- ID:
- ivo://CDS.VizieR/J/other/PZ/16.213
- Title:
- Variable stars in the globular cluster M92
- Short Name:
- J/other/PZ/16.21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 10 RR Lyr-type variables in M92 are studied. Data obtained from observations carried out by the author (1961-1965) and those of the past years were used. Periods of brightness variations, diagrams O-C, mean curves, period-amplitude and period-asymmetry relations were determined. Variations of the periods of studied variables were discovered; 3 of them do not possess Blazko effect. A distance of 10.5kpc to M92 was obtained according to the media,n magnitude of the studied stars.
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Search Results
- ID:
- ivo://CDS.VizieR/II/247
- Title:
- Variable Stars in the Large Magellanic Clouds
- Short Name:
- II/247
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The MACHO Project is a collaboration between scientists at the Mt. Stromlo & Siding Spring Observatories, the Center for Particle Astrophysics at the Santa Barbara, San Diego, & Berkeley campuses of the University of California, and the Lawrence Livermore National Laboratory. The primary aim of the project is a search for dark matter in the halo of the Milky Way in the form of objects like brown dwarfs or planets also named MACHOs, for MAssive Compact Halo Objects. The signature of these MACHOs is the occasional amplification of the light from extragalactic stars by the gravitational lens effect. The amplification can be large, but events are extremely rare: it is necessary to monitor photometrically several million stars for a period of years in order to obtain a useful detection rate. The MACHO project is described by Alcock et al. (1992, in "Robotic Telescopes in the 1990s", A.V. Fillippenko Ed., ASP Conf. Series 34, p.193). A dedicated 1.27-m telescope at Mount Stromlo, Australia is used to obtain observations of the LMC year-round, using a camera imaging a field of view of 0.5 square degrees at prime focus. Photometric observations of the LMC fields are obtained in two bandpasses simultaneously, using a dichroic beamsplitter to direct the blue (440-590nm) and red (590-780nm) light onto 2x2 mosaics of 2048x2048 Loral CCDs; the 15um pixels map to 0.63arcsec on the sky. The photometric reduction methods are detailed in Alcock et al. (1996ApJ...461...84A).
- ID:
- ivo://CDS.VizieR/II/320
- Title:
- Variable stars in the M16-M17 field
- Short Name:
- II/320
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The original work was published as a paper book by the Perugia University in 1999. Before that, only the variable stars list (coordinates, classifications, periods, epochs, magnitude ranges) was published (P. Maffei, 1975IBVS..985....1M) The photographic material was discontinuously collected with the two Schmidt telescopes of the Asiago Observatory and with the Schmidt telescope of the Catania Astrophysical Observatory in the years 1961 to 1991. 103a-O without or with filter GG13 and hypersensitized with NH3 or pre-flashed I-N+RG5 were used. Date, JD, exposure time, emulsion/filter combination and the observer for each plate are listed in Table 1 and Table 2. The variable search was carried out with the blink microscope plate comparator of the Asiago Observatory. Details about the history and the reduction of the observational material are given in the "main.htm" file; the digitization was made by Alessandro Nesci.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
