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1271. Gaia's DR1 parallaxes vs previous measurements
ID:
ivo://CDS.VizieR/J/ApJ/832/L18
Title:
Gaia's DR1 parallaxes vs previous measurements
Short Name:
J/ApJ/832/L18
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use 612 single stars with previously published trigonometric parallaxes placing them within 25pc to evaluate parallaxes released in Gaia's first data release (DR1). We find that the Gaia parallaxes are, on average, 0.24+/-0.02mas smaller than the weighted mean trigonometric parallax values for these stars in the solar neighborhood. We also find that the offset changes with distance out to 100pc, in the sense that the closer the star, the larger the offset. We find no systematic trends in the parallax offsets with stellar V magnitude, V-K color, or proper motion. We do find that the offset is roughly twice as large for stars south of the ecliptic compared to those that are north.
1272. Gaia SPSS variability monitoring
ID:
ivo://CDS.VizieR/J/MNRAS/462/3616
Title:
Gaia SPSS variability monitoring
Short Name:
J/MNRAS/462/3616
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of the short-term constancy monitoring of candidate Gaia Spectrophotometric Standard Stars (SPSS). We obtained time series of typically 1.24 hour - with sampling periods from 1-3 min to a few hours, depending on the case - to monitor the constancy of our candidate SPSS down to 10mmag, as required for the calibration of Gaia photometric data. We monitored 162 out of a total of 212 SPSS candidates. The observing campaign started in 2006 and finished in 2015, using 143 observing nights on nine different instruments covering both hemispheres. Using differential photometry techniques, we built light curves with a typical precision of 4 mmag, depending on the data quality. As a result of our constancy assessment, 150 SPSS candidates were validated against short term variability, and only 12 were rejected because of variability including some widely used flux standards such as BD+174708, SA 105-448, 1740346, and HD 37725.
1273. Gaia survey of stars associated with Lupus Clouds
ID:
ivo://CDS.VizieR/J/AJ/160/186
Title:
Gaia survey of stars associated with Lupus Clouds
Short Name:
J/AJ/160/186
Date:
21 Oct 2021
Publisher:
CDS
Description:
I have used high-precision photometry and astrometry from the second data release of the Gaia mission to perform a survey for young stars associated with the Lupus clouds, which have distances of ~160pc and reside within the Scorpius-Centaurus (Sco-Cen) OB association. The Gaia data have made it possible to distinguish Lupus members from most of the stars in other groups in Sco-Cen that overlap with the Lupus clouds, which have contaminated previous surveys. The new catalog of candidate Lupus members should be complete for spectral types earlier than M7 at AK<0.2 within fields encompassing clouds 1-4. I have used that catalog to characterize various aspects of the Lupus stellar population. For instance, the sequence of low- mass stars in Lupus is ~0.4mag brighter than the sequence for Upper Sco, which implies an age of ~6Myr based an adopted age of 10-12Myr for Upper Sco and the change in luminosity with age predicted by evolutionary models. I also find that the initial mass function in Lupus is similar to that in other nearby star-forming regions based on a comparison of their distributions of spectral types.
1274. 632 Gaia Ultracompact Dwarf galaxy candidates
ID:
ivo://CDS.VizieR/J/ApJ/899/140
Title:
632 Gaia Ultracompact Dwarf galaxy candidates
Short Name:
J/ApJ/899/140
Date:
14 Mar 2022 00:54:57
Publisher:
CDS
Description:
Tidally stripped galaxy nuclei and luminous globular clusters (GCs) are important tracers of the halos and assembly histories of nearby galaxies, but are difficult to reliably identify with typical ground-based imaging data. In this paper we present a new method to find these massive star clusters using Gaia DR2, focusing on the massive elliptical galaxy Centaurus A (Cen A). We show that stripped nuclei and GCs are partially resolved by Gaia at the distance of Cen A, showing characteristic astrometric and photometric signatures. We use this selection method to produce a list of 632 new candidate luminous clusters in the halo of Cen A out to a projected radius of 150kpc. Adding in broadband photometry and visual examination improves the accuracy of our classification. In a spectroscopic pilot program we have confirmed five new luminous clusters, which includes the 7th and 10th most luminous GC in Cen A. Three of the newly discovered GCs are further away from Cen A than all previously known GCs. Several of these are compelling candidates for stripped nuclei. We show that our novel Gaia selection method retains at least partial utility out to distances of ~25Mpc and hence is a powerful tool for finding and studying star clusters in the sparse outskirts of galaxies in the local universe.
