//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14331 SUBJECT: GRB 130327A: Swift detection of a burst DATE: 13/03/27 02:09:19 GMT FROM: Jamie A. Kennea at PSU/Swift-XRT T. N. Ukwatta (MSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), V. Mangano (INAF-IASFPA), C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC), A. Maselli (INAF-IASFPA), D. M. Palmer (LANL), M. H. Siegel (PSU) and C. A. Swenson (PSU) report on behalf of the Swift Team: At 01:47:34 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 130327A (trigger=552063). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 91.992, +55.730 which is RA(J2000) = 06h 07m 58s Dec(J2000) = +55d 43' 49" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a weak single peak with a duration of about 10 sec. The peak count rate was ~900 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 01:49:55.0 UT, 141.0 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 92.0387, 55.7143 which is equivalent to: RA(J2000) = 06h 08m 09.29s Dec(J2000) = +55d 42' 51.5" with an uncertainty of 2.7 arcseconds (radius, 90% containment). This location is 110 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. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 1.31 x 10^21 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 150 seconds with the White filter starting 104 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 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 0.13. Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta AT gmail.com). 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: 14333 SUBJECT: GRB 130327A: PAIRITEL NIR Afterglow Candidate DATE: 13/03/27 03:39:24 GMT FROM: Adam Morgan at U.C. Berkeley A. N. Morgan (UC Berkeley) reports: We observed the field of GRB 130327A (Ukwatta et al., GCN 14331) with the 1.3m PAIRITEL located at Mt. Hopkins, Arizona. Observations began at 2013-Mar-27 02h21m22s UT, ~33.8 minutes after the Swift trigger. In mosaics (effective exposure time of ~25 m) taken simultaneously in the J, H, and Ks filters, we marginally detect a source in the J band within the XRT error circle (Ukwatta et al., GCN 14331). Given the minor significance of the detection in only a single filter, deeper observations are encouraged to confirm if this possible source is indeed the afterglow of GRB 130327A. post burst t_mid (hr) exp.(hr) filt Mag 0.91 0.42 J 17.8 +/- 0.4 0.91 0.42 H > 17.1 0.91 0.42 Ks > 15.7 All magnitudes are given in the Vega system, calibrated to 2MASS. No correction for Galactic extinction has been made to the above reported values. Observations are ongoing. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14334 SUBJECT: GRB 130327A: RATIR Optical and NIR Observations DATE: 13/03/27 04:56:14 GMT FROM: Nat Butler at UC berkeley Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB) J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC), Eleonora Troja (GSFC), Enrico Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report: We observed the field of GRB 130327A (Ukwatta, et al., GCN 14331) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2013/03 27.12 to 2013/03 27.17 UTC (1.16 to 2.17 hours after the BAT trigger), obtaining a total of 0.82 hours exposures in the r' and i' bands and 0.35 hours of exposure in the Z, Y, J, and H bands. We detect one uncatalogued source within the XRT error region (GCN 14331), at a position RA , DEC: = 92.03875, 55.71504 (+/-0.5 ", J2000). This is 2.7" from the center of the XRT error circle. In comparison with USNO-B1 and 2MASS, we derive the following detections and upper limit (3-sigma) in the AB magnitude system: r' 21.22 +/- 0.10 i' 21.17 +/- 0.09 Z 20.09 +/- 0.14 Y 19.98 +/- 0.17 J 19.98 +/- 0.23 H > 20.08 We also detect a second uncatalogued source just outside the XRT error circle (3.9" from the center) at RA , DEC: 92.03822, 55.71326 (+/-0.5 ", J2000): r' 21.61 +/- 0.14 i' 20.36 +/- 0.05 Z 19.15 +/- 0.06 Y 18.72 +/- 0.06 J 18.70 +/- 0.07 H 18.53 +/- 0.09 We note that this second source has a brightness consistent with the earlier PAIRITEL measurement (Morgan; GCN 14333). We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. Further observations are planned. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14335 SUBJECT: GRB 130327A: Enhanced Swift-XRT position DATE: 13/03/27 07:49:55 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 1239 s of XRT Photon Counting mode data and 2 UVOT images for GRB 130327A, 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 = 92.03858, +55.71475 which is equivalent to: RA (J2000): 06h 08m 9.26s Dec (J2000): +55d 42' 53.1" 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: 14337 SUBJECT: GRB 130327A: ISON-NM optical upper limit DATE: 13/03/27 09:59:23 GMT FROM: Alexei Pozanenko at IKI, Moscow L. Elenin (KIAM), A. Volnova (SAI MSU), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 130327A (Ukwatta, et al., GCN 14331) with 0.45-m telescope of ISON-NM observatory on Mar. 27, between (UT) 02:44:04 - 03:27:54. We took several unfiltered images of 30 s exposures. Within enhanced XRT afterglow position (Osborne et al., GCN 14335) we do not detect any new object. We marginally (S/N~2.5, R~ 20.3) detected "second uncatalogued source" (Morgan et al., GCN 14333; Butler et al., GCN 14334) at RA , DEC (J2000): 06 08 09.06 +55 42 48.5. A photometry of combined image is based on the USNO-B1.0 (R2) nearby stars Start, T0+, Exposure, OT, UL (3 sigma) (UT) mid, d (s) 02:44:04 0.0546 60x30 n/d 20.0 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14339 SUBJECT: GRB 130327A: Swift/UVOT Upper Limits DATE: 13/03/27 14:22:35 GMT FROM: Craig Swenson at PSU/Swift C. A. Swenson (PSU) and T. N. Ukwatta (MSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 130327A 104 s after the BAT trigger (Ukwatta et al., GCN Circ. 14331). No optical afterglow consistent with the XRT position (Osborne et al. GCN Circ. 14335) is detected in the initial UVOT exposures. Preliminary 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 104 254 147 >21.2 u_FC 317 567 246 >20.0 white 104 6491 727 >21.8 v 646 6877 428 >19.8 b 572 6286 432 >20.7 u 317 6081 659 >20.4 w1 695 12014 1111 >21.6 m2 671 11107 1141 >21.0 w2 622 6696 452 >21.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.13 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14340 SUBJECT: GRB 130327A: Weihai optical obsevations DATE: 13/03/27 17:51:32 GMT FROM: Dong Xu at DARK/NBI D. Xu (DARK/NBI), C. Cao, S. M. Hu (SDU) report: We observed the field of GRB 130327A (Ukwatta et al., GCN 14331) using the 1m telescope located in Weihai, Shandong Province, China. Observations started at 11:27:02 UT on 2013-03-27 (i.e, 9.658 hr after the burst) in a seeing of ~2.8", and 10x360s I-band images were obtained with a mean time of 10.158 hr post-burst. Within the enhanced XRT error circle (Osborne et al., GCN 14335), no credible source is detected in the stacked I-band image, down to a limit of R>20.2 mag, calibrated with the USNO B1 catalogue. A source, with R~19.2 mag and somehow extended along NW-SE, is detected at the position of the "second uncatalogued source" reported by Butler et al. (GCN 14334), and confirmed in Elenin et al. (GCN 14337). This source might be the one in Morgan (GCN 14333). Since it is 5.5" away from the center of the enhanced XRT error circle (radius: 1.9") and it's getting brightening significantly, this source is unlikely related to the afterglow of the burst. We thank Dayong Ren for carrying out thee observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14341 SUBJECT: GRB 130327A: Swift-XRT refined Analysis DATE: 13/03/27 19:09:04 GMT FROM: Phil Evans at U of Leicester C. Pagani (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. Maselli (INAF-IASFPA), D.N. Burrows (PSU), J.A. Kennea (PSU), M.C. Stroh (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester) and T.N. Ukwatta report on behalf of the Swift-XRT team: We have analysed 10 ks of XRT data for GRB 130327A (Ukwatta et al. GCN Circ. 14331), from 83 s to 45.1 ks after the BAT trigger. The data comprise 902 s in Windowed Timing (WT) mode (the first 9 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 14335). The light curve can be modelled with an initial power-law decay with an index of alpha=4.3 (+0.5, -0.4), followed by a break at T+348 s to an alpha of 0.22 (+0.07, -0.08). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.28 (+0.29, -0.13). The best-fitting absorption column is consistent with the Galactic value of 1.3 x 10^21 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.2 x 10^-11 (4.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 0 (+3.7, -0) x 10^20 cm^-2 Galactic foreground: 1.3 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 2.28 (+0.29, -0.13) If the light curve continues to decay with a power-law decay index of 0.22, the count rate at T+24 hours will be 0.012 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.7 x 10^-13 (4.8 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/00552063. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14342 SUBJECT: GRB 130327A: Gemini Observations DATE: 13/03/27 21:20:55 GMT FROM: Antonino Cucchiara at UCSC/UCO Lick A. Cucchiara (UCSC/UCO Lick Observatory) and S. B. Cenko (UC Berkeley) report on behalf of a large collaboration: "On March 27.25 UT we observed the field of GRB 130327A (Ukwatta et al., GCN 14331) with the Gemini-North telescope equipped with the GMOS camera. We obtained a 4 minutes i' band image of the field: the two sources identified by Butler et al. (GCN 14334) are both detected. The southern source (#1) is located at RA: 06:08:09.12 (J2000) Dec: +55:42:47.98 (J2000) The northern source (#2) is located inside the XRT revised error circle (Osborne et al. GCN 14335) at: RA: 06:08:09.25 (J2000) Dec: +55:42:54.39 (J2000) Using several nearby USNO-B1 stars we estimated i' = 19.81 +- 0.02, (source #1), and i' = 21.75 +- 0.06 (source #2), which is 0.43 mag fainter than the RATIR observations. We also obtained a 2x900s spectra of these two sources under cloudy conditions, covering the 6000-10000A wavelength range: source #1 presents several stellar features, while source #2 presents a noisy continuum, but no clear absorption features are identified. If we assume that source #2 is indeed GRB 130327A afterglow, we can place an upper limit on the GRB redshift of z < 3.9, based on the absence of a Lyman-break features. Our acquisition image can be found here: https://www.dropbox.com/s/ygvcdykmpow6gq5/sources.jpeg We thank the Gemini staff for performing this observations, in particular Andre'-Nicolas Chene' " //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14343 SUBJECT: GRB 130327A: Swift-BAT refined analysis DATE: 13/03/27 21:54:49 GMT FROM: Scott Barthelmy at NASA/GSFC 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), A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT GRB 130327A (trigger #552063) (Ukwatta, et al., GCN Circ. 14140). The BAT ground-calculated position is RA, Dec = 91.984, 55.732 deg, which is RA(J2000) = 06h 07m 56.2s Dec(J2000) = +55d 43' 56.2" with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 61%. The mask-weighted lightcurve shows a single peak starting at ~T-5 sec, peaking at ~T+1 sec, and ending at ~T+8 sec. T90 (15-350 keV) is 9.0 +- 2.8 sec (estimated error including systematics). The time-averaged spectrum from T-4.38 to T+5.62 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.26 +- 0.36. The fluence in the 15-150 keV band is 2.3 +- 0.5 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.62 sec in the 15-150 keV band is 0.9 +- 0.2 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/552063/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14352 SUBJECT: GRB 130327A: RATIR Optical/NIR afterglow confirmation DATE: 13/03/29 00:21:46 GMT FROM: Antonino Cucchiara at UCSC/UCO Lick Antonino Cucchiara (UCSC), Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB) J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Eleonora Troja (GSFC), Enrico Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report: We reobserved the field of GRB 130327A (Ukwatta et al., GCN 14331, and Osborne et al., GCN 14335) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2013/03 28.13 to 2013/03 28.14 UTC (25.24 to 25.64 hours after the BAT trigger), obtaining a total of 0.33 hours exposure in the r' and i' bands and 0.14 hours of exposure in the Z, Y, J, and H bands. The source identified in our previous RATIR observations within the refined XRT error circle (Butler et al. GCN 14334), and detected by Gemini (source #2 in GCN 14342) has faded below our detection limit. We report the following 3-sigma limits in the AB magnitude system: r' > 22.67 i' > 22.46 Z > 20.83 Y > 20.47 J > 20.07 H > 19.99 This fading is consistent with the fading reported by Cucchiara et al. (GCN 14342). Based on these observations we confirm that this was the optical/NIR afterglow of GRB 130327A. The second source identified outside the refined XRT error circle in the first RATIR observation and detected also by Gemini (as source #1 in GCN 14342) has not faded. Therefore it is unrelated to GRB 130327A. These magnitudes are not corrected for Galactic extinction in the direction of the GRB. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. [GCN OPS NOTE(29mar13): Per author's request, the name in the Subject-line was changed from "130727A" to "130327A".]