GRB 070810B
GCN Circular 6852
Subject
GRB 070810B: further XRT analysis
Date
2007-10-05T18:33:55Z (18 years ago)
From
Rhaana Starling at U of Leicester <rlcs1@star.le.ac.uk>
R. Starling, J.P. Osborne, K.L. Page (U. Leicester) and F.E. Marshall
(NASA/GSFC) report, on behalf of the Swift XRT team:
Previously, Swift XRT data for the short GRB 070810B (trigger=287409;
Marshall et al., GCN Circ. 6743) up to 13.8 ks after the BAT trigger
showed two possible sources within the BAT refined error circle, detected
at 2-sigma significance in 7.2 ks and termed S1 and S2 (Starling et al.,
GCN Circ. 6754).
We have analysed a further 12.6 ks of Swift XRT photon counting mode data
beginning 42 days and ending 54 days after the burst, in order to assess
the variability of the two possible afterglow candidates.
In this second epoch of data we detect one X-ray source at 4-sigma
significance within the refined BAT error circle (Sakamoto et al., GCN
Circ. 6753), corresponding to the source S2 described in GCN Circ. 6754.
Using Bayesian analysis we find that S2 has between 20 and 54 counts at
the 99% confidence level or 1.6e-3 to 4.3e-3 count/s, consistent with the
first epoch limits of 5.6e-4 to 3.6e-3 count/s. This suggests that S2 is
a persistent faint source, and not the afterglow of GRB 070810B.
The possible source S1 (GCN Circ. 6754), detected only at the 2-sigma
level in the intial epoch observations, is not detected in the second
epoch observations, providing an upper limit on the count rate of 6.7e-4
count/s at 99% confidence based on the background count rate. This is
above the 3-sigma lower limit on the source count rate at epoch 1 of
5.6e-4 count/s, hence we cannot determine whether or not this source has
faded.
This is an official product of the Swift XRT team.
GCN Circular 6771
Subject
GRB 070810b: Image Subtraction of Multiple Keck Observations
Date
2007-09-01T04:05:55Z (19 years ago)
From
Daniel Kocevski at UC Berkeley <kocevski@berkeley.edu>
D. Kocevski, J.S. Bloom, C. C. Thoene, and J. Prochaska report:
We performed image subtraction between multiple R-band observations
of the error box of short burst GRB070810b (Marshall et al., GCN
6743) with the Keck I telescope (+LRIS). The first epoch of
observations began at (UT) 2007-08-11 14:45:00 followed by a second
epoch six nights later at (UT) 2007-08-17 12:02:00, with equivalent
exposures of 630 and 900 seconds respectively. Image subtraction
using the public POIS-IPP package(*) software shows no variable
sources associated with the S1, S2 XRT positions (GCN 6754 , Starling
et al.) or the S3 position (Thoene et al., GCN 6756) nor any
significant residual sources within the BAT error circle down to a
limiting magnitude of ~25.5 mag in R band. The potential candidate
afterglow close to S2, reported by Pozanenko et al. can be resolved
as two objects in our images, which show no sign of variability
between the two epochs.
* See http://pan-starrs.ifa.hawaii.edu/project/IPP/software/
GCN Circular 6762
Subject
GRB070810b: optical candidate
Date
2007-08-21T17:05:01Z (19 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
V. Rumyantsev (CrAO) , V.Biryukov (SAI, MSU and CrAO), A. Pozanenko (IKI)
report on behalf of larger GRB follow-up collaboration:
We observed the error box of short GRB070810b (Marshall et al., GCN 6743)
with Shajn 2.6m telescope of CrAO on Aug. 10. Series of images were
obtained between (UT) 2007-08-10 22:05:23 and 2007-08-10 23:25:50 in R
filter. The combined image of a total exposure of 4260 s (71x60 s) covers
entire of the error box of GRB 070810b and can be found at
http://grb.rssi.ru/GRB070810b/GRB070810b_ZTSh.gif. The limiting magnitude (3
sigma) calibrated against USNO-A2.0 of the combined image is 24.8 mag.
We investigate the S1, S2 XRT positions of GRB70810b (GCN 6754 , Starling
et al.) and S3 position (Thoene et al., GCN 6756).
