{
  "eventId": "LIGO/Virgo/KAGRA S250206dm",
  "circularId": 39183,
  "subject": "LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations",
  "createdOn": 1738893853622,
  "bibcode": "2025GCN.39183....1M",
  "submitter": "oindabimukherjee@gmail.com",
  "submittedHow": "web",
  "body": "O. Mukherjee (USRA) and R. Hamburg (USRA) report on behalf of the Fermi-GBM Team:\n\nFor S250206dm (GCN 39175; GCN 39178) and using the updated Bilby skymap, Fermi-GBM was observing 35.7% of the localization probability at event time.\n\nThere was no Fermi-GBM onboard trigger around the event time of the LIGO/Virgo/KAGRA (LVK) detection of GW trigger S250206dm. An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around merger time, and also identified no counterpart candidates.\n\nPart of the LVK localization region is behind the Earth for Fermi, located at an RA=24.7, Dec=-4.2 with a radius of 67.9 degrees. We therefore set upper limits on impulsive gamma-ray emission for the GW localization region visible to Fermi at merger time. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395, we set the following 3 sigma flux upper limits over 10-1000 keV, weighted by GW localization probability (in units of 10^-7 erg/s/cm^2):\nTimescale  Soft  Normal Hard \n------------------------------------\n0.128 s:   1.5   2.4    5.1\n1.024 s:   0.44  0.72   1.3\n8.192 s:   0.08  0.17   0.31\n\nAssuming the median luminosity distance of 358.7 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^50 erg/s):\nTimescale  Soft   Normal   Hard \n------------------------------------\n0.128s:    0.71   1.02     2.95\n1.024s:    0.09   0.14     0.47\n8.192s:    0.02   0.02     0.04",
  "format": "text/plain"
}