GRB 080602

G. Sato (GSFC/ISAS), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), J. Cummings (GSFC/UMBC), E. Fenimore (LANL),
N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
K. McLean (GSFC/UMD), D. Palmer (LANL), T. Sakamoto (GSFC/UMBC),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-296 to T+302 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 080602 (trigger #312958)
(Beardmore, et al., GCN Circ. 7781
Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 19.177, -9.239 deg, which is 
   RA(J2000)  =  01h 16m 42.6s 
   Dec(J2000) = -09d 14' 19.8" 
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 19%.
 
The mask-weighted light curve shows 4 or 5 peaks, the first starting at ~T-25 sec,
the second at ~T-15 sec, the 3rd at ~T-5 sec, peaking at ~T+1 sec and 
ending at ~T+15 sec; the 4th starts at ~T+55 sec and ends at ~T+65 sec.
T90 (15-350 keV) is 74 +- 7 sec (estimated error including systematics).
 
The time-averaged spectrum from T-11.5 to T+69.3 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.43 +- 0.13.  The fluence in the 15-150 keV band is 3.2 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+59.60 sec in the 15-150 keV band
is 2.9 +- 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/312958/BA/

A.P. Beardmore, K.L. Page and P.A. Evans (U. Leicester) report on behalf 
of the Swift-XRT team:

The Swift-XRT observed GRB 080602 (trigger 312958, Beardmore et
al. GCN 7781
Loading...
 
 ) for one orbit which consisted of 71 s of Windowed
Timing mode data starting 118 s after the trigger and 1.23 ks  of
Photon Counting mode data, 193 s after the trigger.

Using 930 s of overlapping XRT Photon Counting mode and UVOT data, 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 = 19.17574, -9.23207 which is equivalent to:

RA (J2000): 01 16 42.18
Dec (J2000): -09 13 55.4

with an uncertainty of 1.7 arcsec (radius, 90% confidence). The position 
is 6.3 arcsec from the on-board position reported in GCN 7781
Loading...
 
  and 0
Loading...
 
 .4 
arcsec from the initial refined XRT position reported in GCN 7782
Loading...
 
 .

At first, the X-ray light curve shows signs of a steep decay with a slope 
of 4.7 +2.1/-0.9, breaking to a shallower decay of 0.21 +/- 0.16 at 
a time of 145 +11/-6 s after the trigger. This is followed by a further 
steepening  to a slope of 0.76 +0.41/-0.23 at a time of 561 +276/-201 s.

A spectrum of the Windowed Timing data can be well fit by an absorbed
power-law, with a photon index Gamma = 1.63 +/- 0.21 and a column
density Nh = (1.0 +/- 0.5) e21 cm^-2, compared with the Galactic
column density in this direction of 3.5e20 cm^-2. The observed
(unabsorbed) 0.3-10 keV flux is 3.13e-10 (3.61e-10) erg cm^-2 s^-1.

The Photon Counting mode spectrum is also well fit by an absorbed
powerlaw, with Nh = (2.1 +/- 0.4) e21 cm^-2 and Gamma = 2.12 +/- 0.15.
The observed (unabsorbed) 0.3-10 keV flux is 1.66 e-10 (2.59e-10)
erg cm^-2 s^-1.  The observed count to flux conversion factor for this
data is 3.5e-11 erg cm^-2 count^-1.

Due to the limited XRT data available, no count rate prediction at T+1 day
has been made. No further observations with Swift are planned.

This circular is an official product of the Swift-XRT team.

S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks,
and T. Cline on behalf of the Konus-Wind team report:

The second, most intense pulse of the GRB 080602 (Swift-BAT trigger 
#312958: Beardmore et al., GCN 7781
Loading...
 
 ) triggered Konus-Wind
at T0=5486.229 s UT (01:31:26.229).

As observed by Konus-Wind the burst
had a fluence of 7.92(-1.45, +1.47)x10^-6 erg/cm2,
and a 256-ms peak flux measured from T0+1.280 s
of (1.92 +/- 0.58)x10^-6 erg/cm2/s
(both in the 20 keV - 1 MeV energy range).

The spectrum of the most intense part
(from T0 to T0+8.448 s) is well fitted (in the 20 keV-1 MeV range)
by a simple power law with the photon index of 1.48(-0.17, +0.18) (chi2 
= 39.7/53 dof). We note that because of the derived photon index is <2,
the fluence is very sensitive to the upper boundary of the energy range.
Fitting by a power law with exponential cutoff model:
dN/dE ~ (E^-alpha)*exp(-E*(2-alpha)/Ep)
yields alpha = 0.96(-0.76, +0.52),
and only a lower limit on the peak energy: Ep > 226 keV
(chi2 = 36.6/52 dof).

All the quoted errors are at the 90% confidence level.

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB080602_T05486/

Daniele Malesani (DARK/NBI), Pierre-Olivier Quirion (Univ. AArhus), and
Johan Peter Uldall Fynbo (DARK/NBI), Páll Jakobsson (Univ. Hertfordshire)
report on behalf of a larger collaboration:

We observed the field of GRB 080602 (Beardmore et al., GCN 7781
Loading...
 
 ) with the
NOT telescope. Observations were carried out in the R band at high airmass
(~6) and close to twilight. Mean time was June 2.203 UT, 3.4 hr after the
trigger. Inside the refined XRT error circle (Beardmore et al., GCN 7782
Loading...
 
 ),
we do not detect any source down to a limiting magnitude R=22.3.
Observations will be attempted with the VLT on Cerro Paranal, but due to
weather the outlook for data is bad. We encourage observations from other
sites.

A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 16 s of overlapping XRT Photon Counting mode and UVOT
data for GRB 080602, 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 = 19.17563, -9.23212 which is equivalent
to:

RA (J2000): 01h 16m 42.15s
Dec (J2000): -09d 13' 55.6"

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
http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an
extension of this method.

This circular was automatically generated, and is an official product of the
Swift-XRT team.

A. P. Beardmore (U Leicester), S. D. Barthelmy (GSFC),
J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC),
S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU),
J. A. Kennea (PSU), C. B. Markwardt (CRESST/GSFC/UMD),
F. E. Marshall (NASA/GSFC), K. M. McLean (GSFC/UMD),
K. L. Page (U Leicester), D. M. Palmer (LANL) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:

At 01:30:28 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080602 (trigger=312958).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 19.173, -9.251 which is 
   RA(J2000) = 01h 16m 41s
   Dec(J2000) = -09d 15' 02"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed two well-separated
peaks with a total duration of about 70 sec.  The peak count rate
was ~3000 counts/sec (15-350 keV), at ~60 sec after the trigger. 

The XRT began observing the field at 01:32:19.7 UT, 111.6 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 19.1766, -9.2336 which is equivalent to:
   RA(J2000)  = 01h 16m 42.3s
   Dec(J2000) = -09d 14' 00.9"
with an uncertainty of 5.8 arcseconds (radius, 90% containment). This
location is 63 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to assess possible
redshift constraints using X-ray spectroscopy and the nH-z relation
from Grupe et al. (2007). 


UVOT took a finding chart exposure of nominal 100 seconds with the White
(160-650 nm) filter starting 123 seconds after the BAT trigger. No afterglow
candidate has been found in the initial data products. Image catalog data are
not available at this time. The 8'x8' region for the list of sources generated
on-board covers 100% of the XRT error circle. The list of sources is typically
complete to about 18 mag. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.03. 




Burst Advocate for this burst is A. P. Beardmore (apb AT star.le.ac.uk). 
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.)