TITLE:   GCN CIRCULAR
NUMBER:  33551
SUBJECT: GRB 230307A: Bad Time Intervals for Fermi GBM data
DATE:    23/04/01 01:57:34 GMT
FROM:    Sarah Dalessi at UAH  <sd0104@uah.edu>

S. Dalessi (UAH) reports on behalf of the Fermi GBM Team:

"The Fermi Gamma-ray Burst Monitor data for GRB 230307A has a period
of bad time intervals, affecting all data types. At particularly high
rates the TTE data has data loss due to the bandwidth limit between
the instrument and the spacecraft. CTIME and CSPEC data experience
deadtime but do not experience similar losses due to electronics
bandwidth. However, at particularly high rates both CTIME and CSPEC
are affected by pulse pile-up, which will distort the spectra (see
https://arxiv.org/abs/2303.14172). For CTIME and CSPEC, pulse pile-up
occurs for GRB pulses during the time interval of 2.5-11.0 seconds for
the BGO detector B1 and the interval 2.5-7.5 seconds for the NaI
detector Na, with T0 referenced to the GBM trigger time. The TTE
losses happen within these time intervals, with packet losses for
high-rate GRB pulses between 3 to 7 seconds. We recommend the
exclusion of these time intervals for GBM analysis of this burst, as
well as caution in using bins adjacent to these selections.


Additionally, due to the orientation of the burst, we recommend only
using BGO detector B1 and NaI detector Na for analysis of this burst.
All the other detectors either have >60deg source angles or are
blocked by the spacecraft itself."