THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS 25 Birch Street, Cambridge, MA 02138 USA INTERNET: aavso@aavso.org Tel. 617-354-0484 FAX 617-354-0665 AAVSO ALERT NOTICE 253 (January 28, 1999) SPECIAL and UNIQUE OPTICAL MONITORING REQUEST: 1522+45 GRB 990123 - GAMMA-RAY BURSTER EVENT WITH BRIGHT OPTICAL COUNTERPART We have been informed by the Central Bureau for Astronomical Telegrams (IAU Circulars 7094, 7095, 7100), Dr. Howard Bond, Space Telescope Science Institute, and Dr. Chryssa Kouveliotou, NASA Marshall Space Flight Center and BATSE Team member, that a gamma-ray burst accompanied by an unprecedentedly bright optical flash has been detected by the Burst and Transient Source Experiment (BATSE) instrument aboard the Compton Gamma Ray Observatory satellite on January 23.40764 UT, and by the Gamma Ray Burst Monitor instrument aboard the BeppoSAX satellite on January 23.40780 UT. The BeppoSAX Wide Field Camera 1 also detected the burst and observed the x-ray counterpart. Interested astronomers were immediately alerted via BATSE's Gamma Ray Burst Coordinates Network. C. W. Akerlof and T. A. McKay, University of Michigan, report on behalf of the Robotic Optical Transient Search Experiment (ROTSE) collaboration (Michigan/Los Alamos National Laboratory/Lawrence Livermore National Laboratory) that within 30 seconds, the ROTSE-I telephoto camera array at Los Alamos, NM, which uses an unfiltered broadband CCD, was observing the location of the gamma-ray burst, and it observed a very bright, rapidly-fading object. Six observations made between January 23.407851 and January 23.414677 (approximately 10 minutes) showed the object brighten from V magnitude 11.82 to 8.95 and then fade to 14.53. Images of these six observations may be seen at http://www.umich.edu/~rotse/gifs/grb990123/990123.gif. Additional observations of the immediate region around this event, obtained by numerous astronomers at several institutions (see IAU Circulars 7094, 7095, 7096, 7098, 7099, 7100), indicate that the optical counterpart of the gamma-ray burst continued to fade very quickly, reaching R magnitude approximately 18 in less than 4 hours and fainter than R magnitude 19 in less than another 5 hours, and fainter than R magnitude 21 in another 24 hours. The position of the optical counterpart was reported by S. C. Odewahn, J. S. Bloom, and S. R. Kulkarni, California Institute of Technology, on behalf of the Caltech-NRAO-CARA GRB Collaboration (IAU Circular 7094) as: R.A. = 15h 25m 30.5s Decl. = +44 degrees 46' 00" (2000) This event is potentially a very important one for our observers because the bright optical flash may occur again once or several times, and so the area should be monitored. As Dr. Bond explains, "...An exciting aspect of this object is the suggestion by S.G. Djorgovski et al. that GRB 990123 was gravitationally lensed (which might account for the extraordinary apparent luminosity). This raises the possibility, emphasized by E. Turner, that the gamma-ray and optical bursts may recur in the next few days to months, due to lensing time delays along different paths to the Earth. It would thus be very worthwhile for AAVSO members to monitor this position constantly, even with small telescopes or binoculars, to search for such repeated optical transients, which could in principle even reach to brighter than 8th magnitude for a few seconds. Precise times, magnitude estimates, and other details should be determined for any flashes that are seen." All AAVSO observers - visual observers, photoelectric photometrists, and CCD photometrists - are strongly urged to monitor this location as much as possible over the coming months, and to report any sudden brightening to AAVSO Headquarters immediately. If you see any brightening at the position of GRB 990123, please monitor it constantly and report the timing of your observations very accurately, to the fourth decimal of the J.D. We recommend that you have a tape recorder at hand when you are observing and record your observations into the tape recorder, for the sake of speed. Accompanying is an AAVSO preliminary "d" scale chart prepared by C. Scovil using Tycho photometry, and approximate V magnitudes derived from USNO A2.0 magnitudes via the vsnet chart for this object. Anyone interested in being alerted by the Gamma Ray Burst Coordinates Network should write to Dr. Scott Barthelmy at scott@milkyway.gsfc.nasa.gov. The following websites with information on this object may also be of interest to our observers: http://science.msfc.nasa.gov http://astro.caltech.edu/~jsb/GRB/grb990123.html http://gcn.gsfc.nasa.gov/gcn/gcn3/199.gcn3 CHARTS AVAILABLE ON AAVSO WEB AND FTP SITES Electronic copies of the AAVSO chart of GRB 990123 mentioned in this Alert Notice are available through our web site at the following address: http://www.aavso.org All of these charts may also be obtained directly from our FTP site: ftp.aavso.org (198.116.78.5), in /alerts/alert253/ The answering machine at AAVSO Headquarters is on nights and weekends for your convenience. Please call our charge-free number (888-802-STAR = 888-802-7827) to report your observations. We also encourage observers to send observations by fax to 617-354-0665 or by e-mail through the Internet to observations@aavso.org. Many thanks for your valuable astronomical contributions and your efforts. Good observing! Janet A. Mattei Director