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TITLE:   GCN CIRCULAR
NUMBER:  26581
SUBJECT: GRB 191225B: Fermi GBM Final Real-time Localization
DATE:    19/12/25 17:47:56 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 17:37:51 UT on 25 Dec 2019, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 191225B (trigger 598988276.867438 / 191225735).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 145.8, Dec = -7.2 (J2000 degrees, equivalent to J2000 09h 43m, -7d 12'), with a statistical uncertainty of 2.8 degrees.

The angle from the Fermi LAT boresight is 61.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn191225735/quicklook/glg_skymap_all_bn191225735.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn191225735/quicklook/glg_healpix_all_bn191225735.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn191225735/quicklook/glg_lc_medres34_bn191225735.gif

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TITLE:   GCN CIRCULAR
NUMBER:  26583
SUBJECT: GRB 191225B: BALROG localization (Fermi Trigger 598988276 / GRB 191225735)
DATE:    19/12/25 18:02:04 GMT
FROM:    Jochen Greiner at MPE,Garching  <jcg@mpe.mpg.de>

B. Biltzinger, F. Kunzweiler, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
598988276 at 17:37:51 on 25 Dec. 2019 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 144.1+/-1.7 deg
Decl.(2000.0) = -7.2+/-0.8 deg
We estimate an additional systematic error of 2 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB191225735/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB191225735/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB191225735/json