Fermi-LAT detection of the naked-eye classical nova MGAB-V207
ATel #13868; Kwan-Lok Li, Albert Kong (NTHU), Elias Aydi, Kirill Sokolovsky, Laura Chomiuk, Adam Kawash, and Jay Strader (MSU)
on 16 Jul 2020; 12:32 UT
Credential Certification: K. L. Li (lilirayhk@gmail.com)
Subjects: Gamma Ray, Nova, Transient
Using the Fermi-LAT observations, we detected an uncatalogued gamma-ray source (TS=467, equivalent to a 22-sigma detection significance; photon index = 2.1+/-0.1) at the optical position of the 5.3-mag transient MGAB-V207 discovered on 2020-07-15.590 UT
(CBET #4811; pre-discovery observation by ASAS-SN on 2020-07-08.17). In a daily search of the LAT data (from 2020-07-04 to 2020-07-15), we find that the gamma-ray emission first appeared on 2020-07-10 with F(0.1-300GeV) = 2.0+/-0.8 x 10^-7 ph/cm^2/s (TS=22). It was then undetected on 2020-07-11 (TS=3) and re-appeared in gamma-rays from 2020-07-12 to 2020-07-15 (the daily flux is around 5-7 x 10^-7 ph/cm^2/s with daily TS > 78). Based on the AAVSO data, the visual magnitude of the transient was around 4.5-5.0 mag between 2020-07-15.93 and 2020-07-16.32.
The positional coincidence of the optical/gamma-ray transient with the previously known VY Scl-type cataclysmic variable (d = 2.7 kpc
from Gaia DR2; Bailer-Jones et al. 2018) suggests that the transient is a Galactic nova, which was confirmed with SALT spectroscopy (ATel #13867). It is only the third time that a classical nova eruption is observed in a previously known white dwarf hosting binary after V407 Cyg (ATel #2487) and V392 Per (ATel #11590), which were also detected by Fermi-LAT.
Further multi-wavelength observations are strongly encouraged.
