GRB 071118
GCN Circular 7106
Subject
GRB 071118: Swift detection of a burst
Date
2007-11-18T09:29:11Z (18 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <jayc@milkyway.gsfc.nasa.gov>
J. R. Cummings (NASA/UMBC), G. Cusumano (INAF-IASFPA),
N. Gehrels (NASA/GSFC), C. Guidorzi (Univ Bicocca&INAF-OAB),
S. T. Holland (CRESST/USRA/GSFC), C. B. Markwardt (CRESST/GSFC/UMD),
A. Moretti (INAF-OAB), D. M. Palmer (LANL),
G. Tagliaferri (INAF-OAB), T. N. Ukwatta (GSFC/GWU) and
D. E. Vanden Berk (PSU) report on behalf of the Swift Team:
At 08:57:17 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 071118 (trigger=296856). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 299.817, +70.093 which is
RA(J2000) = 19h 59m 16s
Dec(J2000) = +70d 05' 34"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). As is usual for image triggers, there is
no obvious variation in the TDRSS light curve.
The XRT began observing the field at 08:59:20 UT, 123 seconds after the
BAT trigger. Using prompt downlinked data, we find a fading X-ray
source located at RA, Dec 299.7178, 70.1245 which is
RA(J2000) = 19 58 52.27
Dec(J2000) = +70 07 28.2
with an uncertainty of 4.0 arcsec (radius, 90% containment).
This location is 166 arcseconds from the BAT on-board position,
within the BAT error circle. The initial flux in the 2.5s image
was 1.9e-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 132 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 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 XRT error
circle. The list of sources is typically complete to about 18 mag.
However, there may be a marginally detected source inside the XRT
error circle, at RA(J2000) = 19 58 52.1, DEC(J2000) = +70 07 29, with
an uncertainty of 1 arcsecond, that is somewhat obscured by the halo
of a nearby star. No correction has been made for the expected extinction
corresponding to E(B-V) of 0.37.
Burst Advocate for this burst is J. R. Cummings (jayc 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.)
GCN Circular 7109
Subject
GRB 071118, Swift-BAT refined analysis
Date
2007-11-18T20:39:20Z (18 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
C. Markwardt (GSFC/UMD), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
D. Palmer (LANL), T. Sakamoto (GSFC/UMBC), 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 the recent telemetry downlink,
we report further analysis of BAT GRB 071118 (trigger #296856)
(Cummings, et al., GCN Circ. 7106). The BAT ground-calculated position is
RA, Dec = 299.839, 70.130 deg, which is
RA(J2000) = 19h 59m 21.4s
Dec(J2000) = 70d 07' 47"
with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
The mask-weighted light curve shows a broad single peak starting at ~T-25 sec,
peaking at ~T+55 sec, and ending at ~T+110 sec.
T90 (15-350 keV) is 71 +- 20 sec (estimated error including systematics).
The time-averaged spectrum from T+4.5 to T+81.2 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.63 +- 0.29. The fluence in the 15-150 keV band is 5.0 +- 1.0 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+80.26 sec in the 15-150 keV band
is 0.3 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
This burst satisfies Sakamoto/Ukwatta Swift-BAT possible high-z criteria:
1) Power law photon index = 1.63 (PL photon index < 2)
2) 1-s peak photon flux = 0.3 (1-s peak photon flux < 1.0 ph/cm2/s)
3) Light curve variance = 4e-05 (Variance < 0.0001)
4) T90/(Peak photon flux) = 220 (T90/(Peak photon flux) > 200)
Based on a limited sample of bursts, these criteria yield
an 85% chance it has a redshift greater than 3.5.
Deep IR observations are strongly encouraged.
GCN Circular 7111
Subject
GRB071118: Swift XRT refined analysis
Date
2007-11-19T09:59:03Z (18 years ago)
From
Alberto Moretti at Obs Brera Merate <alberto.moretti@brera.inaf.it>
A. Moretti (INAF-OAB), J. R. Cummings (NASA/UMBC), C. Guidorzi
(Univ. Bicocca & INAF-OAB), P. Romano (Univ. Bicocca & INAF-OAB),
P. Evans (U Leicester)report on behalf of the Swift-XRT team:
We have analysed the first 4 orbits of Swift-XRT data obtained for GRB
071118 (trigger number 296856, Cummings et al., GCN Circ. 7106). The
data consist of 122 s in Windowed Timing (WT) mode, starting 128
s after the BAT trigger and 8.8 ks in Photon Counting (PC) mode.
Using 1298 s of overlapping XRT Photon Counting mode and UVOT V-band
data, 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 = 299.71558, 70.12449 which is equivalent to:
RA (J2000): 19 58 51.74
Dec (J2000): +70 07 28.2
with an uncertainty of 1.6 arcsec (radius, 90% confidence). This
location is 2.7 arcseconds from the XRT position measured using prompt
downlinked data (Cummings et al., GCN Circ. 7106) and 152 arcseconds
from the BAT refined position (Markwardt et al. GCN Circ. 7109).
The light-curve, in the first orbit (up to 2 ks from the trigger)
shows a steep decay accompanied by flaring activity Since the second
orbit, the afterglow shows a more regular decay with a shallow phase
(alpha1=0.6+/-0.2) until 11 ks and a steeper decay (alpha2=1.6+/-0.2).
The spectrum formed from all the WT data can be modelled with a
power-law of photon index Gamma = 1.64 +/- 0.13, with an absorbing
column of NH = (2.7 +/- 0.6)e21 cm^-2 (in excess with respect to the
Galactic value of 9.7e20 cm^-2). The spectrum formed from the PC data
can be modelled with a power-law of photon index Gamma = 1.62 +/-
0.06, with an absorbing column of NH = (2.6 +/- 0.4)e21 cm^-2, which
is consistent with the previous one.
