//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17515 SUBJECT: GRB 150301B: Swift detection of a burst with an optical afterglow DATE: 15/03/01 19:50:01 GMT FROM: David Palmer at LANL A. Y. Lien (GSFC/UMBC), D. N. Burrows (PSU), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), M. De Pasquale (INAF-IASFPA), A. Maselli (INAF-IASFPA), K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 19:38:04 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 150301B (trigger=633180). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 89.157, -57.977 which is RA(J2000) = 05h 56m 38s Dec(J2000) = -57d 58' 37" 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 20 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 19:39:26.4 UT, 82.4 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 89.16636, -57.97051 which is equivalent to: RA(J2000) = 05h 56m 39.93s Dec(J2000) = -57d 58' 13.8" with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 29 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 6.16 x 10^20 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 85 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 05:56:39.86 = 89.16608 DEC(J2000) = -57:58:10.4 = -57.96956 with a 90%-confidence error radius of about 0.61 arc sec. This position is 31.9 arc sec. from the center of the BAT error circle. The estimated magnitude is 16.22 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.08. Burst Advocate for this burst is A. Y. Lien (amy.y.lien 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: 17518 SUBJECT: GRB 150301B: MASTER early OT detection DATE: 15/03/01 20:51:41 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory E. Gorbovskoy, V. Lipunov, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.V.Chazov, D.Kuvshinov, Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory V.Krushinsky, I.Zalozhnih, A. Popov Ural Federal University, Yekaterinburg, Kourovka Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) Claudio Mallamaci, Carlos Lopez and Federico Podest Observatorio Astronomico Felix Aguilar (OAFA) MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in SAAO was pointed to the GRB150301.82 (Lien et al, GCN 17515) 60 sec after notice time and 79 sec after trigger time at 2015-03-01 19:39:23 UT in two polarizations. On our first (10s exposure) set we found 1 optical transient within SWIFT error-box (ra=05 56 37 dec=-57 58 35 r=0.050000). T_start RA DEC Exp unfiltered s magnitude 2015-03-01 19:39:23 79.0 05h 56m 39.94s -57d 58m 10.0s 15.3 The error is about 0.5 arcsec. This position is coincidet with UVOT data. We detected OT before maximum brightness. The 5-sigma upper limit has been about 16.8 mag . The telegram is generated automatically. We have number of the images after maximum in two polarizations. The reduction is continuated. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17520 SUBJECT: GRB 150301B: Enhanced Swift-XRT position DATE: 15/03/01 22:44:01 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 386 s of XRT Photon Counting mode data and 1 UVOT images for GRB 150301B, 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 = 89.16660, -57.96950 which is equivalent to: RA (J2000): 05h 56m 39.98s Dec (J2000): -57d 58' 10.2" 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: 17522 SUBJECT: GRB 150301B: GROND afterglow observations DATE: 15/03/02 01:55:37 GMT FROM: Alexander Kann at TLS Tautenburg D. A. Kann (TLS Tautenburg), C. Delvaux and J. Greiner (both MPE Garching) report on behalf of the GROND team: We observed the field of GRB 150301B (Swift trigger 633180; Lien et al., GCN #17515) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). Observations started at 00:09 UT on 2015-03-02, 4.5 hrs after the GRB trigger. They were performed at an average seeing of 1".0 and at an average airmass of 1.1. We detect the optical afterglow candidate reported by Lien et al. (GCN #17515) and Buckley et al. (GCN #17518). Based on 7.7 min of total exposure time in g'r'i'z' and 8.0 min in JHK, centered 5 hrs after the GRB, we estimate the following preliminary magnitudes (all in AB system): g' = 21.7 +/- 0.2 mag, r' = 21.4 +/- 0.1 mag, i' = 21.2 +/- 0.1 mag, z' = 21.0 +/- 0.1 mag, J = 20.5 +/- 0.3 mag, H = 20.6 +/- 0.4 mag, and K > 17.9 mag. Given magnitudes are calibrated against GROND zeropoints (g'r'i'z') as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.08 mag in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17523 SUBJECT: GRB 150301B: X-shooter spectroscopy DATE: 15/03/02 02:07:10 GMT FROM: Antonio de Ugarte Postigo at IAA-CSIC A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), T. Kruehler (ESO), H. Flores (GEPI/Obs. de Paris), and J.P.U. Fynbo (DARK/NBI) report on behalf of a larger collaboration: We observed the afterglow of GRB 150301B (Lien et al. GCN 17515, Buckley et al. GCN 17518, Kann et al. GCN 17522) with X-shooter at the Very Large Telescope (Paranal Observatory, Chile). Observations started at 00:45 UT (5.12 hr after the burst), and consisted of 6x600 s exposures covering the spectral range between 3 000 and 18 000 Angstroms. In the acquisition image the afterglow is detected with R(Vega) = 21.0 mag, as compared to stars of the USNOB-1.0 catalogue. On a preliminary reduction we detect a weak continuum with absorption features of FeII, MgII and MgI at a common redshift of z = 1.5169, which we suggest as the redshift of the GRB. We acknowledge the excellent support provided by Paranal staff, and in particular Andrea Mehner, Tayyaba Zafar, and Marcelo Lopez. