- ID:
- ivo://CDS.VizieR/J/MNRAS/447/3536
- Title:
- Variables in the fields of M35 and NGC2158
- Short Name:
- J/MNRAS/447/3536
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multiyear survey aimed at collecting (1) high-precision (~5 milli-mag), (2) fast-cadence (~3-min), and (3) relatively long duration (~10d) multiband photometric series. The goal of the survey is to discover and characterize efficiently variable objects and exoplanetary transits in four fields containing five nearby open clusters spanning a broad range of ages. More in detail, our project will (1) constitute a preparatory survey for the High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N) mounted at the Telescopio Nazionale Galileo (TNG), which will be used for spectroscopic follow-up of any target of interest that this survey discovers or characterizes, (2) measure rotational periods and estimate the activity level of targets we are already monitoring with HARPS and HARPS-N for exoplanet transit search, and (3) long-term characterization of selected targets of interest in open clusters within the planned K2 fields. In this first paper, we give an overview of the project, and report on the variability of objects within the first of our selected fields, which contains two open clusters: M35 and NGC 2158. We detect 519 variable objects, 273 of which are new discoveries, while the periods of most of the previously known variables are considerably improved.
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Search Results
- 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/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.
- ID:
- ivo://CDS.VizieR/J/AJ/129/2232
- Title:
- Variable stars in And I and And III
- Short Name:
- J/AJ/129/2232
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of variable star searches of the M31 dwarf spheroidal (dSph) companions Andromeda I and Andromeda III using the Hubble Space Telescope. A total of 100 variable stars were found in And I, while 56 were found in And III. One variable found in And I and another in And III may be type II Cepheids. In addition to this variable in And III, another four variables are anomalous Cepheids (ACs). So far, no definite ACs have been discovered in And I.
- ID:
- ivo://CDS.VizieR/J/AJ/124/1464
- Title:
- Variable stars in Andromeda VI
- Short Name:
- J/AJ/124/1464
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have surveyed Andromeda VI, a dwarf spheroidal galaxy companion to M31, for variable stars by using F450W and F555W observations obtained with the Hubble Space Telescope on 1999 October 25 and 1999 October 27 (WFPC2 instrument). A total of 118 variables were found, including 111 RR Lyrae stars, six anomalous Cepheids, and one variable that we were unable to classify. We find that the Andromeda VI anomalous Cepheids have properties consistent with those of anomalous Cepheids in other dwarf spheroidal galaxies. We revise the existing period-luminosity relations for these variables. Further, using these and other available data, we show that there is no clear difference between fundamental and first-overtone anomalous Cepheids in a period-amplitude diagram at shorter periods, unlike the RR Lyrae stars. For the Andromeda VI RR Lyrae stars, we find that they lie close to the Oosterhoff type I Galactic globular clusters in the period-amplitude diagram, although the mean period of the RRab stars, <P_ab_>=0.588days, is slightly longer than that of the typical Oosterhoff type I cluster. The mean V magnitude of the RR Lyrae stars in Andromeda VI is 25.29+/-0.03, resulting in a distance 815+/-25kpc on the Lee, Demarque, & Zinn (1990ApJ...350..155L) distance scale. This is consistent with the distance derived from the I magnitude of the tip of the red giant branch. Similarly, the properties of the RR Lyrae stars indicate a mean abundance for Andromeda VI that is consistent with that derived from the mean red giant branch color.
- ID:
- ivo://CDS.VizieR/J/ApJS/194/27
- Title:
- Variable stars in Cygnus OB2
- Short Name:
- J/ApJS/194/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of photometrically variable stars discovered within two 21.3'x21.3' fields centered on the Cygnus OB2 association (Cyg OB2). There have hitherto been no deep optical variability studies of Cyg OB2, despite it being replete with early-type massive stars, likely due to the high and variable extinction (up to A_V_~20) that permeates much of the region. Here, we provide results of the first variability study with this combination of spatial coverage (~0.5deg) and photometric depth (R~21mag). We find 121 stars to be variable in both R and I bands, 115 of them newly discovered. Of the 121 variables, we identify 27 eclipsing binaries and eclipsing-binary candidates, 52 pulsating variables, and 20 potential Herbig Ae/Be stars. Confirming both the status and the cluster membership of the Herbig Ae/Be stars would address the uncertainty regarding the age and star formation history of Cyg OB2. We match our catalog to known variables and binaries in the region, Two Micron All Sky Survey near-IR data, and Chandra X-ray observations to find counterparts to new variables in other wavelengths.
