//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17809 SUBJECT: GRB 150512A: iPTF Optical Observations DATE: 15/05/13 18:50:52 GMT FROM: Leo Singer at GSFC/iPTF L. P. Singer (NASA/GSFC), V. Bhalerao (IUCAA), M. M. Kasliwal (Carnegie Observatories/Princeton), and S. B. Cenko (NASA/GSFC) report on behalf of the intermediate Palomar Transient Factory (iPTF) collaboration: Fermi detected GRB 150512A (Fermi trigger 453118948 / bn150512432) at 2015-05-12 10:22:25.87. At 2015-05-13 03:58:15, 17.6 hours after the burst, we began searching for optical counterparts using the Palomar 48-inch Oschin telescope (P48). We imaged 20 fields covering an area of 144 deg^2 covering the 1-sigma statistical+systematic region of the final Fermi GBM localization. We estimate a 76% prior probability that these fields contain the true location of the source. Sifting through candidate variable sources using image subtraction and standard iPTF vetting procedures, we detected the following optical transient candidates: iPTF15asm, at the coordinates: RA(J2000) = 13h 40m 45.03s (205.187617 deg) Dec(J2000) = +63d 19' 53.3" (+63.331461 deg) This position is 6" from the galaxy SDSS J134044.09+631954.4 (z = 0.104). We report the following P48 photometry: -95 days: R > 20.27 +18.01 hours: R = 19.49 +/- 0.06 +18.93 hours: R = 19.42 +/- 0.06 iPTF15asn, at the coordinates: RA(J2000) = 13h 57m 40.01s (209.416716 deg) Dec(J2000) = +65d 08' 01.6" (+65.133789 deg) We report the following P48 photometry: -95 days: R > 20.42 +18.01 hours: R = 19.82 +/- 0.07 +18.93 hours: R = 19.98 +/- 0.07 No source was visible in archival P48 and SDSS images at either position. Times are relative to the GBM trigger. Magnitudes are in the Mould R filter and in the AB system, calibrated with respect to point sources in SDSS as described in Ofek et al. (2012, http://dx.doi.org/10.1086/664065). We encourage further observations of both candidates to determine if either is fading and potentially related to the GRB. The diagram http://www.its.caltech.edu/~lsinger/iptf/Fermi453118948.pdf shows the locations of our candidates and the P48 fields in relation to the Fermi GBM 1- and 2-sigma statistical+systematic contours. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17811 SUBJECT: GRB 150512A: Fermi GBM detection DATE: 15/05/13 21:53:22 GMT FROM: Binbin Zhang at UAH Bin-Bin Zhang (UAH) and A. von Kienlin (MPE) report on behalf of the Fermi GBM Team: "At 10:22:25.87 UT on 12 May 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150512A (trigger 453118948 / 150512432), which was also detected by the iPTF (Singer et al. 2015,GCN 17809). The GBM on-ground location is consistent with the positions of the potential transient sources reported by iPTF (Singer et al. 2015, GCN 17809). The angle of the burst direction to the Fermi LAT boresight was 95 degrees. The GBM light curve consists of several peaks with a total duration (T90) of about 123 s (50-300 keV). The time-averaged spectrum from T0-20 s to T0+104 s is best fit by a BAND function with Epeak = 121.5 +/- 18.7 keV, alpha = -0.9 +/- 0.1 and Beta = -2.0 +/- 0.1. The event fluence (10-1000 keV) in this time interval is (2.17 +/- 0.06)E-05 erg/cm^2. The 1.0-sec peak photon flux measured starting from T0+101 s in the 10-1000 keV band is 5.5 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17815 SUBJECT: GRB 150512A: CrAO optical observations DATE: 15/05/14 19:30:18 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), V. Rumyantsev (CrAO), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the two OT candidates (Singer et al., GCN 17809) of the Fermi GRB 150512A (Zhang et al., GCN 17811) with ZTSh telescope of CrAO observatory starting on May. 13 (UT) 21:04:53. Both candidats are clearly visible in our images. Photometry of the candidates is following iPTF15asn: Date UT start t-T0 Filter Exp. Source Err. (mid, days) (s) 2015-05-13 21:04:53 1.45795 R 16*120 19.20 0.03 iPTF15asm: Date UT start t-T0 Filter Exp. Source Err. (mid, days) (s) 2015-05-13 21:46:49 1.48417 R 12*120 19.40 0.02 Photometry of iPTF15asm might be biased by nearby galaxy SDSS J134044.09+631954.4. However both sources do not fade in comparison with early observations (Singer et al., GCN 17809) and most probably cannot be considered as afterglow. Photometry is in Vega, and based on following SDSS stars SDSS9_id R_Lupton J135741.63+650759.8 16.82 J135738.44+650852.4 18.03 J135752.58+650922.2 18.14