GRB 110208A
GCN Circular 11674
Subject
GRB 110208A: Swift detection of a burst
Date
2011-02-08T21:21:21Z (14 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
V. D'Elia (ASDC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
S. Campana (INAF-OAB), N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
N. P. M. Kuin (UCL-MSSL), C. B. Markwardt (NASA/GSFC),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL),
T. Sakamoto (NASA/UMBC), M. H. Siegel (PSU),
E. Sonbas (GSFC/USRA/Adiyaman Univ.), G. Stratta (ASDC),
C. A. Swenson (PSU) and E. Troja (NASA/GSFC/ORAU) report on behalf of
the Swift Team:
At 21:10:46 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 110208A (trigger=445038). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 22.484, -20.628 which is
RA(J2000) = 01h 29m 56s
Dec(J2000) = -20d 37' 41"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows one peak
with a duration of about 15 sec. The peak count rate
was ~1200 counts/sec (15-350 keV), at 0 sec after the trigger.
The XRT began observing the field at 21:12:06.5 UT, 80.1 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 22.46404, -20.59248 which is equivalent
to:
RA(J2000) = 01h 29m 51.37s
Dec(J2000) = -20d 35' 32.9"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 145 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
http://www.swift.ac.uk/sper. We cannot determine whether the source is
fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 2.31
x 10^20 cm^-2 (Kalberla et al. 2005).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 84 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers none of
the XRT error circle. 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 the expected
extinction corresponding to E(B-V) of 0.02.
Burst Advocate for this burst is V. D'Elia (delia AT asdc.asi.it).
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 11676
Subject
GRB 110208A: Magellan optical observations
Date
2011-02-09T03:29:03Z (14 years ago)
From
Edo Berger at Harvard <eberger@cfa.harvard.edu>
E. Berger, W. Fong (Harvard), and J. Mulchaey (OCIW) report:
"We observed the position of GRB 110208A (GCN #11674) with LDSS3 on the
Magellan/Clay 6.5-m telescope on 2011 February 9.022 UT (3.35 hours after
the burst) in the r- and i-band filters. In single 180 sec exposures in
each filter no object is detected inside the XRT error circle (GCN #11674)
to the limit of the Digitized Sky Survey."
GCN Circular 11677
Subject
GRB 110208A: Swift-BAT refined analysis
Date
2011-02-09T04:22:41Z (14 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), V. D'Elia (ASDC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 110208A (trigger #445038)
(D'Ella, et al., GCN Circ. 11674). The BAT ground-calculated position is
RA, Dec = 22.487, -20.561 deg, which is
RA(J2000) = 01h 29m 56.9s
Dec(J2000) = -20d 33' 40.5"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
The mask-weighted light curve shows a single peak starting at ~T-2 sec,
peaking at ~T+0.5 sec, and ending at ~T+20 sec. T90 (15-350 keV) is
37.4 +- 7.9 sec (estimated error including systematics).
The time-averaged spectrum from T-1.5 to T+40.7 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
2.08 +- 0.31. The fluence in the 15-150 keV band is 2.7 +- 0.6 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.46 sec in the 15-150 keV band
is 0.6 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/445038/BA/
GCN Circular 11678
Subject
GRB 110208A: Enhanced Swift-XRT position
Date
2011-02-09T06:19:23Z (14 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester)
report on behalf of the Swift-XRT team.
Using 5594 s of XRT Photon Counting mode data and 7 UVOT
images for GRB 110208A, 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 = 22.46218, -20.59277 which is equivalent
to:
RA (J2000): 01h 29m 50.92s
Dec (J2000): -20d 35' 34.0"
with an uncertainty of 1.5 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 11679
Subject
GRB 110208A: Swift-XRT refined Analysis
Date
2011-02-09T14:42:48Z (14 years ago)
From
Valerio D'Elia at ASDC <delia@asdc.asi.it>
V. D'Elia (ASDC) reports on behalf of the Swift-XRT team:
We have analysed 20 ks of XRT data for GRB 110208A (D'Elia et al. GCN
Circ. 11674), from 64 s to 47.3 ks after the BAT trigger. The data
comprise 55 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Evans et
al. (GCN. Circ 11678).
The late-time light curve (from T0+4.3 ks) can be modelled with a
power-law decay with a decay index of alpha=1.21 (+0.20, -0.18).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.27 (+/-0.25). The
best-fitting absorption column is 1.1 (+0.4, -0.6) x 10^21 cm^-2, in
excess of the Galactic value of 2.3 x 10^20 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 3.3 x 10^-11 (4.7 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.1 (+0.4, -0.6) x 10^21 cm^-2
Galactic foreground: 2.3 x 10^20 cm^-2
Excess significance: 3.2 sigma
Photon index: 2.27 (+/-0.25)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00445038.
This circular is an official product of the Swift-XRT team.
GCN Circular 11681
Subject
GRB 110208A: Potential afterglow from Magellan
Date
2011-02-09T14:52:13Z (14 years ago)
From
Edo Berger at Harvard <eberger@cfa.harvard.edu>
E. Berger, W. Fong (Harvard), and J. Mulchaey (OCIW) report:
"We inspected our Magellan/LDSS3 r- and i-band images (GCN #11676) at the
location of the refined XRT error circle (GCN #11678). We detect a single
point source in coincidence with the new XRT position in both filters. The
position of the optical source is (J2000):
RA = 01:29:50.86
DEC = -20:35:33.5
with an uncertainty of about 0.3" in each coordinate. The i-band magnitude
is about 21.8 mag. At present we do not have any evidence
for fading of this source."
GCN Circular 11683
Subject
Swift/UVOT observations of GRB110208a
Date
2011-02-09T19:16:17Z (14 years ago)
From
Massimiliano de Pasquale at MSSL-UCL <mdp@mssl.ucl.ac.uk>
M. De Pasquale (MSSL-UCL) and V. D'Elia (ASI-ASDC) report on
behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 110208a 85s
s after the BAT trigger (D'Elia, GCN Circ. 11674). No optical afterglow
consistent with the enhanced XRT position (Evans et al, GCN Circ. 11678)
or the Magellan position (Berger et al., GCN Circ. 11681) is detected in
the initial UVOT exposures or in the summed ones.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC)
exposures and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 85 240 147 >20.6
white 85 18443 1425 >21.5
u_FC 298 548 246 >20.0
u 298 30010 3111 > 21.2
v 628 11030 1190 >20.0
b 553 24229 2021 >21.4
w1 703 29283 2919 >21.3
m2 652 28376 1771 >21.1
w2 603 6810 393 >20.5
We note that there is a bright galaxy a few arcminutes from
the GRB position.
The values quoted above are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.02 in the
direction of the burst (Schlegel et al. 1998).
GCN Circular 11685
Subject
GRB 110208A: Magellan confirmation of the optical afterglow
Date
2011-02-10T03:56:49Z (14 years ago)
From
Wen-fai Fong at CFA <wfong@cfa.harvard.edu>
W. Fong, E. Berger (Harvard), and J. Mulchaey (OCIW) report:
"We re-observed the position of GRB 110208A (GCN #11678) with LDSS3 on the
Magellan/Clay 6.5-m telescope starting on 2011 February 10.03 UT (27.5 hrs
post-burst). In a single 180-sec i-band exposure we no longer detect the
point source described by Berger et al. (GCN #11681) to a limiting
magnitude of i>22.8 mag (3-sigma). We therefore conclude that this source
is the optical afterglow of GRB 110208A."