomenon with the highest degree in the sample. Finally, NGC 2010 is not segregated, as its bright stellar content is not centrally concentrated, the relation of effective radius to magnitude for stars of intermediate brightness is rather flat, and we find no evidence of stratification for its faintest stars. For the parameterization of the phenomenon of stellar stratification and its quantitative comparison among these clusters, we propose the slope derived from the change in the effective radius over the corresponding magnitude range as indicative parameter of the degree of stratification in the clusters. A positive value of this slope indicates mass segregation in the cluster, while a negative or zero value

  14. Achieving universal access to broadband

    DEFF Research Database (Denmark)

    Falch, Morten; Henten, Anders

    2009-01-01

    The paper discusses appropriate policy measures for achieving universal access to broadband services in Europe. Access can be delivered by means of many different technology solutions described in the paper. This means a greater degree of competition and affects the kind of policy measures...

  15. THE ADVANCED STELLAR COMPASS

    DEFF Research Database (Denmark)

    Jørgensen, John Leif; Liebe, Carl Christian

    1997-01-01

    The science objective of the Danish Geomagnetic Research Satellite "Ørsted" is to map the magnetic field of the Earth, with a vector precision of a fraction of a nanotesla. This necessitates an attitude reference instrument with a precision of a few arcseconds onboard the satellite. To meet...... this demand the Advanced Stellar Compass (ASC), a fully autonomous miniature star tracker, was developed. This ASC is capable of both solving the "lost in space" problem and determine the attitude with arcseconds precision. The development, principles of operation and instrument autonomy of the ASC...

  16. Physics of Stellar Convection

    Science.gov (United States)

    Arnett, W. David

    2009-05-01

    We review recent progress using numerical simulations as a testbed for development of a theory of stellar convection, much as envisaged by John von Newmann. Necessary features of the theory, non-locality and fluctuations, are illustrated by computer movies. It is found that the common approximation of convection as a diffusive process presents the wrong physical picture, and improvements are suggested. New observational results discussed at the conference are gratifying in their validation of some of our theoretical ideas, especially the idea that SNIb and SNIc events are related to the explosion of massive star cores which have been stripped by mass loss and binary interactions [1

  17. Near infrared photometry of globular clusters

    International Nuclear Information System (INIS)

    Evans, T.L.; Menzies, J.W.

    1977-01-01

    Photographic photometry on the V, Isub(K) system has been obtained for giant stars in the metal-rich globular clusters NGC 5927, 6171, 6352, 6356, 6388, 6522, 6528, 6712 and 6723. Colour-magnitude diagrams are presented. These data, with earlier observations of NGC 104 (47 Tuc), yield new parameters to describe the giant branch. These are the colour of the red variables, represented by their mean colour (V - Isub(K)) 0 or by the colour (V - Isub(K))sub(BO) of the bluest red variable on the giant branch of a cluster, and ΔV' which is the magnitude difference between the horizontal branch and the highest point on the giant branch. The latter is independent of reddening, since the giant branch of the most metal-rich clusters passes through a maximum in the V, V - Isub(K) plane. These parameters are correlated with the metal content, deduced from integrated photometry: the red variables are redder and the giant branch fainter the higher the metal content. Comparison with theoretical evolutionary tracks suggests that the range in metal content of these clusters is at most a factor of 10, the most metal-rich clusters possibly approaching the solar value. The cluster giant branches and those of open clusters, groups and field stars of the old disk population are compared. The assumption that all the globular clusters have an absolute magnitude on the horizontal branch of Msub(v) = + 0.9, as found recently for 47 Tuc, gives good agreement between the magnitudes of giant stars in the most metal rich of the globular clusters and those of field stars deduced from statistical parallaxes and moving group parallaxes. The values of the parameters ΔV' and (V - Isub(k))sub(BO) also approach those in the moving groups. The globular clusters have a longer horizontal branch, however, and the subgiants are bluer even when the values of ) 7Fe/H{ appear to be the same. (author). )

  18. IRAS 20050+2720: ANATOMY OF A YOUNG STELLAR CLUSTER

    International Nuclear Information System (INIS)

    Günther, H. M.; Wolk, S. J.; Spitzbart, B.; Forbrich, J.; Wright, N. J.; Bourke, T. L.; Gutermuth, R. A.; Allen, L.; Megeath, S. T.; Pipher, J. L.

    2012-01-01

    IRAS 20050+2720 is young star-forming region at a distance of 700 pc without apparent high-mass stars. We present results of our multi-wavelength study of IRAS 20050+2720 which includes observations by Chandra and Spitzer, and Two Micron All Sky Survey and UBVRI photometry. In total, about 300 young stellar objects (YSOs) in different evolutionary stages are found. We characterize the distribution of YSOs in this region using a minimum spanning tree analysis. We newly identify a second cluster core, which consists mostly of class II objects, about 10' from the center of the cloud. YSOs of earlier evolutionary stages are more clustered than more evolved objects. The X-ray luminosity function (XLF) of IRAS 20050+2720 is roughly lognormal, but steeper than the XLF of the more massive Orion Nebula complex. IRAS 20050+2720 shows a lower N H /A K ratio compared with the diffuse interstellar medium.

  19. Stellar axion models

    Energy Technology Data Exchange (ETDEWEB)

    Nowakowski, Daniel; Kuster, Markus; Meister, Claudia V.; Fuelbert, Florian; Hoffmann, Dieter H.H. [TU Darmstadt (Germany). Institut fuer Kernphysik; Weiss, Achim [Max-Planck-Institut fuer Astrophysik, Garching (Germany)

    2010-07-01

    An axion helioscope is typically operated to observe the sun as an axion source. Additional pointings at celestial sources, e.g. stars in other galaxies, result in possible detections of axions from distant galactic objects. For the observation of supplementary axion sources we therefore calculate the thereotical axion flux from distant stars by extending axionic flux models for the axion Primakoff effect in the sun to other main sequence stars. The main sequence star models used for our calculations are based on full stellar structure calculations. To deduce the effective axion flux of stellar objects incident on the Earth the All-Sky catalogue was used to obtain the spectral class and distance of the stars treated. Our calculations of the axion flux in the galactic plane show that for a zero age main sequence star an maximum axion flux of {phi}{sub a}=303.43 cm{sup -2}s{sup -1} could be expected. Furthermore we present estimates of axion fluxes from time-evolved stars.

  20. The DEMO Quasisymmetric Stellarator

    Directory of Open Access Journals (Sweden)

    Geoffrey B. McFadden

    2010-02-01

    Full Text Available The NSTAB nonlinear stability code solves differential equations in conservation form, and the TRAN Monte Carlo test particle code tracks guiding center orbits in a fixed background, to provide simulations of equilibrium, stability, and transport in tokamaks and stellarators. These codes are well correlated with experimental observations and have been validated by convergence studies. Bifurcated 3D solutions of the 2D tokamak problem have been calculated that model persistent disruptions, neoclassical tearing modes (NTMs and edge localized modes (ELMs occurring in the International Thermonuclear Experimental Reactor (ITER, which does not pass the NSTAB simulation test for nonlinear stability. So we have designed a quasiaxially symmetric (QAS stellarator with similar proportions as a candidate for the demonstration (DEMO fusion reactor that does pass the test [1]. The configuration has two field periods and an exceptionally accurate 2D symmetry that furnishes excellent thermal confinement and good control of the prompt loss of alpha particles. Robust coils are found from a filtered form of the Biot-Savart law based on a distribution of current over a control surface for the coils and the current in the plasma defined by the equilibrium calculation. Computational science has addressed the issues of equilibrium, stability, and transport, so it remains to develop an effective plan to construct the coils and build a diverter.

  1. BVI CCD photometry of 47 Tucanae

    International Nuclear Information System (INIS)

    Alcaino, G.; Liller, W.

    1987-01-01

    CCD BVI main-sequence photometry of 47 Tuc is presented, matched to the recent BVI isochrones of VandenBerg and Bell (1985). The main-sequence turnoffs are found to be at V = 17.60 + or - 0.1, B-V = 0.56 + or - 0.02; V-I = 0.68 + or - 0.02, and B-I = 1.24 + or - 0.02. The magnitude difference between the main-sequence turnoff and the horizontal branch is 3.55 + or - 0.15 for all three color indices. A consistent age for 47 Tuc of 17 Gyr and a consistent distance modulus of (m-M)v = 13.2 are obtained for all three indices, and an absolute magnitude of Mv = 0.85 is determined for the horizontal branch stars. The results also favor the adoption of (Fe/H) near -0.5 as the best abundance value for 47 Tuc. 38 references

  2. UBV photometry of 262 southern galaxies

    International Nuclear Information System (INIS)

    Wegner, G.

    1979-01-01

    Multi-aperture photometry of 262 bright southern galaxies in the Johnson UBV system is given. Most of these are south of delta = -30 0 , although some northward to delta = -10 0 are included. A total of 169 objects have published radial velocity determinations. These provide distances, and enable construction of colour-magnitude diagrams for this subset of objects througha physical diameter of 2.0 kpc (with H 0 = 100). The two-colour diagrams for the inner regions of the galaxies differ from those of integrated galaxies due to the colour changes towards their centres. Comparison with theoretical models of Larson and Tinsley (1978) suggest that the colours of the inner portions of most ellipticals and lenticulars are consistent with their having all stars formed at nearly one epoch with little subsequent star formation, while for spirals larger amounts of star formation, either in bursts of continuously, are suggested. This simple picture is complicated by the presence of certain objects having peculiar colours indicative of large amounts of recent star formation. (Auth.)

  3. Circumstellar Disk Lifetimes In Numerous Galactic Young Stellar Clusters

    Science.gov (United States)

    Richert, A. J. W.; Getman, K. V.; Feigelson, E. D.; Kuhn, M. A.; Broos, P. S.; Povich, M. S.; Bate, M. R.; Garmire, G. P.

    2018-04-01

    Photometric detections of dust circumstellar disks around pre-main sequence (PMS) stars, coupled with estimates of stellar ages, provide constraints on the time available for planet formation. Most previous studies on disk longevity, starting with Haisch, Lada & Lada (2001), use star samples from PMS clusters but do not consider datasets with homogeneous photometric sensitivities and/or ages placed on a uniform timescale. Here we conduct the largest study to date of the longevity of inner dust disks using X-ray and 1-8 {μ m} infrared photometry from the MYStIX and SFiNCs projects for 69 young clusters in 32 nearby star-forming regions with ages t ≤ 5 Myr. Cluster ages are derived by combining the empirical AgeJX method with PMS evolutionary models, which treat dynamo-generated magnetic fields in different ways. Leveraging X-ray data to identify disk-free objects, we impose similar stellar mass sensitivity limits for disk-bearing and disk-free YSOs while extending the analysis to stellar masses as low as M ˜ 0.1 M⊙. We find that the disk longevity estimates are strongly affected by the choice of PMS evolutionary model. Assuming a disk fraction of 100% at zero age, the inferred disk half-life changes significantly, from t1/2 ˜ 1.3 - 2 Myr to t1/2 ˜ 3.5 Myr when switching from non-magnetic to magnetic PMS models. In addition, we find no statistically significant evidence that disk fraction varies with stellar mass within the first few Myr of life for stars with masses <2 M⊙, but our samples may not be complete for more massive stars. The effects of initial disk fraction and star-forming environment are also explored.

  4. STELLAR MASSES FROM THE CANDELS SURVEY: THE GOODS-SOUTH AND UDS FIELDS

    International Nuclear Information System (INIS)

    Santini, P.; Fontana, A.; Castellano, M.; Grazian, A.; Amorin, R.; Ferguson, H. C.; Mobasher, B.; Barro, G.; Finkelstein, S. L.; Hsu, L. T.; Salvato, M.; Wuyts, S.; Galametz, A.; Lee, B.; Lee, S.-K.; Pforr, J.; Wiklind, T.; Almaini, O.; Cooper, M. C.; Weiner, B.

    2015-01-01

    We present the public release of the stellar mass catalogs for the GOODS-S and UDS fields obtained using some of the deepest near-IR images available, achieved as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey project. We combine the effort from 10 different teams, who computed the stellar masses using the same photometry and the same redshifts. Each team adopted their preferred fitting code, assumptions, priors, and parameter grid. The combination of results using the same underlying stellar isochrones reduces the systematics associated with the fitting code and other choices. Thanks to the availability of different estimates, we can test the effect of some specific parameters and assumptions on the stellar mass estimate. The choice of the stellar isochrone library turns out to have the largest effect on the galaxy stellar mass estimates, resulting in the largest distributions around the median value (with a semi interquartile range larger than 0.1 dex). On the other hand, for most galaxies, the stellar mass estimates are relatively insensitive to the different parameterizations of the star formation history. The inclusion of nebular emission in the model spectra does not have a significant impact for the majority of galaxies (less than a factor of 2 for ∼80% of the sample). Nevertheless, the stellar mass for the subsample of young galaxies (age <100 Myr), especially in particular redshift ranges (e.g., 2.2 < z < 2.4, 3.2 < z < 3.6, and 5.5 < z < 6.5), can be seriously overestimated (by up to a factor of 10 for <20 Myr sources) if nebular contribution is ignored

  5. STELLAR MASSES FROM THE CANDELS SURVEY: THE GOODS-SOUTH AND UDS FIELDS

    Energy Technology Data Exchange (ETDEWEB)

    Santini, P.; Fontana, A.; Castellano, M.; Grazian, A.; Amorin, R. [INAF-Osservatorio Astronomico di Roma, via di Frascati 33, I-00040 Monte Porzio Catone, Roma (Italy); Ferguson, H. C. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Mobasher, B. [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Barro, G. [UCO/Lick Observatory and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Finkelstein, S. L. [Department of Astronomy, The University of Texas at Austin, Austin, TX 78712 (United States); Hsu, L. T.; Salvato, M.; Wuyts, S.; Galametz, A. [Max-Planck-Institut für Extraterrestrische Physik (MPE), Postfach 1312, D-85741 Garching (Germany); Lee, B. [Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States); Lee, S.-K. [Center for the Exploration of the Origin of the Universe, Department of Physics and Astronomy, Seoul National University, Seoul (Korea, Republic of); Pforr, J. [National Optical Astronomy Observatories, 950 N Cherry Avenue, Tucson, AZ 85719 (United States); Wiklind, T. [Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile); Almaini, O. [University of Nottingham, School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Cooper, M. C. [Center for Galaxy Evolution, Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Weiner, B., E-mail: paola.santini@oa-roma.inaf.it [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); and others

    2015-03-10

    We present the public release of the stellar mass catalogs for the GOODS-S and UDS fields obtained using some of the deepest near-IR images available, achieved as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey project. We combine the effort from 10 different teams, who computed the stellar masses using the same photometry and the same redshifts. Each team adopted their preferred fitting code, assumptions, priors, and parameter grid. The combination of results using the same underlying stellar isochrones reduces the systematics associated with the fitting code and other choices. Thanks to the availability of different estimates, we can test the effect of some specific parameters and assumptions on the stellar mass estimate. The choice of the stellar isochrone library turns out to have the largest effect on the galaxy stellar mass estimates, resulting in the largest distributions around the median value (with a semi interquartile range larger than 0.1 dex). On the other hand, for most galaxies, the stellar mass estimates are relatively insensitive to the different parameterizations of the star formation history. The inclusion of nebular emission in the model spectra does not have a significant impact for the majority of galaxies (less than a factor of 2 for ∼80% of the sample). Nevertheless, the stellar mass for the subsample of young galaxies (age <100 Myr), especially in particular redshift ranges (e.g., 2.2 < z < 2.4, 3.2 < z < 3.6, and 5.5 < z < 6.5), can be seriously overestimated (by up to a factor of 10 for <20 Myr sources) if nebular contribution is ignored.

  6. Age gradients in the stellar populations of massive star forming regions based on a new stellar chronometer

    Energy Technology Data Exchange (ETDEWEB)

    Getman, Konstantin V.; Feigelson, Eric D.; Kuhn, Michael A.; Broos, Patrick S.; Townsley, Leisa K.; Luhman, Kevin L. [Department of Astronomy and Astrophysics, 525 Davey Laboratory, Pennsylvania State University, University Park, PA 16802 (United States); Naylor, Tim [School of Physics and Astronomy, University of Exeter, Stocker Road, Exeter, EX4 4QL (United Kingdom); Povich, Matthew S. [Department of Physics and Astronomy, California State Polytechnic University, 3801 West Temple Avenue, Pomona, CA 91768 (United States); Garmire, Gordon P. [Huntingdon Institute for X-ray Astronomy, LLC, 10677 Franks Road, Huntingdon, PA 16652 (United States)

    2014-06-01

    A major impediment to understanding star formation in massive star-forming regions (MSFRs) is the absence of a reliable stellar chronometer to unravel their complex star formation histories. We present a new estimation of stellar ages using a new method that employs near-infrared (NIR) and X-ray photometry, Age {sub JX} . Stellar masses are derived from X-ray luminosities using the L{sub X} -M relation from the Taurus cloud. J-band luminosities are compared to mass-dependent pre-main-sequence (PMS) evolutionary models to estimate ages. Age {sub JX} is sensitive to a wide range of evolutionary stages, from disk-bearing stars embedded in a cloud to widely dispersed older PMS stars. The Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) project characterizes 20 OB-dominated MSFRs using X-ray, mid-infrared, and NIR catalogs. The Age {sub JX} method has been applied to 5525 out of 31,784 MYStIX Probable Complex Members. We provide a homogeneous set of median ages for over 100 subclusters in 15 MSFRs; median subcluster ages range between 0.5 Myr and 5 Myr. The important science result is the discovery of age gradients across MYStIX regions. The wide MSFR age distribution appears as spatially segregated structures with different ages. The Age {sub JX} ages are youngest in obscured locations in molecular clouds, intermediate in revealed stellar clusters, and oldest in distributed populations. The NIR color index J – H, a surrogate measure of extinction, can serve as an approximate age predictor for young embedded clusters.

  7. A catalog of stellar spectrophotometry

    Science.gov (United States)

    Adelman, S. J.; Pyper, D. M.; Shore, S. N.; White, R. E.; Warren, W. H., Jr.

    1989-01-01

    A machine-readable catalog of stellar spectrophotometric measurements made with rotating grating scanner is introduced. Consideration is given to the processes by which the stellar data were collected and calibrated with the fluxes of Vega (Hayes and Latham, 1975). A sample page from the spectrophotometric catalog is presented.

  8. A broadband electromagnetic UT system

    International Nuclear Information System (INIS)

    Repplinger, W.; Salzburger, H.J.

    1985-01-01

    An ultrasonic testing system based on contactless electromagnetic acoustic (E.M.A.) transduction has been developed by which broadband ultrasonic pulses are excited. This system overcomes disadvantages of usual E.M.A. transducers with meanderlike coil configuration, namely the excitation of narrowband pulses and the symmetrical radiation pattern. By dividing up a meanderlike coil into single elements and a time-delayed firing of the elements, whereby the time delay is given by the distance of the elements and the phase velocity of the wave propagating along the surface, the ultrasonic pulse radiated in one preferred direction becomes broadband by constructive interference. The signals radiated in the opposite direction do no more interfere. Its amplitude is smaller than that of the other direction, so that the transducer becomes uni-directional. This technique can be applied for the excitation of all dispersionless waves (bulk waves and guided waves)

  9. Visible light broadband perfect absorbers

    Energy Technology Data Exchange (ETDEWEB)

    Jia, X. L.; Meng, Q. X.; Yuan, C. X.; Zhou, Z. X.; Wang, X. O., E-mail: wxo@hit.edu.cn [School of Science, Harbin Institute of Technology, Harbin 150001 (China)

    2016-03-15

    The visible light broadband perfect absorbers based on the silver (Ag) nano elliptical disks and holes array are studied using finite difference time domain simulations. The semiconducting indium silicon dioxide thin film is introduced as the space layer in this sandwiched structure. Utilizing the asymmetrical geometry of the structures, polarization sensitivity for transverse electric wave (TE)/transverse magnetic wave (TM) and left circular polarization wave (LCP)/right circular polarization wave (RCP) of the broadband absorption are gained. The absorbers with Ag nano disks and holes array show several peaks absorbance of 100% by numerical simulation. These simple and flexible perfect absorbers are particularly desirable for various potential applications including the solar energy absorber.

  10. Quasisymmetry equations for conventional stellarators

    International Nuclear Information System (INIS)

    Pustovitov, V.D.

    1994-11-01

    General quasisymmetry condition, which demands the independence of B 2 on one of the angular Boozer coordinates, is reduced to two equations containing only geometrical characteristics and helical field of a stellarator. The analysis is performed for conventional stellarators with a planar circular axis using standard stellarator expansion. As a basis, the invariant quasisymmetry condition is used. The quasisymmetry equations for stellarators are obtained from this condition also in an invariant form. Simplified analogs of these equations are given for the case when averaged magnetic surfaces are circular shifted torii. It is shown that quasisymmetry condition can be satisfied, in principle, in a conventional stellarator by a proper choice of two satellite harmonics of the helical field in addition to the main harmonic. Besides, there appears a restriction on the shift of magnetic surfaces. Thus, in general, the problem is closely related with that of self-consistent description of a configuration. (author)

  11. Integrated Broadband Quantum Cascade Laser

    Science.gov (United States)

    Mansour, Kamjou (Inventor); Soibel, Alexander (Inventor)

    2016-01-01

    A broadband, integrated quantum cascade laser is disclosed, comprising ridge waveguide quantum cascade lasers formed by applying standard semiconductor process techniques to a monolithic structure of alternating layers of claddings and active region layers. The resulting ridge waveguide quantum cascade lasers may be individually controlled by independent voltage potentials, resulting in control of the overall spectrum of the integrated quantum cascade laser source. Other embodiments are described and claimed.

  12. Synthetic Stromgren photometry for F dwarf stars

    Science.gov (United States)

    Bell, R. A.

    1988-01-01

    Recent synthetic spectrum and color calculations for cool dwarf star models are tested by comparison with observation. The accuracy of the computed dependence of the thermal colors B-V and b-y on effective temperature is examined, and H-beta indices are presented and compared with observed values. The accuracy of the predictions of the Stromgren uvby system metal-abundance indicator m1 and luminosity indicator c1 are tested. A new calibration of the c1, b-y diagram in terms of absolute magnitudes is given, making use of recent calculations of stellar isochrones. Observations of very metal-poor subdwarfs are used to study the accuracy of the isochrones. The c1, b-y diagram of the subdwarfs is compared with that of the turnoff-region stars in the very metal-poor globular cluster NGC 6397.

  13. Nucleosynthesis in stellar explosions

    Energy Technology Data Exchange (ETDEWEB)

    Woosley, S.E.; Axelrod, T.S.; Weaver, T.A.

    1983-01-01

    The final evolution and explosion of stars from 10 M/sub solar/ to 10/sup 6/ M/sub solar/ are reviewed with emphasis on factors affecting the expected nucleosynthesis. We order our paper in a sequence of decreasing mass. If, as many suspect, the stellar birth function was peaked towards larger masses at earlier times (see e.g., Silk 1977; but also see Palla, Salpeter, and Stahler 1983), this sequence of masses might also be regarded as a temporal sequence. At each stage of Galactic chemical evolution stars form from the ashes of preceding generations which typically had greater mass. A wide variety of Type I supernova models, most based upon accreting white dwarf stars, are also explored using the expected light curves, spectra, and nucleosynthesis as diagnostics. No clearly favored Type I model emerges that is capable of simultaneously satisfying all three constraints.

  14. Nucleosynthesis in stellar explosions

    International Nuclear Information System (INIS)

    Woosley, S.E.; Axelrod, T.S.; Weaver, T.A.

    1983-01-01

    The final evolution and explosion of stars from 10 M/sub solar/ to 10 6 M/sub solar/ are reviewed with emphasis on factors affecting the expected nucleosynthesis. We order our paper in a sequence of decreasing mass. If, as many suspect, the stellar birth function was peaked towards larger masses at earlier times (see e.g., Silk 1977; but also see Palla, Salpeter, and Stahler 1983), this sequence of masses might also be regarded as a temporal sequence. At each stage of Galactic chemical evolution stars form from the ashes of preceding generations which typically had greater mass. A wide variety of Type I supernova models, most based upon accreting white dwarf stars, are also explored using the expected light curves, spectra, and nucleosynthesis as diagnostics. No clearly favored Type I model emerges that is capable of simultaneously satisfying all three constraints

  15. Remarks on stellar clusters

    International Nuclear Information System (INIS)

    Teller, E.

    1985-01-01

    In the following, a few simple remarks on the evolution and properties of stellar clusters will be collected. In particular, globular clusters will be considered. Though details of such clusters are often not known, a few questions can be clarified with the help of primitive arguments. These are:- why are spherical clusters spherical, why do they have high densities, why do they consist of approximately a million stars, how may a black hole of great mass form within them, may they be the origin of gamma-ray bursts, may their invisible remnants account for the missing mass of our galaxy. The available data do not warrant a detailed evaluation. However, it is remarkable that exceedingly simple models can shed some light on the questions enumerated above. (author)

  16. L = ± 1 stellarator

    International Nuclear Information System (INIS)

    Kikuchi, T.; Shiina, S.; Saito, K.; Gesso, H.; Aizawa, M.; Kawakami, I.

    1985-01-01

    We report the magnetic field configuration of helical magnetic axis stellarator. The magnetic field configuration is composed of large l=1 field and small l=-1 and l=0(bumpy) fields. The large l=1 field (combined with the small l=-1 field) is used to form helical magnetic axis with the helical curvature much larger than the toroidal curvature, which provides the high limiting values of β. The small l=-1 field, furthermore, as well as the large l=1 field reduces the Pfirsch-Schlueter currents by combining with l=0 field. Therefore, the large l=1 field and the combination of three field components may be favourable for the increase of limiting β value

  17. Investigating the Bright End of LSST Photometry

    Science.gov (United States)

    Ojala, Elle; Pepper, Joshua; LSST Collaboration

    2018-01-01

    The Large Synoptic Survey Telescope (LSST) will begin operations in 2022, conducting a wide-field, synoptic multiband survey of the southern sky. Some fraction of objects at the bright end of the magnitude regime observed by LSST will overlap with other wide-sky surveys, allowing for calibration and cross-checking between surveys. The LSST is optimized for observations of very faint objects, so much of this data overlap will be comprised of saturated images. This project provides the first in-depth analysis of saturation in LSST images. Using the PhoSim package to create simulated LSST images, we evaluate saturation properties of several types of stars to determine the brightness limitations of LSST. We also collect metadata from many wide-field photometric surveys to provide cross-survey accounting and comparison. Additionally, we evaluate the accuracy of the PhoSim modeling parameters to determine the reliability of the software. These efforts will allow us to determine the expected useable data overlap between bright-end LSST images and faint-end images in other wide-sky surveys. Our next steps are developing methods to extract photometry from saturated images.This material is based upon work supported in part by the National Science Foundation through Cooperative Agreement 1258333 managed by the Association of Universities for Research in Astronomy (AURA), and the Department of Energy under Contract No. DE-AC02-76SF00515 with the SLAC National Accelerator Laboratory. Additional LSST funding comes from private donations, grants to universities, and in-kind support from LSSTC Institutional Members.Thanks to NSF grant PHY-135195 and the 2017 LSSTC Grant Award #2017-UG06 for making this project possible.

  18. Characterization of the Praesepe star cluster by photometry and proper motions with 2MASS, PPMXL, and Pan-STARRS

    Energy Technology Data Exchange (ETDEWEB)

    Wang, P. F.; Chen, W. P. [Department of Physics, National Central University, 300 Jhongda Road, Jhongli 32001, Taiwan (China); Lin, C. C.; Huang, C. K.; Panwar, N.; Lee, C. H. [Graduate Institute of Astronomy, National Central University, 300 Jhongda Road, Jhongli 32001, Taiwan (China); Pandey, A. K. [Aryabhatta Research Institute of Observational Sciences, Manora Peak, Nainital 263129 (India); Tsai, M. F.; Tang, C.-H. [Department of Computer Science and Information Engineering, National Central University, 300 Jhongda Road, Jhongli 32001, Taiwan (China); Goldman, B. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Burgett, W. S.; Chambers, K. C.; Flewelling, H.; Heasley, J. N.; Hodapp, K. W.; Huber, M. E.; Jedicke, R.; Kaiser, N. [Institute for Astronomy, University of Hawai' i, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Draper, P. W. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Grav, T. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); and others

    2014-03-20

    Membership identification is the first step in determining the properties of a star cluster. Low-mass members in particular could be used to trace the dynamical history, such as mass segregation, stellar evaporation, or tidal stripping, of a star cluster in its Galactic environment. We identified member candidates of the intermediate-age Praesepe cluster (M44) with stellar masses ∼0.11-2.4 M {sub ☉}, using Panoramic Survey Telescope And Rapid Response System and Two Micron All Sky Survey photometry, and PPMXL proper motions. Within a sky area of 3° radius, 1040 candidates are identified, of which 96 are new inclusions. Using the same set of selection criteria on field stars, an estimated false positive rate of 16% was determined, suggesting that 872 of the candidates are true members. This most complete and reliable membership list allows us to favor the BT-Settl model over other stellar models. The cluster shows a distinct binary track above the main sequence, with a binary frequency of 20%-40%, and a high occurrence rate of similar mass pairs. The mass function is consistent with that of the disk population but shows a deficit of members below 0.3 solar masses. A clear mass segregation is evidenced, with the lowest-mass members in our sample being evaporated from this disintegrating cluster.

  19. REMOVING BIASES IN RESOLVED STELLAR MASS MAPS OF GALAXY DISKS THROUGH SUCCESSIVE BAYESIAN MARGINALIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Martínez-García, Eric E. [Cerrada del Rey 40-A, Chimalcoyoc Tlalpan, Ciudad de México, C.P. 14630, México (Mexico); González-Lópezlira, Rosa A.; Bruzual A, Gustavo [Instituto de Radioastronomía y Astrofísica, UNAM, Campus Morelia, Michoacán, C.P. 58089, México (Mexico); Magris C, Gladis, E-mail: martinezgarciaeric@gmail.com [Centro de Investigaciones de Astronomía, Apartado Postal 264, Mérida 5101-A (Venezuela, Bolivarian Republic of)

    2017-01-20

    Stellar masses of galaxies are frequently obtained by fitting stellar population synthesis models to galaxy photometry or spectra. The state of the art method resolves spatial structures within a galaxy to assess the total stellar mass content. In comparison to unresolved studies, resolved methods yield, on average, higher fractions of stellar mass for galaxies. In this work we improve the current method in order to mitigate a bias related to the resolved spatial distribution derived for the mass. The bias consists in an apparent filamentary mass distribution and a spatial coincidence between mass structures and dust lanes near spiral arms. The improved method is based on iterative Bayesian marginalization, through a new algorithm we have named Bayesian Successive Priors (BSP). We have applied BSP to M51 and to a pilot sample of 90 spiral galaxies from the Ohio State University Bright Spiral Galaxy Survey. By quantitatively comparing both methods, we find that the average fraction of stellar mass missed by unresolved studies is only half what previously thought. In contrast with the previous method, the output BSP mass maps bear a better resemblance to near-infrared images.

  20. A Catalog of Stellar Unified Properties (CATSUP) for 951 FGK-Stars within 30 pc

    Energy Technology Data Exchange (ETDEWEB)

    Hinkel, Natalie R.; Somers, Garrett [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Mamajek, Eric E. [Jet Propulsion Laboratory, California Institute of Technology, M/S 321-100, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Turnbull, Margaret C. [Global Science Institute, P.O. Box 252, Antigo, WI 54409 (United States); Osby, Ella; Shkolnik, Evgenya L.; Desch, Steven J. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Smith, Graeme H. [University of California Observatories and Department of Astronomy and Astrophysics, University of California, Santa Cruz CA 95064 (United States); Klimasewski, Alexis, E-mail: natalie.hinkel@gmail.com [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627-0171 (United States)

    2017-10-10

    Almost every star in our Galaxy is likely to harbor a terrestrial planet, but accurate measurements of an exoplanet’s mass and radius demand accurate knowledge of the properties of its host star. The imminent TESS and CHEOPS missions are slated to discover thousands of new exoplanets. Along with WFIRST, which will directly image nearby planets, these surveys make urgent the need to better characterize stars in the nearby solar neighborhood (<30 pc). We have compiled the CATalog of Stellar Unified Properties (CATSUP) for 951 stars, including such data as: Gaia astrometry; multiplicity within stellar systems; stellar elemental abundance measurements; standardized spectral types; Ca ii H and K stellar activity indices; GALEX NUV and FUV photometry; and X-ray fluxes and luminosities from ROSAT , XMM, and Chandra . We use this data-rich catalog to find correlations, especially between stellar emission indices, colors, and galactic velocity. Additionally, we demonstrate that thick-disk stars in the sample are generally older, have lower activity, and have higher velocities normal to the galactic plane. We anticipate that CATSUP will be useful for discerning other trends among stars within the nearby solar neighborhood, for comparing thin-disk versus thick-disk stars, for comparing stars with and without planets, and for finding correlations between chemical and kinematic properties.

