//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22620 SUBJECT: GRB 180410A: Swift detection of a burst or a Galactic transient. DATE: 18/04/10 08:27:45 GMT FROM: Kim Page at U.of Leicester J.D. Gropp (PSU), A. Deich (PSU), P. A. Evans (U Leicester), C. Gronwall (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC) and K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift Observatory Team: At 08:02:59 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180410A or a Galactic transient (trigger=824063). Swift slewed immediately to the source. The BAT on-board calculated location is RA, Dec 95.981, +12.808 which is RA(J2000) = 06h 23m 56s Dec(J2000) = +12d 48' 28" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure structure with a duration of about 100 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~26 sec after the trigger. The XRT began observing the field at 08:05:49.8 UT, 170.7 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 95.9570, 12.8110 which is equivalent to: RA(J2000) = 06h 23m 49.68s Dec(J2000) = +12d 48' 39.4" with an uncertainty of 2.1 arcseconds (radius, 90% containment). This location is 84 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 6.56 x 10^21 cm^-2 (Willingale et al. 2013). The initial flux in the 2.5 s image was 1.55e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 179 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 large, but uncertain, extinction expected. Given the source's proximity (0.17 degrees) to the Galactic Plane, and the fact that this is a BAT image trigger, we cannot rule out that this may be a new Galactic Transient, rather than a GRB. If it is a transient, we name it Swift J0623.9+1248. Burst Advocate for this burst is J.D. Gropp (jdg44 AT psu.edu). 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: 22622 SUBJECT: GRB 180410A: Enhanced Swift-XRT position DATE: 18/04/10 11:09:33 GMT FROM: Phil Evans at U of Leicester P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 1707 s of XRT Photon Counting mode data and 1 UVOT images for GRB 180410A, 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 = 95.95717, +12.81143 which is equivalent to: RA (J2000): 06h 23m 49.72s Dec (J2000): +12d 48' 41.1" 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: 22623 SUBJECT: GRB 180410A: MITSuME Akeno optical upper limits DATE: 18/04/10 12:31:10 GMT FROM: Ryosuke Itoh at Tokyo Institute of Tech. R. Itoh, K. L. Murata, Y. Tachibana, S. Harita, K. Morita, T. Ozawa, H. Mamiya, K. Shiraishi, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We searched for the optical counterpart of GRB 180410A (J. D. Gropp et al., GCN Circular #22620) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50cm telescope of Akeno Observatory, Yamanashi, Japan. The observation started on 2018-04-10 10:02:24 UT. We did not find any point source at the position of the XRT error circle (P. A. Evans et al., GCN Circular #22622) in all three bands. We obtained following limits for the magnitudes. T0+[hour] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------- ~2.0 10:27:25 2,700 >18.8 >18.7 >18.0 ------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used UCAC-4 catalog for flux calibration. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22627 SUBJECT: GRB 180410A: Swift/UVOT Upper Limits DATE: 18/04/10 18:18:04 GMT FROM: Frank Marshall at Swift/UVOT F. E. Marshall (NASA/GSFC) and J. D. Gropp (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180410A 179 s after the BAT trigger (Gropp et al., GCN Circ. 22620). No optical afterglow consistent with the enhanced XRT position (Evans et al. GCN Circ. 22622) 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 179 329 147 >20.6 u_FC 338 587 246 >20.0 white 179 2068 450 >20.9 v 669 1943 156 >19.2 b 594 2043 156 >20.1 u 338 2017 382 >20.4 w1 718 1993 136 >20.1 m2 693 1968 136 >20.3 w2 644 2093 175 >19.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.92 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22628 SUBJECT: GRB 180410A: Swift-BAT refined analysis DATE: 18/04/10 21:03:41 GMT FROM: Amy Lien at GSFC A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), J. D. Gropp (PSU), 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-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180410A (trigger #824063) (Gropp et al., GCN Circ. 22620). The BAT ground-calculated position is RA, Dec = 95.974, 12.804 deg which is RA(J2000) = 06h 23m 53.7s Dec(J2000) = +12d 48' 15.2" with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 53%. The mask-weighted light curve shows a weak-long pulse that starts and peak at ~ T+25 s, and ends at ~T+150 s. T90 (15-350 keV) is 100.7 +- 13.8 sec (estimated error including systematics). The time-averaged spectrum from T+25.16 to T+153.67 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.46 +- 0.13. The fluence in the 15-150 keV band is 2.2 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+25.70 sec in the 15-150 keV band is 0.7 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The spectral and temporal behaviors are consistent with those of a GRB. However, due to the proximity to the Galactic plane (0.17 degrees), we cannot rule out the possibility that this is a Galactic transient. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/824063/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22629 SUBJECT: GRB 180410A: Swift-XRT refined Analysis DATE: 18/04/10 23:40:51 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester), Z. Liu (NAOC / 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) and J.D. Gropp report on behalf of the Swift-XRT team: We have analysed 6.8 ks of XRT data for GRB 180410A (Gropp et al. GCN Circ. 22620), from 176 s to 45.6 ks after the BAT trigger. The data comprise 201 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 22622). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=1.39 (+0.22, -0.28). At T+321 s the decay steepens to an alpha of 2.9 (+0.4, -0.3) before breaking again at T+866 s to a final decay with index alpha=1.48 (+0.15, -0.13). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.87 (+0.07, -0.05). The best-fitting absorption column is consistent with the Galactic value of 6.6 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.45 (+0.21, -0.19) and a best-fitting absorption column of 7.7 (+2.3, -1.2) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 6.2 x 10^-11 (8.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 7.7 (+2.3, -1.2) x 10^21 cm^-2 Galactic foreground: 6.6 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 1.45 (+0.21, -0.19) If the light curve continues to decay with a power-law decay index of 1.48, the count rate at T+24 hours will be 6.1 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.7 x 10^-14 (4.9 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/00824063. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22631 SUBJECT: GRB 180410A: RATIR Optical Observations DATE: 18/04/11 16:03:38 GMT FROM: Alan M. Watson at Instituto de Astronomia UNAM Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report: We observed the field of GRB 180410A (Gropp et al., GCN 22620) 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 2018/04 11.13 to 2018/04 11.25 UTC (19.10 to 21.87 hours after the BAT trigger), obtaining a total of 2.13 hours exposure in the r and i bands. For a source within the Swift-XRT error circle, in comparison with the USNO-B1 and 2MASS catalogs, we obtain the following upper limits (3-sigma): r > 24.20 i > 23.90 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. The XRT error region is only 2.8 arcsec from a previously cataloged star with r = 18.1 and i = 17.4. Thus, our formal upper limits given above may be optimistic. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22636 SUBJECT: GRB 180410A: Fermi GBM observation DATE: 18/04/12 08:27:16 GMT FROM: Elisabetta Bissaldi at INFN,Bari E. Bissaldi (Politecnico & INFN Bari) reports on behalf of the Fermi GBM Team: "At 08:03:27.79 UT on 10 April 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180410A (trigger 545040212 / 180410336), which was also detected by the Swift/BAT (Gropp et al. 2018, GCN 22620, Lien et al., GCN 22628). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 108 degrees. The GBM light curve consists of an initial peak followed by a weaker emission episode with a duration (T90) of about 100 s (50-300 keV). The time-averaged spectrum from T0-3 s to T0+47 s is adequately fit by a simple power law function with index -1.53 +/- 0.04. The event fluence (10-1000 keV) in this time interval is (3.1 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-1.5 s in the 10-1000 keV band is 1.51 +/- 0.27 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."