This file contains Circulars for both GRBs: 051016A and 051016B //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4096 SUBJECT: GRB051016: Swift detection of a burst DATE: 05/10/16 06:07:36 GMT FROM: Scott Barthelmy at NASA/GSFC P. Boyd (GSFC/UMBC), S. Barthelmy (GSFC), A. Beardmore (U. Leicester), D. Burrows (PSU), N. Gehrels (GSFC), C. Gronwall (PSU), S.T. Holland (GSFC), J. Kennea (PSU), C. Markwardt (GSFC/UMD), D. Palmer (LANL), T. Sakamoto (GSFC) on behalf of the Swift team: At 05:23:31 UT, Swift-BAT triggered and located GRB051016 (trigger=159913). The BAT on-board calculated location is RA,Dec 122.811,-18.311d {08h 11m 15s,-18d 18' 39"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows a single peak with a total duration of ~15 sec. The peak count rate was ~1200 counts/sec (15-350 keV), at ~2 seconds after the trigger. The spacecraft slewed promptly and the XRT began observing the GRB at 05:25:23 UT, 112 sec after the BAT trigger. An uncatalogued source was found by the on-board centroiding algorithm at RA(J2000)= 08h 11m 16.3s DEC(J2000)=-18d 17' 49.2" with an uncertainty of 8 arcseconds radius (90% containment). This position lies 56 arcseconds from the centre of the BAT error circle. The initial flux is approximately 3.8E-10 ergs/cm2/s (0.3-10 keV). The count rate decreases during the first 100 seconds. UVOT began observing the field at 05:25:26 UT. The small image includes the BAT and the XRT error circles. This image contains no new sources down to a V limiting magnitude of 19.1 (3-sigma). No new source was seen in the list of sources from the entire UVOT field of view. E(B-V) in this direction is 0.088. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4097 SUBJECT: GRB 051016: PROMPT Observations DATE: 05/10/16 07:30:50 GMT FROM: Melissa Nysewander at UNC,Chapel Hill M. Nysewander, D. Reichart, A. Crain, A. Foster, J. Haislip report on behalf of the UNC team of the FUN GRB Collaboration: Under the control of Skynet, PROMPT observed the localization of GRB 051016 (Boyd et al., GCN 4096) beginning 6.6 min after the burst, when the field was still at high airmass, in repeating blocks of BVRcIc (two filters simultaneously). We do not detect any new sources within or around the XRT localization. In a 12 x 80 sec integration of mean epoch 25.6 min after the burst, we measure a 3-sigma limiting magnitude of Rc = 19.1, based on 3 USNO-B1.0 stars. PROMPT is still being built and commissioned. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4098 SUBJECT: GRB 051016: LCO optical and near-IR imaging DATE: 05/10/16 09:43:36 GMT FROM: Edo Berger at Carnegie Obs E. Berger (Carnegie Observatories), M. Roth, and S. Gonzalez (Las Campanas Observatory) report: "We imaged the error circle of GRB 051016 (GCN #4096) with the Swope 40-inch telescope in I-band and with the Magellan telescope in J-band. A total of 10 min were obtained in I-band on Oct 16.345 UT and 20 min were obtained in J-band on Oct 16.325 UT (2.9 and 2.4 hours after the burst, respectively). We do not detect any sources within the XRT error circle which are not visible in the DSS. The 3-sigma upper limits are I>20 mag and J>21.7 mag." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4099 SUBJECT: GRB051016: Planned XMM-Newton observation DATE: 05/10/16 13:07:19 GMT FROM: Norbert Schartel at XMM-Newton/ESA XMM-Newton will observe GRB051016 (GCN 4096) at location (RA=08h 11m 16.3s, DEC=-18d 17' 49.2", J2000), as triggered by D. Fox via XMM-Newton ToO alert, starting at 12:49 UT, on October 16, 2005, for an exposure of 30ksec seconds. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4100 SUBJECT: GRB051016: Swift XRT refined analysis. DATE: 05/10/16 15:13:00 GMT FROM: Andy Beardmore at U Leicester A. Beardmore (U. Leicester), D. Burrows, J. Kennea (PSU), N. Gehrels (GSFC) report on behalf of the Swift XRT team: We have analysed the first two orbits of data from the Swift XRT observation of GRB051016 (Boyd et al., GCN4096). The refined ground processed coordinates are : RA(J2000) = 08h 11m 16.3s Dec(J2000) = -18d 17m 56.3s with an estimated uncertainty of 8 arcsecs radius (90% containment). This is 7.1 arcsecs awsy from the XRT position reported in Boyd et al. The XRT light curve from this interval shows a steep initial decline, followed by a break to a shallower decay slope. A broken power-law fit to the light curve gives parameters : alpha_1 = 4.8 +0.5-0.4 t_break = 247 +/- 15s alpha_2 = 0.7 +/- 0.1. The Windowed Timing (WT) and Photon Counting mode spectra from the first two orbits can be fit with an absorbed power-law with a photon index of 3.14+/-0.45 and a column density of 4.5+/-1.5 E21 cm-2, which is slightly in excess of the Galactic column density of 1.19E+21 cm-2 in this direction. The observed 0.2-10 keV flux for the WT data (exposure time 22.2s, centered at T+130s) was 1.31E-10 ergs cm**-2 s**-1, corresponding to an unabsorbed flux of 9.98E-10 ergs cm**-2 s**-1. Assuming the X-ray emission from the GRB continues to decline at the same rate, the predicted XRT count rate at T+24hrs is 0.0036 counts/s, which corresponds to an observed 0.2-10 keV flux of 1.1e-13 ergs cm**-2 s**-1. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4101 SUBJECT: GRB051016 XMM-Newton observation DATE: 05/10/16 17:11:36 GMT FROM: Norbert Schartel at XMM-Newton/ESA Nora Loiseau and Ricardo Perez-Martinez report: Quick-Look-Analysis of the XMM-Newton observation of the GRB051016 field based on an exposure in the EPIC pn camera that started at 13:46 UT, shows the presence of a source at the SWIFT/XRT position (Boyd et al., GCN4096) within XRT 8 arcsec radius uncertainty. The estimated EPIC/pn net count rate for the first 5.9 ksec is 0.029 counts/sec. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4102 SUBJECT: GRB 051016: Swift-BAT refined analysis DATE: 05/10/16 17:34:48 GMT FROM: Scott Barthelmy at NASA/GSFC J. Tueller (GSFC), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cannizzo (GSFC-UMBC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), M. Tashiro (Saitama U.), on behalf of the Swift-BAT team: Using the data set from T-300 to T+300 sec from recent telemetry downlinks, we report further analysis of Swift-BAT GRB 051016 (trigger 159913) (Boyd, et al., GCN 4096). The refined BAT ground position is (RA,Dec) = 122.820, -18.309 deg {8h 11m 16.9s, -18d 18' 33.2"} (J2000) +- 2.0 arcmin, (radius, sys+stat, 90% containment). This position is 38 arcsec from the refined XRT position (Beardmore t al., GCN 4100). The partial coding was 18 %. The light curve shows a FRED-like peak. T90 (15-350 keV) is (22 +- 1) sec (estimated error including systematics). The power law index of the time-averaged spectrum is 1.88 +- 0.27. The fluence in the 15-150 keV band is (8.8 +- 1.4) x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T0+0.3 sec in the 15-150 keV band is (1.6 +- 0.4) ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4103 SUBJECT: GRB 051016B: Swift detection of a soft burst DATE: 05/10/16 19:18:13 GMT FROM: Scott Barthelmy at NASA/GSFC A. Parsons (GSFC), S. Barthelmy (GSFC), A. Beardmore (U. Leicester), P. Boyd (GSFC), D. Burrows (PSU), J. Cummings (GSFC/NRC), N. Gehrels (GSFC), O. Godet (U. Leicester), C. Gronwall (PSU), J. Kennea (PSU), H. Krimm (GSFC/USRA), F. Marshall (GSFC), D. Palmer (LANL), T. Sakamoto (GSFC) on behalf of the Swift team: At 18:28:09 UT, Swift-BAT triggered and located GRB 051016B (trigger=159994). The BAT on-board calculated location is RA,Dec 132.067d,+13.658d {08h 48m 16s,+13d 39' 27"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows a double peak structure with a total duration of at least 