Pulsations in the late-type Be star HD 50 209 detected by CoRoT
Context: The presence of pulsations in late-type Be stars is still amatter of controversy. It constitutes an important issue to establishthe relationship between non-radial pulsations and the mass-lossmechanism in Be stars. Aims: To contribute to this discussion, weanalyse the photometric time series of the B8IVe star HD 50 209 observedby the CoRoT mission in the seismology field. Methods: We usestandard Fourier techniques and linear and non-linear least squaresfitting methods to analyse the CoRoT light curve. In addition, weapplied detailed modelling of high-resolution spectra to obtain thefundamental physical parameters of the star. Results: We havefound four frequencies which correspond to gravity modes with azimuthalorder m=0,-1,-2,-3 with the same pulsational frequency in theco-rotating frame. We also found a rotational period with a frequency of0.679 cd-1 (7.754 ?Hz). Conclusions: HD 50 209 is apulsating Be star as expected from its position in the HR diagram, closeto the SPB instability strip.Based on observations made with the CoRoT satellite, with FEROS at the2.2 m telescope of the La Silla Observatory under the ESO LargeProgramme LP178.D-0361 and with Narval at the Télescope BernardLyot of the Pic du Midi Observatory. Current address: ValencianInternational University (VIU), José Pradas Gallen s/n, 12006Castellón, Spain. Current address: Laboratoire AIM,CEA/DSM-CNRS-Université Paris Diderot; CEA, IRFU, SAp, centre deSaclay, 91191 Gif-sur-Yvette, France.
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A photometric study of Be stars located in the seismology fields of COROT
Context: In preparation for the COROT mission, an exhaustive photometricstudy of Be stars located in the seismology fields of the mission hasbeen performed. The very precise and long-time-spanned photometricobservations gathered by the COROT satellite will give important clueson the origin of the Be phenomenon. Aims: The aim of this work is tofind short-period variable Be stars located in the seismology fields ofCOROT, and to study and characterise their pulsational properties. Methods: Light curves obtained at the Observatorio de Sierra Nevada,together with data from Hipparcos and ASAS-3 for a total of 84 Be stars,were analysed in order to search for short-term variations. We appliedstandard Fourier techniques and non-linear least-square fitting to thetime series. Results: We found 7 multiperiodic, 21 mono-periodic and 26non-variable Be stars. Short-term variability was detected in 74% ofearly-type Be stars and in 31% of mid- to late-type Be stars. We showthat non-radial pulsations are more frequent among Be stars than inslow-rotating B stars of the same spectral range.Appendix A is only available in electronic form at http://www.aanda.org
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A WFI survey in the Chamaeleon II dark cloud
Aims.We present the results of an optical multi-band survey for low-masspre-main sequence (PMS) stars and young brown dwarfs (BDs) in theChamaeleon II (Cha II) dark cloud. This surveyconstitutes the complementary optical data to the c2d Spitzer Legacysurvey in Cha II. Methods: Using the wide-fieldimager (WFI) at the ESO 2.2 m telescope, we surveyed a sky area of about1.75 square degrees in Cha II. The region wasobserved in the R_c, I_c, and z broad-bands, in Hα and in twomedium-band filters centred at 856 and 914 nm. We selected PMS star andyoung BD candidates using colour-magnitude diagrams (CMDs) andtheoretical isochrones reproduced ad-hoc for the WFI at the ESO2.2mtelescope system. We reinforced the selection criteria by using thepreviously known PMS stars in Cha II to define thePMS locus on the CMDs and by investigating the infrared (IR) colours ofthe candidates. By exploiting the WFI intermediate-band photometry wealso estimated the effective temperature and the level of Hαemission of the candidates. Results: Our survey, which is one of thelargest and deepest optical surveys conducted so far in ChaII, recovered the majority of the PMS stars and 10 membercandidates of the cloud from previous IR surveys. In addition, thesurvey revealed 10 new potential members. From our photometriccharacterisation, we estimate that some 50% of the 20 candidates willresult in true Cha II members. Based on ourtemperature estimates, we conclude that several of these objects areexpected to be sub-stellar and give a first estimate of the fraction ofsub-stellar objects.Based on observations carried out at the European Southern Observatory,La Silla, Chile under proposals numbers 67.C-0225 and 68.C-0311.Appendices and Fig. 14 are only available in electronic form athttp://www.aanda.org Table 7 is available in electronic form athttp://www.aanda.org and at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/470/281
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CoRoT and asteroseismology. . Preparatory work and simultaneous ground-based monitoring
The successful launch of the CoRoT (COnvection, ROtation and planetaryTransits) satellite opens a new era in asteroseismology. The spacephotometry is complemented by high-resolution spectroscopy andmulticolour photometry from ground, to disclose the pulsational contentof the asteroseismic targets in the most complete way. Some preliminaryresults obtained with both types of data are presented.
