- ID:
- ivo://CDS.VizieR/J/AJ/155/39
- Title:
- Variability properties of TIC sources with KELT
- Short Name:
- J/AJ/155/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Kilodegree Extremely Little Telescope (KELT) has been surveying more than 70% of the celestial sphere for nearly a decade. While the primary science goal of the survey is the discovery of transiting, large-radii planets around bright host stars, the survey has collected more than 10^6^ images, with a typical cadence between 10-30 minutes, for more than four million sources with apparent visual magnitudes in the approximate range 7<V<13. Here, we provide a catalog of 52741 objects showing significant large-amplitude fluctuations likely caused by stellar variability, as well as 62229 objects identified with likely stellar rotation periods. The detected variability ranges in rms-amplitude from ~3 mmag to ~2.3 mag, and the detected periods range from ~0.1 to >~2000 days. We provide variability upper limits for all other ~4000000 sources. These upper limits are principally a function of stellar brightness, but we achieve typical 1{sigma} sensitivity on 30 min timescales down to ~5 mmag at V~8, and down to ~43 mmag at V~13. We have matched our catalog to the TESS Input catalog and the AAVSO Variable Star Index to precipitate the follow-up and classification of each source. The catalog is maintained as a living database on the Filtergraph visualization portal at the URL https://filtergraph.com/kelt_vars.
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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/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/AJ/145/160
- Title:
- Variables in LMC globular clusters. III. Reticulum
- Short Name:
- J/AJ/145/160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the third in a series of papers studying the variable stars in old globular clusters in the Large Magellanic Cloud. The primary goal of this series is to look at how the characteristics and behavior of RR Lyrae stars in Oosterhoff-intermediate systems compare to those of their counterparts in Oosterhoff-I/II systems. In this paper we present the results of our new time-series BVI photometric study of the globular cluster Reticulum. We found a total of 32 variables stars (22 RRab, 4 RRc, and 6 RRd stars) in our field of view. We present photometric parameters and light curves for these stars. We also present physical properties, derived from Fourier analysis of light curves, for some of the RR Lyrae stars. We discuss the Oosterhoff classification of Reticulum and use our results to re-derive the distance modulus and age of the cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/144/186
- Title:
- Variables in LMC globular clusters. II. NGC 1786
- Short Name:
- J/AJ/144/186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second in a series of papers studying the variable stars in Large Magellanic Cloud globular clusters. The primary goal of this series is to study how RR Lyrae stars in Oosterhoff-intermediate systems compare to their counterparts in Oosterhoff I/II systems. In this paper, we present the results of our new time-series B-V photometric study of the globular cluster NGC 1786. A total of 65 variable stars were identified in our field of view. These variables include 53 RR Lyraes (27 RRab, 18 RRc, and 8 RRd), 3 classical Cepheids, 1 Type II Cepheid, 1 Anomalous Cepheid, 2 eclipsing binaries, 3 Delta Scuti/SX Phoenicis variables, and 2 variables of undetermined type. Photometric parameters for these variables are presented. We present physical properties for some of the RR Lyrae stars, derived from Fourier analysis of their light curves. We discuss several different indicators of Oosterhoff type which indicate that the Oosterhoff classification of NGC 1786 is not as clear cut as what is seen in most globular clusters.
- 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.
- 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/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/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.
