GRB 070520A
GCN Circular 6427
Subject
GRB 070520A: Swift-XRT refined analysis
Date
2007-05-20T21:45:39Z (18 years ago)
From
Pat Romano at OAB-Swift <patrizia.romano@brera.inaf.it>
P. Romano (Univ Bicocca&INAF-OAB), A. Moretti (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 four orbits of XRT data on
GRB 070520A (Romano et al., GCN Circ. 6423) with total observing
times of 79 s in Windowed Timing mode (from T+165 to T+244 s)
and 6.5 ks in Photon Counting mode (from T+3565 s).
The Photon Counting mode image provides a refined XRT
position at RA,DEC(J2000) = 193.36131,+74.99038 which is
RA(J2000) = 12h 53m 26.72s
Dec(J2000) = +74d 59' 25.4"
with an uncertainty of 4.1 arcsec (radius, 90% containment).
This is 2.6 arcsec from the initial X-ray position,
and 43 arcsec from the initial BAT position (Romano et al.,
GCN Circ. 6423).
The XRT light curve exhibits an initial flaring behaviour throughout
the first orbit (in the WT data, i.e., up to T+244 s) with an
underlying power-law with slope 4.4+/-0.5.
The PC data start at T+3565 s, when the count rate had decreased by
three orders of magnitude. The PC data power-law slope is 0.1+/-0.4.
The mean WT spectrum, extracted during the flaring activity,
can be fit with an absorbed power law with a photon index of 3.1+/-0.2
and a column density of (2.2+/-0.4)E21 cm^-2 significantly in excess
of the Galactic value (2.3E20 cm^-2; Dickey & Lockman, 1990).
The absorbed (unabsorbed) 0.3-10.0keV flux for the WT spectrum is
5.2E-10 (1.5E-9) ergs cm^-2 s^-1.
Assuming the source continues to decay at the present rate, we
predict an XRT count rate of 1E-4 counts/s at T+24 hours,
which corresponds to an unabsorbed flux of 5E-15 ergs cm^-2 s^-1.
This circular is an official product of the Swift XRT team.
[GCN OPS NOTE(21may07): Per author's request, the sentence starting
"The absorbed (unabsorbed) 0.3-10.0keV flux ..." was added.]
GCN Circular 6428
Subject
GRB 070520A, Swift-BAT refined analysis
Date
2007-05-21T00:01:27Z (18 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
C. Markwardt (GSFC/UMD), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), D. Palmer (LANL), A. Parsons (GSFC),
P. Romano (Univ. Bicocca & INAF-OAB), T. Sakamoto (GSFC/ORAU),
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+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 070520A (trigger #279817)
(Romano, et al., GCN Circ. 6423). The BAT ground-calculated position is
RA, Dec = 193.255, 75.005 deg which is
RA(J2000) = 12h 53m 1.1s
Dec(J2000) = 75d 0' 16.6"
with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 67%.
The mask-weighted light curve shows single peak with a long tail. The peak
starts at ~T+10 sec, peaks at T+35 sec, and ends at ~T+105 sec. The long
tail appears to extend out to T+370+/-30 sec at the 0.02 +/- 0.01 ph/cm2/sec level.
T90 (15-350 keV) is 18 +- 3 sec (estimated error including systematics).
The time-averaged spectrum from T+25.5 to T+45.4 is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.60 +- 0.33. The fluence in the 15-150 keV band is 2.5 +- 0.5 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+35.80 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 6430
Subject
GRB 070520A: MITSuME Akeno optical upper limits
Date
2007-05-21T04:19:51Z (18 years ago)
From
Nobuyuki Kawai at Tokyo Tech <nkawai@hp.phys.titech.ac.jp>
T. Ishimura, T. Shimokawabe, N. Vasquez, Y. Yatsu, Y. Kudou and
N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
We observed the field of GRB070520A (Romano et al., GCN 6423)
with the 3-color 50cm MITSuME Telescope at Akeno, Japan starting
at 13:15:15 UT, 10 min after the trigger, under a clear, but windy
condition.
In the co-added images of Ic, Rc, and g' bands, we did not detect
any new source in the XRT error circle. The 3-sigma limiting
magnitudes based on USNO-B1.0 (I-band) and NOMAD (R-band,g'-band)
stars are following.
Filter start time end time Exp(s) Mag (3-sigma UL)
-----------------------------------------------------------
Ic 13:15:15 15:06:06 60s * 91 20.3
Rc 13:15:15 15:06:06 60s * 91 21.2
g' 13:15:15 15:06:06 60s * 91 21.1
-----------------------------------------------------------
GCN Circular 6439
Subject
GRB 070520A: Swift UVOT Upper Limits
Date
2007-05-21T13:26:54Z (18 years ago)
From
Stefan Immler at NASA/GSFC <immler@milkyway.gsfc.nasa.gov>
S. Immler (USRA/GSFC) and P. Romano (Univ. Bicocca & INAF-OAB)
report on behalf of the Swift/UVOT team:
The Swift/UVOT observed the field of GRB 070520A starting 152 s after
the BAT trigger (Romano et al., GCN 6423). We do not find any source
in any of the UVOT observations inside the XRT error circle. The 3-sigma
upper limits for detecting a source inside the XRT error circle in the
co-added frames are:
Filter T_start(s) T_stop(s) Exp(s) Mag (3-sigma UL)
White 168 4793 345 >20.2
V 152 11162 1288 >19.6
B 4389 6021 393 >20.0
U 4184 16822 1142 >20.3
UVW1 3979 16047 1279 >20.1
UWM2 3774 11805 1021 >20.4
UVW2 4799 10249 1082 >20.5
The values quoted above are not corrected for the expected Galactic
extinction corresponding to a reddening of E(B-V) = 0.02 mag towards
the direction of the burst (Schlegel et al. 1998).
[GCN OPS NOTE(21may07): Per author's request, the typo in the first
sentence was corrected (070525A --> 070520A).]
GCN Circular 6441
Subject
GRB 070520A: Subaru Observations
Date
2007-05-21T16:14:41Z (18 years ago)
From
Nobuyuki Kawai at Tokyo Tech <nkawai@hp.phys.titech.ac.jp>
T. Hattori, K. Aoki (Subaru Telescope, NAOJ), and N. Kawai
(Tokyo Tech) report on behalf of the Subaru GRB team:
"We observed the field of GRB 070520A (Romano et al., GCN 6423) with
FOCAS on the Subaru Telescope in the z'-band from 06:32(UT) to
07:27(UT) May 21 with a total exposure of 1920 sec (120s*16) under a
non-photometric condition with occasional clouds.
In the XRT error circle (Romano et al., GCN 6427), we find a possible
afterglow candidate as a low-significance source (1.5 sigma) at
RA=12:53:26.52, Dec=74:59:26.6
with a positional uncertainty of 0.4", and a rough estimation of the
magnitude z' ~ 24.
The image may be viewed at
http://www.hp.phys.titech.ac.jp/nkawai/grb/070520A/ "
GCN Circular 6446
Subject
GRB 070520A: SARA upper limit
Date
2007-05-22T00:25:10Z (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 at Kitt Peak under decent weather
conditions to image the field of GRB 070520A (GCN 6423, Romano et al.),
beginning 17 hours after the burst. In 40 minutes of stacked exposures,
we do not detect the object noted by Hattori et al. (GCN 6441) down to a
limiting magnitude of 20 +/- 0.4 in the R-band. This magnitude is based
on calibration to 9 USNO B1.0 stars.
The SARA Homepage can be found at:
http://saraobservatory.org
This message may be cited.