- GCN Circular #5407
K. Hurley and T. Cline, on behalf of the Ulysses, Mars Odyssey,
and Konus GRB teams,
I. Mitrofanov, A. Kozyrev, M. Litvak, A. Sanin, V. Tret'yakov and A.
Parshukov, on behalf of the HEND-Odyssey GRB team,
W. Boynton, C. Fellows, K. Harshman, C. Shinohara and R. Starr, on
behalf of the GRS-Odyssey GRB team,
S. Golenetskii, E. Mazets, V. Pal'shin, and D. Frederiks on behalf of
the Konus-Wind teams,
D. M. Smith, R. P. Lin, J. McTiernan, R. Schwartz, C. Wigger, W.
Hajdas, and A. Zehnder, on behalf of the RHESSI GRB team, and
A. von Kienlin, G. Lichti, and A. Rau, on behalf of the
INTEGRAL SPI-ACS GRB team,
report:
Ulysses, Mars Odyssey, Konus, RHESSI, and INTEGRAL (SPI-ACS) observed
this very intense, 8 s long burst at 52035 s. Spectral information
will be given in a forthcoming GCN Circular. We have triangulated
it to an ~ 46 sq. arcmin. error box (3 sigma), whose coordinates are
RA(2000) DEC(2000)
18 h 10 m 01.78 s 58 o 08 ' 47.67 " (CENTER)
18 h 09 m 36.85 s 58 o 00 ' 55.18 " (CORNER)
18 h 09 m 47.45 s 57 o 57 ' 22.44 " (CORNER)
18 h 10 m 16.89 s 58 o 20 ' 22.15 " (CORNER)
18 h 10 m 27.16 s 58 o 16 ' 42.85 " (CORNER)
This error box may be improved.
- GCN Circular #5413
P. Schady (UCL-MSSL) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began observing the field of the GRB060805B on Aug. 7th at
01:34:52 UT. No optical afterglow candidate has been found in the coadded
images of any of the UV/optical lenticular filters within the IPN error
box reported by Hurley et al. (GCN 5407).
The 3-sigma limiting magnitudes for the coadded images for the
6 filters are listed below:
Filter Tstart (UT) Exposure(s) 3sig upper limits
V 02:02:23 1397 20.56
B 01:45:13 1397 21.61
U 01:41:44 1397 21.26
UVW1 01:34:52 2802 20.77
UVM2 02:05:50 3619 21.27
UVW2 01:48:42 2402 21.27
These upper limits have not been corrected for the estimated Galactic reddening
of E(B-V) = 0.037 mag (Schlegel et al. 1998).
- GCN Circular #5414
N. Butler (UC Berkeley) reports:
We report the results of a spectral/spatial/temporal analysis of the
Swift target-of-opportunity observation of the X-ray afterglow to
GRB060805B (GCN 5407). We detect a bright and fading X-ray source <~0.7
arcmin from the center of the IPN error region. Using 130 cts (0.3-10 keV)
from a total exposure of 16.7 ksec for the time interval 126-164 ksec after
the IPN trigger, the count rate fades as t^-alpha, with alpha=-2.4+/-1.1.
The spectrum is fit by an absorbed powerlaw, with column density
N_H = (1.3+/-1.1) 10^21 cm^-2, consistent with the Galactic value in the
source direction. Also, we find photon index Gamma=2.1+/-0.4 and
unabsorbed flux (4.4+/-1.1) 10^(-13) erg cm^-2 s^-1.
We determine the following position for the transient, with respect to
the DSS positions of 23 optical sources and the XRT positions of 7 X-ray
sources and including an estimate of the systematic error:
RA, Dec: 18 10 05.41 +58 09 18.1 ; +/- 2.6" (J2000, 90% Conf.)
We note that the X-ray source is near but not spatially consistent with
a R~18.5 mag source in the DSS at RA, Dec: 18 10 5.64, +58 09 19.4.
- GCN Circular #5418
E. Bellm, M. Bandstra, S. Boggs, D. M. Smith, R. P. Lin, J. McTiernan, R.
Schwartz, C. Wigger, W. Hajdas, A. Zehnder, and K. Hurley, report:
The preliminary fit to the time-integrated RHESSI spectrum of
GRB060805B (Hurley et al., GCN 5407; Butler, GCN 5414) between 30 keV
and 10 MeV is a Band function with
alpha = -0.66 +0.12/-0.10
beta = -2.52 +0.16/-0.22
E0 = 240. +45/-40. keV
Epeak = 320. +/-20. keV
The 30 keV-10 MeV fluence is 1.13 +/- 0.046 E-4 erg/cm^2.
