{
  "bibcode": "2019GCN.26556....1M",
  "body": "*LIGO/Virgo S191222n: No counterpart candidates in Fermi-LAT observations *\n\nE. Moretti (IFAE, Barcelona), M. Crnogorcevic (Univ. of Maryland &\nNASA/GSFC), F. Longo (UniTS and INFN, Trieste) and M. Axelsson (KTH &\nStockholm Univ.) report on behalf of the Fermi-LAT Collaboration:\n\nWe have searched data collected by the Fermi Large Area Telescope (LAT) on\nDec 22, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission\nin spatial/temporal coincidence with the LIGO/Virgo trigger S191222n (GCN\n26543).\n\nWe define \"instantaneous coverage\" as the integral over the region of the\nLIGO probability map that is within the LAT field of view at a given time,\nand \"cumulative coverage\" as the integral of the instantaneous coverage\nover time.\n\nThe Fermi Gamma-ray Space Telescope was passing through the South\nAtlantic Anomaly (SAA) at the time of the trigger (T0\n= 2019-12-22 03:35:37.118 UTC). During SAA passages both the LAT and the\nGamma-ray Burst Monitor (GBM) do not collect data due to the high charged\nparticle background in this region. The LAT resumed taking data upon\nexiting the SAA at roughly T0 + 1ks. At that time the instantaneous\ncoverage was 55% of the LIGO probability map, and reached cumulative\ncoverage of 90% after ~5 ks. The remaining area was not observed within 10\nks following the trigger time of the event.\n\nWe performed a search for a transient counterpart within the observed\nregion of the 90% contour of LIGO map in a fixed time window from T0 + 1ks\nto T0 + 10 ks. No significant new sources are found.\n\nWe also performed a search which adapted the time interval of the analysis\nto the exposure of each region of the sky, and no additional excesses were\nfound.\n\nEnergy flux upper bounds for the fixed time interval between 100 MeV and 1\nGeV for this search vary between 1.4e-10 and 5.7e-08 [erg/cm^2/s].\n\nThe Fermi-LAT point of contact for this event is Milena Crnogorcevic (\nmcrnogor@astro.umd.edu).\n\nThe Fermi-LAT is a pair conversion telescope designed to cover the energy\nband from 20 MeV to greater than 300 GeV. It is the product of an\ninternational collaboration between NASA and DOE in the U.S. and many\nscientific institutions across France, Italy, Japan and Sweden.\n\n-- \n\n\n\n\n*Institut de F��sica d'Altes Energies (IFAE) Universitat Aut��noma de\nBarcelona, Edifici Cn 08193 Bellaterra (Barcelona), Spain Tel:+34 931 70 27\n10Av��s - Aviso - Legal Notice - (LOPD) - http://legal.ifae.es\n<http://legal.ifae.es>*\n\n-- \nAv��s -\nAviso - Legal Notice - (LOPD) - http://legal.ifae.es \n<http://legal.ifae.es/>",
  "circularId": 26556,
  "createdOn": 1577028374000,
  "email": "moretti@ifae.es",
  "subject": "LIGO/Virgo S191222n: No counterpart candidates in Fermi-LAT observations",
  "submitter": "Elena Moretti at IFAE,Barcelona  <moretti@ifae.es>",
  "eventId": "LIGO/Virgo S191222n"
}