GRB 110328A
GCN Circular 12214
Subject
Sw J1644+57 (GRB 110328A): Continued VLBA Observations
Date
2011-07-30T19:22:46Z (14 years ago)
From
S. Bradley Cenko at Caltech <cenko@srl.caltech.edu>
G. Bower, S. B. Cenko, J. S. Bloom (UC Berkeley) and B. D. Metzger
(Princeton) report on behalf of a larger collaboration:
We have obtained a second epoch of long-baseline interferometry with the
VLBA of the unusual high-energy transient Sw J1644+57 (GRB 110328A; Levan
et al, Science, 333, 199, 2011; Bloom et al, Science, 333, 203, 2011;
Burrows et al., astro-ph/1104.4787; Zauderer et al., astro-ph/1106.3568).
Observations were obtained on 2011 July 17 at 8.4 and 22 GHz with
recording bandwidth of 512 Mbps. Preliminary analysis of images at both
frequencies reveals a compact (i.e., unresolved) source with flux
densities of 15 and 12 mJy, respectively. Errors in the flux density are
set by the amplitude scale and are estimated at 10%. The 8.4 GHz
localization is consistent with the position obtained from our previous
epoch of VLBA observations on 2011 April 1 and 3 (Levan et al., Science
333, 199, 2011; see also Zauderer et al., astro-ph/1106.3568) at the level
of ~ 300 uas. If we assume expansion with a constant speed from the time
of the initial high-energy detections of this source, this places an upper
limit on the average outflow Lorentz factor of Gamma <~ 5.
GCN Circular 12060
Subject
GMRT detection of GRB 110328A
Date
2011-06-02T19:14:01Z (14 years ago)
From
Sayan Chakraborti at TIFR,Mumbai,India <sayan1984@gmail.com>
Naveen Yadav, Sayan Chakraborti, Alak Ray (TIFR, Mumbai, India)
and Alicia Soderberg (Harvard University, Cambridge, MA) report:
The field of GRB 110328A was observed with the Giant Metrewave
Radio Telescope (GMRT) for 8 hours centred on May 28.8 UT at
an effective frequency of 1264 MHz with a bandwidth of 32 MHz.
We detect a point source consistent with the position of the
transient with a flux of 0.431 +/- 0.049 mJy. The rms noise in
the synthesized image is 0.023 mJy.
We thank the Director GMRT for granting this DDT observation
and the staff of the GMRT that made this observation possible.
GMRT is run by the National Centre for Radio Astrophysics of the
Tata Institute of Fundamental Research.
GCN Circular 12041
Subject
Swift J1644+57/GRB 110328A, Additional HST Observations
Date
2011-05-26T19:51:14Z (14 years ago)
From
Kuntal Misra at STScI <misra@stsci.edu>
Andrew Fruchter, Kuntal Misra, John Graham (STScI), Andrew Levan (U. Warwick), Nial Tanvir (U. Leicester) and Joshua Bloom (UC Berkeley) report for a larger collaboration:
We have re-observed the field of Swift J1644+57/GRB 110328A using the WFC3 on the Hubble Space Telescope. The observations were performed between approximately 13:30 and 14:30 UT on 20 April 2011 using the F160W filter in the IR and the F606W filter in the optical.
As in our previous HST observations (GCN 11881), we obtained four dithered exposures of 250s each in F160W. We find that the source, as measured in a one arcsecond aperture, faded in F160W to an AB magnitude of 20.84. This is a reduction of about 0.09 mag since the previous observation of 4 April 2011.
In the optical F606W filter we again obtained three dithered exposures of 420s each. There is no significant change in total flux in a one-arcsecond aperture. However, subtraction of the F606W images from the two different epochs shows a small (27th mag) residual which lies about 0."05 north of the center of the host. This residual is at the detection limit of the image, due to the increased statistical noise under the host, and in fact lies about 0."06 from the location of the much brighter and more clearly detected IR residual (which is more closely aligned to the center of the host.). Given the astrometric difference between the IR and the optical, we believe it probable that the optical residual is noise; however, we plan to obtain further HST observations which may be able to resolve this issue.
GCN Circular 11956
Subject
GRB 110328A/Swift J164449.3+573451: Maidanak Optical Observation
Date
2011-04-22T12:27:55Z (14 years ago)
From
Myungshin Im at Seoul Nat U <mim@astro.snu.ac.kr>
Myungshin Im, Yiseul Jeon (CEOU/SNU), Mansur Ibrahimov (UBAI)
On 2011 April 12 22:49 (UT), we observed GRB 110328A using
SNUCAM on the 1.5m telescope at the Maidanak observatory,
Uzbekistan. The optical counterpart is clearly detected
at S/N > 10 in the R-band image, without exhibiting no strong
flux variability.
We thanks the staffs of the Maidanak observatory for carrying out
this observation.
GCN Circular 11933
Subject
GRB 110328A / Swift J164449.3+573451: WISE quiescent source upper limit
Date
2011-04-14T16:26:40Z (14 years ago)
From
Douglas Hoffman at IPAC/Caltech <dhoffman@ipac.caltech.edu>
D. I. Hoffman (IPAC/Caltech), J. S. Bloom (UC Berkeley), R. M. Cutri (IPAC/Caltech),
D. Perley (UC Berkeley), B. Cenko (UC Berkeley), N. Tanvir (Leicester), and A. Levan (Leicester) report:
The Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010 AJ 140, 1868)
scanned the location of GRB 110328A / Swift J164449.3+573451 from January 25, 2010
to January 28, 2010 in the four WISE bands. The coadded frames, each consisting
of 39 individual images, do not reveal a detection of the quiescent source.
Using a 15 arcsec aperture, we obtained the following 3-sigma upper limit estimates:
Band U. Limit (mag) U. Limit (uJy)
W1 (3.4 um) > 18.0 > 19
W2 (4.6 um) > 16.2 > 57
W3 (12 um) > 12.8 > 240
W4 (24 um) > 9.55 > 1270
WISE is a joint project of the University of California, Los Angeles,
and the Jet Propulsion Laboratory/California Institute of Technology,
funded by the National Aeronautics and Space Administration.
[GCN OPS NOTE(14apr11): Per author's request, the greek-font mu characters
were replaced with 'u's.]
GCN Circular 11917
Subject
GRB 110328A / Swift J164449.3+573451: R-band Monitoring
Date
2011-04-11T08:32:16Z (14 years ago)
From
Myungshin Im at Seoul Nat U <mim@astro.snu.ac.kr>
Myungshin Im, Yiseul Jeon (CEOU/SNU), Hyun-Il Sung (KASI),
Yuji Urata (NCU), and Kuiyun Huang (ASIAA) on behalf of EAFON
We are conducting R-band monitoring of GRB 110328A, using
the 1.0m telescope at the Mt. Lemmon (LOAO), AZ, USA.
In the images taken during April 4, 5, and 7 (UT), we clearly
identify the optical counterpart (Cenko et al. GCN 11827; Leloudas et al.
GCN 11830; Volnova et al. GCN 11837; Im et al. GCN 11839; Yoshida et al.
GCN 11882). The derived R-band magnitudes range from 22.3 to 22.6 mag,
but uncertainties in the current photometry make it difficult to assess
its variability at < ~0.3 mag.
Further analysis of the data, as well as the continued monitoring
of the object is planned.
We thank the LOAO operator, I. Baek and J. Yoon for their assistance
of these observations.
GCN Circular 11915
Subject
GRB 110328A / Swift J164449.3+573451: MASTER pre, prompt and follow-up observations
Date
2011-04-10T15:58:42Z (14 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <gcncirc@observ.inetcomm.ru>
E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, N.Tyurina,
N.Shatskiy, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov,
D.Zimnukhov, M. Kornilov, A.Kuznetsov, D.Zimnukhov, M. Kornilov,
D.Gareeva, A.Sankovich
Sternberg Astronomical Institute, Moscow State University
V.Yurkov, Yu.Sergienko, D.Varda, I.Kudelina
Blagoveschensk Educational State University, Blagoveschensk
A. Tlatov, A.V. Parhomenko, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory
V.Krushinski, I.Zalozhnich, T.Kopytova, A. Popov
Ural State University, Kourovka
K.Ivanov, S.Yazev, N.M.Budnev, E.Konstantinov, O.Gres, O.Chuvalaev,
V.A.Poleshchuk
Irkutsk State University
MASTER II robotic telescope (MASTER-Net: http://87.226.242.22/all-new.php)
located in Tunka(Siberia) was pointed to the GRB 110328A (Cummings et
al., GCN Circ 11823) 23 sec s after
notice time and 1257 sec after GRB time at 2011-03-28 13:18:42.285 UT. On
our first (180s exposure) set we haven`t found optical transient within
SWIFT error-box. The 3-sigma upper limit has been about 17.7mag
The second Swift trigger (Number 450161, 11/03/28, 13:40:41.20) has
been received during this follow-up observations. So we have synhronous
prompt observatios of the GRB 110328A / Swift J164449.3+573451:
Time start exp mlim T_mean
(s) unfiltered (if needed)
2011-03-28 13:38:20 180 19.1
2011-03-28 13:38:21 180 19.1
2011-03-28 13:41:56 180 18.9
2011-03-28 13:41:56 180 18.9
2011-03-28 13:45:41 180 18.5
2011-03-28 13:45:41 180 18.7
2011-03-28 13:49:17 180 18.2
2011-03-28 13:49:17 180 18.2
....................................
