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16711. Variable Stars in the Sculptor dwarf galaxy
ID:
ivo://CDS.VizieR/J/A+AS/112/407
Title:
Variable Stars in the Sculptor dwarf galaxy
Short Name:
J/A+AS/112/407
Date:
21 Oct 2021
Publisher:
CDS
Description:
The central area of the Sculptor dwarf galaxy was surveyed for variable stars as a side-program of the OGLE project. Light curves in the V band were obtained for 226 RR Lyr stars and for 3 anomalous cepheids. The data on RR Lyr variables in four nearby dwarf galaxies are summarized and discussed briefly.
16712. Variable stars in the SMCNOD
ID:
ivo://CDS.VizieR/J/MNRAS/480/669
Title:
Variable stars in the SMCNOD
Short Name:
J/MNRAS/480/669
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of a recently discovered stellar overdensity near the northern edge of the Small Magellanic Cloud (SMCNOD). We exploited variable stars from the fourth release of the Optical Gravitational Lensing Experiment. We used mainly pulsating variable stars and investigated their potential association with the SMCNOD using their spatial distribution and distances. We found four rather spatially concentrated anomalous Cepheids and eight evenly dispersed RR Lyrae stars to be most likely members of this overdensity. The anomalous Cepheids inside the SMCNOD trace possible intermediate-age population with ages ranging between 2 and 4.5Gyr. The age distribution of anomalous Cepheids seems to be in a good agreement with the age distribution of anomalous Cepheids in the SMC. Using empirical relations for RR Lyrae stars, we determined the median metallicity for a possible old population in the SMCNOD to be [Fe/H]_SMCNOD_=-1.71+/-0.21dex, which is in agreement with median metallicity of the old SMC population. The density profile for anomalous Cepheids shows a small anomaly at the position of the SMCNOD, on the other hand, RR Lyrae variables show no such deviation. The probability of finding the observed number of variable stars at the location of the SMCNOD by chance is very low for anomalous Cepheids (0.7 per cent) but high for RR Lyrae stars (13.0 per cent). Based on its variable stars content, we thus confirm the presence of a modest overdensity in intermediate-age stars in the SMCNOD and conclude that it probably has its origin in the SMC rather than to be the remnant of an accreted dwarf galaxy.
16713. Variable stars in 47 Tuc fields 104A-E
ID:
ivo://CDS.VizieR/J/A+AS/128/19
Title:
Variable stars in 47 Tuc fields 104A-E
Short Name:
J/A+AS/128/19
Date:
21 Oct 2021
Publisher:
CDS
Description:
CCD photometry for 42 variables from the field of 47 Tuc = NGC 104 is presented. VI photometry for a large set of stars from the surveyed fields is also given.
16714. Variable stars in VVV globulars. II.
ID:
ivo://CDS.VizieR/J/A+A/651/A47
Title:
Variable stars in VVV globulars. II.
Short Name:
J/A+A/651/A47
Date:
22 Feb 2022
Publisher:
CDS
Description:
The Galactic globular clusters (GGCs) located in the inner regions of the Milky Way suffer from high extinction that makes their observation challenging. High densities of field stars in their surroundings complicate their study even more. The VISTA Variables in the Via Lactea (VVV) survey provides a way to explore these GGCs in the near-infrared where extinction effects are highly diminished. We conduct a search for variable stars in several inner GGCs, taking advantage of the unique multi-epoch, wide-field, near-infrared photometry provided by the VVV survey. We are especially interested in detecting classical pulsators that will help us constrain the physical parameters of these GGCs. In this paper, the second of a series, we focus on NGC 6656 (M 22), NGC 6626 (M 28), NGC 6569, and NGC 6441; these four massive GGCs have known variable sources, but quite different metallicities. We also revisit 2MASS-GC 02 and Terzan 10, the two GGCs studied in the first paper of this series. We present an improved method and a new parameter that efficiently identify variable candidates in the GGCs. We also use the proper motions of those detected variable candidates and their positions in the sky and in the color-magnitude diagrams to assign membership to the GGCs. We identify and parametrize in the near-infrared numerous variable sources in the studied GGCs, cataloging tens of previously undetected variable stars. We recover many known classical pulsators in these clusters, including the vast majority of their fundamental mode RR Lyrae. We use these pulsators to obtain distances and extinctions toward these objects. Recalibrated period-luminosity-metallicity relations for the RR Lyrae bring the distances to these GGCs to a closer agreement with those reported by Gaia, except for NGC 6441, which is an uncommon Oosterhoff III GGC. Recovered proper motions for these GGCs also agree with those reported by Gaia, except for 2MASS-GC 02, the most reddened GGC in our sample, where the VVV near-infrared measurements provide a more accurate determination of its proper motions.
