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Register a new userA Deep Catalog of Variable Stars in a 0.66deg^2 Lupus Field
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David T. F. Weldrake RSAA
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We have conducted a wide-field photometric survey in a single 52x52 field towards the Lupus Galactic Plane in an effort to detect transiting Hot Jupiter planets. The planet Lupus-TR-3b was identified from this work. The dataset also led to the detection of 494 field variables, all of which are new discoveries. This paper presents an overview of the project, along with the total catalog of variables, which comprises 190 eclipsing binaries (of contact, semi-contact and detached configurations), 51 miscellaneous pulsators of various types, 237 long period variables (P>=2d), 11 delta Scuti stars, 4 field RR Lyrae (3 disk and 1 halo) and 1 irregular variable. Our survey provides a complete catalog of W UMa eclipsing binaries in the field to V=18.8, which display a Gaussian period distribution of 0.277+/-0.036d. Several binary systems are likely composed of equal mass M-dwarf components and others display evidence of mass transfer. We find 17 candidate blue stragglers and one binary that has the shortest period known, 0.2009d (V=20.9). The frequency of eclipsing binaries (all types) is found to be 1.7+/-0.4x10^{-3} per star, substantially higher (by a factor of 3-10) than previously determined in the haloes of the globular clusters 47 Tuc and omega Cen. This indicates that cluster dynamics aids mass segregation and binary destruction.
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We present a variable star catalog of an extensive ground-based wide-field variability survey in the globular cluster omega Centauri. Using the ANU 40-inch (1m) telescope at Siding Spring Observatory, the cluster was observed with a 52x52 (0.75 deg^2) field for 25 nights. A total of 187 variable stars were identified in the field, 81 of which are new discoveries. This work comprises the widest field variability survey yet undertaken for this cluster. Here we present the V+R lightcurves and preliminary analysis of the detected variable stars, comprising 58 eclipsing binaries, 69 RR Lyrae stars, 36 long period variables (P>=2d) and 24 miscellaneous pulsators including 15 SX Phoenicis stars and two Type II Cepheids. Analysis of the eclipsing binary radial distribution has revealed an apparent lack of binaries in the 8-15 range, perhaps indicating two separate binary populations. Four detached binaries have short periods (<2.5d) and are likely composed of low-mass M-dwarf components, useful for testing stellar evolution models. One further detached system has a period of 0.8 days and due to the blueness of the system could be composed of white dwarf stars. Analysis of the RR Lyrae sample has produced a reddening corrected distance modulus (also accounting for metallicity spread) for the cluster of 13.68+-0.27, a result consistent with previously published values. This paper also presents a total stellar database comprising V and I photometry (with astrometry better than 0.25) for 203,892 stars with 12.0<V<21.0 and 25-night V+R lightcurves for 109,726 stars (14.0<V<22.0) for both the cluster and the field.
We present a comprehensive re-analysis of stellar photometric variability in the field of the open cluster M37 following the application of a new photometry and de-trending method to MMT/Megacam image archive. This new analysis allows a rare opportunity to explore photometric variability over a broad range of time-scales, from minutes to a month. The intent of this work is to examine the entire sample of over 30,000 objects for periodic, aperiodic, and sporadic behaviors in their light curves. We show a modified version of the fast $chi^{2}$ periodogram algorithm (F$chi^{2}$) and change-point analysis (CPA) as tools for detecting and assessing the significance of periodic and non-periodic variations. The benefits of our new photometry and analysis methods are evident. A total of 2306 stars exhibit convincing variations that are induced by flares, pulsations, eclipses, starspots, and unknown causes in some cases. This represents a 60% increase in the number of variables known in this field. Moreover, 30 of the previously identified variables are found to be false positives resulting from time-dependent systematic effects. New catalog includes 61 eclipsing binary systems, 92 multiperiodic variable stars, 132 aperiodic variables, and 436 flare stars, as well as several hundreds of rotating variables. Based on extended and improved catalog of variables, we investigate the basic properties (e.g., period, amplitude, type) of all variables. The catalog can be accessed through the web interface (http://stardb.yonsei.ac.kr/).