2011-03-28 13:38:20 2520 20.8 (T_mean = 2011-03-28 14:13:54.50)
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru)
located in MASTER-Amur was pointed to the GRB 110328A 16 sec s after
notice time and 365 sec after GRB time at 2011-03-29 18:32:30.586 UT. On
our first (70s exposure) set we haven`t found optical transient within
SWIFT error-box.
The beginning results:
Time start exp mlim T_mean
(s) unfiltered (if needed)
2011-03-29 18:32:30 70 19.1
2011-03-29 18:33:51 90 19.3
2011-03-29 18:35:32 110 19.5
2011-03-29 18:37:32 130 19.7
2011-03-29 18:39:52 160 19.8
2011-03-29 18:42:42 180 19.6
2011-03-29 18:46:04 180 19.5
2011-03-29 18:49:26 180 19.6
2011-03-29 18:52:48 180 19.6
....................................
2011-03-29 18:37:32 3530 22.0 2011-03-29 19:10:15
MASTER II robotic telescope located in Kislovodsk was pointed
to the GRB 110328A 28 sec s after
notice time and 105 sec after GRB time at 2011-03-29 19:59:30.376 UT. On
our first (20s exposure) set we haven`t found optical transient within
SWIFT error-box. The 3-sigma upper limit has been about 18.8 mag
Time start exp mlim T_mean
(s) unfiltered (if needed)
2011-03-29 19:59:30 20 18.5
2011-03-29 20:00:18 30 19.1
2011-03-29 20:19:48 180 19.9
2011-03-29 20:23:17 180 19.9
2011-03-29 20:26:42 180 19.9
2011-03-29 20:30:07 180 19.8
2011-03-29 20:33:32 180 19.9
2011-03-29 20:36:58 180 19.9
2011-03-29 20:40:24 180 19.9
2011-03-29 20:43:52 180 19.8
2011-03-29 20:47:25 180 19.9
2011-03-29 20:50:50 180 19.9
2011-03-29 20:54:15 180 19.9
2011-03-29 20:57:40 180 19.9
2011-03-29 21:01:06 180 19.9
2011-03-29 21:04:31 180 20.0
....................................
2011-03-29 20:19:48 10800 23.0 (T_mean=2011-03-29 22:54:51)
There are 2 preburst images 1 month before the GRB 110328A / Swift
J164449.3+573451 tregger in MASTER Tunka DataBase.
Time start exp mlim T_mean
UT (s) unfiltered (if needed)
2011-02-27 21:31:05 180 19.6
2011-02-27 22:21:49 180 20.3
There is no OT on our images.
Our unfiltered magnitude is determined as m = 0.8R+0.2B.
The photometry of the coadded images are based on the USNO B1.0 star
1475-0312998 (16 45 07.13 +57 36 03.4) assuming R=19.35, B=21.3 .
Our results in agreement with Swift UVOT White limit (Breeveld et al., GCN
Circ 11910).
The summary diagramm of our observations is available at
http://observ.pereplet.ru/images/GRB110328A/limit.gif
The message may be cited.
GCN Circular 11913
Subject
GRB 110328A / Swift J164449.3+573451: optical observations
Date
2011-04-09T12:36:58Z (14 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
V. Rumyantsev (CrAO), A. Volnova (SAI MSU), E. Klunko (ISTP), A. Pozanenko
(IKI), on behalf of larger GRB follow up collaboration report:
We observed the 110328A / Swift J164449.3+573451 (Cummings et al., GCN
11823) with Shajn telescope of CrAO observatory and AZT-33IK telescope of
Sayan observatory (Mondy) . Several series were taken on March 31, April 1
and 3. In each epoch of our observations we clearly observed the optical
counterpart (Cenko et al., GCN 11827, Leloudas et al., GCN 11830, Volnova et
al., GCN 11837). The photometry is based on the USNO B1.0 star 1476-0321081
(16 45 07.13 +57 36 03.4) assuming R=19.38. The first column represents the
time since first Swift trigger (Cummings et al., GCN 11823).
#, T0+ Filter Exposure OT telescope
4. 3.28240 R 10230 22.44 +/-0.14 AZT-33IK
5. 4.35111 R 69x60 22.45 +/-0.12 ZTSh
6. 6.44459 R 96x60 22.68 +/-0.05 ZTSh
Some details of our observations can be found at
http://grb.rssi.ru/GRB110328A/
[GCN OPS NOTE(30apr11): Per author's request, Elunko was changed to Klunko.]
GCN Circular 11911
Subject
GRB 110328A / Swift J164449.3+573451: VLBA Observations
Date
2011-04-08T19:41:35Z (14 years ago)
From
Edo Berger at Harvard <eberger@cfa.harvard.edu>
Andreas Brunthaler (MPIfR), Alicia Soderberg (Harvard), Michael Rupen
(NRAO), Ashley Zauderer, Edo Berger (Harvard), Dale Frail (NRAO), and
Michael Bietenholz (York U.) report:
"We observed the variable radio counterpart (GCNs 11836, 11848) of GRB
110328A / Swift J164449.3+573451 (GCNs 11823, 11824) with the Very Long
Baseline Array (VLBA) and Effelsberg Radio Telescope for 7 hours beginning
on April 2 at 6:00 UT. Observations at both telescopes were carried out
at a central frequency of 8.46 GHz. Based on a preliminary analysis of
the VLBA baselines alone, we report a significant detection (SNR=29) of
the source at position:
RA: 16 44 49.9313
DEC: 57 34 59.6895
with a conservative error estimate of 0.5 mas dominated by the positional
uncertainty of the phase calibrator, J1638+5720. This is the most precise
position available for the transient. It is coincident with the measured
positions for the variable radio, NIR, and X-ray counterparts (GCNs 11836,
11848, 11853, 11854, 11886) and the host galaxy nucleus (GCN 11881). The
source is not resolved in our VLBA observation; this constrains the size
to be smaller than that of the beam: 1.9 x 0.7 mas at a position angle of
18 deg. Further VLBI observations are planned to set limits on the proper
motion and source structure.
We thank the NRAO and Effelsberg scheduling staff for enabling these
rapid response observations. "
GCN Circular 11910
Subject
GRB 110328A/Swift J164449.3+573451 UVOT Upper Limits
Date
2011-04-08T18:38:46Z (14 years ago)
From
Alice Breeveld at MSSL-UCL <aab@mssl.ucl.ac.uk>
A. A. Breeveld (MSSL/UCL), M. M. Chester (PSU), S. T. Holland
(CRESST/USRA/GSFC) , F.E. Marshall (NASA/GSFC) and J. R. Cummings
(NASA/UMBC) report on behalf of the Swift/UVOT team:
The Swift/UVOT has been observing the field of GRB110328A/Swift
J164449.3+573451 since 1483s after the initial trigger (Cummings et
al., GCN Circ. 11823). We have found no source in any filter at the
position of the afterglow (Cenko et al., GCN Circ. 11827), using
individual exposures or summed exposures.
Summing up all the data in each filter, beginning with the first BAT
trigger on 28th March through 7th April, we have obtained the
following 3-sigma upper limits using the UVOT photometric system
(Poole et al. 2008, MNRAS, 383, 627):
Filter Exp(s) Mag
---------------------------------------------------------------------
white 29579 >23.9
v 2541 >21.1
b 1493 >21.5
u 58559 >23.5
w1 59906 >23.4
m2 29000 >23.0
w2 15547 >22.9
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 11891
Subject
GRB 110328A/Swift J164449.3+573451: BAT recent rate increase and pre-outburst,light curve
Date
2011-04-06T21:40:50Z (15 years ago)
From
Hans Krimm at NASA-GSFC <hans.krimm@nasa.gov>
H. A. Krimm (CRESST/GSFC/USRA) and S. D. Barthelmy (GSFC) report
on behalf of the Swift/BAT team:
We report on the time history of the discovery outburst of Swift
J164449.3+573451 and archival searches for past emission.
The current outburst started on 2011-Mar-25 (MJD 55645) with a detection
of 0.0059 � 0.0016 ct/s/cm2 (~25 mCrab). BAT first triggered on the
source on 2011-Mar-28 (Cummings et al, GCN 11823). There were numerous
flares as high as 220 mCrab over the next three days, then the count
rate dropped to an average level of 0.0009 ct/s/cm2 and the flares
stopped. For the past three days the rate shown a slight increase to
0.0015 � 0.0005 ct/s/cm2 (~7 mCrab) on 2001-Apr-05, although no flares
above 40 mCrab have been seen. For a detailed time history of the early
part of the outburst see Sakamoto et al, GCN 11842.
The Swift/BAT transient monitor archival data were searched back to
February 12, 2005 for previous detections of Swift J164449.3+573451.
These searches were made on three different time scales with the
following results:
On a 16-day timescale (the longest available), we set a 3-sigma upper
limit of 0.0011 ct/s/cm2 (~5 mCrab).
On a 1-day timescale, there were three isolated days before the outburst
when the source was found at above the 3-sigma level:
2009-Mar-31 (MJD 54921) 0.0036 � 0.0011 ct/s/cm2
2009-Sep-14 (MJD 55088) 0.0036 � 0.0010 ct/s/cm2
2011-Mar-14 (MJD 55634) 0.0035 � 0.0011 ct/s/cm2
All three episodes correspond to approximately 15 mCrab. However, given
1866 independent days examined, three 3-sigma points is consistent with
statistics.
