GCN Circular 34079
Subject
INTEGRAL upper limit on any GRB associated with ZTF23aaoohpy/AT2023lcr
Event
Date
2023-06-25T15:10:21Z (2 years ago)
From
Volodymyr Savchenko at ISDC, University of Geneva; LASTRO, EPFL <volodymyr.savchenko@unige.ch>
Volodymyr Savchenko (ISDC, University of Geneva; LASTRO, EPFL), Carlo Ferrigno (ISDC, University of Geneva), Antonio Martin-Carrillo (UCD), Sandro Mereghetti (IASF-Milano, INAF)
Using INTEGRAL serendipitous all-sky observations we searched for GRB associated with ZTF23aaoohpy/AT2023lcr (GCN #34022).
Between last non-detection at 2023-06-17T23:50:30 (T1) and first detection 2023-06-18T01:27:41 (T2) by GOTO (GCN #34023) INTEGRAL was observing the whole sky while maintaining stable attitude, and ZTF23aaoohpy/AT2023lcr was at an offaxis angle from 77.1 to 78.7 deg. This orientation implies optimal response of SPI-ACS and reduced response of other INTEGRAL all-sky instruments.
Background conditions were stable during the time interval of interest, with excess variance of 1.2 (1 s timescale). The background is also near its long-term minimum, typical for this phase of solar cycle.
No IBAS triggers occurred between T1 and T2. Following [1] we performed an offline-search for any GRB-like events between T1 and T2. In this time interval we did not find any relevant excesses.
We set a 3-sigma upper limit on the 75-2000 keV fluence of 1.7e-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). 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 ~1.5e-07 (5.6e-08) erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.
In addition, the location of ZTF23aaoohpy/AT2023lcr was serendipitously in FoV of INTEGRAL pointing instruments during slew between 2023-06-18T05:25:38 (T2+3.9 h) and 2023-06-18T05:35 (T2+4.1 h). Using collimating properties of IBIS/ISGRI telescope, we set an rough upper limit on average flux in this time interval at the level of 1.9e-10 erg/cm2/s (28-80 keV energy range).
All the quoted values are preliminary.
SPI-ACS lightcurve for this event can be obtained through MMODA: https://www.astro.unige.ch/mmoda/?T1=2023-06-17T23:50:30&T2=2023-06-18T01:27:41&T_format=isot&data_level=ordinary&instrument=spi_acs&product_type=spi_acs_lc&time_bin=2&time_bin_format=sec
[1] Savchenko+ 2012, A&A