Assuming the light-curve continues to decay with alpha2=1.6, the count
rate at 48 hours is predicted to be 0.002 count s^-1. This corresponds
to an observed (unabsorbed) flux of 1.3e-13 (1.7e-13) erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.
GCN Circular 7116
Subject
Swift/UVOT observations of GRB071118
Date
2007-11-19T16:14:54Z (18 years ago)
From
Massimiliano de Pasquale at MSSL-UCL <mdp@mssl.ucl.ac.uk>
M. De Pasquale, P. Schady (MSSL-UCL) and J. Cummings (GSFC/GWU)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began observing the field of GRB 071118 (Cummings
et al, GCN 7106) 123s after the BAT trigger.
In the v band finding chart, an uncatalogued source is detected
inside the refined XRT error circle (Moretti et al 7111) with ~6
sigma significance. This source looks extended; however it is not
found at late times, which indicates that it is the optical
afterglow of GRB 071118. Its detection suggests that this GRB
took place at redshift z<~5. The coordinates of this source are
RA: 19 58 51.8
Dec: +70 07 29.2
with an error of 0.6 arcsecond. No new source is detected within
the XRT error circle in the b, u or uv filters, either in the single
or co-added exposures.
In the table below, we indicate the magnitude of the optical
afterglow and the 3sigma upper limits. We do caution that the
photometry may be affected by the halo of a near bright star and
the crowded field.
Filter Time (s) Exp time (s) Mag
White 134-233 98 > 20.6
White 734-743 9.8 > 19.4
White 874-973 98 20.4 +/- 0.2
White 1484-1983 39 > 20.6
White 5756-7391 393 > 21.4
v 240-639 393 19.1 +/- 0.2
v 774-793 9.8 > 18.1
v 981-1380 393 19.1 +/- 0.2
v 1524-2033 78 > 19.1
v 6166-7801 198 > 19.2
v 17862-18769 885 > 20.4
b 720-1696 87 >20.0
b 5551-7186 393 >20.6
u 695-2093 122 >20.0
u 5345-13654 1096 >21.0
w1 670-2083 136 >19.9
w1 6576-6775 1078 >21.2
um2 646-2058 136 >20.4
um2 11126-18883 1250 >21.2
uw2 750-2009 98 >19.7
uw2 6371-18883 750 >21.1
No correction has been made for the expected high
Galactic extinction, corresponding to E(B-V) of 0.37.
GCN Circular 7118
Subject
GRB 071118: Observations from OSN
Date
2007-11-20T01:55:25Z (18 years ago)
From
Antonio Deugarte at IAA-CSIC <deugarte@iaa.es>
A. de Ugarte Postigo (ESO, Chile), A.J. Castro-Tirado, F.J. Aceituno
& D. Diaz-Fraile (IAA-CSIC, Granada) on behalf of a larger collaboration
report:
We have observed the field of GRB 071118 (Cummings et al. GCN 7106)
with the 1.5m telescope at Sierra Nevada Observatory in Granada (Spain)
starting at 18:00 UT (~9 hours after the burst). We detect the afterglow
reported by UVOT (De Pasquale et al. GCN 7116) in a 18x300s exposure
I-band image (with mean date Nov 18.8038 UT) as a faint object of I~21.7.
It is however not detected in a V band image of 11x300s.
A finding chart can be found at:
http://www.iaa.es/~deugarte/GRBs/071118/GRB071118.jpg
This message may be cited.
GCN Circular 7119
Subject
GRB071118 MITSuME OAO optical observation
Date
2007-11-20T02:43:54Z (18 years ago)
From
Michitoshi Yoshida at Okayama Astrophysical Obs <yoshida@oao.nao.ac.jp>
M. Yoshida, K. Yanagisawa, Y. Shimizu, S. Nagayama, H. Toda (OAO, NAOJ)
and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
We performed optical imaging observations (g', Rc and Ic) of the field
of GRB 071118 (Cummings et al., GCN 7106; Markwardt et al. GCN 7109)
with 50cm MITSuME telescope at Okayama Astrophysical Observatory from UT
9:00:31 (194 sec after the trigger) to UT 13:03 on November 18 2007.
We found a fading source at the position in the XRT error circle
reported by Moretti et al. (GCN 7111) in Rc and Ic bands. We made flux
calibration using NOMAD (for g' and Rc) and USNO B1.0 (for Ic) catalogs.
The photometric results are following.
mid-UT exp-T g' Rc Ic
---------------------------------------------------------
2007-11-18 9:03:22 5min >16.9 18.5+-0.5 >17.8
2007-11-18 10:12:12 25min >19.1 19.1+-0.3 18.5+-0.3
2007-11-18 11:16:35 45min >20.0 20.2+-0.3 19.7+-0.3
2007-11-18 12:33:20 57min >20.3 20.7+-0.4 >20.2
---------------------------------------------------------
GCN Circular 7120
Subject
GRB 071118: P60 Observations
Date
2007-11-20T04:14:34Z (18 years ago)
From
S. Bradley Cenko at Caltech <cenko@srl.caltech.edu>
S. B. Cenko (Caltech) reports on behalf of a larger collaboration:
We have imaged the field of GRB071118 (Cummings et al., GCN 7106) with the
automated Palomar 60-inch telescope beginning at 01:49 UT on 19 November.
We do not detect any source at the location of the optical afterglow (de
Pasquale et al., GCN 7116). Using the USNO-B1 catalog as a reference, we
calculate upper limits of R > 22.5, i' > 22.5 at this epoch.