For all other 1-day images, we can set a 3-sigma upper limit. This
limit varies depending on the exposure of the source, with 90% of the
daily limits within the range of 0.0015 ct/s/cm2 to 0.010 ct/s/cm2.
On shorter time scales, we are unable to set a limit below the 6-sigma
level for a previously unknown source. Before March 2011 there was no
interval when Swift J164449.3+573451 was seen above 6-sigma on any
time scale from 64 seconds to a full Swift pointing (nominally 1200
seconds). Corresponding count rate limits cannot be specified since
they depend critically on the time scale and location of the source in
the BAT field of view.
GCN Circular 11882
Subject
GRB 110328A / Swift J164449.3+573451: Keck LRIS R-band photometry
Date
2011-04-05T06:24:09Z (15 years ago)
From
Michitoshi Yoshida at HASC,Hiroshima U <yoshidam@hiroshima-u.ac.jp>
M. Yoshida (HASC, Hiroshima Univ.), M. Yagi and Y. Komiyama (NAOJ)
We performed R band imaging observation of the optical counterpart
of GRB 110328A / Swift J164449.3+573451 (Cummings et al. GCN 11823)
with LRIS attached to Keck-I telescope. The observation was made at
2011-04-01 15:22 UT. We obtained two 30 sec exposure frames and
clearly detected the source (Cenko et al. GCN 11827; Leloudas et al.
GCN 11830; Volnova et al. GCN 11837; Im et al. GCN 11839) in both
frames. Using GSC2.3: N4JF005367 and N4JF005228 (F-magnitude = 15.90
and 17.13, respectively) for flux calibration, we obtained R-band AB
magnitude of 22.61 +- 0.09. Taking into account photometric error of
the GSC catalog, we consider that this result is consistent with
the HST photometry done on 2011-04-04 (Fruchter et al. GCN 11881)
and the OT shows no significant variation between our observation
and the HST observation.
GCN Circular 11881
Subject
GRB 110328A / Swift J164449.3+573451, HST Observations
Date
2011-04-04T18:46:17Z (15 years ago)
From
Andrew S. Fruchter at STScI <fruchter@stsci.edu>
Andrew Fruchter, Kuntal Misra, John Graham (STScI), Andrew Levan (U. Warwick), Nial Tanvir (U. Leicester) and Joshua Bloom (UC Berkeley) report for a larger collaboration:
We have observed the field of GRB 110328A / Swift J164449.3+573451 using the WFC3 on the Hubble Space Telescope. We observed in both the near-IR (F160W) and optical (F606W). The observations were performed between 03:00 and 04:00 UT on 4 April 2011.
We obtained four dithered exposures of 250s each in F160W. The combined drizzled image has a FWHM of 0.16 arcsec. At the location of the transient we find a nearly pointlike source. Using the two stars in the field which are in both the UCAC3 and 2MASS catalogs for astrometric alignment, we find that the position of this source agrees with that of EVLA (GCN 11854) to within our estimated astrometric error of 0.07 arcsec (340 pc at the distance of the source).
In the optical F606W filter we obtained three dithered exposures of 420s each. This combined optical image shows a clearly resolved but compact host galaxy. The nucleus of the galaxy is coincident with the position of the IR source.
Using an aperture with a radius of of one arcsecond, we obtain AB magnitudes of 20.75 +/- 0.04 (F160W) and 22.82 +/- 0.02 (F606W) for the central source plus surrounding host galaxy.
The astrometric agreement between the HST images and the radio, as well as the observed near-IR variability (GCN 11853) suggest that the transient is associated with the nucleus of this galaxy. Future HST observations should be able to place good constraints on the nuclear variability in both the optical and near-IR, and thus perhaps on the interesting proposal that we are seeing a mini-blazar powered by a tidal disruption event (GCN 11847).
GCN Circular 11880
Subject
GRB 110328A / Swift J164449.3+573451: millimeter detection at PdBI
Date
2011-04-04T18:14:26Z (15 years ago)
Edited On
2024-11-18T09:46:59Z (a year ago)
From
Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov>
A. J. Castro-Tirado (IAA-CSIC), M. Bremer, J.-M. Winters and P. Cox
(IRAM), J. Gorosabel, S. Guziy (IAA-CSIC), J. M. Castro Cerón (ESA/ESAC)
and A. de Ugarte Postigo (DARK/NBI), on behalf of a larger collaboration,
report:
"Following the detection by Swift of GRB 110328A / Swift J164449.3+573451
(Sbarufatti et al. GCNC 11798), millimeter observations were conducted on
Mar 31 at the Plateau de Bure Interferometer. Consistent with the EVLA
radio counterpart (Zauderer et al. GCNC 11836) we clearly detect a source
at 3-mm with a flux density of ~20 mJy (200 sigma), confirming a 30%
increase in flux density with respect to a previous mm observation on Mar
30
(Zauderer et al. GCN 11841). Further observations are scheduled. We
acknowledge the Bure staff for its excellent support."
GCN Circular 11874
Subject
GRB 110328A / Swift J164449.3+573451: Keck/DEIMOS Optical Spectroscopy
Date
2011-04-04T04:27:16Z (15 years ago)
From
S. Bradley Cenko at Caltech <cenko@srl.caltech.edu>
S. B. Cenko, D. A. Perley, J. S. Bloom (UC Berkeley), K. Hurley (SSL), J.
X. Prochaska, J. Brodie, N. Singh, J. Arnold, A. Romanowsky, J. C. Forbes
(UCO/Lick), and D. Forbes (Swinburne) report on behalf of a larger
collaboration:
We have obtained medium-resolution optical spectroscopy of the optical
counterpart (Cenko et al., GCN 11827) of the high-energy transient GRB
110328A / Swift J164449.3+573451 (Cummings et al., GCN 11823) with the
DEIMOS spectrograph mounted on the Keck II telescope. Observations began
at 14:55 UT on 2011 Mar 31 and cover the wavelength range from 4500-9500
A.
We identify strong nebular emission features associated with [O II], [O
III], H-beta, H-alpha, [N II], and [S II] at a redshift consistent with
that reported by Levan et al. (GCN 11833) and Thoene et al. (GCN 11834).
Using a preliminary flux calibration, we find that the Balmer decrement
(H-alpha / H-beta) is only marginally larger than the value expected for
Case B recombination (consistent at the 2 sigma level). This would
suggest that the observed red colors of the optical / NIR counterpart
(e.g., Morgan et al., GCN 11845; Levan et al., GCN 11846) are either due
to 1) an intrinsically red transient source, or 2) dust localized to the
source of the transient emission (which does not affect the bulk of the
ongoing star formation in the galaxy).
Constructing a diagnostic diagram (e.g., Baldwin, Phillips, and Terlevich
1981, PASP, 93, 5) based on the observed ratio of the narrow emission
lines, we find the source falls within the locus of star-forming
galaxies, and thus does not appear to exhibit any evidence for past
nuclear activity. A plot of the diagnostic diagram of the host, showing
the empirical dividing line between star-forming galaxies and AGNs from
Kauffmann et al (2003, MNRAS, 341, 33- solid line), the theoretical
dividing lines from Kewley and Dopita (2002, ApJS, 142, 35 - dashed
lines), and the empirical dividing lines from Ho, Filippenko, and Sargent
(1997, ApJS, 112, 315), along with analogous measurements from the MPA-JHU
value-added SDSS database, can be found at:
http://astro.berkeley.edu/~cenko/public/grb/GRB110328A/bpt.png
GCN Circular 11872
Subject
GRB 110328A/Swift J164449.3+573451: SARA-N detection
Date
2011-04-03T03:37:13Z (15 years ago)
From
Adria C. Updike at Clemson U <aupdike@clemson.edu>
William C. Keel, Erin Darnell (U Alabama), Adria C. Updike (NASA/GSFC), D.
Alexander Kann (TLS Tautenburg), and Dieter H. Hartmann (Clemson
University) report:
We observed the field of GRB 110328A/Swift J164449.3+573451 (Cummings et
al., GCN 11823) on April 1 at 11:50 UT (3.96 days after the trigger) for
20 minutes in the R band with the SARA North telescope at KPNO. At the
location of the optical counterpart (Cenko et al., GCN 11827; Volnova et
al., GCN 11837) we marginally detect the transient at R = 21.7 +/- 0.3 as
compared to the USNO B1.0 catalog and the comparison star given by
Leloudas et al. (GCN 11844), in good agreement with the earlier
observations of Kelemen et al. (GCN 11867).
This GCN resulted from a collaboration initiated by the BAUTforum.
This message may be cited.
GCN Circular 11867
Subject
GRB 110328A: Konkoly observations.
Date
2011-04-02T14:58:11Z (15 years ago)
From
Janos Kelemen at Konkoly Obs/Hungary <kelemen@konkoly.hu>
J. Kelemen, K. Sarneczky (Konkoly Obs.)
on behalf of the GRB OT observing program at the Konkoly Observatory.
During the period 30/03/2011 - 31/03/2011 we observed the field of GRB 110328A
/ Swift J164449.3+573451 detected by Swift (Cummings et al., GCN 11823;
Barthelmy et al., GCN 11824) with a 60/90 cm Schmidt telescope located at the
Mountain Station of the Konkoly Observatory. For the photometry of the OT
reported by Cenko et al., (GCN 11827); G. Leloudas et. al., (GCN11830) nearby
stars of the UCAC3 catalogue was used.
