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Sample records for beta cephei stars

  1. Period change and stellar evolution of $\\beta$ Cephei stars

    CERN Document Server

    Neilson, Hilding R

    2015-01-01

    The $\\beta$ Cephei stars represent an important class of massive star pulsators probing the evolution of B-type stars and the transition from main sequence to hydrogen-shell burning evolution. By understanding $\\beta$ Cep stars, we gain insights into the detailed physics of massive star evolution such as rotational mixing, convective core overshooting, magnetic fields and stellar winds, all of which play important roles. Similarly, modeling their pulsation provides additional information into their interior structures. Furthermore, measurements of the rate of change of pulsation period offer a direct measure of $\\beta$ Cephei stellar evolution. In this work, we compute state-of-the-art stellar evolution models assuming different amounts of initial rotation and convective core overshoot and measure theoretical rates of period change for which we compare to rates previously measured for a sample of $\\beta$ Cephei stars. The results of this comparison are mixed. For three stars, the rates are too small to infer ...

  2. Constraints on model atmospheres from complex asteroseismology of the \\beta Cephei stars

    CERN Document Server

    Szewczuk, Wojciech; Daszyńska-Daszkiewicz, Jadwiga

    2012-01-01

    Using the method termed complex asteroseismology, we derive constraints on model atmospheres, in particular, on the NLTE effects. We fit simultaneously pulsational frequencies and the corresponding values of the nonadiabatic complex parameter f for the four \\beta Cephei stars: \\theta Oph, \

  3. Periodic Radio Continuum Emission Associated with the beta Cephei Star V2187 Cyg

    CERN Document Server

    Tapia, Mauricio; Tovmassian, Gagik; Rodriguez-Gomez, Vicente; Gonzalez-Buitrago, Diego; Zharikov, Sergei; Ortiz-Leon, Gisela N

    2014-01-01

    We present new optical time-resolved photometry and medium-resolution spectroscopy of V2187 Cyg. We confirm its classification as a beta Cephei star based on sinusoidal light variations with a period of 0.2539 days and mean amplitudes of 0.037 and 0.042 magnitudes in "i" and "V", respectively. We classified the spectrum of this star B2-3V with no evidence of variations in the profiles of its absorption lines in timescales of hours or days. The stellar spectrum is totally absent of emission lines. We detected unexpected faint radio continuum emission (between 0.4 and 0.8 mJy at 6-cm) showing a sinusoidal variation with a period of 12.8 days. The radio spectrum is thermal. We searched in the Very Large Array archive for radio continuum emission toward other 15 beta Cephei stars. None of these additional stars, some of them much closer to the Sun than V2187 Cyg, was detected, indicating that radio emission is extremely uncommon toward beta Cephei stars.

  4. A line-profile analysis of the large-amplitude beta Cephei star xi1 Canis Majoris

    NARCIS (Netherlands)

    Saesen, S.; Briquet, M.; Aerts, C.C.

    2006-01-01

    We present a detailed line-profile study of the beta Cephei star xi1 Canis Majoris, for which we have assembled numerous high-resolution spectra over a period of 4.5 years. It is the first time that the line-profile variations of this star have been analysed. We focused on the Si III line profiles c

  5. Asteroseismology of the Beta Cephei star Nu Eridani: photometric observations and pulsational frequency analysis

    CERN Document Server

    Handler, G; Jerzykiewicz, M; Krisciunas, K; Tshenye, T; Rodríguez, E; Costa, V; Zhou, A Y; Medupe, R; Phorah, W M; Garrido, R; Amado, P J; Paparo, M; Zsuffa, D; Ramokgali, L; Crowe, R; Purves, N; Avila, R; Knight, R; Brassfield, E; Kilmartin, P M; Cottrell, P L

    2004-01-01

    We undertook a multisite photometric campaign for the Beta Cephei star Nu Eridani. More than 600 hours of differential photoelectric uvyV photometry were obtained with 11 telescopes during 148 clear nights. The frequency analysis of our measurements shows that the variability of Nu Eri can be decomposed into 23 sinusoidal components, eight of which correspond to independent pulsation frequencies between 5 - 8 c/d. Some of these are arranged in multiplets, which suggests rotational m-mode splitting of nonradial pulsation modes as the cause. If so, the rotation period of the star must be between 30 - 60 d. One of the signals in the light curves of Nu Eri has a very low frequency of 0.432 c/d. It can be a high-order combination frequency or, more likely, an independent pulsation mode. In the latter case Nu Eri would be both a Beta Cephei star and a slowly pulsating B (SPB) star. The photometric amplitudes of the individual pulsation modes of Nu Eri appear to have increased by about 20 per cent over the last 40 y...

  6. Research study of Beta Cephei variable stars using data from OAO-2

    Science.gov (United States)

    Lesh, J. R.

    1975-01-01

    Photometric data from the Wisconsin Experiment package on OAO-2 were obtained for six Beta Cephei variable stars. The data were reduced in accordance with the OAO 2/Wisconsin Experiment Package Photometer Users Guide. For delta Cet and gamma Peg, there were enough data points to form reliable composite light curves at seven or eight ultraviolet wavelengths. The light curves are well represented by sine waves in phase with the blue light curve for each star. The amplitude of the light variation increases with shorter wavelengths. For theta Oph, epsilon Cen, eta Sco, and Lambda Sco, mean magnitudes and light ranges were obtained at several ultraviolet wavelengths. No significant differences were found between the mean, de-reddened ultraviolet colors of the observed stars, and the mean values for standard stars computed by Bottemiller. An attempt to derive a temperature scale from a comparison of the observed ultraviolet colors with Kurucz models was unsuccessful.

  7. Asteroseismology of the Beta Cephei star 12 (DD) Lacertae: photometric observations, pulsational frequency analysis and mode identification

    CERN Document Server

    Handler, G; Rodríguez, E; Uytterhoeven, K; Amado, P J; Dorokhova, T N; Dorokhov, N I; Poretti, E; Sareyan, J P; Parrao, L; Lorenz, D; Zsuffa, D; Drummond, R; Daszynska-Daszkiewicz, J; Verhoelst, T; De Ridder, J; Acke, B; Bourge, P O; Movchan, A I; Garrido, R; Paparo, M; Sahin, T; Antoci, V; Udovichenko, S N; Csorba, K; Crowe, R; Berkey, B; Stewart, S; Terry, D; Mkrtichian, D E; Aerts, C

    2006-01-01

    We report a multisite photometric campaign for the Beta Cephei star 12 Lacertae. 750 hours of high-quality differential photoelectric Stromgren, Johnson and Geneva time-series photometry were obtained with 9 telescopes during 190 nights. Our frequency analysis results in the detection of 23 sinusoidal signals in the light curves. Eleven of those correspond to independent pulsation modes, and the remainder are combination frequencies. We find some slow aperiodic variability such as that seemingly present in several Beta Cephei stars. We perform mode identification from our colour photometry, derive the spherical degree l for the five strongest modes unambiguously and provide constraints on l for the weaker modes. We find a mixture of modes of 0 <= l <= 4. In particular, we prove that the previously suspected rotationally split triplet within the modes of 12 Lac consists of modes of different l; their equal frequency splitting must thus be accidental. One of the periodic signals we detected in the light c...

  8. C-4 155 nm line in beta Cephei

    Science.gov (United States)

    Fischel, D.

    1972-01-01

    The class of early B variable stars known as beta Cephei stars are characterized by short-period radial velocity and light variations. The coolest stars of this group have an effective temperature of about 20,000 K and the hottest, about 28,000 K. These stars are not related to the classical Cepheids whose temperatures are of the order of 6000 K. The amplitude of the radial velocity variation beta Cephei stars is in the tens of kilometers per second and the light variation is less than 0.2 mag, that is, less than 10 percent. The fastest pulsation interval is 3 hr and the slowest is 6 hr. The prototype beta Cephei has a period of 4 hr 34 min. Ultraviolet observations were taken using OAO 2 to investigate the relationship between the visual and the ultraviolet variations.

  9. Magnetic Fields and UV-line Variability in beta Cephei

    NARCIS (Netherlands)

    R.S. Schnerr; H.F. Henrichs; S.P. Owocki; A. ud-Doula; R.H.D. Townsend

    2007-01-01

    We present results of numerical simulations of wind variability in the magnetic B1 IVe star beta Cephei. 2D-MHD simulations are used to determine the structure of the wind. From these wind models we calculate line profiles for different aspect angles to simulate rotation. The results are compared wi

  10. Discovery of the magnetic field in the pulsating B star beta Cephei

    CERN Document Server

    Henrichs, H F; Verdugo, E; Schnerr, R S; Neiner, C; Donati, J -F; Catala, C; Shorlin, S L S; Wade, G A; Veen, P M; Nichols, J S; Damen, E M F; Talavera, A; Hill, G M; Kaper, L; Tijani, A M; Geers, V C; Wiersema, K; Plaggenborg, B; Rygl, K L J

    2013-01-01

    Although the star itself is not He enriched, the periodicity and the variability in the UV wind lines of the pulsating B1 IV star beta Cep are similar to what is observed in magnetic He-peculiar B stars, suggesting that beta Cep is magnetic. We searched for a magnetic field using spectropolarimetry. From UV spectroscopy, we analysed the wind variability and investigated the correlation with the magnetic data. Using 130 time-resolved circular polarisation spectra, obtained with the MuSiCoS spectropolarimeter at the 2m TBL from 1998 until 2005, we applied the least-squares deconvolution method on the Stokes V spectra and derived the longitudinal component of the integrated magnetic field over the visible hemisphere of the star. We performed a period analysis on the magnetic data and on EW measurements of UV wind lines obtained over 17 years. We also analysed the short- and long-term radial velocity variations, which are due to the pulsations and the 90-year binary motion. beta Cep hosts a sinusoidally varying m...

  11. A high-resolution spectroscopy survey of beta Cephei pulsations in bright stars

    NARCIS (Netherlands)

    Telting, J.H.; Schrijvers, C.; Ilyin, I.V.; Uytterhoeven, K.; Ridder, J. de; Aerts, C.C.; Henrichs, H.F.

    2006-01-01

    We present a study of absorption line-profile variations in early-B type near-main-sequence stars without emission lines. We have surveyed a total of 171 bright stars using the Nordic Optical Telescope (NOTSA), William Herschel Telescope (ING) and Coud�uxiliary Telescope (ESO). Our sample contains 7

  12. Combining BRITE and ground-based photometry for the Beta Cephei star Nu Eridani: impact on photometric pulsation mode identification and detection of several g modes

    CERN Document Server

    Handler, G; Popowicz, A; Pigulski, A; Kuschnig, R; Zoclonska, E; Moffat, A F J; Weiss, W W; Grant, C C; Pablo, H; Whittaker, G N; Rucinski, S M; Ramiaramanantsoa, T; Zwintz, K; Wade, G A

    2016-01-01

    We report a simultaneous ground and space-based photometric study of the Beta Cephei star Nu Eridani. Half a year of observations have been obtained by four of the five satellites constituting BRITE-Constellation, supplemented with ground-based photoelectric photometry. We show that carefully combining the two data sets virtually eliminates the aliasing problem that often hampers time-series analyses. We detect 40 periodic signals intrinsic to the star in the light curves. Despite a lower detection limit we do not recover all the pressure and mixed modes previously reported in the literature, but we newly detect six additional gravity modes. This behaviour is a consequence of temporal changes in the pulsation amplitudes that we also detected for some of the p modes. We point out that the dependence of theoretically predicted pulsation amplitude on wavelength is steeper in visual passbands than those observationally measured, to the extent that the three dominant pulsation modes of Nu Eridani would be incorrec...

  13. On the use of rotational splitting asymmetries to probe the internal rotation profile of stars. Application to $\\beta$ Cephei stars

    CERN Document Server

    Suárez, J C; Goupil, M J; Janot-Pacheco, E

    2010-01-01

    Rotationally-split modes can provide valuable information about the internal rotation profile of stars. This has been used for years to infer the internal rotation behavior of the Sun. The present work discusses the potential additional information that rotationally splitting asymmetries may provide when studying the internal rotation profile of stars. We present here some preliminary results of a method, currently under development, which intends: 1) to understand the variation of the rotational splitting asymmetries in terms of physical processes acting on the angular momentum distribution in the stellar interior, and 2) how this information can be used to better constrain the internal rotation profile of the stars. The accomplishment of these two objectives should allow us to better use asteroseismology as a test-bench of the different theories describing the angular momentum distribution and evolution in the stellar interiors.

  14. Asteroseismology of the Beta Cephei star Nu Eridani -- IV. The 2003-4 multisite photometric campaign and the combined 2002-4 data

    CERN Document Server

    Jerzykiewicz, M; Shobbrook, R R; Pigulski, A; Medupe, R; Mokgwetsi, T; Tlhagwane, P; Rodríguez, E

    2005-01-01

    The second multisite photometric campaign devoted to Nu Eri is reported. For Nu Eri, analysis of the new data adds four independent frequencies to the nine derived previously from the 2002-3 data, three in the range from 7.20 to 7.93 c/d, and a low one, equal to 0.614 c/d. Combining the new and the old data results in two further independent frequencies, equal to 6.7322 and 6.2236 c/d. Altogether, the oscillation spectrum is shown to consist of 12 high frequencies and two low ones. The latter have u amplitudes about twice as large as the v and y amplitudes, a signature of high radial-order g modes. Thus, the suggestion that Nu Eri is both a Beta Cephei and an SPB star, put forward on the basis of the first campaign's data, is confirmed. Nine of the 12 high frequencies form three triplets, of which two are new. The triplets represent rotationally split l=1 modes, although in case of the smallest-amplitude one this may be questioned. Mean separations and asymmetries of the triplets are derived with accuracy suf...

  15. The 2003-4 multisite photometric campaign for the Beta Cephei and eclipsing star 16 (EN) Lacertae with an Appendix on 2 Andromedae, the variable comparison star

    CERN Document Server

    Jerzykiewicz, M; Daszynska-Daszkiewicz, J; Pigulski, A; Poretti, E; Rodriguez, E; Amado, P J; Kolaczkowski, Z; Uytterhoeven, K; Dorokhova, T N; Dorokhov, N I; Lorenz, D; Zsuffa, D; Kim, S -L; Bourge, P -O; Acke, B; De Ridder, J; Verhoelst, T; Drummond, R; Movchan, A I; Lee, J -A; Steslicki, M; Molenda-Zakowicz, J; Garrido, R; Kim, S -H; Michalska, G; Paparo, M; Antoci, V; Aerts, C

    2015-01-01

    A multisite photometric campaign for the Beta Cephei and eclipsing variable 16 Lacertae is reported. 749 h of high-quality differential photoelectric Stromgren, Johnson and Geneva time-series photometry were obtained with ten telescopes during 185 nights. After removing the pulsation contribution, an attempt was made to solve the resulting eclipse light curve by means of the computer program EBOP. Although a unique solution was not obtained, the range of solutions could be constrained by comparing computed positions of the secondary component in the Hertzsprung-Russell diagram with evolutionary tracks. For three high-amplitude pulsation modes, the uvy and the Geneva UBG amplitude ratios are derived and compared with the theoretical ones for spherical-harmonic degrees l <= 4. The highest degree, l = 4, is shown to be incompatible with the observations. One mode is found to be radial, one is l = 1, while in the remaining case l = 2 or 3. The present multisite observations are combined with the archival photo...

  16. Understanding the dynamical structure of pulsating stars: The center-of-mass velocity and the Baade-Wesselink projection factor of the beta-Cephei star alpha-Lupi

    CERN Document Server

    Nardetto, N; Fokin, A; Chapellier, E; Pietrzynski, G; Gieren, W; Graczyk, D; Mourard, D

    2013-01-01

    High-resolution spectroscopy of pulsating stars is a powerful tool to study the dynamical structure of their atmosphere. Lines asymmetry is used to derive the center-of-mass velocity of the star, while a direct measurement of the atmospheric velocity gradient helps determine the projection factor used in the Baade-Wesselink method of distance determination. We aim at deriving the center-of-mass velocity and the projection factor of the beta-Cephei star alpha-Lup. We present HARPS high spectral resolution observations of alpha-Lup. We calculate the first-moment radial velocities and fit the spectral line profiles by a bi-Gaussian to derive line asymmetries. Correlations between the gamma-velocity and the gamma-asymmetry (defined as the average values of the radial velocity and line asymmetry curves respectively) are used to derive the center-of-mass velocity of the star. By combining our spectroscopic determination of the atmospheric velocity gradient with a hydrodynamical modelof the photosphere of the star, ...

  17. Abundance of nine beta Cephei stars (Morel+, 2006) g spectroscopy with Ta/Al DROIDs: performance for different geometries

    NARCIS (Netherlands)

    Morel, T.; Butler, K.; Aerts, C.C.; Neiner, C.; Briquet, M.; Hijmering, R.A.; Jerjen, I.; Verhoeve, P.; Martin, D.D.E.; Peacock, A.; Kozorezov, A.G.; Venn, R.

    2006-01-01

    The equivalent widths (EWs) were measured on high-resolution spectra obtained with various echelle spectrographs (see Table 2 of paper for further details). Our EWs are systematically larger than the values quoted by Gies & Lambert (1992ApJ...387..673G) for the seven stars in common, but a similar t

  18. Planet Formation in Binary Stars: The case of Gamma Cephei

    CERN Document Server

    Kley, Wilhelm

    2008-01-01

    Over 30 planetary systems have been discovered to reside in binary stars. For small separations gravitational perturbation of the secondary star has a strong influence on the planet formation process. It truncates the protoplanetary disk, may shortens its lifetime, and stirs up the embedded planetesimals. Due to its small semi-major axis (18.5 AU) and large eccentricity (e=0.35) the binary $\\gamma$ Cephei represents a particularly challenging example. In the present study we model the orbital evolution and growth of embedded protoplanetary cores of about 30 earth masses in the putative protoplanetary disk surrounding the primary star in the $\\gamma$ Cep system. We assume coplanarity of the disk, binary and planet and perform two-dimensional hydrodynamic simulations of embedded cores in a protoplanetary disk. The presence of the eccentric secondary star perturbs the disk periodically and generates strong spiral arms at periapse which propagate toward the disk centre. The disk also becomes slightly eccentric (w...

  19. Discovery of the magnetic field in the pulsating B star β Cephei

    NARCIS (Netherlands)

    Henrichs, H.F.; de Jong, J.A.; Verdugo, E.; Schnerr, R.S.; Neiner, C.; Donati, J.-F.; Catala, C.; Shorlin, S.L.S.; Wade, G.A.; Veen, P.M.; Nichols, J.S.; Damen, E.M.F.; Talavera, A.; Hill, G.M.; Kaper, L.; Tijani, A.M.; Geers, V.C.; Wiersema, K.; Plaggenborg, B.; Rygl, K.L.J.

    2013-01-01

    Context. Although the star itself is not helium enriched, the periodicity and the variability in the UV wind lines of the pulsating B1 IV star β Cephei are similar to what is observed in magnetic helium-peculiar B stars, suggesting that β Cep is magnetic. Aims. We searched for a magnetic field using

  20. Modelling hybrid Beta Cephei/SPB pulsations: Gamma Pegasi

    CERN Document Server

    Zdravkov, T

    2009-01-01

    Recent photometric and spectroscopic observations of the hybrid variable Gamma Pegasi (Handler et al. 2009, Handler 2009) revealed 6 frequencies of the SPB type and 8 of the Beta Cep type pulsations. Standard seismic models, which have been constructed with OPAL (Iglesias & Rogers 1996) and OP (Seaton 2005) opacities by fitting three frequencies (those of the radial fundamental and two dipole modes), do not reproduce the frequency range of observed pulsations and do not fit the observed individual frequencies with a satisfactory accuracy. We argue that better fitting can be achieved with opacity enhancements, over the OP data, by about 20-50 percent around the opacity bumps produced by excited ions of the iron-group elements at temperatures of about 200 000 K (Z bump) and 2 million K (Deep Opacity Bump).

  1. Instability strips of main sequence B stars: a parametric study of iron enhancement

    CERN Document Server

    Miglio, A; Montalban, J; Dupret, M A

    2006-01-01

    The discovery of beta Cephei stars in low metallicity environments, as well as the difficulty to theoretically explain the excitation of the pulsation modes observed in some beta Cephei and SPB stars, suggest that the iron opacity ``bump'' provided by standard models could be underestimated. We investigate, by means of a parametric study, the effect of a local iron enhancement on the location of the beta Cephei and SPB instability strips.

  2. Discovery of the magnetic field in the pulsating B star β Cephei

    Science.gov (United States)

    Henrichs, H. F.; de Jong, J. A.; Verdugo, E.; Schnerr, R. S.; Neiner, C.; Donati, J.-F.; Catala, C.; Shorlin, S. L. S.; Wade, G. A.; Veen, P. M.; Nichols, J. S.; Damen, E. M. F.; Talavera, A.; Hill, G. M.; Kaper, L.; Tijani, A. M.; Geers, V. C.; Wiersema, K.; Plaggenborg, B.; Rygl, K. L. J.

    2013-07-01

    Context. Although the star itself is not helium enriched, the periodicity and the variability in the UV wind lines of the pulsating B1 IV star β Cephei are similar to what is observed in magnetic helium-peculiar B stars, suggesting that β Cep is magnetic. Aims: We searched for a magnetic field using high-resolution spectropolarimetry. From UV spectroscopy, we analysed the wind variability and investigated the correlation with the magnetic data. Methods: We used 130 time-resolved circular polarisation spectra that were obtained from 1998 (when β Cep was discovered to be magnetic) to 2005, with the MuSiCoS échelle spectropolarimeter at the 2 m Télescope Bernard Lyot. We applied the least-square deconvolution method on the Stokes V spectra and derived the longitudinal component of the integrated magnetic field over the visible hemisphere of the star. We performed a period analysis on the magnetic data and on equivalent-width measurements of UV wind lines obtained over 17 years. We also analysed the short- and long-term radial velocity variations, which are due to the pulsations and the 90-year binary motion, respectively. Results: β Cep hosts a sinusoidally varying magnetic field with an amplitude 97 ± 4 G and an average value - 6 ± 3 G. From the UV wind line variability, we derive a period of 12.00075(11) days, which is the rotation period of the star, and is compatible with the observed magnetic modulation. Phases of maximum and minimum field match those of maximum emission in the UV wind lines, strongly supporting an oblique magnetic-rotator model. We discuss the magnetic behaviour as a function of pulsation behaviour and UV line variability. Conclusions: This paper presents the analysis of the first confirmed detection of a dipolar magnetic field in an upper main-sequence pulsating star. Maximum wind absorption originates in the magnetic equatorial plane. Maximum emission occurs when the magnetic north pole points to the Earth. Radial velocities agree with

  3. Asteroseismology with the WIRE satellite. I. Combining Ground- and Space-based Photometry of the Delta Scuti Star Epsilon Cephei

    CERN Document Server

    Bruntt, H; Bedding, T R; Buzasi, D L; Moya, A; Amado, P J; Martin-Ruiz, S; Garrido, R; De Coca, P L; Rolland, A; Costa, V; Olivares, I; Garcia-Pelayo, J M

    2006-01-01

    We have analysed ground-based multi-colour Stromgren photometry and single-filter photometry from the star tracker on the WIRE satellite of the delta scuti star Epsilon Cephei. The ground-based data set consists of 16 nights of data collected over 164 days, while the satellite data are nearly continuous coverage of the star during 14 days. The spectral window and noise level of the satellite data are superior to the ground-based data and this data set is used to locate the frequencies. However, we can use the ground-based data to improve the accuracy of the frequencies due to the much longer time baseline. We detect 26 oscillation frequencies in the WIRE data set, but only some of these can be seen clearly in the ground-based data. We have used the multi-colour ground-based photometry to determine amplitude and phase differences in the Stromgren b-y colour and the y filter in an attempt to identify the radial degree of the oscillation frequencies. We conclude that the accuracies of the amplitudes and phases a...

  4. uvbybeta photometry of early type open cluster and field stars

    CERN Document Server

    Handler, G

    2011-01-01

    The beta Cephei stars and slowly pulsating B (SPB) stars are massive main sequence variables. The strength of their pulsational driving strongly depends on the opacity of iron-group elements. As many of those stars naturally occur in young open clusters, whose metallicities can be determined in several fundamental ways, it is logical to study the incidence of pulsation in several young open clusters. To provide the foundation for such an investigation, Str\\"omgren-Crawford uvbybeta photometry of open cluster target stars was carried out to determine effective temperatures, luminosities, and therefore cluster memberships. In the course of three observing runs, uvbybeta photometry for 168 target stars was acquired and transformed into the standard system by measurements of 117 standard stars. The list of target stars also included some known cluster and field beta Cephei stars, as well as beta Cephei and SPB candidates that are targets of the asteroseismic part of the Kepler satellite mission. The uvbybeta phot...

  5. A BRITE view on delta Scuti and gamma Doradus stars

    CERN Document Server

    Zwintz, Konstanze

    2016-01-01

    BRITE-Constellation has obtained data for a few delta Scuti and gamma Doradus type stars. A short overview of the pulsational content found in five stars - beta Cassiopeiae, epsilon Cephei, M Velorum, beta Pictoris and QW Puppis - is given and the potential of BRITE-Constellation observations of delta Scuti and gamma Doradus pulsators is discussed.

  6. Multiple short-lived stellar prominences on O stars: The O6.5I(n)fp star λ Cephei

    Science.gov (United States)

    Sudnik, N. P.; Henrichs, H. F.

    2016-10-01

    Context. Most O-type stars and many B stars show unexplained cyclical variability in their spectral lines, i.e., modulation on the rotational timescale, but not strictly periodic. The variability occurs in the so-called discrete absorption components (DACs) that accelerate through the UV-wind line profiles and also in many optical lines. For such OB stars no dipolar magnetic fields have been detected with upper limits of ~300 G. Aims: We investigate whether multiple magnetic loops on the surface rather than non-radial pulsations or a dipolar magnetic field can explain the observed cyclical UV and optical spectral line variability. Methods: We present time-resolved, high-resolution optical spectroscopy of the O6.5I(n)fp star λ Cephei. We apply a simplified phenomenological model in which multiple spherical blobs attached to the surface represent magnetic-loop structures, which we call stellar prominences, by analogy with solar prominences. We compare the calculated line profiles as a function of rotational phase, adopting a rotation period of 4.1 d, with observed relative changes in subsequent quotient spectra. Results: We identify many periodicities in spectral lines, almost none of which is stable over timescales from months to years. We show that the relative changes in various optical absorption and emission lines are often very similar. Our proposed model applied to the He ii λ4686 line can typically be fitted with 2-5 equatorial blobs with lifetimes between ~1 and 24 h. Conclusions: Given the irregular timescales involved, we propose that the azimuthal distribution of DACs correspond to the locations of stellar prominences attached to the surface. This could explain the observed variability of optical and UV lines, and put constraints on the strength and lifetime of these structures, which can be compared with recent theoretical predictions, in which bright magnetic surface spots are formed by the action of the subsurface convection zone. Based on

  7. The 2003-2004 multisite photometric campaign for the β Cephei and eclipsing star 16 (EN) Lacertae with an appendix on 2 Andromedae, the variable comparison star

    Science.gov (United States)

    Jerzykiewicz, M.; Handler, G.; Daszyńska-Daszkiewicz, J.; Pigulski, A.; Poretti, E.; Rodríguez, E.; Amado, P. J.; Kołaczkowski, Z.; Uytterhoeven, K.; Dorokhova, T. N.; Dorokhov, N. I.; Lorenz, D.; Zsuffa, D.; Kim, S.-L.; Bourge, P.-O.; Acke, B.; De Ridder, J.; Verhoelst, T.; Drummond, R.; Movchan, A. I.; Lee, J.-A.; Stȩślicki, M.; Molenda-Żakowicz, J.; Garrido, R.; Kim, S.-H.; Michalska, G.; Paparó, M.; Antoci, V.; Aerts, C.

    2015-11-01

    A multisite photometric campaign for the β Cephei and eclipsing variable 16 Lacertae is reported. 749 h of high-quality differential photoelectric Strömgren, Johnson and Geneva time series photometry were obtained with 10 telescopes during 185 nights. After removing the pulsation contribution, an attempt was made to solve the resulting eclipse light curve by means of the computer program EBOP. Although a unique solution was not obtained, the range of solutions could be constrained by comparing computed positions of the secondary component in the Hertzsprung-Russell diagram with evolutionary tracks. For three high-amplitude pulsation modes, the uvy and the Geneva UBG amplitude ratios are derived and compared with the theoretical ones for spherical-harmonic degrees ℓ ≤ 4. The highest degree, ℓ = 4, is shown to be incompatible with the observations. One mode is found to be radial, one is ℓ = 1, while in the remaining case ℓ = 2 or 3. The present multisite observations are combined with the archival photometry in order to investigate the long-term variation of the amplitudes and phases of the three high-amplitude pulsation modes. The radial mode shows a non-sinusoidal variation on a time-scale of 73 yr. The ℓ = 1 mode is a triplet with unequal frequency spacing, giving rise to two beat-periods, 720.7 d and 29.1 yr. The amplitude and phase of the ℓ = 2 or 3 mode vary on time-scales of 380.5 d and 43 yr. The light variation of 2 And, one of the comparison stars, is discussed in the appendix.

  8. Combining BRITE and ground-based photometry for the β Cephei star ν Eridani: impact on photometric pulsation mode identification and detection of several g modes

    Science.gov (United States)

    Handler, G.; Rybicka, M.; Popowicz, A.; Pigulski, A.; Kuschnig, R.; Zocłońska, E.; Moffat, A. F. J.; Weiss, W. W.; Grant, C. C.; Pablo, H.; Whittaker, G. N.; Ruciński, S. M.; Ramiaramanantsoa, T.; Zwintz, K.; Wade, G. A.

    2016-10-01

    We report a simultaneous ground and space-based photometric study of the β Cephei star ν Eridani. Half a year of observations have been obtained by four of the five satellites constituting BRITE-Constellation, supplemented with ground-based photoelectric photometry. We show that carefully combining the two data sets virtually eliminates the aliasing problem that often hampers time-series analyses. We detect 40 periodic signals intrinsic to the star in the light curves. Despite a lower detection limit we do not recover all the pressure and mixed modes previously reported in the literature, but we newly detect six additional gravity modes. This behaviour is a consequence of temporal changes in the pulsation amplitudes that we also detected for some of the p modes. We point out that the dependence of theoretically predicted pulsation amplitude on wavelength is steeper in visual passbands than those observationally measured, to the extent that the three dominant pulsation modes of ν Eridani would be incorrectly identified using data in optical filters only. We discuss possible reasons for this discrepancy.

  9. Combining BRITE and ground-based photometry for the β Cephei star ν Eridani: impact on photometric pulsation mode identification and detection of several g modes

    Science.gov (United States)

    Handler, G.; Rybicka, M.; Popowicz, A.; Pigulski, A.; Kuschnig, R.; Zocłońska, E.; Moffat, A. F. J.; Weiss, W. W.; Grant, C. C.; Pablo, H.; Whittaker, G. N.; Ruciński, S. M.; Ramiaramanantsoa, T.; Zwintz, K.; Wade, G. A.

    2017-01-01

    We report a simultaneous ground- and space-based photometric study of the β Cephei star ν Eridani. Half a year of observations have been obtained by four of the five satellites constituting BRITE-Constellation, supplemented with ground-based photoelectric photometry. We show that carefully combining the two data sets virtually eliminates the aliasing problem that often hampers time series analyses. We detect 40 periodic signals intrinsic to the star in the light curves. Despite a lower detection limit, we do not recover all the pressure and mixed modes previously reported in the literature, but we newly detect six additional gravity modes. This behaviour is a consequence of temporal changes in the pulsation amplitudes that we also detected for some of the p modes. We point out that the dependence of theoretically predicted pulsation amplitude on wavelength is steeper in visual passbands than those observationally measured, to the extent that three dominant pulsation modes of ν Eridani would be incorrectly identified using data in optical filters only. We discuss possible reasons for this discrepancy.

  10. Dynamics of the circumstellar gas in the Herbig Ae stars BF Orionis, SV Cephei, WW Vulpeculae and XY Persei

    CERN Document Server

    Mora, A; Natta, A; Grady, C A; De Winter, D; Davies, J K; Ferlet, R; Harris, A W; Miranda, L F; Montesinos, B; Oudmaijer, R D; Palacios, J; Quirrenbach, Andreas G; Rauer, H; Alberdi, A; Cameron, A; Deeg, H J; Garzón, F; Horne, K; Merin, B; Penny, A; Schneider, J; Solano, E; Tsapras, Y; Wesselius, P R

    2004-01-01

    We present high resolution (lambda / Delta_lambda = 49000) echelle spectra of the intermediate mass, pre-main sequence stars BF Ori, SV Cep, WW Wul and XY Per. The spectra cover the range 3800-5900 angstroms and monitor the stars on time scales of months and days. All spectra show a large number of Balmer and metallic lines with variable blueshifted and redshifted absorption features superimposed to the photospheric stellar spectra. Synthetic Kurucz models are used to estimate rotational velocities, effective temperatures and gravities of the stars. The best photospheric models are subtracted from each observed spectrum to determine the variable absorption features due to the circumstellar gas; those features are characterized in terms of their velocity, v, dispersion velocity, Delta v, and residual absorption, R_max. The absorption components detected in each spectrum can be grouped by their similar radial velocities and are interpreted as the signature of the dynamical evolution of gaseous clumps with, in m...

  11. Multiple short-lived stellar prominences on O stars: The O6.5I(n)fp star lambda Cephei

    OpenAIRE

    Sudnik, N. P.; Henrichs, H. F.

    2016-01-01

    Most O and many B stars show unexplained cyclical variability in their spectral lines, i.e. modulation on the rotational timescale, but not strictly periodic. The variability occurs in the so-called discrete absorption components (DACs) that accelerate through the UV-wind line profiles and also in many optical lines. For such OB stars no dipolar magnetic fields have been detected with upper limits of ~300G. We investigate whether multiple magnetic loops on the surface rather than non-radial p...

  12. Multiple short-lived stellar prominences on O stars: The O6.5I(n)fp star lambda Cephei

    CERN Document Server

    Sudnik, N P

    2016-01-01

    Most O and many B stars show unexplained cyclical variability in their spectral lines, i.e. modulation on the rotational timescale, but not strictly periodic. The variability occurs in the so-called discrete absorption components (DACs) that accelerate through the UV-wind line profiles and also in many optical lines. For such OB stars no dipolar magnetic fields have been detected with upper limits of ~300G. We investigate whether multiple magnetic loops on the surface rather than non-radial pulsations or a dipolar magnetic field can explain the observed cyclical UV and optical spectral line variability. We present time-resolved, high-resolution optical spectroscopy of the O6.5I(n)fp star lambda Cep. We apply a simplified phenomenological model in which multiple spherical blobs attached to the surface represent magnetic-loop structures, which we call stellar prominences, by analogy with solar prominences. We compare the calculated line profiles as a function of rotational phase, adopting a rotation period of 4...

  13. Double Star Measurements of Beta Scorpii

    Science.gov (United States)

    Gillette, Sean; Funk, Benjamin; Schlosser, Ruth; Brown, Alana; Cruz, Mallikai; McCarthy, Jeff; Rhoades, Breauna; Spreng, Bill

    2016-10-01

    Eight observers met at the Lewis Center for Educational Research in Apple Valley, California. These observers studied the distance and position angle between ß1 and ß2 of the beta Scorpii star system. They used the drift method to calibrate the telescope-eyepiece, which was a Celestron C8 Schmidt-Cassegrain telescope equipped with an astrometric eyepiece. The star system g Cassiopeia was used to determine the scale constant of 4.6 arcseconds per division mark, using the average of twelve observations made of the star system using the drift method. A separation of 15.4 arcseconds and a position angle of 14.3 was determined using a Bader Planetarium Micro Guide eyepiece with marking similar to a Celestron Micro Guide eyepiece. A large difference was found compared to WDS due in part to a smoky sky, an incoming storm, and the novice level of the team members, who had a difficult time reading the labels on the eyepiece.

  14. Revealing {\\delta} Cephei's Secret Companion and Intriguing Past

    CERN Document Server

    Anderson, Richard I; Holl, Berry; Eyer, Laurent; Palaversa, Lovro; Mowlavi, Nami; Süveges, Maria; Roelens, Maroussia

    2015-01-01

    Classical Cepheid variable stars are crucial calibrators of the cosmic distance scale thanks to a relation between their pulsation periods and luminosities. Their archetype, {\\delta} Cephei, is an important calibrator for this relation. In this paper, we show that {\\delta} Cephei is a spectroscopic binary based on newly-obtained high-precision radial velocities. We combine these new data with literature data to determine the orbit, which has period 2201 days, semi-amplitude 1.5 km/s, and high eccentricity (e = 0.647). We re-analyze Hipparcos intermediate astrometric data to measure {\\delta} Cephei's parallax ($\\varpi = 4.09 \\pm 0.16$ mas) and find tentative evidence for an orbital signature, although we cannot claim detection. We estimate that Gaia will fully determine the astrometric orbit. Using the available information from spectroscopy, velocimetry, astrometry, and Geneva stellar evolution models ($M_{\\delta Cep} ~ 5.0 - 5.25 M_\\odot$), we constrain the companion mass to within $0.2 < M_2 < 1.2 M_\\...

  15. The 2009 Eclipse of EE Cephei: An Educational and Collaborative Journey

    Science.gov (United States)

    Pye, John; Elder, Lauren; Hopkins, Jeff

    2009-05-01

    In December 2008 Jeff Hopkins of the Hopkins Phoenix Observatory (HPO) put out a request for assistance in extracting data from images taken by the AAVSO SRO (Sonoita Research Observatory) of EE Cephei, an 11th magnitude (V) long period (5.6 years) eclipsing binary star system that was due to eclipse in January of 2009. The Hopkins Phoenix Observatory originally planned to do BVRI CCD photometry of EE Cephei for the 2009 eclipse, but equipment and logistical changes at HPO meant the EE Cephei project would not be possible. However, in the fall of 2008 Arne Henden of the AAVSO announced the availability of a remote robotic 16" telescope (the Sonoita Research Observatory) in southern Arizona for use by members of the AAVSO. Jeff Hopkins contacted Arne Henden and arrangements were made to have the EE Cephei star system imaged with BVRI filters beginning in November 2008 and running through February 2009. Image files were archived on the AAVSO web site. Soon after his initial request went out, Jeff Hopkins was contacted by John Pye from Maui Community College, who agreed to help with the project by having one of his students, Lauren Elder, examine the image files and extract EE Cephei and 3 comparison stars flux (ADU) counts for each band. The resulting data were then sent to the Hopkins Phoenix Observatory for data reduction and analysis. The project was a successful joint collaboration with 40 nights of observations for over 300 BVRI data points from 20 November 2008 to 17 February 2009. Light curves for each band as well as color indices were plotted and eclipse contact points were determined. The data were also contributed to the EE Cephei Campaign organized by Cezary Galan at the Centre for Astronomy at Nicolaus Copernicus University in Torun (Poland). Our results are plotted along with those of several dozen other observers from around the world.

  16. A Planetary Companion to gamma Cephei A

    CERN Document Server

    Hatzes, A P; Endl, M; McArthur, B; Paulson, D B; Walker, G A H; Campbell, B; Yang, S; Hatzes, Artie P.; Cochran, William D.; Endl, Michael; Arthur, Barbara Mc; Paulson, Diane B.; Walker, Gordon A. H.; Campbell, Bruce; Yang, Stephenson

    2003-01-01

    We report the detection of a planetary companion in orbit around the primary star of the binary system gamma~Cephei. High precision radial velocity measurements using 4 independent data sets spanning the time interval 1981 to 2002 reveal long-lived residual radial velocity variations that are coherent in phase and amplitude with a period or 2.47 years and a semi-amplitude of 27 m/s. These residual radial velocity variations are most likely caused by a planetary mass companion with Msin i = 1.59 M_Jupiter and an orbital semi-major axis of 2.03AU. We have carefully analyzed of all the available photometric and spectroscopic data. Our CaII H&K S-index measurements taken during 1998-2002 show no variations with the planet period. Analysis of high resolution spectra taken 1988-1995 shows that the changes in the mean bisector velocity span and curvature for this star is less than 5 m/s. The Hipparcos photometry for this star made during 1989 to 1992 is constant to less than 0.001 mag. An analysis of the Walker ...

  17. Time-resolved multicolour photometry of bright B-type variable stars in Scorpius

    CERN Document Server

    Handler, G

    2013-01-01

    The first two of a total of six nano-satellites that will constitute the BRITE-Constellation space photometry mission have recently been launched successfully. In preparation for this project, we carried out time-resolved colour photometry in a field that is an excellent candidate for BRITE measurements from space. We acquired 117 h of Stromgren uvy data during 19 nights. Our targets comprised the Beta Cephei stars Kappa and Lambda Sco, the eclipsing binary Mu 1 Sco, and the variable super/hypergiant Zeta 1 Sco. For Kappa Sco, a photometric mode identification in combination with results from the spectroscopic literature suggests a dominant (l, m) = (1, -1) Beta Cephei-type pulsation mode of the primary star. The longer period of the star may be a rotational variation or a g-mode pulsation. For Lambda Sco, we recover the known dominant Beta Cephei pulsation, a longer-period variation, and observed part of an eclipse. Lack of ultraviolet data precludes mode identification for this star. We noticed that the spe...

  18. The (BETA) Pictoris Phenomenon Among Herbig Ae/Be Stars

    Science.gov (United States)

    Grady, C. A.; Perez, M. R.; Talavera, A.; Bjorkman, K. S.; deWinter, D.; The, P.-S.; Molster, F. J.; vandenAncker, M. E.; Sitko, M. L.; Morrison, N. D.; Beaver, M. L.; McCollum, B.; Castelaz, M. W.

    1996-01-01

    We present a survey of high dispersion UV and optical spectra of Herbig Ae/Be (HAeBe) and related stars. We find accreting, circumstellar gas over the velocity range +100 to +400 km/s, and absorption profiles similar to those seen toward Beta Pic, in 36% of the 33 HAeBe stars with IUE data as well as in 3 non-emission B stars. We also find evidence of accretion in 7 HAeBe stars with optical data only. Line profile variability appears ubiquitous. As a group, the stars with accreting gas signatures have higher v sin i than the stars with outflowing material, and tend to exhibit large amplitude (greater than or equal to 1(sup m)) optical light variations. All of the program stars with polarimetric variations that are anti-correlated with the optical light, previously interpreted as the signature of a dust disk viewed close to equator-on, also show spectral signatures of accreting gas. These data imply that accretion activity in HAeBe stars is preferentially observed when the line of sight transits the circumstellar dust disk. Our data imply that the spectroscopic signatures of accreting circumstellar material seen in Beta Pic are not unique to that object, but instead are consistent with interpretation of Beta Pic as a comparatively young A star with its associated circumstellar disk.

  19. Mode selection in pulsating stars

    CERN Document Server

    Smolec, R

    2013-01-01

    In this review we focus on non-linear phenomena in pulsating stars the mode selection and amplitude limitation. Of many linearly excited modes only a fraction is detected in pulsating stars. Which of them and why (the problem of mode selection) and to what amplitude (the problem of amplitude limitation) are intrinsically non-linear and still unsolved problems. Tools for studying these problems are briefly discussed and our understanding of mode selection and amplitude limitation in selected groups of self-excited pulsators is presented. Focus is put on classical pulsators (Cepheids and RR Lyrae stars) and main sequence variables (delta Scuti and beta Cephei stars). Directions of future studies are briefly discussed.

  20. Period Changes and Evolution in Pulsating Variable Stars

    Science.gov (United States)

    Neilson, H. R.; Percy, J. R.; Smith, H. A.

    2016-12-01

    We review ways in which observations of the changing periods of pulsating variable stars can be used to detect and directly measure their evolution. We briefly describe the two main techniques of analysis-(O-C) analysis and wavelet analysis - and results for pulsating variable star types which are reasonably periodic: type I and II Cepheids, RR Lyrae stars, beta Cephei stars, and Mira stars. We comment briefly on delta Scuti stars and pulsating white dwarfs. For some of these variable star types, observations agree approximately with the predictions of evolutionary models, but there still exist significant areas of disagreement that challenge future models of stellar evolution. There may be a need, for instance, to include processes such as rotation, mass loss, and magnetic fields. There may also be non-evolutionary processes which are contributing to the period changes.

  1. Period Changes and Evolution in Pulsating Variable Stars

    CERN Document Server

    Neilson, Hilding R; Smith, Horace A

    2016-01-01

    We review ways in which observations of the changing periods of pulsating variable stars can be used to detect and directly measure their evolution. We briefly describe the two main techniques of analysis -- (O-C) analysis and wavelet analysis -- and results for pulsating variable star types which are reasonably periodic: type I and II Cepheids, RR Lyrae stars, beta Cephei stars, and Mira stars. We comment briefly on delta Scuti stars and pulsating white dwarfs. For some of these variable star types, observations agree approximately with the predictions of evolutionary models, but there still exist significant areas of disagreement that challenge future models of stellar evolution. There may be a need, for instance, to include processes such as rotation, mass loss, and magnetic fields. There may also be non-evolutionary processes which are contributing to the period changes.

  2. Planets in double stars: the cephei system

    Directory of Open Access Journals (Sweden)

    R. Dvorak

    2004-01-01

    Full Text Available Hasta ahora se tiene evidencia de unos 15 planetas en orbita alrededor de estrellas dobles. Todos pertenecen al llamado tipo S, es decir, orbitan en torno a la primaria. S olo dos de las binarias, Gliese 86 y Cep, tienen separaciones del orden de las dimensiones de las orbitas en el Sistema Solar. En este estudio, investigamos la estabilidad del planeta en Cep en relaci on a los par ametros orbitales de la binaria y del planeta. Adem as, investigamos la regi on dentro y fuera de la orbita del planeta (a = 2.1 AU. A un si la masa de un planeta adicional a 1 AU fuera del orden de la masa de J upiter, el planeta descubierto tendr a una orbita estable.

  3. Biodegradable star polymers functionalized with beta-cyclodextrin inclusion complexes.

    Science.gov (United States)

    Setijadi, Eki; Tao, Lei; Liu, Jingquan; Jia, Zhongfan; Boyer, Cyrille; Davis, Thomas P

    2009-09-14

    Three-armed biodegradable star polymers made from polystyrene (polySt) and poly (polyethylene glycol) acrylate (polyPEG-A) were synthesized via a "core first" methodology using a trifunctional RAFT agent, created by attaching RAFT agents to a core via their R-groups. The resultant three-armed polymeric structures were well-defined, with polydispersity indices less than 1.2. Upon aminolysis and further reaction with dithiodipyridine (DTDP), these three-armed polymers could be tailored with sulfhydryl and pyridyldisulfide (PDS) end functionalities, available for further reaction with any free-sulfhydryl group containing precursors to form disulfide linkages. Nuclear magnetic resonance (NMR) confirmed that more than 98% of the polymer arms retained integral trithiocarbonate active sites after polymerization. Intradisulfide linkages between the core and the arms conferred biodegradability on the star architectures. Subsequently, the arm-termini were attached to cholesterol also via disulfide linkages. The cholesterol terminated arms were then used to form supramolecular structures via inclusion complex formation with beta-cyclodextrin (beta-CD). The star architectures were found to degrade rapidly on treatment with DL-dithiothereitol (DTT). The star polymers and supramolecular structures were characterized using gel permation chromatography (GPC), static light scattering (SLS), 2D NMR, and fluorescence spectroscopy.

  4. B-type stars in eclipsing binaries

    Science.gov (United States)

    Ratajczak, Milena; Pigulski, Andrzej

    2016-07-01

    B-type stars in eclipsing binary systems are unique astrophysical tools to test several aspects of stellar evolution. Such objects can be used e.g. to determine the masses of Beta Cephei variable stars, as well as help to place tighter constraints on the value of the convective core overshooting parameter α. Both precise photometry and high-resolution spectroscopy with high SNR are required to achieve these goals, but since many of the targets are bright enough, the challenge is fair. Following this assumption, we shall explain how we plan to examine both the aforementioned aspects of stellar evolution using observations of B-type stars obtained with a wide range of spectrographs, as well as BRITE-Constellation satellites.

  5. Detection of a Proto-planetary Clump in the Habitable Zone of GM Cephei

    Science.gov (United States)

    Chen, W. P.; Hu, S. C.-L.

    2014-04-01

    GM Cephei is an active T Tauri star in the young open cluster Trumpler 37, showing abrupt UX Orionis type of photometric variability. Its light curves exhibit frequent, sporadic brightening events, each of <0.5 mag and lasting for days, which must have been originated from unsteady circumstellar accretion. In addition, the star undergoes a brightness drop up to ~1 mag lasting for about a month, during which the star became bluer when fainter. Moreover, the brightness drops seem to have a recurrence timescale of about 300 days. It is proposed that the brightness drop arises from obscuration of the central star by an orbiting dust concentration, exemplifying disk inhomogeneity in transition between grain coagulation and planetesimal formation in a young circumstellar disk. GM Cep was found to show a few percent polarization in the optical wavelengths, and an enhanced level of polarization during the occultation phase.

  6. The Beta Pictoris Phenomenon in A-Shell Stars: Detection of Accreting Gas

    Science.gov (United States)

    Grady, C. A.; Perez, Mario R.; Talavera, A.; McCollum, B.; Rawley, L. A.; England, M. N.; Schlegel, M.

    1996-01-01

    We present the results of an expanded survey of A-shell stars using IUE high-dispersion spectra and find accreting, circumstellar gas in the line of sight to nine stars, in addition to the previously identified beta Pic, HR 10, and 131 Tau, which can be followed to between +70 and 100 km/s relative to the star. Two of the program stars, HD 88195 and HD 148283, show variable high-velocity gas. Given the small number of IUE spectra for our program stars, detection of high-velocity, accreting gas in 2/3 of the A-shell stars sampled indicates that accretion is an intrinsic part of the A-shell phenomenon and that beta Pic is not unique among main-sequence A stars in exhibiting such activity. Our program stars, as a group, have smaller column densities of high-velocity gas and smaller near-IR excesses compared with beta Pic. These features are consistent with greater central clearing of a remnant debris disk, compared with beta Pic, and suggest that the majority of field A-shell stars are older than beta Pic.

  7. Separated Fringe Packet Observations with the CHARA Array II: $\\omega$ Andromeda, HD 178911, and {\\xi} Cephei

    CERN Document Server

    Farrington, Christopher D; Mason, Brian D; Hartkopf, William I; Mourard, Denis; Moravveji, Ehsan; McAlister, Harold A; Turner, Nils H; Sturmann, Laszlo; Sturmann, Judit

    2014-01-01

    When observed with optical long-baseline interferometers (OLBI), components of a binary star which are sufficiently separated produce their own interferometric fringe packets; these are referred to as Separated Fringe Packet (SFP) binaries. These SFP binaries can overlap in angular separation with the regime of systems resolvable by speckle interferometry at single, large-aperture telescopes and can provide additional measurements for preliminary orbits lacking good phase coverage, help constrain elements of already established orbits, and locate new binaries in the undersampled regime between the bounds of spectroscopic surveys and speckle interferometry. In this process, a visibility calibration star is not needed, and the separated fringe packets can provide an accurate vector separation. In this paper, we apply the SFP approach to {\\omega} Andromeda, HD 178911, and {\\xi} Cephei with the CLIMB three-beam combiner at the CHARA Array. For these systems we determine component masses and parallax of 0.963${\\pm...

  8. The radius and other fundamental parameters of the F9 V star beta Virginis

    CERN Document Server

    North, J R; Robertson, J G; Bedding, T R; Bruntt, H; Ireland, M J; Jacob, A P; Lacour, S; O'Byrne, J W; Owens, S M; Stello, D; Tango, W J; Tuthill, P G

    2008-01-01

    We have used the Sydney University Stellar Interferometer (SUSI) to measure the angular diameter of the F9 V star beta Virginis. After correcting for limb darkening and combining with the revised Hipparcos parallax, we derive a radius of 1.703 +/- 0.022 R_sun (1.3%). We have also calculated the bolometric flux from published measurements which, combined with the angular diameter, implies an effective temperature of 6059 +/- 49 K (0.8%). We also derived the luminosity of beta Vir to be L = 3.51 +/- 0.08 L_sun (2.1%). Solar-like oscillations were measured in this star by Carrier et al. (2005) and using their value for the large frequency separation yields the mean stellar density with an uncertainty of about 2%. Our constraints on the fundamental parameters of beta Vir will be important to test theoretical models of this star and its oscillations.

  9. The WFC3 Mosaic of The Star-Forming Galaxy M51 in Paschen beta

    Science.gov (United States)

    Koda, Jin

    2011-10-01

    We propose WFC3/IR Paschen beta imaging of the entire star-forming disk of M51 in a 10-point mosaic. This proposal is motivated by a new picture of gas evolution in galaxies from our recent observations in carbon-monoxide {CO} emission, namely one driven by galactic dynamics. The Paschen beta and archival ACS/Halpha images will enable correction for extinction throughout the entire M51 disk, and show an unprecedented map of star forming activity across the entire galaxy. By comparing this map with our new CO intensity and velocity maps, we will {1} place star formation in this new context of gas evolution, {2} study the triggering of star formation by correlating the star formation efficiency of individual GMC with global galactic structures {such as observed spiral shear motions and local gas convergence}, and {3} investigate the physics that underlie the Schmidt law by resolving the early-phases of star formation and its environment. The extinction-corrected map of star formation activity will become a reference for future calibration of other tracers of star formation activity and will have an unparalleled archival value.

  10. A POSSIBLE DETECTION OF OCCULTATION BY A PROTO-PLANETARY CLUMP IN GM Cephei

    Energy Technology Data Exchange (ETDEWEB)

    Chen, W. P.; Hu, S. C.-L.; Guo, J. K.; Hsiao, H. Y.; Lin, H. C.; Lin, C. S. [Graduate Institute of Astronomy, National Central University, 300 Jhongda Road, Jhongli 32001, Taiwan (China); Errmann, R.; Adam, Ch.; Baar, S.; Berndt, A.; Eisenbeiss, T.; Fiedler, S.; Ginski, Ch.; Graefe, C.; Hohle, M. M.; Kitze, M.; Maciejewski, G. [Astrophysikalisches Institut und Universitaets-Sternwarte, FSU Jena, Schillergaesschen 2-3, D-07745 Jena (Germany); Bukowiecki, L. [Torun Centre for Astronomy, Nicolaus Copernicus University, Gagarina 11, PL87-100 Torun (Poland); Dimitrov, D. P. [Institute of Astronomy and NAO, Bulg. Acad. Sc., 72 Tsarigradsko Chaussee Blvd., 1784 Sofia (Bulgaria); Janulis, R. [Moletai Observatory, Vilnius University (Lithuania); and others

    2012-06-01

    GM Cephei (GM Cep), in the young ({approx}4 Myr) open cluster Trumpler 37, has been known to be an abrupt variable and to have a circumstellar disk with a very active accretion. Our monitoring observations in 2009-2011 revealed that the star showed sporadic flare events, each with a brightening of {approx}< 0.5 mag lasting for days. These brightening events, associated with a color change toward blue, should originate from increased accretion activity. Moreover, the star also underwent a brightness drop of {approx}1 mag lasting for about a month, during which time the star became bluer when fainter. Such brightness drops seem to have a recurrence timescale of a year, as evidenced in our data and the photometric behavior of GM Cep over a century. Between consecutive drops, the star brightened gradually by about 1 mag and became blue at peak luminosity. We propose that the drop is caused by the obscuration of the central star by an orbiting dust concentration. The UX Orionis type of activity in GM Cep therefore exemplifies the disk inhomogeneity process in transition between the grain coagulation and the planetesimal formation in a young circumstellar disk.

  11. Aperture Fever and the Quality of AAVSO Visual Estimates: mu Cephei as an Example

    Science.gov (United States)

    Turner, D. G.

    2014-06-01

    (Abstract only) At the limits of human vision the eye can reach precisions of 10% or better in brightness estimates for stars. So why did the quality of AAVSO visual estimates suddenly drop to 50% or worse for many stars following World War II? Possibly it is a consequence of viewing variable stars through ever-larger aperture instruments than was the case previously, a time when many variables were observed without optical aid. An example is provided by the bright red supergiant variable mu Cephei, a star that has the potential to be a calibrating object for the extragalactic distance scale if its low-amplitude brightness variations are better defined. It appears to be a member of the open cluster Trumpler 37, so its distance and luminosity can be established provided one can pinpoint the amount of interstellar extinction between us and it. mu Cep appears to be a double-mode pulsator, as suggested previously in the literature, but with periods of roughly 700 and 1,000 days it is unexciting to observe and its red color presents a variety of calibration problems. Improving quality control for such variable stars is an issue important not only to the AAVSO, but also to science in general.

  12. Investigation of UBVRI Light Curves of LP Cephei

    Science.gov (United States)

    Carrigan, B.; Samec, R. G.; McDermith, R. J.

    1995-12-01

    In our study of eccentric eclipsing binary candidates (EEB's), we have obtained UBVRI CCD light curves of the LP Cephei, which was discovered by Wachmann (1972). The observations were taken 21 to 25 September 1994, inclusive, at Kitt Peak National Observatory, Arizona. The CCD photometer system (CCDPHOT) was used in conjunction with the 0.9 m Cassegrain reflector telescope. Five mean precision epochs of minimum light were determined from the observations made during primary and secondary eclipses. A period study has been conducted for all available data Analysis of both Wachmann's timings and our timings yielded the following linear ephemeris: HJD Min I = 2 449 621.732 19(78)d + 0.693 0625(1)XE. Despite the reported displacement of the secondary by Wachmann (1972) , we find that the secondary eclipse occurs at 0.5 phase. We have obtained standard magnitudes and estimated the amount of interstellar extinction for LP Cephei. Reddening Estimates indicate that LP Cephei consists of two B-type Near-Contact components. Simultaneous synthetic light curve solutions are discussed. The system is semidetatched: the secondary component fills its Roche lobe, while the primary component has a fillout of ~ 70 % of its Roche lobe.

