Jeremy Shears, Robert Koff, Gianluca Masi, Enrique de Miguel, Ian Miller, George Roberts, Richard Sabo, William Stein, Joseph Ulowetz
GALEX J215818.5+241924 was initially identified as a possible nova in Pegasus. We report unfiltered photometry of the object which revealed the presence of superhumps, with peak-to-peak amplitude of up to 0.22 magnitudes, diagnostic of it being a member of the SU UMa family of dwarf novae. The outburst amplitude was 4.3 magnitudes and it lasted at least 10 days, with a maximum brightness of magnitude 14.3. We determined the mean superhump period from our first 5 nights of observations as Psh = 0.06728(21) d. However analysis of the O-C residuals showed a dramatic evolution in Psh during the outburst. During the first part of the plateau phase the period increased with dPsh/dt = +2.67(15) \times 10-4. There was then an abrupt change following which the period decreased with dPsh/dt = -2.08(9)\times10-4. We found a signal in the power spectrum of the photometry which we interpret as the orbital signal with Porb = 0.06606(35) d. Thus the superhump period excess was epsilon = 0.020(8), such value being consistent with other SU UMa systems of similar orbital period.
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http://arxiv.org/abs/1205.0898
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