16715. Variable stars of Draco dSph
ID:
ivo://CDS.VizieR/J/AJ/136/1921
Title:
Variable stars of Draco dSph
Short Name:
J/AJ/136/1921
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a CCD survey of variable stars in the Draco dwarf spheroidal galaxy. This survey, which has the largest areal coverage since the original variable star survey by Baade & Swope (1961AJ.....66..300B), includes photometry for 270 RR Lyrae (RRL) stars, 9 anomalous Cepheids (ACs), 2 eclipsing binaries, and 12 slow, irregular red variables, as well as 30 background QSOs. Twenty-six probable double-mode RRL stars were identified. Observed parameters, including mean V and I magnitudes, V amplitudes, and periods, have been derived.
16716. Variable stars photometry from Dome A
ID:
ivo://CDS.VizieR/J/AJ/142/155
Title:
Variable stars photometry from Dome A
Short Name:
J/AJ/142/155
Date:
21 Oct 2021
Publisher:
CDS
Description:
Dome A on the Antarctic plateau is likely one of the best observing sites on Earth thanks to the excellent atmospheric conditions present at the site during the long polar winter night. We present high-cadence time-series aperture photometry of 10000 stars with i<14.5mag located in a 23deg^2^ region centered on the south celestial pole. The photometry was obtained with one of the CSTAR telescopes during 128 days of the 2008 Antarctic winter. We used this photometric data set to derive site statistics for Dome A and to search for variable stars. Thanks to the nearly uninterrupted synoptic coverage, we found six times as many variables as previous surveys with similar magnitude limits. We detected 157 variable stars, of which 55% were unclassified, 27% were likely binaries, and 17% were likely pulsating stars. The latter category includes {delta} Scuti, {gamma} Doradus, and RR Lyrae variables. One variable may be a transiting exoplanet.
16717. Variable young stars photometry
ID:
ivo://CDS.VizieR/J/MNRAS/478/5091
Title:
Variable young stars photometry
Short Name:
J/MNRAS/478/5091
Date:
10 Dec 2021 13:53:12
Publisher:
CDS
Description:
Variability in young stellar objects (YSOs) is one of their primary characteristics. Long-term, multifilter, high-cadence monitoring of large YSO samples is the key to understand the partly unusual light curves that many of these objects show. Here we introduce and present the first results of the HOYS-CAPS citizen science project that aims to perform such monitoring for nearby (d<1kpc) and young (age<10Myr) clusters and star-forming regions, visible from the northern hemisphere, with small telescopes. We have identified and characterized 466 variable (413 confirmed young) stars in eight young, nearby clusters. All sources vary by at least 0.2mag in V, have been observed at least 15 times in V, R, and I in the same night over a period of about 2 yr, and have a Stetson index of larger than 1. This is one of the largest samples of variable YSOs observed over such a time span and cadence in multiple filters. About two-thirds of our sample are classical T-Tauri stars, while the rest are objects with depleted or transition discs. Objects characterized as bursters show by far the highest variability. Dippers and objects whose variability is dominated by occultations from normal interstellar dust or dust with larger grains (or opaque material) have smaller amplitudes. We have established a hierarchical clustering algorithm based on the light-curve properties that allows the identification of the YSOs with the most unusual behaviour and to group sources with similar properties. We discuss in detail the light curves of the unusual objects V2492 Cyg, V350 Cep, and 2MASS J21383981+5708470.
