Gamma-ray Burst 111205A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN Circular #12626
K. Hurley, on behalf of the Mars Odyssey and MESSENGER GRB teams,
I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,
S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, and
A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, report:
The long-duration, intense GRB 111205A has been observed by INTEGRAL (SPI-ACS), Konus-Wind, and Mars Odyssey (HEND) so far, at about 47450 s UT (13:10:50). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:
```
  ----------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   134.486 (08h 57m 57s) -31.972 (-31d 58' 20")
  Corners:
   134.668 (08h 58m 40s) -32.260 (-32d 15' 37")
   134.190 (08h 56m 46s) -31.944 (-31d 56' 38")
   134.306 (08h 57m 13s) -31.682 (-31d 40' 57")
   134.782 (08h 59m 08s) -31.999 (-31d 59' 57")
  ---------------------------------------------
```
The error box area is 492 sq. arcmin, and its maximum dimension is 39 arcmin.
This box can be improved.
The time history and spectrum will be given in a forthcoming GCN Circular.
A Swift ToO observation has been requested.
GCN Circular #12627
S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report:
The long hard intense GRB 111205A (localized by IPN: Hurley et al., GCN=20 12626) triggered Konus-Wind at T0=3D47450.301 s UT (13:10:50.301)
The light curve starts with a hard bright ~20 s long pulse followed by a weaker tail of softer emission. A total duration of the burst is ~85 s. The emission is seen up to ~8 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB111205_T47450/
As observed by Konus-Wind the burst had a fluence of (1.7 =B1 0.1)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+1.024 s, of (2.2 =B1 0.25)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum of the burst (measured from T0 to T0+80.384=20 s) is best fitted in the 20 keV - 10 MeV range by a power law with exponential cutoff model, for which alpha =3D -0.82 (-0.04, +0.04), and Ep =3D 998 (-70, +77) keV, chi2 =3D 98.0/85 dof. Fitting by GRB (Band) model yields the same alpha and Ep, and only an upper limit on the high energy photon index: beta < -2.86 (chi2 =3D 97.2/84 dof).
The spectrum at the maximum count rate (measured from T0 to T0+4.352 s) is best fitted in the 20 keV - 10 MeV range by a power law with exponential cutoff model, for which alpha =3D -0.35 (-0.05, +0.05), and Ep =3D 1120 (-57, +60) keV, chi2 =3D 68.8/85 dof.
All the quoted results are preliminary. All the quoted errors are at the 90% confidence level.
GCN Circular #12630
C. A. Wolf (PSU) and E. A. Hoversten (PSU) report on behalf of the Swift team:
We have analysed 5.0 ks of XRT data for the IPN-detected burst: GRB 111205A (Hurley et al. GCN Circ. 12626), from 198.4 ks to 210.7 ks after the IPN trigger. The data are entirely in Photon Counting (PC) mode. The XRT field-of- view does not cover the entire IPN error region. However, an uncataloged X-ray source is detected within the observed XRT field which is potentially the afterglow of GRB 111205A. The refined XRT position is RA, Dec = 134.6793, -31.94327 which is equivalent to:
```
RA (J2000): 08 58 43.03
Dec(J2000): -31 56 35.8
```
with an uncertainty of 4.3 arcsec (radius, 90% confidence). This position is inside the IPN error box. We cannot determine at the present time whether the source is fading. A follow-up Swift observation is planned in several days to confirm fading of the source. The XRT position is outside of the UVOT field of view. However, archival DSS imaging reveals a faint optical source within the XRT error circle.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020189.
GCN Circular #12636
D. A. Kann, A. Rossi, A. Nicuesa Guelbenzu (TLS Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND team:
We observed the field of the possible X-ray afterglow (Wolf & Hoversten, GCN #12630) of the intense IPN GRB 111205A (Hurley et al., GCN #12626, Golenetskii et al., GCN #12627) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP, 120, 405) mounted at the 2.2 m ESO/MPI telescope at La Silla Observatory (Chile).
Observations were obtained at a mid-time of 07:35 UT on December 9, 2011, 4.87 days after the GRB trigger, under excellent conditions. They were performed at an average seeing of 0".7 in the optical bands and at an airmass of 1. The integration time was 1475 sec in g'r'i'z' and 1200 sec in JHK.
The DSS source mentioned by Wolf & Hoversten in the XRT error circle is detected and is revealed to be a double star separated by about 1".2, both components clearly resolved due to the excellent seeing. The r'-band magnitudes of the stars (calibrated against an SDSS standard field) are 16.33 (south-east, edge of error circle) and 16.85 (north-west, in error circle) with negligible errors.
We therefore posit that this source is not associated with GRB 111205A, and the X-ray source detected by XRT is not the X-ray afterglow of the GRB. We note that such a faint X-ray source, at 6E-3 cts/s, would be untypical for an X-ray afterglow of an intense GRB, even several days after the GRB.
GCN Circular #12699
E. A. Hoversten (PSU) and C. A. Wolf (PSU) report on behalf of the Swift team:
We have analyzed 8.3 ks of XRT data for the IPN detected burst GRB 111205A (Hurley et al. GCN Circ. 12626) from 828 to 853 ks after the burst. The data are entirely in Photon Counting (PC) mode. Previously an uncataloged X-ray source was detected by XRT 200 ks after the burst (Wolf & Hoversten GCN Circ. 12630) which was identified as the potential afterglow for GRB 111205A, but could not be confirmed as it was not possible to discern if the source was fading in a single observation. The follow-up observation reveals that the source is still detected, but has faded by a factor of 4, which corresponds to a decay index of 1.0 (+1.3, -0.6) which is consistent with a GRB late time afterglow. Thus we conclude that the X-ray source previously reported is the afterglow.
GCN Circular #12736
L. Elenin (KIAM), A. Volnova (SAI MSU), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of IPN of hard intense GRB 111205A (Hurley et al., GCN 12626; Golenetskii et al., GCN 12627) with 0.45-m telescope If ISON-NM observatory on Dec 8 (09:55:52 - 11:52:34 UT). We took several unfiltered images of 300 s exposure. All our images cover full IPN error box. On a stacked image we do not find any new objects within IPN error box in comparison with DSS. We detect DSS source mentioned by Wolf & Hoversten in the XRT error circle (Wolf & Hoversten, GCN 12630). However due to bad seeing we cannot resolve this source into separate sources of a double star (Kann et al., GCN 12636).
Photometry of the unresolved source based on several nearby USNO-B1.0 stars (R2 magnitudes) is the following:
```
t-t0             filter      Exp.     source             uplim (3 sigma)
(mid, days)             (s)

2.90513      none     21x300   15.40 +/- 0.05     19.8
```

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Jochen Greiner, last update: 28-Dec-2011 [Disclaimer]