- ID:
- ivo://CDS.VizieR/J/AJ/131/431
- Title:
- Abundances of Galactic G dwarfs
- Short Name:
- J/AJ/131/431
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied 23 long-lived G dwarfs that belong to the thin disk and thick disk stellar populations. The stellar data and analyses are identical, reducing the chances for systematic errors in the comparisons of the chemical abundance patterns in the two populations. Abundances have been derived for 24 elements: O, Na, Mg, Al, Si, Ca, Ti, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, and Eu.
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- ID:
- ivo://CDS.VizieR/J/A+A/554/A16
- Title:
- Age and metallicity relation in MC clusters
- Short Name:
- J/A+A/554/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study small open star clusters, using Stroemgren photometry to investigate a possible dependence between age and metallicity in the Magellanic Clouds (MCs). Our goals are to trace evidence of an age metallicity relation (AMR) and correlate it with the mutual interactions of the two MCs and to correlate the AMR with the spatial distribution of the clusters. In the Large Magellanic Cloud (LMC), the majority of the selected clusters are young (up to 1Gyr), and we search for an AMR at this epoch, which has not been much studied. We report results for 15 LMC and 8 Small Magellanic Cloud (SMC) clusters, scattered all over the area of these galaxies, to cover a wide spatial distribution and metallicity range. The selected LMC clusters were observed with the 1.54m Danish Telescope in Chile, using the Danish Faint Object Spectrograph and Camera (DFOSC) with a single 2kx2k CCD. The SMC clusters were observed with the ESO 3.6m Telescope, also in Chile, using the ESO Faint Object Spectrograph and Camera (EFOSC). The obtained frames were analysed with the conventional DAOPHOT and IRAF software. We used Stroemgren filters in order to achieve reliable metallicities from photometry. Isochrone fitting was used to determine the ages and metallicities. The AMR for the LMC displays a metallicity gradient, with higher metallicities for the younger ages. The AMR for LMC-SMC star clusters shows a possible jump in metallicity and a considerable increase at about 6x10^8^yr. It is possible that this is connected to the latest LMC-SMC interaction. The AMR for the LMC also displays a metallicity gradient with distance from the centre. The metallicities in SMC are lower, as expected for a metal-poor host galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/409/1037
- Title:
- AK Sco ubvy and Geneva differential photometry
- Short Name:
- J/A+A/409/1037
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of 32 high-resolution echelle spectra of the pre-main sequence spectroscopic binary AK Sco obtained during 1998 and 2000, as well as a total of 72 photoelectric radial-velocity observations from the period 1986-1994. These data allow considerable improvement of the period and other orbital parameters of AK Sco. Our analysis also includes eight series of photometric observations in the uvby and Geneva seven-color systems from 1987, 1989, 1990, 1992, 1994 and 1997.
- ID:
- ivo://CDS.VizieR/J/PASP/105/36
- Title:
- All-sky uvby photometry of speckle binaries
- Short Name:
- J/PASP/105/36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- All-sky Stroemgren photometric observations were obtained for 303 speckle binaries. Most stars were in the range of V = 5 to 8.These data, when combined with ratios of intensities from the CHARA speckle photometry program, will allow the determination of photometric indices for the individual components of binary stars with separations as small as 0.05 arcsec. These photometric indices will complement the stellar masses from the speckle interferometry observations to provide a much improved mass-luminosity relationship.
- ID:
- ivo://CDS.VizieR/J/A+AS/109/425
- Title:
- AO Vel four-colour photometry
- Short Name:
- J/A+AS/109/425
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/AJ/131/1184
- Title:
- A recalibration of optical photometry
- Short Name:
- J/AJ/131/1184
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I use high-quality Hubble Space Telescope (HST) spectrophotometry to analyze the calibration of three popular optical photometry systems: Tycho-2 B_T_ and V_T_, Stromgren uvby, and Johnson UBV.
