TITLE: GCN CIRCULAR NUMBER: 31012 SUBJECT: GRB 211027A: Fermi GBM Final Real-time Localization DATE: 21/10/27 06:02:00 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 05:51:52 UT on 27 Oct 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 211027A (trigger 657006717.695746 / 211027244).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 278.6, Dec = 19.0 (J2000 degrees, equivalent to J2000 18h 34m, 19d 00'), with a statistical uncertainty of 6.1 degrees.

The angle from the Fermi LAT boresight is 24.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn211027244/q...

The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn211027244/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn211027244/q...