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تسجيل مستخدم جديدThe ASAS-SN Catalog of Variable Stars III: Variables in the Southern TESS Continuous Viewing Zone
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The All-Sky Automated Survey for Supernovae (ASAS-SN) provides long baseline (${sim}4$ yrs) light curves for sources brighter than V$lesssim17$ mag across the whole sky. The Transiting Exoplanet Survey Satellite (TESS) has started to produce high-quality light curves with a baseline of at least 27 days, eventually for most of the sky. The combination of ASAS-SN and TESS light curves probes both long and short term variability in great detail, especially towards the TESS continuous viewing zones (CVZ) at the ecliptic poles. We have produced ${sim}1.3$ million V-band light curves covering a total of ${sim}1000 , rm deg^2$ towards the southern TESS CVZ and have systematically searched these sources for variability. We have identified ${sim} 11,700$ variables, including ${sim} 7,000$ new discoveries. The light curves and characteristics of the variables are all available through the ASAS-SN variable stars database (https://asas-sn.osu.edu/variables). We also introduce an online resource to obtain pre-computed ASAS-SN V-band light curves (https://asas-sn.osu.edu/photometry) starting with the light curves of the ${sim}1.3$ million sources studied in this work. This effort will be extended to provide ASAS-SN light curves for ${sim}50;$million sources over the entire sky.
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The All-Sky Automated Survey for Supernovae (ASAS-SN) provides long baseline (${sim}4$ yrs) light curves for sources brighter than V$lesssim17$ mag across the whole sky. As part of our effort to characterize the variability of all the stellar sources
visible in ASAS-SN, we have produced ${sim}30.1$ million V-band light curves for sources in the southern hemisphere using the APASS DR9 catalog as our input source list. We have systematically searched these sources for variability using a pipeline based on random forest classifiers. We have identified ${sim} 220,000$ variables, including ${sim} 88,300$ new discoveries. In particular, we have discovered ${sim}48,000$ red pulsating variables, ${sim}23,000$ eclipsing binaries, ${sim}2,200$ $delta$-Scuti variables and ${sim}10,200$ rotational variables. The light curves and characteristics of the variables are all available through the ASAS-SN variable stars database (https://asas-sn.osu.edu/variables). The pre-computed ASAS-SN V-band light curves for all the ${sim}30.1$ million sources are available through the ASAS-SN photometry database (https://asas-sn.osu.edu/photometry). This effort will be extended to provide ASAS-SN light curves for sources in the northern hemisphere and for V$lesssim17$ mag sources across the whole sky that are not included in APASS DR9.
The variable stars in the VSX catalog are derived from a multitude of inhomogeneous data sources and classification tools. This inhomogeneity complicates our understanding of variable star types, statistics, and properties, and it directly affects at
tempts to build training sets for current (and next) generation all-sky, time-domain surveys. We homogeneously analyze the ASAS-SN V-band light curves of ${sim}412,000$ variables from the VSX catalog. The variables are classified using an updated random forest classifier with an $F_1$ score of 99.4% and refinement criteria for individual classifications. We have derived periods for ${sim}52,000$ variables in the VSX catalog that lack a period, and have reclassified ${sim} 17,000$ sources into new broad variability groups with high confidence. We have also reclassified ${sim} 94,000$ known variables with miscellaneous/generic classifications. The light curves, classifications, and a range of properties of the variables are all available through the ASAS-SN variable stars database (https://asas-sn.osu.edu/variables). We also include the V-band light curves for a set of ${sim}4,000$ rare variables and transient sources, including cataclysmic variables, symbiotic binaries and flare stars.
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.
The Transiting Exoplanet Survey Satellite (TESS) will provide high precision time-series photometry for millions of stars with at least a half-hour cadence. Of particular interest are the circular regions of 12-degree radius centered around the eclip
tic poles that will be observed continuously for a full year. Spectroscopic stellar parameters are desirable to characterize and select suitable targets for TESS, whether they are focused on exploring exoplanets, stellar astrophysics, or Galactic archaeology. Here, we present spectroscopic stellar parameters ($T_{rm eff}$, $log g$, [Fe/H], $v sin i$, $v_{rm micro}$) for about 16,000 dwarf and subgiant stars in TESS southern continuous viewing zone. For almost all the stars, we also present Bayesian estimates of stellar properties including distance, extinction, mass, radius, and age using theoretical isochrones. Stellar surface gravity and radius are made available for an additional set of roughly 8,500 red giants. All our target stars are in the range $10<V<13.1$. Among them, we identify and list 227 stars belonging to the Large Magellanic Cloud. The data were taken using the the High Efficiency and Resolution Multi-Element Spectrograph (HERMES, R $sim 28,000$) at the Anglo-Australian Telescope as part of the TESS-HERMES survey. Comparing our results with the TESS Input Catalog (TIC) shows that the TIC is generally efficient in separating dwarfs and giants, but it has flagged more than hundred cool dwarfs ($T_{rm eff}< 4800$ K) as giants, which ought to be high-priority targets for the exoplanet search. The catalog can be accessed via http://www.physics.usyd.edu.au/tess-hermes/ , or at MAST via https://archive.stsci.edu/prepds/tess-hermes/ .
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 sour
ces 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.
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