Summary of our results:
J.D. magnitude Band
2455650.58459 21.8 +/- 0.2 R
2455651.56924 21.5 +/- 0.2 R
2455652.41122 21.6 +/- 0.2 R
GCN Circular 11862
Subject
GRB110328A/Swift J164449.3+573451: Fermi LAT Observations
Date
2011-04-02T06:06:13Z (15 years ago)
From
Nicola Omodei at Stanford U. <nicola.omodei@slac.stanford.edu>
N. Omodei (Stanford), E. Troja (NASA/GSFC/ORAU), R. Corbet (CRESST/UMBC/GSFC), J. S. Perkins (CRESST/UMBC/GSFC), J. L. Racusin (NASA/GSFC), J. E. McEnery (NASA/GSFC) on behalf of the Fermi Large Area Telescope collaboration.
At the time of the first Swift trigger (Cummings et al., GCN 11823) the Fermi spacecraft was operating in pointing mode observing the region of Cyg X-3.
The ToO was terminated at 15:13 UT (2.25 hours on target after the initial Swift trigger) and the Fermi spacecraft continued in normal rocking mode.
During the time of Cyg X-3 pointed mode observation the GRB110328A/Swift J164449.3+573451 was at 47 degrees from the LAT boresight.
We report here the 95% confidence upper limits on the flux for different exposures spanning the time period of the bright activity of the source.
Upper limits (in units of ph/cm^2/s) have been computed between 100 MeV and 10 GeV using the standard likelihood tool, publicly available at the Fermi Science Support Center Web site (http://fermi.gsfc.nasa.gov/ssc/data/analysis/software/).
The model assumed in the fit for the source is a power law. The two sets of ULs were derived by fixing the spectral index to 2 and 2.5, respectively.
We report upper limits on day-long time scales:
| Date | Flux (Index = 2) | Flux (Index = 2.5) |
| 2011-03-26 | <3.3e-07 | <6.0e-07 |
| 2011-03-27 | <2.9e-07 | <5.2e-07 |
| 2011-03-28 | <1.8e-07 | <2.8e-07 |
| 2011-03-29 | <1.7e-07 | <2.6e-07 |
| 2011-03-30 | <2.3e-07 | <3.9e-07 |
| 2011-03-31 | <2.2e-07 | <3.4e-07 |
We also searched over a shorter time window around the time of the first three Swift triggers (during the hour following each trigger).
For the last Swift trigger (Sakamoto et al., GCN 11842) the source was never in the LAT field of view, therefore we omit it in the following table:
| Date | Flux (Index = 2) | Flux (Index = 2.5) |
| 2011-03-28 12:57:45.2 | <1.5e-06 | <9.1e-07 |
| 2011-03-28 13:40:41.2 | <3.0e-06 | <4.7e-06 |
| 2011-03-29 18:26:25.1 | <2.1e-06 | <2.6e-06 |
No significant gamma-ray emission is seen from the direction of GRB110328A/Swift J164449.3+573451 in the full 27 months of Fermi LAT data.
We report an upper limit of 1.7e-8 ph/cm^2/s (from 100 MeV to 10 GeV) and an upper limit of 1.5e-10 ph/cm^2/s (from 1 GeV to 300 GeV).
Knowing that this object could be highly variable, we investigated possible emission on timescales of 5 and 2 days over the lifetime of the Fermi mission.
No significant emission was seen in any of the time bins in this light curve.
We also report that no significant sources are detected within three degrees from the position of GRB110328A/Swift J164449.3+573451 are present integrating the data over 27 months.
The Fermi LAT point of contact for this source is Nicola Omodei (nicola.omodei@slac.stanford.edu).
The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV.
It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular 11856
Subject
GRB 110328A / Swift J164449.3+573451: KASINICS NIR Observation
Date
2011-04-01T13:04:13Z (15 years ago)
From
Myungshin Im at Seoul Nat U <mim@astro.snu.ac.kr>
Myungshin Im, Won-Kee Park (CEOU/SNU), Hyun-Il Sung,
Yeong-Beom Jeon (KASI), Yuji Urata (NCU), and Kuiyun Huang (ASIAA)
on behalf of EAFON
We continued NIR observation of GRB 110328A / Swift J164449.3+573451
using the KASINICS on the 1.8m telescope at Mt. Bohyun Observatory
in Korea.
The observation started at 2011 March 31, 14:45:20 UT, and we
obtained a series of images in H and K.
The NIR counterpart is clearly detected in both bands,
with the K-band magnitude at 17.29 +- 0.03.
Comparison with the K-band magnitude of the same object from
the previous night data (Im et al. GCN 11850) shows the dimming
of the object by 0.43 mag over one day.
The H-band data also show variability, confirming the variability
of the source reported earlier (Leval et al. GCN 11854)
More NIR imaging is planned.
GCN Circular 11855
Subject
GRB 110328A / Swift J164449.3+57345: Correction to GCN 11850
Date
2011-04-01T12:57:45Z (15 years ago)
From
Myungshin Im at Seoul Nat U <mim@astro.snu.ac.kr>
Myungshin Im, Won-Kee Park (CEOU/SNU), Hyun-Il Sung,
Yeong-Beom Jeon (KASI), Yuji Urata (NCU), and Kuiyun Huang (ASIAA)
on behalf of EAFON
It was reported earlier in Im et al. (GCN 11850) that
KASINICS K-band imaging started at 2011 March 31, 07:04 UT.
The starting time needs to be corrected to March 30, 14:43 UT,
which is only 1:43 behind the observation time of Levan et al.
(GCN 11846). Considering the proximity of the observation times,
the no detection in the variability (GCN 11850) is not surprising.
GCN Circular 11854
Subject
GRB 110328A / Swift J164449.3+573451: Radio-optical/NIR Astrometry
Date
2011-03-31T18:47:00Z (15 years ago)
From
Edo Berger at Harvard <eberger@cfa.harvard.edu>
E. Berger (Harvard), A. Levan (U. Warwick), N. R. Tanvir
(U. Leicester), A. Zauderer, A. M. Soderberg (Harvard), and
D. A. Frail (NRAO) report:
"We performed absolute and relative astrometry on radio and optical
images of GRB 110328A / Swift J164449.3+573451 (GCNs 11823, 11824) in
an atempt to locate the radio transient (GCNs 11836, 11848) relative
to the quiescent optical source at z=0.35 (GCNs 11827, 11830, 11833,
11834). We used EVLA observations at a mean frequency of 5.8 GHz
(GCNs 11836, 11848), a Gemini-N/GMOS r-band image, and a UKIRT/WFCAM
J-band image (GCN 11846).
The Gemini and UKIRT images were astrometrically aligned relative to
2MASS using 20 and 55 objects in common, respectively, leading to an
rms scatter of 0.14" and 0.10" in each coordinate, respectively. For
the EVLA image we used the native astrometric solution relative to the
ICRS. The accuracy of the astrometry is verified by imaging and
measuring the position of the phase calibrator, which agrees with the
ICRS position to better than 0.4 mas. We note that the 2MASS
point-source-catalog positions used to align the Gemini and UKIRT
images are reconstructed onto the ICRS.
We find the following coordinates for the optical source in the Gemini
image (J2000):
RA = 16:44:49.939
DEC = +57:34:59.64
with an uncertainty of 0.14" in each coordinate, dominated by the
astrometric solution uncertainty.
The position of the faint NIR counterpart in the UKIRT image is:
RA = 16:44:49.958
DEC = +57:35:00.00
with an uncertainty of about 0.3" in the source centroid, and an
additional 0.1" due to astrometric solution uncertainty.
Finally, the ICRS position of the radio transient is:
RA = 16:44:49.925
DEC = +57:34:59.68
with negligible centroid uncertainty of about 0.01".
The relative offset between the radio and optical positions is
therefore 0.12+/-0.20", or about 0.6+/-1.0 kpc (at z=0.35). The
offset relative to the NIR position is 0.42+/-0.42". Thus, the radio
transient position is consistent with arising in the nucleus of the
host galaxy (GCN 11847).
We find an additional common source between the radio, optical, and
NIR images with the following positions:
optical:
RA = 16:44:48.047
DEC = +57:32:16.83
near-IR:
RA = 16:44:48.093
DEC = +57:32:17.03
radio:
RA = 16:44:48.139
DEC = +57:32:16.74
This source is a galaxy with extended structure in the optical/NIR
images, but it is unresolved in the radio. We therefore associate the
radio position with the nucleus of the galaxy (positions given above).
The resulting positional offsets are 0.75+/-0.20" (radio-to-optical)
and 0.47+/-0.15" (radio-to-NIR). We caution that the error bars do
not include a systematic uncertainty in centroiding on the galaxy
nucleus (~0.1"), and do not account for potential distortions due to
the location of the object near the edge of the Gemini image. Taken
at face value, the offset between these positions potentially reflects
a relative shift between the optical/NIR and radio astrometric
systems. If applied to the radio counterpart of GRB 110328A / Swift
J164449.3+573451, this shift would lead to a significant offset
(~3-sigma confidence level) between the radio position and the center
of the host galaxy.
To conclude, absolute astrometry indicates that the radio transient is
consistent with arising in the nucleus of the host galaxy (0.6+/-1.0
kpc); the relative radio-optical/NIR positions of an additional common
source allow for an offset of up to ~3 kpc. Additional wide-field
(~10') deep NIR imaging may provide a larger number of common objects
with the EVLA images, thereby impoving the relative astrometric
solution.
