GRB 070520B
GCN Circular 6425
Subject
GRB 070520B: Swift detection of a burst
Date
2007-05-20T18:14:26Z (18 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
A. Moretti (INAF-OAB), S. D. Barthelmy (GSFC), M. M. Chester (PSU),
N. Gehrels (NASA/GSFC), C. Gronwall (PSU), J. A. Kennea (PSU),
V. Mangano (INAF-IASFPA), P. T. O'Brien (U Leicester),
D. M. Palmer (LANL), P. Romano (Univ. Bicocca & INAF-OAB),
M. Stamatikos (NASA/ORAU), E. Troja (INAF-IASFPA) and
S. D. Vergani (DIAS-DCU) report on behalf of the Swift Team:
At 17:44:53 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070520B (trigger=279898). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 121.951, +57.617 which is
RA(J2000) = 08h 07m 48s
Dec(J2000) = +57d 37' 00"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows a single peak
with a duration of about 5 sec. The peak count rate
was ~1000 counts/sec (15-350 keV), at ~0 sec after the trigger.
This burst occurred during a Malindi data downlink session
which buffered the initial notices for up to 12 minutes.
The XRT began observing the field at 17:46:31 UT, 98 seconds after the
BAT trigger. Using prompt downlinked data
XRT found a bright and flaring uncatalogued X-ray source
located at RA, Dec 121.8798, 57.6092 which is
RA(J2000) = 08h 07m 31.1's
Dec(J2000) = +57d 36' 33.1''
with an uncertainty of 4.3 arcsec (radius, 90% containment).
This location is 138 arcseconds from the BAT on-board position,
within the BAT error circle. The initial flux in the 2.5s image
was 1.5e-09 erg/cm2/s (0.2-10 keV).
UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 107 seconds after the BAT trigger. No
afterglow candidate has been found in the initial data products. The
2.7'x2.7' sub-image covers 100% of the XRT error circle. The 3-sigma
upper limit at the XRT position is 19.5 mag. 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 Galactic reddening of E(B-V)=0.04.
GCN Circular 6429
Subject
GRB 070520B, Swift-BAT refined analysis
Date
2007-05-21T00:15:51Z (18 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
T. Sakamoto (GSFC/ORAU), 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), A. Moretti (INAF-OAB),
D. Palmer (LANL), A. Parsons (GSFC), G. Sato (GSFC/ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC)
on behalf of the Swift-BAT team:
Using the data set from T-239 to T+592 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 070520B (trigger #279898)
(Moretti, et al., GCN Circ. 6245). The BAT ground-calculated position is
RA, Dec = 121.886, 57.588 deg which is
RA(J2000) = 08h 07m 32.7s
Dec(J2000) = 57d 35' 15.3"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 59%.
The mask-weighted light curve shows two overlapping peaks starting
at T-4 sec, peaking at T+1 sec, and ending with a long tail at T+200 sec.
T90 (15-350 keV) is 66 +- 4 sec (estimated error including systematics).
The time-averaged spectrum from T-5.0 to T+71.3 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.15 +- 0.21. The fluence in the 15-150 keV band is 9.2 +- 1.1 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.74 sec in the 15-150 keV band
is 0.4 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
GCN Circular 6438
Subject
GRB 070520B: Swift-XRT refined analysis
Date
2007-05-21T10:41:47Z (18 years ago)
From
Alberto Moretti at Obs Brera Merate <alberto.moretti@brera.inaf.it>
A. Moretti (INAF-OAB), P. Romano (Univ Bicocca&INAF-OAB),
C. Guidorzi (Univ Bicocca&INAF-OAB), S.D. Vergani (DIAS-DCU)
report on behalf of the Swift team:
We have analysed the first three orbits of XRT data on GRB 070520B
(Moretti et al., GCN Circ. 6425) with total observing times of 284 s
in Windowed Timing mode (from T+104 to T+388 s) and 5.2 ks in Photon
Counting mode (from T+388 s). The Photon Counting mode image provides
a refined XRT position at RA,DEC(J2000) = 121.87964,+57.60896, which is
RA(J2000) = 08h 07m 31.11s
Dec(J2000) =+57d 36' 32.3"
with an uncertainty of 4.0 arcsec (radius, 90% containment). This is
1.0 arcsec from the initial X-ray position, and 76 arcsec from the
refine BAT position (Sakamoto et al., GCN Circ. 6429).
The XRT light curve (LC) exhibits an initial mildly steep decay (slope
2.5) in the interval (100,170) seconds from the trigger. An intense
FRED-like flare is present between 170 and 390 seconds. In the second
and third orbits the LC shows a decay with a slope is 1.0+/-0.3.
