GRB 110726A
GCN Circular 12196
Subject
GRB 110726A: Swift detection of a burst
Date
2011-07-26T01:48:27Z (14 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
C. A. Wolf (PSU), S. D. Barthelmy (GSFC),
S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU),
O. M. Littlejohns (U Leicester), C. B. Markwardt (NASA/GSFC),
A. Melandri (INAF-OAB), C. J. Mountford (U Leicester),
D. M. Palmer (LANL), T. Sakamoto (NASA/UMBC), C. J. Saxton (UCL-MSSL),
M. H. Siegel (PSU), E. Sonbas (GSFC/USRA/Adiyaman Univ.),
M. Stamatikos (OSU/NASA/GSFC), C. A. Swenson (PSU) and
E. Troja (NASA/GSFC/ORAU) report on behalf of the Swift Team:
At 01:30:40 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 110726A (trigger=458059). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 286.751, +56.053 which is
RA(J2000) = 19h 07m 00s
Dec(J2000) = +56d 03' 12"
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 10 sec. The peak count rate
was ~2000 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 01:31:38.7 UT, 58.2 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 286.7161,
56.0712 which is equivalent to:
RA(J2000) = 19h 06m 51.87s
Dec(J2000) = +56d 04' 16.3"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 95 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.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (5.60 x
10^20 cm^-2, Kalberla et al. 2005), with an excess column of 1.8
(+1.73/-1.55) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White
filter starting 59 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 100% of the XRT error circle. The typical
3-sigma upper limit has been about 19.6 mag. No correction has been
made for the expected extinction corresponding to E(B-V) of 0.08.
Burst Advocate for this burst is C. A. Wolf (cwolf AT swift.psu.edu).
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 12198
Subject
GRB 110726A: Liverpool Telescope observations
Date
2011-07-26T03:37:41Z (14 years ago)
From
Andrea Melandri at Liverpool John Moores U <axm@astro.livjm.ac.uk>
A. Melandri (INAF-OAB), D. Bersier and R. Smith (Liverpool JMU)
report on behalf of a large collaboration:
The 2-m Liverpool Telescope robotically followed up GRB110726A (SWIFT
trigger 458059; Wolf et al. GCN 12196) starting 190 seconds after the
GRB trigger time. Initial RINGO2 polarimeter frames detected no
candidate optical transient. Switching to broad band imaging, we do
detect an uncatalogued source inside the XRT error circle, consistent
wih the proposed optical counterpart of Schaefer et al. (GCN Circ.
12197), in all three SDSS-gri filters. Our preliminary photometry gives:
Mid time from Total Exp Filter Magnitude
trigger (min) (s)
------------------------------------------------
14.7 10 R 19.0 +/- 0.1
30.0 60 R 19.6 +/- 0.1
20.1 30 I 18.6 +/- 0.1
33.0 60 I 19.1 +/- 0.1
------------------------------------------------
The observed decay is rather shallow (power law index ~0.4) for the
next 45 minutes, unlike the initial behavior observed by ROTSE.
Magnitudes have been calibrated from the nearby USNOB-1 stars.
Observations still ongoing.
GCN Circular 12199
Subject
GRB 110726A: Swift/UVOT Detection
Date
2011-07-26T04:02:40Z (14 years ago)
From
Mike Siegel at PSU/Swift MOC <siegel@astro.psu.edu>
M.H. Siegel (PSU) and C. A. Wolf (PSU) report on behalf
of the Swift/UVOT team:
Swift/UVOT began observations of the field of GRB 110726A (Wolf et al. 2011,
GCN 12196) 59 seconds after the BAT trigger. The 150 second finding chart
in the White filter reveals a candidate afterglow in the rapidly available
2.7'x2.7' sub-image at:
RA(J2000) = 19:06:52.06 = 286.71693
DEC(J2000) = +56:04:16.6 = 56.0713
with a 90%-confidence error radius of about 0.6 arc sec. This is consistent
with the afterglow reported by both the XRT (Wolf et al.) and ROTSE (Schaefer
et al., 2011, GCN 12197). The estimated magnitude is 17.80 with a 1-sigma
error of about 0.06. No correction has been made for the expected extinction
corresponding to E(B-V) of 0.08.
