- ID:
- ivo://CDS.VizieR/J/ApJ/731/17
- Title:
- Variability of low-mass stars in SDSS Stripe 82
- Short Name:
- J/ApJ/731/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of periodic stellar variability in the "Stripe 82" region of the Sloan Digital Sky Survey. After aggregating and re-calibrating catalog-level data from the survey, we ran a period-finding algorithm (Supersmoother) on all point-source light curves. We used color selection to identify systems that are likely to contain low-mass stars, in particular M dwarfs and white dwarfs. In total, we found 207 candidates, the vast majority of which appear to be in eclipsing binary systems. The catalog described in this paper includes 42 candidate M dwarf/white dwarf pairs, four white dwarf pairs, 59 systems whose colors indicate they are composed of two M dwarfs and whose light-curve shapes suggest they are in detached eclipsing binaries, and 28 M dwarf systems whose light-curve shapes suggest they are in contact binaries. We find no detached systems with periods longer than 3 days, thus the majority of our sources are likely to have experienced orbital spin-up and enhanced magnetic activity.
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- ID:
- ivo://CDS.VizieR/J/AcA/63/339
- Title:
- Variability Survey in Stock 14 cluster
- Short Name:
- J/AcA/63/339
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a photometric variability survey in the young open cluster Stock 14 and the surrounding fields. In total, we detected 103 variable stars of which 88 are new discoveries. We confirm short-period, low-amplitude light variations in two eclipsing members of the cluster, HD 101838 and HD 101794. In addition, we find two new {beta} Cep stars of which one, HD 101993, is also a member. The sample of pulsating cluster members is supplemented by one multimode slowly pulsating B-type star and several single-mode candidates of this type. The other pulsating stars in our sample are mostly field stars. In particular, we found 14 {delta} Sct stars including one {gamma} Dor/{delta} Sct hybrid pulsator.
- ID:
- ivo://CDS.VizieR/J/A+A/598/A108
- Title:
- Variability survey of brightest stars
- Short Name:
- J/A+A/598/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar evolution theory of massive stars remains uncalibrated with high-precision photometric observational data mainly due to small number of luminous stars monitored from space. Automated all-sky surveys have revealed numerous variable stars but most luminous stars are often overexposed. Targeted campaigns can improve the time base of photometric data for those objects. The aim of this investigation is to study the variability of luminous stars at different time-scales in young open clusters and OB associations. We monitored 22 open clusters and associations from 2011 to 2013 using a 0.25-m telescope. Variable stars were detected by comparing the overall light-curve scatter with measurement uncertainties. Variability was analysed by the light curve feature extraction tool FATS. Periods of pulsating stars were determined using the discrete Fourier transform code SigSpec. We then classified the variable stars based on their pulsation periods and available spectral information. We obtained light curves for more than 20000 sources of which 354 were found to be variable. Amongst them we find 80 eclipsing binaries, 31 {alpha} Cyg, 13 {beta} Cep, 62 Be, 16 slowly pulsating B, 7 Cepheid, 1 {gamma} Doradus, 3 Wolf-Rayet and 63 late-type variable stars. Up to 55% of these stars are potential new discoveries as they are not present in the Variable Star Index (VSX) database. We find the cluster membership fraction for variable stars to be 13% with an upper limit of 35%.
- ID:
- ivo://CDS.VizieR/J/ApJS/186/233
- Title:
- Variable point sources in SDSS stripe 82. I.