  13. Detection of ultra-weak magnetic fields in Am stars: beta UMa and theta Leo

    CERN Document Server

    Blazère, A; Lignières, F; Aurière, M; ballot, J; Böhm, T; Folsom, C P; Gaurat, M; Jouve, L; Ariste, A Lopez; Neiner, C; Wade, G A

    2016-01-01

    An extremely weak circularly polarized signature was recently discovered in spectral lines of the chemically peculiar Am star Sirius A. A weak surface magnetic field was proposed to account for the observed polarized signal, but the shape of the phase-averaged signature, dominated by a prominent positive lobe, is not expected in the standard theory of the Zeeman effect. We aim at verifying the presence of weak circularly polarized signatures in two other bright Am stars, beta UMa and theta Leo, and investigating the physical origin of Sirius-like polarized signals further. We present here a set of deep spectropolarimetric observations of beta UMa and theta Leo, observed with the NARVAL spectropolarimeter. We analyzed all spectra with the Least Squares Deconvolution multiline procedure. To improve the signal-to-noise ratio and detect extremely weak signatures in Stokes V profiles, we co-added all available spectra of each star (around 150 observations each time). Finally, we ran several tests to evaluate wheth...

  14. Luminosity control and beam orbit stability with beta star leveling at LHC and HL-LHC

    CERN Document Server

    Gorzawski, Arkadiusz Andrzej; Wenninger, Jorg

    This thesis describes the wide subject of the luminosity leveling and its requirements for the LHC and the HL-LHC. We discuss the advantages and disadvantages of different leveling methods focusing the thesis on the beta star leveling technique. We review the beams offset build--up due to the environmental (i.e. natural ground motion) and mechanical (i.e. moving quadrupole) sources. We quantify the instrumentation requirements for the reliable and reproducible operation with small offsets at the interaction points. Last but not least, we propose a novel method for the beam offset stabilization at the collision point based on the feedback from the luminosity.

  15. Star formation triggered by SN explosions: an application to the stellar association of $\\beta$ Pictoris

    CERN Document Server

    Melioli, C; De la Reza, R; Raga, A

    2006-01-01

    In the present study, considering the physical conditions that are relevant in interactions between supernova remnants (SNRs) and dense molecular clouds for triggering star formation we have built a diagram of SNR radius versus cloud density in which the constraints above delineate a shaded zone where star formation is allowed. We have also performed fully 3-D radiatively cooling numerical simulations of the impact between SNRs and clouds under different initial conditions in order to follow the initial steps of these interactions. We determine the conditions that may lead either to cloud collapse and star formation or to complete cloud destruction and find that the numerical results are consistent with those of the SNR-cloud density diagram. Finally, we have applied the results above to the $\\beta-$Pictoris stellar association which is composed of low mass Post-T Tauri stars with an age of 11 Myr. It has been recently suggested that its formation could have been triggered by the shock wave produced by a SN e...

  16. Discovery of a brown dwarf companion to the A3V star \\beta{} Circini

    CERN Document Server

    Smith, L C; Peña, C Contreras; Kurtev, R; Marocco, F; Jones, H R A; Beamin, J C; Napiwotzki, R; Borissova, J; Burningham, B; Faherty, J; Pinfield, D J; Gromadzki, M; Ivanov, V D; Minniti, D; Stimson, W; Villanueva, V

    2015-01-01

    We report the discovery of an L dwarf companion to the A3V star \\beta{} Circini. VVV J151721.49-585131.5, or \\beta{} Cir B, was identified in a proper motion and parallax catalogue of the Vista Variables in the V\\'{i}a L\\'{a}ctea survey as having near infrared luminosity and colour indicative of an early L dwarf, and a proper motion and parallax consistent with that of \\beta{} Cir. The projected separation of $\\sim$3.6' corresponds to $6656$ au, which is unusually wide. The most recent published estimate of the age of the primary combined with our own estimate based on newer isochrones yields an age of $370-500$ Myr. The system therefore serves as a useful benchmark at an age greater than that of the Pleiades brown dwarfs and most other young L dwarf benchmarks. We have obtained a medium resolution echelle spectrum of the companion which indicates a spectral type of L1.0$\\pm$0.5 and lacks the typical signatures of low surface gravity seen in younger brown dwarfs. This suggests that signs of low surface gravit...

  17. Testing iSpec for the determination of atmospheric parameters and abundances of δ Cephei and RR Lyrae

    Science.gov (United States)

    Blanco-Cuaresma, S.; Anderson, R. I.; Eyer, L.; Mowlavi, N.

    2017-03-01

    Classical Cepheids and RR Lyrae stars are radially pulsating stars where the spectral type varies according to pulsation phase. Several studies used synthesis and the equivalent width method to determine the variations of effective temperature, surface gravity and metallicity for classical Cepheids and RR Lyrae stars (Luck and Andrievsky 2004; Kovtyukh et al. 2005; Andrievsky et al 2005; Luck et al 2008; Takeda et al. 2013; Fossati et al. 2014). We evaluated the applicability of iSpec (Blanco-Cuaresma et al. 2014 - http://www.blancocuaresma.com/s/), which has been extensively used with non-pulsating FGK stars, and derived atmospheric parameters as a function of phase for δ Cephei and RR Lyrae (the two prototypes stars for each class). The results showed that when we apply a non-adapted traditional spectroscopic method to pulsating stars, derived gravities do not seem to follow a physically logical evolution. Nevertheless, metallicity is globally stable and effective temperature variations globally agree with expectations from the radius variations indicated by the radial velocity variability. Max/min values and average results agree with the literature. In terms of broadening parameters, macroturbulent and projected rotation velocities are very difficult to disentangle even if their profiles are not exactly the same. Individual chemical abundances as function of phase are stable as it was expected (the chemical composition of the star should not vary). We plan to use this information to identify absorption lines that are reliable and stable (less affected by blending) during the whole pulsating cycle. This new line selection may help to improve the determination of atmospheric parameters and it could allow us to be more confident in the study of other less known Cepheids and RR Lyrae stars.

  18. The Relation Between [OIII]/H$\\beta$ and Specific Star Formation Rate in Galaxies at $z \\sim 2$

    CERN Document Server

    Dickey, Claire Mackay; Oesch, Pascal; Whitaker, Katherine; Momcheva, Ivelina; Nelson, Erica; Leja, Joel; Brammer, Gabriel; Franx, Marijn; Skelton, Rosalind

    2016-01-01

    Recent surveys have identified a seemingly ubiquitous population of galaxies with elevated [OIII]/H$\\beta$ emission line ratios at $z > 1$, though the nature of this phenomenon continues to be debated. The [OIII]/H$\\beta$ line ratio is of interest because it is a main component of the standard diagnostic tools used to differentiate between active galactic nuclei (AGN) and star-forming galaxies, as well as the gas-phase metallicity indicators $O_{23}$ and $R_{23}$. Here, we investigate the primary driver of increased [OIII]/H$\\beta$ ratios by median-stacking rest-frame optical spectra for a sample of star-forming galaxies in the 3D-HST survey in the redshift range $z\\sim1.4-2.2$. Using $N = 4220$ star-forming galaxies, we stack the data in bins of mass and specific star formation rates (sSFR) respectively. After accounting for stellar Balmer absorption, we measure [OIII]$\\lambda5007$\\AA/H$\\beta$ down to $\\mathrm{M} \\sim 10^{9.2} \\ \\mathrm{M_\\odot}$ and sSFR $\\sim 10^{-9.6} \\ \\mathrm{yr}^{-1}$, more than an ord...

  19. The Bursty Star Formation Histories of Low-mass Galaxies at $0.4Star Formation Rates Measured from FUV and H$\\beta$

    CERN Document Server

    Guo, Yicheng; Faber, S M; Koo, David C; Krumholz, Mark R; Trump, Jonathan R; Willner, S P; Amorín, Ricardo; Barro, Guillermo; Bell, Eric F; Gardner, Jonathan P; Gawiser, Eric; Hathi, Nimish P; Koekemoer, Anton M; Pacifici, Camilla; Pérez-González, Pablo G; Ravindranath, Swara; Reddy, Naveen; Teplitz, Harry I; Yesuf, Hassen

    2016-01-01

    We investigate the burstiness of star formation histories (SFHs) of galaxies at $0.4star formation rates (SFRs) measured from FUV (1500 \\AA) and H$\\beta$ (FUV--to--H$\\beta$ ratio). Our sample contains 164 galaxies down to stellar mass (M*) of $10^{8.5} M_\\odot$ in the CANDELS GOODS-N region, where TKRS Keck/DEIMOS spectroscopy and HST/WFC3 F275W images from CANDELS and HDUV are available. When the ratio of FUV- and H$\\beta$-derived SFRs is measured, dust extinction correction is negligible (except for very dusty galaxies) with the Calzetti attenuation curve. The FUV--to--H$\\beta$ ratio of our sample increases with the decrease of M* and SFR. The median ratio is $\\sim$1 at M* $\\sim 10^{10} M_\\odot$ (or SFR = 20 $M_\\odot$/yr) and increases to $\\sim$1.6 at M* $\\sim 10^{8.5} M_\\odot$ (or SFR $\\sim 0.5 M_\\odot$/yr). At M* $< 10^{9.5} M_\\odot$, our median FUV--to--H$\\beta$ ratio is higher than that of local galaxies at the same M*, implying a redshift evolution. Bursty SFH on a ...

  20. B fields in OB stars (BOB): on the detection of weak magnetic fields in the two early B-type stars beta CMa and epsilon CMa

    CERN Document Server

    Fossati, L; Morel, T; Langer, N; Briquet, M; Carroll, T A; Hubrig, S; Nieva, M F; Oskinova, L M; Przybilla, N; Schneider, F R N; Scholler, M; Simon-Diaz, S; Ilyin, I; de Koter, A; Reisenegger, A; Sana, H

    2014-01-01

    Within the context of the "B fields in OB stars (BOB)" collaboration, we used the HARPSpol spectropolarimeter to observe the early B-type stars beta CMa (HD44743; B1 II/III) and epsilon CMa (HD52089; B1.5 II). For both stars, we consistently detected the signature of a weak (<30 G in absolute value) longitudinal magnetic field. We determined the physical parameters of both stars and characterise their X-ray spectrum. For beta CMa, our mode identification analysis led to determining a rotation period of 13.6+/-1.2 days and of an inclination angle of the rotation axis of 57.6+/-1.7 degrees, with respect to the line of sight. On the basis of these measurements and assuming a dipolar field geometry, we derived a best fitting obliquity of ~22 degrees and a dipolar magnetic field strength (Bd) of ~100 G (60stars. For epsilon CMa we could only determine a lower limit on the dipolar magnetic field strength of 13 G. For this s...

  1. WZ Cephei: A Close Binary at the Beginning of Contact Phase

    Science.gov (United States)

    Zhu, L. Y.; Qian, S. B.

    2009-12-01

    Photometric photoelectric data of the short-period close binary system, WZ Cephei, are presented. A new photometric analysis with the 2003 version of the Wilson-Devinney method confirmed that it is a shallow contact binary (f ~ 13.3%) with a high level of spot activity on the primary component. Combining new determined times of light minimum with the others published in the literature, the period change of the binary star is investigated. A periodic variation, with a period of 34.2 years and an amplitude of 0fd013, was discovered to be superimposed on a long-term period decrease (dP/dt = -8.8 × 10-8 days year-1). Both the secular period decrease and the shallow contact configuration suggest that this binary system is at the beginning of contact phase. It is on the way to evolving into a normal overcontact phase via secular angular momentum loss and/or mass transfer from the more massive component to the less massive one. The period oscillation can be explained either by the light-time effect due to the presence of a third body or by magnetic activity. On the one hand, if it is caused by the light-time effect, the mass and the orbital radius of the additional body should be m 3 = 0.17 M sun and a 3 = 26.6 AU, respectively, when this body is coplanar to the orbit of the eclipsing pair. On the other hand, since the system shows high levels of spot activity, the period oscillation may be explained as a consequence of magnetic cycles. In this case, the required variation of the quadrupole moment is calculated to be 9.2 × 1049 g cm2.

  2. An ancient repeat sequence in the ATP synthase beta-subunit gene of forcipulate sea stars.

    Science.gov (United States)

    Foltz, David W

    2007-11-01

    A novel repeat sequence with a conserved secondary structure is described from two nonadjacent introns of the ATP synthase beta-subunit gene in sea stars of the order Forcipulatida (Echinodermata: Asteroidea). The repeat is present in both introns of all forcipulate sea stars examined, which suggests that it is an ancient feature of this gene (with an approximate age of 200 Mya). Both stem and loop regions show high levels of sequence constraint when compared to flanking nonrepetitive intronic regions. The repeat was also detected in (1) the family Pterasteridae, order Velatida and (2) the family Korethrasteridae, order Velatida. The repeat was not detected in (1) the family Echinasteridae, order Spinulosida, (2) the family Astropectinidae, order Paxillosida, (3) the family Solasteridae, order Velatida, or (4) the family Goniasteridae, order Valvatida. The repeat lacks similarity to published sequences in unrestricted GenBank searches, and there are no significant open reading frames in the repeat or in the flanking intron sequences. Comparison via parametric bootstrapping to a published phylogeny based on 4.2 kb of nuclear and mitochondrial sequence for a subset of these species allowed the null hypothesis of a congruent phylogeny to be rejected for each repeat, when compared separately to the published phylogeny. In contrast, the flanking nonrepetitive sequences in each intron yielded separate phylogenies that were each congruent with the published phylogeny. In four species, the repeat in one or both introns has apparently experienced gene conversion. The two introns also show a correlated pattern of nucleotide substitutions, even after excluding the putative cases of gene conversion.

  3. The Mass of the Planet-hosting Giant Star Beta Geminorum Determined from its p-mode Oscillation Spectrum

    CERN Document Server

    Hatzes, A P; Matthews, J; Kuschnig, R; Walker, G A H; Doellinger, M; Guenther, D B; Moffat, A F J; Rucinski, S M; Sasselov, D

    2012-01-01

    We use precise radial velocity measurements and photometric data to derive the frequency spacing of the p-mode oscillation spectrum of the planet-hosting star Beta Gem. This spacing along with the interferometric radius for this star is used to derive an accurate stellar mass. A long time series of over 60 hours of precise stellar radial velocity measurements of Beta Gem were taken with an iodine absorption cell and the echelle spectrograph mounted on the 2m Alfred Jensch Telescope. Complementary photometric data for this star were also taken with the MOST microsatellite spanning 3.6 d. A Fourier analysis of the radial velocity data reveals the presence of up to 17 significant pulsation modes in the frequency interval 10-250 micro-Hz. Most of these fall on a grid of equally-spaced frequencies having a separation of 7.14 +/- 0.12 micro-Hz. An analysis of 3.6 days of high precision photometry taken with the MOST space telescope shows the presence of up to 16 modes, six of which are consistent with modes found i...

  4. Erratum to Star formation triggered by SN explosions: an application to the stellar association of $\\beta$Pictoris

    CERN Document Server

    Melioli, C; Leão, M R M; De la Reza, R; Raga, A

    2007-01-01

    In the present study, considering the physical conditions that are relevant interactions between supernova remnants (SNRs) and dense molecular clouds for triggering star formation we have built a diagram of SNR radius versus cloud density in which the constraints above delineate a shaded zone where star formation is allowed. We have also performed fully 3-D radiatively cooling numerical simulations of the impact between SNRs and clouds under different initial conditions in order to follow the initial steps of these interactions. We determine the conditions that may lead either to cloud collapse and star formation or to complete cloud destruction and find that the numerical results are consistent with those of the SNR-cloud density diagram. Finally, we have applied the results above to the $\\beta-$ Pictoris stellar association which is composed of low mass Post-T Tauri stars with an age of 11 Myr. It has been recently suggested that its formation could have been triggered by the shock wave produced by a SN exp...

  5. Massive pulsating stars observed by BRITE-Constellation. I. The triple system Beta Centauri (Agena)

    CERN Document Server

    Pigulski, A; Popowicz, A; Kuschnig, R; Moffat, A F J; Rucinski, S M; Schwarzenberg-Czerny, A; Weiss, W W; Handler, G; Wade, G A; Koudelka, O; Matthews, J M; Mochnacki, St; Orleański, P; Pablo, H; Ramiaramanantsoa, T; Whittaker, G; Zocłońska, E; Zwintz, K

    2016-01-01

    This paper aims to precisely determine the masses and detect pulsation modes in the two massive components of Beta Cen with BRITE-Constellation photometry. In addition, seismic models for the components are considered and the effects of fast rotation are discussed. This is done to test the limitations of seismic modeling for this very difficult case. A simultaneous fit of visual and spectroscopic orbits is used to self-consistently derive the orbital parameters, and subsequently the masses, of the components. The derived masses are equal to 12.02 +/- 0.13 and 10.58 +/- 0.18 M_Sun. The parameters of the wider, A - B system, presently approaching periastron passage, are constrained. Analysis of the combined blue- and red-filter BRITE-Constellation photometric data of the system revealed the presence of 19 periodic terms, of which eight are likely g modes, nine are p modes, and the remaining two are combination terms. It cannot be excluded that one or two low-frequency terms are rotational frequencies. It is pos...

  6. Endoplasmic reticulum stress mediating downregulated StAR and 3-beta-HSD and low plasma testosterone caused by hypoxia is attenuated by CPU86017-RS and nifedipine

    Directory of Open Access Journals (Sweden)

    Liu Gui-Lai

    2012-01-01

    Full Text Available Abstract Background Hypoxia exposure initiates low serum testosterone levels that could be attributed to downregulated androgen biosynthesizing genes such as StAR (steroidogenic acute regulatory protein and 3-beta-HSD (3-beta-hydroxysteroid dehydrogenase in the testis. It was hypothesized that these abnormalities in the testis by hypoxia are associated with oxidative stress and an increase in chaperones of endoplasmic reticulum stress (ER stress and ER stress could be modulated by a reduction in calcium influx. Therefore, we verify that if an application of CPU86017-RS (simplified as RS, a derivative to berberine could alleviate the ER stress and depressed gene expressions of StAR and 3-beta-HSD, and low plasma testosterone in hypoxic rats, these were compared with those of nifedipine. Methods Adult male Sprague-Dawley rats were randomly divided into control, hypoxia for 28 days, and hypoxia treated (mg/kg, p.o. during the last 14 days with nifedipine (Nif, 10 and three doses of RS (20, 40, 80, and normal rats treated with RS isomer (80. Serum testosterone (T and luteinizing hormone (LH were measured. The testicular expressions of biomarkers including StAR, 3-beta-HSD, immunoglobulin heavy chain binding protein (Bip, double-strand RNA-activated protein kinase-like ER kinase (PERK and pro-apoptotic transcription factor C/EBP homologous protein (CHOP were measured. Results In hypoxic rats, serum testosterone levels decreased and mRNA and protein expressions of the testosterone biosynthesis related genes, StAR and 3-beta-HSD were downregulated. These changes were linked to an increase in oxidants and upregulated ER stress chaperones: Bip, PERK, CHOP and distorted histological structure of the seminiferous tubules in the testis. These abnormalities were attenuated significantly by CPU86017-RS and nifedipine. Conclusion Downregulated StAR and 3-beta-HSD significantly contribute to low testosterone in hypoxic rats and is associated with ER stress

  7. The radius and effective temperature of the binary Ap star beta CrB from CHARA/FLUOR and VLT/NACO observations

    CERN Document Server

    Bruntt, H; Merand, A; Brandao, I M; Bedding, T R; Brummelaar, T A ten; Foresto, V Coude du; Cunha, M S; Farrington, C; Goldfinger, P J; Kiss, L L; McAlister, H A; Ridgway, S T; Sturmann, J; Sturmann, L; Turner, N; Tuthill, P G

    2009-01-01

    The prospects for using asteroseismology of rapidly oscillating Ap (roAp) stars are hampered by the large uncertainty in fundamental stellar parameters. Results in the literature for the effective temperature (Teff) often span a range of 1000 K. Our goal is to reduce systematic errors and improve the Teff calibration of Ap stars based on new interferometric measurements. We obtained long-baseline interferometric observations of beta CrB using the CHARA/FLUOR instrument. To disentangle the flux contributions of the two components of this binary star, we obtained VLT/NACO adaptive optics images. We determined limb darkened angular diameters of 0.699+-0.017 mas for beta CrB A (from interferometry) and 0.415+-0.017 mas for beta CrB B (from surface brightness- color relations), corresponding to radii of 2.63+-0.09 Rsun (3.4 percent uncertainty) and 1.56+-0.07 Rsun (4.5 percent). The combined bolometric flux of the A and B components was determined from satellite UV data, spectrophotometry in the visible and broadb...

  8. Multitechnique testing of the viscous decretion disk model I. The stable and tenuous disk of the late-type Be star $\\beta$ CMi

    CERN Document Server

    Klement, R; Rivinius, T; Panoglou, D; Vieira, R G; Bjorkman, J E; Štefl, S; Tycner, C; Faes, D M; Korčáková, D; Müller, A; Zavala, R T; Curé, M

    2015-01-01

    The viscous decretion disk (VDD) model is able to explain most of the currently observable properties of the circumstellar disks of Be stars. However, more stringent tests, focusing on reproducing multitechnique observations of individual targets via physical modeling, are needed to study the predictions of the VDD model under specific circumstances. In the case of nearby, bright Be star $\\beta$ CMi, these circumstances are a very stable low-density disk and a late-type (B8Ve) central star. The aim is to test the VDD model thoroughly, exploiting the full diagnostic potential of individual types of observations, in particular, to constrain the poorly known structure of the outer disk if possible, and to test truncation effects caused by a possible binary companion using radio observations. We use the Monte Carlo radiative transfer code HDUST to produce model observables, which we compare with a very large set of multitechnique and multiwavelength observations that include ultraviolet and optical spectra, photo...

  9. A Coherent Study of Emission Lines from Broad-Band Photometry: Specific Star-Formation Rates and [OIII]/H{\\beta} Ratio at 3 < z < 6

    CERN Document Server

    Faisst, A L; Hsieh, B C; Laigle, C; Salvato, M; Tasca, L; Cassata, P; Davidzon, I; Ilbert, O; Fevre, O Le; Masters, D; McCracken, H J; Steinhardt, C; Silverman, J D; De Barros, S; Hasinger, G; Scoville, N Z

    2016-01-01

    We measure the H{\\alpha} and [OIII] emission line properties as well as specific star-formation rates (sSFR) of spectroscopically confirmed 33 cannot be fully explained in a picture of cold accretion driven growth. We find a progressively increasing [OIII]{\\lambda}5007/H{\\beta} ratio out to z~6, consistent with the ratios in local galaxies selected by increasing H{\\alpha} EW (i.e., sSFR). This demonstrates the potential of using "local high-z analogs" to investigate the spectroscopic properties and relations of galaxies in the re-ionization epoch.

  10. Optical polarimetry of star-forming regions

    Energy Technology Data Exchange (ETDEWEB)

    Gledhill, T.M.

    1987-01-01

    The polarimetric investigation of nebulosity associated with loss-mass pre-main sequence (PMS) stellar objects is detailed. Three regions of on-going star formation are considered, specifically, the Haro 6-5 and the HL/XZ Tau systems - both associated with dark clouds in the Taurus complex - and the PV Cephei nebulosity near NGC7023. In each region the imaging observations suggest bipolarity in the optical structure of the nebulosity, and the polarimetric data are used to determine the locations of the illuminating sources. Evidence is found for the association of circumstellar discs of obscuration with the PMS objects Haro 6-5A (FS Tau), Haro 6-5B, HL Tau, and PV Cephei. In each case the polarimetric data suggest that the local magnetic field has played an important role in the evolution of the star and the circumstellar material. Examination of the source-region polarization maps suggests that at least one of the objects considered is surrounded by a dust grain-aligning magnetic field with a predominantly toroidal geometry in the plane of the circumstellar disc. Implications for current theories of outflow acceleration and cloud evolution are discussed.

  11. Nearby young stars selected by proper motion. I. Four new members of the Beta Pictoris moving group from the Tycho-2 catalog

    CERN Document Server

    Lepine, Sebastien

    2008-01-01

    We describe a procedure to identify stars from nearby moving groups and associations out of catalogs of stars with large proper motions. We show that from the mean motion vector of a known or suspected moving group, one can identify additional members of the group based on proper motion data and photometry in the optical and infrared, with minimal contamination from background field stars. We demonstrate the technique by conducting a search for low-mass members of the Beta Pictoris Moving Group in the Tycho-2 catalog. All known members of the moving group are easily recovered, and a list of 51 possible candidates is generated. Moving group membership is evaluated for 33 candidates based on X-ray flux from ROSAT, Halpha line emission, and radial velocity measurement from high-resolution infrared spectra obtained at IRTF. We confirm three of the candidates to be new members of the group: TYC 1186-706-1, TYC 7443-1102-1, and TYC 2211-1309-1 which are late-K and early-M dwarfs 45pc-60pc from the Sun. We also iden...

  12. MULTICOLOR U BV RI POLARIMETRY OF NGC 4755 AND THE B CEPHEI POPULATION

    Directory of Open Access Journals (Sweden)

    E. Irene Vega

    2015-01-01

    Full Text Available Se presentan observaciones polarimétricas en las bandas U BV RI de 66 estrellas situadas en la dirección del cúmulo NGC 4755, incluyendo once β Cephei. Casi la mitad de estas variables muestran indicios de polarización intrínseca, pero según la teoría ninguna clase de pulsación puede originarla. Del análisis de las principales características de sus curvas Pv vs. λv hemos encontrado posibles orígenes de la dispersión de la luz en atmósferas extendidas, así como sospechas de binaridad en algunos casos. La polarización media para los miembros de NGC 4755 es Pv = 2.76%, con θv = 76.°6. Las partículas tienen un tamaño medio normal para el ISM, y la eficiencia es elevada. Con el uso exclusivo de herramientas polarimétricas se han identificado un total de 25 estrellas miembro.

  13. Third Order Effect of Rotation on Stellar Oscillations of a B Star

    Institute of Scientific and Technical Information of China (English)

    K. Karami

    2008-01-01

    We aim at investigating the effect of rotation up to the third order in the angular velocity of a star on the p and g modes, based on the formalism developed by Soufi et al. Our ultimate goal is the study of oscillations of β Cephei stars which are often rapidly rotating stars. Our results show that the third-order perturbation formalism presented by Soufi et al. should be corrected for some missing terms and some misprints in the equations. As a first step in our study of β Cephei stars, we quantify by numerical calculations the effect of rotation on the oscillation frequencies of a uniformly rotating zero-age main-sequence star with 12 M. For an equatorial velocity of 100km s-1, it is found that the second-and third-order corrections for (l, m)=(2, 2), for instance, are of the order of 0.01% of the frequency for radial order n=6 and reaches up to 0.5% for n=14.

  14. Measurement of amplitude detuning at flat-top and beta star = 0.6 m using AC dipoles

    CERN Document Server

    Bach, T; Langner, A; Levinsen, Z I; Miyamoto, R; Maclean, E H; McAteer, M J; Redaelli, R; Skowronski, P K; Tomas, R; Persson, T H B; White, S

    2013-01-01

    This paper reports on the first direct measurement of amplitude detuning using AC dipoles. The only means in the LHC at high energy to excite large betatron oscillations is using AC dipoles. In the linear regime a perfect AC dipole does not excite the natural tune of the machine. This seriously challenges the measurement of the amplitude detuning by having to rely on imperfections in order to observe the natural tune. The measurements were carried out at $\\beta$*=0.6 m and at flat-top during two MD sessions in 12-10-2012 and 27-11-2012, respectively.

  15. Sparse aperture masking at the VLT II. Detection limits for the eight debris disks stars $\\beta$ Pic, AU Mic, 49 Cet, $\\eta$ Tel, Fomalhaut, g Lup, HD181327 and HR8799

    CERN Document Server

    Gauchet, L; Lagrange, A -M; Ehrenreich, D; Bonnefoy, M; Girard, J H; Boccaletti, A

    2016-01-01

    Context. The formation of planetary systems is a common, yet complex mechanism. Numerous stars have been identified to possess a debris disk, a proto-planetary disk or a planetary system. The understanding of such formation process requires the study of debris disks. These targets are substantial and particularly suitable for optical and infrared observations. Sparse Aperture masking (SAM) is a high angular resolution technique strongly contributing to probe the region from 30 to 200 mas around the stars. This area is usually unreachable with classical imaging, and the technique also remains highly competitive compared to vortex coronagraphy. Aims. We aim to study debris disks with aperture masking to probe the close environment of the stars. Our goal is either to find low mass companions, or to set detection limits. Methods. We observed eight stars presenting debris disks ( $\\beta$ Pictoris, AU Microscopii, 49 Ceti, $\\eta$ Telescopii, Fomalhaut, g Lupi, HD181327 and HR8799) with SAM technique on the NaCo ins...

  16. The IRX-beta relation on sub-galactic scales in star-forming galaxies of the Herschel Reference Survey

    CERN Document Server

    Boquien, M; Boselli, A; Baes, M; Bendo, G J; Ciesla, L; Cooray, A; Cortese, L; Eales, S; Gavazzi, G; Gomez, H L; Lebouteiller, V; Pappalardo, C; Pohlen, M; Smith, M W L; Spinoglio, L

    2012-01-01

    UV and optical surveys are essential to gain insight into the processes driving galaxy formation and evolution. The rest-frame UV emission is key to measure the cosmic SFR. However, UV light is strongly reddened by dust. In starburst galaxies, the UV colour and the attenuation are linked, allowing to correct for dust extinction. Unfortunately, evidence has been accumulating that the relation between UV colour and attenuation is different for normal star-forming galaxies when compared to starburst galaxies. It is still not understood why star-forming galaxies deviate from the UV colour-attenuation relation of starburst galaxies. Previous work and models hint that the role of the shape of the attenuation curve and the age of stellar populations have an important role. In this paper we aim at understanding the fundamental reasons to explain this deviation. We have used the CIGALE SED fitting code to model the far UV to the far IR emission of a set of 7 reasonably face-on spiral galaxies from the HRS. We have exp...

  17. Planet formation in stellar binaries II: overcoming the fragmentation barrier in alpha Centauri and gamma Cephei-like systems

    CERN Document Server

    Rafikov, Roman R

    2014-01-01

    Planet formation in small-separation (~20 AU) eccentric binaries such as gamma Cephei or alpha Centauri is believed to be adversely affected by the presence of the stellar companion. Strong dynamical excitation of planetesimals by the eccentric companion can result in collisional destruction (rather than growth) of 1-100 km objects, giving rise to the "fragmentation barrier" for planet formation. We revise this issue using a novel description of secular dynamics of planetesimals in binaries, which accounts for the gravity of the eccentric, coplanar protoplanetary disk, as well as gas drag. By studying planetesimal collision outcomes we show, in contrast to many previous studies, that planetesimal growth and subsequent formation of planets (including gas giants) in AU-scale orbits within ~20 AU separation binaries may be possible, provided that the protoplanetary disks are massive (>10^{-2}M_\\odot) and only weakly eccentric (disk eccentricity <0.01). These requirements are compatible with both the existence...

  18. Gas and dust in the star-forming region rho Oph A: The dust opacity exponent beta and the gas-to-dust mass ratio g2d

    CERN Document Server

    Liseau, R; Lunttila, T; Olberg, M; Rydbeck, G; Bergman, P; Justtanont, K; Olofsson, G; de Vries, B L

    2015-01-01

    We aim at determining the spatial distribution of the gas and dust in star-forming regions and address their relative abundances in quantitative terms. We also examine the dust opacity exponent beta for spatial and/or temporal variations. Using mapping observations of the very dense rho Oph A core, we examined standard 1D and non-standard 3D methods to analyse data of far-infrared and submillimeter (submm) continuum radiation. The resulting dust surface density distribution can be compared to that of the gas. The latter was derived from the analysis of accompanying molecular line emission, observed with Herschel from space and with APEX from the ground. As a gas tracer we used N2H+, which is believed to be much less sensitive to freeze-out than CO and its isotopologues. Radiative transfer modelling of the N2H+(J=3-2) and (J=6-5) lines with their hyperfine structure explicitly taken into account provides solutions for the spatial distribution of the column density N(H2), hence the surface density distribution ...

  19. The Banana Project. III. Spin-orbit Alignment in the Long-period Eclipsing Binary NY Cephei

    CERN Document Server

    Albrecht, Simon; Carter, Joshua; Snellen, Ignas; de Mooij, Ernst

    2010-01-01

    Binaries are not always neatly aligned. Previous observations of the DI Her system showed that the spin axes of both stars are highly inclined with respect to one another and the orbital axis. Here we report on a measurement of the spin-axis orientation of the primary star of the NY Cep system, which is similar to DI Her in many respects: it features two young early-type stars (~6 Myr, B0.5V+B2V), in an eccentric and relatively long-period orbit (e=0.48, P=15.d3). The sky projections of the rotation vector and the spin vector are well-aligned (beta_p = 2 +- 4 degrees), in strong contrast to DI Her. Although no convincing explanation has yet been given for the misalignment of DI Her, our results show that the phenomenon is not universal, and that a successful theory will need to account for the different outcome in the case of NY Cep.

  20. Learning from Pulsating Stars: Progress over the Last Century (Abstract)

    Science.gov (United States)

    Smith, H.

    2016-12-01

    (Abstract only) Scarcely more than a century has elapsed since it began to be widely accepted that pulsation plays an important role in the variability of stars. During that century pulsating stars have been used as tools to explore a variety of astrophysical questions, including the determination of distances to other galaxies, the testing of timescales of evolution through the HR diagram, and the identification of the ages and star formation histories of stellar populations. Among the significant early milestones along this investigative path are Henrietta Leavitt's discovery of a relation between the periods and luminosities of Cepheids, Harlow Shapley's proposal that all Cepheids are pulsating stars, and Arthur Stanley Eddington's use of the observed period change of d Cephei to constrain its power source. Today our explorations of pulsating stars are bolstered by long observational histories of brighter variables, surveys involving unprecedentedly large numbers of stars, and improved theoretical analyses. This talk will review aspects of the history and our current understanding of pulsating stars, paying particular attention to RR Lyrae, d Scuti, and Cepheid variables. Observations by AAVSO members have provided insight into several questions regarding the behavior of these stars.

  1. Kepler observations of the variability in B-type stars

    DEFF Research Database (Denmark)

    Balona, Luis A.; Pigulski, A.; De Cat, P.

    2011-01-01

    variations in other stars which we attribute to proximity effects in binary systems or possibly rotational modulation. We find no evidence for pulsating stars between the cool edge of the SPB and the hot edge of the δ Sct instability strips. None of the stars shows the broad features which can be attributed......The analysis of the light curves of 48 B-type stars observed by Kepler is presented. Among these are 15 pulsating stars, all of which show low frequencies, characteristic of slowly pulsating B (SPB) stars. Seven of these stars also show a few weak, isolated high frequencies and they could...... be considered as SPB/β Cephei (β Cep) hybrids. In all cases, the frequency spectra are quite different from what is seen from ground-based observations. We suggest that this is because most of the low frequencies are modes of high degree which are predicted to be unstable in models of mid-B stars. We find...

  2. Long-Term Photometric Behavior of the Eclipsing Binary GW Cephei

    Science.gov (United States)

    Lee, Jae Woo; Youn, Jae-Hyuck; Han, Wonyong; Lee, Chung-Uk; Kim, Seung-Lee; Kim, Ho-Il; Park, Jang-Ho; Koch, Robert H.

    2010-03-01

    New CCD photometry over four successive years from 2005 is presented for the eclipsing binary GW Cep, together with reasonable explanations for the light and period variations. All historical light curves, obtained over a 30 yr interval, display striking light changes, and are best modeled by the simultaneous existence of a cool spot and a hot spot on the more massive cool component star. The facts that the system is magnetically active and that the hot spot has consistently existed on the inner hemisphere of the star indicate that the two spots are formed by (1) magnetic dynamo-related activity on the cool star and (2) mass transfer from the primary to the secondary component. Based on 38 light-curve timings from the Wilson-Devinney code and all other minimum epochs, a period study of GW Cep reveals that the orbital period has experienced a sinusoidal variation with a period and semi-amplitude of 32.6 yr and 0.009 days, respectively. In principle, these may be produced either by a light-travel-time effect due to a third body or by an active magnetic cycle of at least one component star. Because we failed to find any connection between luminosity variability and the period change, that change most likely arises from the existence of an unseen third companion star with a minimum mass of 0.22 M sun gravitationally bound to the eclipsing pair.

  3. Astrometry with Hubble Space Telescope A Parallax of the Fundamental Distance Calibrator delta Cephei

    CERN Document Server

    Benedict, G F; Fredrick, L W; Harrison, T E; Slesnick, C L; Rhee, J; Patterson, R J; Skrutskie, M F; Franz, O G; Wasserman, L H; Jefferys, W H; Nelan, E; Van Altena, W; Shelus, P J; Hemenway, P D; Duncombe, R L; Story, D; Whipple, A L; Bradley, A J

    2002-01-01

    We present an absolute parallax and relative proper motion for the fundamental distance scale calibrator, delta Cep. We obtain these with astrometric data from FGS 3, a white-light interferometer on HST. Utilizing spectrophotometric estimates of the absolute parallaxes of our astrometric reference stars and constraining delta Cep and reference star HD 213307 to belong to the same association (Cep OB6, de Zeeuw et al. 1999), we find pi_{abs} = 3.66 +/- 0.15 mas. The larger than typical astrometric residuals for the nearby astrometric reference star HD 213307 are found to satisfy Keplerian motion with P = 1.07 +/- 0.02 years, a perturbation and period that could be due to a F0V companion ~7 mas distant from and ~4 magnitudes fainter than the primary. Spectral classifications and VRIJHKT$_2$M and DDO51 photometry of the astrometric reference frame surrounding delta Cep indicate that field extinction is high and variable along this line of sight. However the extinction suffered by the reference star nearest (in a...

  4. On X-ray pulsations in β Cephei-type variables

    Science.gov (United States)

    Oskinova, L. M.; Todt, H.; Huenemoerder, D. P.; Hubrig, S.; Ignace, R.; Hamann, W.-R.; Balona, L.

    2015-05-01

    Context. β Cep-type variables are early B-type stars that are characterized by oscillations observable in their optical light curves. At least one β Cep-variable also shows periodic variability in X-rays. Aims: Here we study the X-ray light curves in a sample of β Cep-variables to investigate how common X-ray pulsations are for this type of stars. Methods: We searched the Chandra and XMM-Newton X-ray archives and selected stars that were observed by these telescopes for at least three optical pulsational periods. We retrieved and analyzed the X-ray data for κ Sco, β Cru, and α Vir. The X-ray light curves of these objects were studied to test for their variability and periodicity. Results: While there is a weak indication for X-ray variability in β Cru, we find no statistically significant evidence of X-ray pulsations in any of our sample stars. This might be due either to the insufficient data quality or to the physical lack of modulations. New, more sensitive observations should settle this question. The scientific results reported in this article are based on observations made by the Chandra and XMM-Newton X-ray Observatories, data obtained from the Chandra and XMM-Newton Data Archives, and observations made by the Chandra and XMM-Newton and published previously in cited articles.

  5. Time-series spectroscopy of the pulsating eclipsing binary XX Cephei

    CERN Document Server

    Koo, Jae-Rim; Hong, Kyeongsoo; Kim, Seung-Lee; Lee, Chung-Uk

    2016-01-01

    Oscillating Algol-type eclipsing binaries (oEA) are very interesting objects that have three observational features of eclipse, pulsation, and mass transfer. Direct measurement of their masses and radii from the double-lined radial velocity data and photometric light curves would be the most essential for understanding their evolutionary process and for performing the asteroseismological study. We present the physical properties of the oEA star XX Cep from high-resolution time-series spectroscopic data. The effective temperature of the primary star was determined to be 7,946 $\\pm$ 240 K by comparing the observed spectra and the Kurucz models. We detected the absorption lines of the secondary star, which had never been detected in previous studies, and obtained the radial velocities for both components. With the published $BVRI$ light curves, we determined the absolute parameters for the binary via Wilson-Devinney modeling. The masses and radii are $M_{1} = 2.49 \\pm 0.06$ $M_\\odot$, $M_{2} = 0.38 \\pm 0.01$ $M_...

  6. Long-term Photometric Behavior of the Eclipsing Binary GW Cephei

    CERN Document Server

    Lee, Jae Woo; Han, Wonyong; Lee, Chung-Uk; Kim, Seung-Lee; Kim, Ho-Il; Park, Jang-Ho; Koch, Robert H

    2009-01-01

    New CCD photometry during 4 successive years from 2005 is presented for the eclipsing binary GW Cep, together with reasonable explanations for the light and period variations. All historical light curves, obtained over a 30-year interval, display striking light changes, and are best modeled by the simultaneous existence of a cool spot and a hot spot on the more massive cool component star. The facts that the system is magnetically active and that the hot spot has consistently existed on the inner hemisphere of the star indicate that the two spots are formed by (1) magnetic dynamo-related activity on the cool star and (2) mass transfer from the primary to the secondary component. Based on 38 light-curve timings from the Wilson-Devinney code and all other minimum epochs, a period study of GW Cep reveals that the orbital period has experienced a sinusoidal variation with a period and semi-amplitude of 32.6 yrs and 0.009 d, respectively. In principle, these may be produced either by a light-travel-time effect due...

  7. PLANET FORMATION IN STELLAR BINARIES. II. OVERCOMING THE FRAGMENTATION BARRIER IN α CENTAURI AND γ CEPHEI-LIKE SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Rafikov, Roman R.; Silsbee, Kedron, E-mail: rrr@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Ivy Lane, Princeton, NJ 08540 (United States)

    2015-01-10

    Planet formation in small-separation (∼20 AU) eccentric binaries such as γ Cephei or α Centauri is believed to be adversely affected by the presence of the stellar companion. Strong dynamical excitation of planetesimals by the eccentric companion can result in collisional destruction (rather than growth) of 1-100 km objects, giving rise to the ''fragmentation barrier'' for planet formation. We revise this issue using a novel description of secular dynamics of planetesimals in binaries, which accounts for the gravity of the eccentric, coplanar protoplanetary disk, as well as gas drag. By studying planetesimal collision outcomes, we show, in contrast to many previous studies, that planetesimal growth and subsequent formation of planets (including gas giants) in AU-scale orbits within ∼20 AU separation binaries may be possible, provided that the protoplanetary disks are massive (≳ 10{sup –2} M {sub ☉}) and only weakly eccentric (disk eccentricity ≲ 0.01). These requirements are compatible with both the existence of massive (several M{sub J} ) planets in γ Cep-like systems and the results of recent simulations of gaseous disks in eccentric binaries. Terrestrial and Neptune-like planets can also form in lower-mass disks at small (sub-AU) radii. We find that the fragmentation barrier is less of a problem in eccentric disks that are apsidally aligned with the binary orbit. Alignment gives rise to special locations, where (1) relative planetesimal velocities are low and (2) the timescale of their drag-induced radial drift is long. This causes planetesimal pileup at such locations in the disk and promotes their growth locally, helping to alleviate the timescale problem for core formation.

  8. New Evidence Supporting Cluster Membership for the Keystone Calibrator Delta Cephei

    CERN Document Server

    Majaess, Daniel J; Gieren, Wolfgang

    2012-01-01

    New and existing UBVJHKs, spectroscopic, NOMAD, HST, and revised HIP observations are employed to determine properties for delta Cep and its host star cluster. The multi-faceted approach ensured that uncertainties were mitigated (~2%). The following fundamental parameters were inferred for delta Cep: E(B-V)=0.073+-0.018, log(t)=7.9+-0.1, and d=272+-3(se)+-5(sd) pc. The cluster exhibits a turnoff near B6 (M*/Ms~5), and the brightest host cluster members are the supergiants zeta Cep (K1.5Ib) and delta Cep. To within the uncertainties, the two stars share common astrometric parameters (pi, mu_ra, mu_dec, RV\\sim-17 km/s) and are tied to bluer members via the evolutionary track implied by the cluster's UBVJHKs color-color and color-magnitude diagrams. The cluster's existence is bolstered by the absence of an early-type sequence in color-magnitude diagrams for comparison fields. NOMAD data provided a means to identify potential cluster members (n~30) and double the existing sample. That number could increase with f...

  9. Can there be additional rocky planets in the Habitable Zone of tight binary stars with a known gas giant?

    CERN Document Server

    Funk, Barbara; Eggl, Siegfried

    2015-01-01

    Locating planets in HabitableZones (HZs) around other stars is a growing field in contemporary astronomy. Since a large percentage of all G-M stars in the solar neighbourhood are expected to be part of binary or multiple stellar systems, investigations of whether habitable planets are likely to be discovered in such environments are of prime interest to the scientific community. As current exoplanet statistics predicts that the chances are higher to find new worlds in systems that are already known to have planets, we examine four known extrasolar planetary systems in tight binaries in order to determine their capacity to host additional habitable terrestrial planets. Those systems are Gliese 86, gamma Cephei, HD 41004 and HD 196885. In the case of gamma Cephei, our results suggest that only the M dwarf companion could host additional potentially habitable worlds. Neither could we identify stable, potentially habitable regions around HD 196885 A. HD 196885 B can be considered a slightly more promising target ...

  10. Beta Thalassemia

    Science.gov (United States)

    Beta thalassemia is found in people of Mediterranean, Middle Eastern, African, South Asian (Indian, Pakistani, etc.), Southeast Asian and Chinese descent. 1 Beta Thalassemia ßß Normal beta globin genes found on chromosomes ...

  11. IUE spectroscopy of U Cephei during the mass flow outburst of 1986 June

    Science.gov (United States)

    Mccluskey, George E., Jr.; Kondo, Yoji; Olson, Edward C.

    1988-01-01

    The interacting Algol-type binary U Cep underwent another of its irregularly occurring transient high-mass flow events during June 1986. For the first time, high-resolution ultraviolet spectroscopy of U Cep during such an event was possible. High-resolution spectra in the far-ultraviolet and near-ultraviolet were obtained with IUE. These spectra show that the ultraviolet continuum decreased by factors of 1.2 to 3.0 during the greatest activity. In addition, one or more narrow absorption components with radial velocities as high as -500 km/s appeared in association with a number of C, Si, Al, Fe, Zn, and Mg lines. The Mg II doublet developed a flat-bottomed appearance with a residual intensity of about 0.31 and a width of at least 800 km/s. These phenomena are interpreted in terms of high-velocity gas streams, mass loss from the system, and the formation of an optically thick equatorial bulge around the B star.

  12. Mean-field study of hot beta-stable protoneutron star matter: Impact of the symmetry energy and nucleon effective mass

    CERN Document Server

    Tan, Ngo Hai; Khoa, Dao T; Margueron, Jerome

    2016-01-01

    A consistent Hartree-Fock study of the equation of state (EOS) of asymmetric nuclear matter at finite temperature has been performed using realistic choices of the effective, density dependent nucleon-nucleon (NN) interaction, which were successfully used in different nuclear structure and reaction studies. Given the importance of the nuclear symmetry energy in the neutron star formation, EOS's associated with different behaviors of the symmetry energy were used to study hot asymmetric nuclear matter. The slope of the symmetry energy and nucleon effective mass with increasing baryon density was found to affect the thermal properties of nuclear matter significantly. Different density dependent NN interactions were further used to study the EOS of hot protoneutron star (PNS) matter of the $npe\\mu\

  13. Variable Stars Observed in the Galactic Disk by AST3-1 from Dome A, Antarctica

    Science.gov (United States)

    Wang, Lingzhi; Ma, Bin; Li, Gang; Hu, Yi; Fu, Jianning; Wang, Lifan; Ashley, Michael C. B.; Cui, Xiangqun; Du, Fujia; Gong, Xuefei; Li, Xiaoyan; Li, Zhengyang; Liu, Qiang; Pennypacker, Carl R.; Shang, Zhaohui; Yuan, Xiangyan; York, Donald G.; Zhou, Jilin

    2017-03-01

    AST3-1 is the second-generation wide-field optical photometric telescope dedicated to time-domain astronomy at Dome A, Antarctica. Here, we present the results of an i-band images survey from AST3-1 toward one Galactic disk field. Based on time-series photometry of 92,583 stars, 560 variable stars were detected with i magnitude ≤16.5 mag during eight days of observations; 339 of these are previously unknown variables. We tentatively classify the 560 variables as 285 eclipsing binaries (EW, EB, and EA), 27 pulsating variable stars (δ Scuti, γ Doradus, δ Cephei variable, and RR Lyrae stars), and 248 other types of variables (unclassified periodic, multiperiodic, and aperiodic variable stars). Of the eclipsing binaries, 34 show O’Connell effects. One of the aperiodic variables shows a plateau light curve and another variable shows a secondary maximum after peak brightness. We also detected a complex binary system with an RS CVn-like light-curve morphology; this object is being followed-up spectroscopically using the Gemini South telescope.

  14. Pulsating Star Mystery Solved

    Science.gov (United States)

    2010-11-01

    outcome of this work, and the team hopes to find other examples of these remarkably useful pairs of stars to exploit the method further. They also believe that from such binary systems they will eventually be able to pin down the distance to the Large Magellanic Cloud to 1%, which would mean an extremely important improvement of the cosmic distance scale. Notes [1] The first Cepheid variables were spotted in the 18th century and the brightest ones can easily be seen to vary from night to night with the unaided eye. They take their name from the star Delta Cephei in the constellation of Cepheus (the King), which was first seen to vary by John Goodricke in England in 1784. Remarkably, Goodricke was also the first to explain the light variations of another kind of variable star, eclipsing binaries. In this case two stars are in orbit around each other and pass in front of each other for part of their orbits and so the total brightness of the pair drops. The very rare object studied by the current team is both a Cepheid and an eclipsing binary. Classical Cepheids are massive stars, distinct from similar pulsating stars of lower mass that do not share the same evolutionary history. [2] The period luminosity relation for Cepheids, discovered by Henrietta Leavitt in 1908, was used by Edwin Hubble to make the first estimates of the distance to what we now know to be galaxies. More recently Cepheids have been observed with the Hubble Space Telescope and with the ESO VLT on Paranal to make highly accurate distance estimates to many nearby galaxies. [3] In particular, astronomers can determine the masses of the stars to high accuracy if both stars happen to have a similar brightness and therefore the spectral lines belonging to each of the two stars can be seen in the observed spectrum of the two stars together, as is the case for this object. This allows the accurate measurement of the motions of both stars towards and away from Earth as they orbit, using the Doppler effect. [4

  15. The Classificiation of Kepler B star Variables

    CERN Document Server

    McNamara, Bernard J; McKeever, Jean

    2012-01-01

    The light curves of 252 B-star candidates in the Kepler data base are analyzed in a similar fashion to that done by Balona et al. (2011) to further characterize B star variability, increase the sample of variable B stars for future study, and to identify stars whose power spectra include particularly interesting features such as frequency groupings. Stars are classified as either constant light emitters, $\\beta$ Cep stars, slowly pulsating B stars, hybrid pulsators, binaries or stars whose light curves are dominated by rotation (Bin/Rot), hot subdwarfs, or white dwarfs. One-hundred stars in our sample were found to be either light contants or to be variable at a level of less than 0.02 mmag. We increase the number of candidate B-star variables found in the Kepler data base by Balona et al. (2011) in the following fashion: $\\beta$ Cep stars from 0 to 10, slowly pulsating B stars from 8 to 54, hybrid pulsators from 7 to 21, and Bin/Rot stars from 23 to 82. For comparison purposes, approximately 51 SPBs and 6 hy...

  16. Star Clusters

    OpenAIRE

    Gieles, M.

    1993-01-01

    Star clusters are observed in almost every galaxy. In this thesis we address several fundamental problems concerning the formation, evolution and disruption of star clusters. From observations of (young) star clusters in the interacting galaxy M51, we found that clusters are formed in complexes of stars and star clusters. These complexes share similar properties with giant molecular clouds, from which they are formed. Many (70%) of the young clusters will not survive the fist 10 Myr, due to t...

  17. Stars and Star Myths.

    Science.gov (United States)

    Eason, Oliver

    Myths and tales from around the world about constellations and facts about stars in the constellations are presented. Most of the stories are from Greek and Roman mythology; however, a few Chinese, Japanese, Polynesian, Arabian, Jewish, and American Indian tales are also included. Following an introduction, myths are presented for the following 32…

  18. Wave Star

    DEFF Research Database (Denmark)

    Kramer, Morten; Brorsen, Michael; Frigaard, Peter

    Denne rapport beskriver numeriske beregninger af forskellige flydergeometrier for bølgeenergianlæget Wave Star.......Denne rapport beskriver numeriske beregninger af forskellige flydergeometrier for bølgeenergianlæget Wave Star....

  19. Massive Stars

    Science.gov (United States)

    Livio, Mario; Villaver, Eva

    2009-11-01

    Participants; Preface Mario Livio and Eva Villaver; 1. High-mass star formation by gravitational collapse of massive cores M. R. Krumholz; 2. Observations of massive star formation N. A. Patel; 3. Massive star formation in the Galactic center D. F. Figer; 4. An X-ray tour of massive star-forming regions with Chandra L. K. Townsley; 5. Massive stars: feedback effects in the local universe M. S. Oey and C. J. Clarke; 6. The initial mass function in clusters B. G. Elmegreen; 7. Massive stars and star clusters in the Antennae galaxies B. C. Whitmore; 8. On the binarity of Eta Carinae T. R. Gull; 9. Parameters and winds of hot massive stars R. P. Kudritzki and M. A. Urbaneja; 10. Unraveling the Galaxy to find the first stars J. Tumlinson; 11. Optically observable zero-age main-sequence O stars N. R. Walborn; 12. Metallicity-dependent Wolf-Raynet winds P. A. Crowther; 13. Eruptive mass loss in very massive stars and Population III stars N. Smith; 14. From progenitor to afterlife R. A. Chevalier; 15. Pair-production supernovae: theory and observation E. Scannapieco; 16. Cosmic infrared background and Population III: an overview A. Kashlinsky.

  20. Hadron star models. [neutron stars

    Science.gov (United States)

    Cohen, J. M.; Boerner, G.

    1974-01-01

    The properties of fully relativistic rotating hadron star models are discussed using models based on recently developed equations of state. All of these stable neutron star models are bound with binding energies as high as about 25%. During hadron star formation, much of this energy will be released. The consequences, resulting from the release of this energy, are examined.

  1. On the nature of the {delta} Scuti star HD 115520

    Energy Technology Data Exchange (ETDEWEB)

    Pena, J H; Cervantes-Sodi, B; Cano, M; Sorcia, M A [Instituto de AstronomIa, Universidad Nacional Autonoma de Mexico, Mexico D.F., Apdo. Postal 70-264 (Mexico); Fox, L; Alvarez, M [Observatorio Astronomico Nacional, Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Ensenada B.C., Apdo. Postal 877 (Mexico); Pena, R [Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Mexico D.F. (Mexico); Munoz, G; Vargas, B [Escuela Superior de Ingenier Mecanica y Electrica, Instituto Politecnico Nacional, Av. IPN s/n, 07738 Mexico, D.F. (Mexico); Sareyan, J P [Observatoire de la Cote d' Azur (France)], E-mail: jhpena@astroscu.unam.mx

    2008-10-15

    Observing Delta Scuti stars is most important as their multi-frequency spectrum of radial pulsations provide strong constraints on the physics of the stars interior; so any new detection and observation of these stars is a valuable contribution to asteroseismology. While performing uvby-beta photoelectric photometry of some RR Lyrae stars acquired in 2005 at the Observatorio Astronomico Nacional, Mexico, we also observed several standard stars, HD115520 among them. After the reduction this star showed indications of variability. In view of this, a new observing run was carried out in 2006 during which we were able to demonstrate its variability and its nature as a Delta Scuti star. New observations in 2007 permitted us to determine its periodic content with more accuracy. This, along with the uvby-beta photoelectric photometry allowed us to deduce its physical characteristics and pulsational modes.

  2. Star Wreck

    OpenAIRE

    Kusenko, Alexander; Shaposhnikov, Mikhail E.; Tinyakov, P. G.; Tkachev, Igor I.

    1998-01-01

    Electroweak models with low-energy supersymmetry breaking predict the existence of stable non-topological solitons, Q-balls, that can be produced in the early universe. The relic Q-balls can accumulate inside a neutron star and gradually absorb the baryons into the scalar condensate. This causes a slow reduction in the mass of the star. When the mass reaches a critical value, the neutron star becomes unstable and explodes. The cataclysmic destruction of the distant neutron stars may be the or...

  3. Star polygons

    OpenAIRE

    Riosa, Blažka

    2014-01-01

    In mathematics we often encounter polygons, such us triangle, square, hexagon, etc., but we hardly encounter star polygons. Despite the fact that we do not meet them so often in mathematics, in nature they can be traced almost on every step. In this paper the emphasis is on the geometric meaning of regular star polygons. Star polygon is a generalization of the concept of regular polygons. In star polygons also non-adjacent sides intersect. Up to similarity they are determined by Schläfli symb...

  4. Chromospheric changes in K stars with activity

    CERN Document Server

    Vieytes, Mariela; Diaz, Rodrigo

    2009-01-01

    We study the differences in chromospheric structure induced in K stars by stellar activity, to expand our previous work for G stars, including the Sun as a star. We selected six stars of spectral type K with 0.82$stars in the sample, in most cases in two different moments of activity. The models were constructed to obtain the best possible match with the Ca II K and the H$\\beta$ observed profiles. We also computed in detail the net radiative losses for each model to constrain the heating mechanism that can maintain the structure in the atmosphere. We find a strong correlation between these losses and \\Sc, the index generally used as a proxy for activity, as we found for G stars.

