{
"subject": "IceCube-200425A: No counterpart candidates in INTEGRAL SPI-ACS prompt observation",
"bibcode": "2020GCN.27652....1G",
"createdOn": 1587886995000,
"circularId": 27652,
"submitter": "Diego Gotz at CEA ",
"email": "diego.gotz@cea.fr",
"body": "D. Gotz (CEA-AIM, France), A. Lutovinov (IKI, Russia),\nV. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland),\nJ. Rodi (IAPS-Roma, Italy)\nA. Coleiro (APC, France)\nS. Mereghetti (INAF IASF-Milano, Italy)\non behalf of the INTEGRAL multi-messenger collaboration:\n\nhttps://www.astro.unige.ch/cdci/integral-multimessenger-collaboration\n\nUsing INTEGRAL/SPI-ACS realtime data (following [1]) we have performed a search for a prompt gamma-ray counterpart of IceCube-200425A (GCN 27651).\n\nAt the time of the event (2020-04-25 23:26:46 UTC, hereafter T0), INTEGRAL was operating in nominal mode. The peak of the event localization probability was at an angle of 123 deg with respect to the spacecraft pointing axis. This orientation implies strongly suppressed (5.3% of optimal) response of ISGRI, strongly suppressed (36% of optimal) response of IBIS/Veto, and somewhat suppressed (61% of optimal) response of SPI-ACS. \n\nThe background within +/-300 seconds around the event was very stable (excess variance 1.1).\n\nWe have performed a search for any impulsive events in INTEGRAL SPI-ACS data (as described in [2]).\n\nWe do not detect any significant counterparts and estimate a 3-sigma upper limit on the 75-2000 keV fluence of 2.8e-07 erg/cm^2 (within the 50% probability containment region of the source localization) 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 ~2.5e-07 (7.8e-08) erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.\n\nWe report for completeness and in order of FAP, all excesses identified in the search region. We find: 7 likely background excesses:\n\nT-T0 | scale | S/N | flux ( x 1e-06 erg/cm2/s) | FAP \n69.3 | 7 | 3.2 | 1.17 +/- 0.379 +/- 0.437 | 0.149 \n13.7 | 1 | 3.1 | 0.302 +/- 0.101 +/- 0.113 | 0.226 \n-2.22 | 0.15 | 3.1 | 0.772 +/- 0.261 +/- 0.289 | 0.272 \n-18.9 | 0.3 | 3.4 | 0.612 +/- 0.184 +/- 0.229 | 0.517 \n-264 | 2.5 | 3.5 | 2.13 +/- 0.635 +/- 0.799 | 0.708 \n-295 | 6.5 | 3.1 | 1.19 +/- 0.393 +/- 0.447 | 0.755 \n7.48 | 0.05 | 3.4 | 1.5 +/- 0.458 +/- 0.562 | 0.936 \n\nNote that FAP estimates (especially at timescales above 2s) may be possibly further affected by enhanced non-stationary local background noise. This list excludes any excesses for which FAP is close to unity.\n\nAll results quoted are preliminary.\n\nThis circular is an official product of the INTEGRAL Multi-Messenger team.\n\n[1] Savchenko et al. 2017, A&A 603, A46 \n[2] Savchenko et al. 2012, A&A 541A, 122S"
}