We have compiled the first all-sky mid-infrared variable-star catalog based on Wide-field Infrared Survey Explorer (WISE) five-year survey data. Requiring more than 100 detections for a given object, 50,282 carefully and robustly selected periodic variables are discovered, of which 34,769 (69%) are new. Most are located in the Galactic plane and near the equatorial poles. A method to classify variables based on their mid-infrared light curves is established using known variable types in the General Catalog of Variable Stars. Careful classification of the new variables results in a tally of 21,427 new EW-type eclipsing binaries, 5654 EA-type eclipsing binaries, 1312 Cepheids, and 1231 RR Lyraes. By comparison with known variables available in the literature, we estimate that the misclassification rate is 5% and 10% for short- and long-period variables, respectively. A detailed comparison of the types, periods, and amplitudes with variables in the Catalina catalog shows that the independently obtained classifications parameters are in excellent agreement. This enlarged sample of variable stars will not only be helpful to study Galactic structure and extinction properties, they can also be used to constrain stellar evolution theory and as potential candidates for the James Webb Space Telescope.
The All-Sky Automated Survey for Supernovae (ASAS-SN) provides long baseline (${sim}4$ yrs) $V-$band light curves for sources brighter than V$lesssim17$ mag across the whole sky. We produced V-band light curves for a total of ${sim}61.5$ million sources and systematically searched these sources for variability. We identified ${sim} 426,000$ variables, including ${sim} 219,000$ new discoveries. Most (${sim}74%$) of our discoveries are in the Southern hemisphere. Here we use spectroscopic information from LAMOST, GALAH, RAVE, and APOGEE to study the physical and chemical properties of these variables. We find that metal-poor eclipsing binaries have orbital periods that are shorter than metal-rich systems at fixed temperature. We identified rotational variables on the main-sequence, red giant branch and the red clump. A substantial fraction (${gtrsim}80%$) of the rotating giants have large $v_{rm rot}$ or large NUV excesses also indicative of fast rotation. The rotational variables have unusual abundances suggestive of analysis problems. Semi-regular variables tend to be lower metallicity ($rm [Fe/H]{sim}-0.5$) than most giant stars. We find that the APOGEE DR16 temperatures of oxygen-rich semi-regular variables are strongly correlated with the $W_{RP}-W_{JK}$ color index for $rm T_{eff}lesssim3800$ K. Using abundance measurements from APOGEE DR16, we find evidence for Mg and N enrichment in the semi-regular variables. We find that the Aluminum abundances of the semi-regular variables are strongly correlated with the pulsation period, where the variables with $rm Pgtrsim 60$ days are significantly depleted in Al.
The number of known periodic variables has grown rapidly in recent years. Thanks to its large field of view and faint limiting magnitude, the Zwicky Transient Facility (ZTF) offers a unique opportunity to detect variable stars in the northern sky. Here, we exploit ZTF Data Release 2 (DR2) to search for and classify variables down to r ~ 20.6 mag. We classify 781,602 periodic variables into 11 main types using an improved classification method. Comparison with previously published catalogs shows that 621,702 objects (79.5%) are newly discovered or newly classified, including ~700 Cepheids, ~5000 RR Lyrae stars, ~15,000 Delta Scuti variables, ~350,000 eclipsing binaries, ~100,000 long-period variables, and about 150,000 rotational variables. The typical misclassification rate and period accuracy are on the order of 2% and 99%, respectively. 74% of our variables are located at Galactic latitudes, $|b|<10^circ$. This large sample of Cepheids, RR Lyrae, Delta Scuti stars, and contact (EW-type) eclipsing binaries is helpful to investigate the Galaxys disk structure and evolution with an improved completeness, areal coverage, and age resolution. Specifically, the northern warp and the disks edge at distances of 15--20 kpc are significantly better covered than previously. Among rotational variables, RS Canum Venaticorum and BY Draconis-type variables can be separated easily. Our knowledge of stellar chromospheric activity would benefit greatly from a statistical analysis of these types of variables.
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