  1. The next generation of galaxy evolution models: A symbiosis of stellar populations and chemical abundances

    Science.gov (United States)

    Kotulla, Ralf

    2012-10-01

    Over its lifespan Hubble has invested significant effort into detailed observations of galaxies both in the local and distant universe. To extract the physical information from the observed {spectro-}photometry requires detailed and accurate models. Stellar population synthesis models are frequently used to obtain stellar masses, star formation rate, galaxy ages and star formation histories. Chemical evolution models offer another valuable and complementary approach to gain insight into many of the same aspects, yet these two methods have rarely been used in combination.Our proposed next generation of galaxy evolution models will help us improve our understanding of how galaxies form and evolve. Building on GALEV evolutionary synthesis models we incorporate state-of-the-art input physics for stellar evolution of binaries and rotating stars as well as new spectral libraries well matched to the modern observational capabilities. Our improved chemical evolution model allows us to self-consistently trace abundances of individual elements, fully accounting for the increasing initial abundances of successive stellar generations. GALEV will support variable Initial Mass Functions {IMF}, enabling us to test recent observational findings of a non-universal IMF by predicting chemical properties and integrated spectra in an integrated and consistent manner.HST is the perfect instrument for testing this approach. Its wide wavelength coverage from UV to NIR enables precise SED fitting, and with its spatial resolution we can compare the inferred chemical evolution to studies of star clusters and resolved stellar populations in nearby galaxies.

  2. Uncertainties and Systematic Effects on the estimate of stellar masses in high z galaxies

    Science.gov (United States)

    Salimbeni, S.; Fontana, A.; Giallongo, E.; Grazian, A.; Menci, N.; Pentericci, L.; Santini, P.

    2009-05-01

    We discuss the uncertainties and the systematic effects that exist in the estimates of the stellar masses of high redshift galaxies, using broad band photometry, and how they affect the deduced galaxy stellar mass function. We use at this purpose the latest version of the GOODS-MUSIC catalog. In particular, we discuss the impact of different synthetic models, of the assumed initial mass function and of the selection band. Using Chariot & Bruzual 2007 and Maraston 2005 models we find masses lower than those obtained from Bruzual & Chariot 2003 models. In addition, we find a slight trend as a function of the mass itself comparing these two mass determinations with that from Bruzual & Chariot 2003 models. As consequence, the derived galaxy stellar mass functions show diverse shapes, and their slope depends on the assumed models. Despite these differences, the overall results and scenario is observed in all these cases. The masses obtained with the assumption of the Chabrier initial mass function are in average 0.24 dex lower than those from the Salpeter assumption, at all redshifts, causing a shift of galaxy stellar mass function of the same amount. Finally, using a 4.5 μm-selected sample instead of a Ks-selected one, we add a new population of highly absorbed, dusty galaxies at z~=2-3 of relatively low masses, yielding stronger constraints on the slope of the galaxy stellar mass function at lower masses.

  3. A Catalog of Stellar Unified Properties (CATSUP) for 951 FGK-Stars within 30 pc

    International Nuclear Information System (INIS)

    Hinkel, Natalie R.; Somers, Garrett; Mamajek, Eric E.; Turnbull, Margaret C.; Osby, Ella; Shkolnik, Evgenya L.; Desch, Steven J.; Smith, Graeme H.; Klimasewski, Alexis

    2017-01-01

    Almost every star in our Galaxy is likely to harbor a terrestrial planet, but accurate measurements of an exoplanet’s mass and radius demand accurate knowledge of the properties of its host star. The imminent TESS and CHEOPS missions are slated to discover thousands of new exoplanets. Along with WFIRST, which will directly image nearby planets, these surveys make urgent the need to better characterize stars in the nearby solar neighborhood (<30 pc). We have compiled the CATalog of Stellar Unified Properties (CATSUP) for 951 stars, including such data as: Gaia astrometry; multiplicity within stellar systems; stellar elemental abundance measurements; standardized spectral types; Ca ii H and K stellar activity indices; GALEX NUV and FUV photometry; and X-ray fluxes and luminosities from ROSAT , XMM, and Chandra . We use this data-rich catalog to find correlations, especially between stellar emission indices, colors, and galactic velocity. Additionally, we demonstrate that thick-disk stars in the sample are generally older, have lower activity, and have higher velocities normal to the galactic plane. We anticipate that CATSUP will be useful for discerning other trends among stars within the nearby solar neighborhood, for comparing thin-disk versus thick-disk stars, for comparing stars with and without planets, and for finding correlations between chemical and kinematic properties.

  4. Calibrating the Near-Infrared Tip of the Red Giant Branch with Multiwavelength Photometry

    Science.gov (United States)

    Durbin, Meredith

    2017-08-01

    The near-infrared (NIR) tip of the red giant branch (TRGB) shows outstanding promise as a distance indicator. In the JWST era, the NIR-TRGB will bridge the gap from local geometric parallax (with Gaia) out to the low-velocity Hubble flow in a single step, in all types of galaxies. However, there currently exist several impediments to JWST's using the TRGB to full advantage. Dalcanton et al. (2012) presented the most comprehensive dataset available for calibrating the TRGB absolute magnitude, with optical and NIR coverage of 23 nearby dwarf and spiral galaxies spanning a wide range of ages and metallicities. However, subtle offsets between this dataset, theoretical models, and globular clusters raise concerns about the calibration.We propose to perform a complete re-reduction and re-analysis of this dataset. We have developed a pipeline that leverages simultaneous fitting of optical and NIR data to produce NIR photometry of higher quality and completeness, with up to 1.5 mag greater depth than can be achieved with the NIR alone. With this added depth, improvements in photometric precision, and updated WFC3/IR PSFs and flux calibration, we will derive uniform, precise, and accurate NIR TRGB measurements, with which we will be able to resolve standing issues with the TRGB color-absolute magnitude relation and its behavior with changing star-formation histories. This work will lay the groundwork for extending the TRGB distance scale out to at least 37 Mpc with JWST. We will release the resulting 4-filter optical-NIR photometry as HLSPs for use by the community before the launch of JWST, to serve as a resource for proposing for stellar population observations in the NIR.

  5. Infrared photometry, extinction curves and R values for stars in the southern Milky Way

    International Nuclear Information System (INIS)

    Whittet, D.C.B.; Breda, I.G. Van; Glass, I.S.

    1976-01-01

    Infrared photometry in the JHKL bands is combined with photoelectric scanner photometry to give interstellar extinction curves in the range lambda 0.34 to 3.4 μ for 22 early-type stars in the Southern Milky Way. The extinction curves show variations in curvature in the infrared which are related to the well-known change in slope in the near ultraviolet. The curves are extrapolated to lambda -1 = 0 with the aid of Mie theory computations for a graphite-iron-silicate grain model, and values of the ratio of total to selective extinction R = Asub(v)/Esub(B-V) are deduced. R is found to vary between 2.7 and 3.5 with a median value of 3.2 for stars with long-path-length reddening, while two stars in the rho Ophiuchi dark cloud have R values of 3.6 and 4.3. The variations found in the extinction curves probably result from regional fluctuations in the mean grain size and/or composition along the line of sight, and any systematic variation in R with galactic longitude is likely to be small. The derived R values are correlated with the wavelength of maximum polarization. R is found to be normal for HD 90706 in the cluster IC 2581, for which a high R value has been suggested. It is noted that R has now been shown to lie in the range 4.1 to 4.4 for stars in the denser regions of the rho Ophiuchi cloud by four independent methods. None of the observed stars show strong infrared excess radiation at 3.4 μ. Small excesses measured for a few high-luminosity stars associated with mass loss may be due to free-free emission in gaseous stellar envelopes. (author)

  6. The Optical Gravitational Lensing Experiment. UBVI Photometry of Stars in Baade's Window

    Science.gov (United States)

    Paczynski, B.; Udalski, A.; Szymanski, M.; Kubiak, M.; Pietrzynski, G.; Soszynski, I.; Wozniak, P.; Zebrun, K.

    1999-09-01

    We present UBVI photometry for 8530 stars in Baade's Window obtained during the OGLE-II microlensing survey. Among these are over one thousand red clump giants. 1391 of them have photometry with errors smaller than 0.04, 0.06, 0.12, and 0.20 mag in the I, V, B, and U-band, respectively. We constructed a map of interstellar reddening. The corrected colors of the red clump giants: (U-B)_0, (B-V)_0, and (V-I)_0 are very well correlated, indicating that a single parameter determines the observed spread of their values, reaching almost 2 mag in the (U-B)_0. It seems most likely that heavy element content is the dominant parameter, but it is possible that another parameter: the age (or mass) of a star moves it along the same trajectory in the color-color diagram as the metallicity. The current ambiguity can be resolved with spectral analysis, and our catalog may be useful as a finding list of red clump giants. We point out that these K giants are more suitable for a fair determination of the distribution of metallicity than brighter M giants. We also present a compilation of UBVI data for 308 red clump giants near the Sun, for which Hipparcos parallaxes are more accurate than 10%. Spectral analysis of their metallicity may provide information about the local metallicity distribution as well as the extent to which mass (age) of these stars affects their colors. It is remarkable that in spite of a number of problems, stellar models agree with observations at the 0.1-0.2 mag level, making red clump giants not only the best calibrated but also the best understood standard candle.

  7. Herschel-PACS photometry of faint stars for sensitivity performance assessment and establishment of faint FIR primary photometric standards

    Science.gov (United States)

    Klaas, U.; Balog, Z.; Nielbock, M.; Müller, T. G.; Linz, H.; Kiss, Cs.

    2018-05-01

    Aims: Our aims are to determine flux densities and their photometric accuracy for a set of seventeen stars that range in flux from intermediately bright (≲2.5 Jy) to faint (≳5 mJy) in the far-infrared (FIR). We also aim to derive signal-to-noise dependence with flux and time, and compare the results with predictions from the Herschel exposure-time calculation tool. Methods: We obtain aperture photometry from Herschel-PACS high-pass-filtered scan maps and chop/nod observations of the faint stars. The issues of detection limits and sky confusion noise are addressed by comparison of the field-of-view at different wavelengths, by multi-aperture photometry, by special processing of the maps to preserve extended emission, and with the help of large-scale absolute sky brightness maps from AKARI. This photometry is compared with flux-density predictions based on photospheric models for these stars. We obtain a robust noise estimate by fitting the flux distribution per map pixel histogram for the area around the stars, scaling it for the applied aperture size and correcting for noise correlation. Results: For 15 stars we obtain reliable photometry in at least one PACS filter, and for 11 stars we achieve this in all three PACS filters (70, 100, 160 μm). Faintest fluxes, for which the photometry still has good quality, are about 10-20 mJy with scan map photometry. The photometry of seven stars is consistent with models or flux predictions for pure photospheric emission, making them good primary standard candidates. Two stars exhibit source-intrinsic far-infrared excess: β Gem (Pollux), being the host star of a confirmed Jupiter-size exoplanet, due to emission of an associated dust disk, and η Dra due to dust emission in a binary system with a K1 dwarf. The investigation of the 160 μm sky background and environment of four sources reveals significant sky confusion prohibiting the determination of an accurate stellar flux at this wavelength. As a good model

  8. The stellar content of the isolated transition dwarf galaxy DDO210

    OpenAIRE

    McConnachie, Alan W.; Arimoto, Nobuo; Irwin, Mike; Tolstoy, Eline

    2006-01-01

    We use Subaru Suprime-Cam and VLT FORS1 photometry of the dwarf galaxy DDO210 to study the global stellar content and structural properties of a transition-type galaxy (with properties intermediate between dwarf irregular and dwarf spheroidal systems). This galaxy is sufficiently isolated that tidal interactions are not likely to have affected its evolution in any way. The colour-magnitude diagrams of DDO210 show a red giant branch (RGB) population (with an RGB bump), a bright asymptotic gian...

  9. Analysis of the Proposed Ghana Broadband Strategy

    DEFF Research Database (Denmark)

    Williams, Idongesit; Botwe, Yvonne

    This project studied the Ghana Broadband Strategy with the aim of evaluating the recommendations in the strategy side by side the broadband development in Ghana. The researchers conducted interviews both officially and unofficially with ICT stakeholders, made observations, studied Government...... intervention policies recommended in the Ghana broadband policy is used to evaluate the broadband market to find out whether the strategy consolidates with the Strengths and opportunities of the market and whether it corrects the anomalies that necessitate the weaknesses and threats to the market....... The strategy did address some threats and weaknesses of the broadband market. It also consolidated on some strengths and opportunities of the broadband market. The researchers also discovered that a market can actually grow without a policy. But a market will grow faster if a well implemented policy is guiding...

  10. Finding Exoplanets Using Point Spread Function Photometry on Kepler Data

    Science.gov (United States)

    Amaro, Rachael Christina; Scolnic, Daniel; Montet, Ben

    2018-01-01

    The Kepler Mission has been able to identify over 5,000 exoplanet candidates using mostly aperture photometry. Despite the impressive number of discoveries, a large portion of Kepler’s data set is neglected due to limitations using aperture photometry on faint sources in crowded fields. We present an alternate method that overcomes those restrictions — Point Spread Function (PSF) photometry. This powerful tool, which is already used in supernova astronomy, was used for the first time on Kepler Full Frame Images, rather than just looking at the standard light curves. We present light curves for stars in our data set and demonstrate that PSF photometry can at least get down to the same photometric precision as aperture photometry. As a check for the robustness of this method, we change small variables (stamp size, interpolation amount, and noise correction) and show that the PSF light curves maintain the same repeatability across all combinations for one of our models. We also present our progress in the next steps of this project, including the creation of a PSF model from the data itself and applying the model across the entire data set at once.

  11. Multicolor photometry of the merging galaxy cluster A2319: Dynamics and star formation properties

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Peng-Fei; Yuan, Qi-Rong [Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing 210023 (China); Zhang, Li [QuFu Education Bureau, QuFu 273100 (China); Zhou, Xu, E-mail: pfyan0822@sina.com, E-mail: yuanqirong@njnu.edu.cn [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2014-05-01

    Asymmetric X-ray emission and a powerful cluster-scale radio halo indicate that A2319 is a merging cluster of galaxies. This paper presents our multicolor photometry for A2319 with 15 optical intermediate filters in the Beijing-Arizona-Taiwan-Connecticut (BATC) system. There are 142 galaxies with known spectroscopic redshifts within the viewing field of 58' × 58' centered on this rich cluster, including 128 member galaxies (called sample I). A large velocity dispersion in the rest frame, 1622{sub −70}{sup +91} km s{sup –1}, suggests merger dynamics in A2319. The contour map of projected density and localized velocity structure confirm the so-called A2319B substructure, at ∼10' northwest to the main concentration A2319A. The spectral energy distributions (SEDs) of more than 30,000 sources are obtained in our BATC photometry down to V ∼ 20 mag. A u-band (∼3551 Å) image with better seeing and spatial resolution, obtained with the Bok 2.3 m telescope at Kitt Peak, is taken to make star-galaxy separation and distinguish the overlapping contamination in the BATC aperture photometry. With color-color diagrams and photometric redshift technique, 233 galaxies brighter than h {sub BATC} = 19.0 are newly selected as member candidates after an exclusion of false candidates with contaminated BATC SEDs by eyeball-checking the u-band Bok image. The early-type galaxies are found to follow a tight color-magnitude correlation. Based on sample I and the enlarged sample of member galaxies (called sample II), subcluster A2319B is confirmed. The star formation properties of cluster galaxies are derived with the evolutionary synthesis model, PEGASE, assuming a Salpeter initial mass function and an exponentially decreasing star formation rate (SFR). A strong environmental effect on star formation histories is found in the manner that galaxies in the sparse regions have various star formation histories, while galaxies in the dense regions are found to have

  12. Principles of broadband switching and networking

    CERN Document Server

    Liew, Soung C

    2010-01-01

    An authoritative introduction to the roles of switching and transmission in broadband integrated services networks Principles of Broadband Switching and Networking explains the design and analysis of switch architectures suitable for broadband integrated services networks, emphasizing packet-switched interconnection networks with distributed routing algorithms. The text examines the mathematical properties of these networks, rather than specific implementation technologies. Although the pedagogical explanations in this book are in the context of switches, many of the fundamenta

  13. Unveiling the Low Surface Brightness Stellar Peripheries of Galaxies

    Science.gov (United States)

    Ferguson, Annette M. N.

    2018-01-01

    The low surface brightness peripheral regions of galaxies contain a gold mine of information about how minor mergers and accretions have influenced their evolution over cosmic time. Enormous stellar envelopes and copious amounts of faint tidal debris are natural outcomes of the hierarchical assembly process and the search for and study of these features, albeit highly challenging, offers the potential for unrivalled insight into the mechanisms of galaxy growth. Over the last two decades, there has been burgeoning interest in probing galaxy outskirts using resolved stellar populations. Wide-field surveys have uncovered vast tidal debris features and new populations of very remote globular clusters, while deep Hubble Space Telescope photometry has provided exquisite star formation histories back to the earliest epochs. I will highlight some recent results from studies within and beyond the Local Group and conclude by briefly discussing the great potential of future facilities, such as JWST, Euclid, LSST and WFIRST, for major breakthroughs in low surface brightness galaxy periphery science.

  14. A Photometric Machine-Learning Method to Infer Stellar Metallicity

    Science.gov (United States)

    Miller, Adam A.

    2015-01-01

    Following its formation, a star's metal content is one of the few factors that can significantly alter its evolution. Measurements of stellar metallicity ([Fe/H]) typically require a spectrum, but spectroscopic surveys are limited to a few x 10(exp 6) targets; photometric surveys, on the other hand, have detected > 10(exp 9) stars. I present a new machine-learning method to predict [Fe/H] from photometric colors measured by the Sloan Digital Sky Survey (SDSS). The training set consists of approx. 120,000 stars with SDSS photometry and reliable [Fe/H] measurements from the SEGUE Stellar Parameters Pipeline (SSPP). For bright stars (g' < or = 18 mag), with 4500 K < or = Teff < or = 7000 K, corresponding to those with the most reliable SSPP estimates, I find that the model predicts [Fe/H] values with a root-mean-squared-error (RMSE) of approx.0.27 dex. The RMSE from this machine-learning method is similar to the scatter in [Fe/H] measurements from low-resolution spectra..

  15. Estimating Stellar Parameters and Interstellar Extinction from Evolutionary Tracks

    Directory of Open Access Journals (Sweden)

    Sichevsky S.

    2016-03-01

    Full Text Available Developing methods for analyzing and extracting information from modern sky surveys is a challenging task in astrophysical studies. We study possibilities of parameterizing stars and interstellar medium from multicolor photometry performed in three modern photometric surveys: GALEX, SDSS, and 2MASS. For this purpose, we have developed a method to estimate stellar radius from effective temperature and gravity with the help of evolutionary tracks and model stellar atmospheres. In accordance with the evolution rate at every point of the evolutionary track, star formation rate, and initial mass function, a weight is assigned to the resulting value of radius that allows us to estimate the radius more accurately. The method is verified for the most populated areas of the Hertzsprung-Russell diagram: main-sequence stars and red giants, and it was found to be rather precise (for main-sequence stars, the average relative error of radius and its standard deviation are 0.03% and 3.87%, respectively.

  16. Polarimetry and photometry of active quasars at visual and near-infrared wavelengths

    International Nuclear Information System (INIS)

    Smith, P.S.

    1986-01-01

    The optical and near-infrared continua of highly luminous BL Lacertae (BL Lac) objects and optically violent variable (OVV) quasars are studied through simultaneous broad-band photometry and linear polarimetry. Nineteen BL Lacs and OVVs were monitored during a ∼1 1/2-year period, with the major aim of characterizing the wavelength-dependent polarization exhibited by these objects. Optical (UBVRI) observations were conducted at the UCSD/U. Minn. 1.5-m telescope on Mt. Lemmon, Arizona. Simultaneous (within 1 hr.) near-infrared (JHK) measurements were made using the KPNO 2.1-m telescope. Most of the BL Lac objects exhibit large variations in polarization and brightness on time scale of less than a week. The degree of fractional linear polarization (P) is not observed to be related to brightness or optical spectral index. Most BL Lacs did not show a preferred polarization position angle (theta). Wavelength-dependent P and theta are observed in almost all BL Lacs, but not always simultaneously. The OVV quasar 1156 + 295 shows behavior very similar to the BL Lac objects. 3C 345 Exhibited polarization properties that are quite different from those of the BL Lacs. This object showed a clear correlation between brightness and P

  17. Precision Photometry and Astrometry from Pan-STARRS

    Science.gov (United States)

    Magnier, Eugene A.; Pan-STARRS Team

    2018-01-01

    The Pan-STARRS 3pi Survey has been calibrated with excellent precision for both astrometry and photometry. The Pan-STARRS Data Release 1, opened to the public on 2016 Dec 16, provides photometry in 5 well-calibrated, well-defined bandpasses (grizy) astrometrically registered to the Gaia frame. Comparisons with other surveys illustrate the high quality of the calibration and provide tests of remaining systematic errors in both Pan-STARRS and those external surveys. With photometry and astrometry of roughly 3 billion astronomical objects, the Pan-STARRS DR1 has substantial overlap with Gaia, SDSS, 2MASS and other surveys. I will discuss the astrometric tie between Pan-STARRS DR1 and Gaia and show comparisons between Pan-STARRS and other large-scale surveys.

  18. A Practical Guide to Lightcurve Photometry and Analysis

    CERN Document Server

    Warner, Brian D

    2006-01-01

    A Practical Guide to Lightcurve Photometry and Analysis provides, for those with access to even a modest telescope and CCD camera, all the information needed to take part in the scientific study of asteroids and variable stars. Using commercially available equipment, amateur astronomers can determine the rotation rate, size, and shape of asteroids. Similarly, it is possible to discover the size, temperature, and orbits of stars in binary systems by using this powerful technique. A Practical Guide to Lightcurve Photometry and Analysis contains all the material needed for readers to understand the theory, and avoid the practical pitfalls of lightcurve photometry. Detailed examples are given for obtaining data, and of course for the exciting and rewarding task of analyzing the data to determine the physical properties of the object. Any college student or amateur astronomer who wants to go beyond mere imaging with a CCD camera and enter the challenging world of "real science" via the lightcurves of asteroids and...

  19. Evolution of stellar systems

    International Nuclear Information System (INIS)

    Vader, P.

    1981-01-01

    The stellar systems of which the evolution will be considered in this thesis, are either galaxies, which contain about 10 11 stars, or binary systems, which consist of only two stars. It is seen that binary systems can give us some insight into the relative age of the nucleus of M31. The positive correlation between the metal content of a galaxy and its mass, first noted for elliptical galaxies, seems to be a general property of galaxies of all types. The observed increase of metallicity with galaxy mass is too large to be accounted for by differences in the evolutionary stage of galaxies. To explain the observed correlation it is proposed that a relatively larger proportion of massive stars is formed in more massive galaxies. The physical basis is that the formation of massive stars seems to be tied to the enhanced gas-dynamical activity in more massive galaxies. A specific aspect of the production of heavy elements by massive stars is investigated in some detail. In 1979 a cluster of 18 point X-ray sources within 400 pc of the centre of M31 was detected with the Einstein satellite. This is a remarkable result since no equivalent of this cluster has been observed in the nucleus of our own Galaxy, which otherwise is very similar to that of M31. An explanation for this phenomenon is proposed, suggesting that X-ray binaries are the products of the long-term evolution of nova systems. (Auth.)

  20. Stellar extreme ultraviolet astronomy

    International Nuclear Information System (INIS)

    Cash, W.C. Jr.

    1978-01-01

    The design, calibration, and launch of a rocket-borne imaging telescope for extreme ultraviolet astronomy are described. The telescope, which employed diamond-turned grazing incidence optics and a ranicon detector, was launched November 19, 1976, from the White Sands Missile Range. The telescope performed well and returned data on several potential stellar sources of extreme ultraviolet radiation. Upper limits ten to twenty times more sensitive than previously available were obtained for the extreme ultraviolet flux from the white dwarf Sirius B. These limits fall a factor of seven below the flux predicted for the star and demonstrate that the temperature of Sirius B is not 32,000 K as previously measured, but is below 30,000 K. The new upper limits also rule out the photosphere of the white dwarf as the source of the recently reported soft x-rays from Sirius. Two other white dwarf stars, Feige 24 and G191-B2B, were observed. Upper limits on the flux at 300 A were interpreted as lower limits on the interstellar hydrogen column densities to these stars. The lower limits indicate interstellar hydrogen densitites of greater than .02 cm -3 . Four nearby stars (Sirius, Procyon, Capella, and Mirzam) were observed in a search for intense low temperature coronae or extended chromospheres. No extreme ultraviolet radiation from these stars was detected, and upper limits to their coronal emisson measures are derived

  1. Mapping stellar surface features

    International Nuclear Information System (INIS)

    Noah, P.V.

    1987-01-01

    New photometric and spectroscopic observations of the RS Canum Venaticorum binaries Sigma Geminorum and UX Arietis are reported along with details of the Doppler-imaging program SPOTPROF. The observations suggest that the starspot activity on Sigma Gem has decreased to 0.05 magnitude in two years. A photometric spot model for September 1984 to January 1985 found that a single spot covering 2% of the surface and 1000 K cooler than the surrounding photosphere could model the light variations. Equivalent-width observations contemporaneous with the photometric observations did not show any significant variations. Line-profile models from SPOTPROF predict that the variation of the equivalent width of the 6393 A Fe I line should be ∼ 1mA. Photometric observations of UX Ari from January 1984 to March 1985 show an 0.3 magnitude variation indicating a large spot group must cover the surface. Contemporaneous spectroscopic observations show asymmetric line profiles. The Doppler imaging and the photometric light-curve models were used in an iterative method to describe the stellar surface-spot distribution and successfully model both the photometric and the spectroscopic variations

  2. SI: The Stellar Imager

    Science.gov (United States)

    Carpenter, Kenneth G.; Schrijver, Carolus J.; Karovska, Margarita

    2006-01-01

    The ultra-sharp images of the Stellar Imager (SI) will revolutionize our view of many dynamic astrophysical processes: The 0.1 milliarcsec resolution of this deep-space telescope will transform point sources into extended sources, and simple snapshots into spellbinding evolving views. SI s science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. SI s prime goal is to enable long-term forecasting of solar activity and the space weather that it drives in support of the Living With a Star program in the Exploration Era by imaging a sample of magnetically active stars with enough resolution to map their evolving dynamo patterns and their internal flows. By exploring the Universe at ultra-high resolution, SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magnetohydrodynamically controlled structures and processes in the Universe.

  3. Stellar Presentations (Abstract)

    Science.gov (United States)

    Young, D.

    2015-12-01

    (Abstract only) The AAVSO is in the process of expanding its education, outreach and speakers bureau program. powerpoint presentations prepared for specific target audiences such as AAVSO members, educators, students, the general public, and Science Olympiad teams, coaches, event supervisors, and state directors will be available online for members to use. The presentations range from specific and general content relating to stellar evolution and variable stars to specific activities for a workshop environment. A presentation—even with a general topic—that works for high school students will not work for educators, Science Olympiad teams, or the general public. Each audience is unique and requires a different approach. The current environment necessitates presentations that are captivating for a younger generation that is embedded in a highly visual and sound-bite world of social media, twitter and U-Tube, and mobile devices. For educators, presentations and workshops for themselves and their students must support the Next Generation Science Standards (NGSS), the Common Core Content Standards, and the Science Technology, Engineering and Mathematics (STEM) initiative. Current best practices for developing relevant and engaging powerpoint presentations to deliver information to a variety of targeted audiences will be presented along with several examples.

  4. Tuchola County Broadband Network (TCBN)

    DEFF Research Database (Denmark)

    Zabludowski, Antoni; Dubalski, B.; Zabludowski, Lukasz

    2012-01-01

    In the paper the designing project (plan) of Tuchola City broadband IP optical network has been presented. The extended version of network plan constitute technical part of network Feasibility Study, that it is expected to be implemented in Tuchola and be financed from European Regional Development...... Funds. The network plan presented in the paper contains both topological structure of fiber optic network as well as the active equipment for the network. In the project described in the paper it has been suggested to use Modular Cable System - MCS for passive infrastructure and Metro Ethernet...

  5. Understanding broadband over power line

    CERN Document Server

    Held, Gilbert

    2006-01-01

    Understanding Broadband over Power Line explores all aspects of the emerging technology that enables electric utilities to provide support for high-speed data communications via their power infrastructure. This book examines the two methods used to connect consumers and businesses to the Internet through the utility infrastructure: the existing electrical wiring of a home or office; and a wireless local area network (WLAN) access point.Written in a practical style that can be understood by network engineers and non-technologists alike, this volume offers tutorials on electric utility infrastru

  6. Achieving Universal Access to Broadband

    Directory of Open Access Journals (Sweden)

    Morten FALCH

    2009-01-01

    Full Text Available The paper discusses appropriate policy measures for achieving universal access to broadband services in Europe. Access can be delivered by means of many different technology solutions described in the paper. This means a greater degree of competition and affects the kind of policy measures to be applied. The paper concludes that other policy measure than the classical universal service obligation are in play, and discusses various policy measures taking the Lisbon process as a point of departure. Available policy measures listed in the paper include, universal service obligation, harmonization, demand stimulation, public support for extending the infrastructure, public private partnerships (PPP, and others.

  7. Turbulence optimisation in stellarator experiments

    Energy Technology Data Exchange (ETDEWEB)

    Proll, Josefine H.E. [Max-Planck/Princeton Center for Plasma Physics (Germany); Max-Planck-Institut fuer Plasmaphysik, Wendelsteinstr. 1, 17491 Greifswald (Germany); Faber, Benjamin J. [HSX Plasma Laboratory, University of Wisconsin-Madison, Madison, WI 53706 (United States); Helander, Per; Xanthopoulos, Pavlos [Max-Planck/Princeton Center for Plasma Physics (Germany); Lazerson, Samuel A.; Mynick, Harry E. [Plasma Physics Laboratory, Princeton University, P.O. Box 451 Princeton, New Jersey 08543-0451 (United States)

    2015-05-01

    Stellarators, the twisted siblings of the axisymmetric fusion experiments called tokamaks, have historically suffered from confining the heat of the plasma insufficiently compared with tokamaks and were therefore considered to be less promising candidates for a fusion reactor. This has changed, however, with the advent of stellarators in which the laminar transport is reduced to levels below that of tokamaks by shaping the magnetic field accordingly. As in tokamaks, the turbulent transport remains as the now dominant transport channel. Recent analytical theory suggests that the large configuration space of stellarators allows for an additional optimisation of the magnetic field to also reduce the turbulent transport. In this talk, the idea behind the turbulence optimisation is explained. We also present how an optimised equilibrium is obtained and how it might differ from the equilibrium field of an already existing device, and we compare experimental turbulence measurements in different configurations of the HSX stellarator in order to test the optimisation procedure.

  8. Optimizing Stellarators for Turbulent Transport

    International Nuclear Information System (INIS)

    Mynick, H.E.; Pomphrey, N.; Xanthopoulos, P.

    2010-01-01

    Up to now, the term 'transport-optimized' stellarators has meant optimized to minimize neoclassical transport, while the task of also mitigating turbulent transport, usually the dominant transport channel in such designs, has not been addressed, due to the complexity of plasma turbulence in stellarators. Here, we demonstrate that stellarators can also be designed to mitigate their turbulent transport, by making use of two powerful numerical tools not available until recently, namely gyrokinetic codes valid for 3D nonlinear simulations, and stellarator optimization codes. A first proof-of-principle configuration is obtained, reducing the level of ion temperature gradient turbulent transport from the NCSX baseline design by a factor of about 2.5.

  9. Stellar magnetic activity and exoplanets

    Directory of Open Access Journals (Sweden)

    Vidotto A.A.

    2017-01-01

    Full Text Available It has been proposed that magnetic activity could be enhanced due to interactions between close-in massive planets and their host stars. In this article, I present a brief overview of the connection between stellar magnetic activity and exoplanets. Stellar activity can be probed in chromospheric lines, coronal emission, surface spot coverage, etc. Since these are manifestations of stellar magnetism, these measurements are often used as proxies for the magnetic field of stars. Here, instead of focusing on the magnetic proxies, I overview some recent results of magnetic field measurements using spectropolarimetric observations. Firstly, I discuss the general trends found between large-scale magnetism, stellar rotation, and coronal emission and show that magnetism seems to be correlated to the internal structure of the star. Secondly, I overview some works that show evidence that exoplanets could (or not act as to enhance the activity of their host stars.