GCN Circular 11853
Subject
GRB 110328A / Swift J164449.3+573451: Infrared transient
Date
2011-03-31T18:19:39Z (15 years ago)
From
Andrew Levan at U.of Leicester <A.J.Levan@warwick.ac.uk>
A.J. Levan (U. Warwick), D. Perley (U.C. Berkeley), N.R. Tanvir (U.
Leicester), J. Bloom, S.B. Cenko (U.C. Berkeley) report for a larger
collaboration:
"We re-observed the localization of GRB 110328A with Gemini-N/NIRI
on 31 March 2011. Observations were taken in the K-band, and began
at 13:15UT, roughly 24 hours after our previous observation (Levan
et al. GCN 11846). We find that the IR source, coincident
with the X-ray (Osborne et al. GCN 11826) and radio (Zauderer et
al. GCN 11848) localisations has faded by 0.25 +/- 0.03 magnitudes
over this time frame. Hence we conclude that the IR light does
contain a substantial contribution from transient emission. We note
that the apparent brightening of the source in a few hours between the
observations of Morgan et al. (GCN 11845) and Gemini (GCN 11846),
coupled with the fading over the subsequent 24 hours, suggests that
the behaviour of the system is complex, and as in the X-ray, is not
simply modelled by either a rising, or decaying lightcurve.
The location of the source is consistent with the galaxy
observed in the optical with a measured redshift z=0.351,
(Levan et al. GCN 11833, Thoene et al. GCN 11834) hence
increasing the confidence in a true association.
Further observations are planned."
GCN Circular 11852
Subject
GRB 110328A / Swift J164449.3+573451: Mondy optical observations
Date
2011-03-31T16:37:26Z (15 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
A. Pozanenko (IKI), A. Volnova (SAI MSU), E. Klunko (ISTP) on behalf of
larger GRB follow up collaboration report:
We continue observation (Volnova et al. GCN 11837) of the field of GRB
110328A / Swift J164449.3+573451 (Cummings et al. GCN 11823) with AZT-33IK
telescope of Sayan observatory (Mondy). Several series of images in R- band
were taken on March 28 an 29. In the first epoch we clearly detect the
optical counterpart (Cenko et al. GCN 11827, Leloudas et al. GCN 11830),
while we do not detect it in the second epoch. The photometry below is based
on the USNO-A2.0 star 1425-08596694 assuming R=16.6. The first column
represents the time since first Swift trigger (Cummings et al. GCN 11823).
T0+ Filter, Exposure, OT mag., UpperLimit (3 sigma)
(mid, d) (s)
0.08944 R 6420 21.50 +/- 0.11 23.7
1.25258 R 870 n/d 22.9
Based on the above photometry we tentatively suggest the variability of the
optical counterpart between the two epochs. However the more precise
calibration of the field stars are necessary to make a definite conclusion
about variability.
[GCN OPS NOTE(30apr11): Per author's request, Elunko was changed to Klunko.]
GCN Circular 11850
Subject
GRB 110328A / Swift J164449.3+573451: KASINICS K-band Observation
Date
2011-03-31T14:14:56Z (15 years ago)
From
Myungshin Im at Seoul Nat U <mim@astro.snu.ac.kr>
Myungshin Im, Won-Kee Park (CEOU/SNU), Hyun-Il Sung,
Yeong-Beom Jeon (KASI), Yuji Urata (NCU), and Kuiyun Huang (ASIAA)
on behalf of EAFON
Starting at 2011 March 31,07:04 UT, we performed K-band observation
of the field of GRB 110328A / Swift J164449.3+573451
(Cummings et al. GCN 11823) using the KASINICS instrument on
the 1.8m telescope at Mt. Bohyun Observatory in Korea.
We clearly detect the NIR counterpart in K (Morgan et al. 11845;
Levan et al. GCN 11846). Using 2MASS stars in the vicinity,
we obtain K ~ 16.86 +- 0.02 mag (statistical error only)
for the NIR counterpart.
The brightness of the object is consistent with the value reported
in Levan et al. (GCN 11846), implying no significant brightening over
about 18 hrs time span.
Further NIR observations are being carried out.
GCN Circular 11849
Subject
GRB 110328A / Swift J164449.3+573451
Date
2011-03-31T11:03:35Z (15 years ago)
From
Guy Pooley at MRAO, Cambridge, UK <ggp1@cam.ac.uk>
Guy Pooley (University of Cambridge) reports:
The unusual source GRB 110328A / Swift J164449.3+573451 (GCNs 11823,
11824) was observed with the AMI large array at MRAO, Cambridge (UK) on
2011 Mar 31 over a frequency band from 13.5 to 17.25 GHz.
The first observation ran from 02h07m to 08h06m UT; the weather
conditions were poor. This observation started 2d13h after the first BAT
trigger. The source reported in GCNs 11836, 11848 was detected with a
mean flux density of 2.95 +- 0.30 mJy.
Analysis of the data in 4 equal time divisions shows a steady increase
(2.25, 2.48, 2.56, 3.46 mJy), and a spectral analysis shows a rising
spectrum.
A second observation from 09h01m to 10h17m UT gives a mean flux density
of 2.75 +- 0.30 mJy and also suggests a rising spectrum.
This message is quotable in publications.
GCN Circular 11848
Subject
GRB 110328A / Swift J164449.3+573451: EVLA observations of a brightening radio source
Date
2011-03-30T23:07:49Z (15 years ago)
From
Edo Berger at Harvard <eberger@cfa.harvard.edu>
Ashley Zauderer, Edo Berger (Harvard), Dale A. Frail (NRAO) and Alicia
Soderberg
(Harvard) report:
"We re-observed the peculiar Swift event GRB110328A / Swift J164449.3+573451
(GCNs 11823, 11824) with the EVLA on March 30.49 UT. At the two
frequenciescentered at 4.94 and 6.69 GHz we find that the
previously-detected radio
source (GCN 11836) has significantly brightened (~10-sigma confidence
level).
This provides the first clear evidence connecting the quiescent optical
source at z=0.35 (GCNs 11827, 11830, 11833, 11834), which is positionally
coincident with the brightening radio source, and the transient
X-ray/gamma-ray source (which is localized to only 1.7" radius accuracy; GCN
11826)."
GCN Circular 11847
Subject
GRB 110328A / Swift J164449.3+573451: X-ray analysis and a mini-blazar analogy
Date
2011-03-30T23:02:09Z (15 years ago)
From
Josh Bloom at UC Berkeley <jbloom@astron.berkeley.edu>
J. S. Bloom, N. R. Butler, S. B. Cenko, D. A. Perley (UC Berkeley) report:
"We perform a time-resolved X-ray spectral analysis of the Swit XRT data for GRB1103028A / Swift J164449.3+573451 (Cummings et al., GCN 11823; Kennea et al., ATel 3242). As reported by Kennea et al. (ATel 3250), the X-ray hardness correlates with the X-ray flux. We find that, in the low-flux state, the spectrum is well-fit by an aborbed powerlaw; while a blackbody model is preferred for the high-flux state.
For a reference time t0 of 2011/03/28 12:57:45.2 UT, the (PC mode) spectrum in the time regions:
t-t0 = (6.08, 100.87 ksec):
NH_excess= (0.61+/-0.03) x 10^22 cm^-2 (z=0)
(NH_Galactic= 0.017 x 10^22 cm^-2)
Gamma = 1.97+/-0.06
Flux= (5.99+/-0.21) x 10^-11 erg cm^-2 s^-1 [0.3-10 keV]
chi^2/nu= 312.50/254
t-t0 = (116.89, 176.05 ksec):
NH_excess= (0.60+/-0.05) x 10^22 cm^-2 (z=0)
Gamma= 1.98+/-0.05
Flux= (1.09+/-0.05) x 10^-10 erg cm^-2 s^-1 [0.3-10 keV]
chi^2/nu= 253.06/224
are well-fit by absorbed powerlaw models. In both of these regions, an absorbed blackbody fit has a significantly lower fit quality (chi^2/nu= 845.01/254, and 609.46/224, respectively). In contrast, in times of high flux, the WT and PC mode spectra are soft:
t-t0 = (1.49, 6.08 ksec; WT):
NH_excess = (0.61+/-0.03) x 10^22 cm^-2 (z=0)
Gamma= 1.63+/-0.04
Flux= (1.21+/-0.03) x 10^-9 erg cm^-2 s^-1 [0.3-10 keV]
chi^2/nu= 840.42/449
t-t0 = (111.35, 111.49 ksec; WT):
NH_excess= (0.66+/-0.02) x 10^22 cm^-2 (z=0)
Gamma= 1.64+/-0.03
Flux= (2.02+/-0.03) x 10^-9 erg cm^-2 s^-1 [0.3-10 keV]
chi^2/nu= 1339.16/583
t-t0= (116.00, 116.46 ksec; PC):
NH_excess= (0.3+/-0.3) x 10^22 cm^-2 (z=0)
Gamma= 1.4+/-0.4
Flux= (1.3+/-0.2) x 10^-9 erg cm^-2 s^-1 [0.3-10 keV]
chi^2/nu= 9.16/10
In each of these 3 high flux time regions, a blackbody fit is preferred relative to the quoted powerlaw fits above (chi^2/nu= 762.17/449, 1235.52/583, and 7.82/11, respectively). In these regions, the best-fit temperature is kT ~ 1 keV. The fact that none of the fits in these regions exhibits chi^2/nu ~ 1 may suggest a superposition of thermal and non-thermal components is required. We note that the BAT photon indices (Sakamoto et al.; GCN #11842) are comparable to the hard photon indices here, possibly indicating a continuation of these spectra to higher energies.
