GRB 091221
GCN Circular 10283
Subject
GRB 091221: Swift detection of a burst
Date
2009-12-21T21:17:35Z (15 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
H. A. Krimm (CRESST/GSFC/USRA), D. N. Burrows (PSU),
P.A. Curran (MSSL-UCL), A. de Ugarte Postigo (INAF-OAB),
N. Gehrels (NASA/GSFC), D. Grupe (PSU), C. Guidorzi (U Ferrara),
S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU),
N. P. M. Kuin (MSSL), J. Mao (INAF-OAB),
R. Margutti (Univ Bicocca&OAB), C. B. Markwardt (CRESST/GSFC/UMD),
F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),
D. M. Palmer (LANL), J. L. Racusin (NASA/GSFC),
P. Romano (INAF-IASFPA), B. Sbarufatti (INAF-IASFPA),
M. H. Siegel (PSU), M. C. Stroh (PSU), E. Troja (NASA/GSFC/ORAU) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:
At 20:52:52 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 091221 (trigger=380311). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 55.754, +23.212 which is
RA(J2000) = 03h 43m 01s
Dec(J2000) = +23d 12' 42"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows a peak from T+0 to T+15
seconds with a second, larger peak from T+15 to T+40. There is
some complexity in the light curve from A0535+262 (currently in outburst
at ~5 Crabs of flux) in the Field Of View, but the GRB peaks are
distinguishable from the softer A0535+262 emission. The peak count
rate was 3500 counts/sec at ~30 sec after the trigger.
The XRT began observing the field at 20:54:04.7 UT, 72.4 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 55.79831, 23.24030
which is equivalent to:
RA(J2000) = 03h 43m 11.59s
Dec(J2000) = +23d 14' 25.1"
with an uncertainty of 4.2 arcseconds (radius, 90% containment). This
position may be improved as more data are received; the latest position
is available at http://www.swift.ac.uk/sper. This position is
170 arcseconds from the BAT position.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of
1.09e+21 cm^-2 (Kalberla et al. 2005).
The initial flux in the 2.5 s image was 1.47e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White
filter starting 79 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 0.22. We note the possibility of a faint source on the
northern edge of the XRT error circle. Further analysis is
forthcoming.
Burst Advocate for this burst is H. A. Krimm (krimm AT milkyway.gsfc.nasa.gov).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
GCN Circular 10284
Subject
GRB 091221: ROTSE-III Detection of Optical Counterpart
Date
2009-12-21T21:37:02Z (15 years ago)
From
Shashi Bhushan Pandey at ROTSE <shaship@umich.edu>
GRB 091221: ROTSE-III Detection of Optical Counterpart
W. Zheng, F. Yuan and S. B. Pandey (U Mich), report on behalf of the ROTSE
collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia,
responded to GRB 091221 (Swift trigger 380311, GCN 10283 Krimm et al.). The
first image was at 20:53:18.1 UT, 25.8 s after the burst (9.1 s after the
GCN notice time). The unfiltered images are calibrated relative to USNO
A2.0. We detect a 17.4 magnitude, source with coordinates:
03:43:11.47 +23:14:29.38 (J2000), with positional uncertainty
of 1" or better
start UT mag mlim(of image)
----------------------------------
20:54:49.5 17.4 18.0
This source is not visible in DSS (second epoch), 2MASS or the MPChecker
database.
A jpeg image is available at
http://www.rotse.net/images/gsb380311_3c011-020_key.jpg, the candidate is
marked as 110.
Continuing observations are in progress.
GCN Circular 10285
Subject
GRB 091221: UVOT Confirmation of an Optical Afterglow
Date
2009-12-21T22:12:23Z (15 years ago)
From
Stephen Holland at USRA/NASA/GSFC/SSC <Stephen.T.Holland@nasa.gov>
S. T. Holland (CRESST/GSFC/USRA), M. de Pasquale (MSSL),
P. Kuin (MSSL), and H. A. Krimm (CRESST/GSFC/USRA)
report on the behalf of the Swift/UVOT team:
The Swift/UVOT observed the field of GRB 091221 (Krimm et
al. 2009, GCN Circ. 10283) starting approximately 80 s after the BAT
detection. We confirm the optical afterglow detected by Krimm et
al. 2009, GCN Circ 10283 and Zheng et al. 2009, GCN Circ. 10284. The
preliminary UVOT position is
RA = 03:43:11.47 = 55.79771 deg
Dec = +23:14:28.9 = +23.24136 deg
with a preliminary error estimate of 0.6 arcsec (radius, 90%
containment). The preliminary white magnitude is
Filter TSTART TSTOP EXPOSURE Mag Err
---------------------------------------------------------
White 80 230 150 20.22 0.28
---------------------------------------------------------
The quoted upper limits have not been corrected for the expected
Galactic extinction along the line of sight corresponding to a
reddening of E_{B-V} = 0.22 mag (Schlegel et al., 1998, ApJS, 500,
525). All photometry is on the UVOT photometry system described in
Poole et al. (2008, MNRAS, 383, 627).
