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A spectroscopic study of southern (candidate) γ Doradus stars. II. Detailed abundance analysis and fundamental parameters
Context: The γ Doradus stars are a recent class of variable mainsequence F-type stars located on the red edge of the Cepheid instabilitystrip. They pulsate in gravity modes, and this makes them particularlyinteresting for detailed asteroseismic analysis, which can providefundamental knowledge of properties near the convective cores ofintermediate-mass main sequence stars. Aims: To improve currentunderstanding of γ Dor stars through theoretical modelling,additional constraints are needed. Our aim is to estimate thefundamental atmospheric parameters and determine the chemicalcomposition of these stars. Detailed analyses of single stars havepreviously suggested links to Am and λ Boo stars, so we wish toexplore this interesting connection between chemical peculiarity andpulsation. Methods: We analysed a sample of γ Dor stars for thefirst time, including nine bona fide and three candidate members of theclass. We determined the fundamental atmospheric parameters and comparedthe abundance pattern with other A-type stars. We used thesemi-automatic software package VWA for the analysis. This code relieson the calculation of synthetic spectra and thus takes line-blendinginto account. This is important because of the fast rotation in some ofthe sample stars, and we made a thorough analysis of how VWA performswhen increasing v sin i. We obtained good results in agreement withpreviously derived fundamental parameters and abundances in a fewselected reference stars with properties similar to the γ Dorstars. Results: We find that the abundance pattern in the γ Dorstars is not distinct from the constant A- and F-type stars we analysed.Appendices A and B are only available in electronic form athttp://www.aanda.org
| A spectroscopic study of southern (candidate) γ Doradus stars. I. Time series analysis
We present the results of a spectroscopic study of 37 southern(candidate) γ Doradus stars based on échelle spectra. Theobserved spectra were cross-correlated with the standard templatespectrum of an F0-type star for easier detection of binary and intrinsicvariations. We identified 15 objects as spectroscopic binaries,including 7 new ones, while another 3 objects are binary suspects. Atleast 12 objects show composite spectra. We could determine the orbitalparameters for 9 binaries, of which 4 turned out to be ellipsoidalvariables. For 6 binaries, we estimated the expected time-base of theorbital variations. Clear profile variations were observed for 17objects, pointing towards stellar pulsation. For 8 of them, we haveevidence that the main spectroscopic and photometric periods coincide.Our results, in combination with prior knowledge from the literature,lead to the classification of 10 objects as new bona fide γDoradus stars, 1 object as a new bona fide δ Scuti star, and 8objects as constant stars. Finally, we determined the projectedrotational velocity by two independent methods. The resulting v sin ivalues range from 3 to 135 {km s-1}. For the bona fideγ Doradus stars, the majority has v sin i below 60 {kms-1}.
| A catalogue of eclipsing variables
A new catalogue of 6330 eclipsing variable stars is presented. Thecatalogue was developed from the General Catalogue of Variable Stars(GCVS) and its textual remarks by including recently publishedinformation about classification of 843 systems and making correspondingcorrections of GCVS data. The catalogue1 represents thelargest list of eclipsing binaries classified from observations.
| Observational results for northern and southern (candidate) gamma Doradus stars .
We report on observational results obtained for 78 objects originallyclassified as bona-fide or candidate gamma Doradus stars. For thesouthern objects, we gathered echelle spectra with the CORALIEspectrograph attached to the Euler telescope in 1998-2003 and/orJohnson-Cousins B,V,I_c observations with the MODULAR photometerattached to the 0.5-m SAAO telescope in 1999-2000. For the northernobjects, we obtained Geneva U,B,B_1,B_2,V,V_1,G observations with the P7photometer attached to the 1.2-m Mercator telescope in 2001-2004. Atleast 15 of our objects are binaries, of which 7 are new. For 6binaries, we determined the orbit for the first time. At least 17objects show profile variations and at least 12 objects aremultiperiodic photometric variables. Our results allow us to upgrade 11objects to bona-fide gamma Doradus stars and to downgrade 8 objects toconstant up to the current detection limits. Mode identification isstill ongoing, but so far, only ℓ = 1 and 2 modes have beenidentified.
| New uvbybeta photometry of stars of ``astrophysical interest''
Not Available
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| The discovery of new gamma Doradus stars from the HIPPARCOS mission
We present a classification of 39 new variable stars with spectral typebetween A2 and F8 discovered by Hipparcos with the aim to find new gammaDoradus stars. We have used a multivariate classification scheme andreport the discovery of 14 new gamma Doradus variables among thisunbiased sample. Our results point out the biased nature towards hottemperatures of earlier, ground-based surveys of these variables. Thecoolest star among our sample has an effective temperature only slightlyhotter than 6 000 K. For most of the 14 new gamma Doradus stars, we areable to detect more than one period in the Hipparcos light curve. Themultiperiodicity points towards the presence of high-order g-modes. Inview of the lack of a pulsation mechanism for these objects, wedetermine their position in the HR diagram with respect to the deltaScuti stars.
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Osservazione e dati astrometrici
| Costellazione: | Gru |
| Ascensione retta: | 23h06m48.01s |
| Declinazione: | -38°47'38.8" |
| Magnitudine apparente: | 8.71 |
| Distanza: | 141.243 parsec |
| Moto proprio RA: | 1.4 |
| Moto proprio Dec: | -7.3 |
| B-T magnitude: | 9.14 |
| V-T magnitude: | 8.746 |
Cataloghi e designazioni:
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