The first WT spectrum, extracted before the flare, can be fit with an
absorbed power law with a photon index of 2.5+/-0.2 and a column
density of (2.1+/-0.4)E21 cm^-2 significantly in excess of the
Galactic value (4.22E20 cm^-2; Dickey & Lockman, 1990). The mean WT
spectrum, extracted during the flare, can be fit with an absorbed
power law with a photon index of 2.6+/-0.1 and a column density of
(2.5+/-0.2)E21 cm^-2 again significantly in excess of the Galactic
value. The absorbed (unabsorbed) 0.3-10.0keV mean flare flux is
9.4E-10 (2.1E-9) ergs cm^-2 s^-1.
Errors are quoted at 90% confidence level.
Assuming the source continues to decay at the present rate, we
predict an XRT count rate of 1E-3 counts/s at T+24 hours,
which corresponds to an unabsorbed flux of 5E-14 ergs cm^-2 s^-1.
This circular is an official product of the Swift XRT team.
GCN Circular 6442
Subject
GRB 070520B: Swift/UVOT Upper Limits
Date
2007-05-21T20:04:41Z (18 years ago)
From
Frank Marshall at GSFC <marshall@milkyway.gsfc.nasa.gov>
F.E. Marshall (NASA/GSFC) and A. Moretti (INAF-OAB)
report on behalf of the Swift/UVOT team:
The Swift/UVOT observed the field of GRB 070520B starting 107 s after
the BAT trigger (Moretti et al., GCN Circ. 6425). We do not find any source
in any of the UVOT observations inside the refined XRT error circle
(Moretti et al., GCN Circ. 6438). The 3-sigma upper limits for detecting
a source inside the XRT error circle in the first finding chart (FC)
exposure and co-added frames are:
Filter T_start(s) T_stop(s) Exp(s) Mag (3-sigma UL)
White (FC) 107 207 98 >20.3
White 107 6197 491 >21.0
V 213 11338 1356 >20.1
B 4360 5992 393 >20.3
U 4155 5788 393 >20.0
UVW1 3950 5583 393 >19.9
UWM2 3745 12043 1094 >20.5
UVW2 4769 10411 1152 >20.9
The values quoted above are not corrected for the expected Galactic
extinction corresponding to a reddening of E(B-V) = 0.04 mag towards
the direction of the burst (Schlegel et al. 1998).
[GCN OPS NOTE(03jun07): Per author's request, the typo in the Subject-line
was changed from "075020B" to "070520B".]
GCN Circular 6447
Subject
GRB 070520B: SARA upper limit
Date
2007-05-22T00:26:39Z (18 years ago)
From
Adria C. Updike at Clemson U <aupdike@clemson.edu>
A. C. Updike, J. R. Puls, and D. H. Hartmann (Clemson University) report
on behalf of the Clemson GRB Follow-Up Team:
We used the 0.9m SARA telescope on Kitt Peak to image the field of GRB
070520B (GCN 6425, Moretti et al.) under decent weather conditions
beginning 9.5 hours after the burst trigger (279898). In 52 minutes of
stacked R-band exposures, we detect no new sources down to a limiting
magnitude of 20.2 +/- 0.4 based on calibration to 8 USNO B1.0 stars.
The SARA Homepage can be found at:
http://saraobservatory.org
This message may be cited.
GCN Circular 6455
Subject
GRB070520B: NIR observations
Date
2007-05-22T20:18:56Z (18 years ago)
From
Paul Price at IfA,UH <price@ifa.hawaii.edu>
T. Minezaki (IoA, Tokyo) and P.A. Price (IfA, Hawaii) report on behalf
of a larger collaboration:
We observed the position of GRB 070520B with the MAGNUM telescope + MIPS
dual-beam imager in R and J bands, at a mean observation time of 12.69
hours after the BAT trigger (GCN #6425). We have only inspected the
J-band images, since other reports have covered the optical (GCN
##6442,6447). We find no afterglow within the XRT error circle to a
limit of J = 20.1 mag.
This message may be cited.
GCN Circular 6485
Subject
GRB070520B: optical observations
Date
2007-06-02T16:32:32Z (18 years ago)
From
Vasilij Rumjantsev at CrAO <rum@crao.crimea.ua>
D. Shakhovskoy, V. Rumyantsev (CrAO), V. Biryukov (CrAO, SAI MSU),
A. Pozanenko (IKI) on behalf of larger GRB follow up collaboration report:
We observed error box of GRB070520B (Moretti et al., GCN 6425) with AZT-11
(1.25m) telescope of CrAO in R-band under not optimal weather conditions
(seeing ~3.6 arcsec) on May 20 between (UT)18:47 and 19:21, i.e. starting 1
hour after burst onset. The weather condition No object is found in a
refined XRT error box (Moretti et al., GCN 6438 ). Limiting magnitude of a
combined image is based on USANO A2.0:
Mid time (UT), Exposure, R_Lim (3sigma)
May 20.753 6x300 21.0
The combined image can be found in
http://grb.rssi.ru/GRB070520B/GRB070520B_AZT11.gif
This message may be cited.
[GCN OPS NOTE(02jun07): The binary attachment was removed as well as the
diagnostics from MIMEDefang reacting to that binary.]