//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10489 SUBJECT: GRB 100316B: Swift detection of a burst with optical counterpart DATE: 10/03/16 08:15:37 GMT FROM: Wayne Baumgartner at GSFC W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), S. Campana (INAF-OAB), P. A. Evans (U Leicester), J. M. Gelbord (PSU), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), O. M. Littlejohns (U Leicester), V. Mangano (INAF-IASFPA), C. B. Markwardt (CRESST/GSFC/UMD), P. T. O'Brien (U Leicester), C. Pagani (U Leicester), K. L. Page (U Leicester), P. Romano (INAF-IASFPA), A. Rowlinson (U Leicester), M. H. Siegel (PSU), R. L. C. Starling (U Leicester), G. Tagliaferri (INAF-OAB) and L. Vetere (PSU) report on behalf of the Swift Team: At 08:01:36 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 100316B trigger=416103). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 163.498, -45.480 which is RA(J2000) = 10h 54m 00s Dec(J2000) = -45d 28' 47" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 5 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 08:02:41.1 UT, 64.1 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 163.48846, -45.47220 which is equivalent to: RA(J2000) = 10h 53m 57.23s Dec(J2000) = -45d 28' 19.9" with an uncertainty of 4.1 arcseconds (radius, 90% containment). This location is 36 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 9.92e+20 cm-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 150 seconds with the White filter starting 66 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 10:53:57.15 = 163.48812 DEC(J2000) = -45:28:21.6 = -45.47267 with a 90%-confidence error radius of about 0.62 arc sec. This position is 2.1 arc sec. from the center of the XRT error circle. The estimated magnitude is 18.36 with a 1-sigma error of about 0.15. No correction has been made for the expected extinction corresponding to E(B-V) of 0.14. Burst Advocate for this burst is W. H. Baumgartner (wayne AT milkyway.gsfc.nasa.gov). 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: 10493 SUBJECT: GRB 100316B: GROND Detection of the Optical/NIR Afterglow Candidate DATE: 10/03/16 10:11:25 GMT FROM: Robert Filgas at MPI P. Afonso, R. Filgas and J.Greiner (all MPE Garching) report on behalf of the GROND team: We observed the field of GRB 100316B (Swift trigger #416103; Baumgartner et al., GCN #10489) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m ESO/MPI telescope at La Silla Observatory (Chile). Observations started at 08:17 UT on 16 March 2010, 16 minutes after the GRB trigger, and are continuing. We detect a single point source within the UVOT error circle reported by Baumgartner et al. Based on the first 4 min of total exposures in g'r', we estimate preliminary magnitudes (all in AB system) of g' = 19.2 +- 0.1 mag, r' = 18.9 +- 0.1 mag, indicating reshift < 3.5. Given magnitudes are calibrated against GROND zeropoints and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.14 mag in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10494 SUBJECT: GRB 100316B: Skynet/PROMPT Observations of Fading DATE: 10/03/16 10:13:19 GMT FROM: Josh Haislip at U.North Carolina J. Haislip, K. Ivarsen, D. Reichart, A. LaCluyze, R. Egger, A. Foster, J. Moore, A. Oza, M. Schubel, J. Styblova, A. Trotter, J. A. Crain, and M. Nysewander report: Skynet observed the Swift/BAT localization of GRB 100316B (Baumgartner et al., GCN 10489) with four of the 16" PROMPT telescopes at CTIO beginning 32 seconds after the trigger (19 seconds after notification) in BVRI. We detect the afterglow (Baumgartner et al., GCN 10489) in all filters. At 34 seconds after the trigger, the afterglow's magnitude was I = 15.61 +0.16 -0.14 (statistical) +/- 0.20 (systematic; calibrated to 56 USNO B1 stars). Between 34 seconds and 2.1 minutes after the trigger, the afterglow faded with a power-law index of about -1.0. Between 2.1 and 35 minutes after the trigger, the afterglow faded more slowly, with a power-law index of about -0.3. Between 35 and 41 minutes after the trigger, the afterglow suddenly rebrightened, with a power-law index of about +5.4. Between 41 and 49 minutes after the trigger, the afterglow faded with a power-law index of about -0.6. Between 49 and 95 minutes after the trigger, the afterglow faded more rapidly, with a power-law index of about -1.7. At 95 minutes after the trigger, the afterglow's magnitude was R = 19.51 +0.33 -0.26 (statistical) +/- 0.28 (systematic; calibrated to 40 USNO B1 stars). Skynet's most recent BVRI light curve, calibrated to USNO B1 and NOMAD stars, can be found here: http://skynet.unc.edu/grb/grb100316b.png //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10495 SUBJECT: GRB 100316B: VLT/X-shooter redshift DATE: 10/03/16 11:04:59 GMT FROM: Paolo D'Avanzo at INAF-OAB S.D. Vergani (APC/Univ. Paris 7), P. D'Avanzo (INAF-OAB), D. Malesani, J.P.U. Fynbo, J. Hjorth (DARK/NBI), A.J. Levan (Univ. Warwick), H. Flores (Paris Obs.), N.R. Tanvir (Univ. Leicester), P. Goldoni (APC/Univ. Paris 7 and SAp/CEA), L.A. Antonelli (INAF-OAR) report on behalf of a larger collaboration: We observed the optical afterglow of GRB 100316B (Baumgartner et al., GCN 10489; Afonso et al. GCN 10493; Haislip et al., GCN 10494) with the VLT equipped with the X-shooter spectrograph. Observations started on 2010 Mar 16 at 08:43 UT (~ 40 minutes after the GRB), for a total exposure time of 4x600 s. From the acquisition image, we estimate for the optical afterglow a magnitude of R = 18.2 +- 