X-ray spectroscopy of the γ-ray brightest nova V906 Car (ASASSN-18fv)

Kirill V. Sokolovsky, Koji Mukai, Laura Chomiuk, Raimundo Lopes De Oliveira, Elias Aydi, Kwan Lok Li, Elad Steinberg, Indrek Vurm, Brian D. Metzger, Adam Kawash, Justin D. Linford, Amy J. Mioduszewski, Thomas Nelson, Jan Uwe Ness, Kim L. Page, Michael P. Rupen, Jennifer L. Sokoloski, Jay Strader

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Shocks in γ-ray emitting classical novae are expected to produce bright thermal and non-thermal X-rays. We test this prediction with simultaneous NuSTAR and Fermi/LAT observations of nova V906 Car, which exhibited the brightest GeV γ-ray emission to date. The nova is detected in hard X-rays while it is still γ-ray bright, but contrary to simple theoretical expectations, the detected 3.5-78 keV emission of V906 Car is much weaker than the simultaneously observed >100 MeV emission. No non-thermal X-ray emission is detected, and our deep limits imply that the γ-rays are likely hadronic. After correcting for substantial absorption (NH ≈ 2 × 1023 cm-2), the thermal X-ray luminosity (from a 9 keV optically thin plasma) is just ∼2 per cent of the γ-ray luminosity. We consider possible explanations for the low thermal X-ray luminosity, including the X-rays being suppressed by corrugated, radiative shock fronts or the X-rays from the γ-ray producing shock are hidden behind an even larger absorbing column (NH > 1025 cm-2). Adding XMM-Newton and Swift/XRT observations to our analysis, we find that the evolution of the intrinsic X-ray absorption requires the nova shell to be expelled 24 d after the outburst onset. The X-ray spectra show that the ejecta are enhanced in nitrogen and oxygen, and the nova occurred on the surface of a CO-type white dwarf. We see no indication of a distinct supersoft phase in the X-ray light curve, which, after considering the absorption effects, may point to a low mass of the white dwarf hosting the nova.

Original languageEnglish
Pages (from-to)2569-2585
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Volume497
Issue number3
DOIs
Publication statusPublished - 2020 Sep 1

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Fingerprint Dive into the research topics of 'X-ray spectroscopy of the γ-ray brightest nova V906 Car (ASASSN-18fv)'. Together they form a unique fingerprint.

Cite this