16718. Variation of mid-IR extinction
ID:
ivo://CDS.VizieR/J/ApJ/707/89
Title:
Variation of mid-IR extinction
Short Name:
J/ApJ/707/89
Date:
21 Oct 2021
Publisher:
CDS
Description:
Based on the data obtained from the Spitzer/Galactic Legacy Infrared Midplane Survey Extraordinaire (GLIPMSE) Legacy Program and the Two Micron All Sky Survey (2MASS) project, we derive the extinction in the four IRAC bands, [3.6], [4.5], [5.8], and [8.0]um, relative to the 2MASS Ks band (at 2.16um) for 131 GLIPMSE fields along the Galactic plane within |l|<=65{deg}, using red giants and red clump giants as tracers. As a whole, the mean extinction in the IRAC bands (normalized to the 2MASS Ks band), A_[3.6]_/A_Ks_~0.63+/-0.01, A_[4.5]_/A_Ks_~0.57+/-0.03, A_[5.8]/A_Ks_~0.49+/-0.03, A_[8.0]_/A_Ks_~0.55+/-0.03, exhibits little variation with wavelength (i.e., the extinction is somewhat flat or gray). As far as individual sightline is concerned, however, the wavelength dependence of the mid-infrared interstellar extinction A_{lambda}_/A_Ks_ varies from one sightline to another, suggesting that there may not exist a "universal" IR extinction law.
16719. Variations in QSOs optical flux
ID:
ivo://CDS.VizieR/J/ApJ/698/895
Title:
Variations in QSOs optical flux
Short Name:
J/ApJ/698/895
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyze a sample of optical light curves, compiled from the literature, for 100 quasars, 70 of which have black hole mass estimates. Our sample is the largest and broadest used yet for modeling quasar variability. The sources in our sample have z<2.8, 10^42^<~{lambda}L_{lambda}_(5100{AA})<~10^46^, and 10^6^<~M_BH_/M_{sun}_<~10^10^. We model the light curves as a continuous time stochastic process, providing a natural means of estimating the characteristic timescale and amplitude of quasar variations. We employ a Bayesian approach to estimate the characteristic timescale and amplitude of flux variations; our approach is not affected by biases introduced from discrete sampling effects.
16720. Variations of O-B stars in Mercator observations
ID:
ivo://CDS.VizieR/J/A+A/463/243
Title:
Variations of O-B stars in Mercator observations
Short Name:
J/A+A/463/243
Date:
21 Oct 2021
Publisher:
CDS
Description:
We selected a large sample of O-B stars that were considered as (candidate) slowly pulsating B, beta Cep, and Maia stars after the analysis of their Hipparcos data. We analysed both the Hipparcos data and our new seven passband Geneva data collected for these stars during the first three years of scientific operations of the Mercator telescope. We performed a frequency analysis for 28 targets with more than 50 high-quality Mercator observations to improve their variability classification. We searched for frequencies by using two independent frequency analysis methods and we applied a 3.6 S/N-level criterion to locate the significant peaks in the periodograms. In total we detected 60 frequencies, among which 32 new ones. We classified 21 objects as pulsating variables (7 new confirmed pulsating stars, including 2 hybrid beta Cep/SPB stars), 6 as non-pulsating variables (binaries or spotted stars), and 1 as photometrically constant stars. For the 27 confirmed variable stars in our sample, we give the values and the corresponding standard errors of the accepted frequencies, the amplitudes, the phases, the constant terms, and the residual standard deviations as found in the seven filters of the Geneva photometric system and in the Hp filter of the Hipparcos photometric system by fitting the data with a superposition of sinusoidal models with reference epoch HJD=2450000.

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