J/PASP/131/H4201 Variable stars in Southern polar region (Ratzloff+, 2019)
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., Trifonov T.
<Publ. Astron. Soc. Pac., 131, h4201 (2019)>
=2019PASP..131h4201R 2019PASP..131h4201R (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Binaries, eclipsing
Abstract:
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 160000 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 1.7RJ 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 (0.06-0.37M☉)
secondaries with K-dwarf primaries, strong candidates for precision
mass-radius measurements.
Description:
All eclipsing binary and variable discoveries were detected in a
transit search of the polar region (declinations -75 to -90°). The
observations were taken from Au- gust 9, 2016 to April 4, 2017. The
exposure time was 120s through a Sloan-g filter and each source
typically had 16000 epochs.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table10.dat 95 135 Variable Star discoveries
table11.dat 95 159 Eclipsing Binary discoveries
--------------------------------------------------------------------------------
See also:
II/336 : AAVSO Photometric All Sky Survey (APASS) DR9 (Henden+, 2016)
J/PASP/131/G5001 : New variable stars and eclipsing binaries (Ratzloff+, 2019)
Byte-by-byte Description of file: table10.dat table11.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 22 A22 --- ESID ES ID (EVRJHHMMSS.ss+DDMMSS.s)
24- 31 I8 --- APASS ?=- APASS ID
33- 40 F8.4 deg RAdeg Right ascension (J2000)
42- 49 F8.4 deg DEdeg Declination (J2000)
51- 55 F5.2 mag Vmag ?=- V magnitude
57- 61 F5.2 --- RPM ?=- Reduced proper motion
63- 67 F5.2 mag B-V ?=- Color difference (B-V) which we use to
estimate the star size and spectral type
(see Section 4.2.1)
69- 73 A5 --- Size Star size (ms or giant)
75- 79 A5 --- SpType Spectral type
81- 89 F9.4 h Per Period
91- 95 F5.3 mag Amp Amplitude of the variability
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 14-Aug-2019