//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17551 SUBJECT: GRB 150305A: Swift XRT confirms weak INTEGRAL event as a new GRB DATE: 15/03/08 18:12:17 GMT FROM: Rhaana Starling at U of Leicester R. Starling (U. Leicester) reports: On 2015-03-05T09:49:19 UT INTEGRAL recorded a 7.6 sigma event at RA, Dec 269.78943, -41.62041 degrees (err 3.39 arcmin) and issued WEAK Alert 6905. We triggered a Swift ToO to observe this position. Swift observations began at 1.8E4 s after the INTEGRAL trigger with exposure time 3ks (obsID33663). Two sources were present in the error circle. One of these is consistent with the ROSAT source 1RXS J175914.5-423529, which is likely associated with dwarf nova V728 CrA. The second is a new source, with enhanced XRT position of RA, Dec (J2000) = 17h 59m 02.60s, -42° 39′ 49.5′′ (269.76082, -42.66374 deg) with an uncertainty of 3.3′′ (radius, 90% confidence). In this first observation the new source had a count rate 0.035 ct/s. Further Swift observations beginning 1.1E5s post-burst with exposure time 3.7ks showed that this source had a count rate of approx. 0.007 ct/s, having faded with a decay rate of alpha ~ -0.7. The spectrum of the new source can be described with an absorbed power law. The UVOT data were taken in UVM2 and UVW1 filters. A preliminary analysis does not reveal any UV counterpart to the new XRT source. We conclude that the INTEGRAL WEAK event was a real GRB and that the fading source discovered by Swift XRT is the afterglow. We thank the Swift team for carrying out these ToOs, and acknowledge use of the UK Swift Science Data Centre in our analysis. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17552 SUBJECT: GRB 150305A: a long GRB detected by INTEGRAL DATE: 15/03/09 12:41:36 GMT FROM: Sandro Mereghetti at IASF/CNR S.Mereghetti (IASF-Milano), D.Gotz (CEA, Saclay), C.Ferrigno, E.Bozzo (ISDC, Versoix), and J.Borkowski (CAMK, Torun) on behalf of the IBAS Localization Team report: a gamma ray burst lasting at least 100 s has been detected by IBAS in the IBIS/ISGRI data at 09:49:19 UT of March 5, 2015. The refined coordinates (J2000) are: R.A.= 269.7685 deg DEC.= -42.6481 deg with an uncertainty of 2.5 arcmin (90% c.l.). The burst had a peak flux of about 0.2 counts/cm2/s (20-200 keV, 1-s integration time) and a fluence in the same energy range of about 7e-7 erg/cmq (over 100 s). Due to the significance of the detection below the high confidence threshold, only an Alert Packet of WEAK type was distributed by IBAS in real time (Packet n. 6905). The X-ray afterglow has been detected with Swift/XRT (Starling 2015, GCN 17551). A plot of the light curve can be found at http://ibas.iasf-milano.inaf.it/IBAS_Results.html