[vsnet-grb-info 19003] GRB 170127C: Fermi-LAT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20544
SUBJECT: GRB 170127C: Fermi-LAT detection
DATE:    17/01/27 17:11:28 GMT
FROM:    Magnus Axelsson at Stockholm U.  <magaxe at kth.se>

E. Moretti (MPP), G. Vianello (Stanford Univ.), E. Bissaldi (INFN and Politecnico Bari), J. Racusin (NASA/GSFC) and M. Axelsson (Stockholm Univ. and KTH Stockholm) report on behalf of the Fermi-LAT team:

On January, 27, 2017 Fermi-LAT detected high-energy emission from GRB 170127C, which was also detected by Fermi-GBM starting at T0 = 01:35:47.79 (trigger 507173752 / 170127067; Bissaldi et al. GCN 20543).


The best LAT on-ground location is found to be

RA, Dec =  339.3, -63.9 (J2000)

with an error radius of 0.4 deg (90 % containment, statistical error only).

The location was outside the LAT field-of-view at the time of the trigger. The event triggered an autonomous repoint of the spacecraft, causing the location to enter the field-of-view around 300s later.

The data from the Fermi-LAT show a significant increase in the event rate that is spatially correlated with the trigger with high significance.

The highest-energy photon is a 500 MeV event which is observed 2890 seconds after the GBM trigger. A total of 5 photons above 100 MeV were detected up to 4000s after the trigger.

A Swift ToO has been requested for this burst.


The Fermi-LAT point of contact for this burst is Elena Moretti (moretti at mpp.mpg.de<mailto:moretti at mpp.mpg.de>).


The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater
than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and
many scientific institutions across France, Italy, Japan and Sweden.