15 sec -- the slew started at T+15 sec, so determination of the full duration will have to wait until after the full data set is downlinked. The peak count rate was ~2200 counts/sec (15-150 keV), at ~1 and 3 seconds after the trigger. Initial inspection of the 4-channel lightcurves shows this burst to be soft. The spacecraft slewed promptly and the XRT began observing the GRB at 18:29:24 UT, 75 sec after the BAT trigger. An uncatalogued source was found by the on-board centroiding algorithm at RA(J2000)=08h 48m 27.6s Dec(J2000)=+13d 39' 25.5" with an uncertainty of 8 arcsec radius (90% containment). This position lies 168 arcsec from the center of the BAT error circle. The initial flux is approximately 4.6e-10 ergs/cm2/s. The count rate decreases during the first 100 seconds. UVOT began observing the field at 18:29:26 UT, 77 sec after the BAT trigger. The small image contains the entire XRT error circle. This image contains no new sources down to a limiting magnitude of 18.7 (3-sigma). No new source was seen in the list of sources from the entire UVOT field of view. E(B-V) in the direction of the XRT position is 0.037. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4104 SUBJECT: GRB 051016B: Refined analysis of the Swift-BAT burst DATE: 05/10/16 22:31:42 GMT FROM: Scott Barthelmy at NASA/GSFC L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), F. Marshall (GSFC), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), T. Takahashi (ISAS), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the full data set from the recent telemetry downlink, we report further analysis of Swift-BAT GRB 051016B (trigger #159994) (Parsons, et al., GCN 4103). The ground-analysis position is RA,Dec 132.120,+13.627 {08h 48m 28.8s,+13d 37' 38.4"} (J2000) with an uncertainty of 1.6 arcmin (radius, 90%, stat+sys). The parital coding fraction is 79 %. T90 is 4.0 +- 0.1 sec. The lightcurve consists of two overlapping peaks at T+0.3 and T+3.0 sec. Fitting a simple power law over the full interval from T-0.0 to T+4.6 sec, the photon index is 2.38 +/- 0.23 with a fluence of 1.7 +/- 0.2 X 10^-7 erg/cm^2. The peak flux in a 1-sec wide window starting at T+0.11 sec is 1.32 +/- 0.17 ph/cm^2/sec. All values are in the 15-150 keV band at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4105 SUBJECT: GRB 051016B : Optical follow-up at Lulin DATE: 05/10/17 03:12:42 GMT FROM: Kuiyun Huang at IANCU GRB 051016B : Optical follow-up at Lulin Y.T. Chen, Y.L. Wu, K-Y. Huang, W-H. Ip(NCU), Y. Urata (RIKEN) on behalf of EAFON report: " We have observed entire error region of GRB 051016B (Parsons et al. GCN 4103) with 1-m telescope at Lulin Observatory, Taiwan. Compare with DSS-2 images, we find a source in the Swift/XRT error region. The position is RA=08:48:27.81 DEC=+13:39:20.0. The source do not show significant variability during our observational period (1.5-2 hours after the burst). These 3-sigma limiting magnitudes derived from the USNO-B1.0 catalog are R=21.5. This message may be cited." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4106 SUBJECT: GRB 051016B,optical observation DATE: 05/10/17 13:10:56 GMT FROM: Shouta Maeno at U.of Miyazaki S.Maeno,E.Sonoda,Y.Tokunaga,M.Yamauchi (University of Miyazaki) "We have observed the field covering the error circle of GRB 051016B (GCN4103) with the unfiltered CCD camera on the 30-cm telescopeat University of Miyazaki. The observation was started 19:16:07 UT on Oct.16. After co-adding a set of 25 images (19:16:07 - 19:59:25 UT) of 30 sec exposures, we have compared with the USNO A2.0 catalog. Preliminary analysis shows there is no new source brighter than 17.8 mag." