Gamma-ray Burst 091111

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #10159
  D. Gotz (CEA-Saclay), E.Bozzo (ISDC, Versoix), S.Mereghetti, A.Paizis (IASF-Milano), M. Beck, (ISDC, Versoix), C. Ferrigno (ISDC, Versoix/ IAAT, Tuebingen) and J.Borkowski (CAMK, Torun) on behalf of the IBAS Localization Team report:
  a long faint and soft gamma-ray burst has been detected by the INTEGRAL Burst Alert System in IBIS/ISGRI data on November 11 2009. Due to its faintness no automatic alert has been issued and the GRB has been identified through the routine off-line analysis of the low significance triggers. The GRB starts at 15:21:59 U.T. and lasts for about 100 s.
  The GRB coordinates (J2000) are
  R.A. : 137.8133 [degrees] , Dec.: -45.9093 [degrees]
  with a 90% c.l. radius unercainty of 2.5 arcmin.
  Even if no known X-ray source is present in the IBAS error circle, we note that the low galactic latitude of the object and its soft X-ray spectrum may indicate also a Galactic transient origin. The light curve of the GRB will be posted at http://ibas.iasf-milano.inaf.it/IBAS_Results.html
  This message can be cited.
• GCN Circular #10160
  J. Gorosabel (IAA-CSIC), A. de Ugarte Postigo (INAF-OAB), A.J. Castro-Tirado, M. Jelinek (IAA-CSIC), P. Kubanek (IPL UV, IAA-CSIC), R. Cunniffe, S. Guziy (IAA-CSIC), P. Yock (Auckland Univ.), W.H. Allen (Vintage Lane Obs.), I. Bond (Massey Univ.), G. Christie (Stardome Obs.), report on behalf of a larger collaboration, report:
  "We have observed the field of the INTEGRAL GRB 091111 (Gotz et al. GCNC 10159) using the 0.6m Yock-Allen robotic telescope (BOOTES-3) located in Bleinheim, New Zealand. The observations were carried out between Nov. 12.45208 UT and 12.47379 UT, with a total exposure time of 88 min (starting 19.5 h after the burst). Visual comparison with the DSS does not show any new source in our combined unfiltered image of the INTEGRAL error box down a limiting magnitude (3 sigma) of R~19.6.
  Further observations are ongoing."
• GCN Circular #10161
  A. de Ugarte Postigo (INAF-OAB), J. Gorosabel, A.J. Castro-Tirado, M. Jelinek (IAA-CSIC), P. Kubanek (IPL UV, IAA-CSIC) and W.H. Allen (Vintage Lane Obs.), on behalf of a larger collaboration, report:
  "During regular monitoring, the all-sky camera located at BOOTES-3 observatory in Blenheim, New Zealand observed the field of the INTEGRAL GRB 091111 (Gotz et al. GCN 10159) before during and after the burst onset. We have examined the images obtained at the time of the GRB and we do not detect any new source within the INTEGRAL error box. In the following table we give time ranges and 3-sigma limiting magnitudes of the observations that overlap with the gamma-ray emission.

  T-T0(start-->end)  Lim
  =================
  -31s --> +5s           9.3
  +24s --> +60s        9.3
  +79 --> +115s        9.3
  

  This GCNC can be quoted."
• GCN Circular #10167
  V. Mangano, B. Sbarufatti (INAF-IASF PA), H. A. Krimm (CRESST/GSFC/USRA) and D. M. Palmer (LANL) report on behalf of the Swift-XRT team:
  The INTEGRAL burst GRB091111 (Gotz et al. GCN Circ. 10159) has been observed by Swift on 2009 11 12 with a 5 ks ToO started at 19:00 UT (trigger 020120). We have analysed 5.4 ks of XRT data in PC mode, from 100361 s to 115.3 ks after the INTEGRAL trigger.
  An X-ray source is detected at RA, Dec 137.82427, -45.92541 which is equivalent to:

     RA(J2000)  = 09h 11m 17.82s
     Dec(J2000) = -45d 55' 31.5"
  

  with an uncertainty of 5.1 arcseconds (radius, 90% containment).
  The light curve is probably decaying but more data are needed to estimate the decay slope.
  A spectrum formed from the PC mode data (30 counts within a circular region of 15 pixel radius) can be fitted with an absorbed power-law with a photon spectral index of 2.5 (+5, -3.4) The best-fitting absorption column is < 5 x 10^22 cm-2, consistent with the Galactic value of 6.2 x 10^21 cm-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 7.0 x 10^-11 (2.7 x 10^-10) erg cm^-2 count^-1.
  The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020120.
  At the time of GRB 091111, the Swift/BAT was active, sensitive and pointing such that the burst was in the BAT field of view with 25% mask coding. There is no count rate increase detected in any of the four BAT energy bands
  This circular is an official product of the Swift-XRT team.