X-ray evolution of the nova V959 Mon suggests a delayed ejection and a non-radiative shock

Abstract

X-ray observations of shocked gas in novae can provide a useful probe of the dynamics of the ejecta. Here we report on X-ray observations of the nova V959 Mon, which was also detected in GeV gamma-rays with the Fermi satellite. We find that the X-ray spectra are consistent with a two-temperature plasma model with non-solar abundances. We interpret the X-rays as due to shock interaction between the slow equatorial torus and the fast polar outflow that were inferred from radio observations of V959 Mon. We further propose that the hotter component, responsible for most of the flux, is from the reverse shock driven into the fast outflow. We find a systematic drop in the column density of the absorber between Days 60 and 140, consistent with the expectations for such a picture. We present intriguing evidence for a delay of around 40 days in the expulsion of the ejecta from the central binary. Moreover, we infer a relatively small (a few times 10${}^{-6}$ Msun) ejecta mass ahead of the shock, considerably lower than the mass of 10${}^4$ K gas inferred from radio observations. Finally, we infer that the dominant X-ray shock was likely not radiative at the time of our observations, and that the shock power was considerably higher than the observed X-ray luminosity. It is unclear why high X-ray luminosity, closer to the inferred shock power, is never seen in novae at early times, when the shock is expected to have high enough density to be radiative.

arXiv comment15 pages, 7 figures; accepted for publication in Monthly Notices of the Royal Astronomical Society

References in corpus (36)

• On the Absorption of X-rays in the Interstellar Medium
• Atomic Data for Astrophysics. II. New Analytic Fits for Photoionization Cross Sections of Atoms and Ions
• The Relation Between Optical Extinction and Hydrogen Column Density in the Galaxy
• Updated Atomic Data and Calculations for X-ray Spectroscopy
• Line ratios for Helium-like ions: Applications to collision-dominated plasmas
• Fermi Establishes Classical Novae as a Distinct Class of Gamma-Ray Sources
• X-Ray Emitting Blast Wave from the Recurrent Nova RS Ophiuchi
• 1SXPS: A deep Swift X-ray Telescope point source catalog with light curves and spectra
• Swift X-Ray Observations of Classical Novae. II. The Super Soft Source sample
• Ionization Equilibrium Timescales in Collisional Plasmas
• Swift observations of the 2006 outburst of the recurrent nova RS Ophiuchi: I. Early X-ray emission from the shocked ejecta and red giant wind
• Binary Stellar Mergers with Marginally-Bound Ejecta: Excretion Disks, Inflated Envelopes, Outflows, and their Luminous Transients
• Binary orbits as the driver of gamma-ray emission and mass ejection in classical novae
• Shocks in nova outflows. I. Thermal emission
• The early X-ray emission from V382 Velorum (=Nova Vel 1999): An internal shock model
• Fermi LAT Gamma-ray Detections of Classical Novae V1369 Centauri 2013 and V5668 Sagittarii 2015
• The spectroscopic evolution of the $\gamma$-ray emitting classical nova Nova Mon 2012. I. Implications for the ONe subclass of classical novae
• Swift X-ray Observations of Classical Novae
• Optical Morphology, Inclination and Expansion Velocity of the Ejected Shell of Nova Monocerotis 2012
• X-ray Emission from an Asymmetric Blast Wave and a Massive White Dwarf in the Gamma-ray Emitting Nova V407 Cyg
• The 2011 Outburst of Recurrent Nova T Pyx: X-ray Observations Expose the White Dwarf Mass and Ejection Dynamics
• The 2011 Outburst of Recurrent Nova T Pyx: Radio Observations Reveal the Ejecta Mass and Hint at Complex Mass Loss
• A Luminous Be+White Dwarf Supersoft Source in the Wing of the SMC: MAXI J0158-744
• Non-Thermal Radio Emission from Colliding Flows in Classical Nova V1723 Aql
• The 7.1 hour X-ray-UV-NIR period of the gamma-ray classical Nova Monocerotis 2012
• The spectral evolution and ejecta of recurrent nova U Sco in the 2010 outburst
• A NuSTAR observation of the fast symbiotic nova V745 Sco in outburst
• Multi-Epoch Radio Imaging of gamma-ray Nova V959 Mon
• Elemental Abundances in the Ejecta of Old Classical Novae from Late-Epoch Spitzer Spectra
• NuSTAR Detection of X-rays Concurrent with Gamma Rays in the Nova V5855 Sgr
• Photometric evolution, orbital modulation and progenitor of Nova Mon 2012
• The Distance to Nova V959 Mon from VLA Imaging
• X-ray Spectroscopy of the gamma-ray Brightest Nova V906 Car (ASASSN-18fv)
• Chemical and physical parameters from X-ray high resolution spectra of the Galactic nova V959 Mon
• Possibility of a White Dwarf as the Accreting Compact Star in CI Cam (= XTE J0421+560)
• Flows and Shocks: Some Recent Developments in Symbiotic Star and Nova Research

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