  10. BRITE-Constellation: Nanosatellites for precision photometry of bright stars

    Science.gov (United States)

    Weiss, W. W.; Moffat, A. F. J.; Schwarzenberg-Czerny, A.; Koudelka, O. F.; Grant, C. C.; Zee, R. E.; Kuschnig, R.; Mochnacki, St.; Rucinski, S. M.; Matthews, J. M.; Orleański, P.; Pamyatnykh, A. A.; Pigulski, A.; Alves, J.; Guedel, M.; Handler, G.; Wade, G. A.; Scholtz, A. L.; Scholtz

    2014-02-01

    BRITE-Constellation (where BRITE stands for BRIght Target Explorer) is an international nanosatellite mission to monitor photometrically, in two colours, brightness and temperature variations of stars brighter than V ~ 4, with precision and time coverage not possible from the ground. The current mission design consists of three pairs of 7 kg nanosats (hence ``Constellation'') from Austria, Canada and Poland carrying optical telescopes (3 cm aperture) and CCDs. One instrument in each pair is equipped with a blue filter; the other, a red filter. The first two nanosats (funded by Austria) are UniBRITE, designed and built by UTIAS-SFL (University of Toronto Institute for Aerospace Studies-Space Flight Laboratory) and its twin, BRITE-Austria, built by the Technical University Graz (TUG) with support of UTIAS-SFL. They were launched on 25 February 2013 by the Indian Space Agency, under contract to the Canadian Space Agency. Each BRITE instrument has a wide field of view (~ 24 degrees), so up to 15 bright stars can be observed simultaneously in 32 × 32 sub-rasters. Photometry (with reduced precision but thorough time sampling) of additional fainter targets will be possible through on-board data processing. A critical technical element of the BRITE mission is the three-axis attitude control system to stabilize a nanosat with very low inertia. The pointing stability is better than 1.5 arcminutes rms, a significant advance by UTIAS-SFL over any previous nanosatellite. BRITE-Constellation will primarily measure p- and g-mode pulsations to probe the interiors and ages of stars through asteroseismology. The BRITE sample of many of the brightest stars in the night sky is dominated by the most intrinsically luminous stars: massive stars seen at all evolutionary stages, and evolved medium-mass stars at the very end of their nuclear burning phases (cool giants and AGB stars). The Hertzsprung-Russell diagram for stars brighter than mag V=4 from which the BRITE-Constellation sample

  11. Superbanana orbits in stellarator geometries

    International Nuclear Information System (INIS)

    Derr, J.A.; Shohet, J.L.

    1979-04-01

    The presence of superbanana orbit types localized to either the interior or the exterior of stellarators and torsatrons is numerically investigated for 3.5 MeV alpha particles. The absence of the interior superbanana in both geometries is found to be due to non-conservation of the action. Exterior superbananas are found in the stellarator only, as a consequence of the existence of closed helical magnetic wells. No superbananas of either type are found in the torsatron

  12. On origin of stellar clusters

    International Nuclear Information System (INIS)

    Tovmasyan, G.M.

    1977-01-01

    The ratios of the gas component of the mass of young stellar clusters to their stellar mass are considered. They change by more than four orders from one cluster to another. The results are in direct contradiction with the hypothesis of formation of cluster stars from a preliminarily existing gas cloud by its condensation, and they favour the Ambartsumian hypothesis of the joint origin of stars and gas clouds from superdense protostellar matter

  13. Jonckheere Double Star Photometry – Part X: Hercules

    Science.gov (United States)

    Knapp, Wilfried

    2018-04-01

    If any double star discoverer is in urgent need of photometry then it is Jonckheere. There are over 3000 Jonckheere objects listed in the WDS catalog and a good part of them with magnitudes obviously far too bright. This report covers 28 of the in total 82 Jonckheere objects in the constellation Hercules selected by a quick WDS data check for being potentially listed with questionable magnitudes. At least one image per object was taken with V-filter to allow for visual magnitude measurement by differential photometry. All objects were additionally checked for common proper motion and two qualify indeed as potential CPM pairs.

  14. UBV-photometry of flare stars in pleiades

    International Nuclear Information System (INIS)

    Chavushyan, O.S.; Garibdzhanyan, A.T.

    1975-01-01

    The results are presented of UBV-photometry of 283 flare stars at the minimum of brightness in the Pleiad region. A new method has been developed and used of taking into account the background in photographic UBV-photometry with an iris microphotometer. The data obtained indicate that the flare Pleiad stars are located on both sides of the main sequence in the light-luminosity (V,B-V) diagram, while in the (U-B,B-V) diagram they are largely located above the main sequence

  15. Photoelectric UBV-photometry of the In(YY) DR Tauri-type young star in 1982-1986

    International Nuclear Information System (INIS)

    Kolotilov, E.A.

    1987-01-01

    The results of photoelectric UBV-photometry carried out in 1982-1986 for DR TAU - the star which undergone nova-like brightness increase in 1965-1980 - are presented. The brightness variations of the star during the post-maximum period include several days lasting flares and much more rare deep minima. The averaged colour-brightness relations are as follows: the higher brightness, the bluer B - V colour and the redder U - B colour. However the fast variations on a time scale of days do not always follow this relation. The observed pattern of variability of DR Tau is in agreement with the model of young stars activity (Grinin, 1980) proposing the appearance of hot spots in stellar atmosphere due to accretion of gas. Some arguments for the binarity of DR Tau are presented

  16. Broadband Wireline Provider Service Summary; BBRI_wirelineSum12

    Data.gov (United States)

    University of Rhode Island Geospatial Extension Program — This dataset represents the availability of broadband Internet access in Rhode Island via all wireline technologies assessed by Broadband Rhode Island. Broadband...

  17. A Method for Transferring Photoelectric Photometry Data from Apple II+ to IBM PC

    Science.gov (United States)

    Powell, Harry D.; Miller, James R.; Stephenson, Kipp

    1989-06-01

    A method is presented for transferring photoelectric photometry data files from an Apple II computer to an IBM PC computer in a form which is compatible with the AAVSO Photoelectric Photometry data collection process.

  18. Galileo Photometry of Asteroid 951 Gaspra

    Science.gov (United States)

    Helfenstein, P.; Veverka, J.; Thomas, P.C.; Simonelli, D.P.; Lee, P.; Klaasen, K.; Johnson, T.V.; Breneman, H.; Head, J.W.; Murchie, S.; Fanale, F.; Robinson, M.; Clark, B.; Granahan, J.; Garbeil, H.; McEwen, A.S.; Kirk, R.L.; Davies, M.; Neukum, G.; Mottola, S.; Wagner, R.; Belton, M.; Chapman, C.; Pilcher, C.

    1994-01-01

    Galileo images of Gaspra make it possible for the first time to determine a main-belt asteroid's photometric properties accurately by providing surface-resolved coverage over a wide range of incidence and emission angles and by extending the phase angle coverage to phases not observable from Earth. We combine Earth-based telescopic photometry over phase angles 2?? ??? ?? ??? 25?? with Galileo whole-disk and disk-resolved data at 33?? ??? ?? ??? 51?? to derive average global photometric properties in terms of Hapke's photometric model. The microscopic texture and particle phase-function behavior of Gaspra's surface are remarkably like those of other airless rocky bodies such as the Moon. The macroscopic surface roughness parameter, ??̄ = 29??, is slightly larger than that reported for typical lunar materials. The particle single scattering albedo, ??́0 = 0.36 ?? 0.07, is significantly larger than for lunar materials, and the opposition surge amplitude, B0 = 1.63 ?? 0.07, is correspondingly smaller. We determine a visual geometric albedo pv = 0.22 ?? 0.06 for Gaspra, in close agreement with pv = 0.22 ?? 0.03 estimated from Earth-based observations. Gaspra's phase integral is 0.47, and the bolometric Bond albedo is estimated to be 0.12 ?? 0.03. An albedo map derived by correcting Galileo images with our average global photometric function reveals subdued albedo contrasts of ??10% or less over Gaspra's northern hemisphere. Several independent classification algorithms confirm the subtle spectral heterogeneity reported earlier (S. Mottola, M. DiMartino, M. Gonano-Beurer, H. Hoffman, and G. Neukum, 1993, Asteroids, Comets, Meteors, pp. 421-424; M. J. S. Belton et al., 1992, Science 257, 1647-1652). Whole-disk colors (0.41 ??? ?? ??? 0.99 ??m) vary systematically with longitude by about ??5%, but color differences as large as 30% occur locally. Colors vary continuously between end-member materials whose areal distribution correlates with regional topography. Infrared

  19. SPITZER IRAC SECONDARY ECLIPSE PHOTOMETRY OF THE TRANSITING EXTRASOLAR PLANET HAT-P-1b

    International Nuclear Information System (INIS)

    Todorov, Kamen; Deming, Drake; Harrington, Jospeph; Stevenson, Kevin B.; Bowman, William C.; Nymeyer, Sarah; Fortney, Jonathan J.; Bakos, Gaspar A.

    2010-01-01

    We report Spitzer/IRAC photometry of the transiting giant exoplanet HAT-P-1b during its secondary eclipse. This planet lies near the postulated boundary between the pM and pL-class of hot Jupiters, and is important as a test of models for temperature inversions in hot Jupiter atmospheres. We derive eclipse depths for HAT-P-1b, in units of the stellar flux, that are: 0.080% ± 0.008% [3.6 μm], 0.135% ± 0.022% [4.5 μm], 0.203% ± 0.031% [5.8 μm], and 0.238% ± 0.040% [8.0 μm]. These values are best fit using an atmosphere with a modest temperature inversion, intermediate between the archetype inverted atmosphere (HD 209458b) and a model without an inversion. The observations also suggest that this planet is radiating a large fraction of the available stellar irradiance on its dayside, with little available for redistribution by circulation. This planet has sometimes been speculated to be inflated by tidal dissipation, based on its large radius in discovery observations, and on a non-zero orbital eccentricity allowed by the radial velocity data. The timing of the secondary eclipse is very sensitive to orbital eccentricity, and we find that the central phase of the eclipse is 0.4999 ± 0.0005. The difference between the expected and observed phase indicates that the orbit is close to circular, with a 3σ limit of |e cos ω| < 0.002.

  20. 75 FR 10464 - Broadband Technology Opportunities Program

    Science.gov (United States)

    2010-03-08

    ... window for Public Computer Center (PCC) and Sustainable Broadband Adoption (SBA) projects. DATES: All...; Extension of Application Closing Deadline for Comprehensive Community Infrastructure (CCI) Projects. SUMMARY... Infrastructure (CCI) projects under the Broadband Technology Opportunities Program (BTOP) is extended until 5:00...

  1. Broadband for all closing the infrastructure gap

    CSIR Research Space (South Africa)

    Roux, K

    2015-10-01

    Full Text Available than just addressing the infrastructure issue. The CSIR is mapping the country’s broadband infrastructure to understand where the largest gaps are, is developing models for how those gaps in broadband infrastructure can be closed. In this presentation...

  2. Customer Churn Prediction for Broadband Internet Services

    Science.gov (United States)

    Huang, B. Q.; Kechadi, M.-T.; Buckley, B.

    Although churn prediction has been an area of research in the voice branch of telecommunications services, more focused studies on the huge growth area of Broadband Internet services are limited. Therefore, this paper presents a new set of features for broadband Internet customer churn prediction, based on Henley segments, the broadband usage, dial types, the spend of dial-up, line-information, bill and payment information, account information. Then the four prediction techniques (Logistic Regressions, Decision Trees, Multilayer Perceptron Neural Networks and Support Vector Machines) are applied in customer churn, based on the new features. Finally, the evaluation of new features and a comparative analysis of the predictors are made for broadband customer churn prediction. The experimental results show that the new features with these four modelling techniques are efficient for customer churn prediction in the broadband service field.

  3. The High Road to Astronomical Photometric Precision : Differential Photometry

    NARCIS (Netherlands)

    Milone, E. F.; Pel, Jan Willem

    2011-01-01

    Differential photometry offers the most precise method for measuring the brightness of astronomical objects. We attempt to demonstrate why this should be the case, and then describe how well it has been done through a review of the application of differential techniques from the earliest visual

  4. Photometry and models of eight near-Earth asteroids

    Czech Academy of Sciences Publication Activity Database

    Kaasalainen, M.; Pravec, Petr; Krugly, Yu. N.; Kotková, Lenka; Torppa, J.; Virtanen, J.; Kaasalainen, S.; Erikson, A.; Nathues, A.; Ďurech, J.; Wolf, M.; Lagerros, J. S. V.; Lindgren, M.; Lagerkvist, C.-I.; Koff, R.; Davies, J.; Mann, R.; Kušnirák, Peter; Gaftonyuk, N. M.; Shevchenko, V. G.; Chiorny, V. G.; Belskaya, I. N.

    2004-01-01

    Roč. 167, č. 1 (2004), s. 178-196 ISSN 0019-1035 R&D Projects: GA AV ČR IAA3003204; GA ČR GA205/99/0255 Institutional research plan: CEZ:AV0Z1003909 Keywords : asteroids * rotation * photometry Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 3.074, year: 2004

  5. 3-color photometry of a sunspot using speckle masking techniques

    NARCIS (Netherlands)

    Wiehr, E.; Sütterlin, P.

    1998-01-01

    A three-colour photometry is used to deduce the temperature of sunspot fine-structures. Using the Speckle-Masking method for image restoration, the resulting images (one per colour and burst) have a spatial resolution only limited by the telescope's aperture, i.e. 95km (blue), 145 km (red) and

  6. The possibilities of CCD photometry of optical afterglows of GRBs

    Czech Academy of Sciences Publication Activity Database

    Šimon, Vojtěch; Polášek, Cyril; Jelínek, M.; Hudec, René; Štrobl, Jan

    -, č. 125 (2010), s. 24-28 ISSN 1801-5964. [Conference on Variable Stars Research /41./. Prague, 27.11.2009-29.11.2009] Institutional research plan: CEZ:AV0Z10030501 Keywords : gamma-ray bursts * optical afterglows * CCD photometry Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  7. Near-infrared photometry of bright elliptical galaxies

    NARCIS (Netherlands)

    Peletier, R. F.; Valentijn, E. A.; Jameson, R. F.

    High-quality visual-infrared color profiles have been determined for elliptical galaxies for the first time. Surface photometry in J and K is presented for 12 bright elliptical galaxies, and the results have been combined with CCD data in visual passbands. It is shown that the galaxies become bluer

  8. CCD photometry of apparent dwarf galaxies in Fornax

    International Nuclear Information System (INIS)

    Phillipps, S.; Grimley, P.L.; Disney, M.J.; Cawson, M.G.M.; Kibblewhite, E.J.

    1986-01-01

    Blue and red CCD surface photometry of two apparent dwarf galaxies in the Fornax cluster region is presented. Luminosity profiles are derived and their form discussed. The fainter galaxy resembles an archetypal diffuse dwarf elliptical but the brighter of the pair is either an unusual red dwarf or a background galaxy in chance juxtaposition. (author)

  9. The Carnegie Supernova Project. I. Third Photometry Data Release of Low-redshift Type Ia Supernovae and Other White Dwarf Explosions

    Science.gov (United States)

    Krisciunas, Kevin; Contreras, Carlos; Burns, Christopher R.; Phillips, M. M.; Stritzinger, Maximilian D.; Morrell, Nidia; Hamuy, Mario; Anais, Jorge; Boldt, Luis; Busta, Luis; Campillay, Abdo; Castellón, Sergio; Folatelli, Gastón; Freedman, Wendy L.; González, Consuelo; Hsiao, Eric Y.; Krzeminski, Wojtek; Persson, Sven Eric; Roth, Miguel; Salgado, Francisco; Serón, Jacqueline; Suntzeff, Nicholas B.; Torres, Simón; Filippenko, Alexei V.; Li, Weidong; Madore, Barry F.; DePoy, D. L.; Marshall, Jennifer L.; Rheault, Jean-Philippe; Villanueva, Steven

    2017-11-01

    We present final natural-system optical (ugriBV) and near-infrared (YJH) photometry of 134 supernovae (SNe) with probable white dwarf progenitors that were observed in 2004-2009 as part of the first stage of the Carnegie Supernova Project (CSP-I). The sample consists of 123 Type Ia SNe, 5 Type Iax SNe, 2 super-Chandrasekhar SN candidates, 2 Type Ia SNe interacting with circumstellar matter, and 2 SN 2006bt-like events. The redshifts of the objects range from z=0.0037 to 0.0835; the median redshift is 0.0241. For 120 (90%) of these SNe, near-infrared photometry was obtained. Average optical extinction coefficients and color terms are derived and demonstrated to be stable during the five CSP-I observing campaigns. Measurements of the CSP-I near-infrared bandpasses are also described, and near-infrared color terms are estimated through synthetic photometry of stellar atmosphere models. Optical and near-infrared magnitudes of local sequences of tertiary standard stars for each supernova are given, and a new calibration of Y-band magnitudes of the Persson et al. standards in the CSP-I natural system is presented.

  10. Broadband spectral observation of a dMe star radio flare

    International Nuclear Information System (INIS)

    Guedel, M.; Benz, A.O.; Fuerst, E.; Simett, G.M.; Davis, R.J.

    1989-01-01

    A flare on the dMe star AD Leonis was simultaneously observed with the radio telescopes in Effelsberg, Jodrell Bank, and Arecibo using spectrometers at 1665, 166 and 1415 MHz with bandwidths of 25, 100 and 40 MHz respectively. The time coincidence confirms the stellar origin of the radiation. The flare emission was resolved into a multitude of broadband pulsations. The e-folding rise and decay times were of the order of the time resolution of the Effelsberg data (125 ms), or less. The circular polarization was ∼ 100%. Similar bursts, but 4 orders of magnitude less powerful, have been observed from the sun at lower frequencies

  11. Recovering the Properties of High-redshift Galaxies with Different JWST Broadband Filters

    DEFF Research Database (Denmark)

    Bisigello, L.; Caputi, K. I.; Colina, L.

    2017-01-01

    Imaging with the James Webb Space Telescope (JWST) will allow observations of the bulk of distant galaxies at the epoch of reionization. The recovery of their properties, such as age, color excess , specific star formation rate (sSFR), and stellar mass, will mostly rely on spectral energy...... of these galaxy properties. We performed our tests on a sample of 1542 simulated galaxies, with known input properties, at z = 7–10. We found that, with only eight NIRCam broadbands, we can recover the galaxy age within 0.1 Gyr and the color excess within 0.06 mag for 70% of the galaxies. Additionally...

  12. A large catalog of accurate distances to molecular clouds from PS1 photometry

    Energy Technology Data Exchange (ETDEWEB)

    Schlafly, E. F.; Rix, H.-W.; Martin, N. F. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Green, G.; Finkbeiner, D. P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Bell, E. F. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Burgett, W. S.; Chambers, K. C.; Hodapp, K. W.; Kaiser, N.; Magnier, E. A.; Tonry, J. L. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Draper, P. W.; Metcalfe, N. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Price, P. A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

    2014-05-01

    Distance measurements to molecular clouds are important but are often made separately for each cloud of interest, employing very different data and techniques. We present a large, homogeneous catalog of distances to molecular clouds, most of which are of unprecedented accuracy. We determine distances using optical photometry of stars along lines of sight toward these clouds, obtained from PanSTARRS-1. We simultaneously infer the reddenings and distances to these stars, tracking the full probability distribution function using a technique presented in Green et al. We fit these star-by-star measurements using a simple dust screen model to find the distance to each cloud. We thus estimate the distances to almost all of the clouds in the Magnani et al. catalog, as well as many other well-studied clouds, including Orion, Perseus, Taurus, Cepheus, Polaris, California, and Monoceros R2, avoiding only the inner Galaxy. Typical statistical uncertainties in the distances are 5%, though the systematic uncertainty stemming from the quality of our stellar models is about 10%. The resulting catalog is the largest catalog of accurate, directly measured distances to molecular clouds. Our distance estimates are generally consistent with available distance estimates from the literature, though in some cases the literature estimates are off by a factor of more than two.

  13. Engineering aspects of compact stellarators

    International Nuclear Information System (INIS)

    Nelson, B.E.; Benson, R.D.; Brooks, A.

    2003-01-01

    Compact stellarators could combine the good confinement and high beta of a tokamak with the inherently steady state, disruption-free characteristics of a stellarator. Two U.S. compact stellarator facilities are now in the conceptual design phase: the National Compact Stellarator Experiment (NCSX) and the Quasi- Poloidal Stellarator (QPS). NCSX has a major radius of 1.4 m and a toroidal field up to 2 T. The primary feature of both NCSX and QPS is the set of modular coils that provide the basic magnetic configuration. These coils represent a major engineering challenge due to the complex shape, precise geometric accuracy, and high current density of the windings. The winding geometry is too complex for conventional hollow copper conductor construction. Instead, the modular coils will be wound with flexible, multi strand cable conductor that has been compacted to a 75% copper packing fraction. Inside the NCSX coil set and surrounding the plasma is a highly contoured vacuum vessel. The vessel consists of three identical, 120 deg. segments that are bolted together at double sealed joints. The QPS device has a major radius of 0.9 m, a toroidal field of 1 T, and an aspect ratio of only 2.7. Instead of an internal vacuum vessel, the QPS modular coils will operate in an external vacuum tank. (author)

  14. LACK OF INFLATED RADII FOR KEPLER GIANT PLANET CANDIDATES RECEIVING MODEST STELLAR IRRADIATION

    International Nuclear Information System (INIS)

    Demory, Brice-Olivier; Seager, Sara

    2011-01-01

    The most irradiated transiting hot Jupiters are characterized by anomalously inflated radii, sometimes exceeding Jupiter's size by more than 60%. While different theoretical explanations have been applied, none of them provide a universal resolution to this observation, despite significant progress in the past years. We refine the photometric transit light curve analysis of 115 Kepler giant planet candidates based on public Q0-Q2 photometry. We find that 14% of them are likely false positives, based on their secondary eclipse depth. We report on planet radii versus stellar flux. We find an increase in planet radii with increased stellar irradiation for the Kepler giant planet candidates, in good agreement with existing hot Jupiter systems. We find that in the case of modest irradiation received from the stellar host, giant planets do not have inflated radii, and appear to have radii independent of the host star incident flux. This finding suggests that the physical mechanisms inflating hot Jupiters become ineffective below a given orbit-averaged stellar irradiation level of ∼2 × 10 8 erg s –1 cm –2 .

  15. MASSCLEANCOLORS-MASS-DEPENDENT INTEGRATED COLORS FOR STELLAR CLUSTERS DERIVED FROM 30 MILLION MONTE CARLO SIMULATIONS

    International Nuclear Information System (INIS)

    Popescu, Bogdan; Hanson, M. M.

    2010-01-01

    We present Monte Carlo models of open stellar clusters with the purpose of mapping out the behavior of integrated colors with mass and age. Our cluster simulation package allows for stochastic variations in the stellar mass function to evaluate variations in integrated cluster properties. We find that UBVK colors from our simulations are consistent with simple stellar population (SSP) models, provided the cluster mass is large, M cluster ≥ 10 6 M sun . Below this mass, our simulations show two significant effects. First, the mean value of the distribution of integrated colors moves away from the SSP predictions and is less red, in the first 10 7 to 10 8 years in UBV colors, and for all ages in (V - K). Second, the 1σ dispersion of observed colors increases significantly with lower cluster mass. We attribute the former to the reduced number of red luminous stars in most of the lower mass clusters and the latter to the increased stochastic effect of a few of these stars on lower mass clusters. This latter point was always assumed to occur, but we now provide the first public code able to quantify this effect. We are completing a more extensive database of magnitudes and colors as a function of stellar cluster age and mass that will allow the determination of the correlation coefficients among different bands, and improve estimates of cluster age and mass from integrated photometry.

  16. VizieR Online Data Catalog: CATalog of Stellar Unified Properties (Hinkel+, 2017)

    Science.gov (United States)

    Hinkel, N. R.; Mamajek, E. E.; Turnbull, M. C.; Osby, E.; Shkolnik, E. L.; Smith, G. H.; Klimasewski, A.; Somers, G.; Desch, S. J.

    2017-11-01

    We have assembled a data set of stellar properties for 951 FGK-type stars within 30pc of the Sun. Beginning with the Gaia (Cat. I/337) TGAS subset of astrometric data, we have combined information regarding multiplicity within stellar systems (ExoCat, Gray et al., 2003, Cat. J/AJ/126/2048; 2006, Cat. J/AJ/132/161; Valenti & Fischer 2005, Cat. J/ApJS/159/141; Takeda et al. 2007, Cat. J/PASJ/59/1127), stellar abundance measurements (Hypatia, Hinkel et al. 2014, Cat. J/AJ/148/54; 2016ApJS..226....4H), standardized spectral types, Ca II H and K stellar activity indices, NUV and FUV photometry from GALEX (Cat. II/312), and X-ray fluxes and luminosities from ROSAT (Cat. IX/10), XMM (Cat. IX/50), and Chandra (Cat. IX/45). The aim of this project was to collate a wide variety of data for nearby stars such that they could be more easily characterized. The information available in CATSUP can be utilized for the direct sample or act as a proxy for similar stars, in order to better understand the overall trends within solar neighborhood stars, as well as stars that host exoplanets. CATSUP was compiled in anticipation of upcoming exoplanet surveys such as TESS, CHEOPS, and WFIRST. (1 data file).

  17. Stellar Oxygen Abundances

    Science.gov (United States)

    King, Jeremy

    1994-04-01

    This dissertation addresses several issues concerning stellar oxygen abundances. The 7774 {\\AA} O I triplet equivalent widths of Abia & Rebolo [1989, AJ, 347, 186] for metal-poor dwarfs are found to be systematically too high. I also argue that current effective temperatures used in halo star abundance studies may be ~150 K too low. New color-Teff relations are derived for metal-poor stars. Using the revised Teff values and improved equivalent widths for the 7774A O I triplet, the mean [O/Fe] ratio for a handful of halo stars is found to be +0.52 with no dependence on Teff or [Fe/H]. Possible cosmological implications of the hotter Teff scale are discussed along with additional evidence supporting the need for a higher temperature scale for metal-poor stars. Our Teff scale leads to a Spite Li plateau value of N(Li)=2.28 +/- 0.09. A conservative minimal primordial value of N(Li)=2.35 is inferred. If errors in the observations and models are considered, consistency with standard models of Big Bang nucleosynthesis is still achieved with this larger Li abundance. The revised Teff scale raises the observed B/Be ratio of HD 140283 from 10 to 12, making its value more comfortably consistent with the production of the observed B and Be by ordinary spallation. Our Teff values are found to be in good agreement with values predicted from both the Victoria and Yale isochrone color-Teff relations. Thus, it appears likely that no changes in globular cluster ages would result. Next, we examine the location of the break in the [O/Fe] versus [Fe/H] plane in a quantitative fashion. Analysis of a relatively homogeneous data set does not favor any unique break point in the range -1.7 /= -3), in agreement with the new results for halo dwarfs. We find that the gap in the observed [O/H] distribution, noted by Wheeler et al. [1989, ARAA, 27, 279], persists despite the addition of more O data and may betray the occurrence of a hiatus in star formation between the end of halo formation and

  18. Kepler Stellar Properties Catalog Update for Q1-Q17 DR25 Transit Search

    Science.gov (United States)

    Mathur, Savita; Huber, Daniel

    2016-01-01

    Huber et al. (2014) presented revised stellar properties for 196,468 Kepler targets, which were used for the Q1-Q16 TPSDV planet search (Tenenbaum et al. 2014). The catalog was based on atmospheric properties (i.e., temperature (Teff), surface gravity (log(g)), and metallicity ([FeH])) published in the literature using a variety of methods (e.g., asteroseismology, spectroscopy, exoplanet transits, photometry), which were then homogeneously fitted to a grid of Dartmouth (DSEP) isochrones (Dotter et al. 2008). The catalog was updated in early 2015 for the Q1-Q17 Data Release (DR) 24 transit search (Seader et al. 2015) based on the latest classifications of Kepler targets in the literature at that time. The methodology followed Huber et al. (2014). Here we provide updated stellar properties of 197,096 Kepler targets. Like the previous catalog, this update is based on atmospheric properties that were either published in the literature or provided by the Kepler community follow-up program (CFOP). The input values again come from different methods: asteroseismology, spectroscopy, flicker, and photometry. This catalog update was developed to support the SOC 9.3 TPSDV planet search (Twicken et al. 2016), which is expected to be the final search and data release by the Kepler project.In this document, we describe the method and the inputs that were used to build the catalog. The methodology follows Huber et al. (2014) with a few improvements as described in Section 2.

  19. AIRTV: Broadband Direct to Aircraft

    Science.gov (United States)

    Sorbello, R.; Stone, R.; Bennett, S. B.; Bertenyi, E.

    2002-01-01

    Airlines have been continuously upgrading their wide-body, long-haul aircraft with IFE (in-flight entertainment) systems that can support from 12 to 24 channels of video entertainment as well as provide the infrastructure to enable in-seat delivery of email and internet services. This is a direct consequence of increased passenger demands for improved in-flight services along with the expectations that broadband delivery systems capable of providing live entertainment (news, sports, financial information, etc.) and high speed data delivery will soon be available. The recent events of Sept. 11 have slowed the airline's upgrade of their IFE systems, but have also highlighted the compelling need for broadband aeronautical delivery systems to include operational and safety information. Despite the impact of these events, it is estimated that by 2005 more than 3000 long haul aircraft (servicing approximately 1 billion passengers annually) will be fully equipped with modern IFE systems. Current aircraft data delivery systems, which use either Inmarsat or NATS, are lacking in bandwidth and consequently are unsuitable to satisfy passenger demands for broadband email/internet services or the airlines' burgeoning data requirements. Present live video delivery services are limited to regional coverage and are not readily expandable to global or multiregional service. Faced with a compelling market demand for high data transport to aircraft, AirTV has been developing a broadband delivery system that will meet both passengers' and airlines' needs. AirTV is a global content delivery system designed to provide a range of video programming and data services to commercial airlines. When AirTV is operational in 2004, it will provide a broadband connection directly to the aircraft, delivering live video entertainment, internet/email service and essential operational and safety data. The system has been designed to provide seamless global service to all airline routes except for those

  20. Spectral Irradiance Calibration in the Infrared. XVII. Zero-Magnitude Broadband Flux Reference for Visible-to-Infrared Photometry

    Science.gov (United States)

    2010-12-01

    Cousins UBVRI system and Rieke et al. (2008, their Table 3) for wavelengths beyond 1 nm ( 2MASS , Two Micron All Sky Survey, JHKS, Cutri el al. 2003...Rieke et al.’s Table 11 lists 2MASS JHK, and Hipparcos Vcolors for 57 A0 V stars and defines their average colors with an internal precision of ±0.003...27.084 0.006 -27.070 -0.008 Cousins / -27.415 -27.412 -0.003 -27.412 -0.003 Mean A ± rms -0.005 ± 0.013 -0.011 ± 0.007 2MASS J -27.881 -27.886 0.005

  1. Broadband Photometry Of The Potentially Asteroid 277475 (2005 WK4) and Corrected 52762 (1998 MT24) Colors.

    Science.gov (United States)

    Hicks, M.; Buratt, B.; Carcione, A.; Borlase, R.

    2013-08-01

    The Near-Earth Object (NEO) 277475 (2005 WK4) was discovered by the Siding Spring Survey (MPEC 2005-W79) on November 27, 2005. With a Minimum Orbit Intersection Distance (MOID) of 0.004 AU and absolute magnitude H_V=20.1 mag, this object has been designated a Potentially Hazardous Asteroid (PHA) by the Minor Planet Center. The asteroid made an Earth close-approach of 0.021 AU on August 09.2, 2013 and was extensively imaged by the JPL Planetary Radar Team ( http://www.jpl.nasa.gov/news/news.php?release=2013-254 ).

  2. Planets, stars and stellar systems

    CERN Document Server

    Bond, Howard; McLean, Ian; Barstow, Martin; Gilmore, Gerard; Keel, William; French, Linda

    2013-01-01

    This is volume 3 of Planets, Stars and Stellar Systems, a six-volume compendium of modern astronomical research covering subjects of key interest to the main fields of contemporary astronomy. This volume on “Solar and Stellar Planetary Systems” edited by Linda French and Paul Kalas presents accessible review chapters From Disks to Planets, Dynamical Evolution of Planetary Systems, The Terrestrial Planets, Gas and Ice Giant Interiors, Atmospheres of Jovian Planets, Planetary Magnetospheres, Planetary Rings, An Overview of the Asteroids and Meteorites, Dusty Planetary Systems and Exoplanet Detection Methods. All chapters of the handbook were written by practicing professionals. They include sufficient background material and references to the current literature to allow readers to learn enough about a specialty within astronomy, astrophysics and cosmology to get started on their own practical research projects. In the spirit of the series Stars and Stellar Systems published by Chicago University Press in...

