Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA First Catalog of Variable Stars Measured by the Asteroid Terrestrial-impact Last Alert System (ATLAS)
404
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The Asteroid Terrestrial-impact Last Alert System (ATLAS) carries out its primary planetary defense mission by surveying about 13000 deg^2 at least four times per night. The resulting data set is useful for the discovery of variable stars to a magnitude limit fainter than r~18, with amplitudes down to 0.01 mag for bright objects. Here we present a Data Release One catalog of variable stars based on analyzing 142 million stars measured at least 100 times in the first two years of ATLAS operations. Using a Lomb-Scargle periodogram and other variability metrics, we identify 4.7 million candidate variables which we analyze in detail. Through Space Telescope Science Institute, we publicly release lightcurves for all of them, together with a vector of 169 classification features for each star. We do this at the level of unconfirmed candidate variables in order to provide the community with a large set of homogeneously analyzed photometry and avoid pre-judging which types of objects others may find most interesting. We use machine learning to classify the candidates into fifteen different broad categories based on lightcurve morphology. About 10% (430,000 stars) pass extensive tests designed to screen out spurious variability detections: we label these as `probable variables. Of these, 230,000 receive specific classifications as eclipsing binaries, pulsating, Mira-type, or sinusoidal variables: these are the `classified variables. New discoveries among the probable variables number more than 300,000, while 150,000 of the classified variables are new, including about 10,000 pulsating variables, 2,000 Mira stars, and 70,000 eclipsing binaries.
rate research
Read More
The number of known variable stars has increased by several magnitudes over the last decade, and automated classification routines are becoming increasingly important to cope with this development. Here we show that the upside-down CBH variables, which were proposed as a potentially new class of variable stars by Heinze et al. (2018) in the ATLAS First Catalogue of Variable Stars, are, at least to a high percentage, made up of alpha2 Canum Venaticorum (ACV) variables - that is, photometrically variable magnetic chemically peculiar (CP2/He-peculiar) stars - with distinct double-wave light curves. Using suitable selection criteria, we identified 264 candidate ACV variables in the ATLAS variable star catalogue. 62 of these objects were spectroscopically confirmed with spectra from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (all new discoveries except for nine stars) and classified on the MK system. The other 202 stars are here presented as ACV star candidates that require spectroscopic confirmation. The vast majority of our sample of stars are main-sequence objects. Derived masses range from 1.4M(Sun) to 5M(Sun), with half our sample stars being situated in the range from 2 M(Sun) to 2.4 M(Sun), in good agreement with the spectral classifications. Most stars belong to the thin or thick disk; four objects, however, classify as members of the halo population. With a peak magnitude distribution at around 14th magnitude, the here presented stars are situated at the faint end of the known Galactic mCP star population. Our study highlights the need to consider rare variability classes, like ACV variables, in automated classification routines.
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.
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 report the discovery of 3 new Double Periodic Variables based on the analysis of ASAS-SN light curves: GSD J11630570-510306, V593 Sco and TYC 6939-678-1. These systems have orbital periods between 10 and 20 days and long cycles between 300 and 600 days.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