GCN Circular 12200
Subject
GRB 110726A: Enhanced Swift-XRT position
Date
2011-07-26T10:30:39Z (14 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester)
report on behalf of the Swift-XRT team.
Using 629 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 110726A, 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 = 286.71752, +56.07123 which is equivalent
to:
RA (J2000): 19h 06m 52.21s
Dec (J2000): +56d 04' 16.4"
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 12201
Subject
GRB 110726A: Swift-BAT refined analysis
Date
2011-07-26T11:38:19Z (14 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU),
J. Tueller (GSFC), T. N. Ukwatta (MSU), C. A. Wolf (PSU)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+572 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 110726A (trigger #458059)
(Wolf, et al., GCN Circ. 12196). The BAT ground-calculated position is
RA, Dec = 286.713, 56.070 deg which is
RA(J2000) = 19h 06m 51.2s
Dec(J2000) = +56d 04' 11.0"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
The mask-weighted light curve shows a single peak starting at ~T-1 sec,
peaking at ~T+2 sec, and ending at ~T+5 sec. T90 (15-350 keV) is
5.2 +- 1.1 sec (estimated error including systematics).
The time-averaged spectrum from T-0.9 to T+5.0 sec is best fit by a power law
with an exponential cutoff. This fit gives a photon index 0.64 +- 0.87,
and Epeak of 46.5 +- 11.8 keV (chi squared 79.8 for 56 d.o.f.). For this
model the total fluence in the 15-150 keV band is 2.2 +- 0.3 x 10^-7 erg/cm2
and the 1-sec peak flux measured from T+0.61 sec in the 15-150 keV band is
1.0 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index
of 1.86 +- 0.18 (chi squared 87.7 for 57 d.o.f.). 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/458059/BA/
GCN Circular 12202
Subject
GRB110726A: Gemini-N tentative redshift
Date
2011-07-26T17:19:31Z (14 years ago)
From
Antonino Cucchiara at LBNL <acucchiara@lbl.gov>
A. Cucchiara (UC Santa Cruz), J. S. Bloom and S. B. Cenko (UC Berkeley)
report on behalf of a larger collaboration:
"We observed the field of GRB 110726A at 06:14 UT (~0.19 days
after the burst) with the GMOS camera mounted on the
Gemini-North telescope.
We obtained a sequence of 2x900 seconds spectra centered at
6000 Angstrom and covering 4000-8100A wavelength range.
The object is well detected and present a featureless continuum
except for a weak double line which we interpret as a signature
of MgII 2796,2803 at redshift z = 1.036.
No other clear features are detected.
Therefore, we suggest 1.036 < z < 2.7 as redshift range for
GRB 110726A.
We thank the Gemini-N staff for performing this observation,
in particular J. Holt."
GCN Circular 12203
Subject
GRB 110726A: Further Swift/UVOT Observations
Date
2011-07-26T19:00:16Z (14 years ago)
From
Mike Siegel at PSU/Swift MOC <siegel@astro.psu.edu>
B.L. Porterfield (PSU), M.H. Siegel (PSU) and C.A. Wolf (PSU)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB
110726A 60 s after the BAT trigger (Wolf et al., GCN Circ. 12196).
A fading source consistent with the XRT position is detected in
the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 19:06:52.08 = 286.71700 (deg.)
Dec (J2000) = +56:04:16.5 = 56.07126 (deg.)
with an estimated uncertainty of 0.51 arc sec. (radius, 90%
confidence).
Preliminary detections and 3-sigma upper limits using the UVOT
photometric system (Poole et al. 2008, MNRAS, 383, 627) for the
early exposures are listed below.
Filter T_start(s) T_stop(s) Exp(s) Mag
white fc 60 210 147 17.84 +/- 0.04
white 6348 6520 169 >20.85
v 602 11374 806 20.61 +/- 0.27
b 528 6344 235 20.44 +/- 0.22
u fc 272 522 246 18.41 +/- 0.08
u 5938 17370 1081 >21.25
w1 653 5934 216 >20.5
m2 628 12301 825 >21.1
w2 578 10448 649 >21.5
The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.08 in the direction
of the burst (Schlegel et al. 1998).
