//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22335 SUBJECT: GRB 180115A: Swift detection of a burst with an optical counterpart. DATE: 18/01/15 04:27:22 GMT FROM: David Palmer at LANL J. K. Cannizzo (NASA/UMBC), J. R. Cummings (NASA/UMBC), A. D'Ai (INAF-IASFPA), V. D'Elia (ASDC), A. Deich (PSU), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 04:16:03 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180115A (trigger=805318). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 12.073, -15.608 which is RA(J2000) = 00h 48m 18s Dec(J2000) = -15d 36' 27" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is usual for an image trigger, the immediately available light curve shows no obvious variation. The XRT began observing the field at 04:18:14.7 UT, 131.1 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 12.03953, -15.62924 which is equivalent to: RA(J2000) = 00h 48m 09.49s Dec(J2000) = -15d 37' 45.3" with an uncertainty of 3.8 arcseconds (radius, 90% containment). This location is 138 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. 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 3.57e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 140 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 00:48:09.25 = 12.03856 DEC(J2000) = -15:37:49.8 = -15.63051 with a 90%-confidence error radius of about 0.75 arc sec. This position is 5.6 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.54 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02. Burst Advocate for this burst is J. K. Cannizzo (cannizzo AT milkyway.gsfc.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: 22337 SUBJECT: GRB 180115A: Enhanced Swift-XRT position DATE: 18/01/15 10:45:08 GMT FROM: Phil Evans at U of Leicester M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 3943 s of XRT Photon Counting mode data and 7 UVOT images for GRB 180115A, 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 = 12.03876, -15.63065 which is equivalent to: RA (J2000): 00h 48m 9.30s Dec (J2000): -15d 37' 50.3" 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: 22338 SUBJECT: GRB 180115A: Swift-XRT refined Analysis DATE: 18/01/15 11:09:44 GMT FROM: Phil Evans at U of Leicester J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), D.N. Burrows (PSU) and J.K. Cannizzo report on behalf of the Swift-XRT team: We have analysed 6.6 ks of XRT data for GRB 180115A (Cannizzo et al. GCN Circ. 22335), from 137 s to 13.1 ks after the BAT trigger. The data comprise 86 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 22337). The light curve can be modelled with an initial power-law decay with an index of alpha=3.6 (+0.6, -0.5), followed by a break at T+269 s to an alpha of 0.71 (+/-0.04). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.26 (+0.13, -0.12). The best-fitting absorption column is consistent with the Galactic value of 1.7 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.94 (+0.12, -0.11) and a best-fitting absorption column of 3.6 (+2.4, -2.0) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10^-11 (3.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.6 (+2.4, -2.0) x 10^20 cm^-2 Galactic foreground: 1.7 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.94 (+0.12, -0.11) If the light curve continues to decay with a power-law decay index of 0.71, the count rate at T+24 hours will be 0.025 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.3 x 10^-13 (9.0 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/00805318. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22340 SUBJECT: GRB 180115A: MITSuME Akeno optical upper limits DATE: 18/01/15 11:42:54 GMT FROM: Katsuhiro L. Murata at Nagoya U K. L. Murata, R. Itoh,T. Yoshii, 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 180115A (Cannizzo et al., GCN Circular #22335) 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 2018-01-15 09:25:40 UT. We did not find the previously reported candidate afterglow (Cannizzo et al., GCN Circular #22335) in all three bands. We obtained following limits for the magnitudes. T0+[hour] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------- ~5.16 10:06:44 4320 >19.8 >19.6 >19.0 ------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22345 SUBJECT: GRB 180115A: NOT detection of optical counterpart DATE: 18/01/15 22:47:53 GMT FROM: Zach Cano at U of Iceland Z. Cano (HETH/IAA-CSIC), K. E. Heintz (Univ. Iceland & DARK/NBI), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), I. Marquez & S. Cazzoli (IAA-CSIC) report on behalf of a larger collaboration: We observed the field of GRB 180115A (Cannizzo et al.; GCN Circ. 22335) with the 2.5-m Nordic Optical Telescope equipped with ALFOSC, starting at 19:40:26 UT on 15 January 2017. We obtained 3x300 s in the r-band. In our co-added image a faint, new object is detected in the enhanced XRT error circle (Goad et al.; GCN Circ. 22337), with an apparent magnitude of r = 21.3 +- 0.1, at a mean post-explosion epoch of +15.53 hours. The calibration was performed using local Pan-STARRS standards in the GRB field. This apparent magnitude is not corrected for foreground extinction. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22346 SUBJECT: GRB 180115A: Redshift from OSIRIS/GTC DATE: 18/01/15 22:57:40 GMT FROM: Antonio de Ugarte Postigo at IAA-CSIC A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), Z. Cano, L. Izzo, C.C. Thoene, D.A. Kann (HETH/IAA-CSIC), N. Castro-Rodriguez (Grantecan, IAC, ULL), D. Perez Valladares (Grantecan) report on behalf of a larger collaboration: We observed the afterglow of GRB 180115A (Cannizzo et al. GCN 22335, Cano et al. GCN 22345) with OSIRIS at the 10.4m GTC telescope. The observation consisted of 3x900s exposure with grism R1000B, covering the range between 3700 and 7800 Angstrom and was performed under bad seeing conditions. The observation started at 20:32 UT (16.28 hr after the burst), and the acquisition image shows the afterglow at r=21.2+/-0.2. The spectrum shows a weak continuum over all the spectral range. The low signal to noise ratio of the spectrum only allows us to detect a single broad spectral feature that we identify as Lyman alpha at a redshift of 2.487. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22348 SUBJECT: GRB 180115A: Swift-BAT refined analysis DATE: 18/01/16 02:02:07 GMT FROM: Amy Lien at GSFC S. D. Barthelmy (GSFC), J. K. Cannizzo (NASA/UMBC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), 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+446 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180115A (trigger #805318) (Cannizzo et al., GCN Circ. 22335). The BAT ground-calculated position is RA, Dec = 12.040, -15.632 deg which is RA(J2000) = 00h 48m 09.6s Dec(J2000) = -15d 37' 55.0" with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 57%. The mask-weighted light curve shows a multi-peaked structure that starts at ~ T+25 s and ends at ~T+70 s. The main peak occurs at ~T+66 s. T90 (15-350 keV) is 40.9 +- 3.0 sec (estimated error including systematics). The time-averaged spectrum from T+26.49 to T+70.28 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.66 +- 0.22. The fluence in the 15-150 keV band is 7.6 +- 1.1 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+65.96 sec in the 15-150 keV band is 0.6 +- 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/805318/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22357 SUBJECT: GRB 180115A: Swift/UVOT Detection DATE: 18/01/16 20:26:27 GMT FROM: Frank Marshall at Swift/UVOT F. E. Marshall (NASA/GSFC) and J. K. Cannizzo (NASA/UMBC) report on behalf of the Swift/UVOT team: Additional observations of the optical afterglow of GRB 180115A discovered with Swift/UVOT (Cannizzo et al., GCN Circ. 22335) reveal an initially brightening and then fading source. The source is not detected in any of the UV filters, consistent with the redshift of 2.487 reported by de Ugarte Postigo et al. (GCN Circ. 22346). The preliminary UVOT position is: RA (J2000) = 00:48:09.27 = 12.03862 (deg.) Dec (J2000) = -15:37:49.9 = -15.63054 (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 140 290 147 17.61 +/- 0.04 white 753 773 20 16.95 +/- 0.07 white 5663 5863 197 19.18 +/- 0.08 v 628 648 20 16.50 +/- 0.16 b 554 574 20 16.93 +/- 0.11 u 299 548 246 16.32 +/- 0.04 w1 1109 13068 1165 >20.7 m2 4743 12296 1279 >21.8 w2 5769 7329 318 >20.2 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: 22362 SUBJECT: GRB 180115A: SEDM Observations DATE: 18/01/18 20:21:52 GMT FROM: Virginia Cunningham at U of MD V. Cunningham, J. D. Neill, S. B. Cenko, and R. Walters report on behalf of the SEDM team: We obtained a spectrum of the optical afterglow of GRB181105A (Cannizzo et al., GCN 22335; Cano et al., GCN 22345; de Ugarte Postigo et al., GCN 22346; Marshall et al., GCN 22357) with the Spectral Energy Distribution Machine (SEDM) on the 60 inch telescope at Palomar Observatory. The SEDM is a low resolution (R ~ 100) integral field unit spectrometer with a multi-band (ugri) “rainbow” camera imager (see Blagorodnova et al., 2017, astro-ph/1710.02917). Observations began at 4:30 UTC on January 15 (14 minutes after the Swift BAT trigger) and covered the wavelength range from 3800-9200 A with an exposure time of 2700 s. Continuum emission is clearly seen at wavelengths redder than 4500 A and is well fit by a relatively steep power-law spectrum with index alpha = 1.93 (f_nu ~ nu^-alpha). No obvious emission or absorption features are clearly detected in the spectrum; due to the low SNR at wavelengths shorter than 4500 A we cannot confirm the detection of Ly-alpha at z = 2.487 reported by de Ugarte Postigo et al. (GCN 22346). [GCN OPS NOTE(07sep19): Per author's request, in the last paragraph the "alpha = 1.93" was changed to "alpha = 0.93".]