Multi-site, multi-technique survey of γ Doradus candidates. I. Spectroscopic results for 59 stars
We present the first results of a 2-year high-resolution spectroscopycampaign of 59 candidate γ Doradus stars which were mainlydiscovered from the HIPPARCOS astrometric mission. More than 60% of thestars present line profile variations which can be interpreted as due topulsation related to γ Doradus stars. For all stars we alsoderived the projected rotation velocity (up to more than 200 kms-1). The amplitude ratios 2K/Δ m for the mainHIPPARCOS frequency are in the range 35-96 kms-1,mag-1. About 50% of the candidates arepossible members of binary systems, with 20 stars being confirmedγ Doradus. At least 6 stars present composite spectra, and in allbut one case (for which only one spectrum could be obtained), the narrowcomponent shows line profile variations, pointing towards anuncomfortable situation if this narrow component originates from a shellsurrounding the star. This paper is the first of a series concerningmode identification using both photometric and spectroscopic methods forthe confirmed γ Doradus stars of the present sample.Partially based on observations obtained at the Observatoire deHaute-Provence.
|
A Dozen New γ Doradus Stars
We use new high-dispersion spectroscopic and precise photometricobservations to identify 12 new γ Doradus stars. Two of the 12systems are double-lined binaries that show obvious velocityvariability. Five other stars have metallic lines with compositeprofiles characterized by a narrow feature near the center of each broadcomponent. Spectrograms of the Hα line indicate that all fivestars are binaries rather than shell stars. The remaining five stars inour sample are probably single. All 12 stars are photometricallyvariable with amplitudes between 6 and 87 mmag in Johnson B and periodsbetween 0.3 and 1.2 days. Four stars are monoperiodic; the rest havebetween two and five independent periods. The variability at all periodsapproximates a sinusoid. Although many of the stars lie within theδ Scuti instability strip, none exhibit the higher frequencyvariability seen in δ Scuti stars. We have increased the sample ofknown γ Doradus stars by 40% and revised the positions of a numberof variables in the H-R diagram by accounting for duplicity. Our list of42 confirmed γ Doradus variables gives some of their properties.All are dwarfs or subgiants and lie within a well-defined region of theH-R diagram that overlaps the cool edge of the δ Scuti instabilitystrip. We compare the observed location of the γ Doradus variableswith a recently published theoretical γ Doradus instability stripand find good agreement.
|
Spectroscopy of Early F Stars: γ Doradus Candidates and Possible Metallic Shell Stars
We obtained high-resolution spectroscopic observations of 34 γDoradus candidates. From the red-wavelength spectra, we determinedspectral classes, radial velocities, and projected rotationalvelocities. The spectra of seven late A or early F stars show metalliclines that have composite profiles consisting of a narrow component nearthe center of a broad line, indicating that they may be shell stars orbinaries. Several stars, including HD 152896, HD 173977, HD 175337, andHD 195068/9, show large line profile asymmetries. Two stars, HD 11443(=α Trianguli) and HD 149420, are ellipsoidal variables and notγ Doradus stars. The percentage of binary systems in our samplemay be as high as 74%.
|
Binary Star Orbits. II. Preliminary First Orbits for 117 Systems
Orbital elements are presented for 117 binary systems with no previousorbit calculation. For nearly all of these systems, these elements mustbe regarded as preliminary, but the ephemerides presented here should berelatively accurate over the next several decades. Further, the analysisof these systems should highlight the need for their continuedobservation by dedicated programs to improve the veracity of theseelements.
|
ICCD Speckle Observations of Binary Stars. XXIII. Measurements during 1982-1997 from Six Telescopes, with 14 New Orbits
We present 2017 observations of 1286 binary stars, observed by means ofspeckle interferometry using six telescopes over a 15 year period from1982 April to 1997 June. These measurements constitute the 23dinstallment in CHARA's speckle program at 2 to 4 m class telescopes andinclude the second major collection of measurements from the MountWilson 100 inch (2.5 m) Hooker Telescope. Orbital elements are alsopresented for 14 systems, seven of which have had no previouslypublished orbital analyses.
|
Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
|
The domain of γ Doradus variables in the Hertzsprung-Russell diagram
70 new γ Doradus candidates were identified from Hipparcosphotometry, which represents more than a doubling of the presently knownnumber. Selecting the objects with good evidence for multiperiodicity,it is found that these stars, together with bona fide members of theclass, occupy a well-defined region in a colour-magnitude diagram. Thisdomain corresponds to a range of 7200-7700K on the zero-age mainsequence (ZAMS) and 6900-7500K one magnitude above it, which partlyoverlaps with the instability strip of δ Scuti stars. For thefirst time, γ Doradus stars can be discussed as a group. They canbe found over a significant fraction of the main sequence lifetimes forobjects in the relevant temperature range. An upper limit on the surfacemetallicity of γ Doradus stars is apparent, which may guide thesearch for their pulsation driving mechanism. The importance of possibleobjects exhibiting both γ Doradus and δ Scuti-typepulsations is discussed.
|
Micrometer Measures of Double Stars
Micrometer measures of 795 double stars made with the 26 inch (0.66 m)refractor of the US Naval Observatory from 1984 to 1990 are presented.
|
True and Possible Contact Binaries in the Hipparcos Catalogue
A comprehensive list of contact binaries included in the HIPPARCOScatalogue is given.
|
ICCD Speckle Observations of Binary Stars. XVII. Measurements During 1993-1995 From the Mount Wilson 2.5-M Telescope.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.1639H&db_key=AST
|
Observations of Double Stars and New Pairs. XVII.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..105..475H&db_key=AST
|
New optical positions and proper motions of late type stars associated with SiO masers
The 33 cm astrograph of the Bordeaux Observatory has been used to derivewith respect to AGK3 reference stars, accurate positions of late typevariable stars variable stars associated with strong SiO maser emission.It is suggested that selected maser stars can be used to link theHIPPARCOS system and the VLBI extragalactic reference frame. The propermotions of the program (SiO) and reference stars are derived and, forthe program stars, are compared to the McCormick catalog of propermotions.
|
Micrometer Observations of Double Stars and New Pairs - Part Ten
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980ApJS...44..111H&db_key=AST
|
Micrometer observations of double stars.8.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975ApJS...29..315H&db_key=AST
|
Mesures d'étoiles doubles faites au 0,38 m de l'Observatoire de Paris.
Not Available
|
Mesures d'étoiles doubles faites à l'Observatoire de Paris
Not Available
|
INHABITED SKY
