Circular No. 6683 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science) URL http://cfa-www.harvard.edu/cfa/ps/cbat.html Phone 617-495-7244/7440/7444 (for emergency use only) GRB 970616 V. Connaughton, National Academy of Sciences/National Research Council and Marshall Space Flight Center (MSFC); R. M. Kippen, R. Preece, and G. N. Pendleton, University of Alabama at Huntsville and MSFC; and S. D. Barthelmy, Universities Space Research Association (USRA) and Goddard Space Flight Center (GSFC), report for the BATSE team: "The transient x-ray XTE source reported below by Marshall et al. lies in the error box of a gamma-ray burst seen by BATSE on June 16.757 UT. The Rapid Burst Reponse location, which was distributed through the GRB Coordinates Network/BATSE Coordinates Distribution Network, 20 min after the initial trigger, was R.A. = 1h21m51s, Decl. = -7 09'.4 (equinox 2000.0), with a 1-sigma error radius of 0.3-degree statistical and about 2 deg systematic. The burst was multipeaked, with a total duration of about 200 s. A maximum flux of 23.8 +/- 0.5 photons cmE-2 sE-1 (above 20 keV) was measured 90 s after the trigger time, placing this event in the brightest 2 percent of all BATSE bursts. Its total fluence above 20 keV is estimated to be 4.01 +/- 0.14 x 10E-5 erg cmE-2." F. E. Marshall, GSFC; T. Takeshima, and S. D. Barthelmy, USRA and GSFC; C. R. Robinson, USRA and MSFC; and K. Hurley, University of California at Berkeley, report the detection of an x-ray afterglow for the gamma-ray burst detected with BATSE on June 16.7568 UT. Scanning observations with the Proportional Counter Array on the Rossi X-ray Timing Explorer (RXTE) 4.0 hr after the burst revealed a source at R.A. = 1h18m.9 +/- 0m.7 (90-percent statistical confidence), Decl. = -5 30' +/- 18' (equinox 2000.0) with a countrate of 4.5 +/- 1.6 counts/s or 1.1 x 10E-11 erg sE-1 cmE-2 in the band 2-10 keV. It is the brightest source detected within the 2-deg BATSE error circle, and it also overlaps the preliminary inter-planetary network (IPN) annulus determined from the time difference in the BATSE and Ulysses detections. The IPN annulus has a radius of 49.808 deg, is centered at R.A. = 22h10m30s, Decl. = -27o24'.8, and has a full width of 4'.6. An annulus with a smaller width will be available after further processing. The intersection of the error regions has corners at 1h19m.6, -5 49'; 1h19m.6, -5 40'; 1h18m.4, -5 12'; 1h18m.2, -5 16'. A subsequent RXTE observation on June 18.08 detected no significant flux from this position, with a preliminary 90-percent confidence upper limit of 2.5 counts/s. (C) Copyright 1997 CBAT 1997 June 19 (6683) Daniel W. E. Green