------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 2559 2009 Jun 18 19.41T 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 ------------------------------------------------------------------- GRB 090618 BRIGHT AFTERGLOW On GCN Circular 9512, P. Schady (MSSL-UCL) et. al., report on behalf of the Swift Team: At 08:28:29 UT on 2009 June 18, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090618 (trigger=355083). Swift slewed immediately to the burst. The BAT on-board calculated location as: RA(J2000) = 19h 36m 05s; Dec(J2000) = +78d 21' 13" with an uncertainty of 3 arcmin. The XRT began observing the field at 08:30:30.8 UT, 120.9 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at: RA(J2000) = 19h 35m 57.52s; Dec(J2000) = +78d 21' 27.3" with an uncertainty of 4.7 arcseconds. UVOT took a finding chart exposure of 150 seconds with the White filter starting 128 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at: RA(J2000) = 19:35:58.69; DEC(J2000) = +78:21:24.3 On GCN Circular 9513, S. B. Cenko (UC Berkeley) reports on behalf of a larger collaboration: We have imaged the field of GRB090618 (Swift trigger 355083) with the automated Palomar 60-inch telescope beginning at 08:30 UT on 18 June 2009 (approximately 2 minutes after the burst). At the edge of the XRT error circle we detect a bright point source with coordinates: RA: 19:35:58.68 Dec: +78:21:24.4 (J2000.0) Using several SDSS stars in the field as reference, we estimate an initial magnitude of r' ~ 13.8. Given the brightness of the source, we consider it highly likely to be the optical afterglow of GRB090618. D. A. Perley reports on behalf of the KAIT GRB team vioa GCN 9514: The Katzman Automatic Imaging Telescope (KAIT) responded to GRB 090618 and began taking data at 08:31:10 (UT). A bright (~14th magnitude) optical afterglow is visible in the initial set of exposures at the following position: RA 19:35:58.80 Dec +78:21:25.5 In GCN 9517 a follow-up report from the KAIT team: We have analyzed the KAIT observations on GRB 090618 (GCN 9512) as reported in GCN 9514. Selected photometry, all unfiltered calibrated to the R band via USNO B1: t_mid(seconds) exp(s) mag mag_err --------------------------------------- 76 2.0 13.61 0.03 92 2.0 13.99 0.04 117 2.0 13.50 0.03 237 20.0 14.02 0.02 436 20.0 14.73 0.02 729 20.0 15.26 0.02 2601 20.0 16.22 0.02 7329 120.0 17.02 0.03 Guy M Hurst