0.1 (calibrated against USNO-B1.0). In a preliminary analysis of the specta, we clearly detect the continuum in the UVB, VIS, and NIR arms, corresponding to the wavelength range 3200-24000 AA. We detect several absorption features, among these FeII(1608), AlII(1670), AlIII(1854), FeII(2344), FeII(2374), FeII(2382), MgII(2796, 2803) and MgI(2852) at a common redshift of z=1.180. The lack of Lyman forest lines down to ~3200 AA sets an upper limit to the redshift z<1.6. We also find evidence for FeII lines and MgII doublet from a strong intervening systems at z=1.063. We caution that the above analysis (particularly the wavelength solution) is preliminary. Reduction with updated calibrations is underway. We would like to thank the ESO staff for their kind assistance, in particular Linda Schmidtobreick, Christophe Martayan, Patricia Guajardo and Manuel Olivares. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10500 SUBJECT: GRB 100316B: Swift-BAT refined analysis DATE: 10/03/16 15:54:41 GMT FROM: Scott Barthelmy at NASA/GSFC C. B. Markwardt (GSFC/UMD), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-61 to T+242 sec from recent telemetry downlinks, we report further analysis of BAT GRB 100316B (trigger #416103) (Baumgartner, et al., GCN Circ. 10489). The BAT ground-calculated position is RA, Dec = 163.499, -45.464 deg, which is RA(J2000) = 10h 53m 59.8s Dec(J2000) = -45d 27' 49.3" with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 83%. The mask-weighted light curve shows a FRED peak starting at T-0.3 sec, peaking at ~T+0.2 sec, and ending at ~T+20 sec. T90 (15-350 keV) is 3.8 +- 0.5 sec (estimated error including systematics). The time-averaged spectrum from T-0.4 to T+4.0 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.23 +- 0.18. The fluence in the 15-150 keV band is 2.0 +- 0.2 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-0.11 sec in the 15-150 keV band is 1.3 +- 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/416103/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10502 SUBJECT: GRB 100316B: Enhanced Swift-XRT position DATE: 10/03/16 16:51:19 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 1148 s of XRT Photon Counting mode data and 2 UVOT images for GRB 100316B, 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 = 163.48865, -45.47244 which is equivalent to: RA (J2000): 10h 53m 57.28s Dec (J2000): -45d 28' 20.8" with an uncertainty of 1.8 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) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10508 SUBJECT: GRB 100316B: Swift/UVOT observations DATE: 10/03/16 19:29:42 GMT FROM: Patricia Schady at MSSL/Swift S. R. Oates (MSSL-UCL) and W. H. Baumgartner (GSFC/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT began observerving the field of GRB 100316B 67s after the BAT trigger (Baumgartner et al., GCN Circ. 10489). We detect the optical afterglow in the white, v, b, u and marginally in the uvw1 filter. The refined UVOT position is RA (J2000)= 163.48809, DEC (J2000)=-45.47265, which is equivalent to: RA (J2000) = 10:53:57.141 Dec (J2000) = -45:28:21.54 with an estimated uncertainty of 0.52 arcsec (radius, 90% confidence). This position is consistent with the XRT refined position (Beardmore et al., GCN Circ 10502). The marginal detection in the uvw1 filter is consistent with the VLT redshift upper limit (D'Avanzo et al., GCN Circ. 10495). Preliminary magnitudes and the 3 sigma upper limits are reported below for individual optical images and summed UV images. Filter T_start(s) T_stop(s) Exposure Mag Err ########################################################### white 67 216 147 18.36 +/- 0.05 white 857 1007 147 19.15 +/- 0.09 u 279 528 246 18.44 +/- 0.10 v 1212 1232 19 18.28 +/- 0.46 b 535 555 19 18.97 +/- 0.36 uvw1 659 1108 58 18.91 +/- 0.36 uvm2 634 1246 66 > 18.59 uvw2 585 1207 78 > 19.13 ########################################################### The above magnitudes are not corrected for the Galactic extinction corresponding to a non-negligible reddening of E_{B-V} = 0.14 mag (Schlegel et al., 1998, ApJS, 500, 525). The photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383,627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10518 SUBJECT: GRB 100316B: Swift-XRT refined analysis DATE: 10/03/17 09:30:12 GMT FROM: Owen Littlejohns at U of Leicester O. M. Littlejohns, P. A. Evans, K. L. Page (U. Leicester) and W. H. Baumgartner (GSFC/UMBC) report on behalf of the Swift-XRT team: We have analysed 2.9 ks of XRT data for GRB 100316B (Baumgartner et al. GCN Circ. 10489), from 75 s to 40.1 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN. Circ 10502). The light curve can be modelled with a broken power-law decay with an initial decay index of alpha=0.1 (+/-0.2), followed by a break at T~1100 s to a final decay of alpha=1.2 (+0.5, -0.1). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.35 (+0.24, -0.21). The best-fitting absorption column is 4.1 (+2.7, -1.3) x 10^21 cm^-2, at a redshift of 1.18 (Vergani et al. GCN Circ 10495), in addition to the Galactic value of 9.9 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.4 x 10^-11 (5.8 x 10^-11) erg cm^-2 count^-1. If the light curve continues to decay with a power-law decay index of 1.2, the count rate at T+48 hours will be 6.6 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.2 x 10^-14 (3.8 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00416103. This circular is an official product of the Swift-XRT team.