  5. STAR Calorimetry

    Energy Technology Data Exchange (ETDEWEB)

    Jacobs, W W, E-mail: jacobsw@indiana.ed [Indiana University Cyclotron Facility and Department of Physics, 2401 Milo B. Sampson Lane, Bloomington IN 47408 (United States)

    2009-04-01

    The main STAR calorimeters comprise a full Barrel EMC and single Endcap EMC plus a Forward Meson Spectrometer. Together they give a nearly complete coverage over the range -1 < pseudorapidity < 4 and provide EM readout and triggering that help drive STAR physics capabilities. Their description, status, performance and operations (and a few physics anecdotes) are briefly presented and discussed.

  6. Wave Star

    DEFF Research Database (Denmark)

    Kramer, Morten; Brorsen, Michael; Frigaard, Peter

    Nærværende rapport beskriver numeriske beregninger af den hydrodynamiske interaktion mellem 5 flydere i bølgeenergianlægget Wave Star.......Nærværende rapport beskriver numeriske beregninger af den hydrodynamiske interaktion mellem 5 flydere i bølgeenergianlægget Wave Star....

  7. Star Imager

    DEFF Research Database (Denmark)

    Madsen, Peter Buch; Jørgensen, John Leif; Thuesen, Gøsta;

    1997-01-01

    The version of the star imager developed for Astrid II is described. All functions and features are described as well as the operations and the software protocol.......The version of the star imager developed for Astrid II is described. All functions and features are described as well as the operations and the software protocol....

  8. Planetary companions in K giants beta Cancri, mu Leonis, and beta Ursae Minoris

    CERN Document Server

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

    2014-01-01

    Auns. The aim of our paper is to investigate the low-amplitude and long-period variations in evolved stars with a precise radial velocity (RV) survey. Methods. The high-resolution, the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) was used from 2003 to 2013 for a radial velocity survey of giant stars as part of the exoplanet search program at Bohyunsan Optical Astronomy Observatory (BOAO). Results. We report the detection of three new planetary companions orbiting the K giants beta Cnc, mu Leo, and beta UMi. The planetary nature of the radial velocity variations is supported by analyzes of ancillary data. The HIPPARCOS photometry shows no variations with periods close to those in RV variations and there is no strong correlation between the bisector velocity span (BVS) and the radial velocities for each star. Furthermore, the stars show weak or no core reversal in Ca II H lines indicating that they are inactive stars. The companion to beta Cnc has a minimum mass of 7.8 M_Jup in a 605-day orbit wi...

  9. Magnetic fields of neutron stars

    CERN Document Server

    Reisenegger, Andreas

    2013-01-01

    Neutron stars contain the strongest magnetic fields known in the Universe. In this paper, I discuss briefly how these magnetic fields are inferred from observations, as well as the evidence for their time-evolution. I show how these extremely strong fields are actually weak in terms of their effects on the stellar structure, as is also the case for magnetic stars on the upper main sequence and magnetic white dwarfs, which have similar total magnetic fluxes. I propose a scenario in which a stable hydromagnetic equilibrium (containing a poloidal and a toroidal field component) is established soon after the birth of the neutron star, aided by the strong compositional stratification of neutron star matter, and this state is slowly eroded by non-ideal magnetohydrodynamic processes such as beta decays and ambipolar diffusion in the core of the star and Hall drift and breaking of the solid in its crust. Over sufficiently long time scales, the fluid in the neutron star core will behave as if it were barotropic, becau...

  10. Rising Star

    OpenAIRE

    Worley, Christiana

    2012-01-01

    Rising Star is a novel about appearances. Thailand Allen is a girl who thinks she understands what she sees. But when what she sees are cracks in her perfect world, maturation and new sight are not far off. Before growth can occur, Thailand must undergo a painful process of learning that carries with it embarrassment, sorrow, anger and confusion. Thailand lives with her mother in a small Texas town called Rising Star. Rising Star is like every other small town with its community gather...

  11. Carbon Stars

    Indian Academy of Sciences (India)

    T. Lloyd Evans

    2010-12-01

    In this paper, the present state of knowledge of the carbon stars is discussed. Particular attention is given to issues of classification, evolution, variability, populations in our own and other galaxies, and circumstellar material.

  12. Rock Stars

    Institute of Scientific and Technical Information of China (English)

    张国平

    2000-01-01

    Around the world young people are spending unbelievable sums of money to listen to rock music. Forbes Magazine reports that at least fifty rock stars have incomes between two million and six million dollars per year.

  13. Hyperon Stars in Strong Magnetic Fields

    CERN Document Server

    Gomes, R O; Vasconcellos, C A Z

    2013-01-01

    We investigate the effects of strong magnetic fields on the properties of hyperon stars. The matter is described by a hadronic model with parametric coupling. The matter is considered to be at zero temperature, charge neutral, beta-equilibrated, containing the baryonic octet, electrons and muons. The charged particles have their orbital motions Landau-quantized in the presence of strong magnetic fields (SMF). Two parametrisations of a chemical potential dependent static magnetic field are considered, reaching $1-2 \\times 10^{18}\\,G$ in the center of the star. Finally, the Tolman-Oppenheimer-Volkov (TOV) equations are solved to obtain the mass-radius relation and population of the stars.

  14. Wave Star

    DEFF Research Database (Denmark)

    Kramer, Morten; Frigaard, Peter

    Nærværende rapport beskriver modelforsøg udført på Aalborg Universitet, Institut for Byggeri og Anlæg med bølgeenergianlæget Wave Star.......Nærværende rapport beskriver modelforsøg udført på Aalborg Universitet, Institut for Byggeri og Anlæg med bølgeenergianlæget Wave Star....

  15. STAR POLYMERS

    OpenAIRE

    Ch. von Ferber; Yu.Holovatch

    2002-01-01

    It is our great pleasure to present a collection of papers devoted to theoretical, numerical, and experimental studies in the field of star polymers. Since its introduction in the early 80-ies, this field has attracted increasing interest and has become an important part of contemporary polymer physics. While research papers in this field appear regularly in different physical and chemical journals, the present collection is an attempt to join together the studies of star polymers showing the...

  16. Wave Star

    DEFF Research Database (Denmark)

    Kramer, Morten; Andersen, Thomas Lykke

    Nærværende rapport beskriver modelforsøg udført på Aalborg Universitet, Institut for Vand, Jord og Miljøteknik med bølgeenergianlægget Wave Star.......Nærværende rapport beskriver modelforsøg udført på Aalborg Universitet, Institut for Vand, Jord og Miljøteknik med bølgeenergianlægget Wave Star....

  17. Detailed Opacity Comparison for an Improved Stellar Modeling of the Envelopes of Massive Stars

    Science.gov (United States)

    Turck-Chièze, S.; Le Pennec, M.; Ducret, J. E.; Colgan, J.; Kilcrease, D. P.; Fontes, C. J.; Magee, N.; Gilleron, F.; Pain, J. C.

    2016-06-01

    Seismic observations have led to doubts or ambiguities concerning the opacity calculations used in stellar physics. Here, we concentrate on the iron-group opacity peak, due to iron, nickel, and chromium, located around T = 200,000 K for densities from {10}-8 {to} {10}-4 {{g}} {{cm}}-3, which creates some convective layers in stellar radiative envelopes for masses between 3 and 18 {M}⊙ . These conditions were extensively studied in the 1980s. More recently, inconsistencies between OP and OPAL opacity calculations have complicated the interpretation of seismic observations as the iron-group opacity peak excites acoustic and gravity modes in SPB, β Cephei, and sdB stars. We investigate the reliability of the theoretical opacity calculations using the modern opacity codes ATOMIC and SCO-RCG. We show their temperature and density dependence for conditions that are achievable in the laboratory and equivalent to astrophysical conditions. We also compare new theoretical opacity spectra with OP spectra and quantify how different approximations impact the Rosseland mean calculations.This detailed study estimates new ATOMIC and SCO-RCG Rosseland mean values for astrophysical conditions which we compare to OP values. Some puzzling questions are still under investigation for iron, but we find a strong increase in the Rosseland mean nickel opacity of a factor between 2 and 6 compared to OP. This appears to be due to the use of extrapolated atomic data for the Ni opacity within the OP calculations. A study on chromium is also shown.

  18. Morning Star

    OpenAIRE

    Harris, Mark

    2010-01-01

    Morning Star comprises a group of paintings and drawings whose imagery derives from photographs of 1960s American hippie communes. The paintings are made using oil paint on linen. Their dimensions vary between 180 x 120, and 228 x 217 centimetres. The drawings are in pencil on watercolour paper and are all 56 x 76 centimetres. The work has been exhibited in conventional form, hanging on gallery walls. For Morning Star I made pencil drawings and oil paintings derived from images in Dick Fa...

  19. Beta-carotene

    Science.gov (United States)

    ... patches on the tongue and mouth called oral leukoplakia. Taking beta-carotene by mouth for up to 12 months seems to decrease symptoms of oral leukoplakia. Osteoarthritis. Beta-carotene taken by mouth may prevent ...

  20. Stars Underground

    CERN Multimedia

    Jean Leyder

    1996-01-01

    An imaginary voyage in time where we were witness of the birth of the universe itself, the time of the Big-Bang 15 billion years ago. Particules from the very first moments of time : protons, neutrons and electrons, and also much more energetic one. These particules are preparing to interact collider and generating others which will be the birth to the stars ........

  1. Pulsating stars

    CERN Document Server

    Catelan, M?rcio

    2014-01-01

    The most recent and comprehensive book on pulsating stars which ties the observations to our present understanding of stellar pulsation and evolution theory.  Written by experienced researchers and authors in the field, this book includes the latest observational results and is valuable reading for astronomers, graduate students, nuclear physicists and high energy physicists.

  2. STAR Highlights

    OpenAIRE

    Masui, Hiroshi; collaboration, for the STAR

    2011-01-01

    We report selected results from STAR collaboration at RHIC, focusing on jet-hadron and jet-like correlations, quarkonium suppression and collectivity, di-electron spectrum in both p+p and Au+Au, and higher moments of net-protons as well as azimuthal anisotropy from RHIC Beam Energy Scan program.

  3. Forward-Looking Betas

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Jacobs, Kris; Vainberg, Gregory

    Few issues are more important for finance practice than the computation of market betas. Existing approaches compute market betas using historical data. While these approaches differ in terms of statistical sophistication and the modeling of the time-variation in the betas, they are all backward......-looking. This paper introduces a radically different approach to estimating market betas. Using the tools in Bakshi and Madan (2000) and Bakshi, Kapadia and Madan (2003) we employ the information embedded in the prices of individual stock options and index options to compute our forward-looking market beta...

  4. Wave Star

    DEFF Research Database (Denmark)

    Kramer, Morten; Frigaard, Peter; Brorsen, Michael

    Nærværende rapport beskriver foreløbige hovedkonklusioner på modelforsøg udført på Aalborg Universitet, Institut for Vand, Jord og Miljøteknik med bølgeenergianlægget Wave Star i perioden 13/9 2004 til 12/11 2004.......Nærværende rapport beskriver foreløbige hovedkonklusioner på modelforsøg udført på Aalborg Universitet, Institut for Vand, Jord og Miljøteknik med bølgeenergianlægget Wave Star i perioden 13/9 2004 til 12/11 2004....

  5. Planck stars

    CERN Document Server

    Rovelli, Carlo

    2014-01-01

    A star that collapses gravitationally can reach a further stage of its life, where quantum-gravitational pressure counteracts weight. The duration of this stage is very short in the star proper time, yielding a bounce, but extremely long seen from the outside, because of the huge gravitational time dilation. Since the onset of quantum-gravitational effects is governed by energy density --not by size-- the star can be much larger than planckian in this phase. The object emerging at the end of the Hawking evaporation of a black hole can can then be larger than planckian by a factor $(m/m_{\\scriptscriptstyle P})^n$, where $m$ is the mass fallen into the hole, $m_{\\scriptscriptstyle P}$ is the Planck mass, and $n$ is positive. The existence of these objects alleviates the black-hole information paradox. More interestingly, these objects could have astrophysical and cosmological interest: they produce a detectable signal, of quantum gravitational origin, around the $10^{-14} cm$ wavelength.

  6. The hot Gamma-Doradus and Maia stars

    CERN Document Server

    Balona, L A; Joshi, Yogesh C; Joshi, S; Sharma, K; Semenko, E; Pandey, G; Chakradhari, N K; Mkrtichian, David; Hema, B P; Nemec, J M

    2016-01-01

    The hot $\\gamma$~Doradus stars have multiple low frequencies characteristic of $\\gamma$~Dor or SPB variables, but are located between the red edge of the SPB and the blue edge of the $\\gamma$~Dor instability strips where all low-frequency modes are stable in current models of these stars. Though $\\delta$~Sct stars also have low frequencies, there is no sign of high frequencies in hot $\\gamma$~Dor stars. We obtained spectra to refine the locations of some of these stars in the H-R diagram and conclude that these are, indeed, anomalous pulsating stars. The Maia variables have multiple high frequencies characteristic of $\\beta$~Cep and $\\delta$~Sct stars, but lie between the red edge of the $\\beta$~Cep and the blue edge of the $\\delta$~Sct instability strips. We compile a list of all Maia candidates and obtain spectra of two of these stars. Again, it seems likely that these are anomalous pulsating stars which are currently not understood.

  7. When stars collide

    NARCIS (Netherlands)

    Glebbeek, E.; Pols, O.R.

    2007-01-01

    When two stars collide and merge they form a new star that can stand out against the background population in a star cluster as a blue straggler. In so called collision runaways many stars can merge and may form a very massive star that eventually forms an intermediate mass blackhole. We have perfor

  8. Measure of the stars

    Energy Technology Data Exchange (ETDEWEB)

    Henbest, N.

    1984-12-13

    The paper concerns the Hertzsprung-Russel (H-R) diagram, which is graph relating the brightness to the surface temperature of the stars. The diagram provides a deep insight into the fundamental properties of the stars. Evolution of the stars; the death of a star; distances; and dating star clusters, are all briefly discussed with reference to the H-R diagram.

  9. Betting against Beta

    DEFF Research Database (Denmark)

    Frazzini, Andrea; Heje Pedersen, Lasse

    2014-01-01

    We present a model with leverage and margin constraints that vary across investors and time. We find evidence consistent with each of the model's five central predictions: (1) Because constrained investors bid up high-beta assets, high beta is associated with low alpha, as we find empirically for......, the return of the BAB factor is low. (4) Increased funding liquidity risk compresses betas toward one. (5) More constrained investors hold riskier assets....... for US equities, 20 international equity markets, Treasury bonds, corporate bonds, and futures. (2) A betting against beta (BAB) factor, which is long leveraged low-beta assets and short high-beta assets, produces significant positive risk-adjusted returns. (3) When funding constraints tighten...

  10. Betting Against Beta

    DEFF Research Database (Denmark)

    Frazzini, Andrea; Heje Pedersen, Lasse

    We present a model with leverage and margin constraints that vary across investors and time. We find evidence consistent with each of the model’s five central predictions: (1) Since constrained investors bid up high-beta assets, high beta is associated with low alpha, as we find empirically for U...... of the BAB factor is low; (4) Increased funding liquidity risk compresses betas toward one; (5) More constrained investors hold riskier assets........S. equities, 20 international equity markets, Treasury bonds, corporate bonds, and futures; (2) A betting-against-beta (BAB) factor, which is long leveraged low beta assets and short high-beta assets, produces significant positive risk-adjusted returns; (3) When funding constraints tighten, the return...

  11. Imperfect World of $\\beta\\beta$-decay Nuclear Data Sets

    CERN Document Server

    Pritychenko, B

    2015-01-01

    The precision of double-beta ($\\beta\\beta$) decay experimental half lives and their uncertainties is reanalyzed. The method of Benford's distributions has been applied to nuclear reaction, structure and decay data sets. First-digit distribution trend for $\\beta\\beta$-decay T$_{1/2}^{2\

  12. Multiplicity of Galactic Cepheids from long-baseline interferometry~III. Sub-percent limits on the relative brightness of a close companion of $\\delta$~Cephei

    CERN Document Server

    Gallenne, A; Kervella, P; Monnier, J D; Schaefer, G H; Roettenbacher, R M; Gieren, W; Pietrzynski, G; McAlister, H; Brummelaar, T ten; Sturmann, J; Sturmann, L; Turner, N; Anderson, R I

    2016-01-01

    We report new CHARA/MIRC interferometric observations of the Cepheid archetype $\\delta$ Cep, which aimed at detecting the newly discovered spectroscopic companion. We reached a maximum dynamic range $\\Delta H $ = 6.4, 5.8, and 5.2 mag, respectively within the relative distance to the Cepheid $r 9.15, 8.31$ and 7.77 mag, respectively for $r < 25$ mas, $25 < r < 50$ mas and $50 < r < 100$ mas. We also found that to be consistent with the predicted orbital period, the companion has to be located at a projected separation $< 24$ mas with a spectral type later than a F0V star.

  13. Equation of State of Protoneutron Star with Trapped Neutrinos

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hua; JIA Huan-Yu

    2006-01-01

    The influence of trapped neutrinos on the proto-neutron star is studied in the framework of relativistic mean-field theory. The results show that trapped neutrinos increase proton fraction and make the equation of state of neutron star matter softer when neglecting hyperonic freedom, while suppress the appearance of hyperons and make the equation of state stiffer when including hyperons in the protoneutron star. The maximum mass, compared with cold neutron star which is in beta equilibrium, decreases by 0.06M☉ for non-strange protoneutron star while increases by 0.21M☉ for protoneutron star with hyperons when the relative number of trapped neutrino is 0.4.

  14. THE INITIAL MASS FUNCTION MODELED BY A LEFT TRUNCATED BETA DISTRIBUTION

    Energy Technology Data Exchange (ETDEWEB)

    Zaninetti, Lorenzo, E-mail: zaninetti@ph.unito.it [Dipartimento di Fisica, Via Pietro Giuria 1, I-10125 Torino (Italy)

    2013-03-10

    The initial mass function for stars is usually fitted by three straight lines, which means it has seven parameters. The presence of brown dwarfs (BDs) increases the number of straight lines to four and the number of parameters to nine. Another common fitting function is the lognormal distribution, which is characterized by two parameters. This paper is devoted to demonstrating the advantage of introducing a left truncated beta probability density function, which is characterized by four parameters. The constant of normalization, the mean, the mode, and the distribution function are calculated for the left truncated beta distribution. The normal beta distribution that results from convolving independent normally distributed and beta distributed components is also derived. The chi-square test and the Kolmogorov-Smirnov test are performed on a first sample of stars and BDs that belongs to the massive young cluster NGC 6611, and on a second sample that represents the masses of the stars of the cluster NGC 2362.

  15. The initial mass function modeled by a left truncated beta distribution

    CERN Document Server

    Zaninetti, L

    2013-01-01

    The initial mass function (IMF) for the stars is usually fitted by three straight lines, which means seven parameters. The presence of brown dwarfs (BD) increases to four the straight lines and to nine the parameters. Another common fitting function is the lognormal distribution, which is characterized by two parameters. This paper is devoted to demonstrating the advantage of introducing a left truncated beta probability density function, which is characterized by four parameters. The constant of normalization, the mean, the mode and the distribution function are calculated for the left truncated beta distribution. The normal-beta (NB) distribution which results from convolving independent normally distributed and beta distributed components is also derived. The chi-square test and the K-S test are performed on a first sample of stars and BDs which belongs to the massive young cluster NGC 6611 and on a second sample which represents the star's masses of the cluster NGC 2362.

  16. Negative Beta Encoder

    CERN Document Server

    Kohda, Tohru; Aihara, Kazuyuki

    2008-01-01

    A new class of analog-digital (A/D), digital-analog (D/A) converters as an alternative to conventional ones, called $\\beta$-encoder, has been shown to have exponential accuracy in the bit rates while possessing self-correction property for fluctuations of amplifier factor $\\beta$ and quantizer threshold $\

  17. Double beta decay experiments

    CERN Document Server

    Barabash, A S

    2011-01-01

    The present status of double beta decay experiments is reviewed. The results of the most sensitive experiments are discussed. Proposals for future double beta decay experiments with a sensitivity to the $$ at the level of (0.01--0.1) eV are considered.

  18. Genetics Home Reference: beta thalassemia

    Science.gov (United States)

    ... Understand Genetics Home Health Conditions beta thalassemia beta thalassemia Enable Javascript to view the expand/collapse boxes. Download PDF Open All Close All Description Beta thalassemia is a blood disorder that reduces the production ...

  19. Multiplicity of Galactic Cepheids from long-baseline interferometry - III. Sub-percent limits on the relative brightness of a close companion of δ Cephei

    Science.gov (United States)

    Gallenne, A.; Mérand, A.; Kervella, P.; Monnier, J. D.; Schaefer, G. H.; Roettenbacher, R. M.; Gieren, W.; Pietrzyński, G.; McAlister, H.; ten Brummelaar, T.; Sturmann, J.; Sturmann, L.; Turner, N.; Anderson, R. I.

    2016-09-01

    We report new CHARA/Michigan InfraRed Combiner interferometric observations of the Cepheid archetype δ Cep, which aimed at detecting the newly discovered spectroscopic companion. We reached a maximum dynamic range ΔH = 6.4, 5.8 and 5.2 mag, respectively, within the relative distance to the Cepheid r 9.15, 8.31 and 7.77 mag, respectively, for r < 25 mas, 25 < r < 50 mas and 50 < r < 100 mas. We also found that to be consistent with the predicted orbital period (Anderson et al.), the companion has to be located at a projected separation <24 mas with a spectral type later than an F0V star.

  20. Rapid synthesis of beta zeolites

    Science.gov (United States)

    Fan, Wei; Chang, Chun -Chih; Dornath, Paul; Wang, Zhuopeng

    2015-08-18

    The invention provides methods for rapidly synthesizing heteroatom containing zeolites including Sn-Beta, Si-Beta, Ti-Beta, Zr-Beta and Fe-Beta. The methods for synthesizing heteroatom zeolites include using well-crystalline zeolite crystals as seeds and using a fluoride-free, caustic medium in a seeded dry-gel conversion method. The Beta zeolite catalysts made by the methods of the invention catalyze both isomerization and dehydration reactions.

  1. Can strange stars mimic dark energy stars?

    CERN Document Server

    Deb, Debabrata; Guha, B K; Ray, Saibal

    2016-01-01

    The possibility of strange stars mixed with dark energy to be one of candidates for dark energy stars is the main issue of the present study. Our investigation shows that quark matter is acting as dark energy after certain yet unknown critical condition inside the quark stars. Our proposed model reveals that strange stars mixed with dark energy feature not only a physically acceptable stable model but also mimic characteristics of dark energy stars. The plausible connections are shown through the mass-radius relation as well as the entropy and temperature. We particulary note that two-fluid distribution is the major reason for anisotropic nature of the spherical stellar system.

  2. Lifestyles of the Stars.

    Science.gov (United States)

    National Aeronautics and Space Administration, Cocoa Beach, FL. John F. Kennedy Space Center.

    Some general information on stars is provided in this National Aeronautics and Space Administration pamphlet. Topic areas briefly discussed are: (1) the birth of a star; (2) main sequence stars; (3) red giants; (4) white dwarfs; (5) neutron stars; (6) supernovae; (7) pulsars; and (8) black holes. (JN)

  3. Circumnuclear Regions of Star Formation in Early Type Galaxies

    CERN Document Server

    Diaz, Angeles I; Hagele, Guillermo F; Castellanos, Marcelo

    2008-01-01

    Circumnuclear star forming regions, also called hotspots, are often found in the inner regions of some spiral galaxies where intense processes of star formation are taking place. In the UV, massive stars dominate the observed circumnuclear emission even in the presence of an active nucleus, contributing between 30 and 50% to the H$\\beta$ total emission of the nuclear zone. Spectrophotometric data of moderate resolution (3000 < R < 11000) are presented from which the physical properties of the ionized gas: electron density, oxygen abundances, ionization structure etc. have been derived.

  4. Neutrinoless double beta decay

    Indian Academy of Sciences (India)

    Kai Zuber

    2012-10-01

    The physics potential of neutrinoless double beta decay is discussed. Furthermore, experimental considerations as well as the current status of experiments are presented. Finally, an outlook towards the future, work on nuclear matrix elements and alternative processes is given.

  5. The Cambridge Double Star Atlas

    Science.gov (United States)

    MacEvoy, Bruce; Tirion, Wil

    2015-12-01

    Preface; What are double stars?; The binary orbit; Double star dynamics; Stellar mass and the binary life cycle; The double star population; Detecting double stars; Double star catalogs; Telescope optics; Preparing to observe; Helpful accessories; Viewing challenges; Next steps; Appendices: target list; Useful formulas; Double star orbits; Double star catalogs; The Greek alphabet.

  6. Alpha and Beta Determinations

    CERN Document Server

    Dunietz, Isard

    1999-01-01

    Because the Bd -> J/psi Ks asymmetry determines only sin(2 beta), a discrete ambiguity in the true value of beta remains. This note reviews how the ambiguity can be removed. Extractions of the CKM angle alpha are discussed next. Some of the methods require very large data samples and will not be feasible in the near future. In the near future, semi-inclusive CP-violating searches could be undertaken, which are reviewed last.

  7. {beta} - amyloid imaging probes

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Jae Min [Seoul National University College of Medicine, Seoul (Korea, Republic of)

    2007-04-15

    Imaging distribution of {beta} - amyloid plaques in Alzheimer's disease is very important for early and accurate diagnosis. Early trial of the {beta} -amyloid plaques includes using radiolabeled peptides which can be only applied for peripheral {beta} - amyloid plaques due to limited penetration through the blood brain barrier (BBB). Congo red or Chrysamine G derivatives were labeled with Tc-99m for imaging {beta} - amyloid plaques of Alzheimer patient's brain without success due to problem with BBB penetration. Thioflavin T derivatives gave breakthrough for {beta} - amyloid imaging in vivo, and a benzothiazole derivative [C-11]6-OH-BTA-1 brought a great success. Many other benzothiazole, benzoxazole, benzofuran, imidazopyridine, and styrylbenzene derivatives have been labeled with F-18 and I-123 to improve the imaging quality. However, [C-11]6-OH-BTA-1 still remains as the best. However, short half-life of C-11 is a limitation of wide distribution of this agent. So, it is still required to develop an Tc-99m, F-18 or I-123 labeled agent for {beta} - amyloid imaging agent.

  8. Beta cell dynamics: beta cell replenishment, beta cell compensation and diabetes.

    Science.gov (United States)

    Cerf, Marlon E

    2013-10-01

    Type 2 diabetes, characterized by persistent hyperglycemia, arises mostly from beta cell dysfunction and insulin resistance and remains a highly complex metabolic disease due to various stages in its pathogenesis. Glucose homeostasis is primarily regulated by insulin secretion from the beta cells in response to prevailing glycemia. Beta cell populations are dynamic as they respond to fluctuating insulin demand. Beta cell replenishment and death primarily regulate beta cell populations. Beta cells, pancreatic cells, and extra-pancreatic cells represent the three tiers for replenishing beta cells. In rodents, beta cell self-replenishment appears to be the dominant source for new beta cells supported by pancreatic cells (non-beta islet cells, acinar cells, and duct cells) and extra-pancreatic cells (liver, neural, and stem/progenitor cells). In humans, beta cell neogenesis from non-beta cells appears to be the dominant source of beta cell replenishment as limited beta cell self-replenishment occurs particularly in adulthood. Metabolic states of increased insulin demand trigger increased insulin synthesis and secretion from beta cells. Beta cells, therefore, adapt to support their physiology. Maintaining physiological beta cell populations is a strategy for targeting metabolic states of persistently increased insulin demand as in diabetes.

  9. Surveying the Bright Stars by Optical Interferometry I: A Search for Multiplicity Among Stars of Spectral Types F - K

    CERN Document Server

    Hutter, Donald; Tycner, Christopher; Benson, James; Hummel, Christian; Sanborn, Jason; Franz, Otto G; Johnston, Kenneth

    2016-01-01

    We present the first results from an ongoing survey for multiplicity among the bright stars using the Navy Precision Optical Interferometer (NPOI). We first present a summary of NPOI observations of known multiple systems, including the first detection of the companion of $\\beta$ Scuti with precise relative astrometry, to illustrate the instrument's detection sensitivity for binaries at magnitude differences $\\Delta$$m$ $\\lessapprox$ 3 over the range of angular separation 3 - 860 milliarcseconds (mas). A limiting $\\Delta$$m_{700}$ $\\sim$ 3.5 is likely for binaries where the component spectral types differ by less than two. Model fits to these data show good agreement with published orbits, and we additionally present a new orbit solution for one of these stars, $\\sigma$ Her. We then discuss early results of the survey of bright stars at $\\delta$ $\\geq$ -20$\\deg$. This survey, which complements previous surveys of the bright stars by speckle interferometry, initially emphasizes bright stars of spectral types F...

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

    CERN Document Server

    Yelda, D P S

    2006-01-01

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

  11. Infrared spectroscopy of star formation in galaxies

    Science.gov (United States)

    Beck, Sara C.; Ho, Paul T. P.; Turner, Jean L.

    1987-01-01

    The Brackett alpha and beta lines with 7.2 seconds angular and 350 km/s velocity resolution were observed in 11 infrared-bright galaxies. From these measurements extinctions, Lyman continuum fluxes, and luminosities due to OB stars were derived. The galaxies observed to date are NGC3690, M38, NGC 5195, Arp 220, NGC 520, NGC660, NGC1614, NGC 3079, NGC 6946, NGC 7714, and Maffei 2, all of which were suggested at some time to be starburst ogjects. The contributions of OB stars to the luminosities of these galaxies can be quantified from the measurements and range from insignificant to sufficient to account for the total energy output. The OB stellar luminosities observed are as high as 10 to the 12th solar luminosities in the galaxy NGC 1614. It is noteworthy that star formation can play very different roles in the infrared energy output of galaxies of similar luminosity, as for example Arp 220 and NGC 1614. In addition to probing the star formation process in these galaxies, the Brackett line measurements, when compared to radio and infrared continuum results, have revealed some unexpected and at present imperfectly understood phenomena: in some very luminous sources the radio continuum appears to be suppressed relative to the infrared recombination lines; in many galaxies there is a substantial excess of 10 micron flux over that predicted from simple models of Lyman alpha heating of dust if young stars are the only significant energy source.

  12. Spectroscopic variability of two Oe stars

    CERN Document Server

    Rauw, G; Naze, Y; Eversberg, T; Alves, F; Arnold, W; Bergmann, T; Viegas, N G Correia; Fahed, R; Fernando, A; Gonzalez-Perez, J N; Carreira, L F Gouveia; Hempelmann, A; Hunger, T; Knapen, J H; Leadbeater, R; Dias, F Marques; Mittag, M; Moffat, A F J; Reinecke, N; Ribeiro, J; Romeo, N; Gallego, J Sanchez; Santos, E M Dos; Schanne, L; Schmitt, J H M M; Schroeder, K -P; Stahl, O; Stober, Ba; Stober, Be; Vollmann, K

    2015-01-01

    The Oe stars HD45314 and HD60848 have recently been found to exhibit very different X-ray properties: whilst HD60848 has an X-ray spectrum and emission level typical of most OB stars, HD45314 features a much harder and brighter X-ray emission, making it a so-called gamma Cas analogue. Monitoring the optical spectra could provide hints towards the origin of these very different behaviours. We analyse a large set of spectroscopic observations of HD45314 and HD60848, extending over 20 years. We further attempt to fit the H-alpha line profiles of both stars with a simple model of emission line formation in a Keplerian disk. Strong variations in the strengths of the H-alpha, H-beta, and He I 5876 emission lines are observed for both stars. In the case of HD60848, we find a time lag between the variations in the equivalent widths of these lines. The emission lines are double peaked with nearly identical strengths of the violet and red peaks. The H-alpha profile of this star can be successfully reproduced by our mod...

  13. Braking the Gas in the beta Pictoris Disk

    CERN Document Server

    Fern'andez, R; Wu, Y; Brandeker, Alexis; Fern\\'andez, Rodrigo

    2006-01-01

    (Abridged) The main sequence star beta Pictoris hosts the best studied circumstellar disk to date. Nonetheless, a long-standing puzzle has been around since the detection of metallic gas in the disk: radiation pressure from the star should blow the gas away, yet the observed motion is consistent with Keplerian rotation. In this work we search for braking mechanisms that can resolve this discrepancy. We find that all species affected by radiation force are heavily ionized and dynamically coupled into a single fluid by Coulomb collisions, reducing the radiation force on species feeling the strongest acceleration. For a gas of solar composition, the resulting total radiation force still exceeds gravity, while a gas of enhanced carbon abundance could be self-braking. We also explore two other braking agents: collisions with dust grains and neutral gas. Grains surrounding beta Pic are photoelectrically charged to a positive electrostatic potential. If a significant fraction of the grains are carbonaceous (10% in t...

  14. Boosted beta regression.

    Directory of Open Access Journals (Sweden)

    Matthias Schmid

    Full Text Available Regression analysis with a bounded outcome is a common problem in applied statistics. Typical examples include regression models for percentage outcomes and the analysis of ratings that are measured on a bounded scale. In this paper, we consider beta regression, which is a generalization of logit models to situations where the response is continuous on the interval (0,1. Consequently, beta regression is a convenient tool for analyzing percentage responses. The classical approach to fit a beta regression model is to use maximum likelihood estimation with subsequent AIC-based variable selection. As an alternative to this established - yet unstable - approach, we propose a new estimation technique called boosted beta regression. With boosted beta regression estimation and variable selection can be carried out simultaneously in a highly efficient way. Additionally, both the mean and the variance of a percentage response can be modeled using flexible nonlinear covariate effects. As a consequence, the new method accounts for common problems such as overdispersion and non-binomial variance structures.

  15. ENERGY STAR Certified Furnaces

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 4.0 ENERGY STAR Program Requirements for Furnaces that are effective as of February 1,...

  16. ENERGY STAR Certified Boilers

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 3.0 ENERGY STAR Program Requirements for Boilers that are effective as of October 1,...

  17. ENERGY STAR Certified Computers

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 6.1 ENERGY STAR Program Requirements for Computers that are effective as of June 2, 2014....

  18. Aperture-free star formation rate of SDSS star-forming galaxies

    CERN Document Server

    Puertas, S Duarte; Iglesias-Paramo, J; Kehrig, C; Perez-Montero, E; Rosales-Ortega, F F

    2016-01-01

    Large area surveys with a high number of galaxies observed have undoubtedly marked a milestone in the understanding of several properties of galaxies, such as star-formation history, morphology, and metallicity. However, in many cases, these surveys provide fluxes from fixed small apertures (e.g. fibre), which cover a scant fraction of the galaxy, compelling us to use aperture corrections to study the global properties of galaxies. In this work, we derive the current total star formation rate (SFR) of Sloan Digital Sky Survey (SDSS) star-forming galaxies, using an empirically based aperture correction of the measured $\\rm H\\alpha$ flux for the first time, thus minimising the uncertainties associated with reduced apertures. All the $\\rm H\\alpha$ fluxes have been extinction-corrected using the $\\rm H\\alpha/H\\beta$ ratio free from aperture effects. The total SFR for $\\sim$210,000 SDSS star-forming galaxies has been derived applying pure empirical $\\rm H\\alpha$ and $\\rm H\\alpha/H\\beta$ aperture corrections based ...

  19. Autonomous Star Tracker Algorithms

    DEFF Research Database (Denmark)

    Betto, Maurizio; Jørgensen, John Leif; Kilsgaard, Søren

    1998-01-01

    Proposal, in response to an ESA R.f.P., to design algorithms for autonomous star tracker operations.The proposal also included the development of a star tracker breadboard to test the algorithms performances.......Proposal, in response to an ESA R.f.P., to design algorithms for autonomous star tracker operations.The proposal also included the development of a star tracker breadboard to test the algorithms performances....

  20. Star operations and Pullbacks

    OpenAIRE

    Fontana, Marco; Park, Mi Hee

    2003-01-01

    In this paper we study the star operations on a pullback of integral domains. In particular, we characterize the star operations of a domain arising from a pullback of ``a general type'' by introducing new techniques for ``projecting'' and ``lifting'' star operations under surjective homomorphisms of integral domains. We study the transfer in a pullback (or with respect to a surjective homomorphism) of some relevant classes or distinguished properties of star operations such as $v-, t-, w-, b...

  1. A probable giant planet imaged in the Beta Pictoris disk

    CERN Document Server

    Lagrange, A -M; Chauvin, G; Fusco, T; Ehrenreich, D; Mouillet, D; Rousset, G; Rouan, D; Allard, F; Gendron, E; Charton, J; Mugnier, L; Rabou, P; Montri, J; Lacombe, F

    2008-01-01

    Since the discovery of its dusty disk in 1984, Beta Pictoris has become the prototype of young early-type planetary systems, and there are now various indications that a massive Jovian planet is orbiting the star at ~ 10 AU. However, no planets have been detected around this star so far. Our goal was to investigate the close environment of Beta Pic, searching for planetary companion(s). Deep adaptive-optics L'-band images of Beta Pic were recorded using the NaCo instrument at the Very Large Telescope. A faint point-like signal is detected at a projected distance of ~ 8 AU from the star, within the North-East side of the dust disk. Various tests were made to rule out with a good confidence level possible instrumental or atmospheric artifacts. The probability of a foreground or background contaminant is extremely low, based in addition on the analysis of previous deep Hubble Space Telescope images. The object L'=11.2 apparent magnitude would indicate a typical temperature of ~1500 K and a mass of ~ 8 Jovian mas...

  2. Standard Stars for the BYU H-alpha Photometric System (Abstract)

    Science.gov (United States)

    Joner, M.; Hintz, E.

    2015-12-01

    (Abstract only) We present primary standard stars for the BYU H-alpha photometric system. This system is similar to the H-beta photometric system that is often used with the intermediate band uvby system. Both systems use the difference between magnitudes measured in a wide (15-20-nm) and narrow (3-nm) bandpass centered on one of the strong Balmer lines of hydrogen to establish a color index. Line indices formed in this manner are independent of atmospheric extinction and interstellar reddening. These indices provide intrinsic measures of effective temperature for stars with spectral types between B and G. The present primary standard stars for the BYU system as established using spectroscopic observations that cover the region between the H-alpha and H-beta lines. The indices were formed using synthetic photometry reductions to convolve ideal filter profiles with the observed spectra. The number of observations per star is generally in excess of 25. Some stars have been observed more than 100 times over a period of 7 years. The typical error per observation for these stars is on the order of 1-3 mmag. In addition to the standard field stars, we present H-alpha and H-beta observations of individual stars that are members of selected open clusters. These include the Hyades, Pleiades, Coma, and NGC 752 clusters. Additional stars that exhibit varying degrees of hydrogen emission are easily distinguished in a plot of the alpha-beta plane. We have found that candidates for emission line objects, high mass x-ray binaries, and young stellar objects are readily identified in our alpha-beta plots. We acknowledge continued support from the BYU College of Physical and Mathematical Sciences as well as support from NSF Grant AST #0618209. We also thank the Dominion Astrophysical Observatory for continued allocation of robotic observing time for spectroscopy on the 1.2-m telescope.

  3. Beta and Gamma Gradients

    DEFF Research Database (Denmark)

    Løvborg, Leif; Gaffney, C. F.; Clark, P. A.;

    1985-01-01

    Experimental and/or theoretical estimates are presented concerning, (i) attenuation within the sample of beta and gamma radiation from the soil, (ii) the gamma dose within the sample due to its own radioactivity, and (iii) the soil gamma dose in the proximity of boundaries between regions...... of differing radioactivity. It is confirmed that removal of the outer 2 mm of sample is adequate to remove influence from soil beta dose and estimates are made of the error introduced by non-removal. Other evaluations include variation of the soil gamma dose near the ground surface and it appears...

  4. Covering tree with stars

    DEFF Research Database (Denmark)

    Baumbach, Jan; Guo, Jian-Ying; Ibragimov, Rashid

    2013-01-01

    We study the tree edit distance problem with edge deletions and edge insertions as edit operations. We reformulate a special case of this problem as Covering Tree with Stars (CTS): given a tree T and a set of stars, can we connect the stars in by adding edges between them such that the resulting ...

  5. Covering tree with stars

    DEFF Research Database (Denmark)

    Baumbach, Jan; Guo, Jiong; Ibragimov, Rashid

    2015-01-01

    We study the tree edit distance problem with edge deletions and edge insertions as edit operations. We reformulate a special case of this problem as Covering Tree with Stars (CTS): given a tree T and a set of stars, can we connect the stars in by adding edges between them such that the resulting ...

  6. Magnetism in massive stars

    NARCIS (Netherlands)

    Henrichs, H.F.

    2012-01-01

    Stars with mass more than 8 solar masses end their lives as neutron stars, which we mostly observe as highly magnetized objects. Where does this magnetic field come from? Such a field could be formed during the collapse, or is a (modified) remnant of a fossil field since the birth of the star, or ot

  7. Managing the star performer.

    Science.gov (United States)

    Hills, Laura

    2013-01-01

    Our culture seems to be endlessly fascinated with its stars in entertainment, athletics, politics, and business, and holds fast to the idea that extraordinary talent accounts for an individual's extraordinary performance. At first glance, managing a star performer in your medical practice may seem like it would be an easy task. However, there's much more to managing a star performer than many practice managers realize. The concern is how to keep the star performer happy and functioning at a high level without detriment to the rest of the medical practice team. This article offers tips for practice managers who manage star performers. It explores ways to keep the star performer motivated, while at the same time helping the star performer to meld into the existing medical practice team. This article suggests strategies for redefining the star performer's role, for holding the star performer accountable for his or her behavior, and for coaching the star performer. Finally, this article offers practical tips for keeping the star performer during trying times, for identifying and cultivating new star performers, and for managing medical practice prima donnas.

  8. America's Star Libraries

    Science.gov (United States)

    Lyons, Ray; Lance, Keith Curry

    2009-01-01

    "Library Journal"'s new national rating of public libraries, the "LJ" Index of Public Library Service, identifies 256 "star" libraries. It rates 7,115 public libraries. The top libraries in each group get five, four, or three Michelin guide-like stars. All included libraries, stars or not, can use their scores to learn from their peers and improve…

  9. To rescue a star

    OpenAIRE

    1996-01-01

    Massless neutrinos are exchanged in a neutron star, leading to long range interactions. Many body forces of this type follow and we resum them. Their net contribution to the total energy is negligible as compared to the star mass. The stability of the star is not in danger, contrary to recent assertions.

  10. Analysis of Kepler B stars: rotational modulation and Maia variables

    CERN Document Server

    Balona, L A; Daszynska-Daszkiewicz, J; De Cat, P

    2015-01-01

    We examine 4-yr almost continuous Kepler photometry of 115 B stars. We find that the light curves of 39 percent of these stars are simply described by a low-frequency sinusoid and its harmonic, usually with variable amplitudes, which we interpret as rotational modulation. A large fraction (28 percent) of B stars might be classified as ellipsoidal variables, but a statistical argument suggests that these are probably rotational variables as well. About 8 percent of the rotational variables have a peculiar periodogram feature which is common among A stars. The physical cause of this is very likely related to rotation. The presence of so many rotating variables indicates the presence of star spots. This suggests that magnetic fields are indeed generated in radiative stellar envelopes. We find five beta Cep variables, all of which have low frequencies with relatively large amplitudes. The presence of these frequencies is a puzzle. About half the stars with high frequencies are cooler than the red edge of the beta...

  11. The evolution of low mass, close binary systems with a neutron star component: a detailed grid

    CERN Document Server

    De Vito, M A

    2012-01-01

    In close binary systems composed of a normal, donor star and an accreting neutron star, the amount of material received by the accreting component is, so far, a real intrigue. In the literature there are available models that link the accretion disk surrounding the neutron star with the amount of material it receives, but there is no model linking the amount of matter lost by the donor star to that falling onto the neutron star. In this paper we explore the evolutionary response of these close binary systems when we vary the amount of material accreted by the neutron star. We consider a parameter \\beta, which represents the fraction of material lost by the normal star that can be accreted by the neutron star. \\beta is considered as constant throughout evolution. We have computed the evolution of a set of models considering initial donor star masses (in solar units) between 0.5 and 3.50, initial orbital periods (in days) between 0.175 and 12, initial masses of neutron stars (in solar units) of 0.80, 1.00, 1.20...

  12. Stochastically excited oscillations on the upper main sequence

    DEFF Research Database (Denmark)

    Antoci, Victoria

    2013-01-01

    Convective envelopes in stars on the main sequence are usually connected only with stars of spectral types F5 or later. However, observations as well as theory indicate that the convective outer layers in earlier stars, despite being shallow, are still effective and turbulent enough to stochastic......Convective envelopes in stars on the main sequence are usually connected only with stars of spectral types F5 or later. However, observations as well as theory indicate that the convective outer layers in earlier stars, despite being shallow, are still effective and turbulent enough...... to stochastically excite oscillations. Because of the low amplitudes, exploring stochastically excited pulsations became possible only with space missions such as Kepler and CoRoT. Here I review the recent results and discuss among others, pulsators such as delta Scuti, gamma Doradus, roAp, beta Cephei, Slowly...

  13. Nuclear physics of stars

    CERN Document Server

    Iliadis, Christian

    2015-01-01

    Most elements are synthesized, or ""cooked"", by thermonuclear reactions in stars. The newly formed elements are released into the interstellar medium during a star's lifetime, and are subsequently incorporated into a new generation of stars, into the planets that form around the stars, and into the life forms that originate on the planets. Moreover, the energy we depend on for life originates from nuclear reactions that occur at the center of the Sun. Synthesis of the elements and nuclear energy production in stars are the topics of nuclear astrophysics, which is the subject of this book

  14. Magnetic chemically peculiar stars

    CERN Document Server

    Schöller, Markus

    2015-01-01

    Chemically peculiar (CP) stars are main-sequence A and B stars with abnormally strong or weak lines for certain elements. They generally have magnetic fields and all observables tend to vary with the same period. Chemically peculiar stars provide a wealth of information; they are natural atomic and magnetic laboratories. After a brief historical overview, we discuss the general properties of the magnetic fields in CP stars, describe the oblique rotator model, explain the dependence of the magnetic field strength on the rotation, and concentrate at the end on HgMn stars.

  15. Applied Beta Dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Rich, B.L.

    1986-01-01

    Measurements of beta and/or nonpenetrating exposure results is complicated and past techniques and capabilities have resulted in significant inaccuracies in recorded results. Current developments have resulted in increased capabilities which make the results more accurate and should result in less total exposure to the work force. Continued development of works in progress should provide equivalent future improvements.

  16. Beta Thalassemia (For Parents)

    Science.gov (United States)

    ... had their spleens removed. Slower growth rates. The anemia resulting from beta thalassemia can cause children to grow more slowly and also can lead ... boost production of new red blood cells. Some children with moderate anemia may require an occasional blood transfusion , particularly after ...

  17. Trichoderma .beta.-glucosidase

    Science.gov (United States)

    Dunn-Coleman, Nigel; Goedegebuur, Frits; Ward, Michael; Yao, Jian

    2006-01-03

    The present invention provides a novel .beta.-glucosidase nucleic acid sequence, designated bgl3, and the corresponding BGL3 amino acid sequence. The invention also provides expression vectors and host cells comprising a nucleic acid sequence encoding BGL3, recombinant BGL3 proteins and methods for producing the same.

  18. Roughing up Beta

    DEFF Research Database (Denmark)

    Bollerslev, Tim; Li, Sophia Zhengzi; Todorov, Viktor

    Motivated by the implications from a stylized equilibrium pricing framework, we investigate empirically how individual equity prices respond to continuous, or \\smooth," and jumpy, or \\rough," market price moves, and how these different market price risks, or betas, are priced in the cross-section...

  19. Utilizing Synthetic UV Spectra to Explore the Physical Basis for the Classification of Lambda Boötis Stars

    Science.gov (United States)

    Cheng, Kwang-Ping; Neff, James E.; Johnson, Dustin M.; Tarbell, Erik S.; Romo, Christopher A.; Prabhaker, Arvind; Steele, Patricia A.; Gray, Richard O.; Corbally, Christopher J.

    2016-04-01

    Lambda Boo-type stars are a group of late B to early F-type Population I dwarfs that show mild to extreme deficiencies of iron-peak elements (up to 2 dex), but their C, N, O, and S abundances are near solar. This intriguing stellar class has recently regained the spotlight because of the directly imaged planets around a confirmed Lambda Boo star, HR 8799, and a suggested Lambda Boo star, Beta Pictoris. The discovery of a giant asteroid belt around Vega, another possible Lambda Boo star, also suggests hidden planets. The possible link between Lambda Boo stars and planet-bearing stars motivates us to study Lambda Boo stars systematically. Since the peculiar nature of the prototype Lambda Boötis was first noticed in 1943, Lambda Boo candidates published in the literature have been selected using widely different criteria. In order to determine the origin of Lambda Boo stars’ unique abundance pattern and to better discriminate between theories explaining the Lambda Boo phenomenon, a consistent working definition of Lambda Boo stars is needed. We have re-evaluated all published Lambda Boo candidates and their available ultraviolet and visible spectra. In this paper, using observed and synthetic spectra, we explore the physical basis for the classification of Lambda Boo stars, and develop quantitative criteria that discriminate metal-poor stars from bona fide Lambda Boo stars. Based on these stricter Lambda Boo classification criteria, we conclude that neither Beta Pictoris nor Vega should be classified as Lambda Boo stars.

  20. UTILIZING SYNTHETIC UV SPECTRA TO EXPLORE THE PHYSICAL BASIS FOR THE CLASSIFICATION OF LAMBDA BOÖTIS STARS

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Kwang-Ping; Johnson, Dustin M.; Tarbell, Erik S.; Romo, Christopher A.; Prabhaker, Arvind [Cal. State Univ., Fullerton, Fullerton, CA (United States); Neff, James E.; Steele, Patricia A. [College of Charleston, Charleston, SC (United States); Gray, Richard O. [Appalachian State Univ., Boone, NC (United States); Corbally, Christopher J. [Vatican Observatory, Tucson, AZ (United States)

    2016-04-15

    Lambda Boo-type stars are a group of late B to early F-type Population I dwarfs that show mild to extreme deficiencies of iron-peak elements (up to 2 dex), but their C, N, O, and S abundances are near solar. This intriguing stellar class has recently regained the spotlight because of the directly imaged planets around a confirmed Lambda Boo star, HR 8799, and a suggested Lambda Boo star, Beta Pictoris. The discovery of a giant asteroid belt around Vega, another possible Lambda Boo star, also suggests hidden planets. The possible link between Lambda Boo stars and planet-bearing stars motivates us to study Lambda Boo stars systematically. Since the peculiar nature of the prototype Lambda Boötis was first noticed in 1943, Lambda Boo candidates published in the literature have been selected using widely different criteria. In order to determine the origin of Lambda Boo stars’ unique abundance pattern and to better discriminate between theories explaining the Lambda Boo phenomenon, a consistent working definition of Lambda Boo stars is needed. We have re-evaluated all published Lambda Boo candidates and their available ultraviolet and visible spectra. In this paper, using observed and synthetic spectra, we explore the physical basis for the classification of Lambda Boo stars, and develop quantitative criteria that discriminate metal-poor stars from bona fide Lambda Boo stars. Based on these stricter Lambda Boo classification criteria, we conclude that neither Beta Pictoris nor Vega should be classified as Lambda Boo stars.

  1. THE FIRST STARS

    Directory of Open Access Journals (Sweden)

    Daniel J. Whalen

    2013-12-01

    Full Text Available Pop III stars are the key to the character of primeval galaxies, the first heavy elements, the onset of cosmological reionization, and the seeds of supermassive black holes. Unfortunately, in spite of their increasing sophistication, numerical models of Pop III star formation cannot yet predict the masses of the first stars. Because they also lie at the edge of the observable universe, individual Pop III stars will remain beyond the reach of observatories for decades to come, and so their properties are unknown. However, it will soon be possible to constrain their masses by direct detection of their supernovae, and by reconciling their nucleosynthetic yields to the chemical abundances measured in ancient metal-poor stars in the Galactic halo, some of which may bear the ashes of the first stars. Here, I review the state of the art in numerical simulations of primordial stars and attempts to directly and indirectly constrain their properties.

  2. Main-sequence variable stars in young open cluster NGC 1893

    OpenAIRE

    Lata, Sneh; Yadav, Ram Kesh; Pandey, A.K.(Indian Institute of Technology Bombay (IIT), Mumbai, India); Richichi, Andrea; Eswaraiah, C.; Kumar, Brajesh; Kappelmann, Norbert; Sharma, Saurabh

    2014-01-01

    In this paper we present time series photometry of 104 variable stars in the cluster region NGC 1893. The association of the present variable candidates to the cluster NGC 1893 has been determined by using $(U-B)/(B-V)$ and $(J-H)/(H-K)$ two colour diagrams, and $V/(V-I)$ colour magnitude diagram. Forty five stars are found to be main-sequence variables and these could be B-type variable stars associated with the cluster. We classified these objects as $\\beta$ Cep, slowly pulsating B stars an...

  3. TGF-beta and osteoarthritis.

    NARCIS (Netherlands)

    Blaney Davidson, E.N.; Kraan, P.M. van der; Berg, W.B. van den

    2007-01-01

    OBJECTIVE: Cartilage damage is a major problem in osteoarthritis (OA). Growth factors like transforming growth factor-beta (TGF-beta) have great potential in cartilage repair. In this review, we will focus on the potential therapeutic intervention in OA with TGF-beta, application of the growth facto

  4. Neutron Star Kicks and their Relationship to Supernovae Ejecta Mass

    CERN Document Server

    Bray, J C

    2016-01-01

    We propose a simple model to explain the velocity of young neutron stars. We attempt to confirm a relationship between the amount of mass ejected in the formation of the neutron star and the `kick' velocity imparted to the compact remnant resulting from the process. We assume the velocity is given by $v_{\\rm kick}=\\alpha\\,(M_{\\rm ejecta} / M_{\\rm remnant}) + \\beta\\,$. To test this simple relationship we use the BPASS (Binary Population and Spectral Synthesis) code to create stellar population models from both single and binary star evolutionary pathways. We then use our Remnant Ejecta and Progenitor Explosion Relationship (REAPER) code to apply different $\\alpha$ and $\\beta$ values and three different `kick' orientations then record the resulting velocity probability distributions. We find that while a single star population provides a poor fit to the observational data, the binary population provides an excellent fit. Values of $\\alpha=70\\, {\\rm km\\,s^{-1}}$ and $\\beta=110\\,{\\rm km\\,s^{-1}}$ reproduce the \\c...

  5. Differential regulation of chemoattractant-stimulated beta 2, beta 3, and beta 7 integrin activity.

    Science.gov (United States)

    Sadhu, C; Masinovsky, B; Staunton, D E

    1998-06-01

    Leukocyte adhesion to endothelium and extravasation are dynamic processes that require activation of integrins. Chemoattractants such as IL-8 and FMLP are potent activators of leukocyte integrins. To compare the chemoattractant-stimulated activation of three integrins, alpha 4 beta 7, alpha L beta 2, and alpha V beta 3, in the same cellular context, we expressed an IL-8 receptor (IL-8RA) and FMLP receptor (FPR) in the lymphoid cell line JY. Chemoattractants induced a rapid increase in alpha L beta 2- and alpha V beta 3-dependent JY adhesion within 5 min, and it was sustained for 30 min. In contrast, stimulation of alpha 4 beta 7-dependent adhesion was transient, returning to basal levels by 30 min. The activation profiles of the integrins were similar regardless of whether IL-8 or FMLP was used for induction. We also demonstrate that alpha 4 beta 7-dependent adhesion was uniquely responsive to the F actin-disrupting agent cytochalasin D and the protein kinase C (PKC) inhibitor chelerythrin. While alpha V beta 3- and alpha L beta 2-mediated cell adhesion was significantly reduced by cytochalasin D, alpha 4 beta 7-mediated adhesion was enhanced. Chelerythrin inhibited both the IL-8 and PMA activation of alpha L beta 2 and alpha V beta 3. In contrast, inducible alpha 4 beta 7 activity was unaffected, and basal activity was increased. These findings demonstrate that the mechanism of alpha 4 beta 7 regulation by chemoattractants is different from that of alpha L beta 2 and alpha V beta 3 and that it appears to involve distinct cytoskeletal and PKC dependencies. In addition, PKC activity may be a positive or negative regulator of integrin-dependent adhesion.

  6. Star Clusters within FIRE

    Science.gov (United States)

    Perez, Adrianna; Moreno, Jorge; Naiman, Jill; Ramirez-Ruiz, Enrico; Hopkins, Philip F.

    2017-01-01

    In this work, we analyze the environments surrounding star clusters of simulated merging galaxies. Our framework employs Feedback In Realistic Environments (FIRE) model (Hopkins et al., 2014). The FIRE project is a high resolution cosmological simulation that resolves star forming regions and incorporates stellar feedback in a physically realistic way. The project focuses on analyzing the properties of the star clusters formed in merging galaxies. The locations of these star clusters are identified with astrodendro.py, a publicly available dendrogram algorithm. Once star cluster properties are extracted, they will be used to create a sub-grid (smaller than the resolution scale of FIRE) of gas confinement in these clusters. Then, we can examine how the star clusters interact with these available gas reservoirs (either by accreting this mass or blowing it out via feedback), which will determine many properties of the cluster (star formation history, compact object accretion, etc). These simulations will further our understanding of star formation within stellar clusters during galaxy evolution. In the future, we aim to enhance sub-grid prescriptions for feedback specific to processes within star clusters; such as, interaction with stellar winds and gas accretion onto black holes and neutron stars.

  7. Multiplicity of massive stars

    CERN Document Server

    Preibisch, T; Zinnecker, H; Preibisch, Thomas; Weigelt, Gerd; Zinnecker, Hans

    2000-01-01

    We discuss the observed multiplicity of massive stars and implications on theories of massive star formation. After a short summary of the literature on massive star multiplicity, we focus on the O- and B-type stars in the Orion Nebula Cluster, which constitute a homogenous sample of very young massive stars. 13 of these stars have recently been the targets of a bispectrum speckle interferometry survey for companions. Considering the visual and also the known spectroscopic companions of these stars, the total number of companions is at least 14. Extrapolation with correction for the unresolved systems suggests that there are at least 1.5 and perhaps as much as 4 companions per primary star on average. This number is clearly higher than the mean number of about 0.5 companions per primary star found for the low-mass stars in the general field population and also in the Orion Nebula cluster. This suggests that a different mechanism is at work in the formation of high-mass multiple systems in the dense Orion Nebu...