There is marginally detected object in a place of the source S1 (see
http://grb.rssi.ru/GRB070810b/GRB070810b_s1_ZTSh.gif).
Both optical sources around S3 (RA = 00:35:46.892 Dec = +08:51:05.96) are
presented in our and Keck's images, see
http://grb.rssi.ru/GRB070810b/GRB070810b_s3_ZTSh.gif.
Comparison of objects around source S2 ( RA = 00h 35m 50.0s Dec = +08d 48'
45.0'' ) in our image ( see
http://grb.rssi.ru/GRB070810b/GRB070810b_s2_ZTSh.gif) with the image
obtained on Aug. 11 (Thoene et al., GCN 6756) reveals a source between two
nearby galaxies. We consider this source as a candidate of the optical
counterpart of GRB070810b and a redshift z~0.49 obtained for the galaxies
(Thoene et al., CN 6756) is quite natural for short GRB detected by Swift.
However more detailed comparison of the images (Keck I and ZTSh) and
additional observations are necessary to secure the nature of the candidate.
The massage can be cited.
GCN Circular 6758
Subject
GRB 070810B : Faulkes Telescope South Observations
Date
2007-08-12T18:59:35Z (19 years ago)
From
Cristiano Guidorzi at INAF-OAB <cristiano.guidorzi@brera.inaf.it>
C. Guidorzi (U. Bicocca/INAF-OAB), R.J. Smith, A. Melandri,
I.A. Steele, C.G. Mundell, M.J. Burgdorf, C.J. Mottram,
M.F. Bode, S.N. Fraser, S. Kobayashi, D.F. Bersier (Liverpool JMU),
A. Gomboc (Ljubljana), P. O'Brien, E. Rol, N. Bannister, N. Tanvir
(U. Leicester) report on behalf of larger GRB collaboration:
On 2007 Aug 10 at 15:22:06 UT the 2-m Faulkes Telescope South
automatically observed the field of GRB 070810B (trigger 287409,
Marshall et al., GCN Circ. 6743).
In our coadded frames we do not detect anything corresponding to
XRT sources 1 or 2 (Starling et al., GCN Circ. 6754)
down to the limiting magnitudes reported below.
Filter Tstart(min) Tstop(min) Exposure(s) M_lim
-------------------------------------------------------
R 2.80 64.3 840 21.2
i' 6.22 54.9 520 21.5
-------------------------------------------------------
Magnitudes are calibrated with respect to USNOB1 R2 in the R filter.
For the SDSS-i' filter we calibrated with the i' magnitudes derived for
USNOB1 field stars by converting from the (R2,I) magnitudes.
GCN Circular 6756
Subject
GRB 070810B: Keck spectroscopy of possible host galaxies
Date
2007-08-12T03:25:02Z (19 years ago)
From
Christina Thoene at Niels Bohr Institute,DARK Cosmo Ctr <cthoene@astro.ku.dk>
Christina C. Thoene (DARK, UC Berkeley), Joshua S. Bloom, Nathaniel R.
Butler (UCB) and Peter Nugent (LBL) report:
We obtained spectra of several sources around the reported XRT positions
of GRB70810B (GCN 6754 , Starling et al.) on Aug. 11, 12:30 UT, using Keck
I + LRIS. No new source is seen in imaging of the field at the same time.
At the position of source 1 ("S1") from Starling et al., there is no
optical counterpart visible. From further analysis of the X-ray data, we
detect another weak X-ray source at RA 00:35:46.892, DEC 08:51:05.96
("S3") which includes a weak optical source.
Within the BAT error circle, there is an early type galaxy (LEDA 1354367)
as noted first in Marshall et. al, GCN 6743, for which we determined a
redshift of z=0.0385 derived from Ca H&K absorption lines.
Around source 2 ("S2"), there are four galaxies of which two show strong
emission lines leading to a redshifts around z=0.49 from OII, OIII and the
Balmer series. The two other galaxies have marginal detections of emission
lines at the same redshift and these galaxies might therefore be part of a
cluster or even interacting.