- Short Name:
- J/ApJS/186/233
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first results of a study of variable point sources identified using multi-color timeseries photometry from Sloan Digital Sky Survey (SDSS) Stripe 82, including data from the SDSS-II Supernova Survey, over a span of nearly 10 years (1998-2007). We construct a light-curve catalog of 221842 point sources in the R.A. 0-4hr half of Stripe 82, limited to r=22.0mag, that have at least 10 detections in the ugriz bands and color errors <0.2mag. These sources are then classified by color and by cross matching them to existing SDSS catalogs of interesting objects. Inhomogeneous ensemble differential photometry techniques are used to greatly improve our sensitivity to variability and reduce contamination by sources that appear variable due to large photometric noise or systematic effects caused by non-uniform photometric conditions throughout the survey. We use robust variable identification methods to extract 6520 variable candidates from this data set, resulting in an overall variable fraction of ~2.9% at the level of ~0.05mag variability. Despite the sparse and uneven time sampling of the light-curve data, we discover 143 periodic variables in total. Due to period ambiguity caused by relatively poor phase coverage, we identify a smaller final set of 101 periodic variables with well-determined periods and light curves. Among these are 55 RR Lyrae, 30 eclipsing binary candidates, and 16 high-amplitude Delta Scuti variables. In addition to these objects, we also identify a sample of 2704 variable quasars matched to the SDSS Quasar Catalog, which make up a large fraction of our variable candidates. An additional 2403 quasar candidates are tentatively identified and selected by their non-stellar colors and variability. A sample of 11328 point sources that appear to be nonvariable given the limits of our variability sensitivity is also briefly discussed. Finally, we describe several interesting objects discovered among our eclipsing binary candidates, and illustrate the use of our publicly available light-curve catalog by tracing Galaxy halo substructure with our small sample of RR Lyrae variables.
- ID:
- ivo://CDS.VizieR/J/A+A/537/A116
- Title:
- Variables in Centaurus field F170
- Short Name:
- J/A+A/537/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used deep V-band and JHKs-band observations to investigate variability and stellar populations near the Galactic plane in Centaurus, and compare the observations with the Galactic model of Besancon. By applying image subtraction technique to a series of over 580 V-band frames taken with the ESO VLT/VIMOS instrument during two contiguous nights in April 2005 we have detected 333 variables among 84,734 stars in the brightness range 12.7<V<26.0mag. Infrared data collected in March 2010 with the new ESO VISTA telescope allowed us to construct deep combined optical-IR colour-magnitude and colour-colour diagrams. All detected variables but four transit candidates are reported for the first time. The majority of the variables are eclipsing/ellipsoidal binaries and delta Scuti-type pulsators. The occurrence rate of eclipsing/ellipsoidal variables reached ~0.28% of all stars. This is very close to the highest fraction of binary systems detected using ground-based data so far (0.30%), but still about four times smaller than the average occurrence rate recently obtained from the Kepler space mission after 44 days of operation. Comparison of the observed Ks vs. V-Ks diagram with a diagram based on the Besancon model shows significant effects of both distance and reddening in the investigated direction of the sky. We demonstrate that the best model indicates presence of absorbing clouds at distances 11-13kpc from the Sun in the minor Carina-Sagittarius Arm.
276. Variables in 47 Tuc
- ID:
- ivo://CDS.VizieR/J/ApJ/559/1060
- Title:
- Variables in 47 Tuc
- Short Name:
- J/ApJ/559/1060
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Differential time series photometry has been derived for 46,422 main-sequence stars in the core of 47 Tucanae. The observations consisted of near-continuous 160 s exposures alternating between the F555W and F814W filters for 8.3 days in 1999 July with the Wide Field Planetary Camera 2 on the Hubble Space Telescope. Using Fourier and other search methods, 11 detached eclipsing binaries and 15 W Ursa Majoris stars have been discovered plus an additional 10 contact or near-contact noneclipsing systems. After correction for nonuniform area coverage of the survey, the observed frequencies of detached eclipsing binaries and W UMa stars within 90" of the cluster center are 0.022% and 0.031%, respectively. The data were taken over an 8.3 day period, 1999 July 3-11, during which HST was pointed continuously at 47 Tuc.
- ID:
- ivo://CDS.VizieR/J/AJ/153/104
- Title:
- Variables observed in the Galactic disk by AST3-1
- Short Name:
- J/AJ/153/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- AST3-1 is the second-generation wide-field optical photometric telescope dedicated to time-domain astronomy at Dome A, Antarctica. Here, we present the results of an i-band images survey from AST3-1 toward one Galactic disk field. Based on time-series photometry of 92583 stars, 560 variable stars were detected with i magnitude {<=}16.5mag during eight days of observations; 339 of these are previously unknown variables. We tentatively classify the 560 variables as 285 eclipsing binaries (EW, EB, and EA), 27 pulsating variable stars ({delta} Scuti, {gamma} Doradus, {delta} Cephei variable, and RR Lyrae stars), and 248 other types of variables (unclassified periodic, multiperiodic, and aperiodic variable stars). Of the eclipsing binaries, 34 show O'Connell effects. One of the aperiodic variables shows a plateau light curve and another variable shows a secondary maximum after peak brightness. We also detected a complex binary system with an RS CVn-like light-curve morphology; this object is being followed-up spectroscopically using the Gemini South telescope.
