Fermi-LAT Observations of V549 Vel 2017: A Subluminous Gamma-Ray Nova?

Kwan Lok Li, Franz Josef Hambsch, Ulisse Munari, Brian D. Metzger, Laura Chomiuk, Andrea Frigo, Jay Strader

Research output: Contribution to journalArticlepeer-review

Abstract

We report on the Fermi Large Area Telescope detection (with ≈5.7σ significance) as well as the multiwavelength analysis of the 2017 nova eruption V549 Vel. Unlike the recent shock-powered novae ASASSN-16ma and V906 Car, the optical and γ-ray light curves of V549 Vel show no correlation, likely implying relatively weak shocks in the eruption. Gaia detected a candidate progenitor of V549 Vel and found a parallax measurement of ϖ = 1.91 ± 0.39 mas, equivalent to a mode distance of d ≈ 560 pc (90% credible interval of 380-1050 pc). The progenitor was also observed by the 2MASS and WISE surveys. When adopting the Gaia distance, the spectral energy distribution of the progenitor is close to that of a G-type star. The Swift X-Ray Telescope detected the supersoft X-ray emission of the nova (kT = 30-40 keV) since day 236, and the inferred blackbody size is comparable to that of other novae assuming d ≈ 560 pc (i.e., R bb ∼ 5 × 108 cm). However, there is also an unknown astrometric excess noise of i = 3.2 mas found in the Gaia data, and the inferred distance becomes controversial. If the Gaia distance is accurate, the γ-ray luminosity of V549 Vel will be as low as L γ ∼ 4 × 1033 erg s-1, making it the least luminous γ-ray nova known so far. This may imply that the shock properties responsible for the γ-ray emission in V549 Vel are different from those of the more luminous events. If the nova is located farther away, it is likely a symbiotic system with a giant companion as the observed progenitor.

Original languageEnglish
Article number114
JournalAstrophysical Journal
Volume905
Issue number2
DOIs
Publication statusPublished - 2020 Dec 20

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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