- ID:
- ivo://CDS.VizieR/J/ApJ/804/146
- Title:
- Atmospheric parameters for nearby B-F stars
- Short Name:
- J/ApJ/804/146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Age determination is undertaken for nearby early type (BAF) stars, which constitute attractive targets for high-contrast debris disk and planet imaging surveys. Our analysis sequence consists of acquisition of ubvy{beta} photometry from catalogs, correction for the effects of extinction, interpolation of the photometry onto model atmosphere grids from which atmospheric parameters are determined, and finally, comparison to the theoretical isochrones from pre-main sequence through post-main sequence stellar evolution models, accounting for the effects of stellar rotation. We calibrate and validate our methods at the atmospheric parameter stage by comparing our results to fundamentally determined T_eff_ and log g values. We validate and test our methods at the evolutionary model stage by comparing our results on ages to the accepted ages of several benchmark open clusters (IC2602, {alpha} Persei, Pleiades, Hyades). Finally, we apply our methods to estimate stellar ages for 3493 field stars, including several with directly imaged exoplanet candidates.
- ID:
- ivo://CDS.VizieR/J/ApJ/484/394
- Title:
- AX Mon photometry and UV spectra
- Short Name:
- J/ApJ/484/394
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- AX Monocerotis is a 232d, noneclipsing, interacting binary star that consists of a K giant, a Be-like giant, and a large amounts of circumstellar material. The K star is almost certainly a synchronous rotator and is probably in contact with its critical lobe. The Be star was believed to be a rapid rotator based on extremely wide absorption lines, but new spectra show that these lines arise from the circumstellar environment. Hydrogen emission, also circumstellar, is many times stronger than the continuum. Near-ultraviolet light curves exhibit a 0.5 mag dip near phase 0.75, but there is no such variability at longer wavelengths. Gas flow trajectories from the cusp of the K star toward the Be star provide a simple explanation for the photometric and spectroscopic behavior. We may have found a decreasing orbital period, but more data are necessary to confirm this result. We present several models for AX Mon based on (1) new and archival visible photometry, (2) archival ultraviolet spectroscopy, (3) new and archival visible spectroscopy, (4) new visible polarimetry, and (5) new radio photometry. Further observations, including optical interferometry, are proposed.
- ID:
- ivo://CDS.VizieR/J/A+AS/119/271
- Title:
- Be stars uvby{beta} photometry
- Short Name:
- J/A+AS/119/271
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present uvby{beta} photometry for Be stars in eight open clusters and two OB associations. It is shown that Be stars occupy anomalous positions in the photometric diagrams, which can be explained in terms of the circumstellar continuum radiation contribution to the photometric indices. In the (b-y)_0_-M_V_ plane Be stars appear redder than the non emission B stars, due to the additional reddening caused by the hydrogen free-bound and free-free recombination in the circumstellar envelope. In the c_0_-M_V_ plane the earlier Be stars present lower c_0_ values than absorption-line B stars, which is caused by emission in the Balmer discontinuity, while the later Be stars deviate towards higher c_0_ values, indicating absorption in the Balmer discontinuity of circumstellar origin.
- ID:
- ivo://CDS.VizieR/J/A+A/362/673
- Title:
- BF Aur UBV photometry
- Short Name:
- J/A+A/362/673
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Because the question of the mass ratio of the early-type system BF Aur has not yet fully been clarified, we present and analyse new UBV photometry and nearly contemporaneous radial velocity observations. From a simultaneous least squares analysis of the photometric light curves and the new radial velocity curves we derive a mass ratio of q=1.048+/-0.02. With even much more accurate photometric and spectroscopic data the mass ratio remains weakly defined. The resulting stellar parameters are consistent with the line ratios derived from old and our new spectra and available Stroemgren indices. We confirm earlier conclusions that BF Aur is detached and that the more massive component is almost filling its Roche lobe. New data indicating a period change support the interpretation that mass exchange has already started or is about to start.
