The long GRB 100621A (Swift-BAT trigger=425151; Ukwatta et al., GCN 10870; Ukwatta et al., GCN 10875) triggered Konus-Wind at T0=11013.352s UT (03:03:33.352) The burst light curve shows multiple overlapping peaks with a total duration of ~80 s. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB100621_T11013/ As observed by Konus-Wind the burst had a fluence...Full Text

Nagayama, M. Kurita (Nagoya Univ.) and N. Oi (The Graduate University for Advanced Studies/NAOJ) on behalf of the IRSF Collabration report: We searched for a NIR afterglow of GRB 100621A (Ukwatta et al., GCN 10870) starting from 04:02 to 04:51 UT on 2010 June 21 with the SIRIUS on the IRSF 1.4m telescope at SAAO in South Africa. In images of a 300 sec exposure with J, H and Ks filter, we...Full Text

We searched for an optical afterglow of GRB 100621A (GCN 10870, T. N. Ukwatta et al.) starting from 09:02 UT on 2010 June 21st (6 hours after the burst) with the MOA-II 1.8m telescope at Mt.John observatory in New Zealand. In a single image of a 300sec exposure with a wide-band Red filter (center wavelength ~ 750nm and FWHM ~ 250nm), we did not find any object within the error circle of the Swift...Full Text

The Swift/UVOT began settled observations of the field of GRB 100621A 85s after the BAT trigger (Ukwatta et al., GCN 10870). We detect a source at the enhanced Swift XRT position (Evans et al. GCN 10873) and at the location of the GROND source (Updike et al. GCN 10874). This source is also observed in the DSS and observed to be constant during the first 7000s and is thus likely to be the host...Full Text

We have analysed 3.6 ks of XRT data for GRB 100621A (Ukwatta et al. GCN 10870), from 79 s to 7.0 ks after the BAT trigger. The data comprise 322 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN. Circ 10872). The light curve can be modelled with a series of power-law decays. The initial decay index...Full Text

We observed the optical afterglow of GRB 100621A (Ukwatta et al., GCN 10870; Updike et al., GCN 10874) with the ESO VLT equipped with the X-shooter spectrograph. The afterglow was detected in the I-band acquisition image. Four spectra lasting 10 minutes each were obtained, covering the spectral range 3000-25000 AA, starting on 2010 June 21, at 10:09 UT (7.1 hr after the GRB); the observations were...Full Text

...Full Text

We observed the field of GRB 100621A (Swift trigger 425151; Ukwatta et al., GCN 10870) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPI/ESO telescope at La Silla Observatory (Chile). Observations started at 03:07 UT on June 21st, 4 minutes after the GRB trigger, and continued for 3 hours. They were performed at an average seeing of 1...Full Text

Using 3262 s of XRT Photon Counting mode data and 4 UVOT images for GRB 100621A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 315.30466, -51.10624 which is equivalent to: RA (J2000): 21h 01m 13.12s Dec (J2000): -51d 06' 22.5" with an uncertainty of 1.7 arcsec (radius, 90% confidence). This...Full Text

Using 0 s of promptly downlinked XRT event data for GRB 100621A, we find an enhanced XRT position of the afterglow: RA, Dec: 315.3052, -51.1060 which is equivalent to: RA (J2000) = 21 01 13.24 Dec (J2000) = -51 06 21.7 with an uncertainty of 2.0 arc sec (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/425151. Position enhancement...Full Text

ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 100621A (Swift trigger 425151; Ukwatta T. N., GCN 10870), producing images beginning 5.0 s after the GCN notice time. An automated response took the first image at 03:04:05.0 UT, 32.2 s after the burst, and during the gamma-ray emission, under fair conditions. We took 10 5-sec, 10 20-sec and 10 60-sec exposures....Full Text

At 03:03:32 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 100621A (trigger=425151). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 315.308, -51.086 which is RA(J2000) = 21h 01m 14s Dec(J2000) = -51d 05' 10" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed...Full Text