Fermi-LAT gamma-ray observations of SN 2024ggi
ATel #16601; G. Marti-Devesa (University and INFN Trieste), on behalf of the Fermi-LAT Collaboration.
on 26 Apr 2024; 12:18 UT
Credential Certification: Deirdre Horan (deirdre@llr.in2p3.fr)
Subjects: Gamma Ray, >GeV, Supernovae
We report an analysis of SN 2024ggi with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The SN 2024ggi was initially reported by Tonry et al. (TNS Astronomical Transient Report No. 207398) in NGC 3621 on April 11 (T0 = 2024-04-11 03:22:35.616 UTC) and later classified as a Type II supernova (Zhai et al., TNS Classification Report No. 16878). Since then, it has been monitored at several wavelengths (e.g. ATels #16586, #16587, #16588, or AstroNotes 2024-102, 2024-105).
We searched for emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (> 5 sigma) new excess emission (> 100 MeV) at the optical position of SN 2024ggi (TNS). Assuming a power-law spectrum (photon index = 2.0, fixed) for a point source at the SN 2024ggi nominal position, the flux upper limit (95% confidence) between 100 MeV and 500 GeV is < 1.5e-8 ph cm^-2 s^-1 (< 2.1e-11 erg cm^-2 s^-1) for a 14-day integration time after its discovery (2024-04-11 03:22:35 to 2024-04-25 at 03:22:35 UTC). This corresponds to a luminosity limit of < 1.1e41 erg s^-1 for a distance of 6.6 Mpc. This limit is about one order of magnitude above the hard X-ray luminosity reported by NuSTAR at T0+2 days (ATel #16587). No signal with larger fluence is detected either on shorter time scales (from T0 to T0+1, T0+3, or T0+7 days), or in a daily or weekly light curve.
Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this region will continue. For this source the Fermi-LAT contact person is Guillem Marti-Devesa (guillem.marti-devesa@ts.infn.it).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