GCN Circular 10286
Subject
GRB 091221, GROND observations
Date
2009-12-22T03:20:01Z (15 years ago)
From
Sylvio Klose at TLS Tautenburg <klose@tls-tautenburg.de>
R. Filgas, P. Afonso (both MPE Garching), S. Klose (TLS Tautenburg), and
J. Greiner (MPE Garching), report on behalf of the GROND team:
GROND (Greiner et al. 2008, PASP 120, 405), the 7-channel imager mounted
at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), started
follow-up observations of GRB 091221 (Krimm et al. 2009, GCN 10283) on Dec
22, at 01:27 UT (4.5 hrs after the burst).
For the suggested GRB afterglow (Zheng et al. 2009, GCN 10284; Holland et
al. 2009, GCN 10285), based on a first 8 min exposure, we estimate the
following preliminary magnitudes (in the AB system):
g' = 22.90 +/- 0.30
r' = 22.27 +/- 0.30
i' = 21.95 +/- 0.30
z' = 22.20 +/- 0.30
J = 20.16 +/- 0.20
H > 19.9
K > 19.1
using GROND zeropoints and 2MASS catalog (airmass 1.8). Observations are
ongoing.
Taking into account a Galactic reddening of E(B-V)=0.22 mag (Holland et
al. 2009, GCN 10285), we estimate a photometric redshift of z<3.5. At
present we cannot decide if the z'-band magnitude is indicating to a
broad-band absorption feature or if we underestimate the magnitude error
in this band (where the source is very faint).
GCN Circular 10287
Subject
GRB 091221: Enhanced Swift-XRT position
Date
2009-12-22T09:17:25Z (15 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
P.A. Evans and M.R. Goad (U. Leicester) report
on behalf of the Swift-XRT team:
Using 3.7 ks of XRT Photon Counting mode data and 7 UVOT
images, 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 =
55.79749, 23.24119 which is equivalent to:
RA (J2000): 03 43 11.40
Dec (J2000): +23 14 28.3
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 is an official product of the Swift-XRT team.
GCN Circular 10288
Subject
GRB 091221: Swift-XRT refined analysis
Date
2009-12-22T10:50:17Z (15 years ago)
From
Jirong Mao at INAF-OAB <jirong.mao@brera.inaf.it>
J. Mao (INAF-OAB) and H. A. Krimm (CRESST/GSFC/USRA) report on behalf of
the Swift-XRT team:
We have analysed 4.7 ks of XRT data for GRB 091221 (Krimm et al. GCN
Circ. 10283), from 78 s to
11.6 ks after the BAT trigger. The data comprise 332 s in Windowed
Timing (WT) mode with the remainder
in Photon Counting (PC) mode. The UVOT-enhanced XRT position was given
in Evans et al.
(GCN Circ. 10287).
The light curve shows a flare feature from T0+90 s to T0+200 s, the peak
value is about 55 count/s at
T0+106 s. After that, the light curve can be modelled with a power-law
decay with a decay index of
alpha=1.07 � 0.05.
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral
index of 2.52 (+0.16, -0.17). The best-fitting absorption column is 3.6
(+/- 0.4) x 1021 cm^-2, in excess of
the Galactic value of 1.1 x 1021 cm^-2 (Kalberla et al. 2005).
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is
4.4 x 10^-11 (7.2 x 10^-11) erg cm^-2 count^-1. The spectrum formed from
the PC mode data can be fitted
with an absorbed power-law with a photon spectral index of 1.68 (+0.45,
-0.51). The best-fitting absorption
column is about 1.1 x 1021 cm^-2, in consistent with the Galactic value.
