[vsnet-grb-info 22071] LIGO/Virgo S190425z: INTEGRAL SPI-ACS prompt observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24170
SUBJECT: LIGO/Virgo S190425z: INTEGRAL SPI-ACS prompt observation
DATE:    19/04/25 10:27:09 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

P. Minaev, A. Pozanenko, S. Grebenev, I. Chelovekov on behalf of IKI GRB FuN collaboration report:

We used public data of SPI-ACS to perform a search for possible EM-counterpart of LIGO/Virgo S190425z. Here we report preliminary analysis of SPI-ACS data available. After trigger time of S190425z (G330561) we found two pulses with time since trigger, duration, significance and fluence (in counts) above a background as following

+0.5 s, 0.4 s, 3.6 sigma, 900 +/- 250
+6 s, 1 s, 4 sigma, 1620 +/- 400

The significance of the second pulse is somewhat larger in comparison with reported early in GCN 24169 (Martin-Carillo et al.)
We estimated fluence of first and second pulses in the energy range  75 - 1000 keV as (9.0 +- 0.3) * 10^-8 erg/cm2 and (1.6 +- 0.4 ) * 10^-7
erg/cm2, respectively. It corresponds to E_iso (2.5 +/- 0.7) * 10^47 erg  and  (4.5 +/- 1.1) * 10^47 erg assuming distance 154.6 Mpc.

We do no found any extended emission up to T0+270 s after trigger.
The boresight of the center of the eror box localization (RA, Dec 16 10
18.75, 22 49 53.0609) is about 31 degrees.