//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21039 SUBJECT: Swift Trigger 750096 is probably a noise fluctuation DATE: 17/04/26 23:00:26 GMT FROM: David Palmer at LANL A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Swift Team: At 22:44:21 UT, the Swift Burst Alert Telescope (BAT) detected an image peak in the vicinity of a nearby galaxy (trigger=750096). Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 184.880, +5.656 which is RA(J2000) = 12h 19m 31s Dec(J2000) = +05d 39' 21" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows no significant activity. The XRT began observing the field at 22:46:18.1 UT, 117.1 seconds after the BAT trigger. No source was detected in 513 s of promptly downlinked data. UVOT took a finding chart exposure of 250 seconds with the U filter starting 117 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image processing FAILED because of no aspect solution. Results from the list of sources generated on-board are not available at this time. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02. Due to the low significance of the image peak (5.80 sigma), the large distance to the potential associated source (7.7 arcminutes), the lack of activity in the BAT count rates, and the non-detection by XRT, we believe that this is merely a noise fluctuation in the image plane and not an astrophysical source. This trigger, like the earlier Trigger #750044, was the result of a triggering strategy that locally depresses the threshold significance in the vicinity of known sources and nearby galaxies in order to gain greater sensitivity to such sources (at the expense of a higher proportion of false triggers). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21040 SUBJECT: GRB170426.95 MASTER-Net OT detection DATE: 17/04/27 00:54:16 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.V.Chazov, D. Vlasenko Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory K. Ivanov, O. Gres, N.M. Budnev, S. Yazev, O. Chuvalaev, V. Poleshchuk Irkutsk State University V. Yurkov, A. Gabovich, Yu. Sergienko Blagoveschensk Educational State University, Blagoveschensk R. Podesta, Carlos Lopez and F. Podesta Observatorio Astronomico Felix Aguilar (OAFA) Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias D. Buckley, S. Potter, A. Kniazev, M. Kotze South African Astronomical Observatory MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Kislovodsk was pointed to the GRB170426.95 894 sec after notice time and 982 sec after trigger time at 2017-04-26 23:00:43 UT. On our 6-th (180s exposure) set we found 1 optical transient within SWIFT error-box (ra=184.879 dec=5.65583 r=0.066667) brighter then 18.91. T-Tmid Date Time Expt. Ra Dec Mag ---------|---------------------|-------|-----------------|-----------------|------- 1072 2017-04-26 23:00:43 180 (12h 19m 39.17s , +05d 37m 42.5s) 16.08 The 5-sigma upper limit has been about 18.91mag The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21041 SUBJECT: Swift trigger 750096 - OT candidate DATE: 17/04/27 03:39:16 GMT FROM: Nial Tanvir at U.Leicester N. R. Tanvir (U. Leicester) reports: I note that the MASTER optical transient reported by Lipunov et al. (GCN 21040) coincides with an AGN for which SDSS gives a magnitude of r=16.1 (consistent with the MASTER source) and a redshift of z=0.101. This suggests there is no compelling reason for it to be associated with Swift trigger 750096.