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4107 SUBJECT: GRB 051016B: Swift/UVOT detection DATE: 05/10/17 13:45:59 GMT FROM: Alexander Blustin at MSSL-UCL A. J. Blustin (UCL-MSSL), A. Parsons (GSFC), S. T. Holland (GSFC), P. Meszaros, M. Chester (PSU), N. Gehrels (GSFC) on behalf of the Swift/UVOT team report: The Swift/UVOT began taking a settled exposure of the field of GRB 051016B 78 s after the trigger (Parsons et al. GCN 4103). A faint optical/UV source (not visible in the DSS) is detected in summed images at the position reported by Chen et al. (GCN 4105) at greater than 3 sigma in four of the UVOT filters; the magnitudes and upper limits are as follows: Filter T_range(sec) Exp(sec) Mag/3-sig upper limit V 78-29720 2418 20.5 (upper limit) B 445-28020 2748 22.0 +/- 0.5 U 391-35505 2507 20.9 +/- 0.3 UVW1 337-34740 2796 21.7 +/- 0.4 UVM2 283-33833 2798 21.0 (upper limit) UVW2 554-28928 2748 22.8 +/- 0.6 The detection in UVW2 would imply that the redshift of the source is less than ~1.3. There was a further uncatalogued nearby UV-only source at (J2000 08:48:27.7 +13:39:12.0), outside the XRT error circle, with the following magnitudes: Filter Mag UVW1 21.9 +/- 0.4 UVM2 22.3 +/- 0.4 UVW2 22.0 +/- 0.3 Further data will be required to tell whether either source is variable. _______________________________________________ Uvot_cal mailing list Uvot_cal@phoenix.astro.psu.edu https://phoenix.astro.psu.edu/mailman/listinfo/uvot_cal //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4108 SUBJECT: GRB 051016B: refined analysis of the Swift/XRT data DATE: 05/10/17 16:26:18 GMT FROM: Olivier Godet at U.of Leicester O. Godet (U. Leicester), A. Parsons (GSFC) K. Page, J. Osborne, A. Beardmore (U. Leicester), D. Burrows (PSU), N. Gehrels (GSFC) report on behalf the Swift XRT team: We have analysed the first four orbits of data from the Swift XRT observation of GRB051016B (Parsons et al., GCN 4103). The refined ground processed coordinates are : RA(J2000) = 08h 48m 27.5s Dec(J2000) = +13d 39m 20.8s with an estimated uncertainty of 8 arcsecs radius (90% containment). This is 4.9 arcsecs away from the XRT position reported in Parsons et al. The XRT light curve shows a steep initial decline with a decay slope of 5.3+0.6/-0.7, followed by a break at ~T+ 200s to a shallower decay slope with a flare at ~T+409s superposed. At ~T+6000s, another break can be seen in the X-ray light-curve with a steeper decay slope of 0.9+/-0.2. The X-ray spectra show strong evolution in the early phase. The Windowed Timing (WT) data from the first orbit (from T+82s to T+107s) can be fit with an absorbed power-law with a photon index of 6.2+2.4/-1.5 and a column density excess of 4.8+/-2.0 E21 cm-2 over the Galactic column density of 3.66E+20 cm-2 in this direction. The Photon Counting (PC) spectrum from the first orbit (containing the flare) can be fit with an absorbed power-law with a photon index of 1.8+0.2/-0.4 and no absorption excess over the Galactic absorption. The PC spectrum of the second, third and fourth orbits can be fit by an absorbed power-law with a photon index of 1.5+/-0.1 and no absorption excess over the Galactic absorption. The observed 0.2-10 keV flux for the PC data from the second, third and fourth orbits (exposure time ~7600s, starting at ~T+3950s) was 3.82E-12 ergs cm**-2 s**-1, corresponding to an unabsorbed flux of 4.15E-12 ergs cm**-2 s**-1. Assuming the X-ray emission from the GRB continues to decline at the same rate (alpha~0.94), the predicted XRT count rate at T+24hrs is 0.0077 counts/s, which corresponds to an observed 0.2-10 keV flux of 4.2e-13 ergs cm**-2 s**-1. