[vsnet-grb-info 27211] Correction to GCN 29288: NuEm-210111A: No counterpart candidates in INTEGRAL SPI-ACS observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29314
SUBJECT: Correction to GCN 29288: NuEm-210111A: No counterpart candidates in INTEGRAL SPI-ACS observation
DATE:    21/01/17 18:55:51 GMT
FROM:    Volodymyr Savchenko at ISDC,U of Geneve  <savchenk at in2p3.fr>

V. Savchenko (ISDC/UniGE, Switzerland)

on behalf of the INTEGRAL multi-messenger collaboration:
https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration

Standard INTEGRAL search for counterparts of NuEm-210111A, based on 
association with short event with known time is not adequate in this 
case since the precise time of the NuEm-210111A event is not reported 
in GCN 29287.

Suitable search for any counterparts of NuEm-210111A in INTEGRAL data 
is within the known event time interval is provided below. 

We apologise for the confusion.

=====

Using INTEGRAL data we have performed a search for 
a prompt gamma-ray counterpart of NuEm-210111A (GCN 29287).

In the time interval corresponding to the event, between 
the 2021-01-11 06:47:00 and 2021-01-11 13:06:41 UT, INTEGRAL was 
operating in nominal mode and continiously collecting data.

The event localization probability was at angles from 85 to 92 deg 
with respect to the spacecraft pointing axis, yielding stable 
response of all INTEGRAL instruments throughout the entire time 
interval of interest. This orientation implies strongly suppressed 
(~15% of optimal) response of ISGRI, strongly suppressed 
(~35% of optimal) response of IBIS/Veto, and near-optimal 
(~70% of optimal) response of SPI-ACS. Since in this case, 
 SPI-ACS is the most sensitive to the flux from the NuEm-210111A
among INTEGRAL instruments, we only report analysis of its data.

In the region of interest, the background was rather stable 
(typical excess variance 1.2).

We have performed a search for any impulsive events in INTEGRAL SPI-
ACS data (following [1]), and did not find any relevant bursts.

We estimate a 3-sigma upper limit on the 75-2000 keV
fluence of 2.6e-07 erg/cm^2 for a burst lasting less than 1 s
with a characteristic short GRB spectrum (an exponentially cut off
power law with alpha=-0.5 and Ep=600 keV) occurring at any time in the
interval within 300 s around T0. For a typical long GRB spectrum (Band
function with alpha=-1, beta=-2.5, and Ep=300 keV), the derived peak
flux upper limit is ~2.2e-07 (8e-08) erg/cm^2/s at 1 s (8 s) time
scale in 75-2000 keV energy range.


All results quoted are preliminary.

This circular is an official product of the INTEGRAL Multi-Messenger
team.

[1] Savchenko et al. 2012, A&A 541A, 122S


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