GRB 200517A
GCN Circular 27750
Subject
GRB 200517A: MAXI/GSC detection
Date
2020-05-17T12:46:55Z (5 years ago)
From
Motoko Serino at RIKEN/MAXI <motoko@crab.riken.jp>
M. Niwano (Tokyo Tech), H. Negoro (Nihon U.), M. Serino (AGU),
M. Nakajima, M. Aoki, K. Kobayashi, R. Takagi, K, Asakura, K, Seino, S. Mokumoto (Nihon U.),
T. Mihara, C. Guo, Y. Zhou, T. Tamagawa, M. Matsuoka (RIKEN),
T. Sakamoto, S. Sugita, H. Nishida, A. Yoshida (AGU),
Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, Y. Okamoto, S. Kitakoga (Chuo U.),
M. Shidatsu (Ehime U.),
N. Kawai, R. Adachi (Tokyo Tech),
S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, M. Tominaga, T. Nagatsuka (JAXA),
Y. Ueda, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake (Kyoto U.),
H. Tsunemi (Osaka U.),
M. Yamauchi, K. Kurogi, K. Miike (Miyazaki U.),
T. Kawamuro (NAOJ),
K. Yamaoka (Nagoya U.),
Y. Kawakubo (LSU),
M. Sugizaki (NAOC)
report on behalf of the MAXI team:
The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 11:27:21 UT .
We obtained the source position at
(R.A., Dec) = (17.230 deg, -50.745 deg) = (01 08 55, -50 44 41) (J2000)
with a rectangular error box with the following corners:
(15.411, -49.816) deg = (01 01 38, -49 48 57) (J2000)
(15.002, -50.346) deg = (01 00 00, -50 20 45) (J2000)
(18.572, -51.401) deg = (01 14 17, -51 24 03) (J2000)
(18.949, -50.859) deg = (01 15 47, -50 51 32) (J2000)
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 198 +- 33 mCrab
(4.0-10.0keV, 1 sigma error).
There was no significant excess flux in the previous transit at 09:54 UT
with an upper limit of 20 mCrab.
GCN Circular 27751
Subject
GRB 200517A: Tiled Swift observations
Date
2020-05-17T13:37:18Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
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
MAXI GRB 200517A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00090
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 MAXI 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 27754
Subject
GRB 200517A: Swift-XRT afterglow detection
Date
2020-05-18T15:06:08Z (5 years ago)
From
Jeffrey Gropp at PSU <jdg44@psu.edu>
B. Sbarufatti (PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester),
K.L. Page (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo
(INAF-OAB), M.G. Bernardini (INAF-OAB), J. D. Gropp (PSU) and P.A.
Evans (U. Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the MAXI-detected
burst GRB 200517A (Niwano et al. GCN Circ. 27750) in a series of
observations tiled on the sky. The total exposure time is 1.1 ks,
distributed over 7 tiles; the maximum exposure at a single sky location
was 388 s. The data were collected between T0+8.0 ks and T0+8.3 ks, and
are entirely in Photon Counting (PC) mode.
An uncatalogued X-ray source is detected and is above the RASS limit,
and is therefore likely the GRB afterglow. Using 366 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 = 17.69837, -50.92242 which is equivalent to:
RA (J2000): 01h 10m 47.61s
Dec(J2000): -50d 55' 20.7"
with an uncertainty of 3.3 arcsec (radius, 90% confidence). This
position is 20.7 arcmin from the MAXI position. We cannot determine at
the present time whether the source is fading.
The results of the XRT-team automatic analysis of the likely afterglow
are at https://www.swift.ac.uk/xrt_products/TILED_GRB00090/Source1.php.
The results of the full analysis of the tiled XRT observations are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00090.
This circular is an official product of the Swift-XRT team.
GCN Circular 27758
Subject
Fermi GBM Sub-Threshold Detection of GRB 200517A
Date
2020-05-19T16:46:54Z (5 years ago)
From
Cori Fletcher at USRA <cfletcher@usra.edu>
C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team:
MAXI/GSC detected GRB 200517A at 11:27:21 UT (GCN 27750). There was no
Fermi-GBM onboard trigger around the event.
An automated, blind search for short gamma-ray bursts below the onboard
triggering threshold in Fermi-GBM identified no counterparts.
The GBM targeted search [1], the most sensitive, coherent search for
GRB-like signals identified a transient most significantly on the 8.192 s
timescale, with a log likelihood ratio of 13 and a location consistent with
the MAXI/GSC event. The GBM targeted search event was found with the highest
significance with a "soft" spectrum (Band function with Epeak=70 keV, alpha=-1.9,
beta=-3.7) for a GRB.
[1] Goldstein et al. 2019 arXiv:1903.12597
GCN Circular 27775
Subject
GRB 200517A: Swift-XRT Confirmation of afterglow
Date
2020-05-21T16:04:22Z (5 years ago)
From
Jeffrey Gropp at PSU <jdg44@psu.edu>
J. Gropp (PSU) reports on behalf of the Swift-XRT team:
We provide an update on the XRT light curve evolution of the candidate
X-ray afterglow of GRB 200517A (GCN Circ. 27750).
The XRT light curve now comprises data up to 300 ks from the MAXI trigger
(GCN Circs. 27750). There is a firm indication of fading with respect to
the first observation as reported previously (GCN Circ 27754), with a decay
index of 1.04 (+0.21, -0.18). We thus confirm that this is indeed the
afterglow of GRB 200517A.
The latest results can be viewed via:
https://www.swift.ac.uk/xrt_curves/00020993/
This circular is an official product of the Swift-XRT team.