  8. Neutron stars and their magnetic fields

    CERN Document Server

    Reisenegger, Andreas

    2008-01-01

    Neutron stars have the strongest magnetic fields known anywhere in the Universe. In this review, I intend to give a pedagogical discussion of some of the related physics. Neutron stars exist because of Pauli's exclusion principle, in two senses: 1) It makes it difficult to squeeze particles too close together, in this way allowing a mechanical equilibrium state in the presence of extremely strong gravity. 2) The occupation of low-energy proton and electron states makes it impossible for low-energy neutrons to beta decay. A corollary of the second statement is that charged particles are necessarily present inside a neutron star, allowing currents to flow. Since these particles are degenerate, they collide very little, and therefore make it possible for the star to support strong, organized magnetic fields over long times. These show themselves in pulsars and are the most likely energy source for the high X-ray and gamma-ray luminosity ``magnetars''. I briefly discuss the possible origin of this field and some ...

  9. Metastable strange matter and compact quark stars

    CERN Document Server

    Malheiro, M; Taurines, A R

    2003-01-01

    Strange quark matter in beta equilibrium at high densities is studied in a quark confinement model. Two equations of state are dynamically generated for the {\\it same} set of model parameters used to describe the nucleon: one corresponds to a chiral restored phase with almost massless quarks and the other to a chiral broken phase. The chiral symmetric phase saturates at around five times the nuclear matter density. Using the equation of state for this phase, compact bare quark stars are obtained with radii and masses in the ranges $R\\sim 5 - 8$ km and $M\\sim M_\\odot$. The energy per baryon number decreases very slowly from the center of the star to the periphery, remaining above the corresponding values for the iron or the nuclear matter, even at the edge. Our results point out that strange quark matter at very high densities may not be absolutely stable and the existence of an energy barrier between the two phases may prevent the compact quarks stars to decay to hybrid stars.

  10. Dark stars: a review.

    Science.gov (United States)

    Freese, Katherine; Rindler-Daller, Tanja; Spolyar, Douglas; Valluri, Monica

    2016-06-01

    Dark stars are stellar objects made (almost entirely) of hydrogen and helium, but powered by the heat from dark matter annihilation, rather than by fusion. They are in hydrostatic and thermal equilibrium, but with an unusual power source. Weakly interacting massive particles (WIMPs), among the best candidates for dark matter, can be their own antimatter and can annihilate inside the star, thereby providing a heat source. Although dark matter constitutes only [Formula: see text]0.1% of the stellar mass, this amount is sufficient to power the star for millions to billions of years. Thus, the first phase of stellar evolution in the history of the Universe may have been dark stars. We review how dark stars come into existence, how they grow as long as dark matter fuel persists, and their stellar structure and evolution. The studies were done in two different ways, first assuming polytropic interiors and more recently using the MESA stellar evolution code; the basic results are the same. Dark stars are giant, puffy (∼10 AU) and cool (surface temperatures  ∼10 000 K) objects. We follow the evolution of dark stars from their inception at  ∼[Formula: see text] as they accrete mass from their surroundings to become supermassive stars, some even reaching masses  >[Formula: see text] and luminosities  >[Formula: see text], making them detectable with the upcoming James Webb Space Telescope. Once the dark matter runs out and the dark star dies, it may collapse to a black hole; thus dark stars may provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation may exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The current review briefly discusses dark stars existing today, but focuses on the early generation of dark stars.

  11. Dark stars: a review

    Science.gov (United States)

    Freese, Katherine; Rindler-Daller, Tanja; Spolyar, Douglas; Valluri, Monica

    2016-06-01

    Dark stars are stellar objects made (almost entirely) of hydrogen and helium, but powered by the heat from dark matter annihilation, rather than by fusion. They are in hydrostatic and thermal equilibrium, but with an unusual power source. Weakly interacting massive particles (WIMPs), among the best candidates for dark matter, can be their own antimatter and can annihilate inside the star, thereby providing a heat source. Although dark matter constitutes only ≲ 0.1% of the stellar mass, this amount is sufficient to power the star for millions to billions of years. Thus, the first phase of stellar evolution in the history of the Universe may have been dark stars. We review how dark stars come into existence, how they grow as long as dark matter fuel persists, and their stellar structure and evolution. The studies were done in two different ways, first assuming polytropic interiors and more recently using the MESA stellar evolution code; the basic results are the same. Dark stars are giant, puffy (˜10 AU) and cool (surface temperatures  ˜10 000 K) objects. We follow the evolution of dark stars from their inception at  ˜1{{M}⊙} as they accrete mass from their surroundings to become supermassive stars, some even reaching masses  >{{10}6}{{M}⊙} and luminosities  >{{10}10}{{L}⊙} , making them detectable with the upcoming James Webb Space Telescope. Once the dark matter runs out and the dark star dies, it may collapse to a black hole; thus dark stars may provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation may exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The current review briefly discusses dark stars existing today, but focuses on the early generation of dark stars.

  12. Star-Branched Polymers (Star Polymers)

    KAUST Repository

    Hirao, Akira

    2015-09-01

    The synthesis of well-defined regular and asymmetric mixed arm (hereinafter miktoarm) star-branched polymers by the living anionic polymerization is reviewed in this chapter. In particular, much attention is being devoted to the synthetic development of miktoarm star polymers since 2000. At the present time, the almost all types of multiarmed and multicomponent miktoarm star polymers have become feasible by using recently developed iterative strategy. For example, the following well-defined stars have been successfully synthesized: 3-arm ABC, 4-arm ABCD, 5-arm ABCDE, 6-arm ABCDEF, 7-arm ABCDEFG, 6-arm ABC, 9-arm ABC, 12-arm ABC, 13-arm ABCD, 9-arm AB, 17-arm AB, 33-arm AB, 7-arm ABC, 15-arm ABCD, and 31-arm ABCDE miktoarm star polymers, most of which are quite new and difficult to synthesize by the end of the 1990s. Several new specialty functional star polymers composed of vinyl polymer segments and rigid rodlike poly(acetylene) arms, helical polypeptide, or helical poly(hexyl isocyanate) arms are introduced.

  13. Touchstone Stars: Highlights from the Cool Stars 18 Splinter Session

    CERN Document Server

    Mann, Andrew W; Boyajian, Tabetha; Gaidos, Eric; von Braun, Kaspar; Feiden, Gregory A; Metcalfe, Travis; Swift, Jonathan J; Curtis, Jason L; Deacon, Niall R; Filippazzo, Joseph C; Gillen, Ed; Hejazi, Neda; Newton, Elisabeth R

    2014-01-01

    We present a summary of the splinter session on "touchstone stars" -- stars with directly measured parameters -- that was organized as part of the Cool Stars 18 conference. We discuss several methods to precisely determine cool star properties such as masses and radii from eclipsing binaries, and radii and effective temperatures from interferometry. We highlight recent results in identifying and measuring parameters for touchstone stars, and ongoing efforts to use touchstone stars to determine parameters for other stars. We conclude by comparing the results of touchstone stars with cool star models, noting some unusual patterns in the differences.

  14. Beta-thalassemia

    Directory of Open Access Journals (Sweden)

    Origa Raffaella

    2010-05-01

    Full Text Available Abstract Beta-thalassemias are a group of hereditary blood disorders characterized by anomalies in the synthesis of the beta chains of hemoglobin resulting in variable phenotypes ranging from severe anemia to clinically asymptomatic individuals. The total annual incidence of symptomatic individuals is estimated at 1 in 100,000 throughout the world and 1 in 10,000 people in the European Union. Three main forms have been described: thalassemia major, thalassemia intermedia and thalassemia minor. Individuals with thalassemia major usually present within the first two years of life with severe anemia, requiring regular red blood cell (RBC transfusions. Findings in untreated or poorly transfused individuals with thalassemia major, as seen in some developing countries, are growth retardation, pallor, jaundice, poor musculature, hepatosplenomegaly, leg ulcers, development of masses from extramedullary hematopoiesis, and skeletal changes that result from expansion of the bone marrow. Regular transfusion therapy leads to iron overload-related complications including endocrine complication (growth retardation, failure of sexual maturation, diabetes mellitus, and insufficiency of the parathyroid, thyroid, pituitary, and less commonly, adrenal glands, dilated myocardiopathy, liver fibrosis and cirrhosis. Patients with thalassemia intermedia present later in life with moderate anemia and do not require regular transfusions. Main clinical features in these patients are hypertrophy of erythroid marrow with medullary and extramedullary hematopoiesis and its complications (osteoporosis, masses of erythropoietic tissue that primarily affect the spleen, liver, lymph nodes, chest and spine, and bone deformities and typical facial changes, gallstones, painful leg ulcers and increased predisposition to thrombosis. Thalassemia minor is clinically asymptomatic but some subjects may have moderate anemia. Beta-thalassemias are caused by point mutations or, more rarely

  15. Beta-thalassemia.

    Science.gov (United States)

    Galanello, Renzo; Origa, Raffaella

    2010-05-21

    Beta-thalassemias are a group of hereditary blood disorders characterized by anomalies in the synthesis of the beta chains of hemoglobin resulting in variable phenotypes ranging from severe anemia to clinically asymptomatic individuals. The total annual incidence of symptomatic individuals is estimated at 1 in 100,000 throughout the world and 1 in 10,000 people in the European Union. Three main forms have been described: thalassemia major, thalassemia intermedia and thalassemia minor. Individuals with thalassemia major usually present within the first two years of life with severe anemia, requiring regular red blood cell (RBC) transfusions. Findings in untreated or poorly transfused individuals with thalassemia major, as seen in some developing countries, are growth retardation, pallor, jaundice, poor musculature, hepatosplenomegaly, leg ulcers, development of masses from extramedullary hematopoiesis, and skeletal changes that result from expansion of the bone marrow. Regular transfusion therapy leads to iron overload-related complications including endocrine complication (growth retardation, failure of sexual maturation, diabetes mellitus, and insufficiency of the parathyroid, thyroid, pituitary, and less commonly, adrenal glands), dilated myocardiopathy, liver fibrosis and cirrhosis). Patients with thalassemia intermedia present later in life with moderate anemia and do not require regular transfusions. Main clinical features in these patients are hypertrophy of erythroid marrow with medullary and extramedullary hematopoiesis and its complications (osteoporosis, masses of erythropoietic tissue that primarily affect the spleen, liver, lymph nodes, chest and spine, and bone deformities and typical facial changes), gallstones, painful leg ulcers and increased predisposition to thrombosis. Thalassemia minor is clinically asymptomatic but some subjects may have moderate anemia. Beta-thalassemias are caused by point mutations or, more rarely, deletions in the beta

  16. Beta and muon decays

    Energy Technology Data Exchange (ETDEWEB)

    Galindo, A.; Pascual, P.

    1967-07-01

    These notes represent a series of lectures delivered by the authors in the Junta de Energia Nuclear, during the Spring term of 1965. They were devoted to graduate students interested in the Theory of Elementary Particles. Special emphasis was focussed into the computational problems. Chapter I is a review of basic principles (Dirac equation, transition probabilities, final state interactions.) which will be needed later. In Chapter II the four-fermion punctual Interaction is discussed, Chapter III is devoted to the study of beta-decay; the main emphasis is given to the deduction of the formulae corresponding to electron-antineutrino correlation, electron energy spectrum, lifetimes, asymmetry of electrons emitted from polarized nuclei, electron and neutrino polarization and time reversal invariance in beta decay. In Chapter IV we deal with the decay of polarized muons with radiative corrections. Chapter V is devoted to an introduction to C.V.C. theory. (Author)

  17. Realized Beta GARCH

    DEFF Research Database (Denmark)

    Hansen, Peter Reinhard; Lunde, Asger; Voev, Valeri Radkov

    2014-01-01

    We introduce a multivariate generalized autoregressive conditional heteroskedasticity (GARCH) model that incorporates realized measures of variances and covariances. Realized measures extract information about the current levels of volatilities and correlations from high-frequency data, which...... is particularly useful for modeling financial returns during periods of rapid changes in the underlying covariance structure. When applied to market returns in conjunction with returns on an individual asset, the model yields a dynamic model specification of the conditional regression coefficient that is known...... as the beta. We apply the model to a large set of assets and find the conditional betas to be far more variable than usually found with rolling-window regressions based exclusively on daily returns. In the empirical part of the paper, we examine the cross-sectional as well as the time variation...

  18. Coroutine Sequencing in BETA

    DEFF Research Database (Denmark)

    Kristensen, Bent Bruun; Madsen, Ole Lehrmann; Møller-Pedersen, Birger;

    In object-oriented programming, a program execution is viewed as a physical model of some real or imaginary part of the world. A language supporting object-oriented programming must therefore contain comprehensive facilities for modeling phenomena and concepts form the application domain. Many ap...... applications in the real world consist of objects carrying out sequential processes. Coroutines may be used for modeling objects that alternate between a number of sequential processes. The authors describe coroutines in BETA...

  19. Magic Baseline Beta Beam

    CERN Document Server

    Agarwalla, Sanjib Kumar; Raychaudhuri, Amitava

    2007-01-01

    We study the physics reach of an experiment where neutrinos produced in a beta-beam facility at CERN are observed in a large magnetized iron calorimeter (ICAL) at the India-based Neutrino Observatory (INO). The CERN-INO distance is close to the so-called "magic" baseline which helps evade some of the parameter degeneracies and allows for a better measurement of the neutrino mass hierarchy and $\\theta_{13}$.

  20. Beta cell adaptation in pregnancy

    DEFF Research Database (Denmark)

    Nielsen, Jens Høiriis

    2016-01-01

    Pregnancy is associated with a compensatory increase in beta cell mass. It is well established that somatolactogenic hormones contribute to the expansion both indirectly by their insulin antagonistic effects and directly by their mitogenic effects on the beta cells via receptors for prolactin...... and growth hormone expressed in rodent beta cells. However, the beta cell expansion in human pregnancy seems to occur by neogenesis of beta cells from putative progenitor cells rather than by proliferation of existing beta cells. Claes Hellerström has pioneered the research on beta cell growth for decades......, but the mechanisms involved are still not clarified. In this review the information obtained in previous studies is recapitulated together with some of the current attempts to resolve the controversy in the field: identification of the putative progenitor cells, identification of the factors involved...

  1. Regulation of beta cell replication

    DEFF Research Database (Denmark)

    Lee, Ying C; Nielsen, Jens Høiriis

    2008-01-01

    Beta cell mass, at any given time, is governed by cell differentiation, neogenesis, increased or decreased cell size (cell hypertrophy or atrophy), cell death (apoptosis), and beta cell proliferation. Nutrients, hormones and growth factors coupled with their signalling intermediates have been...... suggested to play a role in beta cell mass regulation. In addition, genetic mouse model studies have indicated that cyclins and cyclin-dependent kinases that determine cell cycle progression are involved in beta cell replication, and more recently, menin in association with cyclin-dependent kinase...... inhibitors has been demonstrated to be important in beta cell growth. In this review, we consider and highlight some aspects of cell cycle regulation in relation to beta cell replication. The role of cell cycle regulation in beta cell replication is mostly from studies in rodent models, but whether...

  2. STAR in CTO PCI: When is STAR not a star?

    Science.gov (United States)

    Hira, Ravi S; Dean, Larry S

    2016-04-01

    Subintimal tracking and reentry (STAR) has been used as a bailout strategy and involves an uncontrolled dissection and recanalization into the distal lumen to reestablish vessel patency. In the current study, thrombolysis in myocardial infarction (TIMI) flow < 3 was the only variable which they found to be significantly associated with restenosis and reocclusion after stent placement. It may be reasonable to consider second generation drug eluting stent placement in patients receiving STAR that have TIMI 3 flow, however, this should only be done if there is no compromise of major side branches. If unsure, we recommend to perform balloon angioplasty without stenting.

  3. The First Stars

    Science.gov (United States)

    Yoshida, Naoki

    2010-10-01

    The standard cosmological model predicts that the first cosmological objects are formed when the age of the universe is a few hundred million years. Recent theoretical studies and numerical simulations consistently suggest that the first objects are very massive primordial stars. We introduce the key physics and explain why the first stars are thought to be massive, rather than to be low-mass stars. The state-of-the-art simulations include all the relevant atomic and molecular physics to follow the thermal evolution of a prestellar gas cloud to very high ``stellar'' densities. Evolutionary calculations of the primordial stars suggest the formation of massive blackholes in the early universe. Finally, we show the results from high-resolution simulations of star formation in a low-metallicity gas. Vigorous fragmentation is triggered in a star-forming gas cloud at a metallicity of as low as Z = 10-5Zsolar.

  4. LHCb: $2\\beta_s$ measurement at LHCb

    CERN Multimedia

    Conti, G

    2009-01-01

    A measurement of $2\\beta_s$, the phase of the $B_s-\\bar{B_s}$ oscillation amplitude with respect to that of the ${\\rm b} \\rightarrow {\\rm c^{+}}{\\rm W^{-}}$ tree decay amplitude, is one of the key goals of the LHCb experiment with first data. In the Standard Model (SM), $2\\beta_s$ is predicted to be $0.0360^{+0.0020}_{-0.0016} \\rm rad$. The current constraints from the Tevatron are: $2\\beta_{s}\\in[0.32 ; 2.82]$ at 68$\\%$CL from the CDF experiment and $2\\beta_{s}=0.57^{+0.24}_{-0.30}$ from the D$\\oslash$ experiment. Although the statistical uncertainties are large, these results hint at the possible contribution of New Physics in the $B_s-\\bar{B_s}$ box diagram. After one year of data taking at LHCb at an average luminosity of $\\mathcal{L}\\sim2\\cdot10^{32}\\rm cm^{-2} \\rm s^{-1}$ (integrated luminosity $\\mathcal{L}_{\\rm int}\\sim 2 \\rm fb^{-1}$), the expected statistical uncertainty on the measurement is $\\sigma(2\\beta_s)\\simeq 0.03$. This uncertainty is similar to the $2\\beta_s$ value predicted by the SM.

  5. Strange nonchaotic stars

    CERN Document Server

    Lindner, John F; Kia, Behnam; Hippke, Michael; Learned, John G; Ditto, William L

    2015-01-01

    The unprecedented light curves of the Kepler space telescope document how the brightness of some stars pulsates at primary and secondary frequencies whose ratios are near the golden mean, the most irrational number. A nonlinear dynamical system driven by an irrational ratio of frequencies generically exhibits a strange but nonchaotic attractor. For Kepler's "golden" stars, we present evidence of the first observation of strange nonchaotic dynamics in nature outside the laboratory. This discovery could aid the classification and detailed modeling of variable stars.

  6. Interacting binary stars

    CERN Document Server

    Sahade, Jorge; Ter Haar, D

    1978-01-01

    Interacting Binary Stars deals with the development, ideas, and problems in the study of interacting binary stars. The book consolidates the information that is scattered over many publications and papers and gives an account of important discoveries with relevant historical background. Chapters are devoted to the presentation and discussion of the different facets of the field, such as historical account of the development in the field of study of binary stars; the Roche equipotential surfaces; methods and techniques in space astronomy; and enumeration of binary star systems that are studied

  7. Strange Nonchaotic Stars

    Science.gov (United States)

    Lindner, John F.; Kohar, Vivek; Kia, Behnam; Hippke, Michael; Learned, John G.; Ditto, William L.

    2015-08-01

    Exploiting the unprecedented capabilities of the planet-hunting Kepler space telescope, which stared at 150 000 stars for four years, we discuss recent evidence that certain stars dim and brighten in complex patterns with fractal features. Such stars pulsate at primary and secondary frequencies whose ratios are near the famous golden mean, the most irrational number. A nonlinear system driven by an irrational ratio of frequencies is generically attracted toward a “strange” behavior that is geometrically fractal without displaying the “butterfly effect” of chaos. Strange nonchaotic attractors have been observed in laboratory experiments and have been hypothesized to describe the electrochemical activity of the brain, but a bluish white star 16 000 light years from Earth in the constellation Lyra may manifest, in the scale-free distribution of its minor frequency components, the first strange nonchaotic attractor observed in the wild. The recognition of stellar strange nonchaotic dynamics may improve the classification of these stars and refine the physical modeling of their interiors. We also discuss nonlinear analysis of other RR Lyrae stars in Kepler field of view and discuss some toy models for modeling these stars.References: 1) Hippke, Michael, et al. "Pulsation period variations in the RRc Lyrae star KIC 5520878." The Astrophysical Journal 798.1 (2015): 42.2) Lindner, John F., et al. "Strange nonchaotic stars." Phys. Rev. Lett. 114, 054101 (2015)

  8. ENERGY STAR Unit Reports

    Data.gov (United States)

    Department of Housing and Urban Development — These quarterly Federal Fiscal Year performance reports track the ENERGY STAR qualified HOME units that Participating Jurisdictions record in HUD's Integrated...

  9. Horizontal Branch stars as AmFm/HgMn stars

    CERN Document Server

    Michaud, G

    2008-01-01

    Recent observations and models for horizontal branch stars are briefly described and compared to models for AmFm stars. The limitations of those models are emphasized by a comparison to observations and models for HgMn stars.

  10. Oscillations in Beta UMi - Observations with SMEI

    CERN Document Server

    Tarrant, N J; Elsworth, Y; Spreckley, S A; Stevens, I R

    2008-01-01

    Aims: From observations of the K4III star Beta UMi we attempt to determine whether oscillations or any other form of variability is present. Methods: A high-quality photometric time series of approximately 1000 days in length obtained from the SMEI instrument on the Coriolis satellite is analysed. Various statistical tests were performed to determine the significance of features seen in the power density spectrum of the light curve. Results: Two oscillations with frequencies 2.44 and 2.92 microhertz have been identified. We interpret these oscillations as consecutive overtones of an acoustic spectrum, implying a large frequency spacing of 0.48 microhertz. Using derived asteroseismic parameters in combination with known astrophysical parameters, we estimate the mass of Beta UMi to be 1.3 +/- 0.3 solar masses. Peaks of the oscillations in the power density spectrum show width, implying that modes are stochastically excited and damped by convection. The mode lifetime is estimated at 18 +/- 9 days.

  11. 3D-HST Emission Line Galaxies at z ~ 2: Discrepancies in the Optical/UV Star Formation Rates

    CERN Document Server

    Zeimann, Gregory R; Gebhardt, Henry; Gronwall, Caryl; Schneider, Donald P; Hagen, Alex; Bridge, Joanna S; Feldmeier, John; Trump, Jonathan R

    2014-01-01

    We use Hubble Space Telescope near-IR grism spectroscopy to examine the H-beta line strengths of 260 star-forming galaxies in the redshift range 1.90 < z < 2.35. We show that at these epochs, the H-beta star formation rate (SFR) is a factor of ~1.8 higher than what would be expected from the systems' rest-frame UV flux density, suggesting a shift in the standard conversion between these quantities and star formation rate. We demonstrate that at least part of this shift can be attributed to metallicity, as H-beta is more greatly enhanced in systems with lower oxygen abundance. This offset must be considered when measuring the star formation rate history of the universe. We also show that the relation between stellar and nebular extinction in our z ~ 2 sample is consistent with that observed in the local universe.

  12. Star Trek in the Schools

    Science.gov (United States)

    Journal of Aerospace Education, 1977

    1977-01-01

    Describes specific educational programs for using the Star Trek TV program from kindergarten through college. For each grade level lesson plans, ideas for incorporating Star Trek into future classes, and reports of specific programs utilizing Star Trek are provided. (SL)

  13. Stars and Flowers, Flowers and Stars

    Science.gov (United States)

    Minti, Hari

    2012-12-01

    The author, a graduated from the Bucharest University (1964), actually living and working in Israel, concerns his book to variable stars and flowers, two domains of his interest. The analogies includes double stars, eclipsing double stars, eclipses, Big Bang. The book contains 34 chapters, each of which concerns various relations between astronomy and other sciences and pseudosciences such as Psychology, Religion, Geology, Computers and Astrology (to which the author is not an adherent). A special part of the book is dedicated to archeoastronomy and ethnoastronomy, as well as to history of astronomy. Between the main points of interest of these parts: ancient sanctuaries in Sarmizegetusa (Dacia), Stone Henge(UK) and other. The last chapter of the book is dedicated to flowers. The book is richly illustrated. It is designed for a wide circle of readers.

  14. Physical and orbital properties of Beta Pictoris b

    CERN Document Server

    Bonnefoy, M; Galicher, R; Beust, H; Lagrange, A -M; Baudino, J -L; Chauvin, G; Borgniet, S; Meunier, N; Rameau, J; Boccaletti, A; Cumming, A; Helling, C; Homeier, D; Allard, F; Delorme, P

    2014-01-01

    The intermediate-mass star Beta Pictoris is known to be surrounded by a structured edge-on debris disk within which a gas giant planet was discovered orbiting at 8-10 AU. The physical properties of Beta Pic b were previously inferred from broad and narrow-band 0.9-4.8 microns photometry. We used commissioning data of the Gemini Planet Imager (GPI) to obtain new astrometry and a low-resolution (R=35-39) J-band (1.12-1.35 microns) spectrum of the planet. We find that the planet has passed the quadrature. We constrain its semi-major axis to $\\leq$ 10 AU (90 % prob.) with a peak at 8.9+0.4-0.6 AU. The joint fit of the planet astrometry and the most recent radial velocity measurements of the star yields a planet's dynamical mass $\\leq$ 20 MJup (greater than 96 % prob.). The extracted spectrum of Beta Pic b is similar to those of young L1-1.5+1 dwarfs. We use the spectral type estimate to revise the planet luminosity to log(L/Lsun)=-3.90+-0.07. The 0.9-4.8 microns photometry and spectrum are reproduced for Teff=165...

  15. Star Formation Law in the Milky Way

    CERN Document Server

    Sofue, Yoshiaki

    2016-01-01

    The Schmidt law (SF law) in the Milky Way was investigated using 3D distribution maps of HII regions, HI and molecular (\\Htwo) gases with spatial resolutions of $\\sim 1$ kpc in the Galactic plane and a few tens of pc in the vertical direction. HII regions were shown to be distributed in a star-forming (SF) disk with nearly constant vertical full thickness 92 pc in spatial coincidence with the molecular gas disk. The vertically averaged volume star formation rate (SFR) $\\rho_{\\rm SFR}$ in the SF disk is related to the surface SFR $\\Sigma_{\\rm SFR}$ by $\\rho_{\\rm SFR} /[{\\rm M_\\odot y^{-1} kpc^{-3}}] =9.26\\times \\Sigma_{\\rm SFR}/[{\\rm M_\\odot y^{-1} kpc^{-2}}]$. The SF law fitted by a single power law of gas density in the form of $\\Sigma_{\\rm SFR} \\propto \\rho_{\\rm SFR} \\propto \\rho_{\\rm gas}^\\alpha$ and $\\propto \\Sigma_{\\rm gas}^\\beta$ showed indices of $\\alpha=0.78 \\pm 0.05$ for $\\rho_{\\rm H_2}$ and $2.15 \\pm 0.08$ for $\\rho_{\\rm total}$, and $\\beta=1.14\\pm 0.23$ for $\\Sigma_{\\rm total}$, where $\\rho$ and $\\...

  16. PAHs and star formation

    NARCIS (Netherlands)

    Tielens, AGGM; Peeters, E; Bakes, ELO; Spoon, HWW; Hony, S; Johnstone, D; Adams, FC; Lin, DNC; Neufeld, DA; Ostriker, EC

    2004-01-01

    Strong IR emission features at 3.3, 6.2, 7.7, 8.6, and 11.2 mum are a common characteristic of regions of massive star formation. These features are carried by large (similar to 50 C-atom) Polycyclic Aromatic Hydrocarbon molecules which are pumped by the strong FUV photon flux from these stars. Thes

  17. Observing Double Stars

    Science.gov (United States)

    Genet, Russell M.; Fulton, B. J.; Bianco, Federica B.; Martinez, John; Baxter, John; Brewer, Mark; Carro, Joseph; Collins, Sarah; Estrada, Chris; Johnson, Jolyon; Salam, Akash; Wallen, Vera; Warren, Naomi; Smith, Thomas C.; Armstrong, James D.; McGaughey, Steve; Pye, John; Mohanan, Kakkala; Church, Rebecca

    2012-05-01

    Double stars have been systematically observed since William Herschel initiated his program in 1779. In 1803 he reported that, to his surprise, many of the systems he had been observing for a quarter century were gravitationally bound binary stars. In 1830 the first binary orbital solution was obtained, leading eventually to the determination of stellar masses. Double star observations have been a prolific field, with observations and discoveries - often made by students and amateurs - routinely published in a number of specialized journals such as the Journal of Double Star Observations. All published double star observations from Herschel's to the present have been incorporated in the Washington Double Star Catalog. In addition to reviewing the history of visual double stars, we discuss four observational technologies and illustrate these with our own observational results from both California and Hawaii on telescopes ranging from small SCTs to the 2-meter Faulkes Telescope North on Haleakala. Two of these technologies are visual observations aimed primarily at published "hands-on" student science education, and CCD observations of both bright and very faint doubles. The other two are recent technologies that have launched a double star renaissance. These are lucky imaging and speckle interferometry, both of which can use electron-multiplying CCD cameras to allow short (30 ms or less) exposures that are read out at high speed with very low noise. Analysis of thousands of high speed exposures allows normal seeing limitations to be overcome so very close doubles can be accurately measured.

  18. Ages of young stars

    CERN Document Server

    Soderblom, David R; Jeffries, Rob D; Mamajek, Eric E; Naylor, Tim

    2013-01-01

    Determining the sequence of events in the formation of stars and planetary systems and their time-scales is essential for understanding those processes, yet establishing ages is fundamentally difficult because we lack direct indicators. In this review we discuss the age challenge for young stars, specifically those less than ~100 Myr old. Most age determination methods that we discuss are primarily applicable to groups of stars but can be used to estimate the age of individual objects. A reliable age scale is established above 20 Myr from measurement of the Lithium Depletion Boundary (LDB) in young clusters, and consistency is shown between these ages and those from the upper main sequence and the main sequence turn-off -- if modest core convection and rotation is included in the models of higher-mass stars. Other available methods for age estimation include the kinematics of young groups, placing stars in Hertzsprung-Russell diagrams, pulsations and seismology, surface gravity measurement, rotation and activ...

  19. Gaia and Variable Stars

    CERN Document Server

    Udalski, A; Skowron, D M; Skowron, J; Pietrukowicz, P; Mróz, P; Poleski, R; Szymański, M K; Kozłowski, S; Wyrzykowski, Ł; Ulaczyk, K; Pawlak, M

    2016-01-01

    We present a comparison of the Gaia DR1 samples of pulsating variable stars - Cepheids and RR Lyrae type - with the OGLE Collection of Variable Stars aiming at the characterization of the Gaia mission performance in the stellar variability domain. Out of 575 Cepheids and 2322 RR Lyrae candidates from the Gaia DR1 samples located in the OGLE footprint in the sky, 559 Cepheids and 2302 RR Lyrae stars are genuine pulsators of these types. The number of misclassified stars is low indicating reliable performance of the Gaia data pipeline. The completeness of the Gaia DR1 samples of Cepheids and RR Lyrae stars is at the level of 60-75% as compared to the OGLE Collection dataset. This level of completeness is moderate and may limit the applicability of the Gaia data in many projects.

  20. Revised Anatomy of Stars

    CERN Document Server

    Dubin, M; Dubin, Maurice; Soberman, Robert K.

    1997-01-01

    Stars accrete near invisible hydrogen dominated agglomerates. This population, the `dark matter,' effects the nature of stars. Measurements show plasma streams impacting Earth, planets, Sun and stars. This mass-energy source contradicts nebula collapse model for stars. The visual derived model, to which later discoveries (e.g., fusion) were appended, is confounded and contradicted by new observations. Discovery of a quantity of beryllium 7 (53 day half-life) in the Earth's upper atmosphere, fusion produced, hence from the solar outer zone, proves core fusion wrong. Magnetically pinched plasmas from aggregates impact stars at hundreds of km/s, create impulsive conditions for nuclear explosions below the surface. Disks with planets aid cluster capture. Planets modulate the influx varying fusion, hence luminosity (e.g., solar cycle). This population, with no assumptions or ad hoc physics, explains mysterious phenomena, e.g., luminosity/wind variation, sunspots, high temperature corona, CMEs, etc. Standard explan...

  1. Mira Symbiotic Stars

    Institute of Scientific and Technical Information of China (English)

    Guo-Liang Lü; Chun-Hua Zhu; Zhan-Wen Han

    2007-01-01

    We have carried out a detailed study of Mira symbiotic stars by means of a population synthesis code. We estimate the number of Mira symbiotic stars in the Galaxy as 1700 - 3100 and the Galactic occurrence rate of Mira symbiotic novae as from ~ 0.9 to 6.0 yr-1,depending on the model assumptions. The distributions of the orbital periods, the masses of the components, mass-loss rates of cool components, mass-accretion rates of hot components and Mira pulsation periods in Mira symbiotic stars are simulated. By a comparison of the number ratio of Mira symbiotic stars to all symbiotic stars, we find the model with the stellar wind model of Winters et al. to be reasonable.

  2. Producing Runaway Stars

    Science.gov (United States)

    Kohler, Susanna

    2016-07-01

    How are the hypervelocity stars weve observed in our galaxy produced? A recent study suggests that these escapees could be accelerated by a massive black hole in the center of the Large Magellanic Cloud.A Black Hole SlingshotSince their discovery in 2005, weve observed dozens of candidate hypervelocity stars stars whose velocity in the rest frame of our galaxy exceeds the local escape velocity of the Milky Way. These stars present a huge puzzle: how did they attain these enormous velocities?One potential explanation is known as the Hills mechanism. In this process, a stellar binary is disrupted by a close encounter with a massive black hole (like those thought to reside at the center of every galaxy). One member of the binary is flung out of the system as a result of the close encounter, potentially reaching very large velocities.A star-forming region known as LHA 120-N 11, located within the LMC. Some binary star systems within the LMC might experience close encounters with a possible massive black hole at the LMCs center. [ESA/NASA/Hubble]Blame the LMC?Usually, discussions of the Hills mechanism assume that Sagittarius A*, the supermassive black hole at the center of the Milky Way, is the object guilty of accelerating the hypervelocity stars weve observed. But what if the culprit isnt Sgr A*, but a massive black hole at the center of the Large Magellanic Cloud (LMC), one of the Milky Ways satellite galaxies?Though we dont yet have evidence of a massive black hole at the center of the LMC, the dwarf galaxy is large enough to potentially host one as large as 100,000 solar masses. Assuming that it does, two scientists at the University of Cambridge, Douglas Boubert and Wyn Evans, have now modeled how this black hole might tear apart binary star systems and fling hypervelocity stars around the Milky Way.Models for AccelerationBoubert and Evans determined that the LMCs hypothetical black hole could easily eject stars at ~100 km/s, which is the escape velocity of the

  3. The Carbon Star Phenomenon

    Science.gov (United States)

    Wing, Robert F.

    2000-06-01

    The atmospheres of many stars have chemical compositions that are significantly different from that of the interstellar medium from which they are formed. This symposium considered all kinds of late-type stars showing altered compositions, the carbon stars being simply the best-known of these. All stages of stellar evolution from the main sequence to the ejection of a planetary nebula were considered, with emphasis on the changes that occur on the asymptotic giant branch. The spectroscopic properties of the photospheres and circumstellar envelopes of chemically-peculiar red giant stars, their origins via single-star evolution or mass transfer in binary systems, and the methods currently used to study them were all discussed in detail. This volume includes the full texts of papers given orally at the symposium and abstracts of the posters. Link: http://www.wkap.nl/book.htm/0-7923-6347-7

  4. Neutron Stars and Pulsars

    CERN Document Server

    Becker, Werner

    2009-01-01

    Neutron stars are the most compact astronomical objects in the universe which are accessible by direct observation. Studying neutron stars means studying physics in regimes unattainable in any terrestrial laboratory. Understanding their observed complex phenomena requires a wide range of scientific disciplines, including the nuclear and condensed matter physics of very dense matter in neutron star interiors, plasma physics and quantum electrodynamics of magnetospheres, and the relativistic magneto-hydrodynamics of electron-positron pulsar winds interacting with some ambient medium. Not to mention the test bed neutron stars provide for general relativity theories, and their importance as potential sources of gravitational waves. It is this variety of disciplines which, among others, makes neutron star research so fascinating, not only for those who have been working in the field for many years but also for students and young scientists. The aim of this book is to serve as a reference work which not only review...

  5. Monte Carlo simulation of star/linear and star/star blends with chemically identical monomers

    Energy Technology Data Exchange (ETDEWEB)

    Theodorakis, P E [Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina (Greece); Avgeropoulos, A [Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina (Greece); Freire, J J [Departamento de Ciencias y Tecnicas FisicoquImicas, Universidad Nacional de Educacion a Distancia, Facultad de Ciencias, Senda del Rey 9, 28040 Madrid (Spain); Kosmas, M [Department of Chemistry, University of Ioannina, 45110 Ioannina (Greece); Vlahos, C [Department of Chemistry, University of Ioannina, 45110 Ioannina (Greece)

    2007-11-21

    The effects of chain size and architectural asymmetry on the miscibility of blends with chemically identical monomers, differing only in their molecular weight and architecture, are studied via Monte Carlo simulation by using the bond fluctuation model. Namely, we consider blends composed of linear/linear, star/linear and star/star chains. We found that linear/linear blends are more miscible than the corresponding star/star mixtures. In star/linear blends, the increase in the volume fraction of the star chains increases the miscibility. For both star/linear and star/star blends, the miscibility decreases with the increase in star functionality. When we increase the molecular weight of linear chains of star/linear mixtures the miscibility decreases. Our findings are compared with recent analytical and experimental results.

  6. Simultaneous beta and gamma spectroscopy

    Science.gov (United States)

    Farsoni, Abdollah T.; Hamby, David M.

    2010-03-23

    A phoswich radiation detector for simultaneous spectroscopy of beta rays and gamma rays includes three scintillators with different decay time characteristics. Two of the three scintillators are used for beta detection and the third scintillator is used for gamma detection. A pulse induced by an interaction of radiation with the detector is digitally analyzed to classify the type of event as beta, gamma, or unknown. A pulse is classified as a beta event if the pulse originated from just the first scintillator alone or from just the first and the second scintillator. A pulse from just the third scintillator is recorded as gamma event. Other pulses are rejected as unknown events.

  7. Beta section Beta: biogeographical patterns of variation and taxonomy.

    NARCIS (Netherlands)

    Letschert, J.P.W.

    1993-01-01

    In Chapter 1 an account is given of the historical subdivision of the genus Beta and its sections, and the relations of the sections are discussed. Emphasis is given to the taxonomic treatment of wild section Beta by various authors. The Linnaean names B. vulgaris L. and B. maritima L. are lectotypi

  8. Catch a Star!

    Science.gov (United States)

    2006-11-01

    ESO and the European Association for Astronomy Education are launching today the 2007 edition of 'Catch a Star!', their international astronomy competition for school students. Now in its fifth year, the competition offers students the chance to win a once-in-a-lifetime trip to ESO's flagship observatory in Chile, as well as many other prizes. Students are invited to 'become astronomers' and embark on a journey to explore the Universe. ESO PR Photo 42/06 The competition includes separate categories - 'Catch a Star Researchers' and 'Catch a Star Adventurers' - to ensure that every student, whatever their level, has the chance to enter and win exciting prizes. For the artistically minded, 'Catch a Star!' also includes an artwork competition, 'Catch a Star Artists'. "'Catch a Star!' offers a unique opportunity for students to learn more about astronomy and about the methods scientists use to discover new things about the Universe", said Douglas Pierce-Price, Education Officer at ESO. In teams, students choose an astronomical topic to study and produce an in-depth report. An important part of the project for 'Catch a Star Researchers' is to think about how ESO's telescopes or a telescope of the future can contribute to their investigations of the subject. As well as the top prize - a trip to one of ESO's observatory sites in Chile - visits to observatories in Germany, Austria and Spain, and many other prizes are also available to be won. 'Catch a Star Researchers' winners will be chosen by an international jury, and 'Catch a Star Adventurers' will be awarded further prizes by lottery. Entries for 'Catch a Star Artists' will be displayed on the web and winners chosen with the help of a public online vote. The first editions of 'Catch a Star!' have attracted several hundred entries from more than 25 countries worldwide. Previous winning entries have included "Star clusters and the structure of the Milky Way" (Budapest, Hungary), "Vega" (Acqui Terme, Italy) and "Venus

  9. Cyclic modular beta-sheets.

    Science.gov (United States)

    Woods, R Jeremy; Brower, Justin O; Castellanos, Elena; Hashemzadeh, Mehrnoosh; Khakshoor, Omid; Russu, Wade A; Nowick, James S

    2007-03-07

    The development of peptide beta-hairpins is problematic, because folding depends on the amino acid sequence and changes to the sequence can significantly decrease folding. Robust beta-hairpins that can tolerate such changes are attractive tools for studying interactions involving protein beta-sheets and developing inhibitors of these interactions. This paper introduces a new class of peptide models of protein beta-sheets that addresses the problem of separating folding from the sequence. These model beta-sheets are macrocyclic peptides that fold in water to present a pentapeptide beta-strand along one edge; the other edge contains the tripeptide beta-strand mimic Hao [JACS 2000, 122, 7654] and two additional amino acids. The pentapeptide and Hao-containing peptide strands are connected by two delta-linked ornithine (deltaOrn) turns [JACS 2003, 125, 876]. Each deltaOrn turn contains a free alpha-amino group that permits the linking of individual modules to form divalent beta-sheets. These "cyclic modular beta-sheets" are synthesized by standard solid-phase peptide synthesis of a linear precursor followed by solution-phase cyclization. Eight cyclic modular beta-sheets 1a-1h containing sequences based on beta-amyloid and macrophage inflammatory protein 2 were synthesized and characterized by 1H NMR. Linked cyclic modular beta-sheet 2, which contains two modules of 1b, was also synthesized and characterized. 1H NMR studies show downfield alpha-proton chemical shifts, deltaOrn delta-proton magnetic anisotropy, and NOE cross-peaks that establish all compounds but 1c and 1g to be moderately or well folded into a conformation that resembles a beta-sheet. Pulsed-field gradient NMR diffusion experiments show little or no self-association at low (

  10. Hot Subluminous Stars

    Science.gov (United States)

    Heber, U.

    2016-08-01

    Hot subluminous stars of spectral type B and O are core helium-burning stars at the blue end of the horizontal branch or have evolved even beyond that stage. Most hot subdwarf stars are chemically highly peculiar and provide a laboratory to study diffusion processes that cause these anomalies. The most obvious anomaly lies with helium, which may be a trace element in the atmosphere of some stars (sdB, sdO) while it may be the dominant species in others (He-sdB, He-sdO). Strikingly, the distribution in the Hertzsprung-Russell diagram of He-rich versus He-poor hot subdwarf stars of the globular clusters ω Cen and NGC 2808 differ from that of their field counterparts. The metal-abundance patterns of hot subdwarfs are typically characterized by strong deficiencies of some lighter elements as well as large enrichments of heavy elements. A large fraction of sdB stars are found in close binaries with white dwarf or very low-mass main sequence companions, which must have gone through a common-envelope (CE) phase of evolution. Because the binaries are detached they provide a clean-cut laboratory to study this important but yet poorly understood phase of stellar evolution. Hot subdwarf binaries with sufficiently massive white dwarf companions are viable candidate progenitors of type Ia supernovae both in the double degenerate as well as in the single degenerate scenario as helium donors for double detonation supernovae. The hyper-velocity He-sdO star US 708 may be the surviving donor of such a double detonation supernova. Substellar companions to sdB stars have also been found. For HW Vir systems the companion mass distribution extends from the stellar into the brown dwarf regime. A giant planet to the acoustic-mode pulsator V391 Peg was the first discovery of a planet that survived the red giant evolution of its host star. Evidence for Earth-size planets to two pulsating sdB stars have been reported and circumbinary giant planets or brown dwarfs have been found around HW

  11. Dense Axion Stars

    CERN Document Server

    Braaten, Eric; Zhang, Hong

    2015-01-01

    If the dark matter consists of axions, gravity can cause them to coalesce into axion stars, which are stable gravitationally bound Bose-Einstein condensates of axions. In the previously known axion stars, gravity and the attractive force between pairs of axions are balanced by the kinetic pressure.If the axion mass energy is $mc^2= 10^{-4}$ eV, these dilute axion stars have a maximum mass of about $10^{-14} M_\\odot$. We point out that there are also dense axion stars in which gravity is balanced by the mean-field pressure of the axion condensate. We study axion stars using the leading term in a systematically improvable approximation to the effective potential of the nonrelativistic effective field theory for axions. Using the Thomas-Fermi approximation in which the kinetic pressure is neglected, we find a sequence of new branches of axion stars in which gravity is balanced by the mean-field interaction energy of the axion condensate. If $mc^2 = 10^{-4}$ eV, the first branch of these dense axion stars has mas...

  12. Dense Axion Stars

    Science.gov (United States)

    Braaten, Eric; Mohapatra, Abhishek; Zhang, Hong

    2016-09-01

    If the dark matter particles are axions, gravity can cause them to coalesce into axion stars, which are stable gravitationally bound systems of axions. In the previously known solutions for axion stars, gravity and the attractive force between pairs of axions are balanced by the kinetic pressure. The mass of these dilute axion stars cannot exceed a critical mass, which is about 10-14M⊙ if the axion mass is 10-4 eV . We study axion stars using a simple approximation to the effective potential of the nonrelativistic effective field theory for axions. We find a new branch of dense axion stars in which gravity is balanced by the mean-field pressure of the axion Bose-Einstein condensate. The mass on this branch ranges from about 10-20M⊙ to about M⊙ . If a dilute axion star with the critical mass accretes additional axions and collapses, it could produce a bosenova, leaving a dense axion star as the remnant.

  13. Dense Axion Stars

    Science.gov (United States)

    Mohapatra, Abhishek; Braaten, Eric; Zhang, Hong

    2016-03-01

    If the dark matter consists of axions, gravity can cause them to coalesce into axion stars, which are stable gravitationally bound Bose-Einstein condensates of axions. In the previously known axion stars, gravity and the attractive force between pairs of axions are balanced by the kinetic pressure. If the axion mass energy is mc2 =10-4 eV, these dilute axion stars have a maximum mass of about 10-14M⊙ . We point out that there are also dense axion stars in which gravity is balanced by the mean-field pressure of the axion condensate. We study axion stars using the leading term in a systematically improvable approximation to the effective potential of the nonrelativistic effective field theory for axions. Using the Thomas-Fermi approximation in which the kinetic pressure is neglected, we find a sequence of new branches of axion stars in which gravity is balanced by the mean-field interaction energy of the axion condensate. If mc2 =10-4 4 eV, the first branch of these dense axion stars has mass ranging from about 10-11M⊙ toabout M⊙.

  14. Cooling of Neutron Stars

    Directory of Open Access Journals (Sweden)

    Grigorian H.

    2010-10-01

    Full Text Available We introduce the theoretical basis for modeling the cooling evolution of compact stars starting from Boltzmann equations in curved space-time. We open a discussion on observational verification of different neutron star models by consistent statistics. Particular interest has the question of existence of quark matter deep inside of compact object, which has to have a specific influence on the cooling history of the star. Besides of consideration of several constraints and features of cooling evolution, which are susceptible of being critical for internal structure of hot compact stars we have introduced a method of extraction of the mass distribution of the neutron stars from temperature and age data. The resulting mass distribution has been compared with the one suggested by supernove simulations. This method can be considered as an additional checking tool for the consistency of theoretical modeling of neutron stars. We conclude that the cooling data allowed existence of neutron stars with quark cores even with one-flavor quark matter.

  15. Relativistic Stars in Beyond Horndeski Theories

    CERN Document Server

    Babichev, Eugeny; Langlois, David; Saito, Ryo; Sakstein, Jeremy

    2016-01-01

    This work studies relativistic stars in beyond Horndeski scalar-tensor theories that exhibit a breaking of the Vainshtein mechanism inside matter, focusing on a model based on the quartic beyond Horndeski Lagrangian. We self-consistently derive the scalar field profile for static spherically symmetric objects in asymptotically de Sitter space-time and show that the Vainshtein breaking branch of the solutions is the physical branch thereby resolving several ambiguities with non-relativistic frameworks. The geometry outside the star is shown to be exactly Schwarzschild-de Sitter and therefore the PPN parameter $\\beta_{\\rm PPN}=1$, confirming that the external screening works at the post-Newtonian level. The Tolman-Oppenheimer-Volkoff (TOV) equations are derived and a new lower bound on the Vainshtein breaking parameter $\\Upsilon_1>-4/9$ is found by requiring the existence of static spherically symmetric stars. Focusing on the unconstrained case where $\\Upsilon_1<0$, we numerically solve the TOV equations for...

  16. The Polaris Project / NorthStar implementation

    Science.gov (United States)

    Willson, L. A.; Bennett, D. H.; Engelhaupt, T.

    2001-12-01

    The advent of the World Wide Web opens new opportunities for education; it also changes the environment within which we teach. As Marshall McLuhan said many years ago: "The medium is the message". What kind of medium is the Web, and how is it best harnessed for use in astronomy education? We are developing a sequence of one-credit web-based courses covering basic astronomical topics as a means of exploring what the web can and cannot do. Our first course, NorthStar, deals with coordinates, sky motions, and navigation by the stars. It has been through "beta testing" and is being offered as an experimental course for spring. Our second course, EveningStar, is under development. The course materials are open and may be used as a supplement to any course, or for independent study; the homework, discussion group, and other human-intervention features require a student to register for the course. We invite people to make use of our open materials and, in exchange, to provide us with feedback about how well it works. We acknowledge support for this project from NASA (NAG 58465) and the Department of Physics and Astronomy, Iowa State University.

  17. Symbiotic Stars in X-rays

    Science.gov (United States)

    Luna, G. J. M.; Sokoloski, J. L.; Mukai, K.; Nelson, T.

    2014-01-01

    Until recently, symbiotic binary systems in which a white dwarf accretes from a red giant were thought to be mainly a soft X-ray population. Here we describe the detection with the X-ray Telescope (XRT) on the Swift satellite of 9 white dwarf symbiotics that were not previously known to be X-ray sources and one that was previously detected as a supersoft X-ray source. The 9 new X-ray detections were the result of a survey of 41 symbiotic stars, and they increase the number of symbiotic stars known to be X-ray sources by approximately 30%. Swift/XRT detected all of the new X-ray sources at energies greater than 2 keV. Their X-ray spectra are consistent with thermal emission and fall naturally into three distinct groups. The first group contains those sources with a single, highly absorbed hard component, which we identify as probably coming from an accretion-disk boundary layer. The second group is composed of those sources with a single, soft X-ray spectral component, which likely arises in a region where low-velocity shocks produce X-ray emission, i.e. a colliding-wind region. The third group consists of those sources with both hard and soft X-ray spectral components. We also find that unlike in the optical, where rapid, stochastic brightness variations from the accretion disk typically are not seen, detectable UV flickering is a common property of symbiotic stars. Supporting our physical interpretation of the two X-ray spectral components, simultaneous Swift UV photometry shows that symbiotic stars with harder X-ray emission tend to have stronger UV flickering, which is usually associated with accretion through a disk. To place these new observations in the context of previous work on X-ray emission from symbiotic stars, we modified and extended the alpha/beta/gamma classification scheme for symbiotic-star X-ray spectra that was introduced by Muerset et al. based upon observations with the ROSAT satellite, to include a new sigma classification for sources with

  18. Quark matter nucleation in neutron stars and astrophysical implications

    CERN Document Server

    Bombaci, Ignazio; Vidana, Isaac; Providencia, Constanca

    2016-01-01

    A phase of strong interacting matter with deconfined quarks is expected in the core of massive neutron stars. We investigate the quark deconfinement phase transition in cold (T = 0) and hot beta-stable hadronic matter. Assuming a first order phase transition, we calculate and compare the nucleation rate and the nucleation time due to quantum and thermal nucleation mechanisms. We show that above a threshold value of the central pressure a pure hadronic star (HS) (i.e. a compact star with no fraction of deconfined quark matter) is metastable to the conversion to a quark star (QS) (i.e. a hybrid star or a strange star). This process liberates an enormous amount of energy, of the order of 10^{53}~erg, which causes a powerful neutrino burst, likely accompanied by intense gravitational waves emission, and possibly by a second delayed (with respect to the supernova explosion forming the HS) explosion which could be the energy source of a powerful gamma-ray burst (GRB). This stellar conversion process populates the Q...

  19. Wind Circulation in Selected Rotating Magnetic Early-B Stars

    CERN Document Server

    Smith, M A; Smith, Myron A.; Groote, Detlef

    2001-01-01

    The rotating magnetic B stars have oblique dipolar magnetic fields and often anomalous helium and metallic compositions. These stars develop co-rotating torus-shaped clouds by channelling winds from their magnetic poles to an anchored planar disk over the magnetic equator. The line absorptions from the cloud can be studied as the complex rotates and periodically occults the star. We describe an analysis of the clouds of four stars (HD184927, beta Cep, sigma Ori E, and HR6684). From line synthesis models, we find that the metallic compositions are spatially uniform over the stars' surfaces. Next, using the Hubeny CIRCUS code, we demonstate that periodic UV continuum fluxes can be explained by the absorption of low-excitation lines. The analysis also quantifies the cloud temperatures, densities, and turbulences, which appear to increase inward toward the stars. The temperatures range from about 12,000K for the weak Fe lines up to temperatures of 33,000K for N V absorptions, which is in excess of temperatures ex...

  20. A Novel Approach for Star Extraction from Star Image

    Institute of Scientific and Technical Information of China (English)

    ZHENGSheng; LIUJian; TIANJinwen; YANGRuijuan

    2005-01-01

    Star acquisition is one of the most timeconsuming routines in star tracker operation. One star Point spread function (PSF) forms a near Gaussian distribution in the star image, the star image can be regarded as 2-D intensity surface, and every pixel is the sampled point. The star cluster grouping is to find the highes tintensity pixel among the PSFs and collect the adjacent pixels and group them. The possible highest intensity pixels are the maximum extremum points of the 2-D intensity surface. To efficiently extract star from the star image, a novel star acquisition approach, which uses the simplified least squares support vector machines regression algorithm to find the optimal intensity surface function and predictthe maximum extremum points, is proposed. Comput erexperiments are carried out for the simulated star images.The experimental results demonstrate that the proposed method has a lot of advantages, including the high efficiency and good robustness over a wide range of sensor noise.

  1. Infrared spectroscopy of stars

    Science.gov (United States)

    Merrill, K. M.; Ridgway, S. T.

    1979-01-01

    This paper reviews applications of IR techniques in stellar classification, studies of stellar photospheres, elemental and isotopic abundances, and the nature of remnant and ejected matter in near-circumstellar regions. Qualitative IR spectral classification of cool and hot stars is discussed, along with IR spectra of peculiar composite star systems and of obscured stars, and IR characteristics of stellar populations. The use of IR spectroscopy in theoretical modeling of stellar atmospheres is examined, IR indicators of stellar atmospheric composition are described, and contributions of IR spectroscopy to the study of stellar recycling of interstellar matter are summarized. The future of IR astronomy is also considered.

  2. Nuclear physics of stars

    CERN Document Server

    Iliadis, Christian

    2007-01-01

    Thermonuclear reactions in stars is a major topic in the field of nuclear astrophysics, and deals with the topics of how precisely stars generate their energy through nuclear reactions, and how these nuclear reactions create the elements the stars, planets and - ultimately - we humans consist of. The present book treats these topics in detail. It also presents the nuclear reaction and structure theory, thermonuclear reaction rate formalism and stellar nucleosynthesis. The topics are discussed in a coherent way, enabling the reader to grasp their interconnections intuitively. The book serves bo

  3. Entropy Production of Stars

    Directory of Open Access Journals (Sweden)

    Leonid M. Martyushev

    2015-06-01

    Full Text Available The entropy production (inside the volume bounded by a photosphere of main-sequence stars, subgiants, giants, and supergiants is calculated based on B–V photometry data. A non-linear inverse relationship of thermodynamic fluxes and forces as well as an almost constant specific (per volume entropy production of main-sequence stars (for 95% of stars, this quantity lies within 0.5 to 2.2 of the corresponding solar magnitude is found. The obtained results are discussed from the perspective of known extreme principles related to entropy production.

  4. Integration of BETA with Eclipse

    DEFF Research Database (Denmark)

    Andersen, Peter; Madsen, Ole Lehrmann; Enevoldsen, Mads Brøgger

    2004-01-01

    This paper presents language interoperability issues appearing in order to implement support for the BETA language in the Java-based Eclipse integrated development environment. One of the challenges is to implement plug-ins in BETA and be able to load them in Eclipse. In order to do this, some form...

  5. Measurements of sin 2 $\\beta$

    CERN Document Server

    Tricomi, A

    2000-01-01

    A review of the most recent measurements of the CP violating parameter sin 2 beta from LEP and CDF is reported. These yield an average value of sin 2 beta =0.91+or-0.35, giving a confidence level that CP violation in the B system has been observed of almost 99%. (10 refs).

  6. Beta decay of Cu-56

    NARCIS (Netherlands)

    Borcea, R; Aysto, J; Caurier, E; Dendooven, P; Doring, J; Gierlik, M; Gorska, M; Grawe, H; Hellstrom, M; Janas, Z; Jokinen, A; Karny, M; Kirchner, R; La Commara, M; Langanke, K; Martinez-Pinedo, G; Mayet, P; Nieminen, A; Nowacki, F; Penttila, H; Plochocki, A; Rejmund, M; Roeckl, E; Schlegel, C; Schmidt, K; Schwengner, R; Sawicka, M

    2001-01-01

    The proton-rich isotope Cu-56 was produced at the GSI On-Line Mass Separator by means of the Si-28(S-32, p3n) fusion-evaporation reaction. Its beta -decay properties were studied by detecting beta -delayed gamma rays and protons. A half-Life of 93 +/- 3 ms was determined for Cu-56. Compared to the p

  7. Beta Function and Anomalous Dimensions

    DEFF Research Database (Denmark)

    Pica, Claudio; Sannino, Francesco

    2011-01-01

    We demonstrate that it is possible to determine the coefficients of an all-order beta function linear in the anomalous dimensions using as data the two-loop coefficients together with the first one of the anomalous dimensions which are universal. The beta function allows to determine the anomalou...