  3. VizieR Online Data Catalog: HK photometry in an UCHII region near Sh2-217 (Brand+, 2011)

    Science.gov (United States)

    Brand, J.; Massi, F.; Zavagno, A.; Deharveng, L.; Lefloch, B.

    2010-11-01

    Coordinates and photometric parameters (magnitudes and colours) are presented of the stars located in a molecular condensation on the SW-border of the Galactic HII region Sh2-217. The data were obtained on January 4, 2004 with the 3.58-m Telescopio Nazionale Galileo (TNG; La Palma, Canary Islands, Spain). Near-infrared observations were carried out through H and K' broad-band filters with the camera NICS. The image scale is 0.25arcsec/pixel, yielding a field of view of about 4.2'x4.2'. Observing strategy and exposure times are described in Deharveng et al. (2006A&A...458..191D), the only difference being that the dithering sequence for the H-band images was the same as adopted for K'. The data reduction steps adopted are outlined in Deharveng et al. (2006A&A...458..191D). Aperture photometry was done using the DAOPHOT package in IRAF. We followed the same procedure described in Deharveng et al. (2006A&A...458..191D) to obtain aperture photometry, after which PSF-fitting photometry was performed. Although the seeing was good (<1"), the night was barely photometric, so we calibrated our H, K' photometry with that performed on the same field by Deharveng et al. (2003, Cat. J/A+A/399/1135). We calculated the difference in magnitudes for each coinciding source and plotted it against our derived instrumental H-K'. A colour term was present in K' because of the difference between the K and K' filters. After a best-fit calibration, a residual r.m.s. of about 0.2mag. was present in the difference between our photometry and that of Deharveng et al. (2003, J/A+A/399/1135), probably because of the different seeing and possibly also due to the intrinsic variability of young stars. Our photometry is thus on the same HK standard system as Deharveng et al. (2003, J/A+A/399/1135). Sources with K, H < 11-12 are in the non-linear regime or saturated, but such bright objects are few in number and lie outside the cluster, and are probably foreground stars. The approximate limiting

  4. Stellar CME candidates: towards a stellar CME-flare relation

    Science.gov (United States)

    Paraskevi Moschou, Sofia; Drake, Jeremy J.; Cohen, Ofer; Alvarado-Gomez, Julian D.; Garraffo, Cecilia

    2018-06-01

    For decades the Sun has been the only star that allowed for direct CME observations. Recently, with the discovery of multiple extrasolar systems, it has become imperative that the role of stellar CMEs be assessed in the context of exoplanetary habitability. Solar CMEs and flares show a higher association with increasing flaring energy, with strong flares corresponding to large and fast CMEs. As argued in earlier studies, extrasolar environments around active stars are potentially dominated by CMEs, as a result of their extreme flaring activity. This has strong implications for the energy budget of the system and the atmospheric erosion of orbiting planets.Nevertheless, with current instrumentation we are unable to directly observe CMEs in even the closest stars, and thus we have to look for indirect techniques and observational evidence and signatures for the eruption of stellar CMEs. There are three major observational techniques for tracing CME signatures in other stellar systems, namely measuring Type II radio bursts, Doppler shifts in UV/optical lines or transient absorption in the X-ray spectrum. We present observations of the most probable stellar CME candidates captured so far and examine the different observational techniques used together with their levels of uncertainty. Assuming that they were CMEs, we try to asses their kinematic and energetic characteristics and place them in an extension of the well-established solar CME-flare energy scaling law. We finish by discussing future observations for direct measurements.

  5. Advent of broadband public-switched communications

    Science.gov (United States)

    Casey, John J.

    1992-02-01

    Advances in data communications infrastructure, display technology, and man-machine interfaces have changed business applications and the requirements of public network data transport. These changes have created opportunities for a new generation of public broadband services to more efficiently extend high speed communications capabilities beyond the customer premises. This paper provides a view of the technology and market evolution of these public broadband data communications services, and suggests early customer networked applications that justify the deployment of a public switched broadband network infrastructure.

  6. The TERMS Project: Improved Orbital Parameters and Photometry of HD168443 and the Photometry Pipeline

    Science.gov (United States)

    Pilyavsky, Genady; Mahadevan, S.; Kane, S. R.; Howard, A. W.; Ciardi, D. R.; de Pree, C.; Dragomir, D.; Fischer, D.; Henry, G. W.; Jensen, E. L. N.; Laughlin, G.; Marlowe, H.; Rabus, M.; von Braun, K.; Wright, J. T.; Wang, X.

    2012-01-01

    The discovery of transiting planets around bright stars holds the potential to greatly enhance our understanding of planetary atmospheres. The Transit Ephemeris Refinement and Monitoring Survey (TERMS) project focuses on updating the ephemerides of known exoplanets, put tighter constraints on the orbital parameters and shrink the large errors on the predicted transit windows, enabling photometric monitoring to search for a transit signature. Here, we present the revised orbital parameters and the photometric coverage during a predicted transit window of HD168443b, a massive planet orbiting the bright star HD 168443 (V = 6.92) with a period of 58.11 days. The high eccentricity of the planetary orbit (e = 0.53) significantly enhances the a-priori transit probability (3.7%) from what is expected for a circular orbit (2.5%). The transit ephemeris was updated using refined orbital parameters from additional Keck-HIRES radial velocities. The photometry obtained at the 1 m telescope in Cerro Tololo Inter-American Observatory (CTIO) and the T8 0.8 m Automated Photometric Telescope (APT) at Fairborn Observatory achieved the necessary millimag precision. The expected change in flux (0.5%) for HD168443 was not observed during the predicted transit window, thus allowing us to rule out the transit and put tighter constrains on the orbital inclination of HD168443b. Additionally, we present the software used to analyze the CTIO data. Developed by the TERMS team, this IDL based package is a fast, precise, and easy to use program which has eliminated the need for external software and command line prompts by utilizing the functionality of a graphical user interface (GUI).

  7. 47 CFR 27.1305 - Shared wireless broadband network.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Shared wireless broadband network. 27.1305... broadband network. The Shared Wireless Broadband Network developed by the 700 MHz Public/Private Partnership must be designed to meet requirements associated with a nationwide, public safety broadband network. At...

  8. 47 CFR 90.1405 - Shared wireless broadband network.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Shared wireless broadband network. 90.1405... broadband network. The Shared Wireless Broadband Network developed by the 700 MHz Public/Private Partnership must be designed to meet requirements associated with a nationwide, public safety broadband network. At...

  9. Precision Stellar and Planetary Astrophysics with TESS and Gaia

    Science.gov (United States)

    Stevens, Daniel J.; KELT Collaboration

    2018-01-01

    There is an ever-present need for precise and accurate stellar parameters, particularly for low-mass stars. For example, some fraction of measured M dwarf radii are inflated and have effective temperatures that are suppressed relative to predictions from models, but the physical cause of these effects is still uncertain. This is exacerbated by the fact that only a handful of M dwarfs -- all from double-lined eclipsing binaries (EBs) -- have both masses and radii measured to 3% or better. In the Gaia era, we can now measure model-independent masses and radii for single-lined EBs, thus expanding the sample of stars with precisely measured parameters by at least an order of magnitude, in principle. I will illustrate how one can combine Gaia parallaxes and broad-band stellar fluxes with the eclipse and radial velocity data to provide model-independent masses and radii. I will present our expected achievable constraints on the masses and radii of single-lined EBs. I will discuss both our current effort to turn several dozens of single-lined EBs discovered by the KELT and HATNet surveys into a catalog of exquisitely characterized stars and exoplanets as well as the prospects for achieving similar science for a much larger number of systems with TESS.

  10. Stellar populations in the Carina region. The Galactic plane at l = 291°

    Science.gov (United States)

    Molina-Lera, J. A.; Baume, G.; Gamen, R.; Costa, E.; Carraro, G.

    2016-08-01

    Context. Previous studies of the Carina region have revealed its complexity and richness as well as a significant number of early-type stars. However, in many cases, these studies only concentrated on the central region (Trumpler 14/16) or were not homogeneous. This latter aspect, in particular, is crucial because very different ages and distances for key clusters have been claimed in recent years. Aims: The aim of this work is to study in detail an area of the Galactic plane in Carina, eastward η Carina. We analyze the properties of different stellar populations and focus on a sample of open clusters and their population of young stellar objects and highly reddened early stars. We also studied the stellar mass distribution in these clusters and the possible scenario of their formation. Finally, we outline the Galactic spiral structure in this direction. Methods: We obtained deep and homogeneous photometric data (UBVIKC) for six young open clusters: NGC 3752, Trumpler 18, NGC 3590, Hogg 10, 11, and 12, located in Carina at l ~ 291°, and their adjacent stellar fields, which we complemented with spectroscopic observations of a few selected targets. We also culled additional information from the literature, which includes stellar spectral classifications and near-infrared photometry from 2MASS. We finally developed a numerical code that allowed us to perform a homogeneous and systematic analysis of the data. Our results provide more reliable estimates of distances, color excesses, masses, and ages of the stellar populations in this direction. Results: We estimate the basic parameters of the studied clusters and find that they identify two overdensities of young stellar populations located at about 1.8 kpc and 2.8 kpc, with EB - V ~ 0.1 - 0.6. We find evidence of pre-main-sequence populations inside them, with an apparent coeval stellar formation in the most conspicuous clusters. We also discuss apparent age and distance gradients in the direction NW-SE. We study the

  11. Science with Synthetic Stellar Surveys

    Science.gov (United States)

    Sanderson, Robyn Ellyn

    2018-04-01

    A new generation of observational projects is poised to revolutionize our understanding of the resolved stellar populations of Milky-Way-like galaxies at an unprecedented level of detail, ushering in an era of precision studies of galaxy formation. In the Milky Way itself, astrometric, spectroscopic and photometric surveys will measure three-dimensional positions and velocities and numerous chemical abundances for stars from the disk to the halo, as well as for many satellite dwarf galaxies. In the Local Group and beyond, HST, JWST and eventually WFIRST will deliver pristine views of resolved stars. The groundbreaking scale and dimensionality of this new view of resolved stellar populations in galaxies challenge us to develop new theoretical tools to robustly compare these surveys to simulated galaxies, in order to take full advantage of our new ability to make detailed predictions for stellar populations within a cosmological context. I will describe a framework for generating realistic synthetic star catalogs and mock surveys from state-of-the-art cosmological-hydrodynamical simulations, and present several early scientific results from, and predictions for, resolved stellar surveys of our Galaxy and its neighbors.

  12. Maximum stellar iron core mass

    Indian Academy of Sciences (India)

    An analytical method of estimating the mass of a stellar iron core, just prior to core collapse, is described in this paper. The method employed depends, in part, upon an estimate of the true relativistic mass increase experienced by electrons within a highly compressed iron core, just prior to core collapse, and is significantly ...

  13. Maximum stellar iron core mass

    Indian Academy of Sciences (India)

    60, No. 3. — journal of. March 2003 physics pp. 415–422. Maximum stellar iron core mass. F W GIACOBBE. Chicago Research Center/American Air Liquide ... iron core compression due to the weight of non-ferrous matter overlying the iron cores within large .... thermal equilibrium velocities will tend to be non-relativistic.

  14. Integrated Circuit Stellar Magnitude Simulator

    Science.gov (United States)

    Blackburn, James A.

    1978-01-01

    Describes an electronic circuit which can be used to demonstrate the stellar magnitude scale. Six rectangular light-emitting diodes with independently adjustable duty cycles represent stars of magnitudes 1 through 6. Experimentally verifies the logarithmic response of the eye. (Author/GA)

  15. Stellar dynamics and black holes

    Indian Academy of Sciences (India)

    Chandrasekhar's most important contribution to stellar dynamics was the concept of dynamical friction. I briefly review that work, then discuss some implications of Chandrasekhar's theory of gravitational encounters for motion in galactic nuclei. Author Affiliations. David Merritt1. Department of Physics, Rochester Institute ...

  16. TEM turbulence optimisation in stellarators

    Science.gov (United States)

    Proll, J. H. E.; Mynick, H. E.; Xanthopoulos, P.; Lazerson, S. A.; Faber, B. J.

    2016-01-01

    With the advent of neoclassically optimised stellarators, optimising stellarators for turbulent transport is an important next step. The reduction of ion-temperature-gradient-driven turbulence has been achieved via shaping of the magnetic field, and the reduction of trapped-electron mode (TEM) turbulence is addressed in the present paper. Recent analytical and numerical findings suggest TEMs are stabilised when a large fraction of trapped particles experiences favourable bounce-averaged curvature. This is the case for example in Wendelstein 7-X (Beidler et al 1990 Fusion Technol. 17 148) and other Helias-type stellarators. Using this knowledge, a proxy function was designed to estimate the TEM dynamics, allowing optimal configurations for TEM stability to be determined with the STELLOPT (Spong et al 2001 Nucl. Fusion 41 711) code without extensive turbulence simulations. A first proof-of-principle optimised equilibrium stemming from the TEM-dominated stellarator experiment HSX (Anderson et al 1995 Fusion Technol. 27 273) is presented for which a reduction of the linear growth rates is achieved over a broad range of the operational parameter space. As an important consequence of this property, the turbulent heat flux levels are reduced compared with the initial configuration.

  17. Analysis of United States' Broadband Policy

    National Research Council Canada - National Science Library

    Uzarski, Joel S

    2007-01-01

    .... With every month that passes, the United States fails to close the gap in the digital divide both inside its borders as well as among the other countries that lead the world in broadband penetration...

  18. Energy efficiency in future wireless broadband networks

    CSIR Research Space (South Africa)

    Masonta, MT

    2012-10-01

    Full Text Available greener economy and environment. In this research, we investigate the concept of green radio communications in wireless networks and discuss approaches for energy efficient solutions in wireless broadband network deployments. These solutions include...

  19. Analyzing Broadband Divide in the Farming Sector

    DEFF Research Database (Denmark)

    Jensen, Michael; Gutierrez Lopez, Jose Manuel; Pedersen, Jens Myrup

    2013-01-01

    , upstream and downstream connection. The main constraint is that farms are naturally located in rural areas where the required access broadband data rates are not available. This paper studies the broadband divide in relation to the Danish agricultural sector. Results show how there is an important......Agriculture industry has been evolving for centuries. Currently, the technological development of Internet oriented farming tools allows to increase the productivity and efficiency of this sector. Many of the already available tools and applications require high bandwidth in both directions...... difference between the broadband availability for farms and the rest of the households/buildings the country. This divide may be slowing down the potential technological development of the farming industry, in order to keep their competitiveness in the market. Therefore, broadband development in rural areas...

  20. Catalyzing Broadband Internet in Africa | IDRC - International ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    ... generates a 1.4% increase in gross domestic product (GDP) in low-income countries. ... Africa offers a good example of the potential benefits and challenges of ... the policy challenges related to providing affordable broadband services; ...

  1. Nanophotonic Design for Broadband Light Management

    Energy Technology Data Exchange (ETDEWEB)

    Kosten, Emily; Callahan, Dennis; Horowitz, Kelsey; Pala, Ragip; Atwater, Harry

    2014-10-13

    We describe nanophotonic design approaches for broadband light management including i) crossed-trapezoidal Si structures ii) Si photonic crystal superlattices, and iii) tapered and inhomogeneous diameter III-V/Si nanowire arrays.

  2. An ultra-broadband multilayered graphene absorber

    KAUST Repository

    Amin, Muhammad; Farhat, Mohamed; Bagci, Hakan

    2013-01-01

    An ultra-broadband multilayered graphene absorber operating at terahertz (THz) frequencies is proposed. The absorber design makes use of three mechanisms: (i) The graphene layers are asymmetrically patterned to support higher order surface plasmon

  3. Wireless Broadband Access and Accounting Schemes

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    In this paper, we propose two wireless broadband access and accounting schemes. In both schemes, the accounting system adopts RADIUS protocol, but the access system adopts SSH and SSL protocols respectively.

  4. BV photographic and CCD photometry of IC 4651

    International Nuclear Information System (INIS)

    Anthony-Twarog, B.J.; Mukherjee, K.; Twarog, B.A.; Caldwell, N.

    1988-01-01

    A BV photometric survey in IC 4651 based on photographic and CCD material calibrated with photoelectric photometry from Eggen (1971) and Anthony-Twarog and Twarog (1987) has been completed. The color-magnitude diagram is consistent with an age of 2.4 + or - 0.3 x 10 to the 9th yr derived by comparison with the isochrones of VandenBerg (1985) if the apparent distance modulus and reddening derived from uvby photometry in Anthony-Twarog and Twarog (1987) are employed. While evidence is found of a hook in the upper main sequence, no evidence is found of a significantly bifurcated main sequence for this cluster, although it is similar in age to NGC 752 and NGC 3680, where this phenomenon has been noted. Finally, the survey has not resolved the apparent deficit of main-sequence stars fainter than V = 14.5 noted in Anthony-Twarog and Twarog (1987). 16 references

  5. Broadband and Unbundling Regulations in OECD Countries

    OpenAIRE

    Wallsten, Scott

    2006-01-01

    Broadband penetration and available speeds vary widely across OECD countries. Policymakers around the world, and especially in countries like the U.S. that lag in the rankings, are searching for policies to narrow those gaps. Relatively little empirical work tests possible reasons for these differences. In this paper I test the impacts of regulations and demographics on broadband development in a panel dataset across countries. In addition to adding to the meager empirical literature on broad...

  6. Stellar Parameters for Trappist-1

    Science.gov (United States)

    Van Grootel, Valérie; Fernandes, Catarina S.; Gillon, Michael; Jehin, Emmanuel; Manfroid, Jean; Scuflaire, Richard; Burgasser, Adam J.; Barkaoui, Khalid; Benkhaldoun, Zouhair; Burdanov, Artem; Delrez, Laetitia; Demory, Brice-Olivier; de Wit, Julien; Queloz, Didier; Triaud, Amaury H. M. J.

    2018-01-01

    TRAPPIST-1 is an ultracool dwarf star transited by seven Earth-sized planets, for which thorough characterization of atmospheric properties, surface conditions encompassing habitability, and internal compositions is possible with current and next-generation telescopes. Accurate modeling of the star is essential to achieve this goal. We aim to obtain updated stellar parameters for TRAPPIST-1 based on new measurements and evolutionary models, compared to those used in discovery studies. We present a new measurement for the parallax of TRAPPIST-1, 82.4 ± 0.8 mas, based on 188 epochs of observations with the TRAPPIST and Liverpool Telescopes from 2013 to 2016. This revised parallax yields an updated luminosity of {L}* =(5.22+/- 0.19)× {10}-4 {L}ȯ , which is very close to the previous estimate but almost two times more precise. We next present an updated estimate for TRAPPIST-1 stellar mass, based on two approaches: mass from stellar evolution modeling, and empirical mass derived from dynamical masses of equivalently classified ultracool dwarfs in astrometric binaries. We combine them using a Monte-Carlo approach to derive a semi-empirical estimate for the mass of TRAPPIST-1. We also derive estimate for the radius by combining this mass with stellar density inferred from transits, as well as an estimate for the effective temperature from our revised luminosity and radius. Our final results are {M}* =0.089+/- 0.006 {M}ȯ , {R}* =0.121+/- 0.003 {R}ȯ , and {T}{eff} = 2516 ± 41 K. Considering the degree to which the TRAPPIST-1 system will be scrutinized in coming years, these revised and more precise stellar parameters should be considered when assessing the properties of TRAPPIST-1 planets.

  7. Infrared polarimetry and photometry of BL Lac objects. 2

    Energy Technology Data Exchange (ETDEWEB)

    Impey, C D [Hawaii Univ., Honolulu (USA). Inst. for Astronomy; Brand, P W.J.L. [Edinburgh Univ. (UK). Dept. of Astronomy; Wolstencroft, R D [Royal Observatory, Edinburgh (UK); Williams, P M [United Kingdom Infrared Telescope Unit, Hilo, Hawaii (USA)

    1984-07-15

    Photometry and polarimetry in the JHK wavebands have now been obtained for 25 BL Lac objects. Several new objects have been monitored for periods of up to five days, and accumulated data is sufficient for a statistical analysis of polarization properties. The selection effects operating on this sample are examined first. A power-law spectrum is consistent with the spectra of all but three objects. A number of important new results are reported.

  8. Infrared polarimetry and photometry of BL Lac objects

    International Nuclear Information System (INIS)

    Impey, C.D.; Williams, P.M.

    1984-01-01

    Photometry and polarimetry in the JHK wavebands have now been obtained for 25 BL Lac objects. Several new objects have been monitored for periods of up to five days, and accumulated data is sufficient for a statistical analysis of polarization properties. The selection effects operating on this sample are examined first. A power-law spectrum is consistent with the spectra of all but three objects. A number of important new results are reported. (author)

  9. CCD photometry of Cepheid sequences in four nearby galaxies

    International Nuclear Information System (INIS)

    Metcalfe, N.; Shanks, T.

    1991-01-01

    We present Isaac Newton Telescope B and V CCD observations of deep photometric sequences in the vicinity of Cepheid variable stars in three nearby galaxies - M31, M33 and NGC 2403. We have also checked the photometry of the brightest stars in M81 and its dwarf companion, Holmberg IX. We use our data, combined with other recent results, to re-analyse the Cepheid distances to these galaxies. (author)

  10. CCD Photometry of W UMa Type Binary TY UMa

    Directory of Open Access Journals (Sweden)

    Young Woon Kang

    2001-06-01

    Full Text Available We present VRI CCD photometry of W UMa type binary TY UMa. The light curves show that the secondary minimum is deeper than theprimary minimum and the maximum I (0.p25 is 0.m023 brighter than the maximum II (0.p75. The V light curve has beenanalyzed and the photometric solutions have been determined by the method of Wilson & Devinney differential correction. Weadopted the spot model to explain the asymetric light curve.

  11. Long-Term Photometry of Very Slow Novae

    Directory of Open Access Journals (Sweden)

    Chochol D.

    2003-12-01

    Full Text Available Long-term photographic, photoelectric and recent CCD photometry of the classical nova V723 Cas and symbiotic novae V1329 Cyg, PU Vul, V1016 Cyg and HM Sge were used to find their orbital periods. The arguments in favor of the presence of the third components in these systems are given. Physical processes, responsible for the brightness variations, are discussed.

  12. Targeted Optimization of Quasi-Symmetric Stellarators

    International Nuclear Information System (INIS)

    Hegna, Chris C.; Talmadge, J. N.

    2016-01-01

    The proposed research focuses on targeted areas of plasma physics dedicated to improving the stellarator concept. Research was pursued in the technical areas of edge/divertor physics in 3D configurations, magnetic island physics in stellarators, the role of 3D shaping on microinstabilities and turbulent transport and energetic ion confinement in stellarators.

  13. Targeted Optimization of Quasi-Symmetric Stellarators

    Energy Technology Data Exchange (ETDEWEB)

    Hegna, Chris C. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Engineering Physics; Anderson, D. T. [Univ. of Wisconsin, Madison, WI (United States); Talmadge, J. N. [Univ. of Wisconsin, Madison, WI (United States)

    2016-10-06

    The proposed research focuses on targeted areas of plasma physics dedicated to improving the stellarator concept. Research was pursued in the technical areas of edge/divertor physics in 3D configurations, magnetic island physics in stellarators, the role of 3D shaping on microinstabilities and turbulent transport and energetic ion confinement in stellarators.

  14. AGES AND METALLICITIES OF CLUSTER GALAXIES IN A779 USING MODIFIED STROeMGREN PHOTOMETRY

    Energy Technology Data Exchange (ETDEWEB)

    Sreedhar, Yuvraj Harsha; Rakos, Karl D.; Hensler, Gerhard; Zeilinger, Werner W. [University of Vienna, Institute of Astronomy, Tuerkenschanzstrasse 17, A-1180 Vienna (Austria); Odell, Andrew P. [Department of Physics and Astronomy, Northern Arizona University, Flagstaff, AZ (United States)

    2012-03-01

    In the quest for the formation and evolution of galaxy clusters, Rakos and co-workers introduced a spectrophotometric method using modified Stroemgren photometry, but with the considerable debate toward the project's abilities, we re-introduce the system by testing for the repeatability of the modified Stroemgren colors and compare them with the Stroemgren colors, and check for the reproducibility of the ages and metallicities (using the Principle Component Analysis (PCA) technique and the GALEV models) for the six common galaxies in all three A779 data sets. As a result, a fair agreement between two filter systems was found to produce similar colors (with a precision of 0.09 mag in (uz - vz), 0.02 mag in (bz - yz), and 0.03 mag in (vz - vz)) and the generated ages and metallicities are also similar (with an uncertainty of 0.36 Gyr and 0.04 dex from PCA and 0.44 Gyr and 0.2 dex using the GALEV models). We infer that the technique is able to relieve the age-metallicity degeneracy by separating the age effects from the metallicity effects, but it is still unable to completely eliminate it. We further extend this paper to re-study the evolution of galaxies in the low mass, dynamically poor A779 cluster (as it was not elaborately analyzed by Rakos and co-workers in their previous work) by correlating the luminosity (mass), density, and radial distance with the estimated age, metallicity, and the star formation history. Our results distinctly show the bimodality of the young, low-mass, metal-poor population with a mean age of 6.7 Gyr ({+-} 0.5 Gyr) and the old, high-mass, metal-rich galaxies with a mean age of 9 Gyr ({+-} 0.5 Gyr). The method also observes the color evolution of the blue cluster galaxies to red (Butcher-Oemler phenomenon), and the downsizing phenomenon. Our analysis shows that modified Stroemgren photometry is very well suited for studying low- and intermediate-z clusters, as it is capable of observing deeper with better spatial resolution at

  15. Broadband electromagnetic environments simulator (EMES)

    International Nuclear Information System (INIS)

    Pollard, N.

    1977-01-01

    A new test facility has been developed by Sandia Laboratories for determining the effects of electromagnetic environments on systems and components. The facility is capable of producing uniform, vertically polarized, continuous wave (CW) and pulsed fields over the frequency range of dc to 10 GHz. This broadband capability addresses the electromagnetic radiation (EMR) threat and is ideally suited to computer controlled sweeping and data acquisition. EMES is also capable of producing uniform transient fields having the wave shape and magnitude characteristic of a nuclear electromagnetic pulse (EMP) and near lightning. The design consists of a truncated, triplate, rectangular coaxial transmission line. The spacing between the flat center conductor and the ground planes is 4 meters. The line is terminated in its characteristic impedance of 50 ohms. At frequencies below the first resonance of the facility it behaves as a typical coaxial system. Above resonance, a wall of electromagnetic absorbing material provides a nonreflecting termination. Thus, EMES essentially combines the elements of a transmission line and an anechoic chamber. It will not radiate electromagnetic energy into the surrounding area because it is a shielded transmission line

  16. Broadband direct RF digitization receivers

    CERN Document Server

    Jamin, Olivier

    2014-01-01

    This book discusses the trade-offs involved in designing direct RF digitization receivers for the radio frequency and digital signal processing domains.  A system-level framework is developed, quantifying the relevant impairments of the signal processing chain, through a comprehensive system-level analysis.  Special focus is given to noise analysis (thermal noise, quantization noise, saturation noise, signal-dependent noise), broadband non-linear distortion analysis, including the impact of the sampling strategy (low-pass, band-pass), analysis of time-interleaved ADC channel mismatches, sampling clock purity and digital channel selection. The system-level framework described is applied to the design of a cable multi-channel RF direct digitization receiver. An optimum RF signal conditioning, and some algorithms (automatic gain control loop, RF front-end amplitude equalization control loop) are used to relax the requirements of a 2.7GHz 11-bit ADC. A two-chip implementation is presented, using BiCMOS and 65nm...

  17. A broadband accelerator control network

    International Nuclear Information System (INIS)

    Skelly, J.; Clifford, T.; Frankel, R.

    1983-01-01

    A broadband data communications network has been implemented at BNL for control of the Alternating Gradient Synchrotron (AGS) proton accelerator, using commercial CATV hardware, dual coaxial cables as the communications medium, and spanning 2.0 km. A 4 MHz bandwidth Digital Control Channel using CSMA-CA protocol is provided for digital data transmission, with 8 access nodes available over the length of the RELWAY. Each node consists of an rf modem and a microprocessor-based store-and-forward message handler which interfaces the RELWAY to a branch line implemented in GPIB. A gateway to the RELWAY control channel for the (preexisting) AGS Computerized Accelerator Operating System has been constructed using an LSI-11/23 microprocessor as a device in a GPIB branch line. A multilayer communications protocol has been defined for the Digital Control Channel, based on the ISO Open Systems Interconnect layered model, and a RELWAY Device Language defined as the required universal language for device control on this channel

  18. Ultra-broadband photonic internet

    Science.gov (United States)

    Romaniuk, Ryszard S.

    2011-06-01

    In this paper, there is presented a review of our today's understanding of the ultimately broadband photonic Internet. A simple calculation is presented showing the estimate of the throughput of the core photonic network branches. Optoelectronic components, circuits, systems and signals, together with analogous electronic entities and common software layers, are building blocks of the contemporary Internet. Participation of photonics in development of the physical layer in the future Internet will probably increase. The photonics leads now to a better usage of the available bandwidth (increase of the spectral efficiency measured in Bit/s/Hz), increase in the transmission rate (from Gbps, via Tbps up to probably Pbps), increase in the transmission distance without signal regeneration (in distortion compensated active optical cables), increase in energy/power efficiency measured in W/Gbps, etc. Photonics may lead, in the future, to fully transparent optical networks and, thus, to essential increase in bandwidth and network reliability. It is expected that photonics (with biochemistry, electronics and mechatronics) may build psychological and physiological interface for humans to the future global network. The following optical signal multiplexing methods were considered, which are possible without O/E/O conversion: TDM-OTDM, FDM-CO-OFDM, OCDM-OCDMA, WDM-DWDM.

  19. STELLAR ACTIVITY AND ITS IMPLICATIONS FOR EXOPLANET DETECTION ON GJ 176

    International Nuclear Information System (INIS)

    Robertson, Paul; Endl, Michael; Cochran, William D.; MacQueen, Phillip J.; Henry, Gregory W.; Williamson, Michael H.

    2015-01-01

    We present an in-depth analysis of stellar activity and its effects on radial velocity (RV) for the M2 dwarf GJ 176 based on spectra taken over 10 yr from the High Resolution Spectrograph on the Hobby-Eberly Telescope. These data are supplemented with spectra from previous observations with the HIRES and HARPS spectrographs, and V- and R-band photometry taken over six years at the Dyer and Fairborn observatories. Previous studies of GJ 176 revealed a super-Earth exoplanet in an 8.8-day orbit. However, the velocities of this star are also known to be contaminated by activity, particularly at the 39-day stellar rotation period. We have examined the magnetic activity of GJ 176 using the sodium I D lines, which have been shown to be a sensitive activity tracer in cool stars. In addition to rotational modulation, we see evidence of a long-term trend in our Na I D index, which may be part of a long-period activity cycle. The sodium index is well correlated with our RVs, and we show that this activity trend drives a corresponding slope in RV. Interestingly, the rotation signal remains in phase in photometry, but not in the spectral activity indicators. We interpret this phenomenon as the result of one or more large spot complexes or active regions which dominate the photometric variability, while the spectral indices are driven by the overall magnetic activity across the stellar surface. In light of these results, we discuss the potential for correcting activity signals in the RVs of M dwarfs

  20. Data Release of UV to Submillimeter Broadband Fluxes for Simulated Galaxies from the EAGLE Project

    Science.gov (United States)

    Camps, Peter; Trčka, Ana; Trayford, James; Baes, Maarten; Theuns, Tom; Crain, Robert A.; McAlpine, Stuart; Schaller, Matthieu; Schaye, Joop

    2018-02-01

    We present dust-attenuated and dust emission fluxes for sufficiently resolved galaxies in the EAGLE suite of cosmological hydrodynamical simulations, calculated with the SKIRT radiative transfer code. The post-processing procedure includes specific components for star formation regions, stellar sources, and diffuse dust and takes into account stochastic heating of dust grains to obtain realistic broadband fluxes in the wavelength range from ultraviolet to submillimeter. The mock survey includes nearly half a million simulated galaxies with stellar masses above {10}8.5 {M}ȯ across six EAGLE models. About two-thirds of these galaxies, residing in 23 redshift bins up to z = 6, have a sufficiently resolved metallic gas distribution to derive meaningful dust attenuation and emission, with the important caveat that the same dust properties were used at all redshifts. These newly released data complement the already publicly available information about the EAGLE galaxies, which includes intrinsic properties derived by aggregating the properties of the smoothed particles representing matter in the simulation. We further provide an open-source framework of Python procedures for post-processing simulated galaxies with the radiative transfer code SKIRT. The framework allows any third party to calculate synthetic images, spectral energy distributions, and broadband fluxes for EAGLE galaxies, taking into account the effects of dust attenuation and emission.