An image indicating the different XRT positions and galaxies observed can
be found at:
http://lyra.berkeley.edu/~cthoene/GRBs/GRB070810B.png
CT wants to thank Keck support astronomer Greg Wirth and his wife for
excellent dinner support during the observations. Tusend tak!
GCN Circular 6755
Subject
GRB070810B: Swift/UVOT Upper Limits
Date
2007-08-11T19:32:53Z (19 years ago)
From
Peter Brown at PSU <pbrown@astro.psu.edu>
P.J. Brown and F.E. Marshall (NASA/GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT observed the field of GRB 070810B (trigger #287409)
starting 65 s after the BAT trigger (Marshall et al., GCN Circ. 6743).
We do not find any new source in the UVOT observations inside the
refined BAT error circle (Sakamoto et al., GCN Circ. 6753) including
the two low significance XRT sources (Starling et al., GCN Circ. 6754).
The galaxy 2MASX J00355339+0849273 (= LEDA 1354367) is visible in
all filters except uvm2, but does not show signs of variability.
The 3-sigma upper limits for detecting a source 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) 66 165 98 >20.5
white 66 13134 1345 >22.0
v 172 7372 1296 >20.4
b 653 12222 1299 >21.2
u 628 7987 549 >20.3
uvw1 604 7782 549 >20.5
uvm2 579 7577 549 >20.4
uvw2 683 13859 1237 >21.1
The values quoted above are not corrected for the expected Galactic
extinction corresponding to a reddening of E(B-V) = 0.053 mag towards
the direction of the burst (Schlegel et al. 1998).
GCN Circular 6754
Subject
GRB 070810B: XRT refined analysis
Date
2007-08-11T01:59:15Z (19 years ago)
From
Rhaana Starling at U of Leicester <rlcs1@star.le.ac.uk>
R. Starling (U. Leicester), C. Markwardt (CRESST/GSFC/UMD) and F.E.
Marshall (NASA/GSFC) report, on behalf of the Swift XRT team:
We have analysed 7.2 ks of Swift XRT photon counting mode data, beginning
70 s and ending 13.8 ks after the BAT trigger, for the short GRB 070810B
(trigger=287409; Marshall et al., GCN Circ. 6743).
We do not detect any X-ray sources at 3-sigma significance or greater
within the refined BAT error circle (Sakamoto et al., GCN Circ. 6753).
Two low significance (2-sigma) possible sources are found within the BAT
refined error circle at the following positions:
Source 1
RA (J2000) = 00h 35m 51.2s
Dec (J2000) = +08d 51' 21.3''
Source 2
RA (J2000) = 00h 35m 50.0s
Dec (J2000) = +08d 48' 45.0''
Using the Bayesian method we find that both sources have between 4 and 26
counts at the 99% confidence level.
It is not possible to determine at this stage whether or not either of
these sources are fading.
We note that Source 2 lies 1.1 arcmin from the galaxy 2MASX
J00355339+0849273 (= LEDA 1354367; RA, Dec (J2000) = 00h 35m 53.39s,
+08d 49' 27.3''), which has angular diameter approximately 0.7 x 0.3 arcmin.
This is an official product of the Swift XRT team.
GCN Circular 6753
Subject
GRB 070810B, Swift-BAT refined analysis
Date
2007-08-11T00:19:40Z (19 years ago)
From
Craig Markwardt at NASA/GSFC/UMD <craigm@milkyway.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), F. E. Marshall (GSFC),
D. Palmer (LANL), A. Parsons (GSFC), G. Sato (GSFC/ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+303 sec from recent telemetry
downlinks, we report further analysis of BAT GRB 070810B (trigger
#287409) (Marshall, et al., GCN Circ. 6743). The BAT ground-calculated
position is RA, Dec = 8.952, 8.822 deg which is
RA(J2000) = 0h 35m 48.4s
Dec(J2000) = 8d 49' 18"
with an uncertainty of 2.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
The light curve is a single FRED-like peak starting at T+0, and ending
at T+0.12 sec. T90 (15-350 keV) is 80 +- 10 msec (estimated error
including systematics).