  8. RAVEN Beta Release

    Energy Technology Data Exchange (ETDEWEB)

    Rabiti, Cristian [Idaho National Lab. (INL), Idaho Falls, ID (United States); Alfonsi, Andrea [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cogliati, Joshua Joseph [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mandelli, Diego [Idaho National Lab. (INL), Idaho Falls, ID (United States); Kinoshita, Robert Arthur [Idaho National Lab. (INL), Idaho Falls, ID (United States); Wang, Congjian [Idaho National Lab. (INL), Idaho Falls, ID (United States); Maljovec, Daniel Patrick [Idaho National Lab. (INL), Idaho Falls, ID (United States); Talbot, Paul William [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-02-01

    This documents the release of the Risk Analysis Virtual Environment (RAVEN) code. A description of the RAVEN code is provided, and discussion of the release process for the M2LW-16IN0704045 milestone. The RAVEN code is a generic software framework to perform parametric and probabilistic analysis based on the response of complex system codes. RAVEN is capable of investigating the system response as well as the input space using Monte Carlo, Grid, or Latin Hyper Cube sampling schemes, but its strength is focused toward system feature discovery, such as limit surfaces, separating regions of the input space leading to system failure, using dynamic supervised learning techniques. RAVEN has now increased in maturity enough for the Beta 1.0 release.

  9. Utilizing Synthetic Spectra to Refine Lambda Boo Stars' UV Classification Criteria

    Science.gov (United States)

    Cheng, Kwang-Ping; Neff, James E.; Johnson, Dustin; Tarbell, Erik; Romo, Christopher; Steele, Patricia; Gray, Richard O.; Corbally, Christopher J.

    2016-01-01

    Lambda Boo-type stars are a group of late B to early F-type Population I dwarfs that show deficiencies of iron-peak elements (up to 2 dex), but their C, N, O, and S abundances are near solar. This stellar class has recently regained the spotlight because of the directly-imaged planets around a confirmed Lambda Boo star, HR 8799, and a suggested Lambda Boo star Beta Pictoris. The discovery of a giant asteroid belt around Vega, another possible Lambda Boo star, also suggests hidden planets. This possible link between Lambda Boo stars and planet-bearing stars motivates us to study Lambda Boo stars systematically. Since the peculiar nature of the prototype Lambda Bootis was first noticed in 1943, Lambda Boo candidates published in the literature have been selected using widely different criteria. The Lambda Boo label has been applied to almost any peculiar A-type stars that do not fit elsewhere. In order to determine the origin of Lambda Boo stars' unique abundance pattern and to better discriminate between theories explaining the Lambda Boo phenomenon, a consistent working definition of Lambda Boo stars is needed. We have re-evaluated all published Lambda Boo candidates and their available ultraviolet and visible spectra. Using observed and synthetic spectra, we explored the classification of Lambda Boo stars and developed quantitative criteria that discriminate metal-poor stars from bona fide Lambda Boo stars. With model spectra, we demonstrated that the (C I 1657 Angstrom)/ (Al II 1671 Angstrom) line ratio is the best single criterion to distinguish between Lambda Boo stars and metal weak stars, and that one cannot use a single C I/Al II cut-off value as a Lambda Boo classification criterion. The C I/Al II cut-off value is a function of a star's effective temperature and metallicity. Using these stricter Lambda Boo classification criteria, we concluded that neither Beta Pictoris nor Vega should be classified as Lambda Boo stars.

  10. Exocomet signatures around the A-shell star $\\Phi$ Leo?

    CERN Document Server

    Eiroa, C; Montesinos, B; Villaver, E; Absil, O; Henning, Th; Bayo, A; Canovas, H; Carmona, A; Chen, Ch; Ertel, S; Iglesias, D P; Launhardt, R; Maldonado, J; Meeus, G; Moór, A; Mora, A; Mustill, A J; Olofsson, J; Rauw, G; Riviere-Marichalar, P; Roberge, A

    2016-01-01

    We present an intensive monitoring of high-resolution spectra of the Ca {\\sc ii} K line in the A7IV shell star $\\Phi$ Leo at very short (minutes, hours), short (night to night), and medium term (weeks, months) timescales. The spectra show remarkable variable absorptions on timescales of hours, days and months. The characteristics of these sporadic events are very similar to most of the ones observed towards the debris disk host star $\\beta$ Pic, which are usually interpreted as signs of the evaporation of solid, comet-like bodies grazing or falling onto the star. Therefore, our results suggest the presence of solid bodies around $\\Phi$ Leo. To our knowledge, with the exception of $\\beta$ Pic, our monitoring is the one with the best time resolution at the mentioned timescales done on a star with events attributed to exocomets. Assuming the cometary scenario, and considering the timescales of our monitoring, our results point to $\\Phi$ Leo presenting the richest environment with comet-like events yet known, sec...

  11. The relevance of ambipolar diffusion for neutron star evolution

    CERN Document Server

    Passamonti, Andrea; Pons, José A; Miralles, Juan A

    2016-01-01

    We study ambipolar diffusion in strongly magnetised neutron stars, with special focus on the effects of neutrino reaction rates and the impact of a superfluid/superconducting transition in the neutron star core. For axisymmetric magnetic field configurations, we determine the deviation from $\\beta-$equilibrium induced by the magnetic force and calculate the velocity of the slow, quasi-stationary, ambipolar drift. We study the temperature dependence of the velocity pattern and clearly identify the transition to a predominantly solenoidal flow. For stars without superconducting/superfluid constituents and with a mixed poloidal-toroidal magnetic field of typical magnetar strength, we find that ambipolar diffusion proceeds fast enough to have a significant impact on the magnetic field evolution only at low core temperatures, $T \\lesssim 1-2\\times10^8$ K. The ambipolar diffusion timescale becomes appreciably shorter when fast neutrino reactions are present, because the possibility to balance part of the magnetic f...

  12. Physical parameters of three field RR Lyrae stars

    CERN Document Server

    Ferro, A Arellano; Jaimes, R Figuera

    2012-01-01

    Str\\"omgren $uvby-\\beta$ photometry of the stars classified as RR Lyrae stars RU Piscium, SS Piscium and TU Ursae Majoris has been used to estimate their iron abundance, temperature, gravity and absolute magnitude. The stability of the pulsating period is discussed. The nature of SS Psc as a RRc or a HADS is addressed. The reddening of each star is estimated from the Str\\"omgren colour indices and reddening sky maps. The results of three approaches to the determination of [Fe/H], $T_{\\rm eff}$ and $\\log(g)$ are discussed: Fourier light curve decomposition, the Preston $\\Delta S$ index and the theoretical grids on the $(b-y)_o - c_1{_o}$ plane.

  13. Physical parameters of seven field RR Lyrae Stars in Bootes

    CERN Document Server

    Peña, J H; Miller, R Peña; Sareyan, J P; Alvarez, M

    2009-01-01

    Str\\"omgren uvby-beta photometry is reported for the RR Lyrae stars AE, RS, ST, TV, TW, UU, and XX in Bootes. The physical parameters M/Mo, log (L/Lo), M_V, log T_eff and [Fe/H], have been estimated from the Fourier decomposition of the light curves and the empirical calibrations developed for this type of stars. Detailed behavior of the stars along the cycle of pulsation has been determined from the observed photometric indices and the synthetic indices from atmospheric models. The reddening of the zone is found to be negligible, as estimated from the reddening of several objects in the same region of the sky. Hence the distances to the individual objects are also estimated.

  14. Shear viscosity of $\\beta$-stable nuclear matter

    CERN Document Server

    Benhar, Omar

    2009-01-01

    Viscosity plays a critical role in determining the stability of rotating neutron stars. We report the results of a calculation of the shear viscosity of $\\beta$~-~stable matter, carried out using an effective interaction based on a state-of-the-art nucleon-nucleon potential and the formalism of correlated basis functions. Within our approach the equation of state, determining the proton fraction, and the nucleon-nucleon scattering probability are consistently obtained from the same dynamical model. The results show that, while the neutron contribution to the viscosity is always dominant, above nuclear saturation density the electron contribution becomes appreciable.

  15. [Serum beta 2 microglobulin (beta 2M) following renal transplantation].

    Science.gov (United States)

    Pacheco-Silva, A; Nishida, S K; Silva, M S; Ramos, O L; Azjen, H; Pereira, A B

    1994-01-01

    Although there was an important improvement in graft and patient survival the last 10 years, graft rejection continues to be a major barrier to the success of renal transplantation. Identification of a laboratory test that could help to diagnose graft rejection would facilitate the management of renal transplanted patients. PURPOSE--To evaluate the utility of monitoring serum beta 2M in recently transplanted patients. METHODS--We daily determined serum beta 2M levels in 20 receptors of renal grafts (10 from living related and 10 from cadaveric donors) and compared them to their clinical and laboratory evolution. RESULTS--Eight patients who presented immediate good renal function following grafting and did not have rejection had a mean serum beta 2M of 3.7 mg/L on the 4th day post transplant. The sensitivity of the test for the diagnosis of acute rejection was 87.5%, but the specificity was only 46%. Patients who presented acute tubular necrosis (ATN) without rejection had a progressive decrease in their serum levels of beta 2M, while their serum creatinine changed as they were dialyzed. In contrast, patients with ATN and concomitance of acute rejection or CSA nephrotoxicity presented elevated beta 2M and creatinine serum levels. CONCLUSION--Daily monitoring of serum beta 2M does not improve the ability to diagnose acute rejection in patients with good renal function. However, serum beta 2M levels seemed to be useful in diagnosing acute rejection or CSA nephrotoxicity in patients with ATN.

  16. Temperature of neutron stars

    Science.gov (United States)

    Tsuruta, Sachiko

    2016-07-01

    We start with a brief introduction to the historical background in the early pioneering days when the first neutron star thermal evolution calculations predicted the presence of neutron stars hot enough to be observable. We then report on the first detection of neutron star temperatures by ROSAT X-ray satellite, which vindicated the earlier prediction of hot neutron stars. We proceed to present subsequent developments, both in theory and observation, up to today. We then discuss the current status and the future prospect, which will offer useful insight to the understanding of basic properties of ultra-high density matter beyond the nuclear density, such as the possible presence of such exotic particles as pion condensates.

  17. Stars resembling the Sun

    Science.gov (United States)

    Cayrel de Strobel, G.

    This review is primarily directed to the question whether photometric solar analogues remain such when subjected to detailed spectroscopic analyses and interpreted with the help of internal stucture models. In other words, whether the physical parameters: mass, chemical composition, age (determining effective temperature and luminosity), chromospheric activity, equatorial rotation, lithium abundance, velocity fields etc., we derive from the spectral analysis of a photometric solar analogue, are really close to those of the Sun. We start from 109 photometric solar analogues extracted from different authors. The stars selected had to satisfy three conditions: i) their colour index (B-V) must be contained in the interval: Δ (B-V) = 0.59-0.69, ii) they must possess a trigonometric parallax, iii) they must have undergone a high resolution detailed spectroscopic analysis. First, this review presents photometric and spectrophotometric researches on solar analogues and recalls the pionneering work on these stars by the late Johannes Hardorp. After a brief discussion on low and high resolution spectroscopic researches, a comparison is made between effective temperatures as obtained, directly, from detailed spectral analyses and those obtained, indirectly, from different photometric relations. An interesting point in this review is the discussion on the tantalilizing value of the (B-V)solar of the Sun, and the presentation of a new reliable value of this index. A short restatement of the kinematic properties of the sample of solar analogues is also made. And, finally, the observational ( T eff, M bol) diagram, obtained with 99 of the initially presented 109 analogues, is compared to a theoretical ( T eff, M bol) diagram. This latter has been constructed with a grid of internal structure models for which, (very important for this investigation), the Sun was used as gauge. In analysing the position, with respect to the Sun, of each star we hoped to find a certain number of

  18. Notes on Star Formation

    CERN Document Server

    Krumholz, Mark R

    2015-01-01

    This book provides an introduction to the field of star formation at a level suitable for graduate students or advanced undergraduates in astronomy or physics. The structure of the book is as follows. The first two chapters begin with a discussion of observational techniques, and the basic phenomenology they reveal. The goal is to familiarize students with the basic techniques that will be used throughout, and to provide a common vocabulary for the rest of the book. The next five chapters provide a similar review of the basic physical processes that are important for star formation. Again, the goal is to provide a basis for what follows. The remaining chapters discuss star formation over a variety of scales, starting with the galactic scale and working down to the scales of individual stars and their disks. The book concludes with a brief discussion of the clearing of disks and the transition to planet formation. The book includes five problem sets, complete with solutions.

  19. Spectroscopy among the stars.

    Science.gov (United States)

    Winnewisser, G

    1996-06-01

    The space between the stars is not void, but filled with interstellar matter, mainly composed of dust and gas, which gather in large interstellar clouds. In our Galaxy these interstellar clouds are distributed along a thin, but extended layer which basically traces out the spiral distribution of matter: the stars, the gas, and the dust component. Up to the present time more than 100 different molecules have been identified in interstellar molecular clouds. The majority of the interstellar molecules constitute carbon containing organic substances. During the past years, overwhelming evidence has been gathered, mainly through spectroscopic observations, that interstellar molecular clouds provide the birthplaces for stars. In fact detailed high spectral and spatial resolution spectroscopic measurements reveal physical and chemical processes of the intricate star formation process.

  20. Interferometric star tracker Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Optical Physics Company (OPC) proposes to develop a high accuracy version of its interferometric star tracker capable of meeting the milli-arcsecond-level pointing...

  1. Sports Stars Shine

    Institute of Scientific and Technical Information of China (English)

    Yu Yan

    2012-01-01

    Alive and exciting award ceremony drew the attention of numerous Chinese households on the night of January 15.The most popular Chinese sports stars attended the 2011 CCTV Sports Personality Award Ceremony at the National Indoor Stadium in Beijing.

  2. Neutron Stars Recent Developments

    CERN Document Server

    Heiselberg, H

    1999-01-01

    Recent developments in neutron star theory and observation are discussed. Based on modern nucleon-nucleon potentials more reliable equations of state for dense nuclear matter have been constructed. Furthermore, phase transitions such as pion, kaon and hyperon condensation, superfluidity and quark matter can occur in cores of neutron stars. Specifically, the nuclear to quark matter phase transition and its mixed phases with intriguing structures is treated. Rotating neutron stars with and without phase transitions are discussed and compared to observed masses, radii and glitches. The observations of possible heavy $\\sim 2M_\\odot$ neutron stars in X-ray binaries and QPO's require relatively stiff equation of states and restrict strong phase transitions to occur at very high nuclear densities only.

  3. Worlds around other stars

    Science.gov (United States)

    Black, David C.

    1991-01-01

    The possible, though tentative, detection of planetary companions to other stars which may be capable of supporting life as we know it through the use of a new generation of detectors and telescopes, combined with some innovative detection techniques, is discussed. The current view of the origin of the solar system, based on the nebular hypothesis, is discussed as it pertains to the formation of how and where planets form and, hence, how and where to search for them. Both direct methods of search for other planetary systems, which involve detecting reflected light or infrared radiation form the planets themselves, and indirect methods, which involve the scrutinization of a star for signs that it is responding to the gravitational tug of an orbiting planet, are discussed at length. In particular, various methods for detecting minute velocity perturbations of stars are discussed. It is noted that the study of brown dwarfs may also provide clues on the formation of stars and planets.

  4. The JCMT Gould Belt Survey: Evidence for Dust Grain Evolution in Perseus Star-forming Clumps

    CERN Document Server

    Chen, Michael Chun-Yuan; Johnstone, D; Sadavoy, S; Hatchell, J; Mottram, J C; Kirk, H; Buckle, J; Berry, D S; Broekhoven-Fiene, H; Currie, M J; Fich, M; Jenness, T; Nutter, D; Pattle, K; Pineda, J E; Quinn, C; Salji, C; Tisi, S; Hogerheijde, M R; Ward-Thompson, D; Bastien, P; Bresnahan, D; Butner, H; Chrysostomou, A; Coude, S; Davis, C J; Drabek-Maunder, E; Duarte-Cabral, A; Fiege, J; Friberg, P; Friesen, R; Fuller, G A; Graves, S; Greaves, J; Gregson, J; Holland, W; Joncas, G; Kirk, J M; Knee, L B G; Mairs, S; Marsh, K; Matthews, B C; Moriarty-Schieven, G; Mowat, C; Pezzuto, S; Rawlings, J; Richer, J; Robertson, D; Rosolowsky, E; Rumble, D; Schneider-Bontemps, N; Thomas, H; Tothill, N; Viti, S; White, G J; Wouterloot, J; Yates, J; Zhu, M

    2016-01-01

    The dust emissivity spectral index, $\\beta$, is a critical parameter for deriving the mass and temperature of star-forming structures, and consequently their gravitational stability. The $\\beta$ value is dependent on various dust grain properties, such as size, porosity, and surface composition, and is expected to vary as dust grains evolve. Here we present $\\beta$, dust temperature, and optical depth maps of the star-forming clumps in the Perseus Molecular Cloud determined from fitting SEDs to combined Herschel and JCMT observations in the 160 $\\mu$m, 250 $\\mu$m, 350 $\\mu$m, 500 $\\mu$m, and 850 $\\mu$m bands. Most of the derived $\\beta$, and dust temperature values fall within the ranges of 1.0 - 2.7 and 8 - 20 K, respectively. In Perseus, we find the $\\beta$ distribution differs significantly from clump to clump, indicative of grain growth. Furthermore, we also see significant, localized $\\beta$ variations within individual clumps and find low $\\beta$ regions correlate with local temperature peaks, hinting a...

  5. Chaotic Star Birth

    Science.gov (United States)

    2005-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] Click on the image for Poster VersionClick on the image for IRAS 4B Inset Located 1,000 light years from Earth in the constellation Perseus, a reflection nebula called NGC 1333 epitomizes the beautiful chaos of a dense group of stars being born. Most of the visible light from the young stars in this region is obscured by the dense, dusty cloud in which they formed. With NASA's Spitzer Space Telescope, scientists can detect the infrared light from these objects. This allows a look through the dust to gain a more detailed understanding of how stars like our sun begin their lives. The young stars in NGC 1333 do not form a single cluster, but are split between two sub-groups. One group is to the north near the nebula shown as red in the image. The other group is south, where the features shown in yellow and green abound in the densest part of the natal gas cloud. With the sharp infrared eyes of Spitzer, scientists can detect and characterize the warm and dusty disks of material that surround forming stars. By looking for differences in the disk properties between the two subgroups, they hope to find hints of the star and planet formation history of this region. The knotty yellow-green features located in the lower portion of the image are glowing shock fronts where jets of material, spewed from extremely young embryonic stars, are plowing into the cold, dense gas nearby. The sheer number of separate jets that appear in this region is unprecedented. This leads scientists to believe that by stirring up the cold gas, the jets may contribute to the eventual dispersal of the gas cloud, preventing more stars from forming in NGC 1333. In contrast, the upper portion of the image is dominated by the infrared light from warm dust, shown as red.

  6. Alkaline broadening in Stars

    CERN Document Server

    De Kertanguy, A

    2015-01-01

    Giving new insight for line broadening theory for atoms with more structure than hydrogen in most stars. Using symbolic software to build precise wave functions corrected for ds;dp quantum defects. The profiles obtained with that approach, have peculiar trends, narrower than hydrogen, all quantum defects used are taken from atomic database topbase. Illustration of stronger effects of ions and electrons on the alkaline profiles, than neutral-neutral collision mechanism. Keywords : Stars: fundamental parameters - Atomic processes - Line: profiles.

  7. A spectroscopic orbit for the late-type Be star β CMi

    Science.gov (United States)

    Dulaney, Nick; Richardson, Noel; Gerhartz, Cody; Bjorkman, Jon Eric; Bjorkman, Karen S.; Carciofi, Alex C.; Wang, Luqian; Morrison, Nancy D.; Klement, Robert; Ritter Observing Team

    2017-01-01

    The late-type Be star beta CMi is remarkably stable compared to other Be stars that have been studied. This has led to a realistic model of the outflowing Be disk by Klement et al. (2015) These results showed that the disk is likely truncated at a finite radius from the star, which is easily accomplished by a binary companion in orbit. We report on an analysis of the Ritter Observatory spectroscopic archive of beta CMi in hopes of discovering evidence of the elusive companion. We detect orbital motion caused by a companion from small shifts in the H-alpha emission line. We then compared the small changes in the violet-to-red peak height changes (V/R) with the orbital motion. While some V/R variability seems to be present in the H-alpha profile, there is only weak evidence that it follows the orbital motion, as suggested by recent Be binary models by Panoglou et al. (2016). We also analyze several epochs of near-infrared moderate resolution spectra from the InfraRed Telescope Facility with the SpeX spectrograph. Near-infrared spectra show variations of the Pa-beta and Br-gamma lines, suggesting structure could be present in the inner parts of the Be disk. These results suggest that beta CMi is similar to several other Be stars, and is a product of binary evolution where Roche lobe overflow has spun up the current Be star, likely leaving a hot subdwarf or white dwarf in orbit around the star. Unfortunately, no sign of this star is found in the very limited archive of International Ultraviolet Explorer spectra, so future UV studies of the system are necessary.We are grateful for support of the NSF REU program at the University of Toledo through NSF grant 1262810 and addtional support from the NSF under grant AST-1412135.

  8. Resolved Star Formation on Sub-galactic Scales in a Merger at z=1.7

    CERN Document Server

    Whitaker, Katherine E; Brammer, Gabriel B; Gladders, Michael D; Sharon, Keren; Teng, Stacy H; Wuyts, Eva

    2014-01-01

    We present a detailed analysis of Hubble Space Telescope (HST), Wide Field Camera 3 (WFC3) G141 grism spectroscopy for seven star-forming regions of the highly magnified lensed star- burst galaxy RCSGA 032727-132609 at z = 1.704. We measure the spatial variations of the extinction in RCS0327 through the observed H$\\gamma$/H$\\beta$ emission line ratios, finding a constant average extinction of $E(B-V)_{gas} = 0.40\\pm0.07$. We infer that the star formation is enhanced as a result of an ongoing interaction, with measured star formation rates derived from demagnified, extinction-corrected Hbeta line fluxes for the individual star-forming clumps falling >1-2 dex above the star formation sequence. When combining the HST/WFC3 [OIII] $\\lambda$5007/H$\\beta$ emission line ratio measurements with [NII]/H$\\alpha$ line ratios from Wuyts et al. (2014), we find that the majority of the individual star-forming regions fall along the local "normal" abundance sequence. With the first detections of the He I $\\lambda$5876 $\\AA$ ...

  9. The Star Formation History of Local Starbursts as Benchmark for High Redshifts

    Science.gov (United States)

    Schmitt, Henrique R.; Calzetti, Daniela; Armus, Lee

    2001-08-01

    We propose to use the WIYN telescope and MIMO to obtain broad band B and R, and narrow band H(alpha) and H(beta) images for a sample of 13 local starburst galaxies detected by ISO at 170-200(micron) and for which we are obtaining ultraviolet (1600Å) images with an approved HST/STIS program. With these observations we will complete the ground based portion of this project. This sample spans a wide range in the luminosity, star formation rate, metallicity and morphology parameters, and will be used as a low-redshift benchmark to explore the relationship between the Lyman-break and the SCUBA galaxies at z~3. The broad- band ground-based and HST images will be used to characterize the stellar populations and determine the ages of the star forming regions of these galaxies, while the H(alpha)/H(beta) ratio will be used to determine the reddening and gas morphology of these regions. We will study the conditions for the escape of UV light from a dusty galaxy, as a function of the sample parameters. The H(alpha) and UV HST images will be combined to derive a relative empirical calibration between these two star formation indicators. We will measure the fraction of nuclear and disk emission, the fraction of star formation in massive clusters and the properties of those star clusters, the structural properties of star forming bars, rings, and tidally-driven star formation in IR-bright galaxies.

  10. Photometric Observations of 6000 Stars in the Cygnus Field

    Science.gov (United States)

    Borucki, W.; Caldwell, D.; Koch, D.; Jenkins, J.; Ninkov, Z.

    1999-01-01

    transits a much larger primary. However when high-resolution spectra were obtained for both stars, the stars were found to be double-lined binaries so similar in size as to have indistinguishable transit depths. The low amplitude of the transits is explained if the stellar orbital planes are tipped approximately 5 degrees from the line of sight causing both binaries to show grazing transits. The two absorption lines, due to the H(sub beta) feature in each star, are apparent and indicate the presence of a binary system with similar components.

  11. Experiments on double beta decay

    Energy Technology Data Exchange (ETDEWEB)

    Busto, J. [Neuchatel Univ. (Switzerland). Inst. de Physique

    1996-11-01

    The Double Beta Decay, and especially ({beta}{beta}){sub 0{nu}} mode, is an excellent test of Standard Model as well as of neutrino physics. From experimental point of view, a very large number of different techniques are or have been used increasing the sensitivity of this experiments quite a lot (the factor of 10{sup 4} in the last 20 years). In future, in spite of several difficulties, the sensitivity would be increased further, keeping the interest of this very important process. (author) 4 figs., 5 tabs., 21 refs.

  12. Dosimetry of {beta} extensive sources; Dosimetria de fuentes {beta} extensas

    Energy Technology Data Exchange (ETDEWEB)

    Rojas C, E.L.; Lallena R, A.M. [Departamento de Fisica Moderna, Universidad de Granada, E-18071 Granada (Spain)

    2002-07-01

    In this work, we have been studied, making use of the Penelope Monte Carlo simulation code, the dosimetry of {beta} extensive sources in situations of spherical geometry including interfaces. These configurations are of interest in the treatment of the called cranealfaringyomes of some synovia leisure of knee and other problems of interest in medical physics. Therefore, its application can be extended toward problems of another areas with similar geometric situation and beta sources. (Author)

  13. Life Cycle of Stars

    Science.gov (United States)

    1999-01-01

    In this stunning picture of the giant galactic nebula NGC 3603, the crisp resolution of NASA's Hubble Space Telescope captures various stages of the life cycle of stars in one single view. To the upper left of center is the evolved blue supergiant called Sher 25. The star has a unique circumstellar ring of glowing gas that is a galactic twin to the famous ring around the supernova 1987A. The grayish-bluish color of the ring and the bipolar outflows (blobs to the upper right and lower left of the star) indicates the presence of processed (chemically enriched) material. Near the center of the view is a so-called starburst cluster dominated by young, hot Wolf-Rayet stars and early O-type stars. A torrent of ionizing radiation and fast stellar winds from these massive stars has blown a large cavity around the cluster. The most spectacular evidence for the interaction of ionizing radiation with cold molecular-hydrogen cloud material are the giant gaseous pillars to the right of the cluster. These pillars are sculptured by the same physical processes as the famous pillars Hubble photographed in the M16 Eagle Nebula. Dark clouds at the upper right are so-called Bok globules, which are probably in an earlier stage of star formation. To the lower left of the cluster are two compact, tadpole-shaped emission nebulae. Similar structures were found by Hubble in Orion, and have been interpreted as gas and dust evaporation from possibly protoplanetary disks (proplyds). This true-color picture was taken on March 5, 1999 with the Wide Field Planetary Camera 2.

  14. Evolution of outer membrane beta-barrels from an ancestral beta beta hairpin.

    Science.gov (United States)

    Remmert, M; Biegert, A; Linke, D; Lupas, A N; Söding, J

    2010-06-01

    Outer membrane beta-barrels (OMBBs) are the major class of outer membrane proteins from Gram-negative bacteria, mitochondria, and plastids. Their transmembrane domains consist of 8-24 beta-strands forming a closed, barrel-shaped beta-sheet around a central pore. Despite their obvious structural regularity, evidence for an origin by duplication or for a common ancestry has not been found. We use three complementary approaches to show that all OMBBs from Gram-negative bacteria evolved from a single, ancestral beta beta hairpin. First, we link almost all families of known single-chain bacterial OMBBs with each other through transitive profile searches. Second, we identify a clear repeat signature in the sequences of many OMBBs in which the repeating sequence unit coincides with the structural beta beta hairpin repeat. Third, we show that the observed sequence similarity between OMBB hairpins cannot be explained by structural or membrane constraints on their sequences. The third approach addresses a longstanding problem in protein evolution: how to distinguish between a very remotely homologous relationship and the opposing scenario of "sequence convergence." The origin of a diverse group of proteins from a single hairpin module supports the hypothesis that, around the time of transition from the RNA to the protein world, proteins arose by amplification and recombination of short peptide modules that had previously evolved as cofactors of RNAs.

  15. Detailed opacity calculations for stellar models

    Science.gov (United States)

    Pain, Jean-Christophe; Gilleron, Franck

    2016-10-01

    We present a state of the art of precise spectral opacity calculations illustrated by stellar applications. The essential role of laboratory experiments to check the quality of the computed data is underlined. We review some X-ray and XUV laser and Z-pinch photo-absorption measurements as well as X-ray emission spectroscopy experiments of hot dense plasmas produced by ultra-high-intensity laser interaction. The measured spectra are systematically compared with the fine-structure opacity code SCO-RCG. Focus is put on iron, due to its crucial role in the understanding of asteroseismic observations of Beta Cephei-type and Slowly Pulsating B stars, as well as in the Sun. For instance, in Beta Cephei-type stars (which should not be confused with Cepheid variables), the iron-group opacity peak excites acoustic modes through the kappa-mechanism. A particular attention is paid to the higher-than-predicted iron opacity measured on Sandia's Z facility at solar interior conditions (boundary of the convective zone). We discuss some theoretical aspects such as orbital relaxation, electron collisional broadening, ionic Stark effect, oscillator-strength sum rules, photo-ionization, or the ``filling-the-gap'' effect of highly excited states.

  16. Questions Students Ask: Beta Decay.

    Science.gov (United States)

    Koss, Jordan; Hartt, Kenneth

    1988-01-01

    Answers a student's question about the emission of a positron from a nucleus. Discusses the problem from the aspects of the uncertainty principle, beta decay, the Fermi Theory, and modern physics. (YP)

  17. Dark Stars: A Review

    CERN Document Server

    Freese, Katherine; Spolyar, Douglas; Valluri, Monica

    2015-01-01

    Dark Stars (DS) are stellar objects made (almost entirely) of ordinary atomic material but powered by the heat from Dark Matter (DM) annihilation (rather than by fusion). Weakly Interacting Massive Particles (WIMPs), among the best candidates for DM, can be their own antimatter and can accumulate inside the star, with their annihilation products thermalizing with and heating the DS. The resulting DSs are in hydrostatic and thermal equilibrium. The first phase of stellar evolution in the history of the Universe may have been dark stars. Though DM constituted only $10^6 M_\\odot$), very bright ($>10^9 L_\\odot$), and potentially detectable with the James Webb Space Telescope (JWST). Once the DM runs out and the dark star dies, it may collapse to a black hole; thus DSs can provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The curre...

  18. Stars, Galaxies and Quasars

    Directory of Open Access Journals (Sweden)

    Patrick Das Gupta

    2009-05-01

    Full Text Available This article provides a brief introduction to the basics of stars, galaxies and Quasi-stellar objects (QSOs. In stars, the central pressure and temperature must be high in order to halt the stellar gravitational collapse. High temperature leads to thermonuclear fusion in the stellar core, releasing thereby enormous amount of nuclear energy, making the star shine brilliantly. On the other hand, the QSOs are very bright nuclei lying in the centres of some galaxies. Many of these active galactic nuclei, which appear star-like when observed through a telescope and  whose power output are more than 1011 times that of the Sun, exhibit rapid time variability in their X-ray emissions.  Rapid variability along with the existence of a maximum speed limit, c, provide a strong argument in favour of a compact central engine model for QSOs in which a thick disc of hot gas going around a supermassive blackhole is what makes a QSO appear like a bright point source. Hence, unlike stars, QSOs are powered by gravitational potential energy.

  19. Hot subluminous stars

    CERN Document Server

    Heber, Ulrich

    2016-01-01

    Hot subluminous stars of spectral type B and O are core helium-burning stars at the blue end of the horizontal branch or have evolved even beyond that stage. Strikingly, the distribution in the Hertzsprung-Russell diagram of He-rich vs. He-poor hot subdwarf stars of the globular clusters omega Cen and NGC~2808 differ from that of their field counterparts. The metal-abundance patterns of hot subdwarfs are typically characterized by strong deficiencies of some lighter elements as well as large enrichments of heavy elements. A large fraction of sdB stars are found in close binaries with white dwarf or very low-mass main sequence companions, which must have gone through a common-envelope phase of evolution.They provide a clean-cut laboratory to study this important but yet purely understood phase of stellar evolution. Substellar companions to sdB stars have also been found. For HW~Vir systems the companion mass distribution extends from the stellar into the brown dwarf regime. A giant planet to the pulsator V391 ...

  20. Circulation of Stars

    Science.gov (United States)

    Boitani, P.

    2016-01-01

    Since the dawn of man, contemplation of the stars has been a primary impulse in human beings, who proliferated their knowledge of the stars all over the world. Aristotle sees this as the product of primeval and perennial “wonder” which gives rise to what we call science, philosophy, and poetry. Astronomy, astrology, and star art (painting, architecture, literature, and music) go hand in hand through millennia in all cultures of the planet (and all use catasterisms to explain certain phenomena). Some of these developments are independent of each other, i.e., they take place in one culture independently of others. Some, on the other hand, are the product of the “circulation of stars.” There are two ways of looking at this. One seeks out forms, the other concentrates on the passing of specific lore from one area to another through time. The former relies on archetypes (for instance, with catasterism), the latter constitutes a historical process. In this paper I present some of the surprising ways in which the circulation of stars has occurred—from East to West, from East to the Far East, and from West to East, at times simultaneously.

  1. Young Stars with SALT

    CERN Document Server

    Riedel, Adric R; Rice, Emily L; Cruz, Kelle L; Henry, Todd J

    2016-01-01

    We present a spectroscopic and kinematic analysis of 79 nearby M dwarfs in 77 systems. All are low-proper-motion southern hemisphere objects and were identified in a nearby star survey with a demonstrated sensitivity to young stars. Using low-resolution optical spectroscopy from the Red Side Spectrograph (RSS) on the South African Large Telescope (SALT), we have determined radial velocities, H-alpha, Lithium 6708\\AA, and Potassium 7699\\AA~equivalent widths linked to age and activity, and spectral types for all our targets. Combined with astrometric information from literature sources, we identify 44 young stars. Eighteen are previously known members of moving groups within 100 parsecs of the Sun. Twelve are new members, including one member of the TW Hydra moving group, one member of the 32 Orionis moving group, nine members of Tucana-Horologium, one member of Argus, and two new members of AB Doradus. We also find fourteen young star systems that are not members of any known groups. The remaining 33 star syst...

  2. Beta Function and Anomalous Dimensions

    CERN Document Server

    Pica, Claudio

    2010-01-01

    We demonstrate that it is possible to determine the coefficients of an all-order beta function linear in the anomalous dimensions using as data the two-loop coefficients together with the first one of the anomalous dimensions which are universal. The beta function allows to determine the anomalous dimension of the fermion masses at the infrared fixed point, and the resulting values compare well with the lattice determinations.

  3. Stars a very short introduction

    CERN Document Server

    King, Andrew

    2012-01-01

    Stars: A Very Short Introduction looks at how stars live, producing all the chemical elements beyond helium, and how they die, leaving remnants such as black holes. Every atom of our bodies has been part of a star. Our very own star, the Sun, is crucial to the development and sustainability of life on Earth. Understanding stars is key to understanding the galaxies they inhabit, the existence of planets, and the history of our entire Universe. This VSI explores the science of stars, the mechanisms that allow them to form, the processes that allow them to shine, and the results of their death.

  4. {beta}-decay studies of r-process nuclei at NSCL

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, J. [National Superconducting Cyclotron Laboratory, Michigan State University, E. Lansing, MI (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, E. Lansing, MI (United States)], E-mail: pereira@nscl.msu.edu; Aprahamian, A. [Institute of Structure and Nuclear Astrophysics, University of Notre Dame, South Bend, IN (United States); Joint Institute for Nuclear Astrophysics, University of Notre Dame, South Bend, IN (United States); Arndt, O. [Institut fuer Kernchemie, Universitaet Mainz, Mainz (Germany); Virtuelles Institut fuer Struktur der Kerne and Nuklearer Astrophysik, Mainz (Germany); Becerril, A.; Elliot, T. [National Superconducting Cyclotron Laboratory, Michigan State University, E. Lansing, MI (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, E. Lansing, MI (United States); Estrade, A. [National Superconducting Cyclotron Laboratory, Michigan State University, E. Lansing, MI (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, E. Lansing, MI (United States); Department of Physics and Astronomy, Michigan State University, E. Lansing, MI (United States); Galaviz, D. [National Superconducting Cyclotron Laboratory, Michigan State University, E. Lansing, MI (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, E. Lansing, MI (United States); Hennrich, S. [Institut fuer Kernchemie, Universitaet Mainz, Mainz (Germany); Virtuelles Institut fuer Struktur der Kerne and Nuklearer Astrophysik, Mainz (Germany); Hosmer, P. [National Superconducting Cyclotron Laboratory, Michigan State University, E. Lansing, MI (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, E. Lansing, MI (United States); Department of Physics and Astronomy, Michigan State University, E. Lansing, MI (United States)] (and others)

    2008-06-01

    Observed neutron-capture elemental abundances in metal-poor stars, along with ongoing analysis of the extremely metal-poor Eu-enriched sub-class provide new guidance for astrophysical models aimed at finding the r-process sites. The present paper emphasizes the importance of nuclear physics parameters entering in these models, particularly {beta}-decay properties of neutron-rich nuclei. In this context, several r-process motivated {beta}-decay experiments performed at the National Superconducting Cyclotron Laboratory (NSCL) are presented, including a summary of results and impact on model calculations.

  5. Determination of chromatographic and spectrophotometric dissociation constants of some beta lactam antibiotics.

    Science.gov (United States)

    Demiralay, Ebru Çubuk; Koç, Duygu; Daldal, Y Doğan; Cakır, Cansel

    2012-12-01

    In this work, dissociation constants values of seven beta lactam antibiotics in water and acetonitrile-water mixtures using spectrophotometric and reversed phase liquid chromatography methods were determined. The dissociation constant values of these compounds were calculated by NLREG and STAR programs. Aqueous pK(a) values of beta lactam antibiotics were calculated with extrapolation by means of the Yasuda-Shedlovsky and mole fraction equations. Finally, application of the different techniques was compared to the determination of aqueous pK(a) values of investigated compounds.

  6. Highly compact neutron stars in scalar-tensor theories of gravity: spontaneous scalarization vs. gravitational collapse

    CERN Document Server

    Mendes, Raissa F P

    2016-01-01

    Scalar-tensor theories of gravity are extensions of General Relativity (GR) including an extra, nonminimally coupled scalar degree of freedom. A wide class of these theories, albeit indistinguishable from GR in the weak field regime, predicts a radically different phenomenology for neutron stars, due to a nonperturbative, strong-field effect referred to as spontaneous scalarization. This effect is known to occur in theories where the effective linear coupling $\\beta_0$ between the scalar and matter fields is sufficiently negative, i.e. $\\beta_0 \\lesssim -4.35$, and has been strongly constrained by pulsar timing observations. In the test-field approximation, spontaneous scalarization manifests itself as a tachyonic-like instability. Recently, it was argued that, in theories where $\\beta_0>0$, a similar instability would be triggered by sufficiently compact neutron stars obeying realistic equations of state. In this work we investigate the endstate of this instability for some representative coupling functions ...

  7. Polypeptides having beta-glucosidase activity, beta-xylosidase activity, or beta-glucosidase and beta-xylosidase activity and polynucleotides encoding same

    Energy Technology Data Exchange (ETDEWEB)

    Morant, Marc

    2017-02-07

    The present invention relates to isolated polypeptides having beta-glucosidase activity, beta-xylosidase activity, or beta-glucosidase and beta-xylosidase activity and isolated polynucleotides encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the polynucleotides as well as methods of producing and using the polypeptides.

  8. Far Ultraviolet Spectra of B Stars near the Ecliptic

    CERN Document Server

    Morales, C; Gómez, J F; Trapero, J; Talavera, A; Bowyer, S; Edelstein, J D; Korpela, E J; Lampton, M; Drake, J J

    2000-01-01

    Spectra of B stars in the wavelength range of 911-1100 A have been obtained with the EURD spectrograph onboard the Spanish satellite MINISAT-01 with ~5 A spectral resolution. IUE spectra of the same stars have been used to normalize Kurucz models to the distance, reddening and spectral type of the corresponding star. The comparison of 8 main-sequence stars studied in detail (alpha Vir, epsilon Tau, lambda Tau, tau Tau, alpha Leo, zeta Lib, theta Oph, and sigma Sgr) shows agreement with Kurucz models, but observed fluxes are 10-40% higher than the models in most cases. The difference in flux between observations and models is higher in the wavelength range between Lyman alpha and Lyman beta. We suggest that Kurucz models underestimate the FUV flux of main-sequence B stars between these two Lyman lines. Computation of flux distributions of line-blanketed model atmospheres including non-LTE effects suggests that this flux underestimate could be due to departures from LTE, although other causes cannot be ruled ou...

  9. Quenching of Star Formation in Molecular Outflow Host NGC 1266

    CERN Document Server

    Alatalo, K; Graves, G; Deustua, S; Young, L M; Davis, T A; Bureau, M; Bayet, E; Blitz, L; Bois, M; Bournaud, F; Cappellari, M; Davies, R L; de Zeeuw, P T; Emsellem, E; Khochfar, S; Krajnovic, D; Kuntschner, H; McDermid, R M; Morganti, R; Naab, T; Oosterloo, T; Sarzi, M; Scott, N; Serra, P; Weijmans, A

    2012-01-01

    We detail the rich molecular story of NGC 1266, its serendipitous discovery within the ATLAS3D survey (Cappellari et al. 2011) and how it plays host to an AGN-driven molecular outflow, potentially quenching all of its star formation (SF) within the next 100 Myr. While major mergers appear to play a role in instigating outflows in other systems, deep imaging of NGC 1266 as well as stellar kinematic observations from SAURON, have failed to provide evidence that NGC 1266 has recently been involved in a major interaction. The molecular gas and the instantaneous SF tracers indicate that the current sites of star formation are located in a hypercompact disk within 200 pc of the nucleus (Fig. 1; SF rate ~ 2 Msuns/yr). On the other hand, tracers of recent star formation, such as the H{\\beta} absorption map from SAURON and stellar population analysis show that the young stars are distributed throughout a larger area of the galaxy than current star formation. As the AGN at the center of NGC 1266 continues to drive cold...

  10. Global Star Formation Rates in Disk Galaxies and Circumnuclear Starbursts from Cloud Collisions

    CERN Document Server

    Tan, J C

    1999-01-01

    We invoke star formation triggered by cloud-cloud collisions to explain global star formation rates of disk galaxies and circumnuclear starbursts. Previous theories based on the growth rate of gravitational perturbations ignore the dynamically important presence of magnetic fields. Theories based on triggering by spiral density waves fail to explain star formation in systems without such waves. Furthermore, observations suggest gas and stellar disk instabilities are decoupled. Following the numerical work of Gammie, Jog & Ostriker (1991), the cloud collision rate is set by the shear velocity of encounters with initial impact parameters of a few tidal radii, due to differential rotation in the disk. This enhances the collision rate above that calculated from simply considering the random velocities of clouds. We predict Sigma_{SFR}(R) is proportional to Sigma_{gas} Omega (1 - 0.7 beta). In the case of constant circular velocity (beta = 0), this is in agreement with recent observations (Kennicutt 1998). We ...

  11. Equation of state and thickness of the inner crust of neutron stars

    CERN Document Server

    Grill, Fabrizio; Providência, Constança; Vidaña, Isaac; Avancini, Sidney S

    2014-01-01

    The cell structure of $\\beta$-stable clusters in the inner crust of cold and warm neutron stars is studied within the Thomas-Fermi approach using relativistic mean field nuclear models. The relative size of the inner crust and the pasta phase of neutron stars is calculated, and the effect of the symmetry energy slope parameter, $L$, on the profile of the neutron star crust is discussed. It is shown that while the size of the total crust is mainly determined by the incompressibility modulus, the relative size of the inner crust depends on $L$. It is found that the inner crust represents a larger fraction of the total crust for smaller values of $L$. Finally, it is shown that at finite temperature the pasta phase in $\\beta$-equilibrium matter essentially melts above $5-6$ MeV, and that the onset density of the rodlike and slablike structures does not depend on the temperature.

  12. Dynamical Boson Stars

    Directory of Open Access Journals (Sweden)

    Steven L. Liebling

    2012-05-01

    Full Text Available The idea of stable, localized bundles of energy has strong appeal as a model for particles. In the 1950s, John Wheeler envisioned such bundles as smooth configurations of electromagnetic energy that he called geons, but none were found. Instead, particle-like solutions were found in the late 1960s with the addition of a scalar field, and these were given the name boson stars. Since then, boson stars find use in a wide variety of models as sources of dark matter, as black hole mimickers, in simple models of binary systems, and as a tool in finding black holes in higher dimensions with only a single Killing vector. We discuss important varieties of boson stars, their dynamic properties, and some of their uses, concentrating on recent efforts.

  13. Giant star seismology

    CERN Document Server

    Hekker, S

    2016-01-01

    The internal properties of stars in the red-giant phase undergo significant changes on relatively short timescales. Long near-interrupted high-precision photometric timeseries observations from dedicated space missions such as CoRoT and Kepler have provided seismic inferences of the global and internal properties of a large number of evolved stars, including red giants. These inferences are confronted with predictions from theoretical models to improve our understanding of stellar structure and evolution. Our knowledge and understanding of red giants have indeed increased tremendously using these seismic inferences, and we anticipate that more information is still hidden in the data. Unraveling this will further improve our understanding of stellar evolution. This will also have significant impact on our knowledge of the Milky Way Galaxy as well as on exo-planet host stars. The latter is important for our understanding of the formation and structure of planetary systems.

  14. Carbon neutron star atmospheres

    CERN Document Server

    Suleimanov, V F; Pavlov, G G; Werner, K

    2013-01-01

    The accuracy of measuring the basic parameters of neutron stars is limited in particular by uncertainties in chemical composition of their atmospheres. For example, atmospheres of thermally - emitting neutron stars in supernova remnants might have exotic chemical compositions, and for one of them, the neutron star in CasA, a pure carbon atmosphere has recently been suggested by Ho & Heinke (2009). To test such a composition for other similar sources, a publicly available detailed grid of carbon model atmosphere spectra is needed. We have computed such a grid using the standard LTE approximation and assuming that the magnetic field does not exceed 10^8 G. The opacities and pressure ionization effects are calculated using the Opacity Project approach. We describe the properties of our models and investigate the impact of the adopted assumptions and approximations on the emergent spectra.

  15. Atomic diffusion in stars

    CERN Document Server

    Michaud, Georges; Richer, Jacques

    2015-01-01

    This book gives an overview of atomic diffusion, a fundamental physical process, as applied to all types of stars, from the main sequence to neutron stars. The superficial abundances of stars as well as their evolution can be significantly affected. The authors show where atomic diffusion plays an essential role and how it can be implemented in modelling.  In Part I, the authors describe the tools that are required to include atomic diffusion in models of stellar interiors and atmospheres. An important role is played by the gradient of partial radiative pressure, or radiative acceleration, which is usually neglected in stellar evolution. In Part II, the authors systematically review the contribution of atomic diffusion to each evolutionary step. The dominant effects of atomic diffusion are accompanied by more subtle effects on a large number of structural properties throughout evolution. One of the goals of this book is to provide the means for the astrophysicist or graduate student to evaluate the importanc...

  16. Collapse of axion stars

    Science.gov (United States)

    Eby, Joshua; Leembruggen, Madelyn; Suranyi, Peter; Wijewardhana, L. C. R.

    2016-12-01

    Axion stars, gravitationally bound states of low-energy axion particles, have a maximum mass allowed by gravitational stability. Weakly bound states obtaining this maximum mass have sufficiently large radii such that they are dilute, and as a result, they are well described by a leading-order expansion of the axion potential. Heavier states are susceptible to gravitational collapse. Inclusion of higher-order interactions, present in the full potential, can give qualitatively different results in the analysis of collapsing heavy states, as compared to the leading-order expansion. In this work, we find that collapsing axion stars are stabilized by repulsive interactions present in the full potential, providing evidence that such objects do not form black holes. In the last moments of collapse, the binding energy of the axion star grows rapidly, and we provide evidence that a large amount of its energy is lost through rapid emission of relativistic axions.

  17. Uniformly rotating neutron stars

    CERN Document Server

    Boshkayev, Kuantay

    2016-01-01

    In this chapter we review the recent results on the equilibrium configurations of static and uniformly rotating neutron stars within the Hartle formalism. We start from the Einstein-Maxwell-Thomas-Fermi equations formulated and extended by Belvedere et al. (2012, 2014). We demonstrate how to conduct numerical integration of these equations for different central densities ${\\it \\rho}_c$ and angular velocities $\\Omega$ and compute the static $M^{stat}$ and rotating $M^{rot}$ masses, polar $R_p$ and equatorial $R_{\\rm eq}$ radii, eccentricity $\\epsilon$, moment of inertia $I$, angular momentum $J$, as well as the quadrupole moment $Q$ of the rotating configurations. In order to fulfill the stability criteria of rotating neutron stars we take into considerations the Keplerian mass-shedding limit and the axisymmetric secular instability. Furthermore, we construct the novel mass-radius relations, calculate the maximum mass and minimum rotation periods (maximum frequencies) of neutron stars. Eventually, we compare a...

  18. Orbital parameters, masses and distance to beta Centauri determined with the Sydney University Stellar Interferometer and high-resolution spectroscopy

    NARCIS (Netherlands)

    Davis, J.; Mendez, A.; Seneta, E.B.; Tango, W.J.; Booth, A.J.; O'Byrne, J.W.; Thorvaldson, E.D.; Ausseloos, M.; Aerts, C.C.; Uytterhoeven, K.

    2005-01-01

    The bright southern binary star beta Centauri (HR5267) has been observed with the Sydney University Stellar Interferometer (SUSI) and spectroscopically with the European Southern Observatory Coude Auxiliary Telescope and Swiss Euler telescope at La Silla. The interferometric observations have confir

  19. General Relativity&Compact Stars

    Energy Technology Data Exchange (ETDEWEB)

    Glendenning, Norman K.

    2005-08-16

    Compact stars--broadly grouped as neutron stars and white dwarfs--are the ashes of luminous stars. One or the other is the fate that awaits the cores of most stars after a lifetime of tens to thousands of millions of years. Whichever of these objects is formed at the end of the life of a particular luminous star, the compact object will live in many respects unchanged from the state in which it was formed. Neutron stars themselves can take several forms--hyperon, hybrid, or strange quark star. Likewise white dwarfs take different forms though only in the dominant nuclear species. A black hole is probably the fate of the most massive stars, an inaccessible region of spacetime into which the entire star, ashes and all, falls at the end of the luminous phase. Neutron stars are the smallest, densest stars known. Like all stars, neutron stars rotate--some as many as a few hundred times a second. A star rotating at such a rate will experience an enormous centrifugal force that must be balanced by gravity or else it will be ripped apart. The balance of the two forces informs us of the lower limit on the stellar density. Neutron stars are 10{sup 14} times denser than Earth. Some neutron stars are in binary orbit with a companion. Application of orbital mechanics allows an assessment of masses in some cases. The mass of a neutron star is typically 1.5 solar masses. They can therefore infer their radii: about ten kilometers. Into such a small object, the entire mass of our sun and more, is compressed.

  20. A search for nearby young stars among the flare stars

    CERN Document Server

    König, B; Hambaryan, V; Neuh\\"auser, Ralph; Hambaryan, Valeri

    2001-01-01

    Flare stars were discovered in the late 1940s in the solar vicinity and were named UV Cet-type variables (classical FSs). Among the FSs within 100 pc we search for young stars. For the search we take spectra with sufficient resolution to resolve Lithium at 6707 \\AA and Calcium at 6718 \\AA of all the stars. The real young stars are prime targets for the search of extra-solar planets by direct imaging.

  1. Really Hot Stars

    Science.gov (United States)

    2003-04-01

    Spectacular VLT Photos Unveil Mysterious Nebulae Summary Quite a few of the most beautiful objects in the Universe are still shrouded in mystery. Even though most of the nebulae of gas and dust in our vicinity are now rather well understood, there are some which continue to puzzle astronomers. This is the case of a small number of unusual nebulae that appear to be the subject of strong heating - in astronomical terminology, they present an amazingly "high degree of excitation". This is because they contain significant amounts of ions, i.e., atoms that have lost one or more of their electrons. Depending on the atoms involved and the number of electrons lost, this process bears witness to the strength of the radiation or to the impact of energetic particles. But what are the sources of that excitation? Could it be energetic stars or perhaps some kind of exotic objects inside these nebulae? How do these peculiar objects fit into the current picture of universal evolution? New observations of a number of such unusual nebulae have recently been obtained with the Very Large Telescope (VLT) at the ESO Paranal Observatory (Chile). In a dedicated search for the origin of their individual characteristics, a team of astronomers - mostly from the Institute of Astrophysics & Geophysics in Liège (Belgium) [1] - have secured the first detailed, highly revealing images of four highly ionized nebulae in the Magellanic Clouds, two small satellite galaxies of our home galaxy, the Milky Way, only a few hundred thousand light-years away. In three nebulae, they succeeded in identifying the sources of energetic radiation and to eludicate their exceptional properties: some of the hottest, most massive stars ever seen, some of which are double. With masses of more than 20 times that of the Sun and surface temperatures above 90 000 degrees, these stars are truly extreme. PR Photo 09a/03: Nebula around the hot star AB7 in the SMC. PR Photo 09b/03: Nebula near the hot Wolf-Rayet star BAT99

  2. Atmospheres around Neutron Stars

    Science.gov (United States)

    Fryer, Chris L.; Benz, Willy

    1994-12-01

    Interest in the behavior of atmospheres around neutron stars has grown astronomically in the past few years. Some of this interest arrived in the wake of the explosion of Supernova 1987A and its elusive remnant; spawning renewed interest in a method to insure material ``fall-back'' onto the adolescent neutron star in an effort to transform it into a silent black hole. However, the bulk of the activity with atmospheres around neutron stars is concentrated in stellar models with neutron star, rather than white dwarf, cores; otherwise known as Thorne-Zytkow objects. First a mere seed in the imagination of theorists, Thorne-Zytkow objects have grown into an observational reality with an ever-increasing list of formation scenarios and observational prospects. Unfortunately, the analytic work of Chevalier on supernova fall-back implies that, except for a few cases, the stellar simulations of Thorne-Zytkow objects are missing an important aspect of physics: neutrinos. Neutrino cooling removes the pressure support of these atmospheres, allowing accretion beyond the canonical Eddington rate for these objects. We present here the results of detailed hydrodynamical simulations in one and two dimensions with the additional physical effects of neutrinos, advanced equations of state, and relativity over a range of parameters for our atmosphere including entropy and chemical composition as well as a range in the neutron star size. In agreement with Chevalier, we find, under the current list of formation scenarios, that the creature envisioned by Thorne and Zytkow will not survive the enormous appetite of a neutron star. However, neutrino heating (a physical effect not considered in Chevalier's analysis) can play an important role in creating instabilities in some formation schemes, leading to an expulsion of matter rather than rapid accretion. By placing scrutiny upon the formation methods, we can determine the observational prospects for each.

  3. Morphodynamics of star dunes

    Science.gov (United States)

    Zhang, D.; Narteau, C.; Rozier, O.; Courrech du Pont, S.