GCN Circular 12204
Subject
GRB110726A: MITSuME Ishigakijima Optical Observation
Date
2011-07-27T00:03:12Z (14 years ago)
From
Daisuke Kuroda at OAO/NAOJ <dikuroda@oao.nao.ac.jp>
D. Kuroda (OAO, NAOJ), H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ),
K. Yanagisawa (OAO, NAOJ), S.Nagayama (NAOJ), M. Yoshida (Hiroshima),
K. Ohta (Kyoto) and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME collaboration:
We observed the field of GRB 110726A (Wolf et al., GCN 12196)
with the optical three color (g', Rc and Ic) CCD camera attached
to the Murikabushi 1m telescope of Ishigakijima Astronomical
Observatory.
The observation started on 12:56:13 UT (~11.4 h after the burst). We
detected the previously reported afterglow (Schaefer et al., GCN 12197;
Melandri et al., GCN 12198) in Rc bands.
Photometric results and three sigma upper limits of the OT are
listed below. We used GSC2.3 catalog for flux calibration.
#T0+[day] MID-UT T-EXP[sec] g' Rc Rc_err Ic
----------------------------------------------------------------------
0.53142 14:15:55 7020.0 >22.3 21.8 0.2 >20.7
----------------------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
GCN Circular 12205
Subject
GRB 110726A: ROTSE-III refined analysis, fast decay in early phase
Date
2011-07-27T00:49:50Z (14 years ago)
From
Weikang Zheng at U.of Michigan <zwk@umich.edu>
W. Zheng (U Mich), B. E. Schaefer (Louisiana State), H. Flewelling
(IfA/Hawaii), report on behalf of the ROTSE collaboration:
Further analysis to the early optical observations of GRB 110726A from
ROTSE-IIId (Schaefer et al. GCN 12197) shows that, the OT decayed
quickly in early time after ~140s. The OT is detected in our first
co-added of 10 images (14s -142s) with magnitude ~16.1 +/- 0.2. However,
in our second co-added of 10 images (150s - 429s), and afterward
observations, the OT had faded to below our limiting magnitude of ~18.0,
this gives a decay index larger than -1.7, which is much steeper than
the later decay index reported by Melandri et al. (GCN 12198) of ~-0.4
15 minutes after the burst. We summarize the result below:
t_start t_stop mag err detection? number of co-added images
14.0 74.0 16.1 0.3 Yes 5
82.0 142.0 16.1 0.3 Yes 5
150.0 285.0 17.8 - Upper limit 5
293.0 429.0 17.8 - Upper limit 5
GCN Circular 12206
Subject
GRB 110726A: IAC80 R-band observations
Date
2011-07-27T02:09:41Z (14 years ago)
From
Javier Gorosabel at IAA-CSIC <jgu@iaa.es>
J. Gorosabel (IAA-CSIC), D. Jimenez (IAC), A.J. Castro-Tirado (IAA-CSIC), A. de Ugarte Postigo (DARK/NBI), report on behalf of a larger collaboration:
"We carried out R-band observations of the GRB 110726A XRT error circle (Osborne et al., GCNC 12200) with the 0.82m IAC80 telescope at the Observatorio del Teide, Tenerife. A single exposure of 600s taken on July 26.19673-26.20367 UT (3.21-3.38 hours post GRB) shows the optical afterglow (Schaefer et al., GCNC 12197) at a preliminary magnitude of R~20.8. We used as photometric reference the R=18.06 USNO B1.0 star 1460-0295684, located at RA(J2000)=19:06:51.534, DEC(J2000)=+56:04:41.20."
GCN Circular 12207
Subject
GRB 110726A: EVLA observations
Date
2011-07-27T03:30:03Z (14 years ago)
From
Ashley Zauderer at CfA <bevinashley@gmail.com>
A. Zauderer, E. Berger (Harvard/CfA), and D. A. Frail (NRAO) report on
behalf of a larger collaboration:
"We observed GRB 110726A (GCN 12196) with the EVLA beginning on 2011
July 26.19 UT (3.1 hours after the burst) at 5.8 GHz. No source is
detected in coincidence with the optical counterpart (GCNs 12197,12199)
to a 3-sigma limit of about 60 microJy."
