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Photometry and Spectroscopy of 11 γ Doradus Stars
We have used precise photometric and high-dispersion spectroscopicobservations to study 11 γ Doradus stars, 10 of them newlyconfirmed. Only five of these 11 γ Doradus stars appear to besingle; two are primaries of double-lined spectroscopic binaries, one isthe secondary of a double-lined binary, two are primaries of visualbinaries and, in the case of the double-lined binary (HD 86371), eitheror both components could be a pulsating γ Doradus star. We havedetermined a preliminary orbital period of 5.32 days for thedouble-lined binary HD 41547. Several of the stars show spectroscopicline-profile and low-amplitude radial velocity variability indicative ofpulsation. All 11 stars are photometrically variable with amplitudesbetween 4 and 94 mmag in Johnson B and periods between 0.38 and 1.86days. The 11 stars have between two and five independent periods. Thevariability at all periods approximates a sinusoid. We provide a newtabulation of all 66 γ Doradus stars confirmed to date and listsome of their properties. All are dwarfs or subgiants and lie within awell-defined region of the H-R diagram that overlaps the cool edge ofthe δ Scuti instability strip. Four of the new γ Doradusvariables from this paper also lie within the δ Scuti instabilitystrip but do not exhibit the additional higher frequency variabilitytypical of δ Scuti stars. Among the 66 confirmed γ Doradusvariables, we find no correlation between the period of the strongestpulsation mode and the (B-V) color index, absolute magnitude, orluminosity.
| 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%.
| New uvbybeta photometry of stars of ``astrophysical interest''
Not Available
| 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.
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| קבוצת-כוכבים: | נשר |
| התרוממות ימנית: | 19h50m24.99s |
| סירוב: | +14°30'49.9" |
| גודל גלוי: | 7.958 |
| מרחק: | 105.374 פארסק |
| תנועה נכונה: | 20.3 |
| תנועה נכונה: | -4.7 |
| B-T magnitude: | 8.325 |
| V-T magnitude: | 7.989 |
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