  1. DIRECTED SEARCHES FOR BROADBAND EXTENDED GRAVITATIONAL WAVE EMISSION IN NEARBY ENERGETIC CORE-COLLAPSE SUPERNOVAE

    Energy Technology Data Exchange (ETDEWEB)

    Van Putten, Maurice H. P. M., E-mail: mvp@sejong.ac.kr [Room 614, Astronomy and Space Science, Sejong University, 98 Gunja-Dong Gwangin-gu, Seoul 143-747 (Korea, Republic of)

    2016-03-10

    Core-collapse supernovae (CC-SNe) are factories of neutron stars and stellar-mass black holes. SNe Ib/c stand out as potentially originating in relatively compact stellar binaries and they have a branching ratio of about 1% into long gamma-ray bursts. The most energetic events probably derive from central engines harboring rapidly rotating black holes, wherein the accretion of fall-back matter down to the innermost stable circular orbit (ISCO) offers a window into broadband extended gravitational wave emission (BEGE). To search for BEGE, we introduce a butterfly filter in time–frequency space by time-sliced matched filtering. To analyze long epochs of data, we propose using coarse-grained searches followed by high-resolution searches on events of interest. We illustrate our proposed coarse-grained search on two weeks of LIGO S6 data prior to SN 2010br (z = 0.002339) using a bank of up to 64,000 templates of one-second duration covering a broad range in chirp frequencies and bandwidth. Correlating events with signal-to-noise ratios > 6 from the LIGO L1 and H1 detectors reduces the total to a few events of interest. Lacking any further properties reflecting a common excitation by broadband gravitational radiation, we disregarded these as spurious. This new pipeline may be used to systematically search for long-duration chirps in nearby CC-SNe from robotic optical transient surveys using embarrassingly parallel computing.

  2. VizieR Online Data Catalog: Standard Galactic field RR Lyrae. I. Photometry (Monson+, 2017)

    Science.gov (United States)

    Monson, A. J.; Beaton, R. L.; Scowcroft, V.; Freedman, W. L.; Madore, B. F.; Rich, J. A.; Seibert, M.; Kollmeier, J. A.; Clementini, G.

    2017-06-01

    The Three-hundred MilliMeter Telescope (TMMT) is a fully robotic, 300mm telescope at Las Campanas Observatory (LCO), for which the nightly operation and data processing have been completely automated. Over the course of two years data were collected on 179 individual nights for our sample of the 55 RR Lyrae in the B, V, and IC broadband filters. Of these nights, 76 were under photometric conditions and calibrated directly. The 103 nonphotometric nights were roughly calibrated by using the default transformation equations, but only provide differential photometry relative to the calibrated frames. This resulted in 59698 final individual observations. Individual data points have a typical photometric precision of 0.02mag. The statistical error falls rapidly with hundreds of observations, with the zero-point uncertainties being the largest source of uncertainty in the final reported mean magnitude. To compare the results of our TMMT campaign to previous studies of these RR Lyrae (RRL) and to fill gaps in our TMMT phase coverage, we have compiled available broadband data from literature published over the past 30 years and spanning our full wavelength coverage (0.4 to 4.5μm) from the optical to mid-infrared. We have homogenized these diverse data sets to the following filter systems: Johnson UBV, Kron-Cousins RI, 2MASS J,H,Ks, and Spitzer [3.6], [4.5]. The All Sky Automated Survey (ASAS; http://www.astrouw.edu.pl/asas/) is a long-term project monitoring all stars brighter than V~14mag. The program covers both hemispheres, with telescopes at Las Campanas Observatory in Chile and Haleakala on Maui, both of which provide simultaneous I and V photometry. The GEOS RR Lyr Survey (http://www.ast.obs-mip.fr/users/leborgne/dbRR/grrs.html) is a long-term program utilizing TAROT (http://tarot.obs-hp.fr/) at Calern Observatory (Nice University, France). Annual data releases from this project add times for maximum light for program stars over the last year of observations. In

  3. THE INFORMATION CONTENT IN ANALYTIC SPOT MODELS OF BROADBAND PRECISION LIGHT CURVES

    Energy Technology Data Exchange (ETDEWEB)

    Walkowicz, Lucianne M. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, 4 Ivy Lane, Princeton, NJ 08534 (United States); Basri, Gibor [Astronomy Department, University of California at Berkeley, Hearst Field Annex, Berkeley, CA 94720 (United States); Valenti, Jeff A. [Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States)

    2013-04-01

    We present the results of numerical experiments to assess degeneracies in light curve models of starspots. Using synthetic light curves generated with the Cheetah starspot modeling code, we explore the extent to which photometric light curves constrain spot model parameters, including spot latitudes and stellar inclination. We also investigate the effects of spot parameters and differential rotation on one's ability to correctly recover rotation periods and differential rotation in the Kepler light curves. We confirm that in the absence of additional constraints on the stellar inclination, such as spectroscopic measurements of vsin i or occultations of starspots by planetary transits, the spot latitude and stellar inclination are difficult to determine uniquely from the photometry alone. We find that for models with no differential rotation, spots that appear on opposite hemispheres of the star may cause one to interpret the rotation period to be half of the true period. When differential rotation is included, the changing longitude separation between spots breaks the symmetry of the hemispheres and the correct rotation period is more likely to be found. The dominant period found via periodogram analysis is typically that of the largest spot. Even when multiple spots with periods representative of the star's differential rotation exist, if one spot dominates the light curve the signal of differential rotation may not be detectable from the periodogram alone. Starspot modeling is applicable to stars with a wider range of rotation rates than other surface imaging techniques (such as Doppler imaging), allows subtle signatures of differential rotation to be measured, and may provide valuable information on the distribution of stellar spots. However, given the inherent degeneracies and uncertainty present in starspot models, caution should be exercised in their interpretation.

  4. THE INFORMATION CONTENT IN ANALYTIC SPOT MODELS OF BROADBAND PRECISION LIGHT CURVES

    International Nuclear Information System (INIS)

    Walkowicz, Lucianne M.; Basri, Gibor; Valenti, Jeff A.

    2013-01-01

    We present the results of numerical experiments to assess degeneracies in light curve models of starspots. Using synthetic light curves generated with the Cheetah starspot modeling code, we explore the extent to which photometric light curves constrain spot model parameters, including spot latitudes and stellar inclination. We also investigate the effects of spot parameters and differential rotation on one's ability to correctly recover rotation periods and differential rotation in the Kepler light curves. We confirm that in the absence of additional constraints on the stellar inclination, such as spectroscopic measurements of vsin i or occultations of starspots by planetary transits, the spot latitude and stellar inclination are difficult to determine uniquely from the photometry alone. We find that for models with no differential rotation, spots that appear on opposite hemispheres of the star may cause one to interpret the rotation period to be half of the true period. When differential rotation is included, the changing longitude separation between spots breaks the symmetry of the hemispheres and the correct rotation period is more likely to be found. The dominant period found via periodogram analysis is typically that of the largest spot. Even when multiple spots with periods representative of the star's differential rotation exist, if one spot dominates the light curve the signal of differential rotation may not be detectable from the periodogram alone. Starspot modeling is applicable to stars with a wider range of rotation rates than other surface imaging techniques (such as Doppler imaging), allows subtle signatures of differential rotation to be measured, and may provide valuable information on the distribution of stellar spots. However, given the inherent degeneracies and uncertainty present in starspot models, caution should be exercised in their interpretation.

  5. Direct UV-Written Integrated Optical Beam Combiner for Stellar Interferometry

    DEFF Research Database (Denmark)

    Olivero, Massimo; Svalgaard, Mikael; Jocou, L.

    2007-01-01

    In this paper, we report the fabrication of an optical-beam combiner for stellar interferometry by means of direct ultraviolet (UV) writing. The component is shown to have good performance (fringe contrast > 95%, total loss similar to 0.7, -40-dB crosstalk, broadband operation covering at least...... the range 1.49-1.65 mu m, and low differential chromatic dispersion). The overall performance exceeds that of similar components currently used for astronomical research. This result, combined with the fast-prototyping ability of UV writing, opens up new possibilities for the realization of highly optimized...

  6. Broadband in schools: towards a definition and model of broadband for South African schools

    CSIR Research Space (South Africa)

    Ford, Merryl

    2017-05-01

    Full Text Available South Africa is about to provide broadband internet connectivity to all schools in the country via the implementation of the national broadband policy. The challenge is to ensure a balance between the schools’ demand-side usage and supply...

  7. Broad-band beam buncher

    International Nuclear Information System (INIS)

    Goldberg, D.A.; Flood, W.S.; Arthur, A.A.; Voelker, F.

    1986-01-01

    This patent describes a broad-band beam buncher. This beam buncher consists of: a housing adapted to be eacuated, an electron gun in the housing for producing a beam of electrons, buncher means in the housing forming a buncher cavity which has an entrance opening for receiving the electron beam and an exit opening through which the electron beam passes out of the buncher cavity, a drift tube electrode in the buncher cavity and disposed between the entrance opening and the exit opening with first and second gaps between the drift tube electrode and the entrance and exit openings, the drift tube electrode which has a first drift space through which the electron beam passes in traveling between the entrance and exit openings, modulating means for supplying an ultrahigh frequeny modulating signal to the drift tube electrode for producing velocity modulation of the electrons in the electron beam as the electrons pass through the buncher cavity and the drift tube electrode between the entrance opening and the exit opening, drift space means in the housing forming a second drift space for receiving the velocity modulated electron beam from the exit opening, the velocity modulated electron beam being bunched as it passes along the second drift space, the drift space means has a discharge opening through which the electron beam is discharged from the second drift space after being bunched therein, the modulating means containing a signal source for producing an ultrahigh frequency signal, a transmission line connected between the signal source and the drift tube electrode, and terminating means connected to the drift tube electrode for terminating the transmission line in approximately its characteristic impedance to afford a broad response band with minimum 6 variations therein

  8. Characterizing stellar and exoplanetary environments

    CERN Document Server

    Khodachenko, Maxim

    2015-01-01

    In this book an international group of specialists discusses studies of exoplanets subjected to extreme stellar radiation and plasma conditions. It is shown that such studies will help us to understand how terrestrial planets and their atmospheres, including the early Venus, Earth and Mars, evolved during the host star’s active early phase. The book presents an analysis of findings from Hubble Space Telescope observations of transiting exoplanets, as well as applications of advanced numerical models for characterizing the upper atmosphere structure and stellar environments of exoplanets. The authors also address detections of atoms and molecules in the atmosphere of “hot Jupiters” by NASA’s Spitzer telescope. The observational and theoretical investigations and discoveries presented are both timely and important in the context of the next generation of space telescopes. 
 The book is divided into four main parts, grouping chapters on exoplanet host star radiation and plasma environments, exoplanet u...

  9. Modular Stellarator Fusion Reactor concept

    International Nuclear Information System (INIS)

    Miller, R.L.; Krakowski, R.A.

    1981-08-01

    A preliminary conceptual study is made of the Modular Stellarator Reactor (MSR). A steady-state ignited, DT-fueled, magnetic fusion reactor is proposed for use as a central electric-power station. The MSR concept combines the physics of the classic stellarator confinement topology with an innovative, modular-coil design. Parametric tradeoff calculations are described, leading to the selection of an interim design point for a 4-GWt plant based on Alcator transport scaling and an average beta value of 0.04 in an l = 2 system with a plasma aspect ratio of 11. The physics basis of the design point is described together with supporting magnetics, coil-force, and stress computations. The approach and results presented herein will be modified in the course of ongoing work to form a firmer basis for a detailed conceptual design of the MSR

  10. Hydromagnetic instability in a stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Kruskal, M D; Gottlieb, M B; Johnson, J L; Goldman, L M [Project Matterhorn, Princeton University, Princeton, NJ (United States)

    1958-07-01

    It was noted that when there is a uniform externally imposed longitudinal field much larger than the field of the discharge current, one should expect instabilities in the form of a lateral displacement of the plasma column into a helix of large pitch. At the wavelength of fastest growth the e-folding time approximates the time it takes a sound wave in the plasma to traverse the radius of the plasma column. This problem has been re-examines under the conditions which might be expected to occur in the stellarator during ohmic heating, including the presence of external conductors. The theory is applied to the stellarator; and it is shown that the external conductors are in fact unimportant. The important effects due to the finite length of the Machine are discussed and the effects of more general current distributions are considered. The results from the experiments are given.

  11. STELLAR EVIDENCE THAT THE SOLAR DYNAMO MAY BE IN TRANSITION

    International Nuclear Information System (INIS)

    Metcalfe, Travis S.; Egeland, Ricky; Van Saders, Jennifer

    2016-01-01

    Precise photometry from the Kepler space telescope allows not only the measurement of rotation in solar-type field stars, but also the determination of reliable masses and ages from asteroseismology. These critical data have recently provided the first opportunity to calibrate rotation–age relations for stars older than the Sun. The evolutionary picture that emerges is surprising: beyond middle-age the efficiency of magnetic braking is dramatically reduced, implying a fundamental change in angular momentum loss beyond a critical Rossby number (Ro ∼ 2). We compile published chromospheric activity measurements for the sample of Kepler asteroseismic targets that were used to establish the new rotation–age relations. We use these data along with a sample of well-characterized solar analogs from the Mount Wilson HK survey to develop a qualitative scenario connecting the evolution of chromospheric activity to a fundamental shift in the character of differential rotation. We conclude that the Sun may be in a transitional evolutionary phase, and that its magnetic cycle might represent a special case of stellar dynamo theory.

  12. STELLAR EVIDENCE THAT THE SOLAR DYNAMO MAY BE IN TRANSITION

    Energy Technology Data Exchange (ETDEWEB)

    Metcalfe, Travis S. [Space Science Institute, 4750 Walnut Street, Suite 205, Boulder CO 80301 (United States); Egeland, Ricky [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder CO 80307 (United States); Van Saders, Jennifer [Carnegie Observatories, 813 Santa Barbara Street, Pasadena CA 91101 (United States)

    2016-07-20

    Precise photometry from the Kepler space telescope allows not only the measurement of rotation in solar-type field stars, but also the determination of reliable masses and ages from asteroseismology. These critical data have recently provided the first opportunity to calibrate rotation–age relations for stars older than the Sun. The evolutionary picture that emerges is surprising: beyond middle-age the efficiency of magnetic braking is dramatically reduced, implying a fundamental change in angular momentum loss beyond a critical Rossby number (Ro ∼ 2). We compile published chromospheric activity measurements for the sample of Kepler asteroseismic targets that were used to establish the new rotation–age relations. We use these data along with a sample of well-characterized solar analogs from the Mount Wilson HK survey to develop a qualitative scenario connecting the evolution of chromospheric activity to a fundamental shift in the character of differential rotation. We conclude that the Sun may be in a transitional evolutionary phase, and that its magnetic cycle might represent a special case of stellar dynamo theory.

  13. IRAS 20050+2720: ANATOMY OF A YOUNG STELLAR CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Guenther, H. M.; Wolk, S. J.; Spitzbart, B.; Forbrich, J.; Wright, N. J.; Bourke, T. L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gutermuth, R. A. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Allen, L. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Megeath, S. T. [Department of Physics and Astronomy, MS-113, University of Toledo, 2801 W. Bancroft St., Toledo, OH 43606 (United States); Pipher, J. L., E-mail: hguenther@cfa.harvard.edu [Department of Physics and Astronomy, University of Rochester, 500 Wilson Boulevard, Rochester, NY 14627 (United States)

    2012-10-01

    IRAS 20050+2720 is young star-forming region at a distance of 700 pc without apparent high-mass stars. We present results of our multi-wavelength study of IRAS 20050+2720 which includes observations by Chandra and Spitzer, and Two Micron All Sky Survey and UBVRI photometry. In total, about 300 young stellar objects (YSOs) in different evolutionary stages are found. We characterize the distribution of YSOs in this region using a minimum spanning tree analysis. We newly identify a second cluster core, which consists mostly of class II objects, about 10' from the center of the cloud. YSOs of earlier evolutionary stages are more clustered than more evolved objects. The X-ray luminosity function (XLF) of IRAS 20050+2720 is roughly lognormal, but steeper than the XLF of the more massive Orion Nebula complex. IRAS 20050+2720 shows a lower N{sub H}/A{sub K} ratio compared with the diffuse interstellar medium.

  14. ACCELERATED FITTING OF STELLAR SPECTRA

    Energy Technology Data Exchange (ETDEWEB)

    Ting, Yuan-Sen; Conroy, Charlie [Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Rix, Hans-Walter [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)

    2016-07-20

    Stellar spectra are often modeled and fitted by interpolating within a rectilinear grid of synthetic spectra to derive the stars’ labels: stellar parameters and elemental abundances. However, the number of synthetic spectra needed for a rectilinear grid grows exponentially with the label space dimensions, precluding the simultaneous and self-consistent fitting of more than a few elemental abundances. Shortcuts such as fitting subsets of labels separately can introduce unknown systematics and do not produce correct error covariances in the derived labels. In this paper we present a new approach—Convex Hull Adaptive Tessellation (chat)—which includes several new ideas for inexpensively generating a sufficient stellar synthetic library, using linear algebra and the concept of an adaptive, data-driven grid. A convex hull approximates the region where the data lie in the label space. A variety of tests with mock data sets demonstrate that chat can reduce the number of required synthetic model calculations by three orders of magnitude in an eight-dimensional label space. The reduction will be even larger for higher dimensional label spaces. In chat the computational effort increases only linearly with the number of labels that are fit simultaneously. Around each of these grid points in the label space an approximate synthetic spectrum can be generated through linear expansion using a set of “gradient spectra” that represent flux derivatives at every wavelength point with respect to all labels. These techniques provide new opportunities to fit the full stellar spectra from large surveys with 15–30 labels simultaneously.

  15. Grigori Kuzmin and Stellar Dynamics

    Directory of Open Access Journals (Sweden)

    Zeeuw P. Tim de

    2011-06-01

    Full Text Available Grigori Kuzmin was a very gifted dynamicist and one of the towering figures in the distinguished history of the Tartu Observatory. He obtained a number of important results in relative isolation which were later rediscovered in the West. This work laid the foundation for further advances in the theory of stellar systems in dynamical equilibrium, thereby substantially increasing our understanding of galaxy dynamics.

  16. Geometry Dependence of Stellarator Turbulence

    International Nuclear Information System (INIS)

    Mynick, H.E.; Xanthopoulos, P.; Boozer, A.H.

    2009-01-01

    Using the nonlinear gyrokinetic code package GENE/GIST, we study the turbulent transport in a broad family of stellarator designs, to understand the geometry-dependence of the microturbulence. By using a set of flux tubes on a given flux surface, we construct a picture of the 2D structure of the microturbulence over that surface, and relate this to relevant geometric quantities, such as the curvature, local shear, and effective potential in the Schrodinger-like equation governing linear drift modes

  17. The ALHAMBRA survey: 2D analysis of the stellar populations in massive early-type galaxies at z < 0.3

    Science.gov (United States)

    San Roman, I.; Cenarro, A. J.; Díaz-García, L. A.; López-Sanjuan, C.; Varela, J.; González Delgado, R. M.; Sánchez-Blázquez, P.; Alfaro, E. J.; Ascaso, B.; Bonoli, S.; Borlaff, A.; Castander, F. J.; Cerviño, M.; Fernández-Soto, A.; Márquez, I.; Masegosa, J.; Muniesa, D.; Pović, M.; Viironen, K.; Aguerri, J. A. L.; Benítez, N.; Broadhurst, T.; Cabrera-Caño, J.; Cepa, J.; Cristóbal-Hornillos, D.; Infante, L.; Martínez, V. J.; Moles, M.; del Olmo, A.; Perea, J.; Prada, F.; Quintana, J. M.

    2018-01-01

    We present a technique that permits the analysis of stellar population gradients in a relatively low-cost way compared to integral field unit (IFU) surveys. We developed a technique to analyze unresolved stellar populations of spatially resolved galaxies based on photometric multi-filter surveys. This technique allows the analysis of vastly larger samples and out to larger galactic radii. We derived spatially resolved stellar population properties and radial gradients by applying a centroidal Voronoi tessellation and performing a multicolor photometry spectral energy distribution fitting. This technique has been successfully applied to a sample of 29 massive (M⋆ > 1010.5M⊙) early-type galaxies at z Max-Planck-Institut für Astronomie (MPIA) at Heidelberg and the Instituto de Astrofísica de Andalucía (CSIC).

  18. Models of hot stellar systems

    International Nuclear Information System (INIS)

    Van Albada, T.S.

    1986-01-01

    Elliptical galaxies consist almost entirely of stars. Sites of recent star formation are rare, and most stars are believed to be several billion years old, perhaps as old as the Universe itself (--10/sup 10/ yrs). Stellar motions in ellipticals show a modest amount of circulation about the center of the system, but most support against the force of gravity is provided by random motions; for this reason ellipticals are called 'hot' stellar systems. Spiral galaxies usually also contain an appreciable amount of gas (--10%, mainly atomic hydrogen) and new stars are continually being formed out of this gas, especially in the spiral arms. In contrast to ellipticals, support against gravity in spiral galaxies comes almost entirely from rotation; random motions of the stars with respect to rotation are small. Consequently, spiral galaxies are called 'cold' stellar systems. Other than in hot systems, in cold systems the collective response of stars to variations in the force field is an essential part of the dynamics. The present overview is limited to mathematical models of hot systems. Computational methods are also discussed

  19. Optimizing Methods of Obtaining Stellar Parameters for the H3 Survey

    Science.gov (United States)

    Ivory, KeShawn; Conroy, Charlie; Cargile, Phillip

    2018-01-01

    The Stellar Halo at High Resolution with Hectochelle Survey (H3) is in the process of observing and collecting stellar parameters for stars in the Milky Way's halo. With a goal of measuring radial velocities for fainter stars, it is crucial that we have optimal methods of obtaining this and other parameters from the data from these stars.The method currently developed is The Payne, named after Cecilia Payne-Gaposchkin, a code that uses neural networks and Markov Chain Monte Carlo methods to utilize both spectra and photometry to obtain values for stellar parameters. This project was to investigate the benefit of fitting both spectra and spectral energy distributions (SED). Mock spectra using the parameters of the Sun were created and noise was inserted at various signal to noise values. The Payne then fit each mock spectrum with and without a mock SED also generated from solar parameters. The result was that at high signal to noise, the spectrum dominated and the effect of fitting the SED was minimal. But at low signal to noise, the addition of the SED greatly decreased the standard deviation of the data and resulted in more accurate values for temperature and metallicity.

  20. Soap, A Free-code Tool To Study The Impact Of Stellar Activity

    Science.gov (United States)

    Boisse, Isabelle; Bonfils, X.; Santos, N.

    2011-09-01

    Dark spots and bright plages are present on the surface of all stars, even low-active stars (like the Sun in its low-active phase). 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 velocimetry and photometry. SOAP is a tool offered to the community (Boisse, Bonfils and Santos, in prep.) that enables to simulate spots and plages on rotating stars and computes their impact on RV and photometric measurements. This talk will discuss 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 will focus future projects like Elektra, SPIRou or CARMENES), limitation to the sum of different transit observations in order to characterize the atmospheric components (from the ground or with Spitzer, JWST), planets around young stars,... and how this can be simulated with SOAP in order to search for indices and corrections. IB and NCS would like to thank the support by the European Research Council/European Community under the FP7 through a Starting Grant, as well from Fundacao para a Ciencia e a Tecnologia (FCT), Portugal.

  1. Probing the Dusty Stellar Populations of the Local Volume Galaxies with JWST /MIRI

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Olivia C.; Meixner, Margaret [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, 21218 (United States); Justtanont, Kay [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-439 92 Onsala (Sweden); Glasse, Alistair [UK Astronomy Technology Centre, Royal Observatory, Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)

    2017-05-20

    The Mid-Infrared Instrument (MIRI) for the James Webb Space Telescope ( JWST ) will revolutionize our understanding of infrared stellar populations in the Local Volume. Using the rich Spitzer -IRS spectroscopic data set and spectral classifications from the Surveying the Agents of Galaxy Evolution (SAGE)–Spectroscopic survey of more than 1000 objects in the Magellanic Clouds, the Grid of Red Supergiant and Asymptotic Giant Branch Star Model (grams), and the grid of YSO models by Robitaille et al., we calculate the expected flux densities and colors in the MIRI broadband filters for prominent infrared stellar populations. We use these fluxes to explore the JWST /MIRI colors and magnitudes for composite stellar population studies of Local Volume galaxies. MIRI color classification schemes are presented; these diagrams provide a powerful means of identifying young stellar objects, evolved stars, and extragalactic background galaxies in Local Volume galaxies with a high degree of confidence. Finally, we examine which filter combinations are best for selecting populations of sources based on their JWST colors.

  2. The Hierarchical Distribution of the Young Stellar Clusters in Six Local Star-forming Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Grasha, K.; Calzetti, D. [Astronomy Department, University of Massachusetts, Amherst, MA 01003 (United States); Adamo, A.; Messa, M. [Dept. of Astronomy, The Oskar Klein Centre, Stockholm University, Stockholm (Sweden); Kim, H. [Gemini Observatory, La Serena (Chile); Elmegreen, B. G. [IBM Research Division, T.J. Watson Research Center, Yorktown Hts., NY (United States); Gouliermis, D. A. [Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Dale, D. A. [Dept. of Physics and Astronomy, University of Wyoming, Laramie, WY (United States); Fumagalli, M. [Institute for Computational Cosmology and Centre for Extragalactic Astronomy, Durham University, Durham (United Kingdom); Grebel, E. K.; Shabani, F. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, D-69120 Heidelberg (Germany); Johnson, K. E. [Dept. of Astronomy, University of Virginia, Charlottesville, VA (United States); Kahre, L. [Dept. of Astronomy, New Mexico State University, Las Cruces, NM (United States); Kennicutt, R. C. [Institute of Astronomy, University of Cambridge, Cambridge (United Kingdom); Pellerin, A. [Dept. of Physics and Astronomy, State University of New York at Geneseo, Geneseo NY (United States); Ryon, J. E.; Ubeda, L. [Space Telescope Science Institute, Baltimore, MD (United States); Smith, L. J. [European Space Agency/Space Telescope Science Institute, Baltimore, MD (United States); Thilker, D., E-mail: kgrasha@astro.umass.edu [Dept. of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD (United States)

    2017-05-10

    We present a study of the hierarchical clustering of the young stellar clusters in six local (3–15 Mpc) star-forming galaxies using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from the Treasury Program LEGUS (Legacy ExtraGalactic UV Survey). We identified 3685 likely clusters and associations, each visually classified by their morphology, and we use the angular two-point correlation function to study the clustering of these stellar systems. We find that the spatial distribution of the young clusters and associations are clustered with respect to each other, forming large, unbound hierarchical star-forming complexes that are in general very young. The strength of the clustering decreases with increasing age of the star clusters and stellar associations, becoming more homogeneously distributed after ∼40–60 Myr and on scales larger than a few hundred parsecs. In all galaxies, the associations exhibit a global behavior that is distinct and more strongly correlated from compact clusters. Thus, populations of clusters are more evolved than associations in terms of their spatial distribution, traveling significantly from their birth site within a few tens of Myr, whereas associations show evidence of disruption occurring very quickly after their formation. The clustering of the stellar systems resembles that of a turbulent interstellar medium that drives the star formation process, correlating the components in unbound star-forming complexes in a hierarchical manner, dispersing shortly after formation, suggestive of a single, continuous mode of star formation across all galaxies.

  3. The Hierarchical Distribution of the Young Stellar Clusters in Six Local Star-forming Galaxies

    Science.gov (United States)

    Grasha, K.; Calzetti, D.; Adamo, A.; Kim, H.; Elmegreen, B. G.; Gouliermis, D. A.; Dale, D. A.; Fumagalli, M.; Grebel, E. K.; Johnson, K. E.; Kahre, L.; Kennicutt, R. C.; Messa, M.; Pellerin, A.; Ryon, J. E.; Smith, L. J.; Shabani, F.; Thilker, D.; Ubeda, L.

    2017-05-01

    We present a study of the hierarchical clustering of the young stellar clusters in six local (3-15 Mpc) star-forming galaxies using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from the Treasury Program LEGUS (Legacy ExtraGalactic UV Survey). We identified 3685 likely clusters and associations, each visually classified by their morphology, and we use the angular two-point correlation function to study the clustering of these stellar systems. We find that the spatial distribution of the young clusters and associations are clustered with respect to each other, forming large, unbound hierarchical star-forming complexes that are in general very young. The strength of the clustering decreases with increasing age of the star clusters and stellar associations, becoming more homogeneously distributed after ˜40-60 Myr and on scales larger than a few hundred parsecs. In all galaxies, the associations exhibit a global behavior that is distinct and more strongly correlated from compact clusters. Thus, populations of clusters are more evolved than associations in terms of their spatial distribution, traveling significantly from their birth site within a few tens of Myr, whereas associations show evidence of disruption occurring very quickly after their formation. The clustering of the stellar systems resembles that of a turbulent interstellar medium that drives the star formation process, correlating the components in unbound star-forming complexes in a hierarchical manner, dispersing shortly after formation, suggestive of a single, continuous mode of star formation across all galaxies.

  4. The Hierarchical Distribution of the Young Stellar Clusters in Six Local Star-forming Galaxies

    International Nuclear Information System (INIS)

    Grasha, K.; Calzetti, D.; Adamo, A.; Messa, M.; Kim, H.; Elmegreen, B. G.; Gouliermis, D. A.; Dale, D. A.; Fumagalli, M.; Grebel, E. K.; Shabani, F.; Johnson, K. E.; Kahre, L.; Kennicutt, R. C.; Pellerin, A.; Ryon, J. E.; Ubeda, L.; Smith, L. J.; Thilker, D.

    2017-01-01

    We present a study of the hierarchical clustering of the young stellar clusters in six local (3–15 Mpc) star-forming galaxies using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from the Treasury Program LEGUS (Legacy ExtraGalactic UV Survey). We identified 3685 likely clusters and associations, each visually classified by their morphology, and we use the angular two-point correlation function to study the clustering of these stellar systems. We find that the spatial distribution of the young clusters and associations are clustered with respect to each other, forming large, unbound hierarchical star-forming complexes that are in general very young. The strength of the clustering decreases with increasing age of the star clusters and stellar associations, becoming more homogeneously distributed after ∼40–60 Myr and on scales larger than a few hundred parsecs. In all galaxies, the associations exhibit a global behavior that is distinct and more strongly correlated from compact clusters. Thus, populations of clusters are more evolved than associations in terms of their spatial distribution, traveling significantly from their birth site within a few tens of Myr, whereas associations show evidence of disruption occurring very quickly after their formation. The clustering of the stellar systems resembles that of a turbulent interstellar medium that drives the star formation process, correlating the components in unbound star-forming complexes in a hierarchical manner, dispersing shortly after formation, suggestive of a single, continuous mode of star formation across all galaxies.

  5. Identifying Broadband Rotational Spectra with Neural Networks

    Science.gov (United States)

    Zaleski, Daniel P.; Prozument, Kirill

    2017-06-01

    A typical broadband rotational spectrum may contain several thousand observable transitions, spanning many species. Identifying the individual spectra, particularly when the dynamic range reaches 1,000:1 or even 10,000:1, can be challenging. One approach is to apply automated fitting routines. In this approach, combinations of 3 transitions can be created to form a "triple", which allows fitting of the A, B, and C rotational constants in a Watson-type Hamiltonian. On a standard desktop computer, with a target molecule of interest, a typical AUTOFIT routine takes 2-12 hours depending on the spectral density. A new approach is to utilize machine learning to train a computer to recognize the patterns (frequency spacing and relative intensities) inherit in rotational spectra and to identify the individual spectra in a raw broadband rotational spectrum. Here, recurrent neural networks have been trained to identify different types of rotational spectra and classify them accordingly. Furthermore, early results in applying convolutional neural networks for spectral object recognition in broadband rotational spectra appear promising. Perez et al. "Broadband Fourier transform rotational spectroscopy for structure determination: The water heptamer." Chem. Phys. Lett., 2013, 571, 1-15. Seifert et al. "AUTOFIT, an Automated Fitting Tool for Broadband Rotational Spectra, and Applications to 1-Hexanal." J. Mol. Spectrosc., 2015, 312, 13-21. Bishop. "Neural networks for pattern recognition." Oxford university press, 1995.

  6. SPITZER SAGE INFRARED PHOTOMETRY OF MASSIVE STARS IN THE LARGE MAGELLANIC CLOUD

    International Nuclear Information System (INIS)

    Bonanos, A. Z.; Massa, D. L.; Sewilo, M.

