Fermi-LAT Gamma-ray Detection of the Recurrent Nova RS Oph
ATel #14834; C. C. Cheung (NRL), S. Ciprini (ASI Space Science Data Center, Roma, & INFN Roma Tor Vergata, Italy), T. J. Johnson (GMU, resident at NRL), on behalf of the Fermi Large Area Telescope Collaboration
on 9 Aug 2021; 05:05 UT
Credential Certification: Teddy Cheung (Teddy.Cheung@nrl.navy.mil)
Subjects: Gamma Ray, >GeV, Nova, Transient
Referred to by ATel #: 14838, 14840, 14844, 14845, 14846, 14848, 14849, 14850, 14851, 14855, 14857, 14858, 14860, 14863, 14864, 14866, 14868, 14882, 14885, 14886, 14894, 14895, 14909, 14972, 14974, 15169
The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope, has independently detected a transient gamma-ray source positionally consistent with the newly detected optical outburst of the recurrent nova RS Oph on 2021 Aug 8, 22:20 UT reported by K. Geary (vsnet-alert 26131, http://ooruri.kusastro.kyoto-u.ac.jp/mailarchive/vsnet-alert/26131 ), with an estimated visual magnitude of 5.0. Its previous outburst was in 2006, with an average recurrence time of ~15 years over eight recorded historical outbursts (Schaefer 2010, ApJS, 187, 275).
Preliminary analysis indicates its first detection (with ~6-sigma signficance) in the last 6-hr interval (18:00-24:00 UT) of 2021 Aug 8, coinciding with the optical discovery, with a (E >100 MeV) flux of (2.4 +/- 0.8) x 10^-6 photons cm^-2 s^-1 and photon index of 2.3 +/- 0.3 (statistical uncertainties only). The gamma-ray onset coincident with the time of the optical discovery is similar to the case of the Fermi-LAT detection of a similar symbiotic-like recurrent nova V407 Cyg 2010 (Abdo et al. 2010 Sci 329, 817; ATel #2487).
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the ongoing activity of this source, we encourage multi-wavelength observations. For this source the Fermi LAT contact is C.C. Cheung (Teddy.Cheung@nrl.navy.mil).
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.
