THE ASTRONOMER Electronic Circular No 798 1993 Dec 19 14.16UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP,England. Telephone/FAX(0256)471074 Int:+44256471074 TELEX: 9312111261 Answerback: TA G TELECOM GOLD: 10074:MIK2885 GMH at UK.AC.RUTHERFORD.STARLINK.ASTROPHYSICS STARLINK: RLSAC::GMH GMH at UK.AC.CAM.ASTRONOMY.STARLINK STARLINK: CAVAD::GMH ------------------------------------------------------------------- OJ 287 In TA Vol 30 No 354 p140 [1993], we provided details and a chart of this object and appealed for observations. Mark Kidger, Instituto d'Astrofisica d'Canarias has faxed an update. He wishes to stress that the campaign on this object is international and not merely from 'Finnish Astronomers' as an earlier message received by TA suggested. His report follows: Recent observations of this object have shown a major increase in brightness although with large oscillations over a few hours. After staying more or less around V=16 since the decline of the 1983 outburst, it has reached a magnitude of around V=15.3, with occasional much brighter observations. Some recent reports have made the quasar brighter than magnitude 15 for the first time since 1984. The first report of considerable brightening was on December 6.13UT, V=14.5 (Kidger, Teide Observatory, IAC-80, 0.82-m reflector + CCD) which included a 0.2 magnitude brightening in about one hour! On the following night it had faded considerably again (Dec 7.21UT, V=15.2, Kidger). Derek Wills, University of Texas, relayed a report from Janet Mattei, Director of AAVSO, that an observer of that group had estimated it at V=14.6 on Dec 8/9. The latest visual data shows that the magnitude is slightly fainter again (Dec 14.0, v=15.1, Poyner). The upward trend in the data and occasional bright points suggest that a major outburst has started. This was predicted to occur in late July or early August 1994 on the basis of an 11.6-year period estimated by Sillanpaa et al. (Ap.J., 325, 628 [1988]). More recently Kidger et al. (A&A, 164, 32 [1992]) found that an 11.35 year period is a better fit to the data. The discovery of previously unpublished Russian data that covers two outbursts in the 1940s and 1950s greatly strengthens this conclusion that the period is rather shorter tha previously estimated. Based on this new data (Kidger, 1993, Proposal to the Canary Islands Observatories International Scientific Committee) suggested a most probable date of outburst in early March 1994. The proposed mechanism is the binary period of two supermassive black holes in the nucleus of OJ287. It is imperative that confirmation be obtained as rapidly as possible as to whether this is a genuine outburst or simply violent activity in the light curve. It is urgently requested that observers, especially with CCD, but also visual and photographic observers at dark sites, monitor this object as often as possible. Please note that its extreme variability on very short timescales (occasionally more than 0.5 magnitudes in a few hours) makes it important that several data points are obtained per night. Results should be passed to Gary Poyner or Guy Hurst for urgent relay to participating observatories. All data received will be used in publications in professional journals at a later date with credit to individual observers. V542 CYGNI Tony Vanmunster, Belgium reports an outburst of V542 Cyg, a star on the recurrent objects programme. The event has been confirmed by Gary Poyner, Birmingham, UK and Bill Worraker, Didcot, UK: 1993 Dec 4.930UT, 13.6 (Vanmunster, 0.35-m reflector) 7.786 , 13.9 (Poyner, 0.40-m reflector) 7.875 , 13.9 (Worraker, 0.26-m reflector)