[vsnet-alert 11988] (fwd) 1942 superoutburst of OT J213806.6+261957 (resend)

[Taichi Kato]

ATEL #2619                                                           ATEL #2619

Title:          1942 superoutburst of OT J213806.6+261957
Author: Rene Hudec (Astronomical Institute AS CR Ondrejov)
Queries:        rhudec at asu.cas.cz
Posted: 13 May 2010;  22:56  UT
Subjects:       Optical, Cataclysmic Variables, Transients

The optical transient/cataclysmic variable in Pegasus, reported in CBET
2273 and CBET 2275 (designated VSX J213806.5+261957 or OT J213806.6+261957)
was detected in the extended study of Sonneberg Observarory Archival Sky
Patrol Plates (more than 3000 plates analyzed, taken during the years 1928
to 2004) in another (historical) large optical outburst (peak on 1942 Nov
30) at mag(B)=9.8 (+-0.5). The star was found in a superoutburst from 1942
Nov 30 till 1942 Dec 11, being fainter than mag(B) 13 on 1942 Nov 10 (and
before this date)  and on 1942 Dec 28 (and after this date). This limits
the superoutburst duration to be between 12 and 46 days.   The object was
found to be fainter than mag(B) 13-14 (limiting magnitude) on all other
investigated plates confirming that the superoutbursts of this star are
extremely rare.       This gives a very long recurrence time of the superoutbursts,
about 67 years, however we cannot exclude that another superoutburst occurred
which was not covered by Sonneberg plates due to seasonal and/or weather
gap and hence escaped detection.        The detection of another superoutburst
confirms that OT J213806.6+261957 is indeed a WZ Sge type dwarf nova, i.e.
a short-period cataclysmic variable with a low accretion rate and very
rare and large-amplitude superoutbursts (#ATel 2605).