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4109 SUBJECT: GRB 051016A: Swift/UVOT upper limits DATE: 05/10/17 19:06:25 GMT FROM: Alexander Blustin at MSSL-UCL A. J. Blustin (UCL-MSSL), P. Boyd (GSFC), S. Oates (UCL-MSSL), R. Fink (GSFC), M. Ajello (MPE), N. Gehrels (GSFC) on behalf of the Swift/UVOT team report: The Swift-UVOT began taking settled exposures of the field of GRB 051016A 116 s after the BAT trigger (Boyd et al. GCN 4096). No new source with respect to the DSS is detected within the refined XRT error circle (Beardmore et al. GCN 4100) in summed images down to the following 3-sigma magnitude upper limits: Filter T_range(sec) Exp(sec) 3sigUL V 116-41900 3345 20.3 B 483-40330 3693 21.7 U 428-47088 2542 20.7 W1 374-47026 3798 20.7 M2 320-46119 3798 21.0 W2 591-41238 3699 21.1 Where T_range is time post-trigger. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4110 SUBJECT: GRB 051016b: Gemini Near IR Observations DATE: 05/10/18 08:07:33 GMT FROM: Ryan Foley at UC Berkeley J. S. Bloom (UCB), H.-W. Chen, (Chicago), R. J. Foley (UCB), J. X. Prochaska (UCSC), report on behalf of a larger collaboration: "We observed the position of GRB 051016b (GCN 4103) with the NIRI instrument on the Gemini North Telescope beginning 20051017.59 UTC. In a stack of 45 minutes of exposure we detect several faint sources consistent with the XRT position (GCN 4108): A: 08:48:27.85 13:39:20.4 B: 08:48:27.32 13:39:18.1 C: 08:48:27.64 13:39:13.6 D: 08:48:27.42 13:39:23.9 The astrometry is derived assuming the nominal platescale of NIRI and based on the assumption that a bright galaxy (2MASS 1036.075258) is at position (J2000) 08:48:27.607 +13:39:02.67. Source A is 0.6" E and 0.4" N of an optical source reported by Maeno et al. (GCN 4106) and we thus associate this apparent IR point source (A) with the Lulin/UVOT source. We measure an isophotal mag of Ks[A] = 20.52 +/- 0.12 mag, assuming the 2MASS galaxy has magnitude of Ks = 15.209 mag. We make no claim of variability but source A is the most point-like of the 4 objects in the XRT error circle, so it is still a plausible afterglow candidate." We thank the Gemini observing staff for performing this ToO. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4111 SUBJECT: Afterglow candidate of GRB 051016B observed at Lulin DATE: 05/10/18 09:38:17 GMT FROM: Yuji Urata at RIKEN D. Kinoshita, Y.T. Chen, Y.L. Wu, K-Y. Huang, W-H. Ip(NCU), Y. Urata (RIKEN) on behalf of EAFON report: " We have observed the field of GRB 051016B (Parsons et al. GCN 4103) with Lulin 1m telescope at 17.845 (1.08 days after the burst). The R-band stacked image made from 5 x 300sec exposure do not show the candidate source reported by Chen et al (GCN 4105). These results suggest that the source located at RA=08:48:27.81 DEC=+13:39:20.0 is the afterglow of GRB 051016B. These images are available at http://140.115.34.82/~qq/grb/GRB051016B_LOT.jpg Our light curve around 1.5-2 hour do not show power-law decay as we reported (Chen et al GCN 4105). However, several early afterglows show platue phase such as GRB 041006 (Urata et al. ApJL submitted). This message may be cited." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4112 SUBJECT: GRB 051016b: Optical limit DATE: 05/10/19 02:53:53 GMT FROM: Ken ichi Torii at RIKEN K. Torii (Osaka U.) reports on behalf of the ART collaboration: The error region of the soft GRB 051016b (Parsons et al. GCN 4103) was observed by the 14 inch Automated Response Telescope. VRcIc imaging started at 2005 October 16, 18:29:54 UT (105s after the trigger) and 60s integration was repeated. The optical afterglow candidate (Chen et al. GCN 4105) is not detected in our frames and the following limiting magnitudes for single and stacked frames are derived. ------------------------------------------ StartUT Filter Limit Nframes ------------------------------------------ 18:29:54 Rc 15.7R 1 18:30:58 Ic 15.2I 1 18:29:54 V+Rc+Ic 18.3R 9V+10Rc+10Ic ------------------------------------------ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4185 SUBJECT: GRB051016B: optical observation DATE: 05/11/01 21:09:17 GMT FROM: Alexei Pozanenko at IKI, Moscow D. Sharapov, M. Ibrahimov (MAO), A.Pozanenko (IKI),V.Rumyantsev (CrAO) on behalf of larger GRB follow up collaboration report: We observed the error box of GRB051016B (Parsons et al, GCN 4103) with 1.5m telescope of Maidanak Astronomical Observatory. Set of R images were taken between Oct.16 (UT) 23:34 - 23:58. Afterglow candidate proposed by Chen (GCN 4105) and Kinoshita (GCN 4111) is detected in a stacked image. Preliminary photometry of the stacked image against of USNO A2.0 is following: Mid time, Exposure, Filter, Mag. (UT) (s) Oct.16.990 6x180 R 21.43 +/- 0.24 The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4186 SUBJECT: GRB 051016B host spectroscopy and redshift DATE: 05/11/02 19:10:28 GMT FROM: Alicia Soderberg at Caltech A. M. Soderberg, E. Berger and E. Ofek report on behalf of the Caltech-NRAO-Carnegie collaboration: "We observed the optical afterglow position (GCN 4105) of GRB 051016B (GCN 4103) with the Low Resolution Imaging Spectrometer on the Keck I telescope on 2005 October 31.6 UT. We detect an extended source in the g and r filters which we identify as the host galaxy. In a 900 sec spectrum we detect emission lines of [O II] and Ne III, at a redshift of z=0.9364." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4391 SUBJECT: GRB051016: analysis of the XMM-Newton observation DATE: 05/12/23 20:17:20 GMT FROM: Andrea De Luca at IASF-CNR,Milano Andrea De Luca (INAF/IASF, Milano) on behalf of a larger collaboration reports: We have analyzed the data from the XMM-Newton observation of GRB051016, discovered by Swift on 2005, October 16 at 05:23:31 UT (Boyd et al., GCN4096). The XMM-Newton observation started on 2005, October 16 at 13:44 UT and lasted for 29.4 ks. As reported by Loiseau and Perez-Martinez (GCN4101), the afterglow of GRB051016 is clearly detected in the EPIC images and its position is fully consistent with the refined Swift/XRT one (Morris et al., GCN3606). Extracting source events from a circle of 25 arcsec radius (containing ~80% of the total counts), the time-averaged, background-subtracted count rate in the 0.5-8 keV range is 0.028+/-0.001 cts/s, 0.0092+/-0.0006 cts/s and 0.0100+/-0.0006 cts/s in the pn, MOS1 and MOS2 cameras, respectively. The afterglow is seen to fade along the XMM-Newton observation, spanning the time range 30.0-59.4 ks after the GRB. The pn background-subtracted light curve (0.5-8 keV) is well fitted (reduced chi2=1.0, 7 d.o.f.) by a power law decay with index delta=0.9+/-0.3 (90% c.l.). The observed afterglow decay is consistent with the XRT results (Beardmore et al., GCN4100). We extracted the time-averaged spectra and generated ad-hoc response and effective area files for the pn, MOS1 and MOS2 cameras. The spectra were fitted simultaneously. Unless otherwise specified, we quote errors at 90% level for a single interesting parameter. A fit in the energy range 0.5-8 keV with an absorbed power law model yields an unacceptable reduced chi2 of 2.5 for 26 d.o.f., The resulting NH=(3.0+/-0.2)x10^21 cm^-2 is somewhat higher than the expected Galactic value in the burst direction (NH=1.1x10^21 cm^-2, Dickey & Lockman, 1990); the best fitting power law photon index is Gamma=2.6+/-0.3. A better fit may be obtained fixing the NH to the Galactic value and adding a redshifted neutral absorber. This yields a reduced chi2 of 1.74 for 25 d.o.f. The intrinsic gas column density and the redshift are not well constrained owing to their strong correlation. The best fit values are: intrinsic NH=6.7x10^22 cm^-2, z=4.1. At 90% confidence level for 2 parameters, the intrinsic NH is larger than 5x10^21 cm^-2 and the redshift is larger than 0.8. The best fit value of the power law photon index is Gamma=2.5+/-0.2. The observed flux (0.5-8 keV) is of 7.6x10^-14 erg cm^-2 s^-1, corresponding to an unabsorbed flux of 1.1x10^-13 erg cm^-2 s^-1.