Publ. Astron. Soc. Pac., 131, part no 8, 4201-84201 (2019/August-0)
Variables in the Southern polar region Evryscope 2016 data set.
RATZLOFF J.K., CORBETT H.T., LAW N.M., BARLOW B.N., GLAZIER A., HOWARD W.S., FORS O., DEL SER D. and TRIFONOV T.
Abstract (from CDS):
The regions around the celestial poles offer the ability to find and characterize long-term variables from ground-based observatories. We used multi-year Evryscope data to search for high-amplitude (≃5% or greater) variable objects among 160,000 bright stars (mv < 14.5) near the South Celestial Pole. We developed a machine-learning-based spectral classifier to identify eclipse and transit candidates with M-dwarf or K-dwarf host stars, and potential low-mass secondary stars or gas-giant planets. The large amplitude transit signals from low-mass companions of smaller dwarf host stars lessens the photometric precision and systematics removal requirements necessary for detection, and increases the discoveries from long-term observations with modest light-curve precision among the faintest stars in the survey. The Evryscope is a robotic telescope array that observes the Southern sky continuously at 2-minute cadence, searching for stellar variability, transients, transits around exotic stars and other observationally challenging astrophysical variables. The multi-year photometric stability is better than 1% for bright stars in uncrowded regions, with a 3σ limiting magnitude of g = 16 in dark time. In this study, covering all stars 9 < mv < 14.5, in declinations -75° to -90°, and searching for high-amplitude variability, we recover 346 known variables and discover 303 new variables, including 168 eclipsing binaries. We characterize the discoveries and provide the amplitudes, periods, and variability type. A 1.7 RJ planet candidate with a late K-dwarf primary was found and the transit signal was verified with the PROMPT telescope network. Further follow-up revealed this object to be a likely grazing eclipsing binary system with nearly identical primary and secondary K5 stars. Radial-velocity measurements from the Goodman Spectrograph on the 4.1 meter SOAR telescope of the likely lowest-mass targets reveal that six of the eclipsing binary discoveries are low-mass (.06-.37 M☉) secondaries with K-dwarf primaries, strong candidates for precision mass-radius measurements.
© 2019. The Astronomical Society of the Pacific. All rights reserved.
VizieR on-line data:
<Available at CDS (J/PASP/131/h4201): table10.dat table11.dat>
Tables 8-11: EVR JHHMMSS.ss+DDMMSS.s N=6+3+135+159.
Status at CDS
All or part of tables of objects could be ingested in SIMBAD with priority 2.
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