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Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
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Spectroscopic analysis of southern B and Be stars
Spectroscopic monitoring of 141 southern field B-type stars, 114 of themknown to exhibit the Be phenomenon, allowed the estimation of theirprojected rotational velocities, effective temperatures and superficialgravities from both line and equivalent width fitting procedures.Stellar ages, masses and bolometric luminosities were derived frominternal structure models. Without taking into account the effects ofgravity darkening, we note the occurrence of the Be phenomenon in laterstages of main-sequence phase.
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Fundamental parameters of Be stars located in the seismology fields of COROT
In preparation for the COROT space mission, we determined thefundamental parameters (spectral type, temperature, gravity, V sin i) ofthe Be stars observable by COROT in its seismology fields (64 Be stars).We applied a careful and detailed modeling of the stellar spectra,taking into account the veiling caused by the envelope, as well as thegravitational darkening and stellar flattening due to rapid rotation.Evolutionary tracks for fast rotators were used to derive stellar massesand ages. The derived parameters will be used to select Be stars assecondary targets (i.e. observed for 5 consecutive months) and short-runtargets of the COROT mission. Furthermore, we note that the main part ofour stellar sample falls in the second half of the main sequence lifetime, and that in most cases the luminosity class of Be stars isinaccurate in characterizing their evolutionary status.
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An Atlas of Spectrophotometric Landolt Standard Stars
We present CCD observations of 102 Landolt standard stars obtained withthe Ritchey-Chrétien spectrograph on the Cerro TololoInter-American Observatory 1.5 m telescope. Using stellar atmospheremodels, we have extended the flux points to our six spectrophotometricsecondary standards, in both the blue and the red, allowing us toproduce flux-calibrated spectra that span a wavelength range from 3050Å to 1.1 μm. Mean differences between UBVRI spectrophotometrycomputed using Bessell's standard passbands and Landolt's publishedphotometry were determined to be 1% or less. Observers in bothhemispheres will find these spectra useful for flux-calibrating spectra,and through the use of accurately constructed instrumental passbands,will be able to compute accurate corrections to bring instrumentalmagnitudes to any desired standard photometric system (S-corrections).In addition, by combining empirical and modeled spectra of the Sun,Sirius, and Vega, we calculate and compare synthetic photometry toobserved photometry taken from the literature for these three stars.
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Physical Parameters of Southern B- and Be-Type Stars
In this paper we present new results on stellar fundamental parametersfor early B and Be field stars observed in the southern hemisphere:effective temperature, superficial gravity, and projected stellarrotation velocity. The estimation of their projected rotation velocitiesis made by two successive methods. We first obtain an initial valuebased on Fourier transforms of the He I λ4471 line for 34 B andBe field stars with magnitudes in the range0.5<=mv<=10, followed by a more accurate fittingprocedure of observed lines with non-LTE model line profiles. Thisprocedure yields stellar rotation velocity estimates that are inagreement with those of the literature. We derive also Teffand logg values by fitting equivalent widths and profiles of NLTE modelspectra to the observed ones. Finally, we give estimates of stellarages, masses, and bolometric luminosities derived from interpolations inthe evolutionary tracks calculated by Schaller.
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A Search for High-Velocity Be Stars
We present an analysis of the kinematics of Be stars based uponHipparcos proper motions and published radial velocities. We findapproximately 23 of the 344 stars in our sample have peculiar spacemotions greater than 40 km s-1 and up to 102 kms-1. We argue that these high-velocity stars are the resultof either a supernova that disrupted a binary or ejection by closeencounters of binaries in young clusters. Be stars spun up by binarymass transfer will appear as high-velocity objects if there wassignificant mass loss during the supernova explosion of the initiallymore massive star, but the generally moderate peculiar velocities of BeX-ray binaries indicate that the progenitors lose most of their massprior to the supernova (in accordance with model predictions). Binaryformation models for Be stars predict that most systems bypass thesupernova stage (and do not receive runaway velocities) to createultimately Be+white dwarf binaries. The fraction of Be stars spun up bybinary mass transfer remains unknown, since the post-mass transfercompanions are difficult to detect.
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A representative sample of Be stars. II. K band spectroscopy
We present K band (2.05 mu m - 2.22 mu m) spectra of 66 isolated Bestars of spectral types O9-B9 and luminosity classes III, IV & V. Wefind that objects with He i features either in emission or absorptionare B3 or earlier. Objects with Mg ii emission but no He i are B2 to B4,while objects with Brgamma emission but no evidence of He i or Mg ii areB5 or later. Na i emission in the spectra of 4 objects appears toindicate that regions of the circumstellar envelopes of these stars mustbe shielded from direct stellar radiation. Systematic trends in the linestrength and profile of Brgamma are seen from early to late spectraltypes which can be understood in terms of differences in the disctemperature and density. 30 percent of the stars do not currently showevidence for line emission. Compared to the emission line stars theseobjects have a significantly lower mean rotational velocity and adistribution of spectral types that is significantly earlier. This canbe explained either as the original misidentification of these objectsas Be stars (i.e. they never had line emission), or as evidence thatstars with lower rotational velocities may be more prone to changesbetween the Be and B phases.