The time-averaged spectrum from T+0.008 to T+0.092 sec is best fit by a
simple power-law model. The power law index of the time-averaged
spectrum is 1.44 +- 0.37. The fluence in the 15-150 keV band is
1.2 +- 0.3 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from
T-0.45 sec in the 15-150 keV band is 1.8 +- 0.4 ph/cm2/sec. All the
quoted errors are at the 90% confidence level.
GCN Circular 6747
Subject
GRB 070810B: Xinglong TNT optical Upper Limit
Date
2007-08-10T18:21:53Z (19 years ago)
From
W.K. Zheng at NAOC <zwk@bao.ac.cn>
gcncircL.P. Xin, M.Zhai, Y.L. Qiu, J.Y. Wei, J.Y. Hu, J.S. Deng,
Y. Urata, and W.K. Zheng on behalf of EAFON report:
We have imaged the field of GRB 070810B (Marshall et al., GCN 6743)
with the Xinglong TNT 80cm telescope. Observation started from
15:24:17, 300s after the burst. A series of White and R band images
were obtained. Preliminary analysis shows no new object was seen in
our combined image within BAT error circle. The 3 sigam limit is
~20.5 in our co-added 20*20s White band image with mean time ~550s
after the burst, and ~21.7 in co-added 11*360s R band image with mean
time ~44 minutes after the burst derived from USNO-B1.0, Further
analysis is on going.
This message may be cited.
GCN Circular 6746
Subject
GRB070810B: Optical observations with KANATA
Date
2007-08-10T17:34:52Z (19 years ago)
From
Makoto Uemura at Hiroshima U <uemuram@hiroshima-u.ac.jp>
M. Uemura, A. Arai, O. Nagae, and T. Uehara (Hiroshima Univ.),
report on behalf of the KANATA GRB team:
We started optical imaging of the field of GRB070810B (GCN 6743)
at 15:22:37 UT 10 Aug. using TRISPEC attached to the KANATA
1.5-m telescope at Higashi-Hiroshima Observatory, Japan.
Exposure times are 30 sec for the first 10 frames, then changed
to 123 sec for late frames.
We have performed preliminary analysis for the first 30-min images.
No new bright object was detected. There is no object showing
significant fadings.
Limit magnitudes are estimated from neighbour USNO A2.0 stars as
follows:
10 Aug. UT limit mag. band
15:33:22 20.8 Rc
15:55:04 20.9 Rc
We note that there is a possible minor planet at RA=00:35:59.3,
Dec=+08:50:15 (time=15:33:22 UT). The object is about Rc=20.1,
and moving northward during our observations.
GCN Circular 6743
Subject
GRB 070810B: Swift detection of a short burst
Date
2007-08-10T15:52:16Z (19 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
F. E. Marshall (NASA/GSFC), P. J. Brown (PSU),
J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC),
O. Godet (U Leicester), C. Guidorzi (Univ Bicocca&INAF-OAB),
S. T. Holland (CRESST/GSFC/USRA), J. A. Kennea (PSU),
V. Mangano (INAF-IASFPA), C. B. Markwardt (CRESST/GSFC/UMD),
J. P. Osborne (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL), B. Sbarufatti (INAF-IASFPA),
M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester),
E. Troja (INAF-IASFPA), T. N. Ukwatta (GSFC/GWU) and
D. E. Vanden Berk (PSU) report on behalf of the Swift Team:
At 15:19:17 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070810B (trigger=287409). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 8.940, +8.835 which is
RA(J2000) = 00h 35m 46s
Dec(J2000) = +08d 50' 07"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single short spike
with a duration of < 0.2 sec. The peak count rate
was ~4500 counts/sec (15-350 keV), at ~0 sec after the trigger. The
lightcurves in different bands indicate an intermediate spectrum that is
neither hard nor soft.
The XRT began taking data at 15:20:19 UT, 62 seconds after the BAT
trigger. The XRT on-board centroid algorithm did not find a source in the
image and we do not detect a source in the initial SPER images. However, it is
possible that the source is very faint or lies outside the SPER window.
We await 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 65 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 extinction corresponding to the expected
reddening of E(B-V)=0.05.
We note the presence of the bright extended galaxy
2MASX J00355339+0849273 (= LEDA 1354367) within the BAT error circle.
Burst Advocate for this burst is F. E. Marshall (marshall 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.)