If the light curve continues to decay with a power-law decay index of
1.07, the count rate at T0+24 hours
will be 2.3 x 10^-3 count s^-1, corresponding to an observed
(unabsorbed) 0.3-10 keV flux of
1.4 x 10^-13 (1.6 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00380311.
This circular is an official product of the Swift-XRT team.
GCN Circular 10289
Subject
GRB 091221: Swift/UVOT refined analysis
Date
2009-12-22T13:58:52Z (15 years ago)
From
Massimiliano de Pasquale at MSSL-UCL <mdp@mssl.ucl.ac.uk>
M. De Pasquale (MSSL/UCL) and H. Krimm (CRESST/GSFC/USRA)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB091221
80s after the BAT trigger with a 150s finding chart exposure in
the White filter.
We detect the optical afterglow in the finding chart exposure.
The refined UVOT position is RA = 55.79750, Dec = 23.24119 (J2000),
corresponding to
RA = 03h 43m 11.40s,
Dec = +23d 14m 28.3s (J2000)
with an estimated uncertainty of 0.6 arcsec (radius, 90% confidence).
This position is consistent with the XRT enhanced position (Evans
et al., GCN 10287) and ground-based detections (Zheng et al., GCN
10284; Klose et al., GCN 10286).
The afterglow is not detected anymore in single or summed exposures
in all filters. Preliminary magnitudes and 3 sigma upper limits
are reported below.
Filter T_start(s) T_stop(s) Exposure(s) Mag Err
-----------------------------------------------------------------------
white 80 230 149.8 20.19 +/- 0.27
white 3657 11605 927.1 >21.62
v 4068 5704 393.2 >19.56
b 3452 11054 1278.4 >21.11
u 4683 10142 1083.4 >20.68
uvw1 4478 6075 354.4 >19.96
uvm2 4273 5909 393.3 >19.79
uvw2 3863 5499 393.3 >20.07
------------------------------------------------------------------------
The values quoted above are not corrected for the heavy Galactic
extinction corresponding to the reddening of E(B-V) = 0.22 in the
direction of the burst (Schlegel et al. 1998, ApJS, 500, 525). The
photometry is on the UVOT photometric system described in Poole et al.
(2008, MNRAS, 383, 627).
[GCN OPS NOTE(22dec09): Per author's request, the Subject-line
was changed from 091208B to 091221.]
GCN Circular 10290
Subject
GRB091221: Swift/UVOT refined analysis, correction.
Date
2009-12-22T14:06:10Z (15 years ago)
From
Massimiliano de Pasquale at MSSL-UCL <mdp@mssl.ucl.ac.uk>
M. De Pasquale (MSSL/UCL) reports:
GCN circular 10289 title is wrong. It should be
GRB091221: Swift/UVOT refined analysis
not GRB091208B.
I apologize for any confusion.
GCN Circular 10291
Subject
GRB 091221 Swift-BAT refined analysis
Date
2009-12-22T16:44:09Z (15 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <james.r.cummings@nasa.gov>
J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD),
D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC),
G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), 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 the recent telemetry
downlink, we report further analysis of BAT GRB 091221 (trigger #380311)
(Krimm, et al., GCN Circ.#10283). The BAT ground-calculated position is
RA, Dec = 55.798, 23.243 deg which is
RA(J2000) = 03h 43m 11.6s
Dec(J2000) = +23d 14' 35.2"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 62%.
The mask-weighted light curve shows a weak peak from T-45 to T-20 sec
and a stronger, slow-rise, complex peak from T-10 to T+42 sec. T90
(15-350 keV) is 68.5 +- 5.5 sec (estimated error including systematics).
The time-averaged spectrum from T-43.6 to T+41.1 sec is best fit by a
simple power-law model. The power law index of the time-averaged
spectrum is 1.59 +- 0.06. The fluence in the 15-150 keV band is
5.7 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from
T+20.70 sec in the 15-150 keV band is 3.0 +- 0.2 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/380311/BA/
GCN Circular 10293
Subject
GRB 091221: Fermi GBM Observation
Date
2009-12-23T21:02:35Z (15 years ago)
From
Colleen A. Wilson at NASA/MSFC/NSSTC <colleen.wilson@nasa.gov>
Colleen A. Wilson-Hodge (NASA/MSFC)
reports on behalf of the Fermi GBM Team:
"At 20:52:57.22 UT on 21 December 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 091221 (trigger 283121579 / 091221870) which
also triggered the SWIFT-BAT (Krimm et al. 2009, GCN 10283) The GBM
on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight is 53 degrees.