    2009-01-01

    We present a catalog of 1750 massive stars in the Large Magellanic Cloud (LMC), with accurate spectral types compiled from the literature, and a photometric catalog for a subset of 1268 of these stars, with the goal of exploring their infrared properties. The photometric catalog consists of stars with infrared counterparts in the Spitzer SAGE survey database, for which we present uniform photometry from 0.3 to 24 μm in the UBVIJHK s +IRAC+MIPS24 bands. The resulting infrared color-magnitude diagrams illustrate that the supergiant B[e], red supergiant, and luminous blue variable (LBV) stars are among the brightest infrared point sources in the LMC, due to their intrinsic brightness, and at longer wavelengths, due to dust. We detect infrared excesses due to free-free emission among ∼900 OB stars, which correlate with luminosity class. We confirm the presence of dust around 10 supergiant B[e] stars, finding the shape of their spectral energy distributions (SEDs) to be very similar, in contrast to the variety of SED shapes among the spectrally variable LBVs. The similar luminosities of B[e] supergiants (log L/L sun ≥ 4) and the rare, dusty progenitors of the new class of optical transients (e.g., SN 2008S and NGC 300 OT), plus the fact that dust is present in both types of objects, suggests a common origin for them. We find the infrared colors for Wolf-Rayet stars to be independent of spectral type and their SEDs to be flatter than what models predict. The results of this study provide the first comprehensive roadmap for interpreting luminous, massive, resolved stellar populations in nearby galaxies at infrared wavelengths.

  7. Results of Compact Stellarator Engineering Trade Studies

    International Nuclear Information System (INIS)

    Brown, Tom; Bromberg, L.; Cole, M.

    2009-01-01

    A number of technical requirements and performance criteria can drive stellarator costs, e.g., tight tolerances, accurate coil positioning, low aspect ratio (compactness), choice of assembly strategy, metrology, and complexity of the stellarator coil geometry. With the completion of a seven-year design and construction effort of the National Compact Stellarator Experiment (NCSX) it is useful to interject the NCSX experience along with the collective experiences of the NCSX stellarator community to improving the stellarator configuration. Can improvements in maintenance be achieved by altering the stellarator magnet configuration with changes in the coil shape or with the combination of trim coils? Can a mechanical configuration be identified that incorporates a partial set of shaped fixed stellarator coils along with some removable coil set to enhance the overall machine maintenance? Are there other approaches that will simplify the concepts, improve access for maintenance, reduce overall cost and improve the reliability of a stellarator based power plant? Using ARIES-CS and NCSX as reference cases, alternative approaches have been studied and developed to show how these modifications would favorably impact the stellarator power plant and experimental projects. The current status of the alternate stellarator configurations being developed will be described and a comparison made to the recently designed and partially built NCSX device and the ARIES-CS reactor design study

  8. Results of Compact Stellarator Engineering Trade Studies

    International Nuclear Information System (INIS)

    Brown, T.; Bromberg, L.; Cole, M.

    2009-01-01

    A number of technical requirements and performance criteria can drive stellarator costs, e.g., tight tolerances, accurate coil positioning, low aspect ratio (compactness), choice of assembly strategy, metrology, and complexity of the stellarator coil geometry. With the completion of a seven-year design and construction effort of the National Compact Stellarator Experiment (NCSX) it is useful to interject the NCSX experience along with the collective experiences of the NCSX stellarator community to improving the stellarator configuration. Can improvements in maintenance be achieved by altering the stellarator magnet configuration with changes in the coil shape or with the combination of trim coils? Can a mechanical configuration be identified that incorporates a partial set of shaped fixed stellarator coils along with some removable coil set to enhance the overall machine maintenance? Are there other approaches that will simplify the concepts, improve access for maintenance, reduce overall cost and improve the reliability of a stellarator based power plant? Using ARIES-CS and NCSX as reference cases, alternative approaches have been studied and developed to show how these modifications would favorably impact the stellarator power plant and experimental projects. The current status of the alternate stellarator configurations being developed will be described and a comparison made to the recently designed and partially built NCSX device and the ARIES-CS reactor design study.

  9. Is European Broadband Ready for Smart Grid?

    DEFF Research Database (Denmark)

    Balachandran, Kartheepan; Pedersen, Jens Myrup

    2014-01-01

    In this short paper we compare the communication requirements for three Smart Grid scenarios with the availability of broadband and mobile communication networks in Europe. We show that only in the most demanding case - where data is collected and transmitted every second - a standard GSM/GPRS co....../GPRS connection is not enough. Whereas in the less demanding scenarios it is almost all of the European households that can be covered by a standard broadband technology for use with Smart Grid.......In this short paper we compare the communication requirements for three Smart Grid scenarios with the availability of broadband and mobile communication networks in Europe. We show that only in the most demanding case - where data is collected and transmitted every second - a standard GSM...

  10. Magnetically levitated autoparametric broadband vibration energy harvesting

    International Nuclear Information System (INIS)

    Kurmann, L.; Jia, Y.; Manoli, Y.; Woias, P.

    2016-01-01

    Some of the lingering challenges within the current paradigm of vibration energy harvesting (VEH) involve narrow operational frequency range and the inevitable non-resonant response from broadband noise excitations. Such VEHs are only suitable for limited applications with fixed sinusoidal vibration, and fail to capture a large spectrum of the real world vibration. Various arraying designs, frequency tuning schemes and nonlinear vibratory approaches have only yielded modest enhancements. To fundamentally address this, the paper proposes and explores the potentials in using highly nonlinear magnetic spring force to activate an autoparametric oscillator, in order to realize an inherently broadband resonant system. Analytical and numerical modelling illustrate that high spring nonlinearity derived from magnetic levitation helps to promote the 2:1 internal frequency matching required to activate parametric resonance. At the right internal parameters, the resulting system can intrinsically exhibit semi-resonant response regardless of the bandwidth of the input vibration, including broadband white noise excitation. (paper)

  11. Service Differentiation in Residential Broadband Networks

    DEFF Research Database (Denmark)

    Sigurdsson, Halldór Matthias

    2004-01-01

    As broadband gains widespread adoption with residential users, revenue generating voice- and video-services have not yet taken off. This slow uptake is often attributed to lack of Quality of Service management in residential broadband networks. To resolve this and induce service variety, network...... access providers are implementing service differentiation in their networks where voice and video gets prioritised before data. This paper discusses the role of network access providers in multipurpose packet based networks and the available migration strategies for supporting multimedia services...... in digital subscriber line (DSL) based residential broadband networks. Four possible implementation scenarios and their technical characteristics and effects are described. To conclude, the paper discusses how network access providers can be induced to open their networks for third party service providers....

  12. Policy factors affecting broadband development in Poland

    DEFF Research Database (Denmark)

    Henten, Anders; Windekilde, Iwona Maria

    2014-01-01

    of telecommunications network development in Poland than other countries in the European Union is the reason that the circumstances and also the effects of the implementation of some solutions of the EU regulation model are different in Poland than in the most developed EU countries. The aim of the paper is to examine...... and discuss broadband access development in Poland and the policy factors influencing this development as well as to examine national strategies used to stimulate service and infrastructure competition in Poland. There are, indeed, many other factors affecting broadband development such as the income level....../distribution in the country and the infrastructural point of departure. The paper, therefore, analyses the implications of the policy initiatives in light of these basic conditions and the broader context of factors influencing broadband development. In the paper, different kinds of policy initiatives are examined...

  13. Infrared photometry of upper main sequence stars in M39

    International Nuclear Information System (INIS)

    Manteiga, M.; Martinez-Roger, C.; Morales, C.; Sabau, L.

    1991-01-01

    Infrared photometry of 19 Main sequence stars in the open cluster M39 is presented. Infrared-infrared and optical-infrared colour-colour and colour-magnitude diagrams are presented and compared with mean intrinsic colours for Population I stars. An interstellar reddening of E(B - V) = 0.01 is obtained by analysis of the colour-colour diagrams. Comparison with a set of theoretical isochrones leads to an age estimate for the cluster between 2.4 and 4.8 x 10 8 years

  14. Infrared polarimetry and photometry of BL Lac objects. 3

    Energy Technology Data Exchange (ETDEWEB)

    Holmes, P A; Brand, P W.J.L. [Edinburgh Univ. (UK). Dept. of Astronomy; Impey, C D [Hawaii Univ., Honolulu (USA). Inst. for Astronomy; Williams, P M [UKIRT, Hilo, HI (USA)

    1984-10-15

    The data presented here is part of a continuing monitoring programme of BL lac objects with J, H and K photometry and polarimetry. A total of 30 BL Lac objects have now been observed photometrically. Infrared polarimetry has also been obtained for 24 of these objects. The sample is sufficiently large to examine statistically, and several important correlations have emerged. Internight variations and wavelength dependence of polarization indicate that BL Lac objects, as a class, may be understood in terms of a relatively simple two-component model.

  15. uvby photometry in McCormick proper motion fields

    Science.gov (United States)

    Degewij, J.

    1982-01-01

    The Danish 50 cm telescope at the European Southern Observatory was used to obtain high-precision uvby photometry for 50 F2 to G2 stars, with V values in the 9.4-12.3 mag range, which were selected in the southern galactic polar regions of the McCormick proper motion fields and measured on six different nights. The brighter stars are found to systematically exhibit smaller m(1) indices, of about 0.02 mag, upon comparison with the earlier data of Blaauw et al (1976). Single measurements are given for 98 stars in eight McCormick fields at intermediate southern galactic latitudes.

  16. Near infrared photometry of violent star formation regions

    International Nuclear Information System (INIS)

    Melnick, J.; Terlevich, R.; Moles, M.

    1985-01-01

    Near infrared broad band photometry and CO indices for a significant number of Violent Star Formation Regions are presented. The existence of a narrow correlation between W (Hβ) and IR colour is confirmed. The interpretation of this relation as an age sequence implies a correlation between CO index and W(Hβ) which is not found. It is argued however that this failure is most likely a consequence of using narrow band filters to determine CO indices in objects with strong emission-line spectra. (author)

  17. Infrared photometry of upper main sequence stars in M39

    Energy Technology Data Exchange (ETDEWEB)

    Manteiga, M.; Martinez-Roger, C. (Instituto de Astrofisica de Canarias, Tenerife, (ES)); Morales, C.; Sabau, L. (Instituto de Tecnica Aeroespacial, Madrid, (ES))

    1991-03-01

    Infrared photometry of 19 Main sequence stars in the open cluster M39 is presented. Infrared-infrared and optical-infrared colour-colour and colour-magnitude diagrams are presented and compared with mean intrinsic colours for Population I stars. An interstellar reddening of E(B - V) = 0.01 is obtained by analysis of the colour-colour diagrams. Comparison with a set of theoretical isochrones leads to an age estimate for the cluster between 2.4 and 4.8 x 10{sup 8} years.

  18. OV Bootis: Forty Nights of World-Wide Photometry (Abstract)

    Science.gov (United States)

    Patterson, J.; de Miguel, E.; Barret, D.; Brincat, S.; Boardman, J., Jr.; Buczynski, D.; Campbell, T.; Cejudo, D.; Cook, L.; Cook, M. J.; Collins, D.; Cooney, W.; Dubois, F.; Dvorak, S.; Halpern, J. P.; Kroes, A. J.; Lemay, D.; Licchelli, D.; Mankel, D.; Marshall, M.; Novak, R.; Oksanen, A.; Roberts, G.; Seargeant, J.; Sears, H.; Silcox, A.; Slauson, D.; Stone, G.; Thorstensen, J. R.; Ulowetz, J.; Vanmunster, T.; Wallgren, J.; Wood, M.

    2017-12-01

    (Abstract only) Among the 1000 known cataclysmic variables, only one appears to belong to the "Galactic halo"-the Population II stars. We report round-the-world photometry of this star (OV Boo) during March-April 2017, when it staged its first certified dwarf-nova outburst. The star is remarkable for its short binary period (66 minutes), high proper motion, metal-poor composition, substellar secondary, sharp white-dwarf eclipses, and nonradial pulsations. Something for everybody - and it even had the good manners to erupt in northern springtime, when it transits near local midnight. Move over, SS Cyg and WZ Sge; there's a new celebrity in town!

  19. The Photometry Pipeline of the Watcher Robotic Telescope

    Directory of Open Access Journals (Sweden)

    A. Ferrero

    2010-01-01

    Full Text Available The Watcher robotic telescope was developed primarily to perform rapid optical follow-up observations of Gamma-Ray Bursts (GRBs. Secondary scientific goals include blazar monitoring and variable star studies. An automated photometry pipeline to rapidly analyse data from Watcher has been implemented. Details of the procedures to get image zero-point, source instrumental measurement, and limiting magnitude are presented. Sources of uncertainty are assessed and the performance of the pipeline is tested by comparison with a number of catalogue sources.

  20. Cepheid distance scale: a new application for infrared photometry

    International Nuclear Information System (INIS)

    McGonegal, R.; McLaren, R.A.; McAlary, C.W.; Madore, B.F.

    1982-01-01

    It is shown that near-infrared photometry of Cepheid variables provides a powerful and practical means of calibrating the distance scale to nearby galaxies. Compared with similar work in the blue, random-phase observations in the near-infrared produce a factor of 2.5 decrease in the apparent width of the period-luminosity relation. This we attribute to a substantially decreased effect of differential reddening at long wavelengths, to the low sensitivity of the infrared flux to metallicity variations, and furthermore to the fact that the cyclical luminosity variations are also greatly reduced in the infrared

  1. The COSMOS2015 galaxy stellar mass function . Thirteen billion years of stellar mass assembly in ten snapshots

    Science.gov (United States)

    Davidzon, I.; Ilbert, O.; Laigle, C.; Coupon, J.; McCracken, H. J.; Delvecchio, I.; Masters, D.; Capak, P.; Hsieh, B. C.; Le Fèvre, O.; Tresse, L.; Bethermin, M.; Chang, Y.-Y.; Faisst, A. L.; Le Floc'h, E.; Steinhardt, C.; Toft, S.; Aussel, H.; Dubois, C.; Hasinger, G.; Salvato, M.; Sanders, D. B.; Scoville, N.; Silverman, J. D.

    2017-09-01

    We measure the stellar mass function (SMF) and stellar mass density of galaxies in the COSMOS field up to z 6. We select them in the near-IR bands of the COSMOS2015 catalogue, which includes ultra-deep photometry from UltraVISTA-DR2, SPLASH, and Subaru/Hyper Suprime-Cam. At z> 2.5 we use new precise photometric redshifts with error σz = 0.03(1 + z) and an outlier fraction of 12%, estimated by means of the unique spectroscopic sample of COSMOS ( 100 000 spectroscopic measurements in total, more than one thousand having robust zspec> 2.5). The increased exposure time in the DR2, along with our panchromatic detection strategy, allow us to improve the completeness at high z with respect to previous UltraVISTA catalogues (e.g. our sample is >75% complete at 1010 ℳ⊙ and z = 5). We also identify passive galaxies through a robust colour-colour selection, extending their SMF estimate up to z = 4. Our work provides a comprehensive view of galaxy-stellar-mass assembly between z = 0.1 and 6, for the first time using consistent estimates across the entire redshift range. We fit these measurements with a Schechter function, correcting for Eddington bias. We compare the SMF fit with the halo mass function predicted from ΛCDM simulations, finding that at z> 3 both functions decline with a similar slope in thehigh-mass end. This feature could be explained assuming that mechanisms quenching star formation in massive haloes become less effective at high redshifts; however further work needs to be done to confirm this scenario. Concerning the SMF low-mass end, it shows a progressive steepening as it moves towards higher redshifts, with α decreasing from -1.47+0.02-0.02 at z ≃ 0.1 to -2.11+0.30-0.13 at z ≃ 5. This slope depends on the characterisation of the observational uncertainties, which is crucial to properly remove the Eddington bias. We show that there is currently no consensus on the method to quantify such errors: different error models result in different best

  2. Participation in the broadband society in Denmark

    DEFF Research Database (Denmark)

    Falch, Morten; Henten, Anders; Skouby, Knud Erik

    2009-01-01

    passed the threshold set by the EU with respect to the relevance of initiating a discussion on the implementation of a universal service obligation on broadband. As documented in the paper, there are groups among primarily the elderly and the unemployed who do not have Internet access. Their own......The purpose of the paper is to provide an empirical overview of broadband developments in Denmark. The overview includes sections on coverage and penetration, connection speeds, retail prices, competition, interconnection prices, and residential access to Internet. The documentation shows...

  3. Deep SOAR follow-up photometry of two Milky Way outer-halo companions discovered with Dark Energy Survey

    Science.gov (United States)

    Luque, E.; Santiago, B.; Pieres, A.; Marshall, J. L.; Pace, A. B.; Kron, R.; Drlica-Wagner, A.; Queiroz, A.; Balbinot, E.; Ponte, M. dal; Neto, A. Fausti; da Costa, L. N.; Maia, M. A. G.; Walker, A. R.; Abdalla, F. B.; Allam, S.; Annis, J.; Bechtol, K.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Crocce, M.; Davis, C.; Doel, P.; Eifler, T. F.; Flaugher, B.; García-Bellido, J.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Miquel, R.; Nichol, R. C.; Plazas, A. A.; Sanchez, E.; Scarpine, V.; Schindler, R.; Sevilla-Noarbe, I.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Tarle, G.; Thomas, D.

    2018-04-01

    We report the discovery of a new star cluster, DES 3, in the constellation of Indus, and deeper observations of the previously identified satellite DES J0222.7-5217 (Eridanus III). DES 3 was detected as a stellar overdensity in first-year Dark Energy Survey data, and confirmed with deeper photometry from the 4.1 metre Southern Astrophysical Research (SOAR) telescope. The new system was detected with a relatively high significance and appears in the DES images as a compact concentration of faint blue point sources. We determine that DES 3 is located at a heliocentric distance of ≃ 76.2 kpc and it is dominated by an old (≃ 9.8 Gyr) and metal-poor ([Fe/H] ≃ -1.84) population. While the age and metallicity values of DES 3 are comparable to typical globular clusters (objects with a high stellar density, stellar mass of ˜105M⊙ and luminosity MV ˜ -7.3), its half-light radius (rh ˜ 6.87 pc) and luminosity (MV ˜ -1.7) are more indicative of faint star cluster. Based on the angular size, DES 3, with a value of rh ˜ 0{^'.}31, is among the smallest faint star clusters known to date. Furthermore, using deeper imaging of DES J0222.7-5217 taken with the SOAR telescope, we update structural parameters and perform the first isochrone modeling. Our analysis yields the first age (≃ 12.6 Gyr) and metallicity ([Fe/H] ≃ -2.01) estimates for this object. The half-light radius (rh ≃ 11.24 pc) and luminosity (MV ≃ -2.4) of DES J0222.7-5217 suggest that it is likely a faint star cluster. The discovery of DES 3 indicates that the census of stellar systems in the Milky Way is still far from complete, and demonstrates the power of modern wide-field imaging surveys to improve our knowledge of the Galaxy's satellite population.

  4. Stellarator fusion neutronics research in Australia

    International Nuclear Information System (INIS)

    Zimin, S.; Cross, R.C.

    1997-01-01

    The new status of the H-INF Heliac Stellaralor as a National Facility and the signed international Implementing Agreement on 'Collaboration in the Development of the Stellarator Concept' represents a significant encouragement for further fusion research in Australia. In this report the future of fusion research in Australia is discussed with special attention being paid to the importance of Stellarator power plant studies and in particular stellarator fusion neutronics. The main differences between tokamak and stellarator neutronics analyses are identified, namely the neutron wall loading, geometrical modelling and total heating in in-vessel reactor components including toroidal field (TF) coils. Due to the more complicated nature of stellarator neutronics analyses, simplified approaches to fusion neutronics already developed for tokamaks are expected to be even more important and widely used for designing a Conceptual Stellarator Power Plant

  5. On the universal stellar law

    Science.gov (United States)

    Krot, Alexander

    In this work, we consider a statistical theory of gravitating spheroidal bodies to derive and develop the universal stellar law for extrasolar systems. Previously, the statistical theory for a cosmogonic body forming (so-called spheroidal body)has been proposed [1-3]. This theory starts from the conception for forming a spheroidal body inside a gas-dust protoplanetary nebula; it permits us to derive the form of distribution functions, mass density, gravitational potentials and strengths both for immovable and rotating spheroidal bodies as well as to find the distribution function of specific angular momentum[1-3]. If we start from the conception for forming a spheroidal body as a protostar (in particular, proto-Sun) inside a prestellar (presolar) nebula then the derived distribution functions of particle (as well as the mass density of an immovable spheroidal body) characterizes the first stage of evolution: from a prestellar molecular cloud (the presolar nebula) to the forming core of protostar (the proto-Sun) together with its shell as a stellar nebula (the solar nebula). This work derives the equation of state of an ideal stellar substance based on conception of gravitating spheroidal body. Using this equation, we obtain the universal stellar law (USL) for the planetary systems connecting temperature, size and mass of each of stars. This work also considers the Solar corona in the connection with USL. Then it is accounting under calculation of the ratio of temperature of the Solar corona to effective temperature of the Sun’ surfaceand modification of USL. To test justice of the modified USLfor different types of stars, the temperature of stellar corona is estimated. The prediction of parameters of stars is carrying out by means of the modified USL,as well as the Hertzsprung-Russell’s dependence [5-7]is derivedby means of USL directly. This paper also shows that knowledge of some characteristics for multi-planet extrasolar systems refines own parameters of

  6. VT Wireline Broadband Availability by Census Block - 06-2013

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201306 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2013. This...

  7. VT Public Locations of Broadband Data - 06-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201006 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2010. This...

  8. VT Public Locations of Broadband Data - 12-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201112 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2011. This...

  9. VT Public Locations of Broadband Data - 06-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201106 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2011. This...

  10. VT Cable Broadband Availability by Census Block - 06-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201006 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2010. This...

  11. VT Total Broadband Availability by Census Block - 12-2012

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201212 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2012. This...

  12. VT Cable Broadband Availability by Census Block - 12-2012

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201212 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2012. This...

  13. VT Detailed Broadband Availability by Census Block -12-2012

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201212 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2012. This...

  14. VT Detailed Broadband Availability by Census Block - 06-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201006 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2010. This...

  15. VT Detailed Broadband Availability by Census Block -12-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201112 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2011. This...

  16. VT Detailed Broadband Availability by Census Block - 06-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201106 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2011. This...

  17. VT Wireline Broadband Availability by Census Block - 12-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201012 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2010. This...

  18. VT Wireless Broadband Availability by Census Block - 06-2013

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201306 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2013. This...

  19. VT Total Broadband Availability by Census Block - 06-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201006 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2010. This...

  20. VT Wireline Broadband Availability by Census Block - 06-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201006 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2010. This...

  1. VT Wireless Broadband Availability by Census Block - 12-2012

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201212 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2012. This...

  2. VT Total Broadband Availability by Census Block - 12-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201112 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2011. This...

  3. VT Cable Broadband Availability by Census Block - 12-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201012 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2010. This...

  4. VT Wireless Broadband Availability by Census Block - 06-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201006 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2010. This...

  5. VT Detailed Broadband Availability by Census Block - 12-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201012 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2010. This...

  6. VT Total Broadband Availability by Census Block - 06-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201106 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2011. This...

  7. VT DSL Broadband Availability by Census Block - 06-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201106 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2011. This...

  8. VT Wireline Broadband Availability by Census Block - 12-2012

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201212 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2012. This...

  9. VT DSL Broadband Availability by Census Block - 06-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201006 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2010. This...

  10. VT Wireless Broadband Availability by Census Block - 06-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201106 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2011. This...

  11. 7 CFR 1738.11 - Availability of broadband service.

    Science.gov (United States)

    2010-01-01

    ..., DEPARTMENT OF AGRICULTURE RURAL BROADBAND ACCESS LOANS AND LOAN GUARANTEES Loan Purposes and Basic Policies... given to loans to finance service to eligible rural communities in which broadband service is not...

  12. VT Wireless Broadband Availability by Census Block - 12-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201012 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2010. This...

  13. VT Public Locations of Broadband Data - 12-2012

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201212 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2012. This...

  14. VT DSL Broadband Availability by Census Block - 06-2013

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201306 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2013. This...

  15. VT Cable Broadband Availability by Census Block - 06-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201106 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2011. This...

  16. VT Wireline Broadband Availability by Census Block - 12-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201112 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2011. This...

  17. VT Cable Broadband Availability by Census Block - 06-2013

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201306 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2013. This...

  18. VT Wireless Broadband Availability by Census Block - 12-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201112 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2011. This...

  19. VT DSL Broadband Availability by Census Block - 12-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201112 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2011. This...

  20. VT Wireline Broadband Availability by Census Block - 06-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201106 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2011. This...

  1. VT Public Locations of Broadband Data - 12-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201012 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2010. This...

  2. VT Cable Broadband Availability by Census Block - 12-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201112 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2011. This...

  3. VT Total Broadband Availability by Census Block - 12-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201012 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2010. This...

  4. VT Detailed Broadband Availability by Census Block - 06-2013

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201306 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2013. This...

  5. VT DSL Broadband Availability by Census Block - 12-2012

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201212 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2012. This...

  6. VT DSL Broadband Availability by Census Block - 12-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201012 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2010. This...

  7. VT Public Locations of Broadband Data - 06-2013

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201306 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2013. This...

  8. Semiconductor Quantum Dash Broadband Emitters: Modeling and Experiments

    KAUST Repository

    Khan, Mohammed Zahed Mustafa

    2013-01-01

    multi-disciplinary field applications such as biomedical imaging and sensing, general lighting and internet and mobile phone connectivity. In general, most commercial broadband light sources relies on complex systems for broadband light generation which

  9. VT Total Broadband Availability by Census Block - 06-2013

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201306 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2013. This...

  10. Multi-band photometry of trans-Neptunian objects in the Subaru Hyper Suprime-Cam survey

    Science.gov (United States)

    Terai, Tsuyoshi; Yoshida, Fumi; Ohtsuki, Keiji; Lykawka, Patryk Sofia; Takato, Naruhisa; Higuchi, Arika; Ito, Takashi; Komiyama, Yutaka; Miyazaki, Satoshi; Wang, Shiang-Yu

    2018-01-01

    We present visible multi-band photometry of trans-Neptunian objects (TNOs) observed by the Subaru Telescope in the framework of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) from 2014 March to 2016 September. We measured the five broad-band (g, r, i, z, and Y) colors over the wavelength range from 0.4 μm to 1.0 μm for 30 known TNOs using the HSC-SSP survey data covering ˜500 deg2 of sky within ±30° of ecliptic latitude. This dataset allows us to investigate the correlations between the dynamical classes and visible reflectance spectra of TNOs. Our results show that the hot classical and scattered populations with orbital inclination (I) of I ≳ 6° share similar color distributions, while the cold classical population with I ≲ 6° has a different color distribution from the others. The low-I population has reflectance increasing toward longer wavelengths up to ˜0.8 μm, with a steeper slope than the high-I population at ≲ 0.6 μm. We also find a significant anti-correlation between g - r/r - i colors and inclination in the high-I population, as well as a possible bimodality in the g - i color vs. eccentricity plot.

  11. Multiplicity in Early Stellar Evolution

    Science.gov (United States)

    Reipurth, B.; Clarke, C. J.; Boss, A. P.; Goodwin, S. P.; Rodríguez, L. F.; Stassun, K. G.; Tokovinin, A.; Zinnecker, H.

    Observations from optical to centimeter wavelengths have demonstrated that multiple systems of two or more bodies is the norm at all stellar evolutionary stages. Multiple systems are widely agreed to result from the collapse and fragmentation of cloud cores, despite the inhibiting influence of magnetic fields. Surveys of class 0 protostars with millimeter interferometers have revealed a very high multiplicity frequency of about 2/3, even though there are observational difficulties in resolving close protobinaries, thus supporting the possibility that all stars could be born in multiple systems. Near-infrared adaptive optics observations of class I protostars show a lower binary frequency relative to the class 0 phase, a declining trend that continues through the class II/III stages to the field population. This loss of companions is a natural consequence of dynamical interplay in small multiple systems, leading to ejection of members. We discuss observational consequences of this dynamical evolution, and its influence on circumstellar disks, and we review the evolution of circumbinary disks and their role in defining binary mass ratios. Special attention is paid to eclipsing PMS binaries, which allow for observational tests of evolutionary models of early stellar evolution. Many stars are born in clusters and small groups, and we discuss how interactions in dense stellar environments can significantly alter the distribution of binary separations through dissolution of wider binaries. The binaries and multiples we find in the field are the survivors of these internal and external destructive processes, and we provide a detailed overview of the multiplicity statistics of the field, which form a boundary condition for all models of binary evolution. Finally, we discuss various formation mechanisms for massive binaries, and the properties of massive trapezia.

  12. Physics of Compact Advanced Stellarators

    International Nuclear Information System (INIS)

    Zarnstorff, M.C.; Berry, L.A.; Brooks, A.; Fredrickson, E.; Fu, G.-Y.; Hirshman, S.; Hudson, S.; Ku, L.-P.; Lazarus, E.; Mikkelsen, D.; Monticello, D.; Neilson, G.H.; Pomphrey, N.; Reiman, A.; Spong, D.; Strickler, D.; Boozer, A.; Cooper, W.A.; Goldston, R.; Hatcher, R.; Isaev, M.; Kessel, C.; Lewandowski, J.; Lyon, J.; Merkel, P.; Mynick, H.; Nelson, B.E.; Nuehrenberg, C.; Redi, M.; Reiersen, W.; Rutherford, P.; Sanchez, R.; Schmidt, J.; White, R.B.

    2001-01-01

    Compact optimized stellarators offer novel solutions for confining high-beta plasmas and developing magnetic confinement fusion. The 3-D plasma shape can be designed to enhance the MHD stability without feedback or nearby conducting structures and provide drift-orbit confinement similar to tokamaks. These configurations offer the possibility of combining the steady-state low-recirculating power, external control, and disruption resilience of previous stellarators with the low-aspect ratio, high beta-limit, and good confinement of advanced tokamaks. Quasi-axisymmetric equilibria have been developed for the proposed National Compact Stellarator Experiment (NCSX) with average aspect ratio 4-4.4 and average elongation of approximately 1.8. Even with bootstrap-current consistent profiles, they are passively stable to the ballooning, kink, vertical, Mercier, and neoclassical-tearing modes for beta > 4%, without the need for external feedback or conducting walls. The bootstrap current generates only 1/4 of the magnetic rotational transform at beta = 4% (the rest is from the coils), thus the equilibrium is much less nonlinear and is more controllable than similar advanced tokamaks. The enhanced stability is a result of ''reversed'' global shear, the spatial distribution of local shear, and the large fraction of externally generated transform. Transport simulations show adequate fast-ion confinement and thermal neoclassical transport similar to equivalent tokamaks. Modular coils have been designed which reproduce the physics properties, provide good flux surfaces, and allow flexible variation of the plasma shape to control the predicted MHD stability and transport properties

  13. STELLAR MASS DEPENDENT DISK DISPERSAL

    International Nuclear Information System (INIS)

    Kennedy, Grant M.; Kenyon, Scott J.

    2009-01-01

    We use published optical spectral and infrared (IR) excess data from nine young clusters and associations to study the stellar mass dependent dispersal of circumstellar disks. All clusters older than ∼3 Myr show a decrease in disk fraction with increasing stellar mass for solar to higher mass stars. This result is significant at about the 1σ level in each cluster. For the complete set of clusters we reject the null hypothesis-that solar and intermediate-mass stars lose their disks at the same rate-with 95%-99.9% confidence. To interpret this behavior, we investigate the impact of grain growth, binary companions, and photoevaporation on the evolution of disk signatures. Changes in grain growth timescales at fixed disk temperature may explain why early-type stars with IR excesses appear to evolve faster than their later-type counterparts. Little evidence that binary companions affect disk evolution suggests that photoevaporation is the more likely mechanism for disk dispersal. A simple photoevaporation model provides a good fit to the observed disk fractions for solar and intermediate-mass stars. Although the current mass-dependent disk dispersal signal is not strong, larger and more complete samples of clusters with ages of 3-5 Myr can improve the significance and provide better tests of theoretical models. In addition, the orbits of extra-solar planets can constrain models of disk dispersal and migration. We suggest that the signature of stellar mass dependent disk dispersal due to photoevaporation may be present in the orbits of observed extra-solar planets. Planets orbiting hosts more massive than ∼1.6 M sun may have larger orbits because the disks in which they formed were dispersed before they could migrate.

  14. Radiation transfer and stellar atmospheres

    Science.gov (United States)

    Swihart, T. L.

    This is a revised and expanded version of the author's Basic Physics of Stellar Atmospheres, published in 1971. The equation of transfer is considered, taking into account the intensity and derived quantities, the absorption coefficient, the emission coefficient, the source function, and special integrals for plane media. The gray atmosphere is discussed along with the nongray atmosphere, and aspects of line formation. Topics related to polarization are explored, giving attention to pure polarized radiation, general polarized radiation, transfer in a magnetic plasma, and Rayleigh scattering and the sunlit sky. Physical and astronomical constants, and a number of problems related to the subjects of the book are presented in an appendix.

