- 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.
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- 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/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/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.
3385. Variable stars in M54
- ID:
- ivo://CDS.VizieR/J/MNRAS/406/329
- Title:
- Variable stars in M54
- Short Name:
- J/MNRAS/406/329
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new B, V and I CCD time-series photometry for 177 variable stars in a 13x13arcmin^2^ field centred on the globular cluster M54 using the European Southern Observatory (ESO)-Danish 1.54-m telescope in La Silla, 94 of which are newly identified variables. The total sample is composed of two anomalous Cepheids, 144 RR Lyrae stars (108 RR0 and 36 RR1), three SX Phoenicis, seven eclipsing binaries (five W UMa and two Algol binaries), three variables of uncertain classification and 18 long-period variables. Ephemerides are provided for all the observed short-period variables. The positional accuracy is better than 0.2".
- ID:
- ivo://CDS.VizieR/J/ApJ/825/50
- Title:
- Variable stars in M31 & M33. III. YSGs & RSGs
- Short Name:
- J/ApJ/825/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent supernova (SN) and transient surveys have revealed an increasing number of non-terminal stellar eruptions. Though the progenitor class of these eruptions includes the most luminous stars, little is known of the pre-SN mechanics of massive stars in their most evolved state, thus motivating a census of possible progenitors. From surveys of evolved and unstable luminous star populations in nearby galaxies, we select a sample of yellow and red supergiant (RSG) candidates in M31 and M33 for review of their spectral characteristics and spectral energy distributions (SEDs). Since the position of intermediate- and late-type supergiants on the color-magnitude diagram can be heavily contaminated by foreground dwarfs, we employ spectral classification and multi-band photometry from optical and near-infrared surveys to confirm membership. Based on spectroscopic evidence for mass loss and the presence of circumstellar (CS) dust in their SEDs, we find that 30%-40% of the yellow supergiants are likely in a post-RSG state. Comparison with evolutionary tracks shows that these mass-losing, post-RSGs have initial masses between 20 and 40M_{sun}_. More than half of the observed RSGs in M31 and M33 are producing dusty CS ejecta. We also identify two new warm hypergiants in M31, J004621.05+421308.06 and J004051.59+403303.00, both of which are likely in a post-RSG state.
- ID:
- ivo://CDS.VizieR/J/ApJ/790/48
- Title:
- Variable stars in M31 & M33. II. LBVs
- Short Name:
- J/ApJ/790/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An increasing number of non-terminal eruptions are being found in the numerous surveys for optical transients. Very little is known about these giant eruptions, their progenitors and their evolutionary state. A greatly improved census of the likely progenitor class, including the most luminous evolved stars, the luminous blue variables (LBVs), and the warm and cool hypergiants is now needed for a complete picture of the final pre-supernova stages of very massive stars. We have begun a survey of the evolved and unstable luminous star populations in several nearby resolved galaxies. In this second paper on M31 and M33, we review the spectral characteristics, spectral energy distributions, circumstellar ejecta, and evidence for mass loss for 82 luminous and variable stars. We show that many of these stars have warm circumstellar dust including several of the Fe II emission line stars, but conclude that the confirmed LBVs in M31 and M33 do not. The confirmed LBVs have relatively low wind speeds even in their hot, quiescent or visual minimum state compared to the B-type supergiants and Of/WN stars which they spectroscopically resemble. The nature of the Fe II emission line stars and their relation to the LBV state remains uncertain, but some have properties in common with the warm hypergiants and the sgB[e] stars. Several individual stars are discussed in detail. We identify three possible candidate LBVs and three additional post-red supergiant candidates. We suggest that M33-013406.63 (UIT301,B416) is not an LBV/S Dor variable, but is a very luminous late O-type supergiant and one of the most luminous stars or pair of stars in M33.
- ID:
- ivo://CDS.VizieR/J/MNRAS/487/3505
- Title:
- Variable stars in NGC 2244
- Short Name:
- J/MNRAS/487/3505
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of the UBVIc variability search for variable stars in the young open cluster NGC 2244. In total, we found 245 variable stars. Most of them, are pre-main sequence variables with irregular variations typical for classical T Tauri stars (CTTSs). We found also 23 periodic variables, probably weak-lined T Tauri stars (WTTSs). We detected also four candidates for {delta} Scuti stars and 7 eclipsing binaries. Based on the mid-infrared Spitzer and WISE photometry and near infrared JHKS 2MASS photometry, we classified 104 young stellar sources among our variables: 1 Class I object, 1 Class I/flat spectrum object, 4 flat spectrum objects, 91 Class II objects, and 7 transition disc objects. This classification, together with r'i'H{alpha} IPHAS photometry and JHK UKIDSS photometry, were used for identification of pre-main sequence stars among irregular and periodic variables. In this way, 97 CTTS candidates (96 irregular and one periodic variable), 68 WTTS candidates (54 irregular and 14 periodic variables), and 6 Herbig Ae/Be stars were found. For 223 variable stars we calculated membership probability based on proper motions from Gaia DR2 catalogue. Majority of them, 143 stars, are cluster members with probability greater than 70 per cent. For only 36 variable stars the membership probability is smaller than 20 per cent.
- ID:
- ivo://CDS.VizieR/J/MNRAS/362/117
- Title:
- Variable stars in Pegasus field
- Short Name:
- J/MNRAS/362/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent wide field photometric surveys, which target a specific field for long durations, are ideal for studying both long- and short-period stellar variability. Here, we report on 75 variable stars detected during the observations of a field in Pegasus using the Wide Angle Search for Planets Prototype (WASP0) instrument, 73 of which are new discoveries. The variables detected include 16 {delta} Scuti stars, 34 eclipsing binaries, 3 BY Draconis stars and 4 RR Lyraes. We estimate that the fraction of stars in the field brighter than V~13.5 exhibiting variable behaviour with an amplitude greater than 0.6% rms is ~0.4%. These results are compared with other wide field stellar variability surveys, and implications for detecting transits due to extra-solar planets are discussed.
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/4349
- Title:
- Variable stars in Sculptor dSph
- Short Name:
- J/MNRAS/462/4349
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the identification of 634 variable stars in the Milky Way dwarf spheroidal (dSph) satellite Sculptor based on archival ground-based optical observations spanning ~24yr and covering ~2.5deg^2^. We employed the same methodologies as the 'Homogeneous Photometry' series published by Stetson. In particular, we have identified and characterized one of the largest (536) RR Lyrae samples so far in a Milky Way dSph satellite. We have also detected four Anomalous Cepheids, 23 SX Phoenicis stars, five eclipsing binaries, three field variable stars, three peculiar variable stars located above the horizontal branch - near to the locus of BL Herculis - that we are unable to classify properly. Additionally, we identify 37 long period variables plus 23 probable variable stars, for which the current data do not allow us to determine the period. We report positions and finding charts for all the variable stars, and basic properties (period, amplitude, mean magnitude) and light curves for 574 of them. We discuss the properties of the RR Lyrae stars in the Bailey diagram, which supports the coexistence of subpopulations with different chemical compositions. We estimate the mean mass of Anomalous Cepheids (~1.5M_{sun}_) and SX Phoenicis stars (~1M_{sun}_). We discuss in detail the nature of the former. The connections between the properties of the different families of variable stars are discussed in the context of the star formation history of the Sculptor dSph galaxy.
