GRB 180204A
GCN Circular 22375
Subject
GRB 180204A: Swift detection of a short burst
Date
2018-02-04T02:58:47Z (7 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
K. L. Page (U Leicester), A. P. Beardmore (U Leicester),
A. Deich (PSU), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), A. Tohuvavohu (PSU) and T. N. Ukwatta (LANL)
report on behalf of the Neil Gehrels Swift Observatory Team:
At 02:36:16 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180204A (trigger=808483). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 330.118, +30.846 which is
RA(J2000) = 22h 00m 28s
Dec(J2000) = +30d 50' 45"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a double-peaked
structure with a duration of about 1.5 sec. The peak count rate
was ~17000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 02:37:43.8 UT, 87.2 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 330.13359, 30.83807 which is equivalent
to:
RA(J2000) = 22h 00m 32.06s
Dec(J2000) = +30d 50' 17.1"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 56 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper. We
cannot determine whether the source is fading at the present time. No
spectrum from the promptly downlinked event data is yet available to
determine the column density.
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 92 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
0.10.
Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk).
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 22376
Subject
GRB 180204A: Swift-XRT refined Analysis
Date
2018-02-04T10:26:23Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
J.P. Osborne (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri
(INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), D.N. Burrows
(PSU), A. Tohuvavohu (PSU), S. J. LaPorte (PSU) and K.L. Page report on
behalf of the Swift-XRT team:
We have analysed 8.0 ks of XRT data for GRB 180204A (Page et al. GCN
Circ. 22375), from 90 s to 21.2 ks after the BAT trigger. The data
comprise 32 s in Windowed Timing (WT) mode with the remainder in Photon
Counting (PC) mode. The best available XRT position (using the
promptly downlinked event data, the XRT-UVOT alignment and matching
UVOT field sources to the USNO-B1 catalogue) is RA, Dec = 330.1333,
30.8381 which is equivalent to:
RA (J2000): 22 00 32.00
Dec(J2000): +30 50 17.1
with an uncertainty of 2.1 arcsec (radius, 90% confidence).
The light curve can be modelled with a power-law decay with a decay
index of alpha=1.15 (+/-0.03).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.02 (+0.23, -0.22). The
best-fitting absorption column is 6.9 (+1.7, -1.5) x 10^21 cm^-2, in
excess of the Galactic value of 1.0 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 4.3 x 10^-11 (7.6 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 6.9 (+1.7, -1.5) x 10^21 cm^-2
Galactic foreground: 1.0 x 10^21 cm^-2
Excess significance: 6.5 sigma
Photon index: 2.02 (+0.23, -0.22)
If the light curve continues to decay with a power-law decay index of
1.15, the count rate at T+24 hours will be 2.7 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x
10^-13 (2.0 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/00808483.
This circular is an official product of the Swift-XRT team.
GCN Circular 22377
Subject
GRB 180204A: Enhanced Swift-XRT position
Date
2018-02-04T10:47:55Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.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 6274 s of XRT Photon Counting mode data and 9 UVOT
images for GRB 180204A, 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 = 330.13329, +30.83785 which is equivalent
to:
RA (J2000): 22h 00m 31.99s
Dec (J2000): +30d 50' 16.2"
with an uncertainty of 1.4 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 22378
Subject
GRB 180204A: Fermi GBM detection
Date
2018-02-04T14:24:46Z (7 years ago)
From
Adam Goldstein at Fermi-GBM/UAH <adam.m.goldstein@msfc.nasa.gov>
P. Veres and C. Meegan (both UAH)
report on behalf of the Fermi GBM Team:
"At 02:36:16.93 UT on 04 February 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180204A (trigger 539404581 / 180204109) which was also detected by the Swift/BAT (Page et al., GCN 22375).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 68 degrees.
The GBM light curve shows two peaks
with a duration (T90) of about 1.2 s (50-300 keV).
The time-averaged spectrum from T0-0.1 s to T0+1.2 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.92 +/- 0.07 and
the cutoff energy, parameterized as Epeak, is 781 +/- 161 keV.
The event fluence (10-1000 keV) in this time interval is
(8.48 +/- 0.32)E-7 erg/cm^2. The 64-msec peak photon flux measured
starting from T0 in the 10-1000 keV band
is 19.7 +/- 1.6 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 22379
Subject
GRB 180204A: Swift/UVOT Upper Limits
Date
2018-02-04T16:50:12Z (7 years ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
N. P. M. Kuin (UCL-MSSL) and K. L. Page (U. Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180204A
92 s after the BAT trigger (Page et al., GCN Circ. 22375). A star is
present in the GSC whos position is consistent with the enhanced XRT
position (Osborne et al. GCN Circ. 22377). No optical afterglow above
the stellar flux has been detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 92 242 147 >20.3
u_FC 304 554 246 >19.9
white 92 17884 1210 >20.8
v 633 10587 1107 >19.0
b 560 23622 1840 >20.7
u 304 23062 2409 >21.1
w1 3943 22148 1917 >21.0
m2 658 11492 1095 >20.8
w2 609 6398 413 >20.1
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.10 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 22380
Subject
GRB 180204A: Swift-BAT refined analysis
Date
2018-02-04T22:02:03Z (7 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
J. R. Cummings (CPI), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), J. P. Norris (BSU),
K. L. Page (U Leicester), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-186 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180204A (trigger #808483)
(Page et al., GCN Circ. 22375). The BAT ground-calculated position is
RA, Dec = 330.123, 30.852 deg which is
RA(J2000) = 22h 00m 29.5s
Dec(J2000) = +30d 51' 07.5"
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 70%.
