{
  "bibcode": "2019GCN.24571....1D",
  "body": "M. Doyle (UCD, Dublin), Bozzo Enrico,\nV. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland)\nJ. Rodi (IAPS-Roma, Italy)\nA. Coleiro (APC, France)\nS. Mereghetti (INAF IASF-Milano, Italy)\n\non behalf of the INTEGRAL multi-messenger collaboration:\nhttps://www.astro.unige.ch/cdci/integral-multimessenger-collaboration\n\nUsing INTEGRAL SPI-ACS (following Savchenko\net al. 2017, A&A 603, A46) we have\nperformed a search for a prompt gamma-ray counterpart of S190517h (GCN\n24570).\n\nAt the time of the event (2019-05-17 05:51:01 UTC, hereafter T0),\nINTEGRAL was operating in nominal mode. The peak of the event\nlocalization probability was at an angle of 90 deg with respect to the\nspacecraft pointing axis. This orientation implies strongly suppressed\n(8.7% of optimal) response of ISGRI, strongly suppressed (19% of\noptimal) response of IBIS/Veto, and somewhat suppressed (61% of\noptimal) response of SPI-ACS.\n\nThe background within +/-300 seconds around the event was somewhat\nunstable (excess variance 1.9).\n\nWe have performed a search for any impulsive events in INTEGRAL SPI-\nACS (as described in Savchenko et al. 2012, A&A 541A, 122S).\n\nThe real time pipeline has found a collection of weak excesses\nin the vicinity of the event, the most prominent being at T0+37s with\na S/N of 5.4 at the timescale of 0.1s. Note that this pipeline excludes\nthe shortest 0.05s timescale since it is usually strongly polluted by CR\neffects.\n\nWe note the presence of a short time-scale variance excess in the days before\nthe event, and advise caution in interpreting this signal as astrophysical.\nFurther analysis of local noise properties will be reported elsewhere.\n\nWe do not detect any secure significant counterparts and estimate a 3-sigma\nupper limit on the 75-2000 keV fluence of 2.7e-07 erg/cm^2 for a burst\nlasting less than 1 s with a characteristic short GRB spectrum (an\nexponentially cut off power law with alpha=-0.5 and Ep=600 keV)\noccurring at any time in the interval within 300 s around T0. For a\ntypical long GRB spectrum (Band function with alpha=-1, beta=-2.5, and\nEp=300 keV), the derived peak flux upper limit is ~2.3e-07 (1.1e-08)\nerg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.",
  "circularId": 24571,
  "createdOn": 1558078275000,
  "email": "maeve.doyle.1@ucdconnect.ie",
  "subject": "LIGO/Virgo S190517h: INTEGRAL/SPI-ACS prompt observation",
  "submitter": "Maeve Doyle at U College Dublin, Ireland  <maeve.doyle.1@ucdconnect.ie>",
  "eventId": "LIGO/Virgo S190517h"
}