1275. Gaia white dwarfs within 40pc. II.
ID:
ivo://CDS.VizieR/J/MNRAS/499/1890
Title:
Gaia white dwarfs within 40pc. II.
Short Name:
J/MNRAS/499/1890
Date:
14 Jan 2022 00:10:10
Publisher:
CDS
Description:
We present an overview of the sample of northern hemisphere white dwarfs within 40pc of the Sun detected from Gaia Data Release 2 (DR2). We find that 521 sources are spectroscopically confirmed degenerate stars, 111 of which were first identified as white dwarf candidates from Gaia DR2 and followed-up recently with the William Herschel Telescope and Gran Telescopio Canarias. Three additional white dwarf candidates remain spectroscopically unobserved and six unresolved binaries are known to include a white dwarf but were not in our initial selection in the Gaia DR2 Hertzsprung-Russell diagram (HRD). Atmospheric parameters are calculated from Gaia and Pan-STARRS photometry for all objects in the sample, confirming most of the trends previously observed in the much smaller 20pc sample. Local white dwarfs are overwhelmingly consistent with Galactic disc kinematics, with only four halo candidates. We find that DAZ white dwarfs are significantly less massive than the overall DA population (MDAZ_avg_=0.59M_{sun}_, MDA_avg_=0.66M_{sun}_). It may suggest that planet formation is less efficient at higher mass stars, producing more massive white dwarfs. We detect a sequence of crystallised white dwarfs in the mass range from 0.6<=M/M_{sun}_<=1.0 and find that the vast majority of objects on the sequence have standard kinematic properties that correspond to the average of the sample, suggesting that their nature can be explained by crystallisation alone. We also detect 26 double degenerates and white dwarf components in 56 wide binary systems.
1276. Galactic and LMC Cepheids Fourier parameters
ID:
ivo://CDS.VizieR/J/MNRAS/447/3342
Title:
Galactic and LMC Cepheids Fourier parameters
Short Name:
J/MNRAS/447/3342
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a light-curve analysis of fundamental-mode Galactic and Large Magellanic Cloud (LMC) Cepheids based on the Fourier decomposition technique. We have compiled light-curve data for Galactic and LMC Cepheids in optical (VI), near-infrared (JHKs) and mid-infrared (3.6 and 4.5{mu}m) bands from the literature and determined the variation of their Fourier parameters as a function of period and wavelength. We observed a decrease in Fourier amplitude parameters and an increase in Fourier phase parameters with increasing wavelengths at a given period. We also found a decrease in the skewness and acuteness parameters as a function of wavelength at a fixed period. We applied a binning method to analyse the progression of the mean Fourier parameters with period and wavelength. We found that for periods longer than about 20d, the values of the Fourier amplitude parameters increase sharply for shorter wavelengths as compared to wavelengths longer than the J band. We observed the variation of the Hertzsprung progression with wavelength. The central period of the Hertzsprung progression was found to increase with wavelength in the case of the Fourier amplitude parameters and decrease with increasing wavelength in the case of phase parameters. We also observed a small variation of the central period of the progression between the Galaxy and LMC, presumably related to metallicity effects. These results will provide useful constraints for stellar pulsation codes that incorporate stellar atmosphere models to produce Cepheid light curves in various bands.
1277. Galactic Cepheids BVRI photometry
ID:
ivo://CDS.VizieR/J/A+AS/143/211
Title:
Galactic Cepheids BVRI photometry
Short Name:
J/A+AS/143/211
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report a new version of the catalogue of distances and light-curve parameters for Galactic classical Cepheids. The catalogue lists amplitudes, magnitudes at maximum light, and intensity means for 455 stars in BVRI filters of the Johnson system and (RI)_C_ filters of the Cron-Cousins system. The distances are based on our new multicolour set of Period/Luminosity relations and on our Cepheid-based solution for interstellar extinction law parameters and are referred to an LMC distance modulus of 18.25.