GCN Circular 12210
Subject
GRB 110726A: optical upper limit in CrAO
Date
2011-07-29T14:38:54Z (14 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
V. Rumyantsev, N. Pit (CrAO), A. Pozanenko (IKI) report on behalf of larger
GRB follow-up collaboration:
We observed the field of the Swift GRB 110726A (Wolf et al., GCN 12196)
with AZT-11 telescope of CrAO between Jul. 26 (UT) 18:48 - 20:13. We do not
detect the afterglow (Schaefer et al., GCN 12197; Melandri et al., GCN
12198) . The photometry is based on the star used in GCN 12206 (Gorosabel
et al.) USNO B1.0 1460-02955684 (19 06 51.53 +56 04 41.2 ) assuming
R=18.06:
T0+ Filter, Exposure, OT, Upper Limit (3 sigma)
(mid, d) (s)
0.7511 R 29x180 n/d 21.5
GCN Circular 12243
Subject
GRB 110726A: Swift-XRT refined Analysis
Date
2011-08-03T12:34:39Z (14 years ago)
From
Chris Wolf at PSU <cwolf@swift.psu.edu>
C. A. Wolf (PSU) reports on behalf of the Swift-XRT team:
We have analysed 50 ks of XRT data for GRB 110726A (Wolf et al. GCN
Circ. 12196), from 47 s to 421.3 ks after the BAT trigger. The data
comprise 1.3 ks in Windowed Timing (WT) mode (the first 4 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 Osborne et
al. (GCN. Circ 12200).
The late-time light curve (from T0+4.1 ks) can be modelled with a
power-law decay with a decay index of alpha=1.26 (+0.16, -0.15).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.12 (+0.22, -0.21). The
best-fitting absorption column is 1.6 (+/-0.5) x 10^21 cm^-2, in
excess of the Galactic value of 5.6 x 10^20 cm^-2 (Kalberla et al.
2005). The PC mode spectrum has a photon index of 2.15 (+0.12, -0.28)
and a best-fitting absorption column of 9.6 (+3.9, -4.0) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.4 x 10^-11 (4.5 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 9.6 (+3.9, -4.0) x 10^20 cm^-2
Galactic foreground: 5.6 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 2.15 (+0.12, -0.28)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00458059.
This circular is an official product of the Swift-XRT team.
GCN Circular 12251
Subject
GRB 110726A: two epochs of SAO RAS optical observations
Date
2011-08-06T07:04:37Z (14 years ago)
From
Vladimir Sokolov at SAO RAS <sokolov@sao.ru>
A.S.Moskvitin, V.V.Sokolov
report on behalf of the SAO RAS GRB follow-up team:
We observed the field of GRB 110726A (Wolf et al., GCN 12196) with two
optical telescopes of SAO RAS: the 1-m Zeiss-1000 on July, 26/27 in B
and Rc bands and the 6-m BTA + Scorpio on July, 29/30 in Rc band.
We clearly detected an optical transient at the place reported by
Schaefer, Zheng & Flewelling (GCN Circ. 12197, ROTSE-III) and
Siegel & Wolf (GCN Circ. 12199, Swift/UVOT). Results of SAO RAS
observations of OT are presented in the following table.
_______________________________________________________________________
date of July, UT filter exp. magnitude telescope
_______________________________________________________________________
26.833 -- 27.017 Rc 17 x 300 sec. 22.17 +/- 0.12 Zeiss-1000
26.856 -- 27.022 B 16 x 300 sec. 23.47 +/- 0.17 Zeiss-1000
29.819 -- 29.861 Rc 15 x 180 sec. 23.34 +/- 0.09 BTA
_______________________________________________________________________
We use USNO-B.1 1460-0295684 (R. A. = 19:06:51.53, Dec. = +56:04:41.2,
Epoch = 2000.0) with the magnitudes B2 = 20.39, R2 = 18.06
(Gorosabel et al. GCN Circ. 12206) as the reference star.
At the BTA image (ftp://ftp.sao.ru/pub/grb/GRB110726A/GRB110726A_BTA.jpeg)
we detected one more faint object with R = 25.21 +/- 0.30, located 3.5"
North-East from the Swift/UVOT position. According to the Gemini-N redshift
range 1.036 < z < 2.7 reported by Cucchiara Bloom & Cenko (GCN Circ. 12202)
this angle size corresponds to (110 -- 370) +/- 20 kpc.
The message may be cited.