The mask-weighted light curve shows two distict pulses. The first
pulse starts and peaks at ~T0, and ends at ~T+0.2. The second pulse
starts at ~T+0.6 s, peaks at ~T+1 s, and ends at ~T+1.3 s.
T90 (15-350 keV) is 1.16 +- 0.12 sec (estimated error including systematics).
For the first pulse, the lag analysis finds a lag of -0.2 +- 1 ms for the
100-350 keV to 25-100 keV, and 0.2 +- 1.5 ms for the 50-100 keV to 15-25 keV
band. The second pulse has a lag of 5.6 +- 3.9 ms for the 100-350 keV to
25-100 keV, and 3.2 +- 6.6 ms for the 50-100 keV to 15-25 keV band.
These values are consistent with those of a short GRB.
The time-averaged spectrum from T-0.05 to T+1.29 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.09 +- 0.10. The fluence in the 15-150 keV band is 4.8 +- 0.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.05 sec in the 15-150 keV band
is 3.6 +- 0.3 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/808483/BA/
GCN Circular 22385
Subject
Konus-Wind observation of GRB 180204A
Date
2018-02-05T12:16:14Z (7 years ago)
From
Anna Kozlova at Ioffe Institute <ann_kozlova@mail.ioffe.ru>
A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:
The short-duration GRB 180204A (Swift-BAT detection and
analysis: Page et al., GCN 22375; Cummings et al., GCN 22380;
Fermi-GBM observation: Veres&Meegan, GCN 22378)
triggered Konus-Wind at T0=9372.902 s UT (02:36:12.902).
The burst light curve shows two peaks in the interval
from ~T0-0.1 s to ~T0+1.1 s. The emission is seen up to ~10 MeV.
As observed by Konus-Wind, the burst
had a fluence of 3.81(-0.57,+0.66)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0+0.038 s,
of 2.95(-0.80,+0.87)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The spectrum of the burst
(measured from T0 to T0+0.256 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.36(-0.29,+0.38)
and Ep = 843(-177,+263) keV (chi2 = 37/45 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.5
(chi2 = 37/44 dof)
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180204_T09372/
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 22399
Subject
GRB 180204A: MITSuME Okayama optical upper limits
Date
2018-02-07T08:04:10Z (7 years ago)
From
Kotaro Morita at Tokyo Tech <morita@hp.phys.titech.ac.jp>
K. Morita, R. Itoh, K. L. Murata, T. Yoshii, Y. Tachibana, S. Harita, T.
Ozawa, H. Mamiya, K. Shiraishi, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We searched for the optical counterpart of GRB 180204A (K. L. Page et al.,
GCN Circular #22375) with the optical three color (g', Rc, and Ic) CCD
cameras attached to the MITSuME 50 cm telescope of Okayama Astrophysical
Observatory, Japan.
The observation started on 2018-02-04 9:37:11.83 UT. We did not find any
new point source within the XRT circle (J. P. Osborne et al., GCN Circular
#22377) in all three bands.
We obtained following limits for the magnitudes.
T0+[h] MID-UT T-EXP[sec] g' Rc Ic
------------------------------------------------------------
-------------------------------------------
~7.0 9:48:54 1140 >17.5 >17.4 >17.0
------------------------------------------------------------
-------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration
GCN Circular 22422
Subject
GRB 180204A: 15 GHz upper limits from AMI
Date
2018-02-19T11:31:28Z (7 years ago)
From
Joe Bright at U of Oxford <joe.bright@physics.ox.ac.uk>
J. Bright, R. Fender (Oxford), and K. P. Mooley (NRAO, Caltech; Jansky Fellow)
We have initiated the AMI short-GRB program. We observed the field of GRB 180204A (Page et al., GCN 22375) with the AMI Large Array at 15.5 GHz. Our observations on 2018 Feb 04.54, Feb 05.55, Feb 06.62 and Feb 09-11 (0.43 d, 1.44 d, 2.51 d and 5-7 d coadd post-burst) do not reveal any radio source at the XRT location (Osborne et al., GCN 22377), with 3sigma upper limits of 55 uJy, 54 uJy, 76 uJy and 63 uJy respectively.
Results from the AMI short-GRB program will be posted on the AMI-GRB database available at http://4pisky.org/ami-grb/ <http://4pisky.org/ami-grb/>. We thank the MRAO staff for scheduling these observations.