MASTER OT J072007.30+451611.6: Cataclysmic Variable with an Extreme Hot Spot
ATel #11626; D. Denisenko (Sternberg Astronomical Institute, Lomonosov Moscow State University)
on 9 May 2018; 21:11 UT
Credential Certification: Denis Denisenko (d.v.denisenko@gmail.com)
Subjects: Optical, Cataclysmic Variable, Variables
MASTER team has reported an unusual object MASTER OT J072007.30+451611.6 in ATel #11620 (T. Pogrosheva et al.). The object was observed at 17.0-17.2m during 9 minutes from 22:15:26 to 22:24:30 UT on 2018-04-26, but was below the detection limit (18.8m) 45 minutes before the first positive observation and 43 minutes after the last one.
As noted by S. Otero in AAVSO VSX entry, MASTER OT J072007.30+451611.6 has an X-ray counterpart XMMSL2 J072007.4+451615. It was observed by Catalina Sky Survey (A. Drake et al., 2009, ApJ Vol. 696, p. 870) as CSS_J072007.4+451615, but not detected as a transient. The CSS light curve is showing the large amplitude variability from 16.6 to 21.4m (unfiltered with V zero point).
Uploading the CRTS data to Period Search Service by Kirill Sokolovsky has provided the best period value of 0.0627887 d (1.50693 hr, or 90.4157 min - very close to the interval between non-detections by MASTER at 21:30:39 and 23:07:32 UT). The light curve folded with this period is available at http://scan.sai.msu.ru/~denis/J072007+451611-phased_LC.gif It is definitely that of a cataclysmic variable with the large contribution from the hot spot, most likely a polar. One can even suspect the alternating low and high states, though not as obvious ones as in CSS_J071126.0+440405 = V808 Aur located within 2 degree of MASTER OT J072007.30+451611.6. However, V808 Aur is an eclipsing polar, and the amplitude of orbital variations outside the eclipses is about 2 magnitudes. There appears to be no eclipses in MASTER OT J072007.30+451611.6, but the phased light curve amplitude is really huge (about 3 magnitudes). This is a remarkable cataclysmic binary system with an extreme contribution from the hot spot. Checking the archival data for the low states and follow up monitoring is encouraged.
Period Search Service by Kirill Sokolovsky
