//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22872 SUBJECT: GRB 180630A: Swift detection of a burst with an optical counterpart DATE: 18/06/30 11:23:40 GMT FROM: Caryl Gronwall at PSU/Swift-UVOT P. D'Avanzo (INAF-OAB), C. Gronwall (PSU), J.D. Gropp (PSU), J. A. Kennea (PSU), H. A. Krimm (NSF/USRA), F. E. Marshall (NASA/GSFC) and T. Sakamoto (AGU) report on behalf of the Neil Gehrels Swift Observatory Team: At 11:11:51 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180630A (trigger=845443). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 48.810, -87.482 which is RA(J2000) = 03h 15m 14s Dec(J2000) = -87d 28' 54" 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 ~6500 counts/sec (15-350 keV), at ~4 sec after the trigger. The XRT began observing the field at 11:13:13.4 UT, 81.6 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 48.95887, -87.47850 which is equivalent to: RA(J2000) = 03h 15m 50.13s Dec(J2000) = -87d 28' 42.6" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 26 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 1.34 x 10^21 cm^-2 (Willingale et al. 2013). The initial flux in the 2.5 s image was 6.12e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 87 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 03:15:56.02 = 48.98342 DEC(J2000) = -87:28:42.4 = -87.47844 with a 90%-confidence error radius of about 0.62 arc sec. This position is 5.7 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.44 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.13. Burst Advocate for this burst is P. D'Avanzo (paolo.davanzo AT brera.inaf.it). 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: 22873 SUBJECT: GRB 180630A: Enhanced Swift-XRT position DATE: 18/06/30 15:42:40 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 1171 s of XRT Photon Counting mode data and 1 UVOT images for GRB 180630A, 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 = 48.98081, -87.47880 which is equivalent to: RA (J2000): 03h 15m 55.39s Dec (J2000): -87d 28' 43.7" with an uncertainty of 1.7 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: 22875 SUBJECT: GRB 180630A: Fermi GBM detection DATE: 18/06/30 16:54:15 GMT FROM: Rachel Hamburg at UAH R. Hamburg (UAH), A. von Kienlin (MPE), and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 11:11:54.41 UT on 30 June 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180630A (trigger 552049919 / 180630467) which was also detected by the Swift BAT and XRT instruments (D'Avanzo et al. 2018, GCN 22872). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 20 degrees. The GBM light curve consists of a single structured peak with a duration (T90) of about 12 s (50-300 keV). The time-averaged spectrum from T0-1.54s to T0+8.70 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.37 +/- 0.09 and the cutoff energy, parameterized as Epeak, is 84 +/- 8 keV. A Band function fits the spectrum equally well with Epeak = 60 +/- 10 keV, alpha = -1.11 +/- 0.20, and beta = -2.32 +/- 0.16. The event fluence (10-1000 keV) in this time interval is (2.5 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.15 s in the 10-1000 keV band is 9.4 +/- 0.4 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22876 SUBJECT: GRB 180630A: Swift-XRT refined Analysis DATE: 18/06/30 21:33:37 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester), Z. Liu (NAOC / U. Leicester), A. Melandri (INAF-OAB), V. D'Elia (ASDC), A. Tohuvavohu (PSU), S. J. LaPorte (PSU), J.A. Kennea (PSU) and P. D'Avanzo report on behalf of the Swift-XRT team: We have analysed 6.3 ks of XRT data for GRB 180630A (D'Avanzo et al. GCN Circ. 22872), from 87 s to 29.0 ks after the BAT trigger. The data comprise 69 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 22873). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=3.04 (+0.61, -0.21). At T+155 s the decay flattens to an alpha of 0.25 (+0.26, -0.09). The light curve breaks again at T+659 s to a decay with alpha=0.80 (+0.07, -0.05), before a final break at T+24.3 ks s after which the decay index is 4.4 (+3.6, -2.2). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.91 (+0.21, -0.17). The best-fitting absorption column is consistent with the Galactic value of 1.3 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.64 (+/-0.12) and a best-fitting absorption column of 1.7 (+0.5, -0.3) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.3 x 10^-11 (5.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.7 (+0.5, -0.3) x 10^21 cm^-2 Galactic foreground: 1.3 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 1.64 (+/-0.12) If the light curve continues to decay with a power-law decay index of 4.4, the count rate at T+24 hours will be 4.3 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.8 x 10^-14 (2.2 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/00845443. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22877 SUBJECT: GRB 180630A: Swift-BAT refined analysis DATE: 18/07/01 12:30:12 GMT FROM: Takanori Sakamoto at AGU A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (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-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180630A (trigger #845443) (D'Avanzo, et al., GCN Circ. 22872). The BAT ground-calculated position is RA, Dec = 48.885, -87.476 deg which is RA(J2000) = 03h 15m 32.5s Dec(J2000) = -87d 28' 33.4" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 59%. The mask-weighted light curve shows a double-peaked structure. The first pulse starts at T0, peaks at T+4 sec and ends at T+15 sec. The second weak pulse starts at T+15 sec and ends at T+30 sec. T90 (15-350 keV) is 18.85 +- 6.45 sec (estimated error including systematics). The time-averaged spectrum from T-0.36 to T+30.02 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.07 +- 0.10. The fluence in the 15-150 keV band is 1.8 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+3.65 sec in the 15-150 keV band is 6.6 +- 0.4 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/845443/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22881 SUBJECT: GRB 180630A: Swift/UVOT Detection DATE: 18/07/02 01:46:46 GMT FROM: Sam LaPorte at PSU GRB 180630A: Swift/UVOT Detection S. J. LaPorte (PSU) and P. D'Avanzo (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180630A 88 s after the BAT trigger (D'Avanzo et al., GCN Circ. 22872). A fading source consistent with the XRT position (Beardmore et al. GCN Circ. 22873) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 03:15:55.74 = 48.98224 (deg.) Dec (J2000) = -87:28:42.3 = -87.47842 (deg.) with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 88 237 148 17.49 +/- 0.04 white 6384 6584 196 19.50 +/- 0.11 v 629 1597 117 18.56 +/- 0.20 b 555 748 39 18.76 +/- 0.19 u 300 549 246 17.76 +/- 0.06 w1 678 7392 510 19.42 +/- 0.17 m2 654 7187 452 20.16 +/- 0.33 w2 605 6777 255 >19.9 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).