1278. Galactic classical Cepheids Per-Lbol-Rad
ID:
ivo://CDS.VizieR/J/A+A/635/A33
Title:
Galactic classical Cepheids Per-Lbol-Rad
Short Name:
J/A+A/635/A33
Date:
21 Oct 2021
Publisher:
CDS
Description:
Spectral energy distributions (SEDs) were constructed for a sample of 477 classical cepheids (CCs); including stars that have been classified in the literature as such but are probably not. The SEDs were fitted with a dust radiative transfer code. Four stars showed a large mid- or far-infrared excess and the fitting then included a dust component. These comprise the well-known case of RS Pup, and three stars that are (likely) Type-II cepheids (T2Cs), AU Peg, QQ Per, and FQ Lac. The infrared (IR) excess in FQ Lac is reported for the first time in this work. The remainder of the sample was fitted with a stellar photosphere to derive the best-fitting luminosity and effective temperature. Distance and reddening were taken from the literature. The stars were plotted in a Hertzsprung-Russell diagram (HRD) and compared to evolutionary tracks for cepheids and theoretical instability strips. For the large majority of stars, the position in the HRD is consistent with the instability strip for a CC or T2C. About 5% of the stars are outliers in the sense that they are much hotter or cooler than expected. A comparison to effective temperatures derived from spectroscopy suggests in some cases that the photometrically derived temperature is not correct and that this is likely linked to an incorrectly adopted reddening. Two three-dimensional reddening models have been used to derive alternative estimates of the reddening for the sample. There are significant systematic differences between the two estimates with a non-negligible scatter. In this work the presence of a small near-infrared (NIR) excess, as has been proposed in the literature for a few well-known cepheids, is investigated. Firstly, this was done by using a sample of about a dozen stars for which a mid-infrared spectrum is available. This data is particularly con straining as the shape of the observed spectrum should match that of the photosphere and any dust spectrum, both dust continuum and any spectral features of, for example, silicates or aluminium oxide. This comparison provides constraints on the dust composition, in agreement with a previous work in the literature. Secondly, the SEDs of all stars were fitted with a dust model to see if a statistically significant better fit could be obtained. The results were compared to recent work. Eight new candidates for exhibiting a NIR excess are proposed, solely based on the photometric SEDs. Obtaining mid-infrared spectra would be needed to confirm this excess. Finally, period-bolometric luminosity and period-radius relations are presented for samples of over 370 fundamental-mode CCs.
1279. Galactic EB stars with eccentric orbits based on ETDs
ID:
ivo://CDS.VizieR/J/ApJS/235/41
Title:
Galactic EB stars with eccentric orbits based on ETDs
Short Name:
J/ApJS/235/41
Date:
21 Oct 2021
Publisher:
CDS
Description:
A comprehensive catalog of 623 galactic eclipsing binary (EB) systems with eccentric orbits is presented with more than 2830 times of minima determined from the archived photometric data by various sky-survey projects and new photometric measurements. The systems are divided into two groups according to whether the individual system has a GCVS name or not. All the systems in both groups are further classified into three categories (D, A, and A+III) on the basis of their eclipse timing diagrams: 453 D systems showing just constantly displaced secondary minima, 139 A systems displaying only apsidal motion (AM), and 31 A+III systems exhibiting both AM and light-time effects. AM parameters for 170 systems (A and A+III systems) are consistently calculated and cataloged with basic information for all systems. Some important statistics for the AM parameters are discussed and compared with those derived for the eccentric EB systems in the Large and Small Magellanic Clouds.
1280. 5 Galactic GC proper motions from Gaia DR1
ID:
ivo://CDS.VizieR/J/ApJ/839/89
Title:
5 Galactic GC proper motions from Gaia DR1
Short Name:
J/ApJ/839/89
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a pilot study of Galactic globular cluster (GC) proper motion (PM) determinations using Gaia data. We search for GC stars in the Tycho-Gaia Astrometric Solution (TGAS) catalog from Gaia Data Release 1 (DR1), and identify five members of NGC 104 (47 Tucanae), one member of NGC 5272 (M3), five members of NGC 6121 (M4), seven members of NGC 6397, and two members of NGC 6656 (M22). By taking a weighted average of member stars, fully accounting for the correlations between parameters, we estimate the parallax (and, hence, distance) and PM of the GCs. This provides a homogeneous PM study of multiple GCs based on an astrometric catalog with small and well-controlled systematic errors and yields random PM errors similar to existing measurements. Detailed comparison to the available Hubble Space Telescope (HST) measurements generally shows excellent agreement, validating the astrometric quality of both TGAS and HST. By contrast, comparison to ground-based measurements shows that some of those must have systematic errors exceeding the random errors. Our parallax estimates have uncertainties an order of magnitude larger than previous studies, but nevertheless imply distances consistent with previous estimates. By combining our PM measurements with literature positions, distances, and radial velocities, we measure Galactocentric space motions for the clusters and find that these also agree well with previous analyses. Our analysis provides a framework for determining more accurate distances and PMs of Galactic GCs using future Gaia data releases. This will provide crucial constraints on the near end of the cosmic distance ladder and provide accurate GC orbital histories.