- GCN Circular #5428
O. Godet, K. L. Page, M. R. Goad, E. Rol, P.T. O'Brien (U Leicester),
P. Schady (UCL-MSSL), and K. Hurley (UCB) report on behalf of the
Swift-XRT team:
GRB 060805B was detected by IPN (GNC Circ 5407). XRT started to observe
35.1 hours after the IPN trigger for a present 25ks of data. The full
IPN error box was within the XRT field of view. Using the ftool
xrtcentroid, the first 25ks of the XRT data revealed an X-ray source in
the IPN error box at (J2000):
RA = 18 10 05.56
Dec = +58 09 16.3
with an uncertainty of 3.9 arcseconds (90% containment). This position
consistent with that given by Butler 2006 (GCN Circ. 5414) does not
correspond to any catalogued X-ray sources. We note that the X-ray
position is consistent with the position of two optical sources S1 and
S2 in the USNO-B1.0 (Monet et al. 2003) and APM-North (McMahon et al.
2000) catalogues, repectively. The source S1 (RA(J2000) = 18 10 05.56
and Dec = +58 09 19.3) is 2.9 arcseconds away from the XRT position. The
source S2 (RA(J2000) = 18 10 05.60 and Dec = +58 09 19.1) is 2.8
arcseconds away from the XRT position. The positions of the optical
sources are consistent with those reported by Butler 2006 (GCN Circ.
5414).
The spectrum from the first 19ks of the PC data can be well fitted by an
absorbed power-law with Gamma = 1.78 +0.36/-0.33. No clear evidence of
absorption in excess over the Galactic absorption (nH(Gal) = 3.7e20
cm^-2 from Dickey & Lockman 1990) is seen in the data. The unabsorbed
flux in the 0.5-10 keV energy band is 3.9 +1.8/-1.1e-13 erg cm^-2 s^-1.
These results are consistent with those given by Butler (2006; GCN Circ
5414).
Using the initial 19ks of data did not allow us to determine if the
X-source was really fading. Indeed, fitting the light-curve with a
constant (C) gives a value of chi^2/dof=6.5/7 with C = 0.0087+/-0.0012,
while using a power-law gives a value of chi^2/dof=4.0/6 with alpha =
1.62 +1.70/-1.56
(http://www.swift.ac.uk/grb060805b.shtmla)
Using a power-law allows an improvement of delta chi^2 = 2.5 for 1 dof i.e.
less than 90% confidence.
Adding 6 ks of data obtained at later time allows us to confirm that the
X-ray source is actually fading with a decay slope of alpha = 1.20
+0.72/-0.53
(http://www.swift.ac.uk/grb060805b.shtml) and is likely to
be the afterglow of GRB 060805B.
We would like to encourage ground observations in order to determine the
redshift of this burst.
This circular is an official product of the Swift-XRT team.
- GCN Circular #5429
D. Mart=EDnez and A. J. Castro-Tirado (IAA-CSIC Granada), on behalf
of a larger collaboration,
report:
"Following the detection by the IPN of the bright GRB 060805B
(Hurley et al. GCNC 5407), we have obtained I-band frames with
the 1.5m OSN telescope in Spain starting on Aug 8.04 UT (i.e.
58.3 hr post-burst). Six exposures (300s each) in the I-band
filter were taken under non optimum technical conditions.
Within the Swift/XRT X-ray afterglow error box (Butler GCNC 5414,
Godet et al. GCNC 5428), we only detect a single optical source
which is also present in the DSS2 with about the same brightness.
The limiting magnitude of our combined I-band image is I = 20.5".
- GCN Circular #5437
A. Pelangeon & J-L. Atteia (LATT-OMP) report:
We have used the spectral parameters of GRB 060805B
provided by Bellm et al. (GCNC 5418)
to compute the spectral pseudo-redshift** of this burst
localized by IPN (Hurley et al., GCNC 5407).
We find a pseudo-redshift pz= 1.3 +/- 0.2 (90% error).
** cf. http://www.ast.obs-mip.fr/grb/pz
- GCN Circular #5454
M. Andreev (Institute of Astronomy), A. Pozanenko (IKI) on behalf of larger
GRB follow up collaboration report:
We observed an error box of the GRB060805B (Hurley et al. GCN 5407) with
the Z-600 telescope of peak Terskol Observatory on Aug. 7 between (UT)
22:37 - 22:52 in R-band. Within the Swift/XRT error box (Butler GCN 5414,
Godet et al. GCN 5428) in a combined image (15x60 s) we clearly detect only
the source (USNO-B1.0 1481-0304497) mentioned earlier (Butler GCN 5414,
Godet et al. GCN 5428).
The limiting magnitude of the combined image is R~19.0.
The message may be cited.
[GCN OPS NOTE(15aug06): This Circular was delayed by ~1 hr due to problems
at the GCN end.]
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