- ID:
- ivo://CDS.VizieR/V/117A
- Title:
- Geneva-Copenhagen Survey of Solar neighbourhood
- Short Name:
- V/117A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (from paper II, 2007) Ages, metallicities, space velocities, and Galactic orbits of stars in the Solar neighbourhood are fundamental observational constraints on models of galactic disk evolution. Understanding and minimising systematic errors and sample selection biases in the data is crucial for their interpretation. We aim to consolidate the calibrations of uvbyb photometry into T_eff_, [Fe/H], distance, and age for F and G stars and rediscuss the results of the Geneva-Copenhagen Survey (GCS, Nordstrom et al., 2004, paper I) in terms of the evolution of the disk. We use recent V-K photometry, angular diameters, high-resolution spectroscopy, Hipparcos parallaxes, and extensive numerical simulations to re-examine and verify the temperature, metallicity, distance, and reddening calibrations for the uvbyb system. We also highlight the selection effects inherent in the apparent-magnitude limited GCS sample. We substantially improve the T_eff_ and [Fe/H] calibrations for early F stars, where spectroscopic temperatures have large systematic errors. A slight offset of the GCS photometry and the non-standard helium abundance of the Hyades invalidate its use for checking metallicity or age scales; however, the distances, reddenings, metallicities, and age scale for GCS field stars require minor corrections only. Our recomputed ages are in excellent agreement with the independent determinations by Takeda et al. (2007ApJS..168..297T), indicating that isochrone ages can now be reliably determined. The revised G-dwarf metallicity distribution remains incompatible with closed-box models, and the age-metallicity relation for the thin disk remains almost flat, with large and real scatter at all ages sigma_intrinsic=0.20 dex). Dynamical heating of the thin disk continues throughout its life; specific in-plane dynamical effects dominate the evolution of the U and V velocities, while the W velocities remain random at all ages. When assigning thick and thin-disk membership for stars from kinematic criteria, parameters for the oldest stars should be used to characterise the thin disk.
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- ID:
- ivo://CDS.VizieR/V/130
- Title:
- Geneva-Copenhagen Survey of Solar neighbourhood III
- Short Name:
- V/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ages, chemical compositions, velocity vectors, and Galactic orbits for stars in the solar neighbourhood are fundamental test data for models of Galactic evolution. The Geneva-Copenhagen Survey of the Solar neighbourhood (Nordstrom et al. 2004A&A...418..989N; GCS), a magnitude-complete, kinematically unbiased sample of 16,682 nearby F and G dwarfs, is the largest available sample with complete data for stars with ages spanning that of the disk. We aim to improve the accuracy of the GCS data by implementing the recent revision of the Hipparcos parallaxes. The new parallaxes yield improved astrometric distances for 12,506 stars in the GCS. We also use the parallaxes to verify the distance calibration for uvbyHbeta photometry by Holmberg et al. (2007A&A...475..519H; GCS II, Cat. VI/117). We add new selection criteria to exclude evolved cool stars giving unreliable results and derive distances for 3,580 stars with large parallax errors or not observed by Hipparcos. We also check the GCS II scales of T_eff_ and [Fe/H] and find no need for change. From the new distances we compute revised Mv, U, V, W, and Galactic orbital parameters for 13,520 GCS stars. We also recompute stellar ages with the new values of Mv from the Padova stellar evolution models used in GCS I-II, and compare them with ages from the Yale-Yonsei and Victoria-Regina models. Finally, we compare the observed age-velocity relation in W with three simulated disk heating scenarios to show the potential of the data. With these revisions, the basic data for the GCS stars should now be as reliable as is possible with existing techniques. Further improvement must await consolidation of the T_eff_ scale from angular diameters and fluxes, and the Gaia trigonometric parallaxes. We discuss the conditions for improving computed stellar ages from new input data, and for distinguishing different disk heating scenarios from data sets of the size and precision of the GCS.
- ID:
- ivo://CDS.VizieR/J/A+A/325/167
- Title:
- Geneva photometry in NGC 6231
- Short Name:
- J/A+A/325/167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photoelectric (127 stars) and CCD (168 stars) Geneva photometry for the very young open cluster NGC 6231. We have searched for new cluster members out to a distance of ~13arcmin, extending the Seggewiss area (~8arcmin), and we found at least 64 new probable members in this extended field. Differential reddening is clearly measured across the cluster area. We determine the cluster distance (1800pc) and age (3.8+/-0.6x10^6^yr). The probable presence of pre-main sequence stars and the consequence of this population on the cluster formation history is analysed. We also found that the O8.5III star S161 is a long term variable and we present its light curve extending over more than 20 years. Finally we discuss the existence of Ap stars in the cluster. For a description of the Geneva photometric system, see e.g. <GCPD/13>
- ID:
- ivo://CDS.VizieR/J/A+A/343/847
- Title:
- Geneva Photometry of Eta Car
- Short Name:
- J/A+A/343/847
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss 24yr of optical photometry of {eta} Carinae, among which new Geneva photometry made between 1994 and 1998. Various conclusions from our previous photometric studies are confirmed. The core hides a normal S Dor variable (or LBV): it shows light variations on a time scale of 1-4yr, with superimposed micro oscillations whose quasi-period indicates a temperature in the order of 22000K. Therefore, a more complicated model for {eta} Car is necessary to explain its extraordinary appearance and phenomena exhibited in the past and at present.
