- 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>
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Search Results
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/454/855
- Title:
- Geneva photometry of W Cru
- Short Name:
- J/A+A/454/855
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Light curves of the long-period Algols are known for their complex (asymmetry in the eclipse, light variations outside the eclipse, changes from cycle-to-cycle), but their interpretation is not possible in the standard model of binary stars. We determined that complex structures present in these active Algol systems could be studied with the eclipse-mapping method that was successfully applied to the new 7-color photometric observations in the Geneva system of W Cru, belonging to the isolated group of these active Algols. Several cycles of this long-period (198.5-days) eclipsing binary were covered by observations. We used a modified Rutten's approach to the eclipse-mapping. The optimization of the system's parameters and the recovery of the disk intensity distribution are performed using a genetic algorithm (GA). The finding of a primary (hot) component is hidden in thick accretion disk confirms previous solutions. The mass of the primary component, M_1_=8.2M_{sun}_, indicates that it is a mid-B type star. The mass-losing component fills its critical lobe, which, for the system's parameters, means it is a G-type supergiant with a mass M_2_=1.6M_{sun}_. The disk is very extended geometrically, and its outer radius is about 80% of the primary's critical lobe. A reconstructed image reveals the rather clumpy and nonuniform brightness distribution of an accretion disk rim in this system that is seen almost edge-on. This clumpiness accounts for light curve distortions and asymmetries, as well as for secular changes.
- ID:
- ivo://CDS.VizieR/J/A+A/449/305
- Title:
- Geneva photometry time series of HD 203664
- Short Name:
- J/A+A/449/305
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We made a seismic study of the young massive beta Cephei star HD 203664 with the goal of constraining its interior structure. Our study is based on a time series of 328 new Geneva 7-colour photometric data of the star spread over 496.8 days. The data confirm the frequency of the dominant mode of the star, which we refined to f_1_=6.02885c/d. The mode has a large amplitude of 37mmag in V and is unambiguously identified as a dipole mode (l=2) from its amplitude ratios and non-adiabatic computations. Besides f_1_, we discovered two additional new frequencies in the star with amplitudes above 4{sigma}: f_2_=6.82902c/d and f_3_=4.81543c/d, or one of their daily aliases. The amplitudes of these two modes are only between 3 and 4mmag, which explains why they were not detected before. Their amplitude ratios are too uncertain for mode identification. We show that the observed oscillation spectrum of HD 203664 is compatible with standard stellar models but that we have insufficient information for asteroseismic inferences. Among the large-amplitude beta Cephei stars, HD 203664 stands out as the only one rotating at a significant fraction of its critical rotation velocity (~40%).
