//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8381 SUBJECT: GRB 081016B: Swift detection of a burst DATE: 08/10/16 20:04:12 GMT FROM: Scott Barthelmy at NASA/GSFC K. L. Page (U Leicester), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), P. A. Evans (U Leicester), O. Godet (U Leicester), C. Guidorzi (INAF-OAB), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), W.B Landsman (GSFC), C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), J. P. Osborne (U Leicester), D. M. Palmer (LANL), M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester), M. C. Stroh (PSU), T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the Swift Team: At 19:47:14 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 081016B (trigger=331856). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 14.615, -43.543 which is RA(J2000) = 00h 58m 28s Dec(J2000) = -43d 32' 34" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak with a duration of about 5 sec. The peak count rate was ~1600 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 19:48:45.1 UT, 90.6 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued, fading X-ray source located at RA, Dec 14.5670, -43.5296 which is equivalent to: RA(J2000) = 00h 58m 16.08s Dec(J2000) = -43d 31' 46.6" with an uncertainty of 3.3 arcseconds (radius, 90% containment). This location is 134 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 1.96e+20 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 150 seconds with the White (160-650 nm) filter starting 93 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.01. Burst Advocate for this burst is K. L. Page (kpa AT star.le.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8382 SUBJECT: GRB 081016B: ROTSE-III Optical Limits DATE: 08/10/16 20:14:33 GMT FROM: Brad Schaefer at LSU B. E. Schaefer (Louisiana State), E.S. Rykoff (UCSB), and H. Swan (U. Mich.) report on behalf of the ROTSE collaboration: ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 081016B (Swift trigger 331856), producing images beginning 6.4 s after the GCN notice time. An automated response took the first image at 19:47:59.4 UT, 44.9 s after the burst, under excellent conditions. We took 10 5-sec, 10 20-sec and 20 60-sec exposures. These unfiltered images are calibrated relative to USNO A2.0 (R). Imaging is on going. Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma Swift/BAT error circle or the XRT error circle, for both single images and coadding into sets of 10; the field is not crowded. Individual images have limiting magnitudes ranging from 15.8-17.1; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 19:47:59.4 19:48:04.4 5 15.8 44.9 N 19:47:59.4 19:49:15.5 76 17.5 44.9 Y [GCN OPS NOTE(17oct08): Per author's request, the burst name was changed from "A" to "B".] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8383 SUBJECT: GRB 081016B: Enhanced Swift-XRT position DATE: 08/10/17 00:40:37 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 2096 s of XRT Photon Counting mode data and 1 UVOT images for GRB 081016B, 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 = 14.56434, -43.53015 which is equivalent to: RA (J2000): 00h 58m 15.44s Dec (J2000): -43d 31' 48.5" with an uncertainty of 2.1 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401 http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an extension of this method. This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8384 SUBJECT: GRB 081016B: Swift-XRT Team refined Analysis DATE: 08/10/17 05:10:42 GMT FROM: Kim Page at U.of Leicester K.L. Page (U. Leicester) reports on behalf of the Swift-XRT team: We have analysed the first six orbits of the XRT data obtained for GRB 081016B (Page et al., GCN Circ. 8381). After an initial 18 seconds in Windowed Timing mode, the remaining 3.5 ks were collected in Photon Counting (PC) mode. The UVOT-enhanced position was given by Osborne et al. in GCN Circ. 8383. The first orbit of data shows a decay of alpha = 1.1 +/- 0.3. However, after the end of this orbit (~265 s after the trigger), the source is no longer detected, indicating a break to a significantly steeper decay occurred. The spectrum of the first orbit of PC data can be modelled with a power-law (Gamma = 1.20 +/- 0.18) absorbed at the Galactic value of NH = 1.96x10^20 cm^-2. The upper limit on the total absorbing column is 2.2x10^21 cm^-2. The observed (unabsorbed) flux over this time is 2.43x10^-10 (2.48x10^-10) erg cm^-2 s^-1, corresponding to a counts to observed flux conversion of 6.8x10^-11 erg cm^-2 count^-1. Because of the lack of detection after the first orbit, we cannot predict the future count rate. This is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8386 SUBJECT: GRB 081016B: Swift/UVOT Upper Limits DATE: 08/10/17 15:47:39 GMT FROM: Wayne Landsman at GSFC/SSAI W.Landsman (GSFC) and K. L. Page (U Leicester), on behalf of the Swift/UVOT team. The Swift Ultra-Violet/Optical Telescope (UVOT) began settled observations of GRB 081016B (trigger 331856) 93 seconds after the BAT trigger (Page et al.,GCN Circ. 8381). No afterglow is detected at the enhanced XRT position (Osborne et al., GCN Circ. 8383) in the initial white finding chart or subsequent images. The limiting magnitudes (3-sigma in 3" radius apertures) in each of the UVOT filters are as follows: Filter T_start(s) T_stop(s) Exp(s) Mag UL (3sig) white 93 243 150 >21.5 b 4710 4823 113 >20.6 v 5373 5572 197 >20.0 u 5988 11724 960 >21.5 uvw1 5783 5982 197 >20.3 uvm2 5577 5777 197 >20.0 uvw2 5168 5368 197 >20.3 The values quoted above are in the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627). They are not corrected for the expected Galactic extinction corresponding to a reddening of E(B-V)=0.01 mag in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8387 SUBJECT: GRB 081016B, Swift-BAT refined analysis DATE: 08/10/17 21:37:05 GMT FROM: Hans Krimm at NASA-GSFC M. Stamatikos (GSFC/ORAU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), K. L. Page (U Leicester),D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 081016B (trigger #331856) (Page, et al., GCN Circ. 8381). The BAT ground-calculated position is RA, Dec = 14.582, -43.536 deg which is RA(J2000) = 00h 58m 19.8s Dec(J2000) = -43d 32' 07.9" with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 98%. The BAT mask-weighted light curve showed a single peak of duration ~2.5 seconds. T90 (15-350 keV) is 2.6 +- 0.8 sec (estimated error including systematics). The time-averaged spectrum from T-0.0 to T+3.0 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.92 +- 0.32. The fluence in the 15-150 keV band is 9.9 +- 1.8 x 10-08 erg/cm2. The 1-sec peak photon flux measured from T+0.50 sec in the 15-150 keV band is 0.5 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/331856/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8534 SUBJECT: GRB 081016b, SMARTS optical/IR observations DATE: 08/11/20 22:50:32 GMT FROM: Bethany Cobb at UC Berkeley B. E. Cobb (UC Berkeley) reports: Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 081016b (Page et al. GCN 8381) with a mid-exposure time of 4.3 hours post-burst (2008-10-17 00:06 UT). Total summed exposure times amounted to 36 minutes in I and 30 minutes in J. No source is detected at the position of the X-ray afterglow (Osborne et al. GCN 8383) to approximate limiting magnitudes of I > 22.1 and J > 19.8. Magnitudes are calibrated using Landolt standard stars in I, and 2MASS stars in J.