GRB 080723, GRB 080723A
GCN Circular 8018
Subject
GRB 080723A: optical upper limit
Date
2008-07-25T14:19:30Z (18 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
GCN Circular 8012
Subject
GRB 080723A: Swift/UVOT Upper Limits
Date
2008-07-24T14:32:06Z (18 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 8007
Subject
GRB 080723, Swift-BAT refined analysis
Date
2008-07-23T18:48:45Z (18 years ago)
From
Hans Krimm at NASA-GSFC <hans.a.krimm@nasa.gov>
M. Stamatikos (GSFC/ORAU), S. D. Barthelmy (GSFC), W. Baumgartner
(GSFC/UMBC),
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), A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC),
G. Sato (ISAS), J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 080723 (trigger #317662)
(Stamatikos, et al., GCN Circ. 8000). The BAT ground-calculated position is
RA, Dec = 274.461, -6.910 deg which is
RA(J2000) = 18h 17m 50.6s
Dec(J2000) = -06d 54' 34.8"
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The burst was in the fully coded part of the BAT field of view.
The mask-weighted light curve showed a double-peaked structure, with the
first peak extending from T-1 sec to T+4 sec, and the second smaller
peak from T+6 sec to T+20 sec. T90 (15-350 keV) is 17.3 +- 3.0 sec
(estimated error including systematics).
The time-averaged spectrum from T-0.2 to T+18.7 sec is best fit by a
simple power-law model. The power law index of the time-averaged
spectrum is 1.77 +- 0.21. The fluence in the 15-150 keV band is
3.3 +- 0.4 x 10-7 erg/cm2. The 1-sec peak photon flux measured from
T-0.13 sec in the 15-150 keV band is 0.9 +- 0.1 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/317662/BA/
GCN Circular 8004
Subject
GRB 080723A: Swift-XRT refined analysis
Date
2008-07-23T15:35:27Z (18 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 8001
Subject
GRB 080723: Enhanced Swift-XRT position
Date
2008-07-23T10:42:19Z (18 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester)
report on behalf of the Swift-XRT team.
Using 5309 s of XRT Photon Counting mode data and 9 UVOT
images for GRB 080723, 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 = 274.49035, -6.89952 which is equivalent
to:
RA (J2000): 18h 17m 57.68s
Dec (J2000): -06d 53' 58.3"
with an uncertainty of 1.7 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.
GCN Circular 8000
Subject
GRB 080723: Swift detection of a burst
Date
2008-07-23T04:40:07Z (18 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
M. Stamatikos (NASA/ORAU), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), S. T. Holland (CRESST/USRA/GSFC),
S. D. Hunsberger (PSU), H. A. Krimm (CRESST/GSFC/USRA),
C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:
At 04:19:24 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080723 (trigger=317662). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 274.512, -6.923 which is
RA(J2000) = 18h 18m 03s
Dec(J2000) = -06d 55' 20"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). Because the BAT light curve has not been
received, we cannot comment on the burst profile at this time. However,
there is a strong 8.4 sigma excess detected in the scaled map image,
which strongly suggests a real gamma-ray burst occurred.
The XRT began observing the field at 04:20:50.2 UT, 85.8 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 274.48985,
-6.89931 which is equivalent to:
RA(J2000) = 18h 17m 57.56s
Dec(J2000) = -06d 53' 57.5"
with an uncertainty of 2.7 arcseconds (radius, 90% containment). This
location is 116 arcseconds from the BAT onboard position, within the
BAT error circle.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (3.94e+21
cm^-2, Kalberla et al. 2005), with an excess column of 5.7
(+6.36/-4.59) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm)
filter starting 92 seconds after the BAT trigger. No afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 0% of
the XRT error circle. The 8'x8' region for the list of sources generated on-
board covers 100% of the BAT error circle. The list of sources is typically
complete to about 18 mag. No correction has been made for the large Galactic
expected extinction corresponding to E(B-V) of 1.3 mag.
Burst Advocate for this burst is M. Stamatikos (michael AT milkyway.gsfc.nasa.gov).
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.)