GRB 070531
GCN Circular 6475
Subject
GRB 070531: Swift detection of a burst
Date
2007-05-31T02:30:45Z (18 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
C. B. Markwardt (GSFC/UMD), L. M. Barbier (NASA/GSFC),
S. D. Barthelmy (GSFC), M. M. Chester (PSU), N. Gehrels (NASA/GSFC),
S. D. Hunsberger (PSU), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL) and
M. Stamatikos (NASA/ORAU) report on behalf of the Swift Team:
At 02:10:17 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070531 (trigger=280958). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 6.678, +74.304 which is
RA(J2000) = 00h 26m 43s
Dec(J2000) = +74d 18' 14"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows a single FRED-like peak
with a duration of about 20 sec. The peak count rate
was ~1000 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began taking data at 02:12:25 UT, 128 seconds after the BAT
trigger. The XRT on-board centroid algorithm did not find a source in the
image and no prompt position is available. We are waiting for down-linked
data to detect and determine a position for the source.
UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm)
filter starting 131 seconds after the BAT trigger. No afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of
the BAT error circle. The typical 3-sigma upper limit has been about 18.5 mag.
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 expected extinction corresponding to E(B-V) of
0.38.
GCN Circular 6476
Subject
GRB 070531: Liverpool Telescope Optical Observations
Date
2007-05-31T03:55:08Z (18 years ago)
From
Andreja Gomboc at LT,ARI,Liverpool JMU <ag@astro.livjm.ac.uk>
A. Gomboc (Univ. of Ljubljana), R.J. Smith, C.G. Mundell, A. Melandri,
I.A. Steele, D. Carter, A. Monfardini, C.J. Mottram, S. Kobayashi, D.
Bersier, M. Burgdorf (Liverpool JMU) and C. Guidorzi
(Uni-Bicocca/INAF-OAB) report:
The 2-m Liverpool Telescope robotically followed up GRB 070531 (Swift
trigger 280958, GCN 6475 Markwardt et al.) and started observing the field
at 3.7 min after the trigger time with the RINGO polarimeter. Photometric
observations started at 11.9 min after the trigger time.
In first images we do not detect any new object down to:
Filter t_mid (min from GRB) Tot_Exp (s) Lim
-------------------------------------------------------------------
r' 13.2 60 18.2
i' 19.0 120 17.9
------------------------------------------------------------------
Magnitudes were calibrated vs R2 and I mag from the USNOB1 catalogue.
Further analysis is ongoing.
GCN Circular 6477
Subject
GRB 070531: Swift-XRT position
Date
2007-05-31T06:04:29Z (18 years ago)
From
Kim Page at U.of Leicester <kpa@star.le.ac.uk>
K.L. Page (U. Leicester) & C.B. Markwardt (GSFC/UMD) report on behalf of
the Swift-XRT team:
We have analysed the first orbit of data (930 seconds in Photon Counting
mode) for GRB 070531 (trigger number 280958) and find an uncatalogued,
fading X-ray source at a position of RA, Dec 6.73989, 74.3131, which is
RA(J2000) = 00 26 57.57
Dec(J2000) = +74 18 47.0
with an uncertainty of 3.7 arcsec (radius, 90% containment). This is 69
arcsec from the on-board BAT position (GCN Circ. 6475, Markwardt et al.),
within the BAT error circle.
This circular is an official product of the Swift-XRT team.
GCN Circular 6478
Subject
GRB 070531: I-band observations from IAC80
Date
2007-05-31T10:08:01Z (18 years ago)
From
Antonio Deugarte at IAA-CSIC <deugarte@iaa.es>
A. de Ugarte Postigo, A.J. Castro-Tirado (IAA-CSIC,
Granada), J. Benko (Konkoly Observatory, Hungary)
and A. de la Nuez (IAC Tenerife), on behalf of a larger
collaboration, report:
"We have observed the field of GRB 070531 (Markwardt
et al., GCNC 6475) in I-band using the IAC80 telescope
at Iza�a Observatory (Spain) starting at 04:01 UT (1.85
hours after the burst). A combined image of 3960 s
does not show any source within the XRT error box
(Page et al. GCNC 6477). The image is significantly
deeper than the DSS2.
The image is posted at:
http://www.iaa.es/~deugarte/GRBs/070531/GRB070531.gif "
This message can be quoted
GCN Circular 6479
Subject
GRB 070531: Swift-BAT refined analysis
Date
2007-05-31T15:05:12Z (18 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
G. Sato (GSFC/ISAS), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 070531 (trigger #280958)
(Markwardt, et al., GCN Circ. 6475). The BAT ground-calculated position is
RA, Dec = 6.722, 74.316 deg which is
RA(J2000) = 00h 26m 53.3s
Dec(J2000) = 74d 18' 58"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 44%.
The mask-weighted light curve shows a singe FRED peak starting at T_0
with a long weak tail out to at least T+150 sec. There is a 20-sec
gap in the data -- the weak emission is back to background by T+170 sec.
T90 (15-350 keV) is 44 +- 2 sec (estimated error including systematics).
The time-averaged spectrum from T-2.4 to T+44.6 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.41 +- 0.20. The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+1.08 sec in the 15-150 keV band
is 1.0 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
GCN Circular 6480
Subject
GRB 070531: NOT nIR observations
Date
2007-05-31T15:09:03Z (18 years ago)
From
Antonio Deugarte at IAA-CSIC <deugarte@iaa.es>
A. de Ugarte Postigo, A.J. Castro-Tirado (IAA-CSIC,
Granada), C. Gonzalez (IAC Tenerife), A. Cabrera
(GTC Project Office) on behalf of a larger
collaboration, report:
"We have observed the field of GRB 070531 (Markwardt
et al., GCNC 6475) in J, H and K-bands using the 2.5mNOT
(+NOTCAM) Roque de los Muchachos Observatory (Spain)
starting at 04:17 UT (2.11 hours after the burst). We do
not detect any source in the XRT error box (Page et al.
GCNC 6477) down to J~19.5 (3-sigma)."
This message can be quoted
GCN Circular 6481
Subject
Swift/UVOT refined analysis of GRB070531
Date
2007-05-31T20:28:55Z (18 years ago)
From
Massimiliano de Pasquale at MSSL-UCL <mdp@mssl.ucl.ac.uk>
M. De Pasquale (MSSL/UCL) and C. B. Markwardt (GSFC/UMD)
report, on the behalf of Swift UVOT team:
The Swift Ultraviolet/Optical telescope (UVOT) began
its White filter finding chart exposure of GRB070531
(Markwardt et al., GCN circ. 6475) 135 seconds after
the trigger. No optical afterglow is detected inside
the refined XRT error circle (Page et al., GCN circ.
6477), in the initial V and White filter exposures and
the summed exposures in all filters.
In the following table, we report the 3 sigma
upper limits for any optical afterglow .
Filter Time (s) Exp(s) 3sigma UL Mag
White 132-231 98 19.5
White 132-966 207 19.9
V 238-637 393 19.2
V 238-1111 524 19.3
B 716-726 10 18.2
U 692-4845 76 18.9
UW1 668-4803 236 19.2
UM2 643-4598 236 19.5
UW2 745-764 20 17.8
No correction has been made for the Galactic
reddening toward the burst, E(B-V)=0.38