------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 2909 2013 Apr 27 12.06UT 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 130427A: VERY BRIGHT OUTBURST (APPEAL) EDITOR: PLEASE, IN PARTICULAR, READ THE FINAL PARAGRAPH. A. Maselli (INAF-IASFPA) et. al., report (GCN 14448) on behalf of the Swift Team: At 07:47:57 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 130427A. Swift slewed immediately to the burst. The BAT on-board calculated location is RA(J2000) 11h 32m 33s DEC(J2000) = +27d 41' 29" with an uncertainty of 3 arcmin. The XRT found a bright, uncatalogued X-ray source located at: RA(J2000) 11h 32m 32.69s DEC(J2000) = +27d 42' 46.4" with an uncertainty of 4.7 arcseconds. UVOT took a finding chart exposure of 150 seconds with the White filter starting 147 seconds after the BAT trigger. A blurred bright source appears to be located near the XRT position in the initial 2.7'x2.7' sub-image. This is an extremely bright burst in all three instruments, and it was also seen by Fermi/GBM. D. A. Perley (Caltech) reports (GCN 14449) on behalf of a larger collaboration: The Palomar 60-inch telescope automatically responded to GRB 130427A (Maselli et al., GCN 14448) and began taking observations at 07:52:22 UT (4.42 minutes after the BAT trigger). A series of 60-second images were taken in r, i, and z filters; observations are still ongoing. Inspection of individual frames shows no detection of an optical transient consistent with the XRT position to approximately r > 20.6 mag, i > 20.7 mag, z > 19.7 mag. L. Elenin (KIAM), et. al, (GCN 14450): we started observation of the field of the Swift GRB 130427A with 0.45-m telescope of ISON-NM observatory on Apr. 27, 07:50:17UT. On the first images of 30-s exposure we identified very bright optical counterpart of GRB 130427A (Maselli et al., GCN 14448) at about 12m in the initial images. A. Melandri (INAF-OAB), et. al., report (GCN 14452) on behalf of a larger collaboration: The 2-m Faulkes Telescope North robotically followed up GRB130427A (SWIFT trigger 554620, Maselli et al. GCN 14448 ) starting 4.3 min after the GRB trigger time. We detect a bright fading source at the position reported by Elenin et al. (GCN 14450), Perley (GCN 14451) with R ~11.5 mag. We note also a faint, 21-mag, underlying source visible in SDSS images that may suggest this GRB is nearby with a bright host galaxy. D. A. Perley (Caltech) and S. B. Cenko (UC Berkeley) report (11h52mUT): We have continued observations (GCN 14456) with the Palomar 60-inch telescope until the field set. Relative to SDSS reference stars in the field, in some select recent images we estimate afterglow magnitudes of: r' = 14.86 mag (t = 1.40 hours) r' = 15.32 mag (t = 2.31 hours) r' = 15.55 mag (t = 3.10 hours) This is brighter (by about 1 mag) than any other Swift burst as measured at similar epoch, though still significantly fainter than GRB 030329 which reached approximately 13 mag at 0.1 day. The rate of fading corresponds to a relatively shallow decay index of approximately alpha~-0.85, suggests that this AFTERGLOW WILL REMAIN BRIGHT FOR AN EXTENDED PERIOD. WORLDWIDE SMALL-TELESCOPE FOLLOW-UP (INCLUDING BY AMATEURS) IS STRONGLY ENCOURAGED. Guy M Hurst