  15. Drift waves in a stellarator

    International Nuclear Information System (INIS)

    Bhattacharjee, A.; Sedlak, J.E.; Similon, P.L.; Rosenbluth, M.N.; Ross, D.W.

    1982-11-01

    We investigate the eigenmode structure of drift waves in a straight stellarator using the ballooning mode formalism. The electrons are assumed to be adiabatic and the ions constitute a cold, magnetized fluid. The effective potential has an overall parabolic envelope but is modulated strongly by helical ripples along B. We have found two classes of solutions: those that are strongly localized in local helical wells, and those that are weakly localized and have broad spatial extent. The weakly localized modes decay spatially due to the existence of Mathieu resonances between the periods of the eigenfunction and the effective potential

  16. Helical axis stellarator equilibrium model

    International Nuclear Information System (INIS)

    Koniges, A.E.; Johnson, J.L.

    1985-02-01

    An asymptotic model is developed to study MHD equilibria in toroidal systems with a helical magnetic axis. Using a characteristic coordinate system based on the vacuum field lines, the equilibrium problem is reduced to a two-dimensional generalized partial differential equation of the Grad-Shafranov type. A stellarator-expansion free-boundary equilibrium code is modified to solve the helical-axis equations. The expansion model is used to predict the equilibrium properties of Asperators NP-3 and NP-4. Numerically determined flux surfaces, magnetic well, transform, and shear are presented. The equilibria show a toroidal Shafranov shift

  17. Neutrino transport in stellar matter

    International Nuclear Information System (INIS)

    Basdevant, J.L.

    1985-09-01

    We reconsider the neutrino transport problem in dense stellar matter which has a variety of applications among which the participation of neutrinos to the dynamics of type II supernova explosions. We describe the position of the problem and make some critiscism of previously used approximation methods. We then propose a method which is capable of handling simultaneously the optically thick, optically thin, and intermediate regimes, which is of crucial importance in such problems. The method consists in a simulation of the transport process and can be considered exact within numerical accuracy. We, finally exhibit some sample calculations which show the efficiency of the method, and present interesting qualitative physical features

  18. Characterizing Convection in Stellar Atmospheres

    International Nuclear Information System (INIS)

    Tanner, Joel; Basu, Sarbani; Demarque, Pierre; Robinson, Frank

    2011-01-01

    We perform 3D radiative hydrodynamic simulations to study the properties of convection in the superadiabatic layer of stars. The simulations show differences in both the stratification and turbulent quantities for different types of stars. We extract turbulent pressure and eddy sizes, as well as the T-τ relation for different stars and find that they are sensitive to the energy flux and gravity. We also show that contrary to what is usually assumed in the field of stellar atmospheres, the structure and gas dynamics of simulations of turbulent atmospheres cannot be parameterized with T eff and log(g) alone.

  19. On modular stellarator reactor coils

    International Nuclear Information System (INIS)

    Rau, F.; Harmeyer, E.; Kisslinger, J.; Wobig, H.

    1985-01-01

    Modular twisted coils are discussed which produce magnetic fields of the Advanced Stellarator WENDELSTEIN VII-AS type. Reducing the number coils/FP offers advantage for maintenance of coils, but increases the magnetic ripple and B m /B o . Computation of force densities within the coils of ASR and ASB yield local maximum values of about 80 and 180 MN/m 3 , respectively. A system of mutual coil support is being developed. Twisted coils in helical arrangement provide a reactor-sized HELIAC system. In order to reduce the magnetic ripple, a large number of 14 coils/FP in special arrangement is used

  20. Stellar orbits around Sgr A*

    International Nuclear Information System (INIS)

    Trippe, S; Gillessen, S; Ott, T; Eisenhauer, F; Paumard, T; Martins, F; Genzel, R; Schoedel, R; Eckart, A; Alexander, T

    2006-01-01

    In this article we present and discuss the latest results from the observations of stars (''S-stars'') orbiting Sgr A* . With improving data quality the number of observed S-stars has increased substantially in the last years. The combination of radial velocity and proper motion information allows an ever more precise determination of orbital parameters and of the mass of and the distance to the supermassive black hole in the centre of the Milky Way. Additionally, the orbital solutions allow us to verify an agreement between the NIR source Sgr A* and the dynamical centre of the stellar orbits to within 2 mas

  1. Recent advances in stellarator optimization

    Science.gov (United States)

    Gates, D. A.; Boozer, A. H.; Brown, T.; Breslau, J.; Curreli, D.; Landreman, M.; Lazerson, S. A.; Lore, J.; Mynick, H.; Neilson, G. H.; Pomphrey, N.; Xanthopoulos, P.; Zolfaghari, A.

    2017-12-01

    Computational optimization has revolutionized the field of stellarator design. To date, optimizations have focused primarily on optimization of neoclassical confinement and ideal MHD stability, although limited optimization of other parameters has also been performed. The purpose of this paper is to outline a select set of new concepts for stellarator optimization that, when taken as a group, present a significant step forward in the stellarator concept. One of the criticisms that has been leveled at existing methods of design is the complexity of the resultant field coils. Recently, a new coil optimization code—COILOPT++, which uses a spline instead of a Fourier representation of the coils,—was written and included in the STELLOPT suite of codes. The advantage of this method is that it allows the addition of real space constraints on the locations of the coils. The code has been tested by generating coil designs for optimized quasi-axisymmetric stellarator plasma configurations of different aspect ratios. As an initial exercise, a constraint that the windings be vertical was placed on large major radius half of the non-planar coils. Further constraints were also imposed that guaranteed that sector blanket modules could be removed from between the coils, enabling a sector maintenance scheme. Results of this exercise will be presented. New ideas on methods for the optimization of turbulent transport have garnered much attention since these methods have led to design concepts that are calculated to have reduced turbulent heat loss. We have explored possibilities for generating an experimental database to test whether the reduction in transport that is predicted is consistent with experimental observations. To this end, a series of equilibria that can be made in the now latent QUASAR experiment have been identified that will test the predicted transport scalings. Fast particle confinement studies aimed at developing a generalized optimization algorithm are also

  2. Improving the Photometry of the Pi of the Sky System

    Directory of Open Access Journals (Sweden)

    A. F. Żarnecki

    2011-01-01

    Full Text Available The “Pi of the Sky” robotic telescope was designed to monitor a significant fraction of the sky with good time resolution and range. The main goal of the “Pi of the Sky” detector is to look for short timescale optical transients arising from various astrophysical phenomena, mainly for the optical counterparts of Gamma Ray Bursts (GRB. The system design, the observation methodology and the algorithms that have been developed make this detector a sophisticated instrument for looking for novae and supernovae stars and for monitoring blasars and AGNs activity. The final detector will consist of two sets of 12 cameras, one camera covering a field of view of 20◦ ×20◦. For data taken with the prototype detector at the Las Campanas Observatory, Chile, photometry uncertainty of 0.018–0.024 magnitudo for stars 7–10m was obtained. With a new calibration algorithm taking into account the spectral type of reference stars, the stability of the photometry algorithm can be significantly improved. Preliminary results from the BGInd variable are presented, showing that uncertainty of the order of 0.013 can be obtained.

  3. BVI CCD photometry of the globular cluster M4

    International Nuclear Information System (INIS)

    Alcaino, G.; Liller, W.; Alvarado, F.

    1988-01-01

    CCD BV1 main-sequence (MS) photometry of M4, the globular cluster closest to the sun, is presented. The photometry is matched to the BVI isochrones of VandenBerg and Bell (1985). The MS turnoffs are found to be at V = 16.90 + or - 0.05, B-V = 0.81 + or - 0.02, V-I = 0.96 + or - 0.02, and B - I = 1.77 + or - 0.02. The magnitude difference between the MS turnoff and the horizontal branch is Delta M(V) = 3.52 + or - 0.1 for all three color indices. Using Y = 0.2, (Fe/H) = - 1.27, and alpha = 1.65, with a distance modulus of (m-M)V = 12.7 and E(B-V) = 0.41, a consistent age for M4 is deduced in all three color indices of 17 + or - 1.5 Gyr. 34 references

  4. Progress in photometry. Sokko ni okeru saikinno shinpo

    Energy Technology Data Exchange (ETDEWEB)

    Krochmann, J

    1991-07-01

    A recent progress in photometry was summarized. As to photometric error, photometric head, luminous intensity, luminous flux, and lighting system, a present situation was introduced. Was described the error in photometry using a silicon photodiode, which became in a level of 0.1% by the self-calibration. Also were illustrated the photometric heads for evaluating spatial luminous intensities, the detector for ratio temperature measurement needed for calibration of a normal standard light source, the filter-type monochromator for measuring a difference of spectral response, and the solar battery for reference which can correct the photometer used for the long period in the field. A measurement of high-speed photocurrent was shown, in which the resolving power of 10{sup {minus}14}ampere (10{sup {minus}6}lux) can be achieved. A goniophotometer for luminous flux measurement was also introduced. Furthermore, the stimulation direct-reading colorimeter, the reflectance and transmission measuring apparatus, the illumination meter with a remote control transmitter, the diffuse reflectance measuring apparatus, and the daylight factor measuring apparatus were illustrated. 14 refs., 11 figs.

  5. Stromvil Photometry of Clusters II. The Open Cluster M67

    Science.gov (United States)

    Boyle, R. P.; Philip, A. G. D.; Straižys, V.

    1998-12-01

    Use of the Stromgren four-color photometric system with the addition of three filters (P, Z, S) of the Vilnius system allows classifying all the types of stars, even in the presence of significant reddening by interstellar dust (Strai\\v{z}ys et al, 1996). With this Stromvil system we have begun a long-term observational program on the Vatican Advanced Technology Telescope (VATT) on Mt. Graham, Arizona, (see Philip et al,1996). The Loral 2K by 2K CCD, prepared by M. Lesser of the University of Arizona CCD Lab, gives as high as 90% quantum efficiency in most of the filters and notably 65% at the u filter. To demonstrate the degree of success so far attained in this CCD Stromvil System, we present preliminary results on the open cluster M67. We will compare some of our photometry with the CCD results of B. A. Twarog (1987) and the photoelectric photometry of Nissen et al. (1987). REFERENCES Nissen, P.E., Twarog, B.A., and Crawford, D.L. 1987, A.J. 93,634 Philip, A.G. Davis, Boyle, R.P., Strai\\v{z}ys, V. 1996, Baltic Astronomy,5,445 Strai\\v{z}ys, V., Crawford, D.L., Philip, A.G.Davis 1996, Baltic Astronomy, 5,83 Twarog, B.A. 1987, A.J. 93,647

  6. Introduction to stellar astrophysics. V. 1

    International Nuclear Information System (INIS)

    Boehm-Vitense, E.

    1989-01-01

    This textbook introduces basic elements of fundamental astronomy and astrophysics which serve as a foundation for understanding the structure, evolution, and observed properties of stars. The first half of the book explains how stellar motions, distances, luminosities, colours, radii, masses and temperatures are measured or derived. The author then shows how data of these sorts can be arranged to classify stars through their spectra. Stellar rotation and stellar magnetic fields are introduced. Stars with peculiar spectra and pulsating stars also merit special attention. The endpoints of stellar evolutions are briefly described. There is a separate chapter on the Sun and a final one on interstellar absorption. (author)

  7. VERIFYING ASTEROSEISMICALLY DETERMINED PARAMETERS OF KEPLER STARS USING HIPPARCOS PARALLAXES: SELF-CONSISTENT STELLAR PROPERTIES AND DISTANCES

    Energy Technology Data Exchange (ETDEWEB)

    Silva Aguirre, V.; Chaplin, W. J.; Bedding, T. R.; Christensen-Dalsgaard, J.; Kjeldsen, H. [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Casagrande, L. [Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, The Australian National University, ACT 2611 (Australia); Basu, S. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States); Campante, T. L.; Monteiro, M. J. P. F. G. [Centro de Astrofisica and Faculdade de Ciencias, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Huber, D. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Miglio, A.; Elsworth, Y.; Hekker, S. [School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT (United Kingdom); Serenelli, A. M.; Garcia, R. A.; Mathur, S. [Kavli Institute for Theoretical Physics, Santa Barbara, CA 93106 (United States); Ballot, J. [CNRS, Institut de Recherche en Astrophysique et Planetologie, 14 avenue Edouard Belin, F-31400 Toulouse (France); Creevey, O. L. [Laboratoire Lagrange, UMR 7293, Universite de Nice Sophia-Antipolis, CNRS, Observatoire de la Cote dAzur, F-06304 Nice Cedex 4 (France); Gilliland, R. L. [Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, University Park, PA (United States); Metcalfe, T. S. [Space Science Institute, Boulder, CO 80301 (United States); and others

    2012-09-20

    Accurately determining the properties of stars is of prime importance for characterizing stellar populations in our Galaxy. The field of asteroseismology has been thought to be particularly successful in such an endeavor for stars in different evolutionary stages. However, to fully exploit its potential, robust methods for estimating stellar parameters are required and independent verification of the results is mandatory. With this purpose, we present a new technique to obtain stellar properties by coupling asteroseismic analysis with the InfraRed Flux Method. By using two global seismic observables and multi-band photometry, the technique allows us to obtain masses, radii, effective temperatures, bolometric fluxes, and hence distances for field stars in a self-consistent manner. We apply our method to 22 solar-like oscillators in the Kepler short-cadence sample, that have accurate Hipparcos parallaxes. Our distance determinations agree to better than 5%, while measurements of spectroscopic effective temperatures and interferometric radii also validate our results. We briefly discuss the potential of our technique for stellar population analysis and models of Galactic Chemical Evolution.

  8. Stellar Content of the Young Supershell GSH 305+01-24

    Science.gov (United States)

    Kaltcheva, N.; Golev, V.

    2013-06-01

    We combine several multi-wavelength surveys (Wisconsin Halpha Mapper Northern Sky Survey, MSX Mid-IR Galactic Plane Survey, WISE All-Sky Data Release, CO survey of the Milky Way, and the Southern Galactic Plane HI Survey) with intermediate-band uvby photometry to investigate the correlation between the young stars and various interstellar components related to the GSH 305+01-24 supershell seen toward Centaurus. The region shows striking similarities between the stellar distribution and Hα and HI emission morphologies. We identity 161 O-B9 stars at an average distance modulus 11.09 ± 0.71 (s.d.) mag located within the supershell and study their interaction with the surrounding interstellar material.

  9. Broadband luminescent materials in waveguide geometry

    NARCIS (Netherlands)

    Pollnau, Markus

    In recent years, broadband fiber interferometers have become very popular as basic instruments used in optical low-coherence reflectometry for diagnostics of fiber and integrated optics devices or in optical coherence tomography (OCT) for imaging applications in the biomedical field. The

  10. BROADBAND TRAVELLING WAVE SEMICONDUCTOR OPTICAL AMPLIFIER

    DEFF Research Database (Denmark)

    2010-01-01

    Broadband travelling wave semiconductor optical amplifier (100, 200, 300, 400, 800) for amplification of light, wherein the amplifier (100, 200, 300, 400, 800) comprises a waveguide region (101, 201, 301, 401, 801) for providing confinement of the light in transverse directions and adapted...

  11. WIRELESS FIDELITY (Wi-Fi) BROADBAND NETWORK ...

    African Journals Online (AJOL)

    ES Obe

    broadband speed and coverage, while Wi-Fi can be integrated with WiMAX networks to provide Internet ... Microwave Access (WiMAX), IEEE 802.11 standards. 1.0 INTRODUCTION .... These 2G systems provided circuit- switched data ...

  12. 77 FR 36903 - Accelerating Broadband Infrastructure Deployment

    Science.gov (United States)

    2012-06-20

    ... the Nation's global competitiveness in the 21st century, driving job creation, promoting innovation, and expanding markets for American businesses. Broadband access also affords public safety agencies... infrastructure has been deployed in a vast majority of communities across the country, today too many areas still...

  13. 75 FR 27984 - Broadband Technology Opportunities Program

    Science.gov (United States)

    2010-05-19

    ... applications, including: streaming video (surveillance, remote monitoring); digital imaging; automatic vehicle location; computer-aided dispatching; electronic mail; mapping and GPS; remote database access; report... entities to deploy public safety broadband systems using the 700 MHz spectrum licensed to the PSST.\\13\\ The...

  14. 75 FR 29516 - Broadband Researchers' Data Workshop

    Science.gov (United States)

    2010-05-26

    ... foundation for long-term economic stability and prosperity.\\1\\ The increased availability and use of... telecommunications policies pertaining to the Nation's economic and technological advancement. In order to achieve... stakeholders to develop and implement economic and regulatory policies that foster broadband deployment and...

  15. Electromagnetically induced transparency with broadband laser pulses

    International Nuclear Information System (INIS)

    Yavuz, D. D.

    2007-01-01

    We suggest a scheme to slow and stop broadband laser pulses inside an atomic medium using electromagnetically induced transparency. Extending the suggestion of Harris et al. [Phys. Rev. Lett. 70, 552 (1993)], the key idea is to use matched Fourier components for the probe and coupling laser beams

  16. STELLAR ARCHAEOLOGY IN THE GALACTIC HALO WITH THE ULTRA-FAINT DWARFS. VI. URSA MAJOR II

    Energy Technology Data Exchange (ETDEWEB)

    Dall' Ora, M.; Ripepi, Vincenzo; Marconi, Marcella; Musella, Ilaria, E-mail: dallora@na.astro.it, E-mail: ripepi@na.astro.it, E-mail: marcella@na.astro.it, E-mail: ilaria@na.astro.it [INAF, Osservatorio Astronomico di Capodimonte, Napoli (Italy); and others

    2012-06-10

    We present a B, V color-magnitude diagram (CMD) of the Milky Way dwarf satellite Ursa Major II (UMa II), spanning the magnitude range from V {approx} 15 to V {approx} 23.5 mag and extending over an 18 Multiplication-Sign 18 arcmin{sup 2} area centered on the Galaxy. Our photometry goes down to about 2 mag below the Galaxy's main-sequence turnoff that we detected at V {approx} 21.5 mag. We have discovered a bona fide RR Lyrae variable star in UMa II, which we use to estimate a conservative dereddened distance modulus for the galaxy of (m - M){sub 0} = 17.70 {+-} 0.04 {+-} 0.12 mag, where the first error accounts for the uncertainties of the calibrated photometry, and the second reflects our lack of information on the metallicity of the star. The corresponding distance to UMa II is 34.7{sup +0.6}{sub -0.7}({sup +2.0}{sub -1.9}) kpc. Our photometry shows evidence of a spread in the Galaxy's subgiant branch, compatible with a spread in metal abundance in the range between Z = 0.0001 and Z = 0.001. Based on our estimate of the distance, a comparison of the fiducial lines of the Galactic globular clusters M68 and M5 ([Fe/H] = -2.27 {+-} 0.04 dex and -1.33 {+-} 0.02 dex, respectively), with the position on the CMD of spectroscopically confirmed Galaxy members, may suggest the existence of stellar populations of different metal abundance/age in the central region of UMa II.

  17. Magnetohydrodynamic instabilities in a stellarator

    International Nuclear Information System (INIS)

    Matsuoka, K.; Miyamoto, K.; Ohasa, K.; Wakatani, M.

    1977-05-01

    Numerical studies of stability on kink and resistive tearing modes in a linear stellarator are presented for various current profiles and helical fields. In the case of an l = 2 helical field, a magnetic shear vanishes and the stability diagram is given by the straight lines with iota sup(σ) + iota sup(delta) = const., where iota sup(σ) is a rotational transform due to the plasma current and iota sup(delta) is due to the helical field. In the l = 2 stellarator with chi sup(delta) > 0.5, the m.h.d. stability against kink and tearing modes is improved compared with that in tokamaks. While an l = 3 helical component exists, the magnetic shear plays an important role in the stability properties. The stability diagrams become fairly complex; however, they can be explained by properties of the Euler equation. It should be noted that the internal kink modes become more unstable than in tokamaks by the l = 3 helical field. (auth.)

  18. Neoclassical transport simulations for stellarators

    International Nuclear Information System (INIS)

    Turkin, Y.; Beidler, C. D.; Maassberg, H.; Murakami, S.; Wakasa, A.; Tribaldos, V.

    2011-01-01

    The benchmarking of the thermal neoclassical transport coefficients is described using examples of the Large Helical Device (LHD) and TJ-II stellarators. The thermal coefficients are evaluated by energy convolution of the monoenergetic coefficients obtained by direct interpolation or neural network techniques from the databases precalculated by different codes. The temperature profiles are calculated by a predictive transport code from the energy balance equations with the ambipolar radial electric field estimated from a diffusion equation to guarantee a unique and smooth solution, although several solutions of the ambipolarity condition may exist when root-finding is invoked; the density profiles are fixed. The thermal transport coefficients as well as the ambipolar radial electric field are compared and very reasonable agreement is found for both configurations. Together with an additional W7-X case, these configurations represent very different degrees of neoclassical confinement at low collisionalities. The impact of the neoclassical optimization on the energy confinement time is evaluated and the confinement times for different devices predicted by transport modeling are compared with the standard scaling for stellarators. Finally, all configurations are scaled to the same volume for a direct comparison of the volume-averaged pressure and the neoclassical degree of optimization.

  19. THE STELLAR MASS DENSITY AND SPECIFIC STAR FORMATION RATE OF THE UNIVERSE AT z ∼ 7

    International Nuclear Information System (INIS)

    Gonzalez, Valentino; Bouwens, Rychard J.; Illingworth, Garth; Labbe, Ivo; Franx, Marijn; Kriek, Mariska; Brammer, Gabriel B.

    2010-01-01

    We use a robust sample of 11 z ∼ 7 galaxies (z 850 dropouts) to estimate the stellar mass density (SMD) of the universe when it was only ∼750 Myr old. We combine the very deep optical to near-infrared photometry from the Hubble Space Telescope Advanced Camera for Surveys and NICMOS cameras with mid-infrared Spitzer Infrared Array Camera (IRAC) imaging available through the GOODS program. After carefully removing the flux from contaminating foreground sources, we have obtained reliable photometry in the 3.6 μm and 4.5 μm IRAC channels. The spectral shapes of these sources, including their rest-frame optical colors, strongly support their being at z ∼ 7 with a mean photometric redshift of (z) = 7.2 ± 0.5. We use Bruzual and Charlot synthetic stellar population models to constrain their stellar masses and star formation histories. We find stellar masses that range over (0.1-12) x 10 9 M sun and average ages from 20 Myr to 425 Myr with a mean of ∼300 Myr, suggesting that in some of these galaxies most of the stars were formed at z > 8 (and probably at z ∼> 10). The best fits to the observed SEDs are consistent with little or no dust extinction, in agreement with recent results at z ∼ 4-8. The star formation rates (SFRs) are in the range from 5 to 20 M sun yr -1 . From this sample, we measure an SMD of 6.6 +5.4 -3.3 x 10 5 M sun Mpc -3 to a limit of M UV,AB z=3 ). Combined with a fiducial lower limit for their ages (80 Myr), this implies a maximum SFR density of 0.008 M sun yr -1 Mpc -3 . This is well below the critical level needed to reionize the universe at z ∼ 8 using standard assumptions. However, this result is based on luminous sources (>L*) and does not include the dominant contribution of the fainter galaxies. Strikingly, we find that the specific SFR is constant from z ∼ 7 to z ∼ 2 but drops substantially at more recent times.

  20. The Stellar Activity of TRAPPIST-1 and Consequences for the Planetary Atmospheres

    Science.gov (United States)

    Roettenbacher, Rachael M.; Kane, Stephen R.

    2017-12-01

    The signatures of planets hosted by M dwarfs are more readily detected with transit photometry and radial velocity methods than those of planets around larger stars. Recently, transit photometry was used to discover seven planets orbiting the late-M dwarf TRAPPIST-1. Three of TRAPPIST-1's planets fall in the Habitable Zone, a region where liquid water could exist on the planetary surface given appropriate planetary conditions. We aim to investigate the habitability of the TRAPPIST-1 planets by studying the star’s activity and its effect on the planets. We analyze previously published space- and ground-based light curves and show the photometrically determined rotation period of TRAPPIST-1 appears to vary over time due to complicated, evolving surface activity. The dramatic changes of the surface of TRAPPIST-1 suggest that rotation periods determined photometrically may not be reliable for this and similarly active stars. While the activity of the star is low, we use the premise of the “cosmic shoreline” to provide evidence that the TRAPPIST-1 environment has potentially led to the erosion of possible planetary atmospheres by extreme ultraviolet stellar emission.

  1. Star Classification for the Kepler Input Catalog: From Images to Stellar Parameters

    Science.gov (United States)

    Brown, T. M.; Everett, M.; Latham, D. W.; Monet, D. G.

    2005-12-01

    The Stellar Classification Project is a ground-based effort to screen stars within the Kepler field of view, to allow removal of stars with large radii (and small potential transit signals) from the target list. Important components of this process are: (1) An automated photometry pipeline estimates observed magnitudes both for target stars and for stars in several calibration fields. (2) Data from calibration fields yield extinction-corrected AB magnitudes (with g, r, i, z magnitudes transformed to the SDSS system). We merge these with 2MASS J, H, K magnitudes. (3) The Basel grid of stellar atmosphere models yields synthetic colors, which are transformed to our photometric system by calibration against observations of stars in M67. (4) We combine the r magnitude and stellar galactic latitude with a simple model of interstellar extinction to derive a relation connecting {Teff, luminosity} to distance and reddening. For models satisfying this relation, we compute a chi-squared statistic describing the match between each model and the observed colors. (5) We create a merit function based on the chi-squared statistic, and on a Bayesian prior probability distribution which gives probability as a function of Teff, luminosity, log(Z), and height above the galactic plane. The stellar parameters ascribed to a star are those of the model that maximizes this merit function. (6) Parameter estimates are merged with positional and other information from extant catalogs to yield the Kepler Input Catalog, from which targets will be chosen. Testing and validation of this procedure are underway, with encouraging initial results.

  2. Management of broadband technology and innovation policy, deployment, and use

    CERN Document Server

    Choudrie, Jyoti

    2013-01-01

    When one considers broadband, the Internet immediately springs to mind. However, broadband is impacting society in many ways. For instance, broadband networks can be used to deliver healthcare or community related services to individuals who don't have computers, have distance as an issue to contend with, or don't use the internet. Broadband can support better management of scarce energy resources with the advent of smart grids, enables improved teleworking capacity and opens up a world of new entertainment possibilities. Yet scholarly examinations of broadband technology have so far examin

  3. KIC 8462852: Maria Mitchell Observatory Photographic Photometry 1930 to 1985

    Science.gov (United States)

    Castelaz, Michael; Barker, Thurburn

    2018-01-01

    KIC 8462852 is an F3V star which decreased 20% in visual brightness twice from 5 to 20 days (Boyajian et al., 2016, MNRAS, 457, 3988) in 2011 and again in 2013. New observations show decreases of a few percent in May 2017 (Waagen 2017, AAVSO Alert Notice, 579), and reanalysis of Kepler data shows a variation of 928.25 days and 22 dimming events (Kiefer et al. 2017, accepted). Photometry from the All-Sky Automated Survey for Supernovae and the All-Sky Automated Survey (ASAS) indicate two brightening episodes and a steady decrease in magnitude of 6.3 +/- 1.4 mmag/yr (Simon et al 2017, accepted). Photometric studies from photographic plate collections include a light curve from 1338 Harvard College Observatory plates over the period 1890 to 1989 (Schaefer 2016, ApJ, 822, L34) that indicates KIC 8462852 is dimming 0.164 +/- 0.013 magnitudes per century. Hippke et al. (2016, ApJ, 825, 73) present B and V light curves from photometry from the Sonneberg Observatory photographic plate collection (Brauer and Fuhrmann 1992, Die Sterne, 68, 19) covering the period from 1934 to 1995. The light curve suggests less than 3% or 0.03 magnitude per century decrease in brightness, consistent with the ASAS light curve and Kepler data.Another consistent set of astronomical photographic plates with KIC 8462852 are in the Maria Mitchell Observatory (MMO) collection (Strelnitski 2009 in ASP Conference Series Vol. 410 p. 96). This collection is located in the Astronomical Photographic Data Archive at the Pisgah Astronomical Research Institute. We extracted the photographic magnitudes of KIC 8462852 from 743 plates from 1930 to 1988. We chose 8 nearby comparison stars within one spectral subclass and within 0.05 magnitudes of KIC 8462852, and not identified as variables. The photometry is calibrated to the USNO B filter, closest in bandpass to the emulsion wavelength sensitivity. The light curve of KIC 8462852 suggests a trend of about 0.1 +/- 0.07 magnitudes per century decrease, an

  4. Stellar Spectral Classification with Locality Preserving Projections ...

    Indian Academy of Sciences (India)

    With the help of computer tools and algorithms, automatic stellar spectral classification has become an area of current interest. The process of stellar spectral classification mainly includes two steps: dimension reduction and classification. As a popular dimensionality reduction technique, Principal Component Analysis (PCA) ...

  5. Enhanced-confinement class of stellarators

    International Nuclear Information System (INIS)

    Mynick, H.E.; Chu, T.K.; Boozer, A.H.

    1981-08-01

    A class of stellarators has been found in which the transport is reduced by an order of magnitude from transport in conventional stellarators, by localizing the helical ripple to the inside of the torus. The reduction is observed in numerical experiments and explained theoretically

  6. Theories for convection in stellar atmospheres

    International Nuclear Information System (INIS)

    Nordlund, Aa.

    1976-02-01

    A discussion of the fundamental differences between laboratory convection in a stellar atmosphere is presented. The shortcomings of laterally homogeneous model atmospheres are analysed, and the extent to which these shortcoming are avoided in the two-component representation is discussed. Finally a qualitative discussion on the scaling properties of stellar granulation is presented. (Auth.)

  7. Structure of stellar hydroxyl masers

    International Nuclear Information System (INIS)

    Reid, M.J.; Muhleman, D.O.; Moran, J.M.; Johnston, K.J.; Schwartz, P.R.

    1977-01-01

    This paper presents the results of two spectral-line very long baseline (VLB) interferometric experiments on stellar OH masers. These masers are usually associated with long-period variable stars, and exhibit a characteristic double-peaked 1612 MHz OH spectrum. The sources IRC +10011, R Aql, and U Ori were carefully studied in order to determine the spatial structure of their masers. Maser components in these sources exhibited a complex structure which can be interpreted in terms of ''core-halo'' models. For these sources, the emission at any velocity appears to originate from a small (approximately-less-than0.''03) region of brightness approximately-greater-than10 9 K, and from a large (approximately-greater-than0.''5) region of brightness approximately-less-than10 8 K. In IRC+10011, ''core'' components in the two OH peaks probably are separated by less than the apparent size of the ''halos.'' A map of the low-velocity emission of U Ori with a resolution of 0.''01 indicates that the ''cores'' are distributed over a region of only 0.''2. This region is smaller than the apparent sizes of the ''halos.'' Other sources surveyed to determine apparent maser sizes include IRC+50137, OH 1821--12, OH 1837--05, OH 26.5+0.6, W43 A, and VX Sgr at 1612 MHz; and W Hya, R Aql, and IRC--10529 at 1667 MHz. The results of all VLB observations of 1612 MHz stellar OH masers are summarized.The apparent sizes of the strongest components (''halos'') of stellar OH masers typically are approximately-greater-than0.''5, corresponding to linear dimensions of approximately-greater-than3 x 10 15 cm. These surprisingly large sizes imply brightness temperatures much lower than those observed in most other types of astronomical masers. The large sizes rule out models of the 1612 MHz OH masers that require contracting or rotating circumstellar envelopes to explain the double-peaked OH spectra, or that try to explain the apparent maser sizes in terms of interstellar or interplanetary scattering

  8. Wisconsin torsatron/stellarator program, FY 1989

    International Nuclear Information System (INIS)

    Shohet, J.L.; Anderson, D.T.; Anderson, F.S.B.; Talmadge, J.N.

    1988-07-01

    This proposal documents recent activities within the University of Wisconsin-Madison Torsatron/Stellarator Laboratory and presents plans for future research activities for a three year period. Research efforts have focused on fundamental stellarator physics issues through experimental investigations on the Interchangeable Module Stellarator (IMS) and the Proto-Cleo Stellarator. Theoretical activities and studies of new configurations are being undertaken to support and broaden the experimental program. Experimental research at the Torsatron Stellarator Laboratory has been primarily concerned with effects induced through electron-cyclotron resonant frequency plasma production and heating in the IMS device. Plasma electric fields have been shown to play a major role in particle transport and confinement in IMS. ECRF heating at 6 kG has produced electron tail populations in agreement with Monte-Carlo models. Electric and magnetic fields have been shown to alter the particle flows to the IMS modular divertors. 48 refs

  9. Astrospheres and Solar-like Stellar Winds

    Directory of Open Access Journals (Sweden)

    Wood Brian E.