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17524 SUBJECT: GRB 150301B: Swift-BAT refined analysis DATE: 15/03/02 05:24:04 GMT FROM: Amy Lien at GSFC T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC), (i.e. the Swift-BAT team): Using the data set from T-60 to T+243 sec from the recent telemetry downlink, we report further analysis of BAT GRB 150301B (trigger #633180) (Lien, et al., GCN Circ. 17515). The BAT ground-calculated position is RA, Dec = 89.159, -57.969 deg which is RA(J2000) = 05h 56m 38.3s Dec(J2000) = -57d 58' 07.8" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 62%. The mask-weighted light curve shows a single-peaked structure that starts at ~ T0, peaks at ~ T+3 s, and ends at ~ T+16 s. T90 (15-350 keV) is 12.44 +- 1.49 sec (estimated error including systematics). The time-averaged spectrum from T-0.34 to T+15.62 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.46 +- 0.07. 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 3.0 +- 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/633180/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17525 SUBJECT: GRB 150301B: Fermi GBM detection DATE: 15/03/02 05:26:50 GMT FROM: Eric Burns at U of Alabama E. Burns (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 19:38:04.51 UT on 01 March 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150301B (trigger 446931487/150301818) which was also detected by the Swift/BAT (Lien et al. 2015, GCN 17515). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 39 degrees. The GBM light curve consists of one main peak with a duration (T90) of about 13 s (50-300 keV). The time-averaged spectrum from T0-2.560 s to T0+13.824 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.2 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 256 +/- 32 keV. A Band function fits the spectrum equally well with Epeak= 180 +/- 38 keV, alpha = -1.1 +/- 0.1 and beta = -2.0 +/- 0.2. The event fluence (10-1000 keV) in this time interval is (4.4 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2.560 s in the 10-1000 keV band is 4.5 +/- 0.2 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: 17530 SUBJECT: GRB 150301B: LCOGT-Sutherland observations DATE: 15/03/02 09:00:17 GMT FROM: Cristiano Guidorzi at Ferrara U,Italy C. Guidorzi (U. Ferrara), J. Japelj, A. Gomboc (U. Ljubljana), C.G. Mundell (U. Bath), on behalf of a large collaboration report: One of the Las Cumbres Observatory 1-m telescopes in Sutherland (South Africa) began observing Swift and Fermi GRB 150301B (Lien et al. GCN 17515; Burns et al. GCN 17525) on March 01 at 20:07:30 UT, i.e. ~29.4 minutes after the BAT trigger with the r', i', and g' filters. We detect the optical afterglow (Lien et al. GCN 17515; Buckley et al. GCN 7518; Kann et al. GCN 17522; de Ugarte Postigo et al. GCN 17523) with the following magnitudes: Mid time from Total Exp Filter Magnitude trigger (min) (s) ------------------------------------------------- 37.7 360 r' 18.85 +- 0.25 42.3 360 i' 18.5 +- 0.3 ------------------------------------------------- Values have been calibrated against nearby USNOB-1 stars (R2 and I). Compared with earlier (Buckley et el.) and later (Kann et al.) observations, our values suggest an overall power-law decay index ~1. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17531 SUBJECT: GRB 150301B: Swift/UVOT Observations DATE: 15/03/02 14:28:45 GMT FROM: Margaret Chester at PSU M. M. Chester (PSU) and A. Y. Lien (GSFC/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 150301B 86 s after the BAT trigger (Lien et al., GCN Circ. 17515). A fading source consistent with the XRT position (Evans et al. GCN Circ. 17520) and the optical transient reported by Buckley et al. (GCN Circ. 17518) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 05:56:39.89 = 89.16622 (deg.) Dec (J2000) = -57:58:10.4 = -57.96955 (deg.) with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits for the White finding chart and subsequent exposures 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_FC 86 236 147 16.2 +/- 0.1 white 3986 4121 133 >20.2 v 5833 6033 197 >19.7 b 3782 3982 197 >19.6 u 298 543 241 17.1 +/- 0.1 w1 6243 10068 579 >19.9 m2 6038 6237 197 >19.8 w2 5628 16054 963 >21.6 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.08 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17533 SUBJECT: GRB 150301B: Swift-XRT refined Analysis DATE: 15/03/02 19:50:04 GMT FROM: Phil Evans at U of Leicester A. Maselli (INAF-IASFPA), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), A. Amaral-Rogers (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB) and A.Y. Lien report on behalf of the Swift-XRT team: We have analysed 5.7 ks of XRT data for GRB 150301B (Lien et al. GCN Circ. 17515), from 67 s to 69.5 ks after the BAT trigger. The data comprise 67 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 Evans et al. (GCN Circ. 17520). The light curve can be modelled with a power-law decay with a decay index of alpha=1.11 (+0.05, -0.04). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.81 (+0.18, -0.10). The best-fitting absorption column is consistent with the Galactic value of 6.2 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (4.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Galactic foreground: 6.2 x 10^20 cm^-2 Intrinsic column: 6 (+/-14) x 10^20 cm^-2 at z=1.5169 Photon index: 1.81 (+0.18, -0.10) If the light curve continues to decay with a power-law decay index of 1.11, the count rate at T+24 hours will be 3.3 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x 10^-13 (1.4 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/00633180. This circular is an official product of the Swift-XRT team.