    2012-04-01

    Star dunes are among the biggest and the most impressive dunes in Earth sand seas. Nonetheless, they remain poorly studied, probably because of their apparent complexity. They are massive pyramidal dunes with interlaced arms whose slip faces are oriented in various directions. Being large, they can integrate wind properties over a wide range of time scales. Thus, they are observed for wind regimes with multiple directions, and may result from the amalgamation of dunes or from the development of arms on a well-established dune pattern. In both cases, the roles of wind directional variability and secondary flow have been emphasized but not precisely quantified. Here, we report simulations where the star dune shape results from a a combination of longitudinal dunes, which form the star dune arms. These arms may radiate and so interact with the other dunes in the field. This mass exchange, controlled by the morphodynamics of star dunes arms, must play an important role in the large-scale arrangement of star dunes networks. We first demonstrate that star dune arms orientation maximizes the flux in the direction of crests. This is opposed to the usually admit dunes orientation, which maximizes the sediment transport perpendicular to the crest. Indeed, depending on sand availability, dunes development results from the growth of a wave on a sand bed or from a net transport of sediment, which grows and extends an isolated longitudinal dune over a non-erodible soil. These two different mechanisms lead to two different modes of crests orientation. Then, we show that the propagating arms reach a stationary state characterized by constant width, height and growth rate. These are controlled by the frequency at which the wind changes direction. Arm width and height increase, whereas the propagation speed decreases with a decreasing frequency. These morphodynamics properties are helpful to assess from pattern observation the variability of wind directionality over several time

  4. Weighing the Smallest Stars

    Science.gov (United States)

    2005-01-01

    VLT Finds Young, Very Low Mass Objects Are Twice As Heavy As Predicted Summary Thanks to the powerful new high-contrast camera installed at the Very Large Telescope, photos have been obtained of a low-mass companion very close to a star. This has allowed astronomers to measure directly the mass of a young, very low mass object for the first time. The object, more than 100 times fainter than its host star, is still 93 times as massive as Jupiter. And it appears to be almost twice as heavy as theory predicts it to be. This discovery therefore suggests that, due to errors in the models, astronomers may have overestimated the number of young "brown dwarfs" and "free floating" extrasolar planets. PR Photo 03/05: Near-infrared image of AB Doradus A and its companion (NACO SDI/VLT) A winning combination A star can be characterised by many parameters. But one is of uttermost importance: its mass. It is the mass of a star that will decide its fate. It is thus no surprise that astronomers are keen to obtain a precise measure of this parameter. This is however not an easy task, especially for the least massive ones, those at the border between stars and brown dwarf objects. Brown dwarfs, or "failed stars", are objects which are up to 75 times more massive than Jupiter, too small for major nuclear fusion processes to have ignited in its interior. To determine the mass of a star, astronomers generally look at the motion of stars in a binary system. And then apply the same method that allows determining the mass of the Earth, knowing the distance of the Moon and the time it takes for its satellite to complete one full orbit (the so-called "Kepler's Third Law"). In the same way, they have also measured the mass of the Sun by knowing the Earth-Sun distance and the time - one year - it takes our planet to make a tour around the Sun. The problem with low-mass objects is that they are very faint and will often be hidden in the glare of the brighter star they orbit, also when viewed

  5. Kinematics of gas and stars in circumnuclear star-forming regions of early type spirals

    CERN Document Server

    Hagele, Guillermo F; Cardaci, Monica V; Terlevich, Elena; Terlevich, Roberto

    2008-01-01

    (Abbr.) We present high resolution (R~20000) spectra in the blue and the far red of cicumnuclear star-forming regions (CNSFRs) in three early type spirals (NGC3351, NGC2903 and NGC3310) which have allowed the study of the kinematics of stars and ionized gas in these structures and, for the first time, the derivation of their dynamical masses for the first two. In some cases these regions, about 100 to 150 pc in size, are seen to be composed of several individual star clusters with sizes between 1.5 and 4.9 pc estimated from Hubble Space Telescope (HST) images. The stellar dispersions have been obtained from the Calcium triplet (CaT) lines at $\\lambda\\lambda$ 8494,8542,8662 \\AA, while the gas velocity dispersions have been measured by Gaussian fits to the H$\\beta$ and [OIII] $\\lambda\\lambda$ 5007 \\AA lines on the high dispersion spectra. Values of the stellar velocity dispersions are between 30 and 68 km/s. We apply the virial theorem to estimate dynamical masses of the clusters, assuming that systems are grav...

  6. Implications for the formation of star clusters from extra-galactic star-formation rates

    CERN Document Server

    Weidner, C; Larsen, S S

    2004-01-01

    Observations indicate that young massive star clusters in spiral and dwarf galaxies follow a relation between luminosity of the brightest young cluster and the star-formation rate (SFR) of the host galaxy, in the sense that higher SFRs lead to the formation of brighter clusters. Assuming that the empirical relation between maximum cluster luminosity and SFR reflects an underlying similar relation between maximum cluster mass (M_ecl,max) and SFR, we compare the resulting SFR(M_ecl,max) relation with different theoretical models. The empirical correlation is found to suggest that individual star clusters form on a free-fall time-scale with their pre-cluster molecular-cloud-core radii typically being a few pc independent of mass. The cloud cores contract by factors of 5 to 10 while building-up the embedded cluster. A theoretical SFR(M_ecl,max) relation in very good agreement with the empirical correlation is obtained if the cluster mass function of a young population has a Salpeter exponent beta approx. 2.35 and...

  7. The Circumstellar Environments of Exoplanet Host Stars

    Science.gov (United States)

    Chen, Christine

    The WFIRST-AFTA mission currently includes the provision for a high contrast imaging instrument with a primary goal of discovering new, low mass exoplanets and characterizing their atmospheres. To date, eight exoplanetary systems have been discovered via direct imaging using the current generation of ground-based high-contrast facilities. Five of those systems, including the iconic beta Pictoris and HR 8799 systems, possess infrared excesses, indicative of the presence of circumstellar dust. Detailed studies of dust and gas morphology in the beta Pictoris disk provided the impetus for searching for, and eventually imaging the planet. These studies further suggest that additional planets orbit the star, but are below current detection thresholds. Such systems will be prime targets for WFIRST-AFTA, which will obtain visual spectroscopy of several spectral features from molecules in the exoplanet atmospheres including CH4, H2O, and CO2. We propose to: (1) model the dust in exoplanetary systems with well characterized planets and infrared excesses to better constrain the dust geometry and particle properties; (2) generate synthetic WFIRST-AFTA images of these disks with embedded known and putative planets using point-spread-functions generated by JPL, and run our simulations though a WFIRST-AFTA pipeline; and (3) evaluate the sensitivity of WFIRST-AFTA to known and putative planets that have a range of masses and distances from their host stars. The proposed simulations will also assist the community in understanding how WFIRST-AFTA will contribute to our knowledge of debris disks and the role that minor bodies play in the delivery of water into the terrestrial planet zone. The proposed project is complementary to the efforts currently being carried out by the Science Definition Team (SDT), which focus on simulating planets embedded in tenuous disks, analogous to the Zodiacal dust system in our Solar System, the Earth s resonant dust ring, and the HR 4796 dust ring

  8. A Real Shooting Star

    Science.gov (United States)

    2007-01-01

    [figure removed for brevity, see original site] Click on the image for movie of A Real Shooting Star This artist's animation illustrates a star flying through our galaxy at supersonic speeds, leaving a 13-light-year-long trail of glowing material in its wake. The star, named Mira (pronounced my-rah) after the latin word for 'wonderful,' sheds material that will be recycled into new stars, planets and possibly even life. NASA's Galaxy Evolution Explorer discovered the long trail of material behind Mira during its survey of the entire sky in ultraviolet light. The animation begins by showing a close-up of Mira -- a red-giant star near the end of its life. Red giants are red in color and extremely bloated; for example, if a red giant were to replace our sun, it would engulf everything out to the orbit of Mars. They constantly blow off gas and dust in the form of stellar winds, supplying the galaxy with molecules, such as oxygen and carbon, that will make their way into new solar systems. Our sun will mature into a red giant in about 5 billion years. As the animation pulls out, we can see the enormous trail of material deposited behind Mira as it hurls along between the stars. Like a boat traveling through water, a bow shock, or build up of gas, forms ahead of the star in the direction of its motion. Gas in the bow shock is heated and then mixes with the cool hydrogen gas in the wind that is blowing off Mira. This heated hydrogen gas then flows around behind the star, forming a turbulent wake. Why does the trailing hydrogen gas glow in ultraviolet light? When it is heated, it transitions into a higher-energy state, which then loses energy by emitting ultraviolet light - a process known as fluorescence. Finally, the artist's rendering gives way to the actual ultraviolet image taken by the Galaxy Evolution Explorer Mira is located 350 light-years from Earth in the constellation Cetus, otherwise known as the whale. Coincidentally, Mira and its 'whale of a tail' can be

  9. Synthetic guide star generation

    Science.gov (United States)

    Payne, Stephen A [Castro Valley, CA; Page, Ralph H [Castro Valley, CA; Ebbers, Christopher A [Livermore, CA; Beach, Raymond J [Livermore, CA

    2008-06-10

    A system for assisting in observing a celestial object and providing synthetic guide star generation. A lasing system provides radiation at a frequency at or near 938 nm and radiation at a frequency at or near 1583 nm. The lasing system includes a fiber laser operating between 880 nm and 960 nm and a fiber laser operating between 1524 nm and 1650 nm. A frequency-conversion system mixes the radiation and generates light at a frequency at or near 589 nm. A system directs the light at a frequency at or near 589 nm toward the celestial object and provides synthetic guide star generation.

  10. The physics of stars

    CERN Document Server

    Phillips, A C

    1999-01-01

    The Physics of Stars, Second Edition, is a concise introduction to the properties of stellar interiors and consequently the structure and evolution of stars. Strongly emphasising the basic physics, simple and uncomplicated theoretical models are used to illustrate clearly the connections between fundamental physics and stellar properties. This text does not intend to be encyclopaedic, rather it tends to focus on the most interesting and important aspects of stellar structure, evolution and nucleosynthesis. In the Second Edition, a new chapter on Helioseismology has been added, along with a list

  11. The formation of stars

    CERN Document Server

    Stahler, Steven W

    2008-01-01

    This book is a comprehensive treatment of star formation, one of the most active fields of modern astronomy. The reader is guided through the subject in a logically compelling manner. Starting from a general description of stars and interstellar clouds, the authors delineate the earliest phases of stellar evolution. They discuss formation activity not only in the Milky Way, but also in other galaxies, both now and in the remote past. Theory and observation are thoroughly integrated, with the aid of numerous figures and images. In summary, this volume is an invaluable resource, both as a text f

  12. The GERDA experiment on 0{nu}{beta}{beta} decay

    Energy Technology Data Exchange (ETDEWEB)

    Freund, Kai [Eberhard Karls Universitaet Tuebingen (Germany); Collaboration: GERDA-Collaboration

    2012-07-01

    The Gerda (Germanium Detector Array) collaboration searches for the neutrinoless double beta decay (0{nu}{beta}{beta}) of {sup 76}Ge. The existence of this decay would give rise to the assumption that the neutrino is a Majorana particle, i.e. its own antiparticle. A measured half-life could be used to determine the effective neutrino mass and hence resolve the neutrino mass hierarchy problem. Germanium diodes, isotopically enriched in {sup 76}Ge, are used as both source and detector. Due to the low rate of this decay (T{sub 1/2}>10{sup 25} y), the experimental background must be reduced to a level of 10{sup -2}counts/(kg y keV) or better in the region around Q{sub {beta}{beta}}. To minimize background from cosmogenically produced secondary particles, a low Z shielding is employed. Thus, the naked diodes are operated in a liquid argon cryostat, which is surrounded by a water tank acting as both passive shield and active muon Cherenkov veto. Gerda started the commissioning runs in 2010 and in November 2011, the first phase of data taking with enriched detectors has begun. In this talk, the first year of the experiment is summarized.

  13. ENERGY STAR Certified Imaging Equipment

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 2.0 ENERGY STAR Program Requirements for Imaging Equipment that are effective as of...

  14. ENERGY STAR Certified Water Coolers

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 2.0 ENERGY STAR Program Requirements for Water Coolers that are effective as of February...

  15. Stellar populations in star clusters

    CERN Document Server

    Li, Chengyuan; Deng, Licai

    2016-01-01

    Stellar populations contain the most important information about star clus- ter formation and evolution. Until several decades ago, star clusters were believed to be ideal laboratories for studies of simple stellar populations (SSPs). However, discoveries of multiple stellar populations in Galactic globular clusters have expanded our view on stellar populations in star clusters. They have simultaneously generated a number of controversies, particularly as to whether young star clusters may have the same origin as old globular clusters. In addition, extensive studies have revealed that the SSP scenario does not seem to hold for some intermediate-age and young star clusters either, thus making the origin of multiple stellar populations in star clusters even more complicated. Stellar population anomalies in numerous star clusters are well-documented, implying that the notion of star clusters as true SSPs faces serious challenges. In this review, we focus on stellar populations in massive clusters with different ...

  16. Kepler observations of Am stars

    DEFF Research Database (Denmark)

    Balona, L. A.; Ripepi, V.; Cantanzaro, G.

    2011-01-01

    We present an analysis of high-resolution spectra for two pulsating Am stars in the Kepler field. The stellar parameters derived in this way are important because parameters derived from narrow-band photometry may be affected by the strong metal lines in these stars. We analyse the Kepler time...... series of ten known Am stars and find that six of them clearly show δ Scuti pulsations. The other four appear to be non-pulsating. We derive fundamental parameters for all known pulsating Am stars from ground-based observations and also for the Kepler Am stars to investigate the location...... of the instability strip for pulsating Am stars. We find that there is not much difference between the Am-star instability strip and the δ Scuti instability strip. We find that the observed location of pulsating Am stars in the HR diagram does not agree with the location predicted from diffusion calculations. Based...

  17. ENERGY STAR Certified Water Heaters

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 3.0 ENERGY STAR Program Requirements for Water Heaters that are effective April 16, 2015....

  18. ENERGY STAR Certified Commercial Dishwashers

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 2.0 ENERGY STAR Program Requirements for Commercial Dishwashers that are effective as of...

  19. Solid Bare Strange Quark Stars

    CERN Document Server

    Xu, R X

    2003-01-01

    The reason, we need three terms of `strange', `bare', and `solid' before quark stars, is presented concisely though some fundamental issues are not certain. Observations favoring these stars are introduced.

  20. ENERGY STAR Certified Vending Machines

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 3.0 ENERGY STAR Program Requirements for Refrigerated Beverage Vending Machines that are...

  1. ENERGY STAR Certified Residential Dishwashers

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 6.0 ENERGY STAR Program Requirements for Residential Dishwashers that are effective as of...

  2. ENERGY STAR Certified Commercial Fryers

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 3.0 ENERGY STAR Program Requirements for Commercial Fryers that are effective as of...

  3. Star Formation in Irregular Galaxies.

    Science.gov (United States)

    Hunter, Deidre; Wolff, Sidney

    1985-01-01

    Examines mechanisms of how stars are formed in irregular galaxies. Formation in giant irregular galaxies, formation in dwarf irregular galaxies, and comparisons with larger star-forming regions found in spiral galaxies are considered separately. (JN)

  4. OT1_hmaness_1: Planets, Debris Disks, and the Lambda Bootis Stars

    Science.gov (United States)

    Maness, H.

    2010-07-01

    We propose to explore the link between lambda Bootis stars, debris disks, and planetesimal formation and evolution. The lambda Boo stars are a rare type of peculiar A star (2%), which are Population 1 and metal poor. Planet bearing systems and debris disk stars appear unusually well represented in the lambda Boo class: for example, beta Pic, Vega, and HR 8799 are all lambda Boo candidates. A small sample of 14 lambda Boo stars observed by Spitzer suggests an occurrence of infrared excess approaching 100%. Only two lambda Boo stars are included in the DEBRIS/DUNES Herschel key program debris disk surveys. We will use PACS/Herschel to make sensitive, high-resolution maps of 27 new lambda Boo stars. Like DEBRIS/DUNES, we will reach the stellar photosphere for all targets, enabling a measurement of the true rate of excess infrared emission among lambda Boo stars compared to normal A stars. The depletion pattern of heavy elements in the atmospheres of lambda Boo stars suggests they may have accreted gas from which dust grains have condensed and been removed: this gas may be circumstellar gas that has formed planetesimals or dusty interstellar gas. While the circumstellar disk scenario predicts sizes of a few hundred AU, the cloud accretion scenario predicts 1000-2000 AU bow structures oriented in the direction of the relative motion of the cloud and star. With target distances of stars outside of the low density Local Bubble: if interstellar medium interactions dominate the lambda Boo phenomenon then systematic variations in excess strength and morphology may occur with distance.

  5. A meta-analysis of cosmic star-formation history

    CERN Document Server

    Hogg, D W

    2001-01-01

    A meta-analysis is performed of the literature on evolution in cosmic star-formation rate density from redshift unity to the present day. The measurements are extremely diverse, including radio, infrared, and ultraviolet broad-band photometric indicators, and visible and near-ultraviolet line-emission indicators. Although there is large scatter among indicators at any given redshift, virtually all studies find a significant decrease from redshift unity to the present day. This is the most heterogeneously confirmed result in the study of galaxy evolution. When comoving star-formation rate density is treated as being proportional to $(1+z)^{\\beta}$, the meta-analysis gives a best-fit exponent and conservative confidence interval of $\\beta= 3.1\\pm 0.7$ in a world model with $(\\Omega_M,\\Omega_{\\Lambda})=(0.3,0.7)$ and $\\beta= 3.8\\pm 0.8$ in $(\\Omega_M,\\Omega_{\\Lambda})=(1.0,0.0)$. In either case these evolutionary trends are strong enough that the bulk of the stellar mass at the present day ought to be in old ($>...

  6. On the accretion disc and evolutionary stage of beta Lyrae

    CERN Document Server

    Mennickent, R E

    2013-01-01

    We modeled the V-band light curve of beta Lyrae with two stellar components plus an optically thick accretion disc around the gainer assuming a semidetached configuration. We present the results of this calculation, giving physical parameters for the stars and the disc, along with general system dimensions. We discuss the evolutionary stage of the system finding the best match with one of the evolutionary models of Van Rensbergen et al. According to this model, the system is found at age 2.30E7 years, in the phase of rapid mass transfer, the second one in the life of this binary, in a Case-B mass-exchange stage with dM/dt = 1.58E-5 Msun/year. This result, along with the reported rate of orbital period change and observational evidence of mass loss, suggests that the mass transfer in beta Lyrae, is quasi-conservative. The best model indicates that beta Lyrae finished a relatively large mass loss episode 31400 years ago. The light curve model that best fit the observations has inclination angle i = 81 degree, M...

  7. In-trap decay spectroscopy for {beta}{beta} decays

    Energy Technology Data Exchange (ETDEWEB)

    Brunner, Thomas

    2011-01-18

    The presented work describes the implementation of a new technique to measure electron-capture (EC) branching ratios (BRs) of intermediate nuclei in {beta}{beta} decays. This technique has been developed at TRIUMF in Vancouver, Canada. It facilitates one of TRIUMF's Ion Traps for Atomic and Nuclear science (TITAN), the Electron Beam Ion Trap (EBIT) that is used as a spectroscopy Penning trap. Radioactive ions, produced at the radioactive isotope facility ISAC, are injected and stored in the spectroscopy Penning trap while their decays are observed. A key feature of this technique is the use of a strong magnetic field, required for trapping. It radially confines electrons from {beta} decays along the trap axis while X-rays, following an EC, are emitted isotropically. This provides spatial separation of X-ray and {beta} detection with almost no {beta}-induced background at the X-ray detector, allowing weak EC branches to be measured. Furthermore, the combination of several traps allows one to isobarically clean the sample prior to the in-trap decay spectroscopy measurement. This technique has been developed to measure ECBRs of transition nuclei in {beta}{beta} decays. Detailed knowledge of these electron capture branches is crucial for a better understanding of the underlying nuclear physics in {beta}{beta} decays. These branches are typically of the order of 10{sup -5} and therefore difficult to measure. Conventional measurements suffer from isobaric contamination and a dominating {beta} background at theX-ray detector. Additionally, X-rays are attenuated by the material where the radioactive sample is implanted. To overcome these limitations, the technique of in-trap decay spectroscopy has been developed. In this work, the EBIT was connected to the TITAN beam line and has been commissioned. Using the developed beam diagnostics, ions were injected into the Penning trap and systematic studies on injection and storage optimization were performed. Furthermore, Ge

  8. Molecular Gas Clumps from the Destruction of Icy Bodies in the $\\beta$ Pictoris Debris Disk

    CERN Document Server

    Dent, W R F; Roberge, A; Augereau, J -C; Casassus, S; Corder, S; Greaves, J S; de Gregorio-Monsalvo, I; Hales, A; Jackson, A P; Hughes, A Meredith; Lagrange, A -M; Matthews, B; Wilner, D

    2014-01-01

    Many stars are surrounded by disks of dusty debris formed in the collisions of asteroids, comets and dwarf planets. But is gas also released in such events? Observations at submm wavelengths of the archetypal debris disk around $\\beta$ Pictoris show that 0.3% of a Moon mass of carbon monoxide orbits in its debris belt. The gas distribution is highly asymmetric, with 30% found in a single clump 85AU from the star, in a plane closely aligned with the orbit of the inner planet, $\\beta$ Pic b. This gas clump delineates a region of enhanced collisions, either from a mean motion resonance with an unseen giant planet, or from the remnants of a collision of Mars-mass planets.

  9. Analysis of betaS and betaA genes in a Mexican population with African roots.

    Science.gov (United States)

    Magaña, María Teresa; Ongay, Zoyla; Tagle, Juan; Bentura, Gilberto; Cobián, José G; Perea, F Javier; Casas-Castañeda, Maricela; Sánchez-López, Yoaly J; Ibarra, Bertha

    2002-01-01

    To investigate the origin of the beta(A) and beta(S) genes in a Mexican population with African roots and a high frequency of hemoglobin S, we analyzed 467 individuals (288 unrelated) from different towns in the states of Guerrero and Oaxaca in the Costa Chica region. The frequency of the sickle-cell trait was 12.8%, which may represent a public health problem. The frequencies of the beta-haplotypes were determined from 350 nonrelated chromosomes (313 beta(A) and 37 beta(S)). We observed 15 different beta(A) haplotypes, the most common of which were haplotypes 1 (48.9%), 2 (13.4%), and 3 (13.4%). The calculation of pairwise distributions and Nei's genetic distance analysis using 32 worldwide populations showed that the beta(A) genes are more closely related to those of Mexican Mestizos and North Africans. Bantu and Benin haplotypes and haplotype 9 were related to the beta(S) genes, with frequencies of 78.8, 18.2, and 3.0%, respectively. Comparison of these haplotypes with 17 other populations revealed a high similitude with the population of the Central African Republic. These data suggest distinct origins for the beta(A) and beta(S) genes in Mexican individuals from the Costa Chica region.

  10. Beijing Star Lake Ecology Park

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Beijing Star Lake Ecology Park is a Five-star hotel which has developed multi-functions of restaurant, lodge, bath, landscape seeing, leisure,body exercise, recreation, Ecology agriculture,etc. Occupying an area of 500 mu, the park is an environmental friendly five-star hotel.

  11. Supernovae from massive AGB stars

    NARCIS (Netherlands)

    Poelarends, A.J.T.; Izzard, R.G.; Herwig, F.; Langer, N.; Heger, A.

    2006-01-01

    We present new computations of the final fate of massive AGB-stars. These stars form ONeMg cores after a phase of carbon burning and are called Super AGB stars (SAGB). Detailed stellar evolutionary models until the thermally pulsing AGB were computed using three di erent stellar evolution codes. The

  12. Hadrons in compact stars

    Indian Academy of Sciences (India)

    Debades Bandyopadhyay

    2006-05-01

    We discuss -equilibrated and charge neutral matter involving hyperons and $\\bar{K}$ condensates within relativistic models. It is observed that populations of baryons are strongly affected by the presence of antikaon condensates. Also, the equation of state including $\\bar{K}$ condensates becomes softer resulting in a smaller maximum mass neutron star.

  13. First Star I See.

    Science.gov (United States)

    Caffrey, Jaye Andras

    This children's novel tells the story of a young girl with attention deficit disorder (ADD) without hyperactivity and her younger brother who has ADD with hyperactivity. Trying to win a school writing contest on the topic of space and stars helps bright, imaginative Paige Bradley realize that fixing her "focusing knob" will compensate for her ADD.…

  14. Seismology of active stars

    NARCIS (Netherlands)

    Hekker, S.; García, R.A.

    2012-01-01

    In this review we will discuss the current standing and open questions of seismology in active stars. With the longer photometric time series data that are, and will become, available from space-missions such as Kepler we foresee significant progress in our understanding of stellar internal structur

  15. Trek to the Stars

    Science.gov (United States)

    Rubinstein, Robert E.

    1977-01-01

    "Star Trek", which was aired on television for three years, brought the creatures and conflicts of the "outer reaches" of space into our living rooms. Here its new episodes and reruns are analyzed by elementary students as part of a social studies/elementary science curriculum. (Author/RK)

  16. Magnetic Dynamos and Stars

    Energy Technology Data Exchange (ETDEWEB)

    Eggleton, P P

    2007-02-15

    Djehuty is a code that has been developed over the last five years by the Lawrence Livermore National Laboratory (LLNL), from earlier code designed for programmatic efforts. Operating in a massively parallel environment, Djehuty is able to model entire stars in 3D. The object of this proposal was to continue the effort to introduce magneto-hydrodynamics (MHD) into Djehuty, and investigate new classes of inherently 3D problems involving the structure, evolution and interaction of stars and planets. However, towards the end of the second year we discovered an unexpected physical process of great importance in the evolution of stars. Consequently for the third year we changed direction and concentrated on this process rather than on magnetic fields. Our new process was discovered while testing the code on red-giant stars, at the 'helium flash'. We found that a thin layer was regularly formed which contained a molecular-weight inversion, and which led therefore to Rayleigh-Taylor instability. This in turn led to some deeper-than-expected mixing, which has the property that (a) much {sup 3}He is consumed, and (b) some {sup 13}C is produced. These two properties are closely in accord with what has been observed over the last thirty years in red giants, whereas what was observed was largely in contradiction to what earlier theoretical models predicted. Thus our new 3D models with Djehuty explain a previously-unexplained problem of some thirty years standing.

  17. Housing Star Schools Reforms.

    Science.gov (United States)

    Tushnet, Naida C.

    The Star Schools Program has funded projects to explore innovative educational applications of technology in distance education. Funded projects have applied a variety of technologies, including videodisks, compressed data transmission, fiber optic technology, and computer networks. Program evaluation is a mandated aspect of the program. This…

  18. Reaching for the Stars

    Science.gov (United States)

    Terry, Dorothy Givens

    2012-01-01

    Dr. Mae Jemison is the world's first woman astronaut of color who continues to reach for the stars. Jemison was recently successful in leading a team that has secured a $500,000 federal grant to make interstellar space travel a reality. The Dorothy Jemison Foundation for Excellence (named after Jemison's mother) was selected in June by the Defense…

  19. StarLogo TNG

    Science.gov (United States)

    Klopfer, Eric; Scheintaub, Hal; Huang, Wendy; Wendel, Daniel

    Computational approaches to science are radically altering the nature of scientific investigatiogn. Yet these computer programs and simulations are sparsely used in science education, and when they are used, they are typically “canned” simulations which are black boxes to students. StarLogo The Next Generation (TNG) was developed to make programming of simulations more accessible for students and teachers. StarLogo TNG builds on the StarLogo tradition of agent-based modeling for students and teachers, with the added features of a graphical programming environment and a three-dimensional (3D) world. The graphical programming environment reduces the learning curve of programming, especially syntax. The 3D graphics make for a more immersive and engaging experience for students, including making it easy to design and program their own video games. Another change to StarLogo TNG is a fundamental restructuring of the virtual machine to make it more transparent. As a result of these changes, classroom use of TNG is expanding to new areas. This chapter is concluded with a description of field tests conducted in middle and high school science classes.

  20. The Star Formation Camera

    CERN Document Server

    Scowen, Paul A; Beasley, Matthew; Calzetti, Daniela; Desch, Steven; Fullerton, Alex; Gallagher, John; Lisman, Doug; Macenka, Steve; Malhotra, Sangeeta; McCaughrean, Mark; Nikzad, Shouleh; O'Connell, Robert; Oey, Sally; Padgett, Deborah; Rhoads, James; Roberge, Aki; Siegmund, Oswald; Shaklan, Stuart; Smith, Nathan; Stern, Daniel; Tumlinson, Jason; Windhorst, Rogier; Woodruff, Robert

    2009-01-01

    The Star Formation Camera (SFC) is a wide-field (~15'x19, >280 arcmin^2), high-resolution (18x18 mas pixels) UV/optical dichroic camera designed for the Theia 4-m space-borne space telescope concept. SFC will deliver diffraction-limited images at lambda > 300 nm in both a blue (190-517nm) and a red (517-1075nm) channel simultaneously. Our aim is to conduct a comprehensive and systematic study of the astrophysical processes and environments relevant for the births and life cycles of stars and their planetary systems, and to investigate and understand the range of environments, feedback mechanisms, and other factors that most affect the outcome of the star and planet formation process. This program addresses the origins and evolution of stars, galaxies, and cosmic structure and has direct relevance for the formation and survival of planetary systems like our Solar System and planets like Earth. We present the design and performance specifications resulting from the implementation study of the camera, conducted ...

  1. Sleeping under the stars

    Science.gov (United States)

    Zirkel, Jack

    Sherlock Holmes and Dr. Watson went on a camping trip. As they lay down for the night, Holmes said, “Watson, look up at the sky and tell me what you see.”Watson:“! see millions and millions of stars.”

  2. Herschel detects oxygen in the beta Pictoris debris disk

    CERN Document Server

    Brandeker, A; Olofsson, G; Vandenbussche, B; Acke, B; Barlow, M J; Blommaert, J A D L; Cohen, M; Dent, W R F; Dominik, C; Di Francesco, J; Fridlund, M; Gear, W K; Glauser, A M; Greaves, J S; Harvey, P M; Heras, A M; Hogerheijde, M R; Holland, W S; Huygen, R; Ivison, R J; Leeks, S J; Lim, T L; Liseau, R; Matthews, B C; Pantin, E; Pilbratt, G L; Royer, P; Sibthorpe, B; Waelkens, C; Walker, H J

    2016-01-01

    The young star beta Pictoris is well known for its dusty debris disk, produced through the grinding down by collisions of planetesimals, kilometre-sized bodies in orbit around the star. In addition to dust, small amounts of gas are also known to orbit the star, likely the result from vaporisation of violently colliding dust grains. The disk is seen edge on and from previous absorption spectroscopy we know that the gas is very rich in carbon relative to other elements. The oxygen content has been more difficult to assess, however, with early estimates finding very little oxygen in the gas at a C/O ratio 20x higher than the cosmic value. A C/O ratio that high is difficult to explain and would have far-reaching consequences for planet formation. Here we report on observations by the far-infrared space telescope Herschel, using PACS, of emission lines from ionised carbon and neutral oxygen. The detected emission from C+ is consistent with that previously reported being observed by the HIFI instrument on Herschel,...

  3. beta (+)-Thalassaemia in the Po river delta region (northern Italy): genotype and beta globin synthesis.

    Science.gov (United States)

    Del Senno, L; Pirastu, M; Barbieri, R; Bernardi, F; Buzzoni, D; Marchetti, G; Perrotta, C; Vullo, C; Kan, Y W; Conconi, F

    1985-01-01

    Six beta(+)-thalassaemic patients from the Po river delta region have been studied. Using synthetic oligonucleotides as specific hybridisation probes, the beta(+) IVS I mutation (G----A at position 108) was demonstrated. This lesion and the enzyme polymorphism pattern in the subjects examined are the same as have been described for other Mediterranean beta(+)-thalassaemias. Antenatal diagnosis through DNA analysis of beta(+)-thalassaemia is therefore possible. The production of beta globin in a beta(+), homozygote and in a beta (+), beta(0) 39 (nonsense mutation at codon 39) double heterozygote is approximately 20% and 10% respectively of total non-alpha globin synthesis. Despite some overlapping of the results, similar beta globin synthesis levels have been obtained in 43 beta(+)-thalassaemia patients. This suggests that in the Po river delta region the most common thalassaemic genes are beta(0) 39 and beta(+) IVS I. Images PMID:2580095

  4. THE GEMINI PLANET-FINDING CAMPAIGN: THE FREQUENCY OF GIANT PLANETS AROUND DEBRIS DISK STARS

    Energy Technology Data Exchange (ETDEWEB)

    Wahhaj, Zahed [European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago (Chile); Liu, Michael C.; Nielsen, Eric L.; Ftaclas, Christ; Chun, Mark [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Biller, Beth A. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Hayward, Thomas L. [Gemini Observatory, Southern Operations Center, c/o AURA, Casilla 603, La Serena (Chile); Close, Laird M.; Males, Jared R.; Skemer, Andrew [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Thatte, Niranjan; Tecza, Matthias [Department of Astronomy, University of Oxford, DWB, Keble Road, Oxford OX1 3RH (United Kingdom); Shkolnik, Evgenya L. [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Kuchner, Marc [NASA Goddard Space Flight Center, Exoplanets and Stellar Astrophysics Laboratory, Greenbelt, MD 20771 (United States); Reid, I. Neill [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); De Gouveia Dal Pino, Elisabete M.; Gregorio-Hetem, Jane [Departamento de Astronomia, Universidade de Sao Paulo, IAG/USP, Rua do Matao 1226, 05508-900 Sao Paulo, SP (Brazil); Alencar, Silvia H. P. [Departamento de Fisica-ICEx-UFMG, Av. Antonio Carlos 6627, 30270-901 Belo Horizonte, MG (Brazil); Boss, Alan [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015 (United States); Lin, Douglas N. C. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA (United States); and others

    2013-08-20

    We have completed a high-contrast direct imaging survey for giant planets around 57 debris disk stars as part of the Gemini NICI Planet-Finding Campaign. We achieved median H-band contrasts of 12.4 mag at 0.''5 and 14.1 mag at 1'' separation. Follow-up observations of the 66 candidates with projected separation <500 AU show that all of them are background objects. To establish statistical constraints on the underlying giant planet population based on our imaging data, we have developed a new Bayesian formalism that incorporates (1) non-detections, (2) single-epoch candidates, (3) astrometric and (4) photometric information, and (5) the possibility of multiple planets per star to constrain the planet population. Our formalism allows us to include in our analysis the previously known {beta} Pictoris and the HR 8799 planets. Our results show at 95% confidence that <13% of debris disk stars have a {>=}5 M{sub Jup} planet beyond 80 AU, and <21% of debris disk stars have a {>=}3 M{sub Jup} planet outside of 40 AU, based on hot-start evolutionary models. We model the population of directly imaged planets as d {sup 2} N/dMda{proportional_to}m {sup {alpha}} a {sup {beta}}, where m is planet mass and a is orbital semi-major axis (with a maximum value of a{sub max}). We find that {beta} < -0.8 and/or {alpha} > 1.7. Likewise, we find that {beta} < -0.8 and/or a{sub max} < 200 AU. For the case where the planet frequency rises sharply with mass ({alpha} > 1.7), this occurs because all the planets detected to date have masses above 5 M{sub Jup}, but planets of lower mass could easily have been detected by our search. If we ignore the {beta} Pic and HR 8799 planets (should they belong to a rare and distinct group), we find that <20% of debris disk stars have a {>=}3 M{sub Jup} planet beyond 10 AU, and {beta} < -0.8 and/or {alpha} < -1.5. Likewise, {beta} < -0.8 and/or a{sub max} < 125 AU. Our Bayesian constraints are not strong enough to reveal any dependence

  5. Star identification methods, techniques and algorithms

    CERN Document Server

    Zhang, Guangjun

    2017-01-01

    This book summarizes the research advances in star identification that the author’s team has made over the past 10 years, systematically introducing the principles of star identification, general methods, key techniques and practicable algorithms. It also offers examples of hardware implementation and performance evaluation for the star identification algorithms. Star identification is the key step for celestial navigation and greatly improves the performance of star sensors, and as such the book include the fundamentals of star sensors and celestial navigation, the processing of the star catalog and star images, star identification using modified triangle algorithms, star identification using star patterns and using neural networks, rapid star tracking using star matching between adjacent frames, as well as implementation hardware and using performance tests for star identification. It is not only valuable as a reference book for star sensor designers and researchers working in pattern recognition and othe...

  6. Pulsating B-type stars in the open cluster NGC 884: frequencies, mode identification and asteroseismology

    CERN Document Server

    Saesen, S; Aerts, C; Miglio, A; Carrier, F

    2013-01-01

    Recent progress in the seismic interpretation of field beta Cep stars has resulted in improvements of the physics in the stellar structure and evolution models of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance and chemical composition. We present an observational asteroseismology study based on the discovery of numerous multi-periodic and mono-periodic B-stars in the open cluster NGC 884. We describe a thorough investigation of the pulsational properties of all B-type stars in the cluster. Overall, our detailed frequency analysis resulted in 115 detected frequencies in 65 stars. We found 36 mono-periodic, 16 bi-periodic, 10 tri-periodic, and 2 quadru-periodic stars and one star with 9 independent frequencies. We also derived the amplitudes and phases of all detected frequencies in the U, B, V and I filter, if available. We achieved unambiguous identifications of the mode degree for twelve of the de...

  7. Smart Beta or Smart Alpha

    DEFF Research Database (Denmark)

    Winther, Kenneth Lillelund; Steenstrup, Søren Resen

    2016-01-01

    Smart beta has become the flavor of the decade in the investment world with its low fees, easy access to rewarded risk premiums, and appearance of providing good investment results relative to both traditional passive benchmarks and actively managed funds. Although we consider it well documented...... that smart beta investing probably will do better than passive market capitalization investing over time, we believe many are coming to a conclusion too quickly regarding active managers. Institutional investors are able to guide managers through benchmarks and risk frameworks toward the same well......-documented smart beta risk premiums and still motivate active managers to avoid value traps, too highly priced small caps, defensives, etc. By constructing the equity portfolios of active managers that resemble the most widely used risk premiums, we show that the returns and risk-adjusted returns measures...

  8. Swift, UVOT and Hot Stars

    CERN Document Server

    Siegel, Michael H; Hagen, Lea M Z; Hoversten, Erik A

    2015-01-01

    We present the results of our ongoing investigation into the properties of hot stars and young stellar populations using the Swift/UVOT telescope. We present UVOT photometry of open and globular clusters and show that UVOT is capable of characterizing a variety of rare hot stars, including Post-Asymptotic Giant Branch and Extreme Horizontal Branch Stars. We also present very early reults of our survey of stellar populations in the Small Magellanic Cloud. We find that the SMC has experienced recent bouts of star formation but constraining the exact star formation history will depend on finding an effective model of the reddening within the SMC.

  9. Automatic phylogenetic classification of bacterial beta-lactamase sequences including structural and antibiotic substrate preference information.

    Science.gov (United States)

    Ma, Jianmin; Eisenhaber, Frank; Maurer-Stroh, Sebastian

    2013-12-01

    Beta lactams comprise the largest and still most effective group of antibiotics, but bacteria can gain resistance through different beta lactamases that can degrade these antibiotics. We developed a user friendly tree building web server that allows users to assign beta lactamase sequences to their respective molecular classes and subclasses. Further clinically relevant information includes if the gene is typically chromosomal or transferable through plasmids as well as listing the antibiotics which the most closely related reference sequences are known to target and cause resistance against. This web server can automatically build three phylogenetic trees: the first tree with closely related sequences from a Tachyon search against the NCBI nr database, the second tree with curated reference beta lactamase sequences, and the third tree built specifically from substrate binding pocket residues of the curated reference beta lactamase sequences. We show that the latter is better suited to recover antibiotic substrate assignments through nearest neighbor annotation transfer. The users can also choose to build a structural model for the query sequence and view the binding pocket residues of their query relative to other beta lactamases in the sequence alignment as well as in the 3D structure relative to bound antibiotics. This web server is freely available at http://blac.bii.a-star.edu.sg/.

  10. Orbital Constraints on the (beta) Pic Inner Planet Candidate with Keck Adaptive Optics

    Energy Technology Data Exchange (ETDEWEB)

    Fitzgerald, M P; Kalas, P G; Graham, J R

    2009-09-23

    A point source observed 8AU in projection from {beta} Pictoris in L{prime} (3.8 {micro}m) imaging in 2003 has been recently presented as a planet candidate. Here we show the results of L{prime}-band adaptive optics imaging obtained at Keck Observatory in 2008. We do not detect {beta} Pic b beyond a limiting radius of 0.29-inch, or 5.5AU in projection, from the star. If {beta} Pic b is an orbiting planet, then it has moved {ge} 0.12-inch (2.4AU in projection) closer to the star in the five years separating the two epochs of observation. We examine the range of orbital parameters consistent with the observations, including likely bounds from the locations of previously inferred planetesimal belts. We find a family of low-eccentricity orbits with semimajor axes {approx} 8-9AU that are completely allowed, as well as a broad region of orbits with e {approx}< 0.2, a {approx}> 10AU that are allowed if the apparent motion of the planet was towards the star in 2003. We compare this allowed space with predictions of the planetary orbital elements from the literature. Additionally, we show how similar observations in the next several years can further constrain the space of allowed orbits. Non-detections of the source through 2013 will exclude the interpretation of the candidate as a planet orbiting between the 6.4 and 16AU planetesimal belts.

  11. The microbial oxidation of (-)-beta-pinene by Botrytis cinerea.

    Science.gov (United States)

    Farooq, Afgan; Choudhary, M Iqbal; Tahara, Satoshi; Rahman, Atta-ur; Başer, K Hüsnü Can; Demirci, Fatih

    2002-01-01

    (-)-beta-pinene, a flavor and fragrance monoterpene is an important constituent of essential oils of many aromatic plants. It was oxidized by a plant-pathogenic fungus, Botrytis cinerea to afford four metabolites characterized as (-)-6a-hydroxy-beta-pinene, (-)-4beta,5beta-dihydroxy-beta-pinene, (-)-2beta,3beta-dihydroxypinane, and (-)-4beta-hydroxy-beta-pinene-6-one by detailed spectroscopic studies along with other known metabolites.

  12. Neutrinoless double beta decay experiments

    CERN Document Server

    Zuber, K

    2006-01-01

    The study of neutrinoless double beta decay is of outmost importance for neutrino physics. It is considered to be the gold plated channel to probe the fundamental character of neutrinos and to determine the neutrino mass. From the experimental point about nine different isotopes are explored for the search. After a general introduction follows a short discussion on nuclear matrix element calculations and supportive measurements. The current experimental status of double beta searches is presented followed by a short discussion of the ideas and proposals for large scale experiments.

  13. Star Cluster Formation and Feedback

    CERN Document Server

    Krumholz, Mark R; Arce, Hector G; Dale, James E; Gutermuth, Robert; Klein, Richard I; Li, Zhi-Yun; Nakamura, Fumitaka; Zhang, Qizhou

    2014-01-01

    Stars do not generally form in isolation. Instead, they form in clusters, and in these clustered environments newborn stars can have profound effects on one another and on their parent gas clouds. Feedback from clustered stars is almost certainly responsible for a number of otherwise puzzling facts about star formation: that it is an inefficient process that proceeds slowly when averaged over galactic scales; that most stars disperse from their birth sites and dissolve into the galactic field over timescales $\\ll 1$ Gyr; and that newborn stars follow an initial mass function (IMF) with a distinct peak in the range $0.1 - 1$ $M_\\odot$, rather than an IMF dominated by brown dwarfs. In this review we summarize current observational constraints and theoretical models for the complex interplay between clustered star formation and feedback.

  14. Ecology of blue straggler stars

    CERN Document Server

    Carraro, Giovanni; Beccari, Giacomo

    2015-01-01

    The existence of blue straggler stars, which appear younger, hotter, and more massive than their siblings, is at odds with a simple picture of stellar evolution. Such stars should have exhausted their nuclear fuel and evolved long ago to become cooling white dwarfs. They are found to exist in globular clusters, open clusters, dwarf spheroidal galaxies of the Local Group, OB associations and as field stars. This book summarises the many advances in observational and theoretical work dedicated to blue straggler stars. Carefully edited extended contributions by well-known experts in the field cover all the relevant aspects of blue straggler stars research: Observations of blue straggler stars in their various environments; Binary stars and formation channels; Dynamics of globular clusters; Interpretation of observational data and comparison with models. The book also offers an introductory chapter on stellar evolution written by the editors of the book.

  15. A {beta} - {gamma} coincidence; Metodo de coincidencias {beta} - {gamma}

    Energy Technology Data Exchange (ETDEWEB)

    Agullo, F.

    1960-07-01

    A {beta} - {gamma} coincidence method for absolute counting is given. The fundamental principles are revised and the experimental part is detailed. The results from {sup 1}98 Au irradiated in the JEN 1 Swimming pool reactor are given. The maximal accuracy is 1 per cent. (Author) 11 refs.

  16. Beta thalassaemia mutations in Turkish Cypriots.

    Science.gov (United States)

    Sozuoz, A; Berkalp, A; Figus, A; Loi, A; Pirastu, M; Cao, A

    1988-01-01

    Using oligonucleotide hybridisation or restriction endonuclease analysis, we have characterised the molecular defect in 94 patients with thalassaemia major and four with thalassaemia intermedia of Turkish Cypriot descent. We found that four mutations, namely beta+ IVS-1 nt 110, beta zero IVS-1 nt, beta+ IVS-1 nt 6, and beta+ IVS-2 nt 745 were prevalent, accounting for 69.9%, 11.7%, 8.7%, and 5.6% respectively of the beta thalassaemia chromosomes. This information may help in the organisation of a large scale prevention programme based on fetal diagnosis of beta thalassaemia by DNA analysis in the Turkish population. PMID:3236356

  17. Neutron Star Science with the NuSTAR

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, J. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-10-16

    The Nuclear Spectroscopic Telescope Array (NuSTAR), launched in June 2012, helped scientists obtain for the first time a sensitive high-­energy X-­ray map of the sky with extraordinary resolution. This pioneering telescope has aided in the understanding of how stars explode and neutron stars are born. LLNL is a founding member of the NuSTAR project, with key personnel on its optics and science team. We used NuSTAR to observe and analyze the observations of different neutron star classes identified in the last decade that are still poorly understood. These studies not only help to comprehend newly discovered astrophysical phenomena and emission processes for members of the neutron star family, but also expand the utility of such observations for addressing broader questions in astrophysics and other physics disciplines. For example, neutron stars provide an excellent laboratory to study exotic and extreme phenomena, such as the equation of state of the densest matter known, the behavior of matter in extreme magnetic fields, and the effects of general relativity. At the same time, knowing their accurate populations has profound implications for understanding the life cycle of massive stars, star collapse, and overall galactic evolution.

  18. On the Carbon-Star Status of Five Stars in a New Carbon Star Catalog

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    We find that five sources listed in the new carbon star catalog are not really carbon-rich objects but oxygen-rich stars, because they all have the prominent 10μm silicate features in absorption and the 1612 MHz OH maser emission or/and the SiO molecular features. These objects were considered as carbon stars in the catalog based only on their locations in the infrared two-color diagram. Therefore to use the infrared two-color diagram to distinguish carbon-rich stars from oxygenrich stars must be done with caution, because, in general, it has only a statistical meaning.

  19. The Secret XUV Lives of Cepheids: FUV/X-ray Observations of Polaris and beta Dor

    CERN Document Server

    Engle, Scott G; DePasquale, Joseph; Evans, Nancy

    2009-01-01

    We report on the surprising recent discovery of strong FUV emissions in two bright, nearby Classical Cepheids from analyses of FUSE archival observations and one of our own approved observations just prior to the failure of the satellite. Polaris and beta Dor are currently the only two Cepheids to have been observed with FUSE, and beta Dor is the only one to have multiple spectra. Both Cepheids show strong C III (977A, 1176A) and O VI (1032A, 1038A) emissions, indicative of 50,000-500,000 K plasma, well above the photospheric temperatures of the stars. More remarkably, beta Dor displays variability in the FUV emission strengths which appears to be correlated to its 9.84-d pulsation period. This phenomenon has never before been observed in Cepheids. The FUV studies are presented along with our recent Chandra/XMM X-ray observations of Polaris and beta Dor, in which X-ray detections were found for both stars (as well as for the prototype Classical Cepheid, delta Cep). Further X-ray observations have been propose...

  20. The challenge of measuring magnetic fields in strongly pulsating stars: the case of HD 96446

    CERN Document Server

    Järvinen, S P; Ilyin, I; Schöller, M; Briquet, M

    2016-01-01

    Among the early B-type stars, He-rich Bp stars exhibit the strongest large-scale organized magnetic fields with a predominant dipole contribution. The presence of $\\beta$ Cep-like pulsations in the typical magnetic early Bp-type star HD 96446 was announced a few years ago, but the analysis of the magnetic field geometry was hampered by the absence of a reliable rotation period and a sophisticated procedure for accounting for the impact of pulsations on the magnetic field measurements. Using new spectropolarimetric observations and a recently determined rotation period based on an extensive spectroscopic time series, we investigate the magnetic field model parameters of this star under more detailed considerations of the pulsation behaviour of the line profiles.

  1. The effect of starspots on the radii of low-mass pre-main sequence stars

    CERN Document Server

    Jackson, R J

    2014-01-01

    A polytropic model is used to investigate the effects of dark photospheric spots on the evolution and radii of magnetically active, low-mass (M<0.5Msun), pre-main sequence (PMS) stars. Spots slow the contraction along Hayashi tracks and inflate the radii of PMS stars by a factor of (1-beta)^{-N} compared to unspotted stars of the same luminosity, where beta is the equivalent covering fraction of dark starspots and N \\simeq 0.45+/-0.05. This is a much stronger inflation than predicted by the models of Spruit & Weiss (1986) for main sequence stars with the same beta, where N \\sim 0.2 to 0.3. These models have been compared to radii determined for very magnetically active K- and M-dwarfs in the young Pleiades and NGC 2516 clusters, and the radii of tidally-locked, low-mass eclipsing binary components. The binary components and ZAMS K-dwarfs have radii inflated by \\sim 10 per cent compared to an empirical radius-luminosity relation that is defined by magnetically inactive field dwarfs with interferometrica...

  2. Pulsating stars harbouring planets

    Directory of Open Access Journals (Sweden)

    Moya A.

    2013-04-01

    Full Text Available Why bother with asteroseismology while studying exoplanets? There are several answers to this question. Asteroseismology and exoplanetary sciences have much in common and the synergy between the two opens up new aspects in both fields. These fields and stellar activity, when taken together, allow maximum extraction of information from exoplanet space missions. Asteroseismology of the host star has already proved its value in a number of exoplanet systems by its unprecedented precision in determining stellar parameters. In addition, asteroseismology allows the possibility of discovering new exoplanets through time delay studies. The study of the interaction between exoplanets and their host stars opens new windows on various physical processes. In this review I will summarize past and current research in exoplanet asteroseismology and explore some guidelines for the future.

  3. Shooting Star Experiment

    Science.gov (United States)

    1997-01-01

    The Shooting Star Experiment (SSE) is designed to develop and demonstrate the technology required to focus the sun's energy and use the energy for inexpensive space Propulsion Research. Pictured is an engineering model (Pathfinder III) of the Shooting Star Experiment (SSE). This model was used to test and characterize the motion and deformation of the structure caused by thermal effects. In this photograph, alignment targets are being placed on the engineering model so that a theodolite (alignment telescope) could be used to accurately measure the deformation and deflections of the engineering model under extreme conditions, such as the coldness of deep space and the hotness of the sun as well as vacuum. This thermal vacuum test was performed at the X-Ray Calibration Facility because of the size of the test article and the capabilities of the facility to simulate in-orbit conditions

  4. Fab Four Neutron Stars

    CERN Document Server

    Maselli, Andrea; Minamitsuji, Masato; Berti, Emanuele

    2016-01-01

    Horndeski's theory of gravity is the most general scalar-tensor theory with a single scalar whose equations of motion contain at most second-order derivatives. A subsector of Horndeski's theory known as "Fab Four" gravity allows for dynamical self-tuning of the quantum vacuum energy, and therefore it has received particular attention in cosmology as a possible alternative to the $\\Lambda$CDM model. Here we study compact stars in Fab Four gravity, which includes as special cases general relativity ("George"), Einstein-dilaton-Gauss-Bonnet gravity ("Ringo"), theories with a nonminimal coupling with the Einstein tensor ("John") and theories involving the double-dual of the Riemann tensor ("Paul"). We generalize and extend previous results in theories of the John class and we show that there are no viable compact star solutions in theories of the Paul class.

  5. Collapse of Axion Stars

    CERN Document Server

    Eby, Joshua; Suranyi, Peter; Wijewardhana, L C R

    2016-01-01

    Axion stars, gravitationally bound states of low-energy axion particles, have a maximum mass allowed by gravitational stability. Weakly bound states obtaining this maximum mass have sufficiently large radii such that they are dilute, and as a result, they are well described by a leading-order expansion of the axion potential. Heavier states are susceptible to gravitational collapse. Inclusion of higher-order interactions, present in the full potential, can give qualitatively different results in the analysis of collapsing heavy states, as compared to the leading-order expansion. In this work, we find that collapsing axion stars are stabilized by repulsive interactions present in the full potential, providing evidence that such objects do not form black holes. These dense configurations, which are the endpoints of collapse, have extremely high binding energy, and as a result, decay through number changing $3\\,a\\rightarrow a$ interactions with an extremely short lifetime.

  6. Searching for Classical Be Stars from the LAMOST DR1

    CERN Document Server

    Lin, C C; Chen, L; Shao, Z Y; Zhong, J; Yu, P C

    2015-01-01

    We report on searching for Classical B-type emission-line (CBe) stars from the first data release (DR1) of the Large Sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST; also named the Guoshoujing Telescope). A total of 192 (12 known CBes) objects were identified as CBe candidates with prominent He~I~$\\lambda4387$, He~I~$\\lambda4471$, and Mg~II~$\\lambda4481$ absorption lines, as well as H$\\beta$~$\\lambda4861$ and H$\\alpha$~$\\lambda6563$ emission lines. These candidates significantly increases current CBe sample of about 8\\%. Most of the CBe candidates are distributed at the Galactic Anti-Center due to the LAMOST observing strategy. Only two of CBes are in the star clusters with ages of 15.8 and 398~Myr, respectively.

  7. TTVs analysis in Southern Stars: the case of WASP-28

    CERN Document Server

    Petrucci, Romina; Melita, Mario; Gómez, Mercedes; Mauas, Pablo

    2014-01-01

    We present 4 new transit observations of the exoplanet WASP-28b observed between August 2011 and October 2013. Employing another 11 transits available in the literature we compute new ephemeris and redetermine the physical parameters of the star and the exoplanet. Considering 3 yrs of observations, we find no periodic TTVs or long-term variations of the inclination of the orbit, i, or the depth of the transit, k, that could be attributable to the presence of another planetary mass-body in the system. We also study the relations between i and k with different factors that characterize the light-curves. The fits suggest a possible weak correlation between k with the red noise factor, \\b{eta}, and the photometric noise rate, PNR, and a weak anticorrelation between i and PNR, although more points are needed to confirm these trends. Finally, the kinematic study suggests that WASP-28 is a thin disk star.

  8. Magnetic Doppler Imaging of He-strong star HD 184927

    CERN Document Server

    Yakunin, I; Bohlender, D; Kochukhov, O; Tsymbal, V

    2013-01-01

    We have employed an extensive new timeseries of Stokes I and V spectra obtained with the ESPaDOnS spectropolarimeter at the 3.6-m Canada-France-Hawaii Telescope to investigate the physical parameters, chemical abundance distributions and magnetic field topology of the slowly-rotating He-strong star HD 184927. We infer a rotation period of 9.53071+-0.00120 from H-alpha, H-beta, LSD magnetic measurements and EWs of helium lines. We used an extensive NLTE TLUSTY grid along with the SYNSPEC code to model the observed spectra and find a new value of luminosity. In this poster we present the derived physical parameters of the star and the results of Magnetic Doppler Imaging analysis of the Stokes I and V profiles. Wide wings of helium lines can be described only under the assumption of the presence of a large, very helium-rich spot.

  9. Oscillations in neutron stars

    Energy Technology Data Exchange (ETDEWEB)

    Hoeye, Gudrun Kristine

    1999-07-01

    We have studied radial and nonradial oscillations in neutron stars, both in a general relativistic and non-relativistic frame, for several different equilibrium models. Different equations of state were combined, and our results show that it is possible to distinguish between the models based on their oscillation periods. We have particularly focused on the p-, f-, and g-modes. We find oscillation periods of II approx. 0.1 ms for the p-modes, II approx. 0.1 - 0.8 ms for the f-modes and II approx. 10 - 400 ms for the g-modes. For high-order (l (>{sub )} 4) f-modes we were also able to derive a formula that determines II{sub l+1} from II{sub l} and II{sub l-1} to an accuracy of 0.1%. Further, for the radial f-mode we find that the oscillation period goes to infinity as the maximum mass of the star is approached. Both p-, f-, and g-modes are sensitive to changes in the central baryon number density n{sub c}, while the g-modes are also sensitive to variations in the surface temperature. The g-modes are concentrated in the surface layer, while p- and f-modes can be found in all parts of the star. The effects of general relativity were studied, and we find that these are important at high central baryon number densities, especially for the p- and f-modes. General relativistic effects can therefore not be neglected when studying oscillations in neutron stars. We have further developed an improved Cowling approximation in the non-relativistic frame, which eliminates about half of the gap in the oscillation periods that results from use of the ordinary Cowling approximation. We suggest to develop an improved Cowling approximation also in the general relativistic frame. (Author)

  10. John Goodricke, Edward Pigott, and Their Study of Variable Stars

    CERN Document Server

    French, L M

    2012-01-01

    John Goodricke and Edward Pigott, working in York, England, between 1781 and 1786, determined the periods of variation of eclipsing binaries such as Algol and Beta Lyrae and speculated that the eclipses of Algol might be caused by a "dark body," perhaps even a planet. They also determined the periods of variation of the first two known Cepheid variables, the stars whose period-luminosity relation today enables astronomers to determine distances to distant galaxies. Goodricke holds special interest because he was completely deaf and because he died at the age of 21. The lives and work of these two astronomers are described.

  11. The neutron star inner crust and symmetry energy

    CERN Document Server

    Grill, Fabrizio; Providência, Constança

    2012-01-01

    The cell structure of clusters in the inner crust of a cold \\beta-equilibrium neutron star is studied within a Thomas Fermi approach and compared with other approaches which include shell effects. Relativistic nuclear models are considered. We conclude that the symmetry energy slope L may have quite dramatic effects on the cell structure if it is very large or small. Rod-like and slab-like pasta clusters have been obtained in all models except one with a large slope L.

  12. ROLE OF NUCLEONIC FERMI SURFACE DEPLETION IN NEUTRON STAR COOLING

    Energy Technology Data Exchange (ETDEWEB)

    Dong, J. M.; Zuo, W. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Lombardo, U. [Universita di Catania and Laboratori Nazionali del Sud (INFN), Catania I-95123 (Italy); Zhang, H. F. [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China)

    2016-01-20

    The Fermi surface depletion of beta-stable nuclear matter is calculated to study its effects on several physical properties that determine the neutron star (NS) thermal evolution. The neutron and proton Z factors measuring the corresponding Fermi surface depletions are calculated within the Brueckner–Hartree–Fock approach, employing the AV18 two-body force supplemented by a microscopic three-body force. Neutrino emissivity, heat capacity, and in particular neutron {sup 3}PF{sub 2} superfluidity, turn out to be reduced, especially at high baryonic density, to such an extent that the cooling rates of young NSs are significantly slowed.

