------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 2372 2007 Sep 05 11.31UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074 INTERNET: GUY@TAHQ.DEMON.CO.UK Backup: gmh@wdcc1.bnsc.rl.ac.uk WORLD WIDE WEB http://www.theastronomer.org ------------------------------------------------------------------- HS 2331+3905 Hiroyuki Mehara, VSNET Collaboration Team reports that the WZ Sge-type dwarf nova candidate HS2331+3905 is in outburst: 2007 Sept 04.77519UT, 14.59V. This object is located at RA 23h34m01.55s DEC +39 21' 42.9"(J2000) M. Uemura, A. Arai, M. Sasada, O. Nagae on behalf of the KANATA team Hiroshima University report on VSNET that they have confirmed the outburst: 2007 Sept 04.79824UT, 14.4V. According to AAVSO Special Notice No. 63, the variable was last reported as fainter than 14.6 on JD 2454347.3931 (2007, Sept 3, 21h26m UT). Evidently HS 2331+3905 has never been observed in outburst before. The Bulletin adds that this object is known to have a very short orbital period consistent with the WZ Sge class, and is also known to have a pulsating white dwarf primary. It may also have a brown dwarf secondary, making this a very unique object. The AAVSO indicate a chart can be obtained by entering the coordinates above into VSP: http://www.aavso.org/observing/charts/vsp/index.html Gary Poyner, Birmingham, adds: You will have seen from the above that the suspected UGWZ star HS2331+3905 has been detected in outburst. On Sep 3.192 UT, I have a CCD observation made with the Bradford Robotic Telescope showing it at minimum at 16.24 (unfiltered). This is the first outburst detected in this system so far. Dr. Boris Gaensicke comments on his HQSCV web page that it is a grazing eclipsing system which could reach magnitude 10. Needless to say, this outburst should be treated as priority with CCD time series observers. Eddy Muyllaert, Belgium, reports a visual observation suggesting the object is still brightening: 2007 Sept 04.8431UT, 13.9v. Martin Nicholson, UK reports: 2007 Sept 5.164UT, 10.408V Hiroyuki Maehara, VSNET Collaboration Team, reports that he has performed time-series photometry just after the outburst detection. The data show rapid brightening trend at a rate of 10.5 mag/day! This star is in a initial stage of a possible super-outburst. Dr. Boris Gaensicke, Department of Physics, University of Warwick, England indicates he has the first few spectra of HS2331+3905 in outburst: weak Hbeta/gamma, which is broad and double-peaked with deep central absorptions. The last spectrum looks as if they are turning over into complete absorption lines. No sign of HeII 4686. For those of you who are unfamiliar with this star: it is a 81-min orbital period CV with a grazing eclipse, very similar to WZ Sge. But it holds a series of other features, (1) its white dwarf is pulsating with typical periods of ~5min (2) its white dwarf is spinning with a period of 1.12min (3) it probably has permanent superhumps in quiescence (4) most amazing: the Balmer emission lines show a ~3.5h radial velocity variation in quiescence, that is in no way related to the orbital period! A full account on this fantastic object is given in http://arxiv.org/abs/astro-ph/0410223 Guy M Hurst