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TITLE:   GCN CIRCULAR
NUMBER:  23448
SUBJECT: GRB 181125A: Swift detection of a burst
DATE:    18/11/25 09:07:44 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

E. Sonbas (Adiyaman Univ.), S. D. Barthelmy (GSFC),
P. D'Avanzo (INAF-OAB), A. Y. Lien (GSFC/UMBC), A. Melandri (INAF-OAB)
and K. L. Page (U Leicester) report on behalf of the Neil Gehrels
Swift Observatory Team:

At 08:54:39 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 181125A (trigger=873433).  Swift did not slew due to an
observing constraint.  The BAT on-board calculated location is 
RA, Dec 268.413, -2.613, which is 
   RA(J2000)  =  17h 53m 39s
   Dec(J2000) = -02d 36' 47"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single peak
with a duration of about 10 sec.  The peak count rate
was ~1400 counts/sec (15-350 keV), at ~1 sec after the trigger. 

Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 15:18 UT on 2019 January 31. There will thus be no XRT
or UVOT data for this trigger before this time. 

Burst Advocate for this burst is E. Sonbas (edasonbas AT yahoo.com). 
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.)

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TITLE:   GCN CIRCULAR
NUMBER:  23450
SUBJECT: GRB 181125A: Swift-BAT refined analysis 
DATE:    18/11/25 18:25:06 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

T. Sakamoto (AGU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), E. Sonbas (Adiyaman Univ.),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-142 s to T+641 s (when the burst was in the BAT FOV)
from the recent telemetry downlink, we report further analysis of BAT GRB 181125A
(trigger #873433) (Sonbas et al., GCN Circ. 23448).
The BAT ground-calculated position is
RA, Dec = 268.391, -2.634 deg which is
  RA(J2000)  =  17h 53m 33.8s
  Dec(J2000) = -02d 38' 01.2"
with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 69%.

The mask-weighted light curve shows a single-peaked structure that starts
and peaks at ~T0, and ends at ~T+11 s. T90 (15-350 keV) is 10.5 +- 5.0 sec
(estimated error including systematics).

The time-averaged spectrum from T-0.18 to T+11.24 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.57 +- 0.31.  The fluence in the 15-150 keV band is 3.3 +- 0.6 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.24 sec in the 15-150 keV band
is 1.5 +- 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/873433/BA/
////////////////////////////////////////////////////////////////////////
TITLE:   GCN CIRCULAR
NUMBER:  23451
SUBJECT: GRB 181125A: Fermi GBM observation
DATE:    18/11/25 19:15:25 GMT
FROM:    Elisabetta Bissaldi at INFN,Bari  <elisabetta.bissaldi@ba.infn.it>

E. Bissaldi (Politecnico & INFN Bari) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:


"At 08:54:41.73 UT on 25 November 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 181125A (trigger 564828886 / 181125371),
which was also detected by the Swift-BAT (Sonbas et al. 2018, GCN 23448).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight
at the GBM trigger time is 64 degrees.

The GBM light curve shows a structured emission
with a duration (T90) of about 4 s (50-300 keV).
The time-averaged spectrum from T0-1.8 s to T0+2 s is
adequately fit by a simple power law function
with index -1.8 +/- 0.1.

The event fluence (10-1000 keV) in this time interval is
(4.3 +/- 0.10)E-07 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-1.15 s in the 10-1000 keV band
is 2.0 +/- 0.2 ph/s/cm^2.


The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."