  13. Beta Cell Workshop 2013 Kyoto

    DEFF Research Database (Denmark)

    Heller, R Scott; Madsen, Ole D; Nielsen, Jens Høiriis

    2013-01-01

    The very modern Kyoto International Conference Center provided the site for the 8th workshop on Beta cells on April 23-26, 2013. The preceding workshops were held in Boston, USA (1991); Kyoto, Japan (1994); Helsingør, Denmark (1997); Helsinki, Finland (2003); El Perello, Spain (2006); Peebles...

  14. Estimating $\\beta$-mixing coefficients

    CERN Document Server

    McDonald, Daniel J; Schervish, Mark

    2011-01-01

    The literature on statistical learning for time series assumes the asymptotic independence or ``mixing' of the data-generating process. These mixing assumptions are never tested, nor are there methods for estimating mixing rates from data. We give an estimator for the $\\beta$-mixing rate based on a single stationary sample path and show it is $L_1$-risk consistent.

  15. Beta-carotene as antioxidant

    NARCIS (Netherlands)

    Bast, A.; Plas, R.M. van der; Berg, H. van den; Haenen, G.R.M.M.

    1996-01-01

    Objective: Beta-carotene has been shown to exhibit a good radical-trapping antioxidant activity in vitro. We were interested to see if dietary β-carotene in combination with various intake levels for vitamin A would also inhibit lipid peroxidation. Design: Sixty male Wistar rats received vitamin A (

  16. Asteroseismology of Pulsating Stars

    Indian Academy of Sciences (India)

    Santosh Joshi; Yogesh C. Joshi

    2015-03-01

    The success of helioseismology is due to its capability of measuring -mode oscillations in the Sun. This allows us to extract information on the internal structure and rotation of the Sun from the surface to the core. Similarly, asteroseismology is the study of the internal structure of the stars as derived from stellar oscillations. In this review we highlight the progress in the observational asteroseismology, including some basic theoretical aspects. In particular, we discuss our contributions to asteroseismology through the study of chemically peculiar stars under the 'Nainital-Cape Survey' project being conducted at ARIES, Nainital, since 1999. This survey aims to detect new rapidly-pulsating Ap (roAp) stars in the northern hemisphere. We also discuss the contribution of ARIES towards the asteroseismic study of the compact pulsating variables. We comment on the future prospects of our project in the light of the new optical 3.6-m telescope to be installed at Devasthal (ARIES). Finally, we present a preliminary optical design of the high-speed imaging photometers for this telescope.

  17. What are the stars?

    CERN Document Server

    Srinivasan, Ganesan

    2014-01-01

    The outstanding question in astronomy at the turn of the twentieth century was: What are the stars and why are they as they are? In this volume, the story of how the answer to this fundamental question was unravelled is narrated in an informal style, with emphasis on the underlying physics. Although the foundations of astrophysics were laid down by 1870, and the edifice was sufficiently built up by 1920, the definitive proof of many of the prescient conjectures made in the 1920s and 1930s came to be established less than ten years ago. This book discusses these recent developments in the context of discussing the nature of the stars, their stability and the source of the energy they radiate.  Reading this book will get young students excited about the presently unfolding revolution in astronomy and the challenges that await them in the world of physics, engineering and technology. General readers will also find the book appealing for its highly accessible narrative of the physics of stars.  “... The reade...

  18. Parametrising Star Formation Histories

    CERN Document Server

    Simha, Vimal; Conroy, Charlie; Dave, Romeel; Fardal, Mark; Katz, Neal; Oppenheimer, Benjamin D

    2014-01-01

    We examine the star formation histories (SFHs) of galaxies in smoothed particle hydrodynamics (SPH) simulations, compare them to parametric models that are commonly used in fitting observed galaxy spectral energy distributions, and examine the efficacy of these parametric models as practical tools for recovering the physical parameters of galaxies. The commonly used tau-model, with SFR ~ exp(-t/tau), provides a poor match to the SFH of our SPH galaxies, with a mismatch between early and late star formation that leads to systematic errors in predicting colours and stellar mass-to-light ratios. A one-parameter lin-exp model, with SFR ~ t*exp(-t/tau), is much more successful on average, but it fails to match the late-time behavior of the bluest, most actively star-forming galaxies and the passive, "red and dead" galaxies. We introduce a 4-parameter model, which transitions from lin-exp to a linear ramp after a transition time, which describes our simulated galaxies very well. We test the ability of these paramet...

  19. The STAR PXL detector

    Science.gov (United States)

    Contin, G.

    2016-12-01

    The PiXeL detector (PXL) of the STAR experiment at RHIC is the first application of the state-of-the-art thin Monolithic Active Pixel Sensors (MAPS) technology in a collider environment. Designed to extend the STAR measurement capabilities in the heavy flavor domain, it took data in Au+Au collisions, p+p and p+Au collisions at 0√sNN=20 GeV at RHIC, during the period 2014-2016. The PXL detector is based on 50 μm-thin MAPS sensors with a pitch of 20.7 μm. Each sensor includes an array of nearly 1 million pixels, read out in rolling shutter mode in 185.6 μs. The 170 mW/cm2 power dissipation allows for air cooling and contributes to reduce the global material budget to 0.4% radiation length on the innermost layer. Experience and lessons learned from construction and operations will be presented in this paper. Detector performance and results from 2014 Au+Au data analysis, demonstrating the STAR capabilities of charm reconstruction, will be shown.

  20. Magnetic fields in star formation: from galaxies to stars

    CERN Document Server

    Price, Daniel J; Dobbs, Clare L

    2008-01-01

    Magnetic fields are important at every scale in the star formation process: from the dynamics of the ISM in galaxies, to the collapse of turbulent molecular clouds to form stars and in the fragmentation of individual star forming cores. The recent development of a robust algorithm for MHD in the Smoothed Particle Hydrodynamics method has enabled us to perform simulations of star formation including magnetic fields at each of these scales. This paper focusses on three questions in particular: What is the effect of magnetic fields on fragmentation in star forming cores? How do magnetic fields affect the collapse of turbulent molecular clouds to form stars? and: What effect do magnetic fields have on the dynamics of the interstellar medium?

  1. Approximate Universal Relations for Neutron Stars and Quark Stars

    CERN Document Server

    Yagi, Kent

    2016-01-01

    Neutron stars and quark stars are ideal laboratories to study fundamental physics at supra nuclear densities and strong gravitational fields. Astrophysical observables, however, depend strongly on the star's internal structure, which is currently unknown due to uncertainties in the equation of state. Universal relations, however, exist among certain stellar observables that do not depend sensitively on the star's internal structure. One such set of relations is between the star's moment of inertia ($I$), its tidal Love number (Love) and its quadrupole moment ($Q$), the so-called I-Love-Q relations. Similar relations hold among the star's multipole moments, which resemble the well-known black hole no-hair theorems. Universal relations break degeneracies among astrophysical observables, leading to a variety of applications: (i) X-ray measurements of the nuclear matter equation of state, (ii) gravitational wave measurements of the intrinsic spin of inspiraling compact objects, and (iii) gravitational and astroph...

  2. Runaway Stars in Supernova Remnants

    Science.gov (United States)

    Pannicke, Anna; Neuhaeuser, Ralph; Dinçel, Baha

    2016-07-01

    Half of all stars and in particular 70 % of the massive stars are a part of a multiple system. A possible development for the system after the core collapse supernova (SN) of the more massive component is as follows: The binary is disrupted by the SN. The formed neutron star is ejected by the SN kick whereas the companion star either remains within the system and is gravitationally bounded to the neutron star, or is ejected with a spatial velocity comparable to its former orbital velocity (up to 500 km/s). Such stars with a large peculiar space velocity are called runaway stars. We present our observational results of the supernova remnants (SNRs) G184.6-5.8, G74.0-8.5 and G119.5+10.2. The focus of this project lies on the detection of low mass runaway stars. We analyze the spectra of a number of candidates and discuss their possibility of being the former companions of the SN progenitor stars. The spectra were obtained with INT in Tenerife, Calar Alto Astronomical Observatory and the University Observatory Jena. Also we investigate the field stars in the neighborhood of the SNRs G74.0-8.5 and G119.5+10.2 and calculate more precise distances for these SNRs.

  3. The effect of magnetic fields on star cluster formation

    CERN Document Server

    Price, Daniel

    2008-01-01

    We examine the effect of magnetic fields on star cluster formation by performing simulations following the self-gravitating collapse of a turbulent molecular cloud to form stars in ideal MHD. The collapse of the cloud is computed for global mass-to-flux ratios of infinity, 20, 10, 5 and 3, that is using both weak and strong magnetic fields. Whilst even at very low strengths the magnetic field is able to significantly influence the star formation process, for magnetic fields with plasma beta < 1 the results are substantially different to the hydrodynamic case. In these cases we find large-scale magnetically-supported voids imprinted in the cloud structure; anisotropic turbulent motions and column density structure aligned with the magnetic field lines, both of which have recently been observed in the Taurus molecular cloud. We also find strongly suppressed accretion in the magnetised runs, leading to up to a 75% reduction in the amount of mass converted into stars over the course of the calculations and a m...

  4. The coolest 'stars' are free-floating planets

    CERN Document Server

    Joergens, V; Liu, Y; Bayo, A; Wolf, S

    2014-01-01

    We show that the coolest known object that is probably formed in a star-like mode is a free-floating planet. We discovered recently that the free-floating planetary mass object OTS,44 (M9.5, ~12 Jupiter masses, age ~2 Myr) has significant accretion and a substantial disk. This demonstrates that the processes that characterize the canonical star-like mode of formation apply to isolated objects down to a few Jupiter masses. We detected in VLT/SINFONI spectra that OTS44 has strong, broad, and variable Paschen beta emission. This is the first evidence for active accretion of a free-floating planet. The object allows us to study accretion and disk physics at the extreme and can be seen as free-floating analog of accreting planets that orbit stars. Our analysis of OTS44 shows that the mass-accretion rate decreases continuously from stars of several solar masses down to free-floating planets. We determined, furthermore, the disk mass (10 Earth masses) and further disk properties of OTS44 through modeling its SED inc...

  5. Neutron Beta Decay Studies with Nab

    CERN Document Server

    Baeßler, S; Alonzi, L P; Balascuta, S; Barrón-Palos, L; Bowman, J D; Bychkov, M A; Byrne, J; Calarco, J R; Chupp, T; Vianciolo, T V; Crawford, C; Frlež, E; Gericke, M T; Glück, F; Greene, G L; Grzywacz, R K; Gudkov, V; Harrison, D; Hersman, F W; Ito, T; Makela, M; Martin, J; McGaughey, P L; McGovern, S; Page, S; Penttilä, S I; Počanić, D; Rykaczewski, K P; Salas-Bacci, A; Tompkins, Z; Wagner, D; Wilburn, W S; Young, A R

    2012-01-01

    Precision measurements in neutron beta decay serve to determine the coupling constants of beta decay and allow for several stringent tests of the standard model. This paper discusses the design and the expected performance of the Nab spectrometer.

  6. First stars X. The nature of three unevolved carbon-enhanced metal-poor stars

    DEFF Research Database (Denmark)

    Sivarani, T.; Beers, T.C.; Bonifacio, P.

    2006-01-01

    Stars: abundances, stars: population II, Galaxy: abundances, stars: AGB and post-AGB Udgivelsesdato: Nov.......Stars: abundances, stars: population II, Galaxy: abundances, stars: AGB and post-AGB Udgivelsesdato: Nov....

  7. The beta-decay of Al-22

    NARCIS (Netherlands)

    Achouri, NL; Santos, FDO; Lewitowicz, M; Blank, B; Aysto, J; Canchel, G; Czajkowski, S; Dendooven, P; Emsallem, A; Giovinazzo, J; Guillet, N; Jokinen, A; Larid, AM; Longour, C; Perajarvi, K; Smirnova, N; Stanoiu, M

    2006-01-01

    In an experiment performed at the LISE3 facility of GANIL, we studied the decay of Al-22 produced by the fragmentation of a Ar-36 primary beam. A beta-decay half-life of T-1/2 = 91.1 +/- 0.5ms was measured. The beta-delayed one- and two-proton emission as well as beta-alpha and beta-delayed gamma-de

  8. Traumatic Brain Injury, Microglia, and Beta Amyloid

    OpenAIRE

    Mannix, Rebekah C.; Whalen, Michael J

    2012-01-01

    Recently, there has been growing interest in the association between traumatic brain injury (TBI) and Alzheimer's Disease (AD). TBI and AD share many pathologic features including chronic inflammation and the accumulation of beta amyloid (A\\(\\beta\\)). Data from both AD and TBI studies suggest that microglia play a central role in A\\(\\beta\\) accumulation after TBI. This paper focuses on the current research on the role of microglia response to A\\(\\beta\\) after TBI.

  9. Star centroiding error compensation for intensified star sensors.

    Science.gov (United States)

    Jiang, Jie; Xiong, Kun; Yu, Wenbo; Yan, Jinyun; Zhang, Guangjun

    2016-12-26

    A star sensor provides high-precision attitude information by capturing a stellar image; however, the traditional star sensor has poor dynamic performance, which is attributed to its low sensitivity. Regarding the intensified star sensor, the image intensifier is utilized to improve the sensitivity, thereby further improving the dynamic performance of the star sensor. However, the introduction of image intensifier results in star centroiding accuracy decrease, further influencing the attitude measurement precision of the star sensor. A star centroiding error compensation method for intensified star sensors is proposed in this paper to reduce the influences. First, the imaging model of the intensified detector, which includes the deformation parameter of the optical fiber panel, is established based on the orthographic projection through the analysis of errors introduced by the image intensifier. Thereafter, the position errors at the target points based on the model are obtained by using the Levenberg-Marquardt (LM) optimization method. Last, the nearest trigonometric interpolation method is presented to compensate for the arbitrary centroiding error of the image plane. Laboratory calibration result and night sky experiment result show that the compensation method effectively eliminates the error introduced by the image intensifier, thus remarkably improving the precision of the intensified star sensors.

  10. Dust Emissivity in the Star-Forming Filament OMC 2/3

    CERN Document Server

    Sadavoy, S I; Schnee, S; Mason, B; Di Francesco, J; Friesen, R

    2016-01-01

    We present new measurements of the dust emissivity index, beta, for the high-mass, star-forming OMC 2/3 filament. We combine 160-500 um data from Herschel with long-wavelength observations at 2 mm and fit the spectral energy distributions across a ~ 2 pc long, continuous section of OMC 2/3 at 15000 AU (0.08 pc) resolution. With these data, we measure beta and reconstruct simultaneously the filtered-out large-scale emission at 2 mm. We implement both variable and fixed values of beta, finding that beta = 1.7 - 1.8 provides the best fit across most of OMC 2/3. These beta values are consistent with a similar analysis carried out with filtered Herschel data. Thus, we show that beta values derived from spatial filtered emission maps agree well with those values from unfiltered data at the same resolution. Our results contradict the very low beta values (~ 0.9) previously measured in OMC 2/3 between 1.2 mm and 3.3 mm data, which we attribute to elevated fluxes in the 3.3 mm observations. Therefore, we find no evide...

  11. THE ALPHA/BETA-HYDROLASE FOLD

    NARCIS (Netherlands)

    OLLIS, DL; CHEAH, E; CYGLER, M; FROLOW, F; FRANKEN, SM; HAREL, M; REMINGTON, SJ; SILMAN, [No Value; SCHRAG, J; SUSSMAN, JL; VERSCHUEREN, KHG; GOLDMAN, A

    1992-01-01

    We have identified a new protein fold-the alpha/beta-hydrolase fold-that is common to several hydrolytic enzymes of widely differing phylogenetic origin and catalytic function. The core of each enzyme is similar: an alpha/beta-sheet, not barrel, of eight beta-sheets connected by alpha-helices. These

  12. Beta-lactamases in Enterobacteriaceae in broilers

    NARCIS (Netherlands)

    Dierikx, C.M.

    2013-01-01

    Resistance to cephalosprins due to the production of extended spectrum beta-lactamases (ESBLs) or plasmid mediated AmpC beta-lactamases is increasingly found in infections in humans outside the hospital. The genes encoding for these beta-lactamases are located on mobile DNA (plasmids), which can be

  13. Higher-Order Beta Matching with Solutions in Long Beta-Eta Normal Form

    DEFF Research Database (Denmark)

    Støvring, Kristian

    2006-01-01

    up to beta-eta equivalence is a long-standing open problem.We show that higher-order matching up to beta-eta equivalence is decidable if and only if a restricted form of higher-order matching up to beta equivalence is decidable: the restriction is that solutions must be in long beta-eta normal form....

  14. Spectroscopic atlas of Halpha and Hbeta in a sample of northern Be stars

    CERN Document Server

    Catanzaro, G

    2013-01-01

    We present Balmer lines spectroscopy for a sample of 48 Be stars. For most of them, H$\\alpha$ and H$\\beta$ have been observed more than two times, in a total period spanning almost two years between 2008 and 2009. Spectral synthesis of the H$\\alpha$ profile was performed following two steps: photospheric contribution was computed by using Kurucz's code ATLAS9 and SYNTHE, and disk emission was derived by the approach of Hummel & Vrancken (2000, A&A, 302, 751). For 26 out of 48 stars, a modeling of the total H$\\alpha$ emission has been attempted. By this modeling we derived an estimation of the disk radius, as well as the inclination angle between the rotational axis with line of sight and the base density at the stellar equator. For the stars observed more than once, we also discuss the variability of H$\\alpha$ and H$\\beta$ for what concerns both the equivalent width and the spectral profile. We found 16 stars with variable equivalent width and 7 stars with clear signs of profile variation. We derive e...

  15. Flattest Star Ever Seen

    Science.gov (United States)

    2003-06-01

    VLT Interferometer Measurements of Achernar Challenge Stellar Theory Summary To a first approximation, planets and stars are round. Think of the Earth we live on. Think of the Sun, the nearest star, and how it looks in the sky. But if you think more about it, you realize that this is not completely true. Due to its daily rotation, the solid Earth is slightly flattened ("oblate") - its equatorial radius is some 21 km (0.3%) larger than the polar one. Stars are enormous gaseous spheres and some of them are known to rotate quite fast, much faster than the Earth. This would obviously cause such stars to become flattened. But how flat? Recent observations with the VLT Interferometer (VLTI) at the ESO Paranal Observatory have allowed a group of astronomers [1] to obtain by far the most detailed view of the general shape of a fast-spinning hot star, Achernar (Alpha Eridani) , the brightest in the southern constellation Eridanus (The River). They find that Achernar is much flatter than expected - its equatorial radius is more than 50% larger than the polar one! In other words, this star is shaped very much like the well-known spinning-top toy, so popular among young children. The high degree of flattening measured for Achernar - a first in observational astrophysics - now poses an unprecedented challenge for theoretical astrophysics . The effect cannot be reproduced by common models of stellar interiors unless certain phenomena are incorporated, e.g. meridional circulation on the surface ("north-south streams") and non-uniform rotation at different depths inside the star. As this example shows, interferometric techniques will ultimately provide very detailed information about the shapes, surface conditions and interior structure of stars . PR Photo 15a/03 : The VLT Interferometer configuration for the Achernar measurements PR Photo 15b/03 : Achernar's "profile" , as measured by the VLTI. PR Photo 15c/03 : Models of Achernar's spatial shape. VLTI observations of Achernar

  16. First stars evolution and nucleosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Bahena, D. [Institute of Astronomy of the Academy of Sciences, Bocni II 1401, 14131 Praha 4, (Czech Republic); Klapp, J. [ININ, 52750 La Marquesa, Estado de Mexico (Mexico); Dehnen, H. [Fachbereich Physik, Universitat Konstanz, 78457 Konstanz (Germany)]. e-mail: bahen@hotmail.com

    2007-12-15

    The first stars in the universe were massive and luminous with typical masses M {>=} 100M. Metal-free stars have unique physical characteristics and exhibit high effective temperatures and small radii. These so called Population III stars were responsible for the initial enrichment of the intergalactic medium with heavy elements. In this work, we study the structure, evolution and nucleosynthesis of 100, 200, 250 and 300M galactic and pregalactic Population III mass losing stars with metallicities Z 10{sup -6} and Z = 10{sup -9}, during the hydrogen and helium burning phases. Using a stellar evolution code, a system of 10 structure and evolution equations together with boundary conditions, and a set of 30 nuclear reactions, are solved simultaneously, obtaining the star's structure, evolution, isotopic abundances and their ratios. Motivated by recent stability analysis, almost all very massive star (VMS) calculations during the past few years have been performed with no mass loss. However, it has recently been claimed that VMS should have strong mass loss. We present in this work new VMS calculations that includes mass loss. The main difference between zero-metal and metal-enriched stars lies in the nuclear energy generation mechanism. For the first stars, nuclear burning proceeds in a non-standard way. Since Population III stars can reach high central temperatures, this leads to the first synthesis of primary carbon through the 3 {alpha} reaction activating the CNO-cycles. Zero-metal stars produce light elements, such as He, C, N and O. Thus, very massive pregalactic Population III stars experienced self-production of C, either at the zero-age main sequence or in later phases of central hydrogen burning. In advanced evolutionary phases, these stars contribute to the chemical enrichment of the intergalactic medium through supernova explosions. (Author)

  17. Quantitative spectroscopy of hot stars

    Science.gov (United States)

    Kudritzki, R. P.; Hummer, D. G.

    1990-01-01

    A review on the quantitative spectroscopy (QS) of hot stars is presented, with particular attention given to the study of photospheres, optically thin winds, unified model atmospheres, and stars with optically thick winds. It is concluded that the results presented here demonstrate the reliability of Qs as a unique source of accurate values of the global parameters (effective temperature, surface gravity, and elemental abundances) of hot stars.

  18. Properties of Rotating Neutron Star

    Directory of Open Access Journals (Sweden)

    Shailesh K. Singh

    2015-08-01

    Full Text Available Using the nuclear equation of states for a large variety of relativistic and non-relativistic force parameters, we calculate the static and rotating masses and radii of neutron stars. From these equation of states, we evaluate the properties of rotating neutron stars, such as rotational frequencies, moment of inertia, quadrupole deformation parameter, rotational ellipticity and gravitational wave strain amplitude. The estimated gravitational wave strain amplitude of the star is found to be~sim 10-23.

  19. Massive star clusters in galaxies

    CERN Document Server

    Harris, William E

    2009-01-01

    The ensemble of all star clusters in a galaxy constitutes its star cluster system. In this review, the focus of the discussion is on the ability of star clusters, particularly the systems of old massive globular clusters (GCSs), to mark the early evolutionary history of galaxies. I review current themes and key findings in GCS research, and highlight some of the outstanding questions that are emerging from recent work.

  20. The Star Formation History of RCW 36

    NARCIS (Netherlands)

    L. Ellerbroek; L. Kaper; A. Bik; K.M. Maaskant; L. Podio

    2014-01-01

    Recent studies of massive-star forming regions indicate that they can contain multiple generations of young stars. These observations suggest that star formation in these regions is sequential and/or triggered by a previous generation of (massive) stars. Here we present new observations of the star

  1. Lithium Abundances of Extremely Metal-Poor Turn-off Stars

    CERN Document Server

    Aoki, Wako; Beers, Timothy C; Christlieb, Norbert; Inoue, Susumu; Perez, Ana E Garcia; Norris, John E; Carollo, Daniela

    2009-01-01

    We have determined Li abundances for eleven metal-poor turn-off stars, among which eight have [Fe/H]<-3, based on LTE analyses of high-resolution spectra obtained with the HDS on the Subaru telescope. The Li abundances for four of these eight stars are determined for the first time by this study. Effective temperatures are determined by a profile analysis of H-alpha and H-beta. While seven stars have Li abundances as high as the Spite Plateau value, the remaining four objects with [Fe/H] <-3 have A(Li)=log(Li/H)+12 ~< 2.0, confirming the existence of extremely metal-poor turn-off stars having low Li abundances, as reported by previous work. The average of the Li abundances for stars with [Fe/H]<-3 is lower by 0.2 dex than that of the stars with higher metallicity. No clear constraint on the metallicity dependence or scatter of the Li abundances is derived from our measurements for the stars with [Fe/H]<-3. Correlations of the Li abundance with effective temperatures, with abundances of Na, Mg a...

  2. Chemical composition of intermediate mass stars members of the M6 (NGC 6405) open cluster

    CERN Document Server

    Kılıçoğlu, Tolgahan; Richer, Jacques; Fossati, Luca; Albayrak, Berahitdin

    2015-01-01

    We present here the first abundance analysis of 44 late B, A and F-type members of the young open cluster M6 (NGC 6405, age about 75 Myrs). Spectra, covering the 4500 to 5800 \\AA{} wavelength range, were obtained using the FLAMES/GIRAFFE spectrograph attached to the ESO Very Large Telescopes (VLT). We determined the atmospheric parameters using calibrations of the Geneva photometry and by adjusting the $H_{\\beta}$ profiles to synthetic ones. The abundances of up to 20 chemical elements, were derived for 19 late B, 16 A and 9 F stars by iteratively adjusting synthetic spectra to the observations. We also derived a mean cluster metallicity of $\\mathrm{[Fe/H]=0.07\\pm0.03}$ dex from the iron abundances of the F-type stars. We find that, for most chemical elements, the normal late B and A-type stars exhibit larger star-to-star abundance variations than the F-type stars do probably because of the faster rotation of the B and A stars. The abundances of C, O, Mg, Si and Sc appear to be anticorrelated to that of Fe, w...

  3. A Low-Resolution Spectroscopic Exploration of Puzzling OGLE Variable Stars

    CERN Document Server

    Pietrukowicz, P; Angeloni, R; di Mille, F; Soszynski, I; Udalski, A; Germana, C

    2015-01-01

    We present the results of a spectroscopic follow-up of various puzzling variable objects detected in the OGLE-III Galactic disk and bulge fields. The sample includes mainly short-period multi-mode pulsating stars that could not have been unambiguously classified as either delta Sct or beta Cep type stars based on photometric data only, also stars with irregular fluctuations mimicking cataclysmic variables and stars with dusty shells, and periodic variables displaying brightenings in their light curves that last for more than half of the period. The obtained low-resolution spectra show that all observed short-period pulsators are of delta Sct type, the stars with irregular fluctuations are young stellar objects, and the objects with regular brightenings are A type stars or very likely Ap stars with strong magnetic field responsible for the presence of bright caps around magnetic poles on their surface. We also took spectra of objects designated OGLE-GD-DSCT-0058 and OGLE-GD-CEP-0013. An estimated effective tem...

  4. Apple Valley Double Star Workshop

    Science.gov (United States)

    Brewer, Mark

    2015-05-01

    The High Desert Astronomical Society hosts an annual double star workshop, where participants measure the position angles and separations of double stars. Following the New Generation Science Standards (NGSS), adopted by the California State Board of Education, participants are assigned to teams where they learn the process of telescope set-up and operation, the gathering of data, and the reduction of the data. Team results are compared to the latest epoch listed in the Washington Double Star Catalog (WDS) and papers are written for publication in the Journal of Double Star Observations (JDSO). Each team presents a PowerPoint presentation to their peers about actual hands-on astronomical research.

  5. Stellar populations in star clusters

    Science.gov (United States)

    Li, Cheng-Yuan; de Grijs, Richard; Deng, Li-Cai

    2016-12-01

    Stellar populations contain the most important information about star cluster formation and evolution. Until several decades ago, star clusters were believed to be ideal laboratories for studies of simple stellar populations (SSPs). However, discoveries of multiple stellar populations in Galactic globular clusters have expanded our view on stellar populations in star clusters. They have simultaneously generated a number of controversies, particularly as to whether young star clusters may have the same origin as old globular clusters. In addition, extensive studies have revealed that the SSP scenario does not seem to hold for some intermediate-age and young star clusters either, thus making the origin of multiple stellar populations in star clusters even more complicated. Stellar population anomalies in numerous star clusters are well-documented, implying that the notion of star clusters as true SSPs faces serious challenges. In this review, we focus on stellar populations in massive clusters with different ages. We present the history and progress of research in this active field, as well as some of the most recent improvements, including observational results and scenarios that have been proposed to explain the observations. Although our current ability to determine the origin of multiple stellar populations in star clusters is unsatisfactory, we propose a number of promising projects that may contribute to a significantly improved understanding of this subject.

  6. Surface abundances of ON stars

    CERN Document Server

    Martins, F; Palacios, A; Howarth, I; Georgy, C; Walborn, N R; Bouret, J -C; Barba, R

    2015-01-01

    Massive stars burn hydrogen through the CNO cycle during most of their evolution. When mixing is efficient, or when mass transfer in binary systems happens, chemically processed material is observed at the surface of O and B stars. ON stars show stronger lines of nitrogen than morphologically normal counterparts. Whether this corresponds to the presence of material processed through the CNO cycle or not is not known. Our goal is to answer this question. We perform a spectroscopic analysis of a sample of ON stars with atmosphere models. We determine the fundamental parameters as well as the He, C, N, and O surface abundances. We also measure the projected rotational velocities. We compare the properties of the ON stars to those of normal O stars. We show that ON stars are usually helium-rich. Their CNO surface abundances are fully consistent with predictions of nucleosynthesis. ON stars are more chemically evolved and rotate - on average - faster than normal O stars. Evolutionary models including rotation cann...

  7. beta (+)-Thalassaemia in the Po river delta region (northern Italy): genotype and beta globin synthesis.

    OpenAIRE

    del Senno, L; Pirastu, M; Barbieri, R.; De Bernardi, F.; Buzzoni, D; Marchetti, G.; Perrotta, C; Vullo, C; Kan, Y W; Conconi, F

    1985-01-01

    Six beta(+)-thalassaemic patients from the Po river delta region have been studied. Using synthetic oligonucleotides as specific hybridisation probes, the beta(+) IVS I mutation (G----A at position 108) was demonstrated. This lesion and the enzyme polymorphism pattern in the subjects examined are the same as have been described for other Mediterranean beta(+)-thalassaemias. Antenatal diagnosis through DNA analysis of beta(+)-thalassaemia is therefore possible. The production of beta globin in...

  8. Structure of hybrid protoneutron stars within the Nambu--Jona-Lasinio model

    CERN Document Server

    Burgio, G F

    2007-01-01

    We investigate the structure of protoneutron stars (PNS) formed by hadronic and quark matter in $\\beta$-equilibrium described by appropriate equations of state (EOS). For the hadronic matter, we use a finite temperature EOS based on the Brueckner-Bethe-Goldstone many-body theory, with realistic two- and three-body forces. For the quark sector, we employ the Nambu--Jona-Lasinio model. We find that the maximum allowed masses are comprised in a narrow range around 1.8 solar masses, with a slight dependence on the temperature. Metastable hybrid protoneutron stars are not found.

  9. Stars with Extended Atmospheres

    Science.gov (United States)

    Sterken, C.

    2002-12-01

    This Workshop consisted of a full-day meeting of the Working Group "Sterren met Uitgebreide Atmosferen" (SUA, Working Group Stars with Extended Atmospheres), a discussion group founded in 1979 by Kees de Jager, Karel van der Hucht and Pik Sin The. This loose association of astronomers and astronomy students working in the Dutch-speaking part of the Low Countries (The Netherlands and Flanders) organised at regular intervals one-day meetings at the Universities of Utrecht, Leiden, Amsterdam and Brussels. These meetings consisted of the presentation of scientific results by junior as well as senior members of the group, and by discussions between the participants. As such, the SUA meetings became a forum for the exchange of ideas, and for asking questions and advice in an informal atmosphere. Kees de Jager has been chairman of the WG SUA from the beginning in 1979 till today, as the leading source of inspiration. At the occasion of Prof. Kees de Jager's 80th birthday, we decided to collect the presented talks in written form as a Festschrift in honour of this well-respected and much beloved scientist, teacher and friend. The first three papers deal with the personality of Kees de Jager, more specifically with his role as a supervisor and mentor of young researchers and as a catalyst in the research work of his colleagues. And also about his remarkable role in the establishment of astronomy education and research at the University of Brussels. The next presentation is a very detailed review of solar research, a field in which Cees was prominently active for many years. Then follow several papers dealing with stars about which Kees is a true expert: massive stars and extended atmospheres.

  10. Stars and Star Clusters: A Look at Intermediate-Mass Star-Forming Regions

    Science.gov (United States)

    Lundquist, Michael J.; Kobulnicky, Henry A.; Lau, Ryan M.

    2017-01-01

    Star-forming regions hosting intermediate-mass stars straddle the boundary separating the the low- and high-mass regimes. These intermediate-mass star-forming regions can be used to probe this transition from low- to high-mass star formation. Our team has assembled an all-sky catalog of 616 candidate intermediate-mass star forming regions (IMSFRs) selected by IRAS colors and refined by visual inspection of WISE imagery. We present here two outer-Galaxy star-forming regions, IRAS22451+6154 and IRAS23448+6010, that despite having similar IRAS colors and mid-infrared morphologies, have vastly different stellar content. We combine Gemini and IRTF NIR spectroscopy with WIYN and SOFIA imaging for a thorough look at the stellar content of these two regions.

  11. Specific Triazine Herbicides Induce Amyloid-beta(42) Production

    NARCIS (Netherlands)

    Portelius, Erik; Durieu, Emilie; Bodin, Marion; Cam, Morgane; Pannee, Josef; Leuxe, Charlotte; Mabondzo, Aloise; Oumata, Nassima; Galons, Herve; Lee, Jung Yeol; Chang, Young-Tae; Stuber, Kathrin; Koch, Philipp; Fontaine, Gaelle; Potier, Marie-Claude; Manousopoulou, Antigoni; Garbis, Spiros D.; Covaci, Adrian; Van Dam, Debby; De Deyn, Peter; Karg, Frank; Flajolet, Marc; Omori, Chiori; Hata, Saori; Suzuki, Toshiharu; Blennow, Kaj; Zetterberg, Henrik; Meijer, Laurent

    2016-01-01

    Proteolytic cleavage of the amyloid-beta protein precursor (A beta PP) ecretases leads to extracellular release of amyloid-beta (A beta) peptides. Increased production of A beta(42) over A beta(40) and aggregation into oligomers and plaques constitute an Alzheimer's disease (AD) hallmark. Identifyin

  12. LEGO STAR WARS

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    去年有一款游戏以惊人的销量。让人们印象深刻,它就是《乐高星球大战》,经过一番传言过后,LucasArts终于发表了《乐高星球大战》的续作《乐高星球大战2:首部曲》(Lego Star Wars Ⅱ:The Original Trilog),而且登陆的平台还包括了任天堂的DS和GBA主机。

  13. The guide star catalog

    Science.gov (United States)

    Lasker, Barry M.; Jenkner, Helmut; Russell, Jane L.

    1987-01-01

    Part 1 of the catalog presents an astronomical overview of the Guide Star Catalog, together with its history, the properties of its current implementation, and the prospects for enhancement. Part 2 presents the algorithms used in photometric and astrometric calibration of the catalog, as well as the analyses of the related errors. Part 3 presents the current structure and content, as well as future enhancements in this area. An overview of the forthcoming publications is given, both with regard to scientific papers and electronic media.

  14. On Magnetized Neutron Stars

    CERN Document Server

    Lopes, Luiz L

    2014-01-01

    In this work we review the formalism normally used in the literature about the effects of density-dependent magnetic fields on the properties of neutron stars, expose some ambiguities that arise and propose a way to solve the related problem. Our approach uses a different prescription for the calculation of the pressure based on the chaotic field formalism for the stress tensor and also a different way of introducing a variable magnetic field, which depends on the energy density rather than on the baryonic density.

  15. Stars of heaven

    CERN Document Server

    Pickover, Clifford A

    2004-01-01

    Do a little armchair space travel, rub elbows with alien life forms, and stretch your mind to the furthest corners of our uncharted universe. With this astonishing guidebook, you don't have to be an astronomer to explore the mysteries of stars and their profound meaning for human existence. Clifford A. Pickover tackles a range of topics from stellar evolution to the fundamental reasons why the universe permits life to flourish. He alternates sections that explain the mysteries of the cosmos with sections that dramatize mind-expanding concepts through a fictional dialog between futuristic human

  16. SIRTF autonomous star tracker

    Science.gov (United States)

    van Bezooijen, Roelof W. H.

    2003-03-01

    Two redundant AST-301 autonomous star trackers (AST) serve as the primary attitude sensors for JPL's space infrared telescope facility (SIRTF). These units, which employ a 1553B interface to output their attitude quaternions and uncertainty at a 2 Hz rate, provide a 1 σaccuracy of better than 0.18, 0.18, and 5.1 arcsec about their X, Y, and Z axes, respectively. This is a factor 5.5 better than the accuracy of the flight-proven AST-201 from which the trackers were derived. To obtain this improvement, the field of view (FOV) was reduced to 5 by 5 degrees, the accurate Tycho-1 and ACT catalogs were used for selecting the 71,830 guide stars, star image centroiding was improved to better than 1/50th of a pixel, and optimal attitude estimation was implemented. In addition, the apparent direction to each guide star in the FOV is compensated for proper motion, parallax, velocity aberration, and optical distortion. The AST-301 employs autonomous time-delayed integration (TDI) to achieve image motion compensation (IMC) about its X axis that prevents accuracy degradation, even at rates of 2.1 deg/s, making it actually suitable for use on spinning spacecraft. About the Y axis, a software function called "image motion accommodation" (IMA) processes smeared images to maximize the signal to noise ratio of the resulting synthetic images, which enables robust and accurate tracking at rates tested up to 0.42 deg/s. The AST-301 is capable of acquiring its attitude anywhere in the sky in less than 3 seconds with a 99.98% probability of success, without requiring any a priori attitude knowledge. Following a description of the 7.1 kg AST-301, its operation and IMA, the methodology for translating the night sky test data into performance numbers is presented, while, in addition, the results of tests used to measure alignment stability over temperature are included.

  17. Dielectron Measurements in STAR

    Directory of Open Access Journals (Sweden)

    Geurts Frank

    2012-11-01

    Full Text Available Ultrarelativistic heavy-ion collisions provide a unique environment to study the properties of strongly interacting matter. Dileptons, which are not affected by the strong interactions, are an ideal penetrating probe. We present the dielectron results for p+p and Au+Au collisions at √sNN = 200 GeV, as measured by the STAR experiment. We discuss the prospects of dilepton measurements with the near-future detector upgrades, and the recent lower beam energy Au+Au measurements.

  18. Hadronic Resonances from STAR

    Directory of Open Access Journals (Sweden)

    Wada Masayuki

    2012-11-01

    Full Text Available The results of resonance particle productions (ρ0, ω, K*, ϕ, Σ*, and Λ* measured by the STAR collaboration at RHIC from various colliding systems and energies are presented. Measured mass, width, 〈pT〉, and yield of those resonances are reviewed. No significant mass shifts or width broadening beyond the experiment uncertainties are observed. New measurements of ϕ and ω from leptonic decay channels are presented. The yields from leptonic decay channels are compared with the measurements from hadronic decay channels and the two results are consistent with each other.

  19. Probing neutron star physics using accreting neutron stars

    Directory of Open Access Journals (Sweden)

    Patruno A.

    2010-10-01

    Full Text Available We give an obervational overview of the accreting neutron stars systems as probes of neutron star physics. In particular we focus on the results obtained from the periodic timing of accreting millisecond X-ray pulsars in outburst and from the measurement of X-ray spectra of accreting neutron stars during quiescence. In the first part of this overview we show that the X-ray pulses are contaminated by a large amount of noise of uncertain origin, and that all these neutron stars do not show evidence of spin variations during the outburst. We present also some recent developments on the presence of intermittency in three accreting millisecond X-ray pulsars and investigate the reason why only a small number of accreting neutron stars show X-ray pulsations and why none of these pulsars shows sub-millisecond spin periods. In the second part of the overview we introduce the observational technique that allows the study of neutron star cooling in accreting systems as probes of neutron star internal composition and equation of state. We explain the phenomenon of the deep crustal heating and present some recent developments on several quasi persistent X-ray sources where a cooling neutron star has been observed.

  20. Star-forming galaxy models: Blending star formation into TREESPH

    Science.gov (United States)

    Mihos, J. Christopher; Hernquist, Lars

    1994-01-01

    We have incorporated star-formation algorithms into a hybrid N-body/smoothed particle hydrodynamics code (TREESPH) in order to describe the star forming properties of disk galaxies over timescales of a few billion years. The models employ a Schmidt law of index n approximately 1.5 to calculate star-formation rates, and explicitly include the energy and metallicity feedback into the Interstellar Medium (ISM). Modeling the newly formed stellar population is achieved through the use of hybrid SPH/young star particles which gradually convert from gaseous to collisionless particles, avoiding the computational difficulties involved in creating new particles. The models are shown to reproduce well the star-forming properties of disk galaxies, such as the morphology, rate of star formation, and evolution of the global star-formation rate and disk gas content. As an example of the technique, we model an encounter between a disk galaxy and a small companion which gives rise to a ring galaxy reminiscent of the Cartwheel (AM 0035-35). The primary galaxy in this encounter experiences two phases of star forming activity: an initial period during the expansion of the ring, and a delayed phase as shocked material in the ring falls back into the central regions.

  1. Triggered Star Formation Surrounding Wolf-Rayet Star HD 211853

    Science.gov (United States)

    Liu, Tie; Wu, Yuefang; Zhang, Huawei; Qin, Sheng-Li

    2012-05-01

    The environment surrounding Wolf-Rayet (W-R) star HD 211853 is studied in molecular, infrared, as well as radio, and H I emission. The molecular ring consists of well-separated cores, which have a volume density of 103 cm-3 and kinematic temperature ~20 K. Most of the cores are under gravitational collapse due to external pressure from the surrounding ionized gas. From the spectral energy distribution modeling toward the young stellar objects, the sequential star formation is revealed on a large scale in space spreading from the W-R star to the molecular ring. A small-scale sequential star formation is revealed toward core "A," which harbors a very young star cluster. Triggered star formations are thus suggested. The presence of the photodissociation region, the fragmentation of the molecular ring, the collapse of the cores, and the large-scale sequential star formation indicate that the "collect and collapse" process functions in this region. The star-forming activities in core "A" seem to be affected by the "radiation-driven implosion" process.

  2. Triggered star formation surrounding Wolf-Rayet star HD 211853

    CERN Document Server

    Liu, Tie; Zhang, Huawei; Qin, Sheng-Li

    2012-01-01

    The environment surrounding Wolf-Rayet star HD 211853 is studied in molecular emission, infrared emission, as well as radio and HI emission. The molecular ring consists of well-separated cores, which have a volume density of 10$^{3}$ cm$^{-3}$ and kinematic temperature $\\sim$20 K. Most of the cores are under gravitational collapse due to external pressure from the surrounding ionized gas. From SED modeling towards the young stellar objects (YSOs), sequential star formation is revealed on a large scale in space spreading from the Wolf-Rayet star to the molecular ring. A small scale sequential star formation is revealed towards core A, which harbors a very young star cluster. Triggered star formations is thus suggested. The presence of PDR, the fragmentation of the molecular ring, the collapse of the cores, the large scale sequential star formation indicate the "Collect and Collapse" process functions in this region. The star forming activities in core A seem to be affected by the "Radiation-Driven Implosion" (...

  3. TRIGGERED STAR FORMATION SURROUNDING WOLF-RAYET STAR HD 211853

    Energy Technology Data Exchange (ETDEWEB)

    Liu Tie; Wu Yuefang; Zhang Huawei [Department of Astronomy, Peking University, 100871 Beijing (China); Qin Shengli, E-mail: liutiepku@gmail.com [I. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Str. 77, 50937 Koeln (Germany)

    2012-05-20

    The environment surrounding Wolf-Rayet (W-R) star HD 211853 is studied in molecular, infrared, as well as radio, and H I emission. The molecular ring consists of well-separated cores, which have a volume density of 10{sup 3} cm{sup -3} and kinematic temperature {approx}20 K. Most of the cores are under gravitational collapse due to external pressure from the surrounding ionized gas. From the spectral energy distribution modeling toward the young stellar objects, the sequential star formation is revealed on a large scale in space spreading from the W-R star to the molecular ring. A small-scale sequential star formation is revealed toward core 'A', which harbors a very young star cluster. Triggered star formations are thus suggested. The presence of the photodissociation region, the fragmentation of the molecular ring, the collapse of the cores, and the large-scale sequential star formation indicate that the 'collect and collapse' process functions in this region. The star-forming activities in core 'A' seem to be affected by the 'radiation-driven implosion' process.

  4. Future double beta decay experiments

    Energy Technology Data Exchange (ETDEWEB)

    Piquemal, F. [Laboratoire Souterrain de Modane, Modane (France); Centre d' Etudes Nucleaire, Bordeaux-Gradignan (France)

    2013-02-15

    The search of neutrinoless double beta decay is very challenging because of the expected half-life of the process and the backgrounds from the natural radioactivity. Many projects exist to try to reach a sensitivity of ∼50 meV on the effective neutrino mass corresponding to a mass of isotopes of ∼100 kg. In this article some of the futur projects are presented.

  5. Myokardinfarkt und Beta-Blocker

    Directory of Open Access Journals (Sweden)

    Stühlinger H-G

    2003-01-01

    Full Text Available Im Rahmen eines akuten koronaren Syndroms (akuter Herzinfarkt, Angina pectoris kommt es, aufgrund eines Ungleichgewichtes zwischen Angebot und Bedarf, zu einem akuten Mangel an Sauerstoff im Herzmuskel. Ursache ist eine reduzierte Sauerstoffzufuhr durch verengte bzw. verschlossene Gefäße. Bis zur Behebung der Ursache vergehen oft mehrere Stunden. In dieser Phase muß - durch Verminderung des Sauerstoffbedarfs im Herzmuskel - eine Verlangsamung der Nekroseentwicklung erreicht werden. Das Ausmaß der Nekrose wird reduziert, somit die für die Langzeitprognose wichtige Linksventrikelfunktion verbessert. Eine Verminderung des Sauerstoffbedarfs erreicht man durch kontrollierte Frequenzsenkung mittels intravenöser Beta-Blockade. In optimaler Weise wird diese Methode durch die Anwendung eines kardioselektiven Beta-Blockers mit kurzer Halbwertszeit durchgeführt. Beta-Blocker haben nicht nur auf die Nekroseentwicklung, sondern auch auf die Inzidenz von Rhythmusstörungen - besonders in der Akutphase - Auswirkungen. Vor allem die mit dieser therapeutischen Maßnahme verbundene Reduktion von Kammerflimmern ist von großer Bedeutung.

  6. Stars For Citizens With Urban Star Parks and Lighting Specialists

    Science.gov (United States)

    Grigore, Valentin

    2015-08-01

    General contextOne hundred years ago, almost nobody imagine a life without stars every night even in the urban areas. Now, to see a starry sky is a special event for urban citizens.It is possible to see the stars even inside cities? Yes, but for that we need star parks and lighting specialists as partners.Educational aspectThe citizens must be able to identify the planets, constellations and other celestial objects in their urban residence. This is part of a basic education. The number of the people living in the urban area who never see the main constellations or important stars increase every year. We must do something for our urban community.What is an urban star park?An urban public park where we can see the main constellations can be considered an urban star park. There can be organized a lot of activities as practical lessons of astronomy, star parties, etc.Classification of the urban star parksA proposal for classification of the urban star parks taking in consideration the quality of the sky and the number of the city inhabitants:Two categories:- city star parks for cities with inhabitants- metropolis star parks for cities with > 100.000 inhabitantsFive levels of quality:- 1* level = can see stars of at least 1 magnitude with the naked eyes- 2* level = at least 2 mag- 3* level = at least 3 mag- 4* level= at least 4 mag- 5* level = at least 5 magThe urban star urban park structure and lighting systemA possible structure of a urban star park and sky-friend lighting including non-electric illumination are descripted.The International Commission on IlluminationA description of this structure which has as members national commissions from all over the world.Dark-sky activists - lighting specialistsNational Commissions on Illumination organize courses of lighting specialist. Dark-sky activists can become lighting specialists. The author shows his experience in this aspect as a recent lighting specialist and his cooperation with the Romanian National Commission on

  7. The star formation history of the Large Magellanic Cloud as seen by star clusters and stars

    OpenAIRE

    2010-01-01

    The aim of this work is to test to what extent the star cluster population of a galaxy can be utilised to constrain or estimate the star formation history, with the Large Magellanic Cloud as our testbed. We follow two methods to extract information about the star formation rate from star clusters, either using only the most massive clusters (Maschberger & Kroupa 2007) or using the whole cluster population, albeit this is only possible for a shorter age span. We compare these results with the ...

  8. Star Products for Relativistic Quantum Mechanics

    OpenAIRE

    Henselder, P.

    2007-01-01

    The star product formalism has proved to be an alternative formulation for nonrelativistic quantum mechanics. We want introduce here a covariant star product in order to extend the star product formalism to relativistic quantum mechanics in the proper time formulation.

  9. Stars Just Got Bigger - A 300 Solar Mass Star Uncovered

    Science.gov (United States)

    2010-07-01

    Using a combination of instruments on ESO's Very Large Telescope, astronomers have discovered the most massive stars to date, one weighing at birth more than 300 times the mass of the Sun, or twice as much as the currently accepted limit of 150 solar masses. The existence of these monsters - millions of times more luminous than the Sun, losing weight through very powerful winds - may provide an answer to the question "how massive can stars be?" A team of astronomers led by Paul Crowther, Professor of Astrophysics at the University of Sheffield, has used ESO's Very Large Telescope (VLT), as well as archival data from the NASA/ESA Hubble Space Telescope, to study two young clusters of stars, NGC 3603 and RMC 136a in detail. NGC 3603 is a cosmic factory where stars form frantically from the nebula's extended clouds of gas and dust, located 22 000 light-years away from the Sun (eso1005). RMC 136a (more often known as R136) is another cluster of young, massive and hot stars, which is located inside the Tarantula Nebula, in one of our neighbouring galaxies, the Large Magellanic Cloud, 165 000 light-years away (eso0613). The team found several stars with surface temperatures over 40 000 degrees, more than seven times hotter than our Sun, and a few tens of times larger and several million times brighter. Comparisons with models imply that several of these stars were born with masses in excess of 150 solar masses. The star R136a1, found in the R136 cluster, is the most massive star ever found, with a current mass of about 265 solar masses and with a birthweight of as much as 320 times that of the Sun. In NGC 3603, the astronomers could also directly measure the masses of two stars that belong to a double star system [1], as a validation of the models used. The stars A1, B and C in this cluster have estimated masses at birth above or close to 150 solar masses. Very massive stars produce very powerful outflows. "Unlike humans, these stars are born heavy and lose weight as

  10. Rotation of Giant Stars

    CERN Document Server

    Kissin, Yevgeni

    2015-01-01

    The internal rotation of post-main sequence stars is investigated, in response to the convective pumping of angular momentum toward the stellar core, combined with a tight magnetic coupling between core and envelope. The spin evolution is calculated using model stars of initial mass 1, 1.5 and $5\\,M_\\odot$, taking into account mass loss on the giant branches and the partitioning of angular momentum between the outer and inner envelope. We also include the deposition of orbital angular momentum from a sub-stellar companion, as influenced by tidal drag as well as the excitation of orbital eccentricity by a fluctuating gravitational quadrupole moment. A range of angular velocity profiles $\\Omega(r)$ is considered in the deep convective envelope, ranging from solid rotation to constant specific angular momentum. We focus on the backreaction of the Coriolis force on the inward pumping of angular momentum, and the threshold for dynamo action in the inner envelope. Quantitative agreement with measurements of core ro...

  11. The soliton stars evolution

    CERN Document Server

    Bednarek, I; Bednarek, Ilona; Manka, Ryszard

    1996-01-01

    The evolution of a soliton star filled with fermions is studied in the framework of general relativity. Such a system can be described by the surface tension $\\sigma$, the bag constant $B$, and the fermion number density affects the spacetime inside the soliton. Whether it is described by Friedman or de Sitter metric depends on the prevailing parameter. The whole spacetime is devided by the surface of the soliton into the false vacuum region inside the soliton and the true vacuum region outside, the latter being described by the Schwarzschild line element. The aim of this paper is to study the equations of motion of the domain wall in two cases. In the first case the de Sitter metric describes the interior in the first case, and in the second case it is replaced by the Friedman metric. In both of them the Schwarzschild metric is outside the soliton. From the analysis of obtained equations one can draw conclusions concerning further evolution of a soliton star.

  12. Morphogenesis of star dunes

    Science.gov (United States)

    Zhang, D.; Narteau, C.; Rozier, O.

    2010-12-01

    Dunes constantly adapt their shapes in response to the flow. Under multi-modal wind orientation, this permanent reorganization may result in the formation of star dunes, a highly complex structure with multiple arms, crests and slip faces oriented in different directions. Here, we show that this majestic dune feature can be described as a superposition of longitudinal dunes. In a 3D cellular automaton for sediment transport, star dunes form by amalgamation or by nucleation and growth of secondary longitudinal dunes. When the dune shape reaches a steady state, individual arms continue to propagate and detach from the main structure to feed other dunes in the neighborhood. From the sedimentary structures produced by the model we show that arm elongation is strongly dependent on the frequency at which the wind oscillates. This demonstrates that the elongation/propagation of dunes is a highly non-linear process that should account for crest reorientation over different time scales. We conclude that such a behavior needs to be taken into account when estimating climatic conditions from sedimentary structures on Earth or satellite images on other planetary bodies.

  13. Stars and Planets

    Science.gov (United States)

    Neta, Miguel

    2014-05-01

    'Estrelas e Planetas' (Stars and Planets) project was developed during the academic year 2009/2010 and was tested on three 3rd grade classes of one school in Quarteira, Portugal. The aim was to encourage the learning of science and the natural and physical phenomena through the construction and manipulation of materials that promote these themes - in this case astronomy. Throughout the project the students built a small book containing three themes of astronomy: differences between stars and planets, the solar system and the phases of the Moon. To each topic was devoted two sessions of about an hour each: the first to teach the theoretical aspects of the theme and the second session to assembly two pages of the book. All materials used (for theoretical sessions and for the construction of the book) and videos of the finished book are available for free use in www.miguelneta.pt/estrelaseplanetas. So far there is only a Portuguese version but soon will be published in English as well. This project won the Excellency Prize 2011 of Casa das Ciências, a portuguese site for teachers supported by the Calouste Gulbenkian Fundation (www.casadasciencias.org).

  14. The Stars of Heaven

    Science.gov (United States)

    Pickover, Clifford A.

    2004-05-01

    Do a little armchair space travel, rub elbows with alien life forms, and stretch your mind to the furthest corners of our uncharted universe. With this astonishing guidebook, you don't have to be an astronomer to explore the mysteries of stars and their profound meaning for human existence. Clifford A. Pickover tackles a range of topics from stellar evolution to the fundamental reasons why the universe permits life to flourish. He alternates sections that explain the mysteries of the cosmos with sections that dramatize mind-expanding concepts through a fictional dialog between futuristic humans and their alien peers (who embark on a journey beyond the reader's wildest imagination). This highly accessible and entertaining approach turns an intimidating subject into a scientific game open to all dreamers. Told in Pickover's inimitable blend of fascinating state-of-the-art science and whimsical science fiction, and packed with numerous diagrams and illustrations, The Stars of Heaven unfolds a world of paradox and mystery, one that will intrigue anyone who has ever pondered the night sky with wonder.

  15. Axions and the cooling of white dwarf stars

    CERN Document Server

    Isern, J; Torres, S; Catalan, S

    2008-01-01

    White dwarfs are the end-product of the lifes of intermediate- and low-mass stars and their evolution is described as a simple cooling process. Recently, it has been possible to determine with an unprecedented precision their luminosity function, that is, the number of stars per unit volume and luminosity interval. We show here that the shape of the bright branch of this function is only sensitive to the averaged cooling rate of white dwarfs and we propose to use this property to check the possible existence of axions, a proposed but not yet detected weakly interacting particle. Our results indicate that the inclusion of the emission of axions in the evolutionary models of white dwarfs noticeably improves the agreement between the theoretical calculations and the observational white dwarf luminosity function. The best fit is obtained for m_a cos^2 \\beta ~ 5 meV, where m_a is the mass of the axion and cos^2 \\beta is a free parameter. We also show that values larger than 10 meV are clearly excluded. The existin...

  16. STARS: A Year in Review

    Science.gov (United States)

    Association for the Advancement of Sustainability in Higher Education, 2011

    2011-01-01

    The Sustainability Tracking, Assessment & Rating System[TM] (STARS) is a program of AASHE, the Association for the Advancement of Sustainability in Higher Education. AASHE is a member-driven organization with a mission to empower higher education to lead the sustainability transformation. STARS was developed by AASHE with input and insight from…

  17. Physics of Neutron Star Crusts

    Directory of Open Access Journals (Sweden)

    Chamel Nicolas

    2008-12-01

    Full Text Available The physics of neutron star crusts is vast, involving many different research fields, from nuclear and condensed matter physics to general relativity. This review summarizes the progress, which has been achieved over the last few years, in modeling neutron star crusts, both at the microscopic and macroscopic levels. The confrontation of these theoretical models with observations is also briefly discussed.

  18. Star formation in Galactic flows

    Science.gov (United States)

    Smilgys, Romas; Bonnell, Ian A.

    2016-06-01

    We investigate the triggering of star formation in clouds that form in Galactic scale flows as the interstellar medium passes through spiral shocks. We use the Lagrangian nature of smoothed particle hydrodynamics simulations to trace how the star-forming gas is gathered into self-gravitating cores that collapse to form stars. Large-scale flows that arise due to Galactic dynamics create shocks of the order of 30 km s-1 that compress the gas and form dense clouds (n > several × 102 cm-3) in which self-gravity becomes relevant. These large-scale flows are necessary for creating the dense physical conditions for gravitational collapse and star formation. Local gravitational collapse requires densities in excess of n > 103 cm-3 which occur on size scales of ≈1 pc for low-mass star-forming regions (M 103 M⊙). Star formation in the 250 pc region lasts throughout the 5 Myr time-scale of the simulation with a star formation rate of ≈10-1 M⊙ yr-1 kpc-2. In the absence of feedback, the efficiency of the star formation per free-fall time varies from our assumed 100 per cent at our sink accretion radius to values of <10-3 at low densities.

