Superoutburst of Cataclysmic Variable B8 in NGC 6791
ATel #3507; P. Garnavich (Notre Dame), M. Still (NASA Ames/BAERI), T. Barclay (NASA Ames/BAERI)
on 24 Jul 2011; 17:46 UT
Credential Certification: Peter Garnavich (pgarnavi@gmail.com)
Subjects: Optical, Cataclysmic Variable
The Kepler Mission observed a superoutburst from the cataclysmic
variable B8 in NGC 6791 in the newly released quarter 8 data. The
super-outburst began on BJD 2455592 and lasted two weeks. Superhump
oscillations are clearly seen at maximum and during the decline.
B8 in the old, metal-rich cluster NGC 6791 was spectroscopically
confirmed as a cataclysmic variable (CV) by Kaluzny et al. (1997,
ApJ, 419, 153) but its orbital period has not been determined.
Ground-based observations shows B8 spends most of its time
near V=21 mag with two magnitude outbursts consistent with a dwarf
nova classification (Mochejska, Stanek, & Kaluzny 2003, AJ, 125, 3175).
Monitoring of B8 by Kepler using a 1-min cadence in Cycle 2 confirms
the 1.5 magnitude outbursts lasting two to three days and now
show a superoutburst with an amplitude of 3 magnitudes. The
average superhump period is 2.097+/-0.003 hours indicating
an orbital period just under the period gap and that B8 belongs
to the SU UMa class of CV. In the first two days of the outburst
the superhump peak-to-peak amplitude is 0.3 mag and the period is
2.109+/-0.003 hours. The superhump period decreases with time
at a rate of P-dot=2e-4.
