Gamma-ray Burst 150627A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #17971
  M. Arimoto (Tokyo Tech), J.E. McEnery (NASA/GSFC), F. Longo (Trieste) and M. Axelsson (KTH Stockholm) report on behalf of the Fermi-LAT team:
  At 04:23:23.68 UT on June 27, 2015, Fermi-LAT detected high-energy emission from GRB 150627A, which was also detected by Fermi-GBM (trigger 457071806/ 150627183). The best LAT on-ground location is found to be
  RA, Dec = 117.49, -51.56 (J2000)
  with an error radius of 0.05 deg (90 per cent containment, statistical error only). This was 75 deg from the LAT boresight at the time of the trigger and triggered an autonomous repoint of the spacecraft.
  The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance. The highest-energy photon is a 8.1 GeV event which is observed 259 s after the GBM trigger.
  A Swift ToO has been requested for this burst.
  The Fermi-LAT point of contact for this burst is Makoto Arimoto (arimoto@hp.phys.titech.ac.jp)
  The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
• GCN Circular #17972
  P. A. Evans (U. Leicester) reports on behalf of the Swift team:
  Swift has initiated a ToO observation of the Fermi/LAT GRB 150627A. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/ToO_GRBs/00020539
  Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Fermi/LAT event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration.
  Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
  This circular is an official product of the Swift-XRT team.
• GCN Circular #17975
  H.-F. Yu (MPE), E. Burns, V. Connaughton, A. Goldstein (UAH), and M. Gibby (Jacobs) report on behalf of the Fermi GBM Team:
  "At 04:23:23.68 UT on 27 June 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150627A (trigger 457071806 / 150627183), which was also detected by the Fermi LAT (Arimoto et al., GCN 17971). The GBM on-ground location is consistent with the LAT position.
  The GBM trigger resulted in an Autonomous Repoint Request (ARR) that was accepted and the spacecraft slewed to the GBM in-flight location. At the GBM trigger time, the angle of the LAT localization to the LAT boresight is 75 deg.
  The GBM light curve consists of multiple pulses with a duration (T90) of about 65 s (50-300 keV). The time-averaged spectrum from T0-3.072 s to T0+92.161 s is best fit by a Band function with Epeak = 233 +/- 5 keV, alpha = -1.04 +/- 0.01, and beta = -2.18 +/- 0.02.
  The event fluence (10-1000 keV) in this time interval is (1.90 +/- 0.01)E-4 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+59.521 s in the 10-1000 keV band is 65.2 +/- 0.6 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
• GCN Circular #17976
  B.P. Gompertz (U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), L.M. McCauley (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:
  Swift-XRT has performed follow-up observations of the Fermi/LAT-detected burst GRB 150627A (Arimoto et al. GCN Circ. 17971), collecting 4.9 ks of Photon Counting (PC) mode data between T0+33.6 ks and T0+51.0 ks.
  An uncatalogued X-ray source is detected inside or close to the Fermi/LAT error region and is above the RASS limit, and is therefore likely the GRB afterglow. The position of this source is RA, Dec=117.4706, -51.4900 which is equivalent to:

  RA (J2000): 07:49:52.94
  Dec(J2000): -51:29:23.9
  

  with an uncertainty of 3.5 arcsec (radius, 90% confidence). This position is 4.3 arcmin from the Fermi/LAT position.
  The light curve can be modelled with a power-law decay with a decay index of alpha=2.2 (+/-0.3).
  A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.99 (+/-0.13). The best-fitting absorption column is 3.5 (+/-0.6) x 10^21 cm^-2, in excess of the Galactic value of 2.6 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (5.8 x 10^-11) erg cm^-2 count^-1.
  A summary of the PC-mode spectrum is thus:

  Total column:	     3.5 (+/-0.6) x 10^21 cm^-2
  Galactic foreground: 2.6 x 10^21 cm^-2
  Excess significance: 2.8 sigma
  Photon index:	     1.99 (+/-0.13)
  