- ID:
- ivo://CDS.VizieR/J/ApJS/239/5
- Title:
- Variable stars and cand. planets from K2
- Short Name:
- J/ApJS/239/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We produce light curves for all ~34000 targets observed with K2 in Campaign 17 (C17), identifying 34 planet candidates, 184 eclipsing binaries, and 222 other periodic variables. The forward-facing direction of the C17 field means follow-up can begin immediately now that the campaign has concluded and interesting targets have been identified. The C17 field has a large overlap with C6, so this latest campaign also offers an infrequent opportunity to study a large number of targets already observed in a previous K2 campaign. The timing of the C17 data release, shortly before science operations begin with the Transiting Exoplanet Survey Satellite (TESS), also lets us exercise some of the tools and methods developed for identification and dissemination of planet candidates from TESS. We find excellent agreement between these results and those identified using only K2-based tools. Among our planet candidates are several planet candidates with sizes <4R_{Earth}_ and orbiting stars with Kp<~10 (indicating good RV targets of the sort TESS hopes to find) and a Jupiter-sized single-transit event around a star already hosting a 6 day planet candidate.
- ID:
- ivo://CDS.VizieR/J/AJ/150/107
- Title:
- Variable stars from TNTS. I. 2012-2014
- Short Name:
- J/AJ/150/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we report the detections of stellar variabilities from the first two years of observations of a sky area of about 1300 square degrees from the Tsinghua University-NAOC Transient Survey. A total of 1237 variable stars (including 299 new ones) were detected with a brightness <18.0mag and a magnitude variation >~0.1mag on a timescale from a few hours to a few hundred days. Among such detections, we tentatively identified 661 RR Lyrae stars, 431 binaries, 72 semi-regular pulsators, 29 Mira stars, 11 slow irregular variables, 11 RS Canum Venaticorum stars, 7 Gamma Doradus stars, 5 long-period variables, 3 W Virginis stars, 3 Delta Scuti stars, 2 Anomalous Cepheids, 1 Cepheid, and 1 nova-like star based on their time-series variability index J_s_ and their phased diagrams. Moreover, we found that 14 RR Lyrae stars show the Blazhko effect and 67 contact eclipsing binaries exhibit the O'Connell effect. Since the period and amplitude of light variations of RR Lyrae variables depend on their chemical compositions, their photometric observations can be used to investigate the distribution of metallicity along the direction perpendicular to the Galactic disk. We find that the metallicity of RR Lyrae stars shows large scatter at regions closer to the Galactic plane (e.g., -3.0<[Fe/H]<0) but tends to converge at [Fe/H]~-1.7 at larger Galactic latitudes. This variation may be related to the fact that the RRAB Lyrae stars in the Galactic halo come from globular clusters with different metallicities and vertical distances, i.e., OoI and OoII populations, favoring the dual-halo model.
- ID:
- ivo://CDS.VizieR/J/ApJ/773/54
- Title:
- Variable stars in and around NGC 2264 with BEST
- Short Name:
- J/ApJ/773/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Time-series photometry of the CoRoT field SRa01 was carried out with the Berlin Exoplanet Search Telescope II in 2008/2009. A total of 1161 variable stars were detected, of which 241 were previously known and 920 are newly found. Several new, variable young stellar objects have been discovered. The study of the spatial distribution of eclipsing binaries revealed the higher relative frequency of Algols toward the center of the young open cluster NGC 2264. In general Algol frequency obeys an isotropic distribution of their angular momentum vectors, except inside the cluster, where a specific orientation of the inclinations is the case. We suggest that we see the orbital plane of the binaries almost edge-on.