The GBM light curve shows/consists of single structured peak with a
duration (T90) of about 32 s (8-1000 keV). The time-averaged spectrum
from T0-2 s to T0+30 s is adequately fit by a Band function with
Epeak = 207 (+22/-17) keV, alpha = -0.69 +/- 0.07, and
beta = -2.3 (+0.2/-0.3)
(C-Stat 724.6 for 481 d.o.f.).
The event fluence (8-1000 keV) in this time interval is
(1.38 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+11.3 s in the 8-1000 keV band is 5.1 +/- 0.4 ph/s/cm^2.
During this burst, A0535+262 (currently in a bright outburst at an
intensity of ~3xCrab 12-50 keV) and the Crab rose from Earth
occultation, causing a significant rise in the background level. This
likely adds additional systematic errors to the results, especially T90.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 10294
Subject
GRB 091221: Skynet/PROMPT Detections
Date
2009-12-23T22:11:00Z (15 years ago)
From
Josh Haislip at U.North Carolina <haislip@physics.unc.edu>
J. Haislip, D. Reichart, K. Ivarsen, A. LaCluyze, R. Egger, A. Foster, J.
Moore, A. Oza, M. Schubel, J. Styblova, A. Trotter, J. A. Crain, and M.
Nysewander report:
Skynet observed the Swift/BAT localization of GRB 091221 (Palmer et al.,
GCN 10283) with four of the 16" PROMPT telescopes at CTIO beginning 4.3
hours after the trigger in BVRI.
We detect the afterglow (Palmer et al., GCN 10283; Zheng et al., GCN
10284). Stacking only images that increase the limiting magnitude yields:
mean 1-sig. 1-sig.
time sys. stat.
since cal. cal. cal.
trig. tel. exp. fil. magnitude stars unc. unc.
(h) (# x s) (mag) (mag)
4.9 PROMPT-5 44 x 80 I > 21.1 (3 sigma) 143 USNO B1 0.338 0.000
+ 1 x 40
4.9 PROMPT-4 42 x 80 R 21.49 +0.27 -0.22 139 USNO B1 0.362 0.000
4.9 PROMPT-3 41 x 80 B > 21.5 (3 sigma) 82 USNO B1 0.154 0.000
4.9 PROMPT-1 41 x 80 V 21.41 +0.42 -0.31 27 NOMAD 0.193 0.000
7.3 PROMPT-3 136 x 80 B > 22.1 (3 sigma) 79 USNO B1 0.153 0.000
7.3 PROMPT-5 134 x 80 I > 21.8 (3 sigma) 120 USNO B1 0.337 0.000
7.3 PROMPT-4 139 x 80 R 22.44 +0.38 -0.28 112 USNO B1 0.392 0.000
7.4 PROMPT-1 145 x 80 V > 22.0 (3 sigma) 28 NOMAD 0.112 0.000
GCN Circular 10295
Subject
GRB 091221 : IRSF NIR upper limit
Date
2009-12-25T14:42:23Z (15 years ago)
From
Kenta Nishimoto at Nagoya U/MOA-II <nishimo@stelab.nagoya-u.ac.jp>
K. Nishimoto, T. Sako, H. Naito, D. Suzuki (Nagoya Univ.) on behalf of
the MOA Collaboration,
M. Kurita (Nagoya Univ.), Y.Ita (NAOJ) on behalf of the IRSF Collaboration
report:
We searched for a NIR afterglow of GRB 091221 (GCN 10283, Krimm et al.)
starting from 22:27:49.7 UT on 2009 Dec 21 (95 minutes after the burst)
with the SIRIUS on the IRSF 1.4m telescope at SAAO in South Africa.
In images of a 150sec exposure with J, H and Ks filters, we did not find
any object within the error circle of the Swift XRT source position (
GCN 10287, Evans et al.)
Three sigma upper limits are the followings.
J > 19.5
H > 18.4
K > 17.0
This photometry was done by using the DoPhot and calibrated against the
2MASS cataloged stars.