  If the light curve continues to decay with a power-law decay index of 2.2, the count rate at T+24 hours will be 0.066 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.5 x 10^-12 (3.8 x 10^-12) erg cm^-2 s^-1.
  The results of the XRT-team automatic analysis of the likely afterglow are at http://www.swift.ac.uk/ToO_GRBs/00020539/index_1.php. The results of the full analysis of the XRT observations are available at http://www.swift.ac.uk/ToO_GRBs/00020539.
• GCN Circular #17977
  Paul Kuin (MSSL-UCL), Marissa McCauley (PSU) and Daniele Malesani (DARK/NBI) report on behalf of the Swift/UVOT team:
  The Swift/UVOT began settled observations of the field of the Fermi GRB 150627A 33622 s after the LAT trigger (Arimoto et al., GCN Circ. 17971; Yu et al., GCN Circ. 17975).
  An optical object consistent with the XRT position (Gompertz et al., GCN Circ. 17976) is detected at RA, Dec = 117.47108, -51.489417 deg (J2000), which is equivalent to:

  RA (J2000):  07:49:53.06
  Dec(J2000): -51:29:21.9
  

  with an uncertainty of 1".
  Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are:

  Filter           T_start(s)   T_stop(s)       Exp(s)      Mag
  
  white         33963          34289         335     19.11+/-0.10
  white         39860          40112         248     19.55+/-0.17
  white         45659          45863         204     19.28+/-0.14
  v             34304          34601         298     19.02+/-0.32
  v             40117          40346         225     18.98+/-0.36
  u             33622          38243         577     18.90+/-0.10
  u             43668          45654         966     19.00+/-0.11
  

  The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.32 in the direction of the burst (Schlegel et al. 1998).
  While no optical variability can be securely inferred from the UVOT photometry, the source is not visible in the DSS survey, and brighter than its limit, which suggests it to be the optical afterglow of GRB 150627A.
• GCN Circular #17978
  V. Lipunov, E. Gorbovskoy, N.Tyurina, V.Kornilov, P.Balanutsa,A.Kuznetsov,D.Kuvshinov, Lomonosov Moscow State University, Sternberg Astronomical Institute
  D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory
  Rafael Rebolo, Miquel Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias
  A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory
  K.Ivanov, O.Gres, N.M.Budnev, S.Yazev, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University
  V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A.Gabovich Blagoveschensk Educational State University, Blagoveschensk
  V.Krushinski, I.Zalozhnih Ural Federal University, 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 GRB150627.18 10133 sec after notice time and 55479 sec after trigger time at 2015-06-27 19:48:02 16:32:07 UT. On our first (180s exposure) set we found optical transient within LAT error-box (ra=07 49 57 dec=-51 33 34 r=0.500000, Arimoto et al., GCN 17791) brighter then 16.87.
  07h 49m 53.05s , -51d 29m 21s.4 error =+-1.0 m ~ 19.0
  This postion 2 arcsec close X-ray position (Gompertz et al., 17976) The 5-sigma upper limit has been about 16.87mag The message may be cited.
• GCN Circular #17979
  V. Lipunov (Lomonosov MSU)
  I am sorry for mistake. The correct time of the first exposition is 2015-06-27 16:32:07 (43664 s after trigger). I am out from good internet now. So, I did no see UVOT OT detection Paul Kuin et al.,GCN 17977 .
  The message may be cited.
• GCN Circular #17982
  S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report:
  The long-duration, bright GRB 150627A (Fermi-LAT detection: Arimoto, et al., GCN Circ. 17971; Fermi-GBM detection: Yu, GCN Circ. 17975) triggered Konus-Wind at T0=15806.292 s UT (04:23:26.292).
  The burst light curve shows a bright multi-peaked structure from ~T0-6 s to ~T0+80 s followed by a weak tail, which is traceable out to ~T0 + 150 s. The emission is seen up to ~15 MeV.
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB150627_T15806/
  As observed by Konus-Wind, the burst had a fluence of 2.34(-0.11,+0.12)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+12.240 s, of 2.02(-0.27,+0.27)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
  The time-averaged spectrum of the burst (measured from T0 to T0+81.408 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.98(-0.04,+0.05), the high energy photon index beta = -2.25(-0.08,+0.07), the peak energy 217(-13,+14) keV (chi2 = 125/96 dof)
  The spectrum near the maximum count rate (measured from T0+9.728 to T0+12.800 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.55(-0.07,+0.08), the high energy photon index beta = -2.52(-0.29,+0.18), the peak energy 412(-38,+40) keV (chi2 = 114/94 dof)
  All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.