The orbital period of V458 Vulpeculae, a post double common-envelope nova

TL;DR

This study measures the orbital period of V458 Vulpeculae, revealing it as the shortest period binary with potential to be a Type Ia supernova progenitor, involving a post-common-envelope evolution.

Contribution

First precise measurement of V458 Vul's orbital period, identifying it as the shortest known for a planetary nebula central binary, and proposing its potential as a supernova progenitor.

Findings

Orbital period of 98.09647 minutes determined.

V458 Vul is the shortest-period planetary nebula central binary.

System may exceed Chandrasekhar mass, indicating supernova potential.

Abstract

We present time-resolved optical spectroscopy of V458 Vulpeculae (Nova Vul 2007 No. 1) spread over a period of 15 months starting 301 days after its discovery. Our data reveal radial velocity variations in the HeII {\lambda}5412 and HeII {\lambda}4686 emission lines. A period analysis of the radial velocity curves resulted in a period of 98.09647 \pm 0.00025 min (0.06812255 \pm 0.00000017 d) which we identify with the orbital period of the binary system. V458 Vul is therefore the planetary nebula central binary star with the shortest period known. We explore the possibility of the system being composed of a relatively massive white dwarf (M1 \gsim 1.0 Msun) accreting matter from a post-asymptotic giant branch star which produced the planetary nebula observed. In this scenario, the central binary system therefore underwent two common-envelope episodes. A combination of previous photoionisation modelling of the nebular spectra, post-asymptotic giant branch evolutionary tracks and the orbital period favour a mass of M2 \sim 0.6 Msun for the donor star. Therefore, the total mass of the system may exceed the Chandrasekhar mass, which makes V458 Vul a Type Ia supernova progenitor candidate.