- ID:
- ivo://CDS.VizieR/J/A+A/415/241
- Title:
- Geneva photometry of HD 129929
- Short Name:
- J/A+A/415/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have gathered and analysed a timeseries of 1493 high-quality multicolour Geneva photometric data of the B3V {beta} Cep star Hd 129929. The dataset has a time base of 21.2 years. The occurrence of a beating phenomenon is evident from the data. We find evidence for the presence of at least six frequencies, among which we see components of two frequency multiplets with an average spacing of ~0.0121c/d which points towards very slow rotation. This result is in agreement with new spectroscopic data of the star and also with previously taken UV spectra. We provide the amplitudes of the six frequencies in all seven photometric filters. The metal content of the star is Z=0.018+/-0.004. All these observational results will be used to perform detailed seismic modelling of this massive star in a subsequent paper.
- ID:
- ivo://CDS.VizieR/J/A+A/463/579
- Title:
- Geneva photometry of HD 23642
- Short Name:
- J/A+A/463/579
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HD 23642 is the only known eclipsing binary in the Pleiades, and therefore of importance in determining the distance to this cluster. To use new photometric and spectroscopic data in combination with existing data in the literature in order to improve the determination of the parameters of the system, its distance and reddening. New photometric and spectroscopic data are presented for HD 23642. The spectroscopic data are ``spectrally disentangled'' using the KOREL code. The new and literature photometric and radial velocity data are simultaneously analysed using the FOTEL code to obtain the orbital solution and derive the fundamental parameters of the two stars. The distance and reddening are determined by fitting 7-colour Geneva, B,V and Stroemgren colours, and considering surface-brightness relations for the two components in (B-V) and Stroemgren c_1_-index. The preferred distance is 138.0+/-1.5pc for a reddening of E(B-V)=0.025+/-0.003. The reddening value is larger than the 0.012 adopted in the recent works on this stars by Munari et al. (2004A&A...418L..31M) and Southworth et al. (2005A&A...429..645S), and smaller than other values in the literature for the cluster reddening. The distance is in agreement with other recent works on the distance to the Pleiades. A comparison with evolutionary models suggests that the inclusion of convective core overshoot gives a much better fit to the empirical mass-radius relationship obtained from the binary analysis. Both this comparison and the "spectral disentangling" are consistent with HD 23642 having [Fe/H]=+0.06, a value determined by the most recent spectroscopical analyses of Pleiades stars.
- ID:
- ivo://CDS.VizieR/J/A+A/364/689
- Title:
- Geneva photometry of HDE 318107
- Short Name:
- J/A+A/364/689
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The rotation period of the Ap star HDE 318107 has been determined from magnetic and photometric observations obtained between August 1992 and September 1998
- ID:
- ivo://CDS.VizieR/J/A+A/311/873
- Title:
- Geneva Photometry of HD 34798 & HD 45284
- Short Name:
- J/A+A/311/873
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the period analysis of two variable mid-B stars that have been observed in the Geneva photometric system between 1981 and 1990. Both HD 34798 and HD 45284 are multiperiodic g-mode pulsators that belong to the group of slowly pulsating B stars. The power spectrum of HD 34798 is characterized by several modes which have about equal power. This star belongs to a visual binary, the other component of which is a singly periodical CP star. Quasi-simultaneous observations of both stars are discussed and turn out to be helpful to illustrate the multiperiodic behavior of HD 34798. Three oscillation modes with a nearly stable amplitude are found; the remaining variability may be due to two very close oscillation modes, or, alternatively, to one mode with an intrinsically variable amplitude. Three oscillation frequencies can be distinguished clearly in the power spectrum of HD 45284. The beat periods for this star are the shortest for any SPB detected so far, and therefore make HD 45284 an excellent candidate for verification of our results and for asteroseimological follow-up.
- ID:
- ivo://CDS.VizieR/J/A+A/341/469
- Title:
- Geneva photometry of NGC 2451 and HR 2968
- Short Name:
- J/A+A/341/469
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The two clusters NGC 2451 A and B will be examined on the basis of Geneva multicolour photometric measurements. P and Q are the sum of the individual weights divided by 3 for the colours and the V magnitude respectively. For a description of the Geneva photometric system, see e.g. <GCPD/13>
- ID:
- ivo://CDS.VizieR/J/A+AS/132/367
- Title:
- Geneva photometry of the Algol system TZ Eri
- Short Name:
- J/A+AS/132/367
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Light curves of the semi-detached eclipsing binary system TZ Eridan in the Geneva 7-colour photometric system were analysed using the Wilson-Devinney programme. The physical and orbital parameters have been determined through a self-consistent simultaneous solution of the seven light curves and of the radial velocity curves of both components.