- ID:
- ivo://CDS.VizieR/J/ApJ/701/1323
- Title:
- Variable stars in Fornax dSph. III.
- Short Name:
- J/ApJ/701/1323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new study of the variable star population in globular cluster 5 of the Fornax dSph, based on B and V time series photometry obtained with the MagIC camera of the 6.5m Magellan Clay telescope and complementary Hubble Space Telescope archive data. Light curves and accurate periodicities were obtained for 30 RR Lyrae stars and one SX Phoenicis variable. The RR Lyrae sample includes 15 fundamental-mode pulsators, 13 first-overtone pulsators, one candidate double-mode pulsator and one RR Lyrae star with uncertain type classification. The average and minimum periods of the ab-type RR Lyrae stars, <P_ab_>=0.590days, P_ab,min_=0.53297days and the position in the horizontal branch type-metallicity plane, indicate that the cluster has Oosterhoff-intermediate properties, basically confirming previous indications by Mackey & Gilmore, although with some differences both in the period and type classification of individual variables.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A20
- Title:
- Variable stars in globular NGC7492
- Short Name:
- J/A+A/556/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a photometric V,R,I CCD time-series analysis with a baseline of about eight years of the outer-halo globular cluster NGC 7492 with the aim of searching for new variables and using these (and the previously known variables) to determine the physical parameters of interest for the cluster (e.g. metallicity, absolute magnitude of the horizontal branch, distance, etc.). We used difference image analysis to extract precise light curves in the relatively crowded star field, especially towards the densely populated central region. Several different approaches were used for variability detection that recover the known variables and lead to new discoveries. We determined the physical parameters of the only RR0 star using a light-curve Fourier decomposition analysis. We found one new long-period variable and two SX Phe stars in the blue straggler region. We also present one candidate SX Phe star that requires follow-up observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/121
- Title:
- Variable stars in Her dwarf galaxy
- Short Name:
- J/ApJ/756/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first time-series study of the ultra-faint dwarf galaxy Hercules. Using a variety of telescope/instrument facilities we secured about 50 V and 80 B epochs. These data allowed us to detect and characterize 10 pulsating variable stars in Hercules. Our final sample includes six fundamental-mode (ab-type) and three first-overtone (c-type) RR Lyrae stars, and one Anomalous Cepheid. The average period of the ab-type RR Lyrae stars, <P_ab_>=0.68days ({sigma}=0.03days), places Hercules in the Oosterhoff II group, as found for almost the totality of the ultra-faint dwarf galaxies investigated so far for variability. The RR Lyrae stars were used to obtain independent estimates of the metallicity, reddening, and distance to Hercules, for which we find [Fe/H]=-2.30+/-0.15dex, E(B-V)=0.09+/-0.02mag, and (m-M)_0_=20.6+/-0.1mag, in good agreement with the literature values. We have obtained a V, B-V color-magnitude diagram (CMD) of Hercules that reaches V~25mag and extends beyond the galaxy's half-light radius over a total area of 40'x36'. The CMD and the RR Lyrae stars indicate the presence of a population as old and metal-poor as (at least) the Galactic globular cluster M68.
- ID:
- ivo://CDS.VizieR/J/PASP/126/616
- Title:
- Variable stars in Leo I dSph
- Short Name:
- J/PASP/126/616
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From archival ground-based images of the Leo I dwarf spheroidal galaxy, we have identified and characterized the pulsation properties of 164 candidate RR Lyrae variables and 55 candidate anomalous and/or short-period Cepheids. We have also identified 19 candidate long-period variable stars and 13 other candidate variables whose physical nature is unclear, but due to the limitations of our observational material we are unable to estimate reliable periods for them.