  19. Possible Post-AGB Stars

    CERN Document Server

    Wallerstein, G; Shetrone, M D

    2003-01-01

    Radial velocities were measured for 5 potential post-AGB stars, two in the globular cluster NGC 1851 and three in the dSph galaxy Ursa Minor. All five potential PAGB stars were found to be radial velocity non-members.

  20. Mathematics Teaching with the Stars

    Science.gov (United States)

    McKinney, Sueanne E.; Bol, Linda; Berube, Clair

    2010-01-01

    The mathematics instructional approaches of effective elementary teachers in urban high- poverty schools were investigated. Approximately 99 urban elementary teachers were administered the Star Teacher Selection Interview; a total of 31 were identified as star teachers. These teachers were then administered the Instructional Practices…

  1. Stars get dizzy after lunch

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Michael [Department of Astrophysical Sciences, Princeton University, 5491 Frist Center, Princeton, NJ 08544 (United States); Penev, Kaloyan [Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Peyton Hall, Princeton, NJ 08544 (United States)

    2014-06-01

    Exoplanet searches have discovered a large number of {sup h}ot Jupiters{sup —}high-mass planets orbiting very close to their parent stars in nearly circular orbits. A number of these planets are sufficiently massive and close-in to be significantly affected by tidal dissipation in the parent star, to a degree parameterized by the tidal quality factor Q {sub *}. This process speeds up their star's rotation rate while reducing the planet's semimajor axis. In this paper, we investigate the tidal destruction of hot Jupiters. Because the orbital angular momenta of these planets are a significant fraction of their star's rotational angular momenta, they spin up their stars significantly while spiraling to their deaths. Using the Monte Carlo simulation, we predict that for Q {sub *} = 10{sup 6}, 3.9 × 10{sup –6} of stars with the Kepler Target Catalog's mass distribution should have a rotation period shorter than 1/3 day (8 hr) due to accreting a planet. Exoplanet surveys such as SuperWASP, HATnet, HATsouth, and KELT have already produced light curves of millions of stars. These two facts suggest that it may be possible to search for tidally destroyed planets by looking for stars with extremely short rotational periods, then looking for remnant planet cores around those candidates, anomalies in the metal distribution, or other signatures of the recent accretion of the planet.

  2. Stars Get Dizzy After Lunch

    Science.gov (United States)

    Zhang, Michael; Penev, Kaloyan

    2014-06-01

    Exoplanet searches have discovered a large number of "hot Jupiters"—high-mass planets orbiting very close to their parent stars in nearly circular orbits. A number of these planets are sufficiently massive and close-in to be significantly affected by tidal dissipation in the parent star, to a degree parameterized by the tidal quality factor Q *. This process speeds up their star's rotation rate while reducing the planet's semimajor axis. In this paper, we investigate the tidal destruction of hot Jupiters. Because the orbital angular momenta of these planets are a significant fraction of their star's rotational angular momenta, they spin up their stars significantly while spiraling to their deaths. Using the Monte Carlo simulation, we predict that for Q * = 106, 3.9 × 10-6 of stars with the Kepler Target Catalog's mass distribution should have a rotation period shorter than 1/3 day (8 hr) due to accreting a planet. Exoplanet surveys such as SuperWASP, HATnet, HATsouth, and KELT have already produced light curves of millions of stars. These two facts suggest that it may be possible to search for tidally destroyed planets by looking for stars with extremely short rotational periods, then looking for remnant planet cores around those candidates, anomalies in the metal distribution, or other signatures of the recent accretion of the planet.

  3. Axion emission from neutron stars

    Science.gov (United States)

    Iwamoto, N.

    1984-01-01

    It is shown that axion emission from neutron stars is the dominant energy-loss mechanism for a range of values of the Peccei-Quinn symmetry-breaking scale (F) not excluded by previous constraints. This gives the possibility of obtaining a better bound on F from measurements of surface temperature of neutron stars.

  4. Gravitational Stability of Boson Stars

    CERN Document Server

    Kusmartsev, Fjodor V; Schunck, Franz E

    1991-01-01

    We investigate the stability of general-relativistic boson stars by classifying singularities of differential mappings and compare it with the results of perturbation theory. Depending on the particle number, the star has the following regimes of behavior: stable, metastable, pulsation, and collapse.

  5. The Finslerian compact star model

    Energy Technology Data Exchange (ETDEWEB)

    Rahaman, Farook; Paul, Nupur [Jadavpur University, Department of Mathematics, Kolkata, West Bengal (India); De, S.S. [University of Calcutta, Department of Applied Mathematics, Kolkata (India); Ray, Saibal [Government College of Engineering and Ceramic Technology, Department of Physics, Kolkata, West Bengal (India); Jafry, M.A.K. [Shibpur Dinobundhoo Institution, Department of Physics, Howrah, West Bengal (India)

    2015-11-15

    We construct a toy model for compact stars based on the Finslerian structure of spacetime. By assuming a particular mass function, we find an exact solution of the Finsler-Einstein field equations with an anisotropic matter distribution. The solutions are revealed to be physically interesting and pertinent for the explanation of compact stars. (orig.)

  6. Opdriftsbaserede modeller for Wave Star

    DEFF Research Database (Denmark)

    Kramer, Morten

    Formålet med dette skrift er at få en forhåndsvurdering af mulige effektforøgelser for Wave Star ved anvendelse af aktiv akkumulatordrift. Disse vurderinger baseres på simuleringsmodeller for driften af Wave Star i uregelmæssige bølger. Modellen er udarbejdet i programmeringssproget Delphi og er en...

  7. New fully empirical calibrations of strong-line metallicity indicators in star forming galaxies

    CERN Document Server

    Curti, M; Mannucci, F; Marconi, A; Maiolino, R; Esposito, S

    2016-01-01

    We derive new empirical calibrations for strong-line diagnostics of gas phase metallicity in local star forming galaxies by uniformly applying the Te method over the full metallicity range probed by the Sloan Digital Sky Survey (SDSS). To measure electron temperatures at high metallicity, where the auroral lines needed are not detected in single galaxies, we stacked spectra of more than 110,000 galaxies from the SDSS in bins of log[O II]/H$\\beta$ and log[O III]/H$\\beta$. This stacking scheme does not assume any dependence of metallicity on mass or star formation rate, but only that galaxies with the same line ratios have the same oxygen abundance. We provide calibrations which span more than 1 dex in metallicity and are entirely defined on a consistent absolute Te metallicity scale for galaxies. We apply our calibrations to the SDSS sample and find that they provide consistent metallicity estimates to within 0.05 dex.

  8. The radius and mass of the subgiant star bet Hyi from interferometry and asteroseismology

    CERN Document Server

    North, J R; Bedding, T R; Ireland, M J; Jacob, A P; O'Byrne, J; Owens, S M; Robertson, J G; Tango, W J; Tuthill, P G

    2007-01-01

    We have used the Sydney University Stellar Interferometer (SUSI) to measure the angular diameter of beta Hydri. This star is a nearby G2 subgiant whose mean density was recently measured with high precision using asteroseismology. We determine the radius and effective temperature of the star to be 1.814+/-0.017 R_sun (0.9%) and 5872+/-44 K (0.7%) respectively. By combining this value with the mean density, as estimated from asteroseismology, we make a direct estimate of the stellar mass. We find a value of 1.07+/-0.03 M_sun (2.8%), which agrees with published estimates based on fitting in the H-R diagram, but has much higher precision. These results place valuable constraints on theoretical models of beta Hyi and its oscillation frequencies.

  9. $\\beta$-particle energy-summing correction for $\\beta$-delayed proton emission measurements

    CERN Document Server

    Meisel, Z; Crawford, H L; Cyburt, R H; Grinyer, G F; Langer, C; Montes, F; Schatz, H; Smith, K

    2016-01-01

    A common approach to studying $\\beta$-delayed proton emission is to measure the energy of the emitted proton and corresponding nuclear recoil in a double-sided silicon-strip detector (DSSD) after implanting the $\\beta$-delayed proton emitting ($\\beta$p) nucleus. However, in order to extract the proton-decay energy, the measured energy must be corrected for the additional energy implanted in the DSSD by the $\\beta$-particle emitted from the $\\beta$p nucleus, an effect referred to here as $\\beta$-summing. We present an approach to determine an accurate correction for $\\beta$-summing. Our method relies on the determination of the mean implantation depth of the $\\beta$p nucleus within the DSSD by analyzing the shape of the total (proton + recoil + $\\beta$) decay energy distribution shape. We validate this approach with other mean implantation depth measurement techniques that take advantage of energy deposition within DSSDs upstream and downstream of the implantation DSSD.

  10. Modelling of Sigma Scorpii, a high-mass binary with a Beta Cep variable primary component

    CERN Document Server

    Tkachenko, A; Pavlovski, K; Degroote, P; Papics, P I; Moravveji, E; Lehmann, H; Kolbas, V; Clemer, K

    2014-01-01

    High-mass binary stars are known to show an unexplained discrepancy between the dynamical masses of the individual components and those predicted by models. In this work, we study Sigma Scorpii, a double-lined spectroscopic binary system consisting of two B-type stars residing in an eccentric orbit. The more massive primary component is a Beta Cep-type pulsating variable star. Our analysis is based on a time-series of some 1000 high-resolution spectra collected with the CORALIE spectrograph in 2006, 2007, and 2008. We use two different approaches to determine the orbital parameters of the star; the spectral disentangling technique is used to separate the spectral contributions of the individual components in the composite spectra. The non-LTE based spectrum analysis of the disentangled spectra reveals two stars of similar spectral type and atmospheric chemical composition. Combined with the orbital inclination angle estimate found in the literature, our orbital elements allow a mass estimate of 14.7 +/- 4.5 a...

  11. VLT imaging of the {\\beta} Pictoris gas disk

    CERN Document Server

    Nilsson, R; Olofsson, G; Fathi, K; Thébault, Ph; Liseau, R

    2012-01-01

    Circumstellar debris disks older than a few Myr should be largely devoid of primordial gas remaining from the protoplanetary disk phase. Tracing the origin of observed atomic gas in Keplerian rotation in the edge-on debris disk surrounding the ~12 Myr old star {\\beta} Pictoris requires more detailed information about its spatial distribution than has previously been acquired by limited slit spectroscopy. Especially indications of asymmetries and presence of Ca II gas at high disk latitudes call for additional investigation. We set out to recover a complete image of the Fe I and Ca II gas emission around {\\beta} Pic by spatially resolved, high-resolution spectroscopic observations to better understand the morphology and origin of the gaseous disk component. The multiple fiber facility FLAMES/GIRAFFE at the VLT, with the large IFU ARGUS, was used to obtain spatially resolved optical spectra in four regions covering the northeast and southwest side of the disk. Emission lines from Fe I and Ca II were mapped and ...

  12. Study of the Cygnus Star-Forming Field

    Science.gov (United States)

    Christopherson, Christopher; Kaltcheva, Nadia

    2016-01-01

    The star-forming complexes in Cygnus extend nearly 30 deg in Galactic longitude and 20 deg in latitude, and most probably include star-formation sites located between 600 and 4000 pc. We combine the catalog by Heiles (2000) with uvbyβ photometric data from the catalog of Paunzen (2015) to collate a sample of O and B-type stars with precise homogeneous distances, color excess and available polarimetry. This allows us to identify star-forming sites at different distances along the line of sight and to investigate their spatial correlation to the interstellar matter. Further, we use this sample to study the orientation of the polarization as revealed by the polarized light of the bright early-type stars and analyze the polarization-extinction correlation for this field. Since dust grains align in the presence of a magnetic field cause the observed polarization at optical wavelengths, the data contain information about the large-scale component of the Galactic magnetic field. In addition, wide-field astrophotography equipment was used to image the Cygnus field in Hydrogen-alpha, Hydrogen-beta and the [OIII] line at 500.7 nm. This allows us to map the overall distribution of ionized material and the interstellar dust and trace large-scale regions where the physical conditions change rapidly due to supernova shock fronts and strong stellar winds. Acknowledgments: This work was supported by NSF grant AST- 1516932 and the Wisconsin Space Grant Consortium, NASA Space Grant College and Fellowship Program, NASA Training Grant #NNX14AP22H.

  13. Neutron-Capture Elements in Low Metallicity Stars within the Inner Galactic Halo

    Science.gov (United States)

    Jumper, Kenneth A.; Burris, Debra L.

    2017-01-01

    The inner galactic halo is home to some of the oldest and low metallicity stars known. These stars are local enough to observe heavy element synthesis in the oldest stars in our galaxy. The purpose of this research is to analyze the distributions of neutron capture elements in low metallicity stars to help us understand the nature of first stars, which are responsible for the chemical enrichment of our galaxy, and consequently get man closer to an answer to some of the most fundamental questions about the universe.. The researchers will analyze and measure the stellar abundances of metal poor stars using MOOG’s spectral synthesis. Heavy element formation is connected to stellar evolution, thus by observing the chronometric ages of the distributions of Thorium/Europium, one can determine the age of the oldest stars. Analyzing the distribution of Uranium and Thorium as chronometers can set a lower limit on the age of the Universe. The chemical composition in our oldest observable stars resemble that of the earliest stars. This demonstrates that these stars were not synthesized internally but a result of previous deaths of stars generations before. This in turn provides useful information about the first star’s formation, evolution and nucleosynthesis of stars, and the arrangement of the structure of the early Universe. The most r-process rich halo stars abundances are consistent with a scaled solar system r-process abundance distribution. Also, there is symmetry in the rare earth elements in the stars within the Galactic halo. However the lighter n-capture abundances don’t conform to the solar pattern. This suggests the possibility of multiple synthesis mechanisms for the n capture elements. The combinations could include the main r-process, V-P process (core collapsed super- novae), charged particle reactions with Beta delayed fission, and the weak r-process. The weak r-process is sometimes called the incomplete r-process does not have enough neutrons to

  14. NSCool: Neutron star cooling code

    Science.gov (United States)

    Page, Dany

    2016-09-01

    NSCool is a 1D (i.e., spherically symmetric) neutron star cooling code written in Fortran 77. The package also contains a series of EOSs (equation of state) to build stars, a series of pre-built stars, and a TOV (Tolman- Oppenheimer-Volkoff) integrator to build stars from an EOS. It can also handle “strange stars” that have a huge density discontinuity between the quark matter and the covering thin baryonic crust. NSCool solves the heat transport and energy balance equations in whole GR, resulting in a time sequence of temperature profiles (and, in particular, a Teff - age curve). Several heating processes are included, and more can easily be incorporated. In particular it can evolve a star undergoing accretion with the resulting deep crustal heating, under a steady or time-variable accretion rate. NSCool is robust, very fast, and highly modular, making it easy to add new subroutines for new processes.

  15. Grand unification of neutron stars.

    Science.gov (United States)

    Kaspi, Victoria M

    2010-04-20

    The last decade has shown us that the observational properties of neutron stars are remarkably diverse. From magnetars to rotating radio transients, from radio pulsars to isolated neutron stars, from central compact objects to millisecond pulsars, observational manifestations of neutron stars are surprisingly varied, with most properties totally unpredicted. The challenge is to establish an overarching physical theory of neutron stars and their birth properties that can explain this great diversity. Here I survey the disparate neutron stars classes, describe their properties, and highlight results made possible by the Chandra X-Ray Observatory, in celebration of its 10th anniversary. Finally, I describe the current status of efforts at physical "grand unification" of this wealth of observational phenomena, and comment on possibilities for Chandra's next decade in this field.

  16. Grand unification of neutron stars

    Science.gov (United States)

    Kaspi, Victoria M.

    2010-01-01

    The last decade has shown us that the observational properties of neutron stars are remarkably diverse. From magnetars to rotating radio transients, from radio pulsars to isolated neutron stars, from central compact objects to millisecond pulsars, observational manifestations of neutron stars are surprisingly varied, with most properties totally unpredicted. The challenge is to establish an overarching physical theory of neutron stars and their birth properties that can explain this great diversity. Here I survey the disparate neutron stars classes, describe their properties, and highlight results made possible by the Chandra X-Ray Observatory, in celebration of its 10th anniversary. Finally, I describe the current status of efforts at physical “grand unification” of this wealth of observational phenomena, and comment on possibilities for Chandra’s next decade in this field. PMID:20404205

  17. Physics of primordial star formation

    Science.gov (United States)

    Yoshida, Naoki

    2012-09-01

    The study of primordial star formation has a history of nearly sixty years. It is generally thought that primordial stars are one of the key elements in a broad range of topics in astronomy and cosmology, from Galactic chemical evolution to the formation of super-massive blackholes. We review recent progress in the theory of primordial star formation. The standard theory of cosmic structure formation posits that the present-day rich structure of the Universe developed through gravitational amplification of tiny matter density fluctuations left over from the Big Bang. It has become possible to study primordial star formation rigorously within the framework of the standard cosmological model. We first lay out the key physical processes in a primordial gas. Then, we introduce recent developments in computer simulations. Finally, we discuss prospects for future observations of the first generation of stars.

  18. Grand Unification in Neutron Stars

    CERN Document Server

    Kaspi, Victoria M

    2010-01-01

    The last decade has shown us that the observational properties of neutron stars are remarkably diverse. From magnetars to rotating radio transients, from radio pulsars to `isolated neutron stars,' from central compact objects to millisecond pulsars, observational manifestations of neutron stars are surprisingly varied, with most properties totally unpredicted. The challenge is to establish an overarching physical theory of neutron stars and their birth properties that can explain this great diversity. Here I survey the disparate neutron stars classes, describe their properties, and highlight results made possible by the Chandra X-ray Observatory, in celebration of its tenth anniversary. Finally, I describe the current status of efforts at physical `grand unification' of this wealth of observational phenomena, and comment on possibilities for Chandra's next decade in this field.

  19. A Swarm of Ancient Stars

    Science.gov (United States)

    1999-01-01

    This stellar swarm is M80 (NGC 6093), one of the densest of the 147 known globular star clusters in the Milky Way galaxy. Located about 28,000 light-years from Earth, M80 contains hundreds of thousands of stars, all held together by their mutual gravitational attraction. Globular clusters are particularly useful for studying stellar evolution, since all of the stars in the cluster have the same age (about 15 billion years), but cover a range of stellar masses. Every star visible in this image is either more highly evolved than, or in a few rare cases more massive than, our own Sun. Especially obvious are the bright red giants, which are stars similar to the Sun in mass that are nearing the ends of their lives.

  20. Star trackers for attitude determination

    DEFF Research Database (Denmark)

    Liebe, Carl Christian

    1995-01-01

    One problem comes to all spacecrafts using vector information. That is the problem of determining the attitude. This paper describes how the area of attitude determination instruments has evolved from simple pointing devices into the latest technology, which determines the attitude by utilizing...... a CCD camera and a powerful microcomputer. The instruments are called star trackers and they are capable of determining the attitude with an accuracy better than 1 arcsecond. The concept of the star tracker is explained. The obtainable accuracy is calculated, the numbers of stars to be included...... in the star catalogue are discussed and the acquisition of the initial attitude is explained. Finally the commercial market for star trackers is discussed...

  1. StarGuides Plus

    Science.gov (United States)

    Heck, A.

    StarGuides Plus represents the most comprehensive and accurately validated collection of practical data on organizations involved in astronomy, related space sciences and other related fields. This invaluable reference source (and its companion volume, StarBriefs Plus) should be on the reference shelf of every library, organization or individual with any interest in these areas. The coverage includes relevant universities, scientific committees, institutions, associations, societies, agencies, companies, bibliographic services, data centers, museums, dealers, distributors, funding organizations, journals, manufacturers, meteorological services, national norms & standard institutes, parent associations & societies, publishers, software producers & distributors, and so on. Besides astronomy and associated space sciences, related fields such as aeronautics, aeronomy, astronautics, atmospheric sciences, chemistry, communications, computer sciences, data processing, education, electronics, engineering, energetics, environment, geodesy, geophysics, information handling, management, mathematics, meteorology, optics, physics, remote sensing, and so on, are also covered where appropriate. After some thirty years in continuous compilation, verification and updating, StarGuides Plus currently gathers together some 6,000 entries from 100 countries. The information is presented in a clear, uncluttered manner for direct and easy use. For each entry, all practical data are listed: city, postal and electronic-mail addresses, telephone and fax numbers, URLs for WWW access, foundation years, numbers of members and/or numbers of staff, main activities, publications titles (with frequencies, ISS-Numbers and circulations), names and geographical coordinates of observing sites, names of planetariums, awards (prizes and/or distinctions) granted, etc. The entries are listed alphabetically in each country. An exhaustive index gives a breakdown not only by different designations and

  2. The first stars: a classification of CEMP-no stars

    CERN Document Server

    Maeder, Andre

    2015-01-01

    We propose and apply a new classification for the CEMP-no stars, which are "carbon-enhanced metal-poor" stars with no overabundance of s-elements and with [Fe/H] generally inferior or equal to -2.5. This classification is based on the changes in abundances for the elements and isotopes involved in the CNO, Ne-Na, and Mg-Al nuclear cycles. These abundances change very much owing to successive back and forth mixing motions between the He- and H-burning regions in massive stars (the "source stars" responsible for the chemical enrichment of the CEMP-no stars). The wide variety of the ratios [C/Fe], 12C/13C, [N/Fe], [O/Fe], [Na/Fe], [Mg/Fe], [Al/Fe], [Sr/Fe], and [Ba/Fe], which are the main characteristics making the CEMP-no and low s stars so peculiar, is described well in terms of the proposed nucleosynthetic classification. We note that the [(C+N+O)/Fe] ratios significantly increase for lower values of [Fe/H]. The classification of CEMP-no stars and the behavior of [(C+N+O)/Fe] support the presence, in the firs...

  3. Keplerian frequency of uniformly rotating neutron stars and quark stars

    CERN Document Server

    Haensel, P; Bejger, M; Lattimer, J M

    2009-01-01

    We calculate Keplerian (mass shedding) configurations of rigidly rotating neutron stars and quark stars with crusts. We check the validity of empirical formula for Keplerian frequency, f_K, proposed by Lattimer & Prakash, f_K(M)=C (M/M_sun)^1/2 (R/10km)^-3/2, where M is the (gravitational) mass of Keplerian configuration, R is the (circumferential) radius of the non-rotating configuration of the same gravitational mass, and C = 1.04 kHz. Numerical calculations are performed using precise 2-D codes based on the multi-domain spectral methods. We use a representative set of equations of state (EOSs) of neutron stars and quark stars. We show that the empirical formula for f_K(M) holds within a few percent for neutron stars with realistic EOSs, provided 0.5 M_sun < M < 0.9 M_max,stat, where M_max,stat is the maximum allowable mass of non-rotating neutron stars for an EOS, and C=C_NS=1.08 kHz. Similar precision is obtained for quark stars with 0.5 M_sun < M < 0.9 M_max,stat. For maximal crust masses...

  4. The Destructive Birth of Massive Stars and Massive Star Clusters

    Science.gov (United States)

    Rosen, Anna; Krumholz, Mark; McKee, Christopher F.; Klein, Richard I.; Ramirez-Ruiz, Enrico

    2017-01-01

    Massive stars play an essential role in the Universe. They are rare, yet the energy and momentum they inject into the interstellar medium with their intense radiation fields dwarfs the contribution by their vastly more numerous low-mass cousins. Previous theoretical and observational studies have concluded that the feedback associated with massive stars' radiation fields is the dominant mechanism regulating massive star and massive star cluster (MSC) formation. Therefore detailed simulation of the formation of massive stars and MSCs, which host hundreds to thousands of massive stars, requires an accurate treatment of radiation. For this purpose, we have developed a new, highly accurate hybrid radiation algorithm that properly treats the absorption of the direct radiation field from stars and the re-emission and processing by interstellar dust. We use our new tool to perform a suite of three-dimensional radiation-hydrodynamic simulations of the formation of massive stars and MSCs. For individual massive stellar systems, we simulate the collapse of massive pre-stellar cores with laminar and turbulent initial conditions and properly resolve regions where we expect instabilities to grow. We find that mass is channeled to the massive stellar system via gravitational and Rayleigh-Taylor (RT) instabilities. For laminar initial conditions, proper treatment of the direct radiation field produces later onset of RT instability, but does not suppress it entirely provided the edges of the radiation-dominated bubbles are adequately resolved. RT instabilities arise immediately for turbulent pre-stellar cores because the initial turbulence seeds the instabilities. To model MSC formation, we simulate the collapse of a dense, turbulent, magnetized Mcl = 106 M⊙ molecular cloud. We find that the influence of the magnetic pressure and radiative feedback slows down star formation. Furthermore, we find that star formation is suppressed along dense filaments where the magnetic field is

  5. Improving night sky star image processing algorithm for star sensors.

    Science.gov (United States)

    Arbabmir, Mohammad Vali; Mohammadi, Seyyed Mohammad; Salahshour, Sadegh; Somayehee, Farshad

    2014-04-01

    In this paper, the night sky star image processing algorithm, consisting of image preprocessing, star pattern recognition, and centroiding steps, is improved. It is shown that the proposed noise reduction approach can preserve more necessary information than other frequently used approaches. It is also shown that the proposed thresholding method unlike commonly used techniques can properly perform image binarization, especially in images with uneven illumination. Moreover, the higher performance rate and lower average centroiding estimation error of near 0.045 for 400 simulated images compared to other algorithms show the high capability of the proposed night sky star image processing algorithm.

  6. Axion star collisions with Neutron stars and Fast Radio Bursts

    CERN Document Server

    Raby, Stuart

    2016-01-01

    Axions may make a significant contribution to the dark matter of the universe. It has been suggested that these dark matter axions may condense into localized clumps, called "axion stars." In this paper we argue that collisions of dilute axion stars with neutron stars may be the origin of most of the observed fast radio bursts. This idea is a variation of an idea originally proposed by Iwazaki. However, instead of the surface effect of Iwazaki, we propose a perhaps stronger volume effect caused by the induced time dependent electric dipole moment of neutrons.

  7. Axion star collisions with neutron stars and fast radio bursts

    Science.gov (United States)

    Raby, Stuart

    2016-11-01

    Axions may make a significant contribution to the dark matter of the Universe. It has been suggested that these dark matter axions may condense into localized clumps, called "axion stars." In this paper we argue that collisions of dilute axion stars with neutron stars, of the type known as "magnetars," may be the origin of most of the observed fast radio bursts. This idea is a variation of an idea originally proposed by Iwazaki. However, instead of the surface effect of Iwazaki, we propose a perhaps stronger volume effect caused by the induced time dependent electric dipole moment of neutrons.

  8. Star spotting at CERN

    CERN Multimedia

    2008-01-01

    This June, two American celebrities (and physics enthusiasts!) came to CERN. Brian Cox gave Mike Einziger (right), lead guitarist with the rock band Incubus, the star treatment in the ATLAS cavern. Jesse Dylan embraces the spirit of ATLAS! Mike Einziger, lead guitarist with the rock band Incubus, visited CERN on Friday 13 June between concerts in Finland and England. Einziger, a lifelong science enthusiast descended into the ATLAS and CMS caverns and visited the SM18 test magnet facility during his brief tour of CERN. Einziger learned about the LHC through watching online lectures from University of Manchester and ATLAS physicist Brian Cox, and was thrilled to have the chance to see the detectors in person. The musician has created an orchestral piece, inspired in part by the work being done at CERN for the LHC, which will have its debut in Los Angeles on 23 August. Just over a week earlier, Jesse Dylan, Hollywood film director a...

  9. Double Degenerate Stars

    Institute of Scientific and Technical Information of China (English)

    LUO Xin-Lian; BAI Hua; ZHAO Lei

    2008-01-01

    Regardless of the formation mechanism, an exotic object, the double degenerate star (DDS), is introduced and investigated, which is composed of baryonic matter and some unknown fermion dark matter. Different from the simple white dwarfs (WDs), there is additional gravitational force provided by the unknown fermion component inside DDSs, which may strongly affect the structure and the stability of such kind of objects. Many possible and strange observational phenomena connecting with them are concisely discussed. Similar to the normal WD, this object can also experience thermonuclear explosion as type Ia supernova explosion when DDS's mass exceeds the maximum mass that can be supported by electron degeneracy pressure. However, since the total mass of baryonic matter can be much lower than that of WD at Chandrasekhar mass limit, the peak luminosity should be much dimmer than what we expect before, which may throw a slight shadow on the standard candle of SN Ia in the research of cosmology.

  10. Building Cosmological Frozen Stars

    CERN Document Server

    Kastor, David

    2016-01-01

    Janis-Newman-Winicour (JNW) spacetimes generalize the Schwarzschild solution to include a massless scalar field. Although suffering from naked singularities, they share the `frozen star' features of Schwarzschild black holes. Cosmological versions of the JNW spacetimes were discovered some time ago by Husain, Martinez and Nunez and by Fonarev. Unlike Schwarzschild-deSitter black holes, these solutions are dynamical, and the scarcity of exact solutions for dynamical black holes in cosmological backgrounds motivates their further study. Here we show how the cosmological JNW spacetimes can be built, starting from simpler, static, higher dimensional, vacuum `JNW brane' solutions via two different generalized dimensional reduction schemes that together cover the full range of JNW parameter space. Cosmological versions of a BPS limit of charged dilaton black holes are also known. JNW spacetimes represent a different limiting case of the charged, dilaton black hole family. We expect that understanding this second da...

  11. Nonassociative Weyl star products

    CERN Document Server

    Kupriyanov, V G

    2015-01-01

    Deformation quantization is a formal deformation of the algebra of smooth functions on some manifold. In the classical setting, the Poisson bracket serves as an initial conditions, while the associativity allows to proceed to higher orders. Some applications to string theory require deformation in the direction of a quasi-Poisson bracket (that does not satisfy the Jacobi identity). This initial conditions is incompatible with associativity, it is quite unclear which restrictions can be imposed on the deformation. We show that for any quasi-Poisson bracket the deformation quantization exists and is essentially unique if one requires (weak) hermiticity and the Weyl condition. We also propose an iterative procedure that allows to compute the star product up to any desired order.

  12. Resistance training & beta-hydroxy-beta-methylbutyrate supplementation on hormones

    Directory of Open Access Journals (Sweden)

    Hamid Arazi

    2015-10-01

    Full Text Available RESUMOIntroduction:In recent years, there was an increased interest on the effects of beta-hydroxy-beta-methylbutyrate (HMB supplementation on skeletal muscle due to its anti-catabolic effects.Objectives:To investigate the effect of HMB supplementation on body composition, muscular strength and anabolic-catabolic hormones after resistance training.Methods:Twenty amateur male athletes were randomly assigned to supplement and control groups in a double-blind crossover design and participated in four weeks resistance training. Before and after the test period fasting blood samples were obtained to determine anabolic (the growth hormone and testosterone and catabolic (cortisol hormones, and fat mass, lean body mass (LBM and muscular strength were measured. Dependent and independent t-tests were used to analyze data.Results:After the training period, there were no significant differen-ces between the groups with respect to fat mass, LBM and anabolic-catabolic hormones. HMB supplementation resulted in a significantly greater strength gain (p≤0.05.Conclusion:Greater increase in strength for HMB group was not accompanied by body composition and basal circulating anabolic-catabolic hormonal changes. It seems that HMB supplementation may have beneficial effects on neurological adaptations of strength gain.

  13. Likely Members of the Beta Pictoris and AB Doradus Moving Groups in the North

    CERN Document Server

    Schlieder, Joshua E; Simon, Michal

    2012-01-01

    We present first results from follow-up of targets in the northern hemisphere Beta Pictoris and AB Doradus moving group candidate list of Schlieder, Lepine, and Simon (2012). We obtained high-resolution, near-infrared spectra of 27 candidate members to measure their radial velocities and confirm consistent group kinematics. We identify 15 candidates with consistent predicted and measured radial velocities, perform analyses of their 6-dimensional (U,V,W,X,Y,Z) Galactic kinematics, and compare to known group member distributions. Based on these analyses, we propose that 7 Beta Pic and 8 AB Dor candidates are likely new group members. Four of the likely new Beta Pic stars are binaries; one a double lined spectroscopic system. Three of the proposed AB Dor stars are binaries. Counting all binary components, we propose 22 likely members of these young, moving groups. The majority of the proposed members are M2 to M5 dwarfs, the earliest being of type K2. We also present preliminary parameters for the two new spectr...

  14. The Gemini NICI Planet-Finding Campaign: The Orbit of the Young Exoplanet beta Pictoris b

    CERN Document Server

    Nielsen, Eric L; Wahhaj, Zahed; Biller, Beth A; Hayward, Thomas L; Males, Jared R; Close, Laird M; Morzinski, Katie M; Skemer, Andrew J; Kuchner, Marc J; Chun, Mark; Ftaclas, Christ; Toomey, Douglas W

    2014-01-01

    We present new astrometry for the young (12-21 Myr) exoplanet beta Pictoris b taken with the Gemini/NICI, Magellan/MagAO+Clio2, and Magellan/MagAO+VisAO instruments between 2009 and 2012. The high dynamic range of our observations allows us to measure the relative position of beta Pic b with respect to its primary star with greater accuracy than previous observations. Based on a Markov Chain Monte Carlo analysis, we find the planet has an orbital semi-major axis of 9.2 [+8.3, -0.5] AU and orbital eccentricity <0.15 at 68% confidence (with 95% confidence intervals of 8.2-72.3 AU and 0.00-0.88 for semi-major axis and eccentricity, respectively). We find that the planet has reached its maximum projected elongation, enabling higher precision determination of the orbital parameters than previously possible, and that the planet's projected separation is currently decreasing. With unsaturated data of the entire beta Pic system (primary star, planet, and disk) obtained thanks to NICI's semi-transparent focal plane...

  15. Are strange stars distinguishable from neutron stars by their cooling behaviour?

    OpenAIRE

    Schaab, Ch.; Hermann, B.; Weber, F.; Weigel, M. K.

    1997-01-01

    The general statement that strange stars cool more rapidly than neutron stars is investigated in greater detail. It is found that the direct Urca process could be forbidden not only in neutron stars but also in strange stars. If so, strange stars would be slowly cooling and their surface temperatures would be more or less indistinguishable from those of slowly cooling neutron stars. The case of enhanced cooling is reinvestigated as well. It is found that strange stars cool significantly more ...

  16. "Catch a Star !"

    Science.gov (United States)

    2002-05-01

    ESO and EAAE Launch Web-based Educational Programme for Europe's Schools Catch a star!... and discover all its secrets! This is the full title of an innovative educational project, launched today by the European Southern Observatory (ESO) and the European Association for Astronomy Education (EAAE). It welcomes all students in Europe's schools to an exciting web-based programme with a competition. It takes place within the context of the EC-sponsored European Week of Science and Technology (EWST) - 2002 . This unique project revolves around a web-based competition and is centred on astronomy. It is specifically conceived to stimulate the interest of young people in various aspects of this well-known field of science, but will also be of interest to the broad public. What is "Catch a Star!" about? [Go to Catch a Star Website] The programme features useful components from the world of research, but it is specifically tailored to (high-)school students. Younger participants are also welcome. Groups of up to four persons (e.g., three students and one teacher) have to select an astronomical object - a bright star, a distant galaxy, a beautiful comet, a planet or a moon in the solar system, or some other celestial body. Like detectives, they must then endeavour to find as much information as possible about "their" object. This information may be about the position and visibility in the sky, the physical and chemical characteristics, particular historical aspects, related mythology and sky lore, etc. They can use any source available, the web, books, newspaper and magazine articles, CDs etc. for this work. The group members must prepare a (short) summarising report about this investigation and "their" object, with their own ideas and conclusions, and send it to ESO (email address: eduinfo@eso.org). A jury, consisting of specialists from ESO and the EAAE, will carefully evaluate these reports. All projects that are found to fulfill the stipulated requirements, including a

  17. Abstraction Mechanisms in the BETA Programming Language

    DEFF Research Database (Denmark)

    Kristensen, Bent Bruun; Madsen, Ole Lehrmann; Møller-Pedersen, Birger

    1983-01-01

    ]) --- covering both data, procedural and control abstractions, substituting constructs like class, procedure, function and type. Correspondingly objects, procedure activation records and variables are all regarded as special cases of the basic building block of program executions: the entity. A pattern thus......The BETA programming language is developed as part of the BETA project. The purpose of this project is to develop concepts, constructs and tools in the field of programming and programming languages. BETA has been developed from 1975 on and the various stages of the language are documented in [BETA...... a]. The application area of BETA is programming of embedded as well as distributed computing systems. For this reason a major goal has been to develop constructs that may be efficiently implemented. Furthermore the BETA language is intended to have a few number of basic but general constructs...

  18. Orbital Eccentricity Distribution of Solar-Neighbour Halo Stars

    CERN Document Server

    Hattori, Kohei

    2011-01-01

    We present theoretical calculations for the differential distribution of stellar orbital eccentricity for a sample of solar-neighbour halo stars. Two types of static, spherical gravitational potentials are adopted to define the eccentricity e for given energy E and angular momentum L, such as an isochrone potential and a Navarro-Frenk-White potential that can serve as two extreme ends covering in-between any realistic potential of the Milky Way halo. The solar-neighbour eccentricity distribution \\Delta N(e) is then formulated, based on a static distribution function of the form f(E,L) in which the velocity anisotropy parameter \\beta monotonically increases in the radial direction away from the galaxy center, such that beta is below unity (near isotropic velocity dispersion) in the central region and asymptotically approaches \\sim 1 (radially anisotropic velocity dispersion) in the far distant region of the halo. We find that \\Delta N(e) sensitively depends upon the radial profile of \\beta, and this sensitivit...

  19. Strange-quark-matter stars

    Energy Technology Data Exchange (ETDEWEB)

    Glendenning, N.K.

    1989-11-01

    We investigate the implications of rapid rotation corresponding to the frequency of the new pulsar reported in the supernovae remnant SN1987A. It places very stringent conditions on the equation of state if the star is assumed to be bound by gravity alone. We find that the central energy density of the star must be greater than 13 times that of nuclear density to be stable against the most optimistic estimate of general relativistic instabilities. This is too high for the matter to consist of individual hadrons. We conclude that it is implausible that the newly discovered pulsar, if its half-millisecond signals are attributable to rotation, is a neutron star. We show that it can be a strange quark star, and that the entire family of strange stars can sustain high rotation if strange matter is stable at an energy density exceeding about 5.4 times that of nuclear matter. We discuss the conversion of a neutron star to strange star, the possible existence of a crust of heavy ions held in suspension by centrifugal and electric forces, the cooling and other features. 34 refs., 10 figs., 1 tab.

  20. Rapidly rotating neutron star progenitors

    Science.gov (United States)

    Postnov, K. A.; Kuranov, A. G.; Kolesnikov, D. A.; Popov, S. B.; Porayko, N. K.

    2016-12-01

    Rotating proto-neutron stars can be important sources of gravitational waves to be searched for by present-day and future interferometric detectors. It was demonstrated by Imshennik that in extreme cases the rapid rotation of a collapsing stellar core may lead to fission and formation of a binary proto-neutron star which subsequently merges due to gravitational wave emission. In this paper, we show that such dynamically unstable collapsing stellar cores may be the product of a former merger process of two stellar cores in a common envelope. We applied population synthesis calculations to assess the expected fraction of such rapidly rotating stellar cores which may lead to fission and formation of a pair of proto-neutron stars. We have used the BSE (Binary Star Evolution) population synthesis code supplemented with a new treatment of stellar core rotation during the evolution via effective core-envelope coupling, characterized by the coupling time, τc. The validity of this approach is checked by direct MESA calculations of the evolution of a rotating 15 M⊙ star. From comparison of the calculated spin distribution of young neutron stars with the observed one, reported by Popov and Turolla, we infer the value τc ≃ 5 × 105 yr. We show that merging of stellar cores in common envelopes can lead to collapses with dynamically unstable proto-neutron stars, with their formation rate being ˜0.1-1 per cent of the total core collapses, depending on the common envelope efficiency.

  1. Constraining the Low-Mass Slope of the Star Formation Sequence at 0.5

    CERN Document Server

    Whitaker, Katherine E; Leja, Joel; van Dokkum, Pieter G; Henry, Alaina; Skelton, Rosalind E; Fumagalli, Mattia; Momcheva, Ivelina G; Brammer, Gabriel B; Labbe, Ivo; Nelson, Erica J; Rigby, Jane R

    2014-01-01

    We constrain the slope of the star formation rate ($\\log\\Psi$) to stellar mass ($\\log\\mathrm{M_{\\star}}$) relation down to $\\log(\\mathrm{M_{\\star}/M_{\\odot}})=8.4$ ($\\log(\\mathrm{M_{\\star}/M_{\\odot}})=9.2$) at $z=0.5$ ($z=2.5$) with a mass-complete sample of 39,106 star-forming galaxies selected from the 3D-HST photometric catalogs, using deep photometry in the CANDELS fields. For the first time, we find that the slope is dependent on stellar mass, such that it is steeper at low masses ($\\log\\mathrm{\\Psi}\\propto\\log\\mathrm{M_{\\star}}$) than at high masses ($\\log\\mathrm{\\Psi}\\propto(0.3-0.6)\\log\\mathrm{M_{\\star}}$). These steeper low mass slopes are found for three different star formation indicators: the combination of the ultraviolet (UV) and infrared (IR), calibrated from a stacking analysis of Spitzer/MIPS 24$\\mu$m imaging; $\\beta$-corrected UV SFRs; and H$\\alpha$ SFRs. The normalization of the sequence evolves differently in distinct mass regimes as well: for galaxies less massive than $\\log(\\mathrm{M_{\\s...

  2. The star cluster - field star connection in nearby spiral galaxies. II. Field star and cluster formation histories and their relation

    NARCIS (Netherlands)

    Silva-Villa, E.; Larsen, S.S.

    2011-01-01

    Context. Recent studies have started to cast doubt on the assumption that most stars are formed in clusters. Observational studies of field stars and star cluster systems in nearby galaxies can lead to better constraints on the fraction of stars forming in clusters. Ultimately this may lead to a bet

  3. Locating Star-Forming Regions in Quasar Host Galaxies

    CERN Document Server

    Young, J E; Shemmer, O; Netzer, H; Gronwall, C; Lutz, Dieter; Ciardullo, R; Sturm, Eckhard

    2013-01-01

    We present a study of the morphology and intensity of star formation in the host galaxies of eight Palomar-Green quasars using observations with the Hubble Space Telescope. Our observations are motivated by recent evidence for a close relationship between black hole growth and the stellar mass evolution in its host galaxy. We use narrow-band [O II] $\\lambda$3727, H$\\beta$, [O III] $\\lambda$5007 and Pa$\\alpha$ images, taken with the WFPC2 and NICMOS instruments, to map the morphology of line-emitting regions, and, after extinction corrections, diagnose the excitation mechanism and infer star-formation rates. Significant challenges in this type of work are the separation of the quasar light from the stellar continuum and the quasar-excited gas from the star-forming regions. To this end, we present a novel technique for image decomposition and subtraction of quasar light. Our primary result is the detection of extended line-emitting regions with sizes ranging from 0.5 to 5 kpc and distributed symmetrically aroun...

  4. Chromospheric Models and the Oxygen Abundance in Giant Stars

    CERN Document Server

    Dupree, A K; Kurucz, R L

    2016-01-01

    Realistic stellar atmospheric models of two typical metal-poor giant stars in Omega Centauri that include a chromosphere influence the formation of optical lines of Oxygen I: the forbidden lines (630nm, 636nm) and the infrared triplet (777.1-777.5 nm). One-dimensional semi-empirical non-LTE models are constructed based on observed Balmer lines. A full non-LTE formulation is applied in evaluating line strengths of O I including photoionization by the Lyman continuum and photoexcitation by Ly-alpha and Ly-beta. Chromospheric models (CHR) yield forbidden oxygen transitions that are stronger than in radiative/convective equilibrium (RCE) models. The triplet oxygen lines from high levels also appear stronger than produced in an RCE model. The inferred oxygen abundance from realistic CHR models for these two stars is decreased by factors ~3 as compared to values derived from RCE models. A lower oxygen abundance suggests that intermediate mass AGB stars contribute to the observed abundance pattern in globular cluste...

  5. Magnetars: Structure and evolution from p-star models

    CERN Document Server

    Cea, P

    2005-01-01

    P-stars are compact stars made of up and down quarks in $\\beta$-equilibrium with electrons in a chromomagnetic condensate. We discuss p-stars endowed with super strong dipolar magnetic field which, following consolidated tradition in literature, are referred to as magnetars. We show that soft gamma-ray repeaters and anomalous $X$-ray pulsars can be understood within our theory. We find a well defined criterion to distinguish rotation powered pulsars from magnetic powered pulsars. We show that glitches, that in our magnetars are triggered by magnetic dissipative effects in the inner core, explain both the quiescent emission and bursts in soft gamma-ray repeaters and anomalous $X$-ray pulsars. We account for the braking glitch from SGR 1900+14 and the normal glitch from AXP 1E 2259+586 following a giant burst. We discuss and explain the observed anti correlation between hardness ratio and intensity. Within our magnetar theory we are able to account quantitatively for light curves for both gamma-ray repeaters an...

  6. Detailed analysis of Balmer lines in cool dwarf stars

    CERN Document Server

    Barklem, P S; Allende-Prieto, C; Kochukhov, O P; Piskunov, N; O'Mara, B J

    2002-01-01

    An analysis of H alpha and H beta spectra in a sample of 30 cool dwarf and subgiant stars is presented using MARCS model atmospheres based on the most recent calculations of the line opacities. A detailed quantitative comparison of the solar flux spectra with model spectra shows that Balmer line profile shapes, and therefore the temperature structure in the line formation region, are best represented under the mixing length theory by any combination of a low mixing-length parameter alpha and a low convective structure parameter y. A slightly lower effective temperature is obtained for the sun than the accepted value, which we attribute to errors in models and line opacities. The programme stars span temperatures from 4800 to 7100 K and include a small number of population II stars. Effective temperatures have been derived using a quantitative fitting method with a detailed error analysis. Our temperatures find good agreement with those from the Infrared Flux Method (IRFM) near solar metallicity but show diffe...

  7. Evolution in Binary and Triple Stars, with an application to SS Lac

    CERN Document Server

    Eggleton, P P; Eggleton, Peter P.; Kiseleva-Eggleton, Ludmila

    2001-01-01

    We present equations governing the way in which both the orbit and the intrinsic spins of stars in a close binary should evolve subject to a number of perturbing forces, including the effect of a third body in a possibly inclined wider orbit. We illustrate the solutions in some binary-star and triple-star situations: tidal friction in a wide but eccentric orbit of a radio pulsar about a B star, the Darwin and eccentricity instabilities in a more massive but shorter-period massive X-ray binary, and the interaction of tidal friction with Kozai cycles in a triple such as Algol (beta-Per), at an early stage in that star's life when all 3 components were ZAMS stars. We also attempt to model in some detail the interesting triple system SS Lac, which stopped eclipsing in about 1950. We find that our model of SS Lac is quite constrained by the relatively good observational data of this system, and leads to a specific inclination (29 deg) of the outer orbit relative to the inner orbit at epoch zero (1912). Although th...

  8. Milk Intolerance, Beta-Casein and Lactose.

    Science.gov (United States)

    Pal, Sebely; Woodford, Keith; Kukuljan, Sonja; Ho, Suleen

    2015-08-31

    True lactose intolerance (symptoms stemming from lactose malabsorption) is less common than is widely perceived, and should be viewed as just one potential cause of cows' milk intolerance. There is increasing evidence that A1 beta-casein, a protein produced by a major proportion of European-origin cattle but not purebred Asian or African cattle, is also associated with cows' milk intolerance. In humans, digestion of bovine A1 beta-casein, but not the alternative A2 beta-casein, releases beta-casomorphin-7, which activates μ-opioid receptors expressed throughout the gastrointestinal tract and body. Studies in rodents show that milk containing A1 beta-casein significantly increases gastrointestinal transit time, production of dipeptidyl peptidase-4 and the inflammatory marker myeloperoxidase compared with milk containing A2 beta-casein. Co-administration of the opioid receptor antagonist naloxone blocks the myeloperoxidase and gastrointestinal motility effects, indicating opioid signaling pathway involvement. In humans, a double-blind, randomized cross-over study showed that participants consuming A1 beta-casein type cows' milk experienced statistically significantly higher Bristol stool values compared with those receiving A2 beta-casein milk. Additionally, a statistically significant positive association between abdominal pain and stool consistency was observed when participants consumed the A1 but not the A2 diet. Further studies of the role of A1 beta-casein in milk intolerance are needed.

  9. Sawtooth crashes at high beta on JET

    Energy Technology Data Exchange (ETDEWEB)

    Alper, B.; Huysmans, G.T.A.; Sips, A.C.C. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Nave, M.F.F. [Universidade Tecnica, Lisbon (Portugal). Inst. Superior Tecnico

    1994-07-01

    The sawtooth crashes on JET display features which depend on beta. The main observation is a transient bulging of flux surfaces (duration inferior to 30 microsec.), which is predominantly on the low field side and extends to larger radii as beta increases. This phenomenon reaches the plasma boundary when beta{sub N} exceeds 0.5 and in these cases is followed by an ELM within 50 microsec. These sawtooth/ELM events limit plasma performance. Modelling of mode coupling shows qualitative agreement between observations of the structure of the sawtooth precursor and the calculated internal kink mode at high beta. (authors). 6 refs., 5 figs.

  10. Milk Intolerance, Beta-Casein and Lactose

    Directory of Open Access Journals (Sweden)

    Sebely Pal

    2015-08-01

    Full Text Available True lactose intolerance (symptoms stemming from lactose malabsorption is less common than is widely perceived, and should be viewed as just one potential cause of cows’ milk intolerance. There is increasing evidence that A1 beta-casein, a protein produced by a major proportion of European-origin cattle but not purebred Asian or African cattle, is also associated with cows’ milk intolerance. In humans, digestion of bovine A1 beta-casein, but not the alternative A2 beta-casein, releases beta-casomorphin-7, which activates μ-opioid receptors expressed throughout the gastrointestinal tract and body. Studies in rodents show that milk containing A1 beta-casein significantly increases gastrointestinal transit time, production of dipeptidyl peptidase-4 and the inflammatory marker myeloperoxidase compared with milk containing A2 beta-casein. Co-administration of the opioid receptor antagonist naloxone blocks the myeloperoxidase and gastrointestinal motility effects, indicating opioid signaling pathway involvement. In humans, a double-blind, randomized cross-over study showed that participants consuming A1 beta-casein type cows’ milk experienced statistically significantly higher Bristol stool values compared with those receiving A2 beta-casein milk. Additionally, a statistically significant positive association between abdominal pain and stool consistency was observed when participants consumed the A1 but not the A2 diet. Further studies of the role of A1 beta-casein in milk intolerance are needed.

  11. Untangling the Nature of Spatial Variations of Cold Dust Properties in Star Forming Galaxies

    CERN Document Server

    Kirkpatrick, Allison; Kennicutt, Robert; Galametz, Maud; Gordon, Karl; Groves, Brent; Hunt, Leslie; Dale, Daniel; Hinz, Joannah; Tabatabaei, Fatemeh

    2014-01-01

    We investigate the far-infrared (IR) dust emission for 20 local star forming galaxies from the Key Insights on Nearby Galaxies: A Far-IR Survey with Herschel (KINGFISH) sample. We model the far-IR/submillimeter spectral energy distribution (SED) using images from Spitzer Space Telescope and Herschel Space Observatory. We calculate the cold dust temperature (T(cold)) and emissivity (beta) on a pixel by pixel basis (where each pixel ranges from 0.1-3 kpc^2) using a two temperature modified blackbody fitting routine. Our fitting method allows us to investigate the resolved nature of temperature and emissivity variations by modeling from the galaxy centers to the outskirts (physical scales of ~15-50 kpc, depending on the size of the galaxy). We fit each SED in two ways: (1) fit T(cold) and beta simultaneously, (2) hold beta constant and fit T(cold). We compare T(cold) and beta with star formation rates (calculated from L(Halpha) and L(24)), the luminosity of the old stellar population (traced through L(3.6), and ...

  12. Magnetic propeller in symbiotic stars

    OpenAIRE

    Panferov, Alexander; Mikolajewski, Maciej

    2000-01-01

    Rapidly spinning magnetic white dwarfs in symbiotic stars may pass through the propeller stage. It is believed that a magnetic propeller acts in two such stars CH Cyg and MWC 560. We review a diversity of manifestations of the propeller there. In these systems in a quiescent state the accretion onto a white dwarf from the strong enough wind of a companion star is suppressed by the magnetic field, and the hot component luminosity is low. Since the gas stored in the envelope eventually settles ...

  13. Neutron star structure from QCD

    Energy Technology Data Exchange (ETDEWEB)

    Fraga, Eduardo S. [Universidade Federal do Rio de Janeiro, Instituto de Fisica, Rio de Janeiro, RJ (Brazil); Kurkela, Aleksi [PH-TH, Case C01600, CERN, Theory Division, Geneva (Switzerland); University of Stavanger, Faculty of Science Technology, Stavanger (Norway); Vuorinen, Aleksi [University of Helsinki, Helsinki Institute of Physics and Department of Physics (Finland)

    2016-03-15

    In this review article, we argue that our current understanding of the thermodynamic properties of cold QCD matter, originating from first principles calculations at high and low densities, can be used to efficiently constrain the macroscopic properties of neutron stars. In particular, we demonstrate that combining state-of-the-art results from Chiral Effective Theory and perturbative QCD with the current bounds on neutron star masses, the Equation of State of neutron star matter can be obtained to an accuracy better than 30% at all densities. (orig.)

  14. The Sun: Our Nearest Star

    Science.gov (United States)

    Adams, M. L.; Six, N. Frank (Technical Monitor)

    2002-01-01

    We have in our celestial backyard, a prime example of a variable star. The Sun, long thought to be "perfect" and unvarying, began to reveal its cycles in the early 1600s as Galileo Galilei and Christoph Scheiner used a telescope to study sunspots. For the past four hundred years, scientists have accumulated data, showing a magnetic cycle that repeats, on average, every eleven (or twenty-two) years. In addition, modern satellites have shown that the energy output at radio and x-ray wavelengths also varies with this cycle. This talk will showcase the Sun as a star and discuss how solar studies may be used to understand other stars.

  15. Neutron Star Physics and EOS

    Directory of Open Access Journals (Sweden)

    Lattimer James M.

    2016-01-01

    Full Text Available Neutron stars are important because measurement of their masses and radii will determine the dense matter equation of state. They will constrain the nuclear matter symmetry energy, which controls the neutron star matter pressure and the interior composition, and will influence the interpretation of nuclear experiments. Astrophysical observations include pulsar timing, X-ray bursts, quiescent low-mass X-ray binaries, pulse profiles from millisecond pulsars, neutrino observations from gravitational collapse supernovae,and gravitational radiation from compact object mergers. These observations will also constrain the neutron star interior, including the properties of superfluidity there, and determine the existence of a possible QCD phase transition.

  16. Top Argelander Stars: Pedagogy & Prize

    CERN Document Server

    Kulkarni, S R

    2016-01-01

    Stellar astronomy, fueled by massive capital investments, advances in numerical modeling and theory, is resurgent and arguably is on the verge of a magnificent renaissance. Powerful time domain optical surveys, both on ground and in space, are producing data on variable stars on an unprecedented industrial scale. Those with deep knowledge of variable stars will stand to benefit from this resurgence. Notwithstanding these developments, in some astronomical communities, classical stellar astronomy has been in the doldrums. I offer a modest proposal to establish a basic level of familiarity with variable stellar phenomenology and an attractive scheme to make research in variable star astronomy visible, alluring and fashionable.

  17. Neutron star structure from QCD

    Science.gov (United States)

    Fraga, Eduardo S.; Kurkela, Aleksi; Vuorinen, Aleksi

    2016-03-01

    In this review article, we argue that our current understanding of the thermodynamic properties of cold QCD matter, originating from first principles calculations at high and low densities, can be used to efficiently constrain the macroscopic properties of neutron stars. In particular, we demonstrate that combining state-of-the-art results from Chiral Effective Theory and perturbative QCD with the current bounds on neutron star masses, the Equation of State of neutron star matter can be obtained to an accuracy better than 30% at all densities.

  18. Neutron star structure from QCD

    CERN Document Server

    Fraga, Eduardo S; Vuorinen, Aleksi

    2016-01-01

    In this review article, we argue that our current understanding of the thermodynamic properties of cold QCD matter, originating from first principles calculations at high and low densities, can be used to efficiently constrain the macroscopic properties of neutron stars. In particular, we demonstrate that combining state-of-the-art results from Chiral Effective Theory and perturbative QCD with the current bounds on neutron star masses, the Equation of State of neutron star matter can be obtained to an accuracy better than 30% at all densities.

  19. New illustrated stars and planets

    CERN Document Server

    Cooper, Chris; Nicolson, Iain; Stott, Carole

    2002-01-01

    Stars & Plantes, written by experts and popular science writers, is a comprehensive overview of our Universe - what is it, where it came from and how we discovered it. This intriguing, information-rich new reference book contains over 300 stunning images from the Hubble Telescope and leading observatories from around the world as well as diagrams to explain the finer points of theory. With extensive sections on everything from the Solar System to how stars form Stars & Planets will appeal to beginners and the serious stargazer alike.

  20. Neutron star moments of inertia

    Science.gov (United States)

    Ravenhall, D. G.; Pethick, C. J.

    1994-01-01

    An approximation for the moment of inertia of a neutron star in terms of only its mass and radius is presented, and insight into it is obtained by examining the behavior of the relativistic structural equations. The approximation is accurate to approximately 10% for a variety of nuclear equations of state, for all except very low mass stars. It is combined with information about the neutron-star crust to obtain a simple expression (again in terms only of mass and radius) for the fractional moment of inertia of the crust.