    2004-07-01

    Full Text Available Stellar analogs for the solar wind have proven to be frustratingly difficult to detect directly. However, these stellar winds can be studied indirectly by observing the interaction regions carved out by the collisions between these winds and the interstellar medium (ISM. These interaction regions are called "astrospheres", analogous to the "heliosphere" surrounding the Sun. The heliosphere and astrospheres contain a population of hydrogen heated by charge exchange processes that can produce enough H I Ly alpha absorption to be detectable in UV spectra of nearby stars from the Hubble Space Telescope (HST. The amount of astrospheric absorption is a diagnostic for the strength of the stellar wind, so these observations have provided the first measurements of solar-like stellar winds. Results from these stellar wind studies and their implications for our understanding of the solar wind are reviewed here. Of particular interest are results concerning the past history of the solar wind and its impact on planetary atmospheres.

  10. Local government broadband policies for areas with limited Internet access

    Directory of Open Access Journals (Sweden)

    Yoshio Arai

    2014-03-01

    Full Text Available Despite their wide diffusion in developed countries, broadband services are still limited in areas where providing them is not profitable for private telecom carriers. To address this, many local governments in Japan have implemented broadband deployment projects subsidized by the national government. In this paper, we discuss local government broadband policies based on survey data collected from municipalities throughout the country. With the support of national promotion policies, broadband services were rapidly introduced to most local municipalities in Japan during the 2000s. Local government deployment policies helped to reduce the number of areas with no broadband access. A business model based on the Indefeasible Right of Use (IRU contract between a private telecom carrier and a local government has been developed in recent years. Even local governments without the technical capacity to operate a broadband business can introduce broadband services into their territory using the IRU business model.

  11. THERMAL X-RAY EMISSION FROM THE SHOCKED STELLAR WIND OF PULSAR GAMMA-RAY BINARIES

    Energy Technology Data Exchange (ETDEWEB)

    Zabalza, V.; Paredes, J. M. [Departament d' Astronomia i Meteorologia, Institut de Ciencies del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Marti i Franques 1, E08028 Barcelona (Spain); Bosch-Ramon, V., E-mail: vzabalza@am.ub.es [Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland)

    2011-12-10

    Gamma-ray-loud X-ray binaries are binary systems that show non-thermal broadband emission from radio to gamma rays. If the system comprises a massive star and a young non-accreting pulsar, their winds will collide producing broadband non-thermal emission, most likely originated in the shocked pulsar wind. Thermal X-ray emission is expected from the shocked stellar wind, but until now it has neither been detected nor studied in the context of gamma-ray binaries. We present a semi-analytic model of the thermal X-ray emission from the shocked stellar wind in pulsar gamma-ray binaries, and find that the thermal X-ray emission increases monotonically with the pulsar spin-down luminosity, reaching luminosities of the order of 10{sup 33} erg s{sup -1}. The lack of thermal features in the X-ray spectrum of gamma-ray binaries can then be used to constrain the properties of the pulsar and stellar winds. By fitting the observed X-ray spectra of gamma-ray binaries with a source model composed of an absorbed non-thermal power law and the computed thermal X-ray emission, we are able to derive upper limits on the spin-down luminosity of the putative pulsar. We applied this method to LS 5039, the only gamma-ray binary with a radial, powerful wind, and obtain an upper limit on the pulsar spin-down luminosity of {approx}6 Multiplication-Sign 10{sup 36} erg s{sup -1}. Given the energetic constraints from its high-energy gamma-ray emission, a non-thermal to spin-down luminosity ratio very close to unity may be required.

  12. Time-series photometric spot modeling. 2: Fifteen years of photometry of the bright RS CVn binary HR 7275

    Science.gov (United States)

    Strassmeier, K. G.; Hall, D. S.; Henry, G. W.

    1994-01-01

    We present a time-dependent spot modeling analysis of 15 consecutive years of V-band photometry of the long-period (P(sub orb) = 28.6 days) RS CVn binary HR 7275. This baseline in time is one of the longest, uninterrupted intervals a spotted star has been observed. The spot modeling analysis yields a total of 20 different spots throughout the time span of our observations. The distribution of the observed spot migration rates is consistent with solar-type differential rotation and suggests a lower limit of the differential-rotation coefficient of 0.022 +/-0.004. The observed, maximum lifetime of a single spot (or spot group) is 4.5 years, the minimum lifetime is approximately one year, but an average spot lives for 2.2 years. If we assume that the mechanical shear by differential rotation sets the upper limit to the spot lifetime, the observed maximum lifetime in turn sets an upper limit to the differential-rotation coefficient, namely 0.04 +/- 0.01. This would be differential rotation just 5 to 8 times less than the solar value and one of the strongest among active binaries. We found no conclusive evidence for the existence of a periodic phenomenon that could be attributed to a stellar magnetic cycle.

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

    International Nuclear Information System (INIS)

    McArthur, Barbara E.; Benedict, G. Fritz.; Cochran, William D.; Henry, Gregory W.; Hatzes, Artie; Harrison, Tom E.; Johns-Krull, Chris; Nelan, Ed

    2014-01-01

    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 −0.432 +0.924 M 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 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.

  14. Long-period variables in the Large Magellanic Cloud. II. Infrared photometry, spectral classification, AGB evolution, and spatial distribution

    International Nuclear Information System (INIS)

    Hughes, S.M.G.; Wood, P.R.

    1990-01-01

    Infrared JHK photometry and visual spectra have been obtained for a large sample of long-period variables (LPVs) in the Large Magellanic Cloud (LMC). Various aspects of the asymptotic giant branch (AGB) evolution of LPVs are discussed using these data. The birth/death rate of LPVs of different ages in the LMC is compared with the birth rates of appropriate samples of planetary nebulas, clump stars, Cepheids, and OH/IR stars. It appears that there are much fewer large-amplitude LPVs per unit galactic stellar mass in the LMC than in the Galaxy. It is suggested that this may be due to the fact that the evolved intermediate-age AGB stars in the LMC often turn into carbon stars, which tend to have smaller pulsation amplitudes than M stars. There is also a major discrepancy between the number of LPVs in the LMC (and in the Galaxy) and the number predicted by the theories of AGB evolution, pulsation, and mass loss. A distance modulus to the LMC of 18.66 + or - 0.05 is derived by comparing the LMC LPVs with P about 200 days with the 47 Tucanae Mira variables in the (K, log P) plane. 64 refs

  15. Stellarmak a hybrid stellarator: Spheromak

    International Nuclear Information System (INIS)

    Hartman, C.W.

    1980-01-01

    This paper discusses hybridization of modified Stellarator-like transform windings (T-windings) with a Spheromak or Field-Reversed-Mirror configuration. This configuration, Stellarmak, retains the important topological advantage of the Spheromak or FRM of having no plasma linking conductors or blankets. The T-windings provide rotational transformation in toroidal angle of the outer poloidal field lines, in effect creating a reversed B/sub Toroidal/ Spheromak or adding average B/sub T/ to the FRM producing higher shear, increased limiting β, and possibly greater stability to kinks and tilt. The presence of field ripple in the toroidal direction may be sufficient to inhibit cancellation of directed ion current by electron drag to allow steady state operation with the toroidal as well as poloidal current maintained by neutral beams

  16. Stellar Equilibrium in Semiclassical Gravity.

    Science.gov (United States)

    Carballo-Rubio, Raúl

    2018-02-09

    The phenomenon of quantum vacuum polarization in the presence of a gravitational field is well understood and is expected to have a physical reality, but studies of its backreaction on the dynamics of spacetime are practically nonexistent outside of the specific context of homogeneous cosmologies. Building on previous results of quantum field theory in curved spacetimes, in this Letter we first derive the semiclassical equations of stellar equilibrium in the s-wave Polyakov approximation. It is highlighted that incorporating the polarization of the quantum vacuum leads to a generalization of the classical Tolman-Oppenheimer-Volkoff equation. Despite the complexity of the resulting field equations, it is possible to find exact solutions. Aside from being the first known exact solutions that describe relativistic stars including the nonperturbative backreaction of semiclassical effects, these are identified as a nontrivial combination of the black star and gravastar proposals.

  17. On rapid rotation in stellarators

    International Nuclear Information System (INIS)

    Helander, Per

    2008-01-01

    The conditions under which rapid plasma rotation may occur in a three-dimensional magnetic field, such as that of a stellarator, are investigated. Rotation velocities comparable to the ion thermal speed are found to be attainable only in magnetic fields which are approximately isometric. In an isometric magnetic field the dependence of the magnetic field strength B on the arc length l along the field is the same for all field lines on each flux surface ψ. Only in fields where the departure from exact isometry, B=B(ψ,l), is of the order of the ion gyroradius divided by the macroscopic length scale are rotation speeds comparable to the ion thermal speed possible. Moreover, it is shown that the rotation must be in the direction of the vector ∇ψx∇B. (author)

  18. Magnetohydodynamics stability of compact stellarators

    International Nuclear Information System (INIS)

    Fu, G.Y.; Ku, L.P.; Cooper, W.A.; Hirshman, S.H.

    2000-01-01

    Recent stability results of external kink modes and vertical modes in compact stellarators are presented. The vertical mode is found to be stabilized by externally generated poloidal flux. A simple stability criterion is derived in the limit of large aspect ratio and constant current density. For a wall at infinite distance from the plasma, the amount of external flux needed for stabilization is given by Fi = (k2 minus k)=(k2 + 1), where k is the axisymmetric elongation and Fi is the fraction of the external rotational transform. A systematic parameter study shows that the external kink mode in QAS can be stabilized at high beta (approximately 5%) without a conducting wall by magnetic shear via 3D shaping. It is found that external kinks are driven by both parallel current and pressure gradient. The pressure contributes significantly to the overall drive through the curvature term and the Pfirsch-Schluter current

  19. NEMO: A Stellar Dynamics Toolbox

    Science.gov (United States)

    Barnes, Joshua; Hut, Piet; Teuben, Peter

    2010-10-01

    NEMO is an extendible Stellar Dynamics Toolbox, following an Open-Source Software model. It has various programs to create, integrate, analyze and visualize N-body and SPH like systems, following the pipe and filter architecture. In addition there are various tools to operate on images, tables and orbits, including FITS files to export/import to/from other astronomical data reduction packages. A large growing fraction of NEMO has been contributed by a growing list of authors. The source code consist of a little over 4000 files and a little under 1,000,000 lines of code and documentation, mostly C, and some C++ and Fortran. NEMO development started in 1986 in Princeton (USA) by Barnes, Hut and Teuben. See also ZENO (ascl:1102.027) for the version that Barnes maintains.

  20. Polarimetry and photometry of M87: is the jet fading

    Energy Technology Data Exchange (ETDEWEB)

    Warren-Smith, R F; King, D J; Scarrott, S M [Durham Univ. (UK). Dept. of Physics

    1984-09-15

    Optical linear polarization mapping and photometry of M87 is presented in B and R wavebands. The results indicate significant polarization in the galactic nucleus. Polarization in the jet in B is consistent with other recent maps obtained for this area in blue light and no significant variation with wavelength between B and R wavebands is found. The spectral index of the jet radiation is measured to be S=-1.65+-0.2 over the wavelength range observed. Comparison of the integrated B magnitude of the jet with previous independent measurements over the period 1934-80 suggests that the jet is variable and has been fading more or less uniformly by about 0.8 mag per decade between 1964 and 1980.

  1. Infrared polarimetry and photometry of BL Lac objects

    Energy Technology Data Exchange (ETDEWEB)

    Impey, C D; Brand, P W.J.L. [Edinburgh Univ. (UK); Wolstencroft, R D; Williams, P M [Royal Observatory, Edinburgh (UK)

    1982-07-01

    Infrared polarimetry and photometry have been obtained for a sample of 18 BL Lac objects. The data covers a period of one year and is part of a continuing monitoring programme; all observations were in the J,H and K wavebands. Large and variable degrees of polarization are a common property of the sample. Two BL Lac objects show wavelength-dependent polarization, with the polarization increasing towards shorter wavelengths, and two objects show evidence for position angle rotations over a five-day period. The relationship between changes in polarized and total flux is also discussed. The BL Lac objects cover an enormous range of infrared luminosity; the three most luminous having Lsub(IR) > 10/sup 46/ erg s/sup -1/ and the other end of the range having infrared luminosities similar to normal elliptical galaxies. These are the first published infrared polarimetric observations for eight of the sample.

  2. Polarimetry and photometry of the AM Her polar

    Energy Technology Data Exchange (ETDEWEB)

    Efimov, Yu S; Shakhovskoj, N M

    1982-01-01

    The results of the polarization observations and photometry of AM Her obtained during 11 nights from April to September 1978 are presented. The observations were carried out in V spectral region with time resolution of about four minutes. The results of measurements are in agreement with previous observations. The polarization maximum, being mostly on the 1.3 % level, was rising up to 2 % only at an active state of the star. No correlation was found between rapid variations of light and linear polarization at an inactive state of the star. The phase dependence of mean polarization parameters is revealed. The displaced dipole magnetic field with different strength on the poles is assumed for the polar model to interpret the vector diagram of polarization.

  3. Testbed for High-Acuity Imaging and Stable Photometry

    Science.gov (United States)

    Gregory, James

    This proposal from MIT Lincoln Laboratory (LL) accompanies the NASA/APRA proposal enti-tled THAI-SPICE: Testbed for High-Acuity Imaging - Stable Photometry and Image-Motion Compensa-tion Experiment (submitted by Eliot Young, Southwest Research Institute). The goal of the THAI-SPICE project is to demonstrate three technologies that will help low-cost balloon-borne telescopes achieve diffraction-limited imaging: stable pointing, passive thermal stabilization and in-flight monitoring of the wave front error. This MIT LL proposal supplies a key element of the pointing stabilization component of THAI-SPICE: an electronic camera based on an orthogonaltransfer charge-coupled device (OTCCD). OTCCD cameras have been demonstrated with charge-transfer efficiencies >0.99999, noise of 90%. In addition to supplying a camera with an OTCCD detector, MIT LL will help with integration and testing of the OTCCD with the THAI-SPICE payload’s guide camera.

  4. Near-infrared photometry of HDE 245770 (A 0535 + 26)

    International Nuclear Information System (INIS)

    Persi, P.; Ferrari-Toniolo, M.; Spada, G.; Conti, G.; Di Benedetto, P.; Tanzi, E.G.; Tarenghi, M.

    1979-01-01

    A derivation is presented of the optical-infrared energy distribution of the OBe star HDE 245770, the optical counterpart of the transient X-ray source A 0535 + 26, using infrared observations made in the period 1976 November - 1977 March and UBV photometry obtained by other workers in 1976 November. An infrared excess is evident with flux density Ssub(ν) varies as νsup(approximately 0.6). The excess is explained in terms of thermal free-free emission from an ionized gaseous envelope around the OBe star. Assuming a matter outflow through the envelope with uniform velocity of a few hundred km/s, a value is obtained for the mass loss rate in HDE 245770 of about 10 -6 solar masses/yr. (author)

  5. Photoelectric UBV and DDO photometry of NGC 5138

    International Nuclear Information System (INIS)

    Claria, J.J.

    1980-01-01

    Results of UBV photoelectric photometry in NGC 5138 are presented for 50 stars brighter than 14.0 mag. In addition, four probable red giants were also observed in the DDO system. Sixteen stars previously considered members by Lindoff (1972), were found not to be physically connected with the cluster. NGC 5138 is located 1.80 kpc from the Sun and the visual interstellar absorption determined from the reddened B stars amounts to Asub(v) = 0.75 mag. There of the four red stars observed in the DDO system were found to be cluster members. The mean cyanogen anomaly is = 0.043 +- 0.018(m.e.), which implies that NGC 5138 is richer in CN than the field K giants in the solar neighbourhodd, but poorer than the Hyades giants. The cluster age is estimated to be approx. 1.5 x 10 8 yr. (orig.)

  6. Results of the 2017 Mexican Asteroid Photometry Campaign - Part 1

    Science.gov (United States)

    Sada, Pedro; Loera-Gonzalez, Pablo; Olguin, Lorenzo; Saucedo-Morales, Julio C.; Ayala-Gómez, Sandra A.; Garza, Jaime R.

    2018-04-01

    We report the results for the first semester of the 2017 Mexican Asteroid Photometry Campaign. Asteroid 1218 Aster (synodic period of 3.1581 ± 0.0002 h and amplitude of 0.35 mag) was well observed and showed slight variations of its lightcurve at the end of the seven week observing window. An uncertain, but long, period of 93.23 ± 0.02 h and amplitude of 0.36 mag were estimated for 2733 Hamina from sparse data. Asteroid 8443 Svecica was also well observed and yielded a period of 20.9905 ± 0.0015 h and amplitude of 0.65 mag. Observations of NEA (143404) 2003 BD44 also resulted in an uncertain and long period of 78.617 ± 0.009 h and amplitude of 0.66 mag with a sparsely covered lightcurve.

  7. FRAM telescope - monitoring of atmospheric extinction and variable star photometry

    Science.gov (United States)

    Jurysek, J.; Honkova, K.; Masek, M.

    2015-02-01

    The FRAM (F/(Ph)otometric Robotic Atmospheric Monitor) telescope is a part of the Pierre Auger Observatory (PAO) located near town Malargüe in Argentina. The main task of the FRAM telescope is the continuous night - time monitoring of the atmospheric extinction and its wavelength dependence. The current methodology of the measurement of a atmospheric extinction and for instrumentation properties also allows simultaneous observation of other interesting astronomical targets. The current observations of the FRAM telescope are focused on the photometry of eclipsing binaries, positional refinement of minor bodies of the Solar system and observations of optical counterparts of gamma ray bursts. In this contribution, we briefly describe the main purpose of the FRAM telescope for the PAO and we also present its current astrono mical observing program.

  8. uvbyHβ photometry of UV-bright stars

    International Nuclear Information System (INIS)

    Wade, B.R.; Smith, L.F.

    1985-01-01

    uvbyHβ photometry is presented for 90 stars taken from an early version of the Carnochan and Wilson catalogue (1983. Mon. Not. R. astr. Soc. 202,317) of stars that have very negative UV colours. Two have definite UV excesses, (HD 36629, and HD81307). Four early-B stars have UV colours too positive for their visible classification, and β-indices that indicate higher luminosities than appear possible on galactic distribution grounds. Six late-B stars appear to have discordant flux distributions for which there are no obvious explanations. It is suggested that the high population of subluminous stars derived by Carnochan and Wilson is the product of the statistical treatment used and the extreme patchiness in the interstellar absorption. (author)

  9. Applied photometry, radiometry, and measurements of optical losses

    CERN Document Server

    Bukshtab, Michael

    2012-01-01

    Applied Photometry, Radiometry, and Measurements of Optical Losses reviews and analyzes physical concepts of radiation transfer, providing quantitative foundation for the means of measurements of optical losses, which affect propagation and distribution of light waves in various media and in diverse optical systems and components. The comprehensive analysis of advanced methodologies for low-loss detection is outlined in comparison with the classic photometric and radiometric observations, having a broad range of techniques examined and summarized: from interferometric and calorimetric, resonator and polarization, phase-shift and ring-down decay, wavelength and frequency modulation to pulse separation and resonant, acousto-optic and emissive - subsequently compared to direct and balancing methods for studying free-space and polarization optics, fibers and waveguides. The material is focused on applying optical methods and procedures for evaluation of transparent, reflecting, scattering, absorbing, and aggregat...

  10. A practical guide to lightcurve photometry and analysis

    CERN Document Server

    Warner, Brian D

    2016-01-01

    For those with access to even a modest telescope and CCD camera, this new and improved guide delivers all the information needed to take part in the scientific study of asteroids and variable stars. New techniques in photometry continue to be refined, and expert Brian Warner covers the developing territory in detail for those both new and experienced. Updated to reflect changes in telescope and CCD technology, it also includes an expanded chapter on the analysis of asteroid lightcurves to cover some of the common pitfalls that lead to incorrect answers as well as how to discover an asteroid satellite via lightcurves. With this information, amateur astronomers can use commercially available equipment to determine the rotation rate, size, and shape of asteroids. Similarly, it is possible to discover the size, temperature, and orbits of stars in binary systems by using this powerful technique. Brian Warner yet again delivers all the material needed for readers to understand the theory, and avoid the practical pi...

  11. Time Resolved Precision Differential Photometry with OAFA's Double Astrograph

    Science.gov (United States)

    González, E. P. A.; Podestá, F.; Podestá, R.; Pacheco, A. M.

    2018-01-01

    For the last 50 years, the Double Astrograph located at the Carlos U. Cesco station of the Observatorio Astronómico Félix Aguilar (OAFA), San Juan province, Argentina, was used for astrometric observations and research. The main programs involved the study of asteroid positions and proper motions of stars in the Southern hemisphere, being the latter a long time project that is near completion from which the SPM4 catalog is the most recent version (Girard et al. 2011). In this paper, new scientific applications in the field of photometry that can be accomplished with this telescope are presented. These first attempts show the potential of the instrument for such tasks.

  12. Asteroid models from photometry and complementary data sources

    Energy Technology Data Exchange (ETDEWEB)

    Kaasalainen, Mikko [Department of Mathematics, Tampere University of Technology (Finland)

    2016-05-10

    I discuss inversion methods for asteroid shape and spin reconstruction with photometry (lightcurves) and complementary data sources such as adaptive optics or other images, occultation timings, interferometry, and range-Doppler radar data. These are essentially different sampling modes (generalized projections) of plane-of-sky images. An important concept in this approach is the optimal weighting of the various data modes. The maximum compatibility estimate, a multi-modal generalization of the maximum likelihood estimate, can be used for this purpose. I discuss the fundamental properties of lightcurve inversion by examining the two-dimensional case that, though not usable in our three-dimensional world, is simple to analyze, and it shares essentially the same uniqueness and stability properties as the 3-D case. After this, I review the main aspects of 3-D shape representations, lightcurve inversion, and the inclusion of complementary data.

  13. Asteroid models from photometry and complementary data sources

    International Nuclear Information System (INIS)

    Kaasalainen, Mikko

    2016-01-01

    I discuss inversion methods for asteroid shape and spin reconstruction with photometry (lightcurves) and complementary data sources such as adaptive optics or other images, occultation timings, interferometry, and range-Doppler radar data. These are essentially different sampling modes (generalized projections) of plane-of-sky images. An important concept in this approach is the optimal weighting of the various data modes. The maximum compatibility estimate, a multi-modal generalization of the maximum likelihood estimate, can be used for this purpose. I discuss the fundamental properties of lightcurve inversion by examining the two-dimensional case that, though not usable in our three-dimensional world, is simple to analyze, and it shares essentially the same uniqueness and stability properties as the 3-D case. After this, I review the main aspects of 3-D shape representations, lightcurve inversion, and the inclusion of complementary data.

  14. Characterizing exoplanets atmospheres with space photometry at optical wavelengths

    Directory of Open Access Journals (Sweden)

    Parmentier Vivien

    2015-01-01

    Full Text Available Space photometry such as performed by Kepler and CoRoT provides exoplanets radius and phase curves with an exquisite precision. The phase curve constrains the longitudinal variation of the albedo and shed light on the horizontal distribution of clouds. The planet radius constraints thermal evolution of the planet, potentially unveiling its atmospheric composition. We present how the atmospheric circulation can affect the cloud distribution of three different planets, HD209458b, Kepler-7b and HD189733b based on three-dimensional models and analytical calculations. Then we use an analytical atmospheric model coupled to a state-of-the-art interior evolution code to study the role of TiO in shaping the thermal evolution and final radius of the planet.

  15. Electronographic photometry of star clusters in the Magellanic Clouds

    International Nuclear Information System (INIS)

    Walker, M.F.

    1979-01-01

    Electronographic magnitudes and colours of 78 stars in the cluster Hodge 11 in the Large Magellanic Cloud have been measured to V = 21.5 on electrographs taken with a Spectracon image-converter attached to the focus of the 1.5-m (60-inch) Cerro Tololo reflector. The zero point of the electronographic photometry was provided by photoelectric observations of four stars in the cluster field using the same telescope. The colour-magnitude diagram of the cluster consists of an evolved main sequence, whose termination point corresponds to an age of about 6 x 10 8 yr, but with a giant branch which is displaced blueward by about Δ(B-V) 0 = 0.4 from the positions of the giant branches of open clusters of similar age in our Galaxy. (author)

  16. Photometry of High-Redshift Gravitationally Lensed Type Ia Supernovae

    Science.gov (United States)

    Haynie, Annastasia

    2018-01-01

    Out of more than 1100 well-identified Type Ia Supernovae, only roughly 10 of them are at z> 1.5. High redshift supernovae are hard to detect but this is made easier by taking advantage of the effects of gravitational lensing, which magnifies objects in the background field of massive galaxy clusters. Supernova Nebra (z= ~1.8), among others, was discovered during observations taken as part of the RELICS survey, which focused on fields of view that experience strong gravitational lensing effects. SN Nebra, which sits behind galaxy cluster Abell 1763, is magnified and therefore appears closer and easier to see than with HST alone. Studying high-redshift supernovae like SN Nebra is an important step towards creating cosmological models that accurately describe the behavior of dark energy in the early Universe. Recent efforts have been focused on improving photometry and the building and fitting of preliminary light curves.

  17. SPITZER IRAC PHOTOMETRY FOR TIME SERIES IN CROWDED FIELDS

    Energy Technology Data Exchange (ETDEWEB)

    Novati, S. Calchi; Beichman, C. [NASA Exoplanet Science Institute, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Gould, A.; Fausnaugh, M.; Gaudi, B. S.; Pogge, R. W.; Wibking, B.; Zhu, W.; Poleski, R. [Department of Astronomy, Ohio State University, 140 W. 18th Ave., Columbus, OH 43210 (United States); Yee, J. C. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Bryden, G.; Henderson, C. B.; Shvartzvald, Y. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Carey, S. [Spitzer, Science Center, MS 220-6, California Institute of Technology, Pasadena, CA (United States); Udalski, A.; Pawlak, M.; Szymański, M. K.; Skowron, J.; Mróz, P.; Kozłowski, S. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Collaboration: Spitzer team; OGLE group; and others

    2015-12-01

    We develop a new photometry algorithm that is optimized for the Infrared Array Camera (IRAC) Spitzer time series in crowded fields and that is particularly adapted to faint or heavily blended targets. We apply this to the 170 targets from the 2015 Spitzer microlensing campaign and present the results of three variants of this algorithm in an online catalog. We present detailed accounts of the application of this algorithm to two difficult cases, one very faint and the other very crowded. Several of Spitzer's instrumental characteristics that drive the specific features of this algorithm are shared by Kepler and WFIRST, implying that these features may prove to be a useful starting point for algorithms designed for microlensing campaigns by these other missions.

  18. Gaia, an all-sky survey for standard photometry

    Science.gov (United States)

    Carrasco, J. M.; Weiler, M.; Jordi, C.; Fabricius, C.

    2017-03-01

    Gaia ESA's space mission (launched in 2013) includes two low resolution spectroscopic instruments (one in the blue, BP, and another in the red, RP, wavelength domains) to classify and derive the astrophysical parameters of the observed sources. As it is well known, Gaia is a full-sky unbiased survey down to about 20th magnitude. The scanning law yields a rather uniform coverage of the sky over the full extent (a minimum of 5 years) of the mission. Gaia data reduction is a global one over the full mission. Both sky coverage and data reduction strategy ensure an unprecedented all-sky homogeneous spectrophotometric survey. Certainly, that survey is of interest for current and future on-ground and space projects, like LSST, PLATO, EUCLID and J-PAS/J-PLUS among others. These projects will benefit from the large amount (more than one billion) and wide variety of objects observed by Gaia with good quality spectrophotometry. Synthetic photometry derived from Gaia spectrophotometry for any passband can be used to expand the set of standard sources for these new instruments to come. In the current Gaia data release scenario, BP/RP spectrophotometric data will be available in the third release (in 2018, TBC). Current preliminary results allow us to estimate the precision of synthetic photometry derived from the Gaia data. This already allows the preparation of the on-going and future surveys and space missions. We discuss here the exploitation of the Gaia spectrophotometry as standard reference due to its full-sky coverage and its expected photometric uncertainties derived from the low resolution Gaia spectra.

  19. Design, fabrication, and testing of stellar coronagraphs for exoplanet imaging

    Science.gov (United States)

    Knight, Justin M.; Brewer, John; Hamilton, Ryan; Ward, Karen; Milster, Tom D.; Guyon, Olivier

    2017-09-01

    Complex-mask coronagraphs destructively interfere unwanted starlight with itself to enable direct imaging of exoplanets. This is accomplished using a focal plane mask (FPM); a FPM can be a simple occulter mask, or in the case of a complex-mask, is a multi-zoned device designed to phase-shift starlight over multiple wavelengths to create a deep achromatic null in the stellar point spread function. Creating these masks requires microfabrication techniques, yet many such methods remain largely unexplored in this context. We explore methods of fabrication of complex FPMs for a Phased-Induced Amplitude Apodization Complex-Mask Coronagraph (PIAACMC). Previous FPM fabrication efforts for PIAACMC have concentrated on mask manufacturability while modeling science yield, as well as assessing broadband wavelength operation. Moreover current fabrication efforts are concentrated on assessing coronagraph performance given a single approach. We present FPMs fabricated using several process paths, including deep reactive ion etching and focused ion beam etching using a silicon substrate. The characteristic size of the mask features is 5μm with depths ranging over 1μm. The masks are characterized for manufacturing quality using an optical interferometer and a scanning electron microscope. Initial testing is performed at the Subaru Extreme Adaptive Optics testbed, providing a baseline for future experiments to determine and improve coronagraph performance within fabrication tolerances.

  20. GAMA/H-ATLAS: THE DUST OPACITY-STELLAR MASS SURFACE DENSITY RELATION FOR SPIRAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Grootes, M. W.; Tuffs, R. J.; Andrae, E. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Popescu, C. C.; Pastrav, B. [Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE (United Kingdom); Gunawardhana, M.; Taylor, E. N. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 206 (Australia); Kelvin, L. S.; Driver, S. P. [Scottish Universities' Physics Alliance (SUPA), School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS (United Kingdom); Liske, J. [European Southern Observatory, Karl-Schwarzschild Str. 2, D-85748 Garching (Germany); Seibert, M. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Graham, Alister W. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Baes, M. [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium); Baldry, I. K. [Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD (United Kingdom); Bourne, N. [Centre for Astronomy and Particle Theory, The School of Physics and Astronomy, Nottingham University, University Park Campus, Nottingham NG7 2RD (United Kingdom); Brough, S. [Australian Astronomical Observatory, P.O. Box 296, Epping, NSW 1710 (Australia); Cooray, A. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Dariush, A. [Physics Department, Imperial College, Prince Consort Road, London SW7 2AZ (United Kingdom); De Zotti, G. [INAF-Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, I-35122 Padova (Italy); Dunne, L., E-mail: meiert.grootes@mpi-hd.mpg.de [Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8140 (New Zealand); and others

    2013-03-20

    We report the discovery of a well-defined correlation between B-band face-on central optical depth due to dust, {tau}{sup f}{sub B}, and the stellar mass surface density, {mu}{sub *}, of nearby (z {<=} 0.13) spiral galaxies. This relation was derived from a sample of spiral galaxies taken from the Galaxy and Mass Assembly (GAMA) survey, which were detected in the FIR/submillimeter (submm) in the Herschel-ATLAS science demonstration phase field. Using a quantitative analysis of the NUV attenuation-inclination relation for complete samples of GAMA spirals categorized according to stellar mass surface density, we demonstrate that this correlation can be used to statistically correct for dust attenuation purely on the basis of optical photometry and Sersic-profile morphological fits. Considered together with previously established empirical relationships of stellar mass to metallicity and gas mass, the near linearity and high constant of proportionality of the {tau}{sub B}{sup f} - {mu}{sub *} relation disfavors a stellar origin for the bulk of refractory grains in spiral galaxies, instead being consistent with the existence of a ubiquitous and very rapid mechanism for the growth of dust in the interstellar medium. We use the {tau}{sub B}{sup f} - {mu}{sub *} relation in conjunction with the radiation transfer model for spiral galaxies of Popescu and Tuffs to derive intrinsic scaling relations between specific star formation rate (SFR), stellar mass, and stellar surface density, in which attenuation of the UV light used for the measurement of SFR is corrected on an object-to-object basis. A marked reduction in scatter in these relations is achieved which we demonstrate is due to correction of both the inclination-dependent and face-on components of attenuation. Our results are consistent with a general picture of spiral galaxies in which most of the submm emission originates from grains residing in translucent structures, exposed to UV in the diffuse interstellar