The energetics of the continuing event are intriguing, with an average luminosity in the X-rays of L_X ~ 2.5 x 10^47 erg/s continuing for T~10^5 sec implying a total energy output of E_X,tot ~ 2.5x10^52 erg. Assuming this energy is liberated in an accretion process at 10% efficiency, the total mass involved in accretion over the first day is ~0.1 M_sun. If the source of this accreted mass is a tidal disruption of a main sequence star (M_* ~ 0.5 M_sun; R_* ~ 10^10 cm), then this implies a black hole mass of ~few x 10^6 M_sun assuming the disruption radius at the size scale implied by the X-ray variability timescale (500 s; Campana et al. [GCN 11843]), l=1.5x10^12 cm. This disruption radius would be several times the innermost stable orbit of a 10^6 M_sun BH.
We also note an analogy of the reported behavior to blazar activity, in that highly variable gamma-ray and (non-thermal) X-ray emission is accompanied by (presumably) non-thermal long-wavelength emission (radio and sub-mm). The compressed timescales of variability from ordinary blazars (~10 minutes vs ~1 day) could be attributable to a smaller mass BH (~10^6 instead of 10^8 - 10^9 M_sun).
Taken together, this suggests that GRB 110328A / Swift J164449.3+57345 may be the result of tidal disruption event viewed (nearly) face on to a newly formed jet. Note if this is the case--and the evidence for beamed emission has been suggested elsewhere by Campana et al. [GCN 11843]--then the energetics and accretion-mass inferences would be relaxed by an unknown Gamma factor. Hence, the inferred BH mass of few x 10^6 M_sun might be considered an upper limit. With this interpretation, we would expect the emission to be astrometrically coincident with the nucelus of the host galaxy (something not observed with GRBs in general), exhibit time-variable behavior at radio wavebands (including short timescale flickering), and a rising OIR event over the next few weeks (to an unobscured absolute magnitude of M_V ~ -18 to -21 mag)."
We thank Eliot Quataert for helpful discussions.
GCN Circular 11846
Subject
GRB 110328A / Swift J164449.3+573451: Gemini and UKIRT IR observations
Date
2011-03-30T21:38:38Z (15 years ago)
From
Andrew Levan at U.of Leicester <A.J.Levan@warwick.ac.uk>
A.J. Levan (U. Warwick), N.R. Tanvir (U. Leicester), A. Morgan,
J. Bloom, S.B. Cenko (U.C. Berkeley) report for a larger collaboration:
"We obtained IR observations of GRB 110328A using both UKIRT/WFCAM
and Gemini-N/NIRI on 30 March 2011, beginning at ~13:00 UT.
Observations were obtained in J and H with UKIRT and in K with NIRI.
The source is detected in all filters, and confirms the very red
colour of the counterpart suggested by Morgan et al (GCN 11845).
Comparison of these images with those taken with PAIRITEL provides
maginal evidence for brightening between the PAIRITEL observations
and those obtained with UKIRT and Gemini. Formally Delta_K = 0.52
+/- 0.21 and Delta_H = 0.73 +/- 0.35 mag. However, we caution that
the difference between instruments, coupled with slightly different
filter responses, may impact these results, and hence at present we
cannot establish variability with high confidence.
Further observations are planned"
GCN Circular 11845
Subject
GRB 110328A / Swift J164449.3+573451: PAIRITEL NIR Detection in 2nd Epoch
Date
2011-03-30T21:28:44Z (15 years ago)
From
Adam Morgan at U.C. Berkeley <qmorgan@gmail.com>
A. N. Morgan, J. S. Bloom (UC Berkeley), A.J. Levan (U. Warwick), and
N.R. Tanvir (U. Leicester), report:
We continued to observe the field of GRB 110328A / Swift
J164449.3+573451 (Cummings et al., GCN 11823, Barthelmy et al., GCN
11824) with the 1.3m PAIRITEL located at Mt. Hopkins, Arizona for a
second epoch beginning at 2011-03-30 08:22:23 UT, ~43.4 hours after
the first Swift Trigger. In mosaics (effective exposure time of 1.9
hours) taken simultaneously in the J, H, and Ks filters, we detect a
source in all 3 filters at the optical/radio position (Cenko et al.,
GCN 11827, Leloudas et al., GCN 11830, Zauderer et al., GCN 11836,
Volnova et al., GCN 11837, Im et al. GCN 11839, Kelemen et al. 11840,
Zauderer et al. GCN 11841).
The preliminary photometry yields:
post burst
t_mid (hr) exp.(hr) filt mag m_err
44.9 1.90 J 19.1 0.3
44.9 1.90 H 18.9 0.5
44.9 1.90 Ks 17.3 0.4
Compared to our first epoch upper limits at ~20 hours post-burst
(Morgan et al., GCN 11838), these values suggest either a constant
source or re-brightening in J.
All magnitudes are given in the Vega system, calibrated to 2MASS. No
correction for Galactic extinction has been made to the above reported
values.
GCN Circular 11844
Subject
GRB 110328A / Swift J164449.3+573451: No optical variability of the optical counterpart
Date
2011-03-30T20:49:44Z (15 years ago)
From
Giorgos Leloudas at Dark Cosmology Centre <giorgos@dark-cosmology.dk>
G. Leloudas, D. Malesani (DARK/NBI), D. Xu (WIS), P. Jakobsson (U.
Iceland), J. Telting (NOT), report on behalf of a larger collaboration.
We observed again the field of the peculiar source GRB 110328A / Swift
J164449.3+573451 (Cummings et al., GCN 11823; Kennea et al., ATel
3242) with the NOT equipped with ALFOSC, using the same instrument
setup adopted in our first observation (Leloudas et al. GCN 11830).
Observations were carried in the R and z filters with exposures of
3x600 and 8x300 s, respectively. The observations were carried out
starting on 04:10 UT, roughly 26 hr after our first observations and
39 hr after the first Swift trigger.
The reported galaxy at z=0.35 (Cenko et al., GCN 11827; Levan et al.,
GCN 11833; Thoene et al., GCN 11834), which is consistent with the
position of the X-ray and radio emission (Osborne et al., GCN 11826;
Zauderer et al., GCN 11836), does not show measurable variability over
this time range.
Its R-flux has remained constant to within 0.02 +- 0.07 mag, relative
to several stars in the field. Image subtraction using ISIS (Alard
2000, A&AS 144, 363) also does not reveal any variable source on the
potential host galaxy or nearby. Similarly, no variability is observed
in the z-band up to 0.02 +- 0.15 mag. Given the strong variability of
the X-ray counterpart over the same time span, this suggests that the
optical emission is dominated by the host galaxy contribution.
Preliminary photometric calibration using the Landolt standard field
SA 107 yields R = 19.35 for the USNO star 1475-0312998, close to its
archival value (R=19.4) that was used in GCN 11830.
GCN Circular 11843
Subject
GRB 110328A / Swift J164449.3+573451: beamed emission
Date
2011-03-30T17:23:02Z (15 years ago)
From
Sergio Campana at INAF-OAB <sergio.campana@brera.inaf.it>
S. Campana (INAF-OAB), S. Covino (INAF-OAB), G. Tagliaferri (INAF-OAB),
V. D'Elia (ASI-ASDC), L. Stella (INAF-OAR), R. Salvaterra (Insubria
University):
GRB 110328A/ Swift J164449.3+573451 is characterized by a very fast
variability. A doubling time less than 500 s can be easily recovered
from the Swift X-ray data. Assuming that the entire source is varying,
this poses a limit on the mass of the varying object of M1<5x10^5 solar
masses, based on the arguments of Cavallo & Rees (1978) and assuming
a conversion efficiency of ~10%, typical of accretion onto a black hole.
On the other side if this source is really at z=0.354 (Levan et al. GCN
11833; Thoene et al. GCN 11834), as confirmed by the radio position
of the counterpart (Zauderer et al. GCN 11836), its peak flux of ~10^-8
erg/cm2/s (0.3-10 keV based on the Swift Burst analyser, Evans et al.
2010, A&A 509 A102) implies a luminosity of ~5x10^48 erg/s.
In order not to overcome the Eddington limit a mass of M2>3x10^10
solar masses is needed.
The two mass estimates strongly disagree providing clear evidence for
a highly beamed emission.
GCN Circular 11842
Subject
GRB 110328A / Swift J164449.3+573451: BAT refined analysis
Date
2011-03-30T17:06:00Z (15 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <james.r.cummings@nasa.gov>
T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), A. Melandri (INAF-OAB),
D. M. Palmer (LANL), M. Stamatikos (OSU), J. Tueller (GSFC),
T. N. Ukwatta (MSU)
The source originally identified as GRB 110328A (Cummings et al.
GCN Circ. #11823 and Barthelmy et al. GCN Circ. #11824) has triggered BAT
several times. It is a highly unusual object. It is coincident with an
optical source at redshift z = 0.35 (Levan et al., GCN Circ #11833), as
well as a radio source (Zauderer et al., GCN Circ #11836). The source
continues to be detectable and variable in BAT more than 40 hours after
the initial trigger, with peak brightness on the order of 200 mCrab. The
source is at high galactic latitude, 39.4 degrees.
