Shears, JeremyKoff, RobertMasi, G.Miguel Agustino, Enrique deMiller, IanRoberts, GeorgeSabo, RichardStein, WilliamUlowetz, Joseph2023-03-082023-03-082013Shears, J., Koff, R., Masi, G., de Miguel, E., Miller, I., Roberts, G., Sabo, R., Stein, W., & Ulowetz, J. (2012). The first confirmed superoutburst of the dwarf nova GALEX J215818.5+241924 (Version 2). arXiv. https://doi.org/10.48550/ARXIV.1205.0898https://hdl.handle.net/10272/21760In 2011 October an optical transient was reported in Pegasus as a possible nova. The object had an ultraviolet counterpart, GALEX J215818.5+241924. In this paper we present follow-up 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 4.6 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) x 10-4. There was then an abrupt change following which the period decreased with dPsh/dt = -2.08(9)10-4. We found a signal in the power spectrum of the photometry which we tentatively interpret as the orbital signal with Porb = 0.06606(35) d. Thus the superhump period excess was ε = 0.020(8), such value being consistent with other SU UMa systems of similar orbital period.engAtribución-NoComercial-SinDerivadas 3.0 Españahttp://creativecommons.org/licenses/by-nc-nd/3.0/es/journal article10.48550/ARXIV.1205.0898open access22 Física