- GCN Circular #22618
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a series of observations, tiled on the sky, of the
IPN GRB 180409A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00069
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the IPN event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN Circular
after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
- GCN Circular #22619
K. Hurley, on behalf of the IPN,
I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,
A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, D.Svinkin,
and T. Cline on behalf of the Konus-Wind team,
V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa,
and A. Goldstein, on behalf of the Fermi GBM team,
A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, and
W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:
A long-duration GRB 180409A was detected by Fermi (GBM), Konus-Wind,
INTEGRAL (SPI-ACS), Mars-Odyssey (HEND), and Swift (BAT) at about 29899 s
UT (08:18:19).
The burst was outside the coded field of view of the BAT.
We have triangulated it to a preliminary, 3 sigma error box whose
coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
175.842 (11h 43m 22s) +36.308 (+36d 18' 30")
Corners:
175.961 (11h 43m 51s) +35.973 (+35d 58' 21")
176.118 (11h 44m 28s) +36.645 (+36d 38' 43")
175.721 (11h 42m 53s) +36.644 (+36d 38' 37")
175.567 (11h 42m 16s) +35.969 (+35d 58' 10")
---------------------------------------------
The error box area is 772 sq. arcmin, and its maximum
dimension is 49 arcmin (the minimum one is 19 arcmin).
The Sun distance was 131 deg.
This box may be improved.
A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB180409_T29904/IPN/
Swift ToO has been approved (Evans, GCN Circ. 22618).
The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.
- GCN Circular #22621
D. Frederiks, S. Golenetskii, R.Aptekar, M. Ulanov, D. Svinkin,
A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline,
on behalf of the Konus-Wind team, report:
The long GRB 180409A (IPN Triangulation: Hurley et al., GCN 22619)
triggered Konus-Wind at T0=3D29904.770 s UT (08:18:24.770)
The burst light curve shows a multi-peaked structure,
which started at ~T0-3 s and peaked at ~T0+9.4 s.
The total duration of the burst is ~20 s.
The emission is seen up to ~3 MeV.
As observed by Konus-Wind, the burst had a fluence of
(8.8 =B1 1.3)x10^-6 erg/cm2 and a 64-ms peak energy flux,
measured from T0+9.408, of (9.9 =B1 1.5)x10^-6 erg/cm2
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+17.920 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha =3D -0.96 (-0.09,+0.10),
the high energy photon index beta =3D -3.1 (-6.9,+0.42),
the peak energy Ep =3D 180 (-14,+15) keV,
chi2 =3D 67/97 dof.
The spectrum near the peak count rate (measured from T0+7.936
to T0+9.728 s) is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha =3D -0.50 (-0.13,+0.20),
the high energy photon index beta =3D -3.5 (-6.5,+0.8),
the peak energy Ep =3D 266 (-35,+26) keV,
chi2 =3D 81/78 dof.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180409_T29904/
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
- GCN Circular #22625
A. Tohuvavohu (PSU), S. J. LaPorte (PSU), A.P. Beardmore (U.
Leicester), S.L. Gibson (U. Leicester), P. D'Avanzo (INAF-OAB), V.
D'Elia (ASDC), A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU), B. Sbarufatti
(INAF-OAB/PSU), and P.A. Evans (U. Leicester) report on behalf of the
Swift-XRT team:
Swift-XRT has performed follow-up observations of the IPN-detected
burst GRB 180409A in a series of observations tiled on the sky. The
total exposure time is 3.5 ks, distributed over 4 tiles; the maximum
exposure at a single sky location was 2.4 ks. The data were collected
between T0+53.5 ks and T0+71.6 ks, and are entirely in Photon Counting
(PC) mode.
One uncatalogued X-ray source has been detected, it is below the RASS
limit and shows no definitive signs of fading. Therefore, at the
present time we cannot confirm this as the afterglow. Details of this
source are given below:
Source 1:
RA (J2000.0): 175.8434 = 11:43:22.42
Dec (J2000.0): +36.2335 = +36:14:00.6
Error: 3.6 arcsec (radius, 90% conf. [Enhanced position])
Count-rate: 0.0258 +/- 0.0068 ct s^-1
Distance: 268 arcsec from IPN position.
