Evidence for ablated flows in the shell of nova DQ Her

TL;DR

This study uses high-resolution spectra to analyze the shell of nova DQ Her, revealing an equatorial expansion, a ring with enhanced nitrogen emission, and evidence of a collimated stellar wind ablating shell fragments.

Contribution

It provides detailed spectroscopic measurements of DQ Her's shell, including velocity, distance, and evidence of ablated flows driven by a collimated stellar wind, which were not previously characterized.

Findings

Equatorial expansion velocity of 370 km/s

Distance estimate of 525 pc

Detection of ablated flows with velocities up to 900 km/s

Abstract

High-resolution longslit Halpha spectra of the shell of the old nova DQ Her have been obtained with the William Herschel Telescope using the ISIS spectrograph. An equatorial expansion velocity of 370+/-14 km/s is derived from the spectra which, in conjunction with a narrowband Halpha image of the remnant, allows a distance estimate of 525+/-28 pc. An equatorial ring which exhibits enhanced [NII] emission has also been detected and the inclination angle of the shell is found to be 86.8+/-0.2 degrees with respect to the line of sight. The spectra also reveal tails extending from the clumps in the shell, which have a radial velocity increasing along their length. This suggests the presence of a stellar wind, collimated in the polar direction, which ablates fragments of material from the clumps and accelerates them into its stream up to a terminal velocity of order 800-900 km/s.