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Catalogue of H-alpha emission stars in the Northern Milky Way
The ``Catalogue of Stars in the Northern Milky Way Having H-alpha inEmission" appears in Abhandlungen aus der Hamburger Sternwarte, Band XIin the year 1997. It contains 4174 stars, range {32degr <= l() II< 214degr , -10degr < b() II < +10degr } having the Hαline in emission. HBH stars and stars of further 99 lists taken from theliterature till the end of 1994 were included in the catalogue. We givethe cross-identification of stars from all lists used. The catalogue isalso available in the Centre de Données, Strasbourg ftp130.79.128.5 or http://cdsweb.u-strasbg.fr and at the HamburgObservatory via internet.
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Catalogue of stars in the northern Milky Way having H-alpha in emission
Not Available
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Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
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UBV(RI)c photometry of equatorial standard stars - A direct comparison between the northern and southern systems
UBV(RI)c photometry of 212 stars from Landolt's list of equatorialstandards is presented. The observations are tied to the system definedby Cousin's E-region standards. A comparison of the present results withLandolt's reveals reasonably good agreement for (V-R)c and (V-I)c, butmarked systematic differences for (B-V) and (U-B). The UBV systems ofCousins and Landolt are evidently not the same and both probably differfrom Johnson's original system.
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UBVRI photometric standard stars around the celestial equator
It is pointed out that accurate, internally consistent, and readilyaccessible standard star photometric sequences are necessary for thecalibration of the intensity and color data which astronomers obtain atthe telescope. The photometric results provided in connection with thepresent study represent the first part of an effort which is concernedwith the presentation of UBVRI photoelectric photometric standard starsin the magnitude range from 7 to 17 over as broad a range in color aspossible. All of the photometric observations were made with a 31034type photomultiplier used in a pulse counting mode. Some 15 to 25standard stars chosen from Cousins' lists (1973, 1976) in the E-regionswere observed with an 0.4-m telescope each night along with the programstars. UBVRI standard stars were observed periodically throughout thenight. Observations with a 0.9-m telescope were also conducted. TheUBVRI photoelectric observations take into account 223 stars.
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A Catalogue of Be-Stars
Not Available
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Spectral classifications for Landolt's celestial equatorial standard stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979AJ.....84..783D&db_key=AST
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Equatorial UBVRI photoelectric sequences
From 1335 BVRI observations of 189 stars in selected areas 92-115,Landolt's (1973) network of faint UBV standards has been extended to RI. Of these stars, 173 have four or more observations. The (U-B) valuesof Landolt are adopted, and a well-observed equatorial faint-starnetwork is presented on the Johnson UBVRI photometric system.
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Distances to eclipsing binaries. III - Masses, radii, and absolute magnitudes of 96 stars
Distances to, and absolute magnitudes of, 96 components of eclipsingbinaries with well-determined absolute dimensions have been computedusing V-R photometry. The calculations take into account interstellarreddening, which is estimated from existing UBV and uvby-betaphotometry, as well as photometric proximity effects. The resultingabsolute magnitudes, dimensions, and masses are compared with zero-agemain sequences predicted by theory. Theory is in good agreement with theobserved data for stars more massive than the sun if a composition (X,Y, Z) = (0.66 + or - 0.03, 0.303 + or - 0.03, 0.037 + or - 0.005) ischosen. The corresponding helium-to-hydrogen number ratio is 0.115 + or- 0.02, in agreement with previous estimates.
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Photoelektrische Photometrie von Shell-Sternen
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&AS...15..311H&db_key=AST
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Catalog of Indidual Radial Velocities, 0h-12h, Measured by Astronomers of the Mount Wilson Observatory
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJS...19..387A&db_key=AST
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Spectral Classifications of some Emission B Stars
Not Available
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Radial Velocities and Spectral Types for Fourteen Stars
Not Available
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A Spectroscopic and Photometric Study of the be Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1958ApJ...128..207M&db_key=AST
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Stellar Spectra in Milky way Regions. V.A Region in Monoceros.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956ApJS....2..271M&db_key=AST
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Spectroscopic Observations of be Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1951ApJ...113..624M&db_key=AST
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Catalogue and Bibliography of Stars of Classes B and a whose Spectra have Bright Hydrogen Lines
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1933ApJ....78...87M&db_key=AST
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Not Available
Not Available
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INHABITED SKY