The summary of BAT triggers so far is:
TrigNum Date Time TrigDur Intensity
UT [sec] [c/sec]
450158 28 Mar 12:57:45 1208 6.1
450161 28 Mar 13:40:41 64 19.4
450257 29 Mar 18:26:25 320 15.6
450258 29 Mar 19:57:45 64 38.2
This table does not represent all the possible triggers, because the on-
board triggering algorithm requires the intensity of the any following
event to be slightly more than twice the previous intensity. Also note
that the on-board threshold was commanded to zero between the 2nd and 3rd
triggers in order to enhance future triggers, and that it was later
commanded to be 4 times the 4th trigger's intensity after the 4th trigger
to suppress further triggers.
The observation of the source including the discovery image was T-4 sec
to T+1211 sec. A fit to a power law spectrum from BAT survey data on this
interval has a photon index of 1.72 � 0.18. The fluence from 15 to
150 keV using this model was (3.0 � 0.3) x 10^-6 ergs/cm^2. The first
followup observation, during which the second trigger occurred, was
T+1465 sec to T+2348 sec. The photon index from that observation was
1.37 � 0.11. The fluence was (2.7 � 0.2) x 10^-6 ergs/cm^2.
The light curve from the BAT transient monitor (15-50 keV):
http://swift.gsfc.nasa.gov/docs/swift/results/transients/weak/SwiftJ164449.3p573451/
shows variability, but that the source was first detectable on 25-March-2011
and has, on average, continued to brighten since the trigger.
Please see also Kennea et al., ATel#3242 for more information:
http://www.astronomerstelegram.org/?read=3242
GCN Circular 11841
Subject
GRB 110328A / Swift J164449.3+573451: CARMA mm detection
Date
2011-03-30T14:49:44Z (15 years ago)
From
Ashley Zauderer at CfA <bevinashley@gmail.com>
Ashley Zauderer, Edo Berger (Harvard), Dale A. Frail (NRAO), Alicia
Soderberg (Harvard), Shri Kulkarni (Caltech), Shaye Storm (UMD) and Chat
Hull (UC Berkeley) report:
"We observed the peculiar Swift event GRB110328A / Swift
J164449.3+573451 (GCNs 11823, 11824) with CARMA beginning on March 30.39
UT at 98 GHz. We find a bright, unresolved source coincident with our
EVLA detection (GCN 11836) with a preliminary flux density of about 15 mJy.
Additional analysis is on-going and further observations are planned.
We thank the CARMA observatory personnel for their support of these
observations."
GCN Circular 11840
Subject
GRB 110328A / Swift J164449.3+573451: Konkoly observations
Date
2011-03-30T11:52:40Z (15 years ago)
From
Janos Kelemen at Konkoly Obs/Hungary <kelemen@konkoly.hu>
J. Kelemen, K. Sarnetzky (Konkoly Obs.) on behalf of the GRB OT observing
program at the Konkoly Observatory.
On the night 29 - 30/03/2011 we observed the field of GRB 110328A / Swift
J164449.3+573451 detected by Swift (Cummings et al., GCN 11823; Barthelmy et
al., GCN 11824) with a 60/90 cm Schmidt telescope located at the Mountain
Station of the Konkoly Observatory. The OT reported by Cenko et al., (GCN
11827); G. Leloudas et. al., (GCN11830) is visible on the coadded frames
(total exposition time 900 sec).
Based on the UCAC3 catalogue the position of the object:
(J2000) 16 44 49.93 +57 34 59.1 (+/- 0.14 arcsec)
Our R band magnitude estimation based on the same catalogue:
30.08460/03/2011 UT. 21.8 +/- 0.2 mag.
We are planning further observations to determine the variability.
GCN Circular 11839
Subject
GRB 110328A / Swift J164449.3+573451: LOAO R-band Observation
Date
2011-03-30T06:13:19Z (15 years ago)
From
Myungshin Im at Seoul Nat U <mim@astro.snu.ac.kr>
Myungshin Im (CEOU/SNU), Yuji Urata (NCU), and Kuiyun Huang (ASIAA)
on behalf of EAFON
Starting at 2011 March 29,10:53:45 UT (roughly 22 hrs after the 1st
burst alert), we obtained a series of R-band images of the field of
GRB 110328A / Swift J164449.3+573451 (Cummings et al. GCN 11823) using
the 1.0m telescope at Mt. Lemmon, AZ, USA.
We identify the optical counterpart (Volonva et al. GCN 11837,
Cenko et al. GCN 11827, Leloudas et al. GCN 11830, Degarte et al.
GCN 11834) in a stacked image with the total integration time of
2500 secs.
A preliminary analysis shows that the brightness of the counterpart
is R = 22.1 +- 0.4 mag, where the photometry calibration is based on
the USNO B-1 star 1475-0312998.
We thank the LOAO operator, I. Baek for her assistance of this
observation.
GCN Circular 11838
Subject
GRB 110328A / Swift J164449.3+573451: PAIRITEL NIR Upper Limits
Date
2011-03-30T03:07:14Z (15 years ago)
From
Adam Morgan at U.C. Berkeley <qmorgan@gmail.com>
A. N. Morgan, C.R. Klein, A. A. Miller, and J. S. Bloom (UC Berkeley) report:
We observed the field of GRB 110328A / Swift J164449.3+573451
(Cummings et al., GCN 11823, Barthelmy et al., GCN 11824) with the
1.3m PAIRITEL located at Mt. Hopkins, Arizona. Observations began at
2011-03-29 08:32:46 UT, ~19.6 hours after the first Swift Trigger. In
mosaics (effective exposure time of 0.39 hours) taken simultaneously
in the J, H, and Ks filters, we do not detect any source at the
optical/radio position (Cenko et al., GCN 11827, Leloudas et al., GCN
11830, Zauderer et al., GCN 11836, Volnova et al. GCN 11837).
The preliminary photometry yields:
post burst
t_mid (hr) exp.(hr) filt U. Limit (3 sig)
19.9 0.39 J > 19.1
19.9 0.39 H > 18.2
19.9 0.39 Ks > 16.9
Further observations will be performed tonight. All magnitudes are
given in the Vega system, calibrated to 2MASS. No correction for
Galactic extinction has been made to the above reported values.
GCN Circular 11837
Subject
GRB 110328A / Swift J164449.3+573451: optical observations
Date
2011-03-30T01:45:38Z (15 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
A. Volnova (SAI MSU), A. Pozanenko (IKI), E. Klunko (ISTP) on behalf of
larger GRB follow up collaboration report:
We observed the field of GRB 110328A / Swift J164449.3+573451 (Cummings et
al. GCN 11823) with AZT-33IK telescope of Sayan observatory (Mondy) starting
on March 28 (UT) 13:46:35, i.e. 6 minutes after second trigger (Barthelmy et
al. GCNC 11824).
We identified the optical counterpart (Cenko et al. GCN 11827, Leloudas et
al. GCN 11830) in the combined image of a total exposure of 67 min. The
photometry of the optical counterpart in the combined image is R=21.50 +/-
0.10 and based on the USNO-A2.0 star 1425-08596694 assuming R=16.6. The
photometry is still preliminary and calibration of field stars is necessary
(Cenko et al. GCN 11827) to confirm the variable nature of the optical
counterpart.
[GCN OPS NOTE(30apr11): Per author's request, Elunko was changed to Klunko.]
GCN Circular 11836
Subject
GRB 110328A / Swift J164449.3+573451: EVLA Detection
Date
2011-03-29T21:50:24Z (15 years ago)
From
Ashley Zauderer at CfA <bevinashley@gmail.com>
Ashley Zauderer, Edo Berger (Harvard), Dale A. Frail (NRAO) and Alicia
Soderberg (Harvard) report on behalf of a larger collaboration:
We observed the peculiar Swift event GRB110328A / Swift J164449.3+573451
(GCNs 11823, 11824) with the EVLA on March 29.37 UT at two frequencies
(1 GHz bandwidth each) centered at 4.94 and 6.69 GHz. We find a
single, unresolved >10 sigma radio source within the Swift-XRT error
circle (GCN 11826) at the following position (J2000):
RA = 16:44:49.93,
DEC = +57:34:59.7
coincident with the PTF and NOT optical source (GCNs 11827 and 11830).
The optical source showed no clear variability in brightness and is thus
most likely the host galaxy of this event, with a redshift of z=0.35
(GCNs 11833, 11834). The EVLA source is most likely the radio afterglow
of this peculiar burst.
Further observations are planned.
GCN Circular 11834
Subject
GRB 110328A / Swift J164449.3+573451: optical spectroscopy from GTC
Date
2011-03-29T16:28:48Z (15 years ago)
From
Antonio Deugarte at IAA-CSIC <deugarte@iaa.es>
C.C. Thoene, J. Gorosabel (IAA-CSIC), A. de Ugarte Postigo (DARK/NBI), R.
Sanchez-Ramirez (IAA-CSIC), T. Mu�oz-Dar�as (OAB-INAF), S. Guziy and A.J.
Castro-Tirado (IAA-CSIC) report on behalf of a larger collaboration:
We observed the field of GRB 110328A / Swift J164449.3+573451 (Cummings et
al. GCNC 11823) using the 10.4m GTC telescope in Roque de los Muchachos
Observatory (La Palma, Spain). We identified the optical counterpart
(Cenko et al. GCNC 11827, Leloudas et al. GCNC 11830) and obtained
low-resolution spectroscopy of the source. The observations consisted in
3x1200s exposures with the R300B grating starting at 4:40 UT of the 29th
March, 15.7h after the first BAT trigger).