Flux: (8.3 +/- 2.2)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00069.
This circular is an official product of the Swift-XRT team.
- GCN Circular #22626
E. Bissaldi (Politecnico & INFN Bari) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 08:18:18.67 UT on 9 April 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180409A (trigger 544954703 / 180409346),
which was triangulated by IPN (Hurley et al., GCN 22619) and was also
detected by Konus (Frederiks et al., GCN 22621).
The on-ground calculated location, using the GBM trigger data, is
RA = 178.18, DEC = +36.050 (J2000 degrees),
with an uncertainty of 1 degree (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which we have characterized as a core-plus-tail model, with 90% of
GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg
systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).
The angle from the Fermi LAT boresight at the GBM trigger time is 71 degrees.
The GBM light curve consists of multiple peaks
with a duration (T90) of about 13 s (50-300 keV).
The time-averaged spectrum from T0-0.5 s to T0+15 s is
best fit by a Band function with Epeak = 151 +/- 5 keV,
alpha = -0.85 +/- 0.03, and beta = -2.33 +/- 0.05.
The event fluence (10-1000 keV) in this time interval is
(2.87 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+10.1 s in the 10-1000 keV band
is 41 +/- 1 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
- GCN Circular #22635
A. Yoshida, T. Sakamoto, V. Pal'shin, Y. Kawakubo, A. Tezuka, S. Matsukawa,
H. Onozawa (AGU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), I. Takahashi (IPMU),
Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U),
W. Ishizaki (ICRR), M. L. Cherry (LSU), S. Ricciarini (U of Florence),
A. V. Penacchioni, P. S. Marrocchesi (U of Siena)
and the CALET collaboration:
The long GRB 180409A (IPN triangulation: Hurley et al., GCN circ. 22619;
Konus-Wind detection: Frederiks et al., GCN circ. 22621;
Fermi-GBM detection: Bissaldi and Meegan GCN circ. 22626) triggered
the CALET Gamma-ray Burst Monitor (CGBM) at 08:18:17.669 UTC on 9 April 2018.
The burst signal was seen by all CGBM detectors.
The burst light curve shows several partially overlapped short pulses
which start at T+3.0 sec, peaks at T+12.3 sec and ends at T+14.9 sec.
The T90 and the T50 durations measured by the SGM data are 10.6 +- 0.7 sec
and 5.9 +- 1.8 sec (40-1000 keV), respectively.
The ground processed light curve is available at
http://cgbm.calet.jp/cgbm_trigger/ground/1207297067/
The CALET data used in this analysis are provided by the Waseda CALET
Operation Center located at the Waseda University.
- GCN Circular #22643
A. Tohuvavohu (PSU), S. J. LaPorte (PSU), A.P. Beardmore (U.
Leicester), S.L. Gibson (U. Leicester), P. D'Avanzo (INAF-OAB), V.
D'Elia (ASDC), A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU), B. Sbarufatti
(INAF-OAB/PSU) and P.A. Evans (U. Leicester) report on behalf of the
Swift-XRT team:
Swift-XRT has conducted further observations of the field of the
IPN-detected burst GRB 180409A (Yoshida et al. GCN Circ. 22635). The
observations now extend from T0+53.4 ks to T0+455.1 ks. The source
previously reported by Tohuvavohu et al. (GCN Circ. 22625), "Source 1",
is fading with 3-sigma significance, and is therefore likely the GRB
afterglow. Using 1887 s of PC mode data and 2 UVOT images, we find an
enhanced XRT position (using the XRT-UVOT alignment and matching UVOT
field sources to the USNO-B1 catalogue): RA, Dec = 175.84306, +36.23354
which is equivalent to:
RA (J2000): 11h 43m 22.33s
Dec(J2000): +36d 14' 00.8"
with an uncertainty of 3.1 arcsec (radius, 90% confidence). This
position is 4.5 arcmin from the IPN position.
The light curve can be modelled with a power-law decay with a decay
index of alpha=1.0 (+/-0.3).
The results of the XRT-team automatic analysis of the likely afterglow
are at http://www.swift.ac.uk/xrt_products/TILED_GRB00069/Source1.php.
The results of the full analysis of the tiled XRT observations are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00069.
This circular is an official product of the Swift-XRT team.
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