//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22752 SUBJECT: GRB 180602A: Swift detection of a burst DATE: 18/06/02 08:35:07 GMT FROM: David Palmer at LANL S. B. Cenko (GSFC), J.D. Gropp (PSU), A. Y. Lien (GSFC/UMBC), A. Melandri (INAF-OAB), K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 08:14:50 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180602A (trigger=835200). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 142.339, +32.093 which is RA(J2000) = 09h 29m 21s Dec(J2000) = +32d 05' 34" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The burst appears to have been in progress as Swift was slewing to the pre-planned pointing target before the nominal trigger time. The BAT light curve showed a single peak structure with a duration of about 50 seconds, however the start of the peak may be due to the GRB entering the FOV during the slew. The peak count rate was ~1300 counts/sec (15-350 keV), at ~20 sec before the trigger. The XRT began observing the field at 08:16:55.2 UT, 124.3 seconds after the BAT trigger. The position determined from promptly downlinked data differs significantly from the on-board position, suggesting that the XRT may have centroided on a cosmic ray; the initial XRT position notice should be treated with caution. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 142.3319, 32.0661 which is equivalent to: RA(J2000) = 09h 29m 19.65s Dec(J2000) = +32d 03' 58.1" with an uncertainty of 2.2 arcseconds (radius, 90% containment). This location is 99 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 in excess of the Galactic value (1.56 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 6.1 (+2.76/-2.42) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 133 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 0.02. Burst Advocate for this burst is S. B. Cenko (brad.cenko AT 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: 22753 SUBJECT: GRB 180602A: Enhanced Swift-XRT position DATE: 18/06/02 10:38:54 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 2068 s of XRT Photon Counting mode data and 1 UVOT images for GRB 180602A, 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 = 142.33181, +32.06710 which is equivalent to: RA (J2000): 09h 29m 19.63s Dec (J2000): +32d 04' 01.6" 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: 22754 SUBJECT: GRB 180602A: MITSuME Okayama optical upper limits DATE: 18/06/02 12:30:27 GMT FROM: Yutaro Tachibana at Tokyo Tech Y. Tachibana, R. Itoh, K. L. Murata, S. Harita, K. Morita, T. Ozawa, H. Mamita, K. Shiraishi, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the field of GRB 180602A (Cenko et al., GCN Circular #22752) with the optical three color (g', Rc and Ic) CCD camera attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory. The observation started on 2018-06-02 11:14:03.47 UT (~3 hours after the burst). We did not find any new point source within the enhanced XRT error circle (Osborne et al., GCN Circular #22753) in all the three bands. We obtained following limits for the magnitudes. T0+[hour] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------- ~3.07 ~11:18:47 420 >17.8 >17.7 >17.1 ------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22755 SUBJECT: GRB 180602A: Swift-BAT refined analysis DATE: 18/06/02 17:18:13 GMT FROM: Amy Lien at GSFC A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), J. R. Cummings (CPI), 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 180602A (trigger #835200) (Cenko et al., GCN Circ. 22752). The BAT ground-calculated position is RA, Dec = 142.343, 32.080 deg which is RA(J2000) = 09h 29m 22.4s Dec(J2000) = +32d 04' 48.1" with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 78%. The mask-weighted light curve shows a single-peaked structure that starts at ~T-30 s, peaks at ~T-20 s, and ends at ~T+25 s. We note that the burst emission indeed started and peaked during a pre-planned spacecraft slew, and the trigger occurred near the end of the pulse when the slew settled. T90 (15-350 keV) is 45.4 +- 7.1 sec (estimated error including systematics). The time-averaged spectrum from T-29.32 to T+25.73 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.72 +- 0.11. The fluence in the 15-150 keV band is 1.6 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-20.12 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/835200/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22756 SUBJECT: GRB 180602A: Swift-XRT refined Analysis DATE: 18/06/03 02:52:27 GMT FROM: Phil Evans at U of Leicester J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), S. J. LaPorte (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU) and S.B. Cenko report on behalf of the Swift-XRT team: We have analysed 8.4 ks of XRT data for GRB 180602A (Cenko et al. GCN Circ. 22752), from 130 s to 59.7 ks after the BAT trigger. The data comprise 85 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 22753). The late-time light curve (from T0+5.6 ks) can be modelled with a power-law decay with a decay index of alpha=1.38 (+0.16, -0.13). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.36 (+0.28, -0.25). The best-fitting absorption column is 4.0 (+1.3, -1.1) x 10^21 cm^-2, in excess of the Galactic value of 1.6 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.04 (+0.16, -0.15) and a best-fitting absorption column of 4.2 (+0.8, -0.7) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (6.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 4.2 (+0.8, -0.7) x 10^21 cm^-2 Galactic foreground: 1.6 x 10^20 cm^-2 Excess significance: 9.1 sigma Photon index: 2.04 (+0.16, -0.15) If the light curve continues to decay with a power-law decay index of 1.38, the count rate at T+24 hours will be 7.3 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.8 x 10^-13 (4.5 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/00835200. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22757 SUBJECT: GRB 180602A: MITSuME Akeno optical upper limits DATE: 18/06/03 09:29:22 GMT FROM: Katsuhiro L. Murata at Nagoya U K. L. Murata, Y. Tachibana, R. Itoh, T. Yoshii, S. Harita, K. Morita, T. Ozawa, H. Mamiya, K. Shiraishi, K. Iida, M. Oeda, R. Adachi, S. Niwano, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We searched for the field of GRB 180602A (Cenko et al., GCN Circular #22752) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan. The observation started on 2018-06-02 11:12:09 UT (~3 hours after the burst). We did not find any new point source within the enhanced XRT error circle (Osborne et al., GCN Circular #22753) in all the three bands. T0+[hour] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------ ------------------------------------------- ~3.1 ~12:24 1200 >18.9 >18.3 >18.0 ------------------------------------------------------------ ------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22758 SUBJECT: GRB 180602A: Swift/UVOT Upper Limits DATE: 18/06/03 17:11:58 GMT FROM: Jeffrey Gropp at PSU J. Gropp (PSU) and S. B. Cenko (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180602A 133 s after the BAT trigger (Cenko et al., GCN Circ. 22752). No optical afterglow consistent with the enhanced XRT position (Osborne et al. GCN Circ. 22753) 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 133 283 147 >19.9 u_FC 291 541 246 >19.8 white 133 1715 411 >20.8 v 621 2283 194 >19.0 b 547 2208 175 >20.0 u 291 2183 401 >20.3 w1 670 2159 175 >20.0 m2 645 665 19 >18.7 w2 597 2086 136 >20.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22760 SUBJECT: GRB 180602A: MITSuME Ishigakijima optical upper limits DATE: 18/06/04 16:41:32 GMT FROM: Yutaro Tachibana at Tokyo Tech T. Horiuchi, H. Hanayama, M. Honma (IAO, NAOJ), Y. Tachibana, R. Itoh, K. L. Murata, 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 180602A (Cenko et al., GCN Circular #22752, Osborne et al., GCN Circular #22753, Gropp and Cenko, GCN Circular #22758) with the optical three color (g', Rc, and Ic) CCD cameras attached to the Murikabushi 1m telescope of Ishigakijima Astronomical Observatory. The observation started on 2018-06-02 12:38:23 UT. We did not find any point source at the position of the XRT error circle in all three bands. We obtained following 3-sigma upper limits: T0+[hour] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------- ~4.5 12:51:13.3 1,560 >19.4 >19.1 >18.7 ------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used UCAC-4 catalog for flux calibration.