In the spectrum we detect a good signal continuum from 4000 to 10000 A
with several emission lines superposed, which we identify as [OII],
[OIII], Hbeta and Halpha at a common redshift of 0.354, consistent with
the value reported by Levan et al. (GCNC 11833).
We acknowledge the excellent support from the GTC staff.
GCN Circular 11833
Subject
GRB 110328A: Gemini spectroscopic observations
Date
2011-03-29T16:13:27Z (15 years ago)
From
Andrew Levan at U.of Leicester <A.J.Levan@warwick.ac.uk>
A.J. Levan (U. Warwick), N.R. Tanvir, K. Wiersema (U. Leicester),
D. Perley (U.C. Berkeley) report for a larger collaboration:
"We obtained spectroscopic observations of the optical source
associated with GRB 110328A with Gemini/GMOS on 29th March 2011. A
preliminary reduction shows emission lines associated with Hbeta,
and OIII (4959, 5007) at a common redshift of z~0.35.
This suggests either a chance alignment of a soft X-ray transient
with a external galaxy (although the lack of an optical counterpart
within our Galaxy would be puzzling), or, more likely, that GRB
110328A is an extragalactic object, with properties unlike any
previously observed GRB
We thank the staff of Gemini, in particular Richard McDermid, for
the execution of these observations"
GCN Circular 11830
Subject
GRB 110328A / Swift J164449.3+573451: NOT optical observations.
Date
2011-03-29T06:55:40Z (15 years ago)
From
Giorgos Leloudas at Dark Cosmology Centre <giorgos@dark-cosmology.dk>
G. Leloudas, D. Malesani (DARK/NBI), N.R. Tanvir (U. Leicester), Dong
Xu (WIS), A.J. Levan (U. Warwick), P. Jakobsson (U. Iceland), T.
Pursimo (NOT), report on behalf of a larger collaboration.
We used the Nordic Optical Telescope (La Palma, Spain) equipped with
ALFOSC to observe the field of GRB 110328A / Swift J164449.3+573451
(Cummings et al., GCN 11823; Barthelmy et al., GCN 11824).
Observations started at 01:47 UT (12.8 and 12.1 hr after the first and
second trigger, respectively). We obtained 2x600 s in BVR and 4x300 s
in z.
In all filters we detect an object at the coordinates (J2000):
RA: 16:44:50.0
DEC: +57:34:59.13
with an astrometric calibration error of approximately 0.3 arcsec.
This position is within the enhanced XRT error circle (Osborne et al.,
GCN 11826) and is consistent with the coordinates of the object
reported by Cenko et al. (GCN 11827) from pre-outburst images.
At the moment we have no good photometric calibration of the field so
photometry should be considered preliminary (see also GCN 11827).
Assuming R = R1 = 19.40 and B = B2 = 21.30 for the USNO B1.0 star
1475-0312998, we estimate for the counterpart B = 24.0 +- 0.2 and R =
22.6 +- 0.05 (statistical errors only).
At this stage it is not possible to verify whether the source is
variable.
GCN Circular 11829
Subject
GRB 110328A/ Swift J164449.3+573451 : Xinglong TNT Upper limit
Date
2011-03-29T01:44:00Z (15 years ago)
From
L.P. Xin at NAOC <xlp@bao.ac.cn>
L.P. Xin, Y.L. Qiu, J.Y. Wei, J. Wang, J.S. Deng,
C. Wu, X. H. Han, M, Zhai on behalf of EAFON report:
We observed GRB 110328A (Cummings et al. GCN 11823)
with Xinglong TNT telescope at 14:13:22 UT on March 28, 2011,
1.26 hour after the first burst trigger, 33 min after the second trigger.
A series of R-band images were obtained with an exposure
time of 300 sec for each frame. At the X-ray location of GRB 110328A,
and the likely optical counterpart position (Cenko et al. GCN 11827) ,
we do not find any new source down to the limit of 20 mag in R band
relatively to USNO B1.0 R2 mag at the mean time of 1.75 hour after the
first trigger .
Further observations from larger telescopes are encouraged.
This message may be cited.
GCN Circular 11827
Subject
GRB 110328A / Swift J164449.3+573451: PTF Quiescent Optical Counterpart
Date
2011-03-28T21:23:00Z (15 years ago)
From
S. Bradley Cenko at Caltech <cenko@srl.caltech.edu>
S. B. Cenko (UC Berkeley), P. E. Nugent (LBNL / UC Berkeley), Derek B. Fox
(Penn State), E. O. Ofek and M. M. Kasliwal (Caltech) report on behalf of
a larger collaboration:
As part of the Palomar Transient Factory, we have obtained pre-outburst
optical (R-band) imaging of the field of the high-energy transient source
GRB 110328A / Swift J164449.3+573451 (GCNs 11823, 11824) with the Palomar
48-inch Oschin Schmidt telescope over the time period from 2009 May to
2010 October. In a stacked frame of all available data, we find a faint,
unresolved source at location (J2000.0):
RA: 16:44:49.97 Dec: +57:34:59.7
The astrometric uncertainty associated with this position is ~ 150 mas
in each coordinate (based on the USNO-B1 catalog). This is consistent
with the enhanced XRT position (GCN 11826), and is therefore likely to be
associated with the high-energy transient. The detection of such a
relatively bright optical counterpart strongly disfavors a cosmological
long-duration GRB, and instead suggests that Swift J164449.3+573451 is
more likely a new Galactic transient source (GCN 11824, ATEL 3242).
In attempting to estimate the brightness of this object, we find that
nearby calibration stars from the USNO-B catalog are likely to be
inaccurate (resulting in limits significantly deeper than our system can
achieve). Based on past observations of other fields, we estimate the
brightness of the counterpart to be R ~ 22, although we caution that
this estimate may suffer from significant uncertainty.
GCN Circular 11826
Subject
GRB 110328A: Enhanced Swift-XRT position
Date
2011-03-28T18:31:56Z (15 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 2353 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 110328A, 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 = 251.20787, +57.58334 which is equivalent
to:
RA (J2000): 16h 44m 49.89s
Dec (J2000): +57d 35' 00.0"
with an uncertainty of 1.7 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 11824
Subject
GRB 110328A: a second trigger, probably a hard X-ray transient (Swift J164449.3+573451)
Date
2011-03-28T14:33:10Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), D. N. Burrows (PSU),
J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC),
J. M. Gelbord (PSU), S. T. Holland (CRESST/USRA/GSFC),
E. A. Hoversten (PSU), H. A. Krimm (CRESST/GSFC/USRA),
F. E. Marshall (NASA/GSFC), C. Pagani (U Leicester),
K. L. Page (U Leicester), T. Sakamoto (NASA/UMBC),
C. J. Saxton (UCL-MSSL), E. Sonbas (GSFC/USRA/Adiyaman Univ.),
R. L. C. Starling (U Leicester), M. C. Stroh (PSU) and
C. A. Swenson (PSU) report on behalf of the Swift Team:
At 13:40:41 UT, the Swift Burst Alert Telescope (BAT) re-triggered on
what we are tentatively calling GRB 110328A (trigger=450161).
The BAT on-board calculated location is consistent with the coordinates
reported for GRB 110328A (GCN Circ 11823; Cummings et al).
Both this trigger and the earlier trigger (450158) were image triggers,
so the light curves do not show any significant features. The current
trigger was on the rise to the SAA. The source is brightening.
It is quite rare for BAT to trigger a second time on a GRB, so this
is either an unusually long GRB, GRB 110328A, or a new galactic transient,
Swift J164449.3+573451. The galactic coordinates are longitude=86.71,
latitude=+39.44.
We note that the XRT was in Windowed Timing mode during the entire
previous observing window, indicating that the X-ray counterpart
was quite bright (> 10 cps). This also suggests either a very
long-lived GRB or a galactic transient.
We encourage observations at other wavelengths to help determine
the nature of this object.
GCN Circular 11823
Subject
GRB 110328A: Swift detection of a burst
Date
2011-03-28T13:32:29Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
J. R. Cummings (NASA/UMBC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), D. N. Burrows (PSU),
S. Campana (INAF-OAB), V. D'Elia (ASDC), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU), C. Guidorzi (U Ferrara),
S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU),
J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA),
O. M. Littlejohns (U Leicester), R. Margutti (INAF-OAB),
F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB),
C. Pagani (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL), P. Romano (INAF-IASFPA), M. H. Siegel (PSU),
E. Sonbas (GSFC/USRA/Adiyaman Univ.), R. L. C. Starling (U Leicester),
G. Stratta (ASDC), G. Tagliaferri (INAF-OAB) and
E. Troja (NASA/GSFC/ORAU) report on behalf of the Swift Team:
At 12:57:45 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 110328A (trigger=450158). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 251.233, +57.590 which is
RA(J2000) = 16h 44m 56s
Dec(J2000) = +57d 35' 25"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). As is typical for 20-min long image triggers,
the BAT lightcurve does not show anything significant.
The XRT began observing the field at 13:22:19.8 UT, 1474.6 seconds
after the BAT trigger. XRT found a bright, uncatalogued X-ray source
located at RA, Dec 251.2054, +57.5808 which is equivalent to:
RA(J2000) = 16h 44m 49.29s
Dec(J2000) = +57d 34' 50.8"
with an uncertainty of 6.3 arcseconds (radius, 90% containment). This
location is 62 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy.
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 1482 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. 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 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.)