//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21308 SUBJECT: GRB 170710A: Swift detection of a burst DATE: 17/07/10 00:57:28 GMT FROM: David Palmer at LANL P. A. Evans (U Leicester), D. N. Burrows (PSU), A. Cholden-Brown (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Swift Team: At 00:45:44 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 170710A (trigger=761119). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 231.812, -38.547 which is RA(J2000) = 15h 27m 15s Dec(J2000) = -38d 32' 48" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 10 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 00:47:48.3 UT, 123.7 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 231.82076, -38.48434 which is equivalent to: RA(J2000) = 15h 27m 16.98s Dec(J2000) = -38d 29' 03.6" with an uncertainty of 4.4 arcseconds (radius, 90% containment). This location is 226 arcseconds from the BAT onboard position. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. No spectrum from the promptly downlinked event data is yet available to determine the column density. The initial flux in the 2.5 s image was 4.07e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 131 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 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 0.17. Burst Advocate for this burst is P. A. Evans (pae9 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: 21309 SUBJECT: GRB 170710A: Prompt enhanced Swift-XRT position DATE: 17/07/10 01:33:45 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Using promptly downlinked XRT event data for GRB 170710A, we find an enhanced XRT position of the afterglow: RA, Dec: 231.8199, -38.4852 which is equivalent to: RA (J2000) = 15 27 16.77 Dec (J2000) = -38 29 06.6 with an uncertainty of 2.3 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/761119. Position enhancement is is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21310 SUBJECT: GRB 170710A: Enhanced Swift-XRT position DATE: 17/07/10 06:58:48 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 3131 s of XRT Photon Counting mode data and 4 UVOT images for GRB 170710A, 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 = 231.82030, -38.48496 which is equivalent to: RA (J2000): 15h 27m 16.87s Dec (J2000): -38d 29' 05.8" with an uncertainty of 1.9 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: 21311 SUBJECT: GRB 170710A: Gemini-S candidate counterpart DATE: 17/07/10 11:04:40 GMT FROM: Antonino Cucchiara at UVI A. Cucchiara (U. of the Virgin Islands) reports on behalf of a larger collaboration: "On July 10.17UT we imaged the field of GRB 170710A (Evans et al. GCN 21308, 21309, Osborne et al. GCN 21310) with the Gemini-South Telescope equipped with the GMOS camera. We obtained 4x900s spectra covering the 5660-10300 Angstrom wavelength range. In our single 180 seconds acquisition image in i' band centered on the Swift-XRT position we identified an uncatalogued point-like sources at the edge of the refined position: RA= +15:27:16.87 Dec= -38:29:06.0 Using nearby USNO-B1 stars for calibration, we measure a magnitude of i' = 21.13 +/- 0.05. At this point it is not possible to assess the variability of this possible counterpart. Preliminary analysis of the spectra reveals a faint trace clearly visible down to the blue end of the spectrum. No clear absorption or emission features are evident, but more detailed analysis of the data is in progress. We thank the Gemini staff for the prompt response, in particular Veronica Firpo." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21312 SUBJECT: GRB 170710A: Swift-XRT refined Analysis DATE: 17/07/10 12:13:53 GMT FROM: Phil Evans at U of Leicester J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), B. Mingo (U. Leicester) and P. A. Evans (U Leicester) report on behalf of the Swift-XRT team: We have analysed 9.8 ks of XRT data for the Swift/BAT-detected burst GRB 170710A (Evans et al. GCN Circ. 21308), from 114 s to 30.4 ks after the Swift/BAT trigger. The data comprise 102 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 21309). The light curve can be modelled with an initial power-law decay with an index of alpha=4.43 (+0.26, -0.23), followed by a break at T+446 s to an alpha of 0.49 (+0.07, -0.08). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.81 (+/-0.10). The best-fitting absorption column is 3.6 (+/-0.3) x 10^21 cm^-2, in excess of the Galactic value of 1.8 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.96 (+0.28, -0.26) and a best-fitting absorption column of 2.5 (+1.2, -0.7) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (5.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.5 (+1.2, -0.7) x 10^21 cm^-2 Galactic foreground: 1.8 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 1.96 (+0.28, -0.26) If the light curve continues to decay with a power-law decay index of 0.49, the count rate at T+24 hours will be 0.011 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.1 x 10^-13 (5.7 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00761119. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21313 SUBJECT: GRB 170710A: Swift-BAT refined analysis DATE: 17/07/10 17:03:52 GMT FROM: Amy Lien at GSFC A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), P. A. Evans (U Leicester), H. A. Krimm (NSF/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-240 to T+607 sec from the recent telemetry downlink, we report further analysis of BAT GRB 170710A (trigger #761119) (Evans et al., GCN Circ. 21308). The BAT ground-calculated position is RA, Dec = 231.851, -38.523 deg which is RA(J2000) = 15h 27m 24.2s Dec(J2000) = -38d 31' 22.2" with an uncertainty of 3.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 22%. The mask-weighted light curve shows a single-peaked structure that starts and peaks at ~T0, and ends at ~T+37 s. T90 (15-350 keV) is 32.6 +- 10.5 sec (estimated error including systematics). The time-averaged spectrum from T+0.16 to T+36.91 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.91 +- 0.37. The fluence in the 15-150 keV band is 7.4 +- 1.7 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.48 sec in the 15-150 keV band is 1.0 +- 0.3 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/761119/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21315 SUBJECT: GRB170710A: Swift/UVOT detection DATE: 17/07/10 19:37:22 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL), F. E. Marshall (NASA/GSFC) and P. A. Evans (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 170710A 132 s after the BAT trigger (Evans et al., GCN Circ. 21308). An optical afterglow consistent with the enhanced XRT position (Osborne et al., GCN Circ. 21310) and Gemini position (Cuchhiara, GCN Circ. 21311) is detected in the initial UVOT white finding chart. Preliminary detection and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 132 281 147 20.95 +/- 0.3 white 5808 6007 197 >21.0 v 2122 2141 19 >17.9 b 546 565 19 >18.9 u 290 539 246 >20.2 w1 2171 2166 20 >17.1 w2 2098 2117 20 >17.6 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.172 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21967 SUBJECT: GRB 170710A: LCO Observations DATE: 17/10/04 12:24:38 GMT FROM: Antonino Cucchiara at UVI A. Cucchiara (U. Virgin Islands) report on behalf of a larger collaboration: "On July 10.05 UT (T_0 +30 min) we began observing the center of the field of GRB 170710A (Evans et al. GCN 21308, Osborne et al. GCN 21310) using the Las Cumbres Observatory 1m telescope located in Cerro Tololo. We performed a series of 10x60s observations in SDSS I band for a total of 10 minutes on sky. In the full median stacked images we identified no optical counterpart at the location of the optical counterpart (Cucchiara et al. GCN 21311, Breeveld et al. GCN 21315). Nevertheless, at the OT location we identified a 2-sigma excess corresponding to I=21.28 +- 0.24 mag, consistent with other observations at similar time post-burst. These magnitudes are calibrated against nearby USNO-B1 sources, and not corrected for Galactic extinction."