GRB 080723A
GCN Circular 8004
Subject
GRB 080723A: Swift-XRT refined analysis
Date
2008-07-23T15:35:27Z (17 years ago)
From
Andy Beardmore at U Leicester <apb@star.le.ac.uk>
A.P. Beardmore (U. Leicester) and M. Stamatikos (NASA/ORAU)
report on behalf of the Swift-XRT team :
We have analysed the first two orbits of Swift-XRT data obtained
from GRB 080723A (trigger 317662; Stamatikos et al., GCN Circ. 8000).
The data were taken in photon counting mode and have an exposure of
2.83 ks, spanning 88 s to 7.44 ks after the trigger. The UVOT-enhanced
XRT position was given by Beardmore et al. in GCN Circ. 8001.
The light curve can be modelled by a doubly broken power-law, with
an inital decay of alpha1 = 1.77 +0.34 -0.25 which flattens to a shallow
decay of alpha2 = 0.05 +/- 0.24 at a time tbreak1 = 365 +68 -46 s. This is
followed by a further steepening to alpha3 = 1.39 +/- 0.75 at a time
tbreak2 = 3.4 +1.2 -1.8 ks.
The spectrum of the photon counting mode data from the first two orbits
can be fit with an absorbed power-law to give a photon index gamma =
2.39 +0.30 -0.28 and NH = (7.7 +2.5 -2.2)e21 cm^-2, in addition to the
Galactic column of 3.9e+21 cm^-2 in the direction of the GRB. The observed
0.3-10 keV flux is (1.14 +0.10 -0.22)e-11 erg cm^-2 s^-1, which corresponds
to an unabsorbed flux of 3.57e-11 erg cm^-2 s^-1.
If the light curve continues to decay at the same rate we estimate the count
rate will be 3.2e-2 count/s one day after the trigger, which corresponds to
an observed flux of 1.9e-13 erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.
GCN Circular 8012
Subject
GRB 080723A: Swift/UVOT Upper Limits
Date
2008-07-24T14:32:06Z (17 years ago)
From
Stephen Holland at USRA/NASA/GSFC/SSC <sholland@milkyway.gsfc.nasa.gov>
S. T. Holland (CRESST/GSFC/USRA) and M. Stamatikos (NASA/ORAU) report
on the behalf of the Swift UVOT team:
The Swift/UVOT observed the field of GRB 080723A starting 68 s
after the BAT trigger (Stamatikos et al. 2008, GCN Circ. 8000). We do
not find any source, in any of the UVOT observations, at the
UVOT-enhanced XRT position of the afterglow (Beardmore 2008, GCN
Circ. 8001). The 3-sigma upper limits for detecting a source at this
location in the co-added images are:
Filter T_start T_stop Exp(s) Mag (3-sigma upper limit)
-----------------------------------------------------------------
v 194 6260 1040 >20.1
b 674 7080 451 >20.6
u 649 6874 471 >20.4
uvw1 625 6670 469 >20.3
uvm2 600 6465 467 >20.1
uvw2 704 7468 430 >20.4
white 88 7284 628 >21.4
-----------------------------------------------------------------
The quoted upper limits have not been corrected for the expected
Galactic extinction along the line of sight corresponding to a
reddening of E_{B-V} = 1.3 mag. All photometry is on the UVOT flight
system described in Poole et al. (2008, MNRAS, 383, 627).
GCN Circular 8018
Subject
GRB 080723A: optical upper limit
Date
2008-07-25T14:19:30Z (17 years ago)
From
Graziella Pizzichini at IASF/CNR,Bologna <pizzichini@iasfbo.inaf.it>
F. Munz (INAF/IASF Bologna), F. Terra (Second University of Roma "Tor
Vergata"),,G. Greco, C. Bartolini, A. Guarnieri, A. Piccioni (Bologna
University), G. Pizzichini (INAF/IASF Bologna), D. Nanni (INAF/OAR and
Second University of Rome "Tor Vergata"), S. Galleti, R. Gualandi (Bologna
Observatory) report:
We observed the field of GRB 080723A (GCN 8000 Stamatikos et al.)
with the 152 cm telescope located in Loiano under clear sky conditions
(seeing~2.5").
In our 20 min exposure in the Rc filter at mean time 2008 July 23
20.62 UT we do not detect any afterglow candidate in the enhanced Swift-XRT
position (GCN 8001, Beardmore et al.).
Our 3-sigma limiting magnitude is R~20 (based on Nomad1 catalogue).
In this area there is a strong galactic extinction, A_lambda ~ 4 mag in R
from the NASA/IPAC extragalactic data base.
The image has been posted in our public directory
from where it can be retrieved by sftp using
hostname: ermione.bo.astro.it
username: publicGRB
password: GRB_bo
directory: GRB080723A