Insights into the evolution of symbiotic recurrent novae from radio synchrotron emission: V745 Scorpii and RS Ophiuchi

TL;DR

This study analyzes radio synchrotron emission from recurrent novae V745 Scorpii and RS Ophiuchi, revealing how their radio light curves evolve and what this implies about their surrounding environments and potential as supernova progenitors.

Contribution

First detailed low-frequency radio light curve analysis of V745 Scorpii, comparing it with RS Ophiuchi, and modeling the emission to understand the nova environment and evolution.

Findings

Radio emission appears sooner in successive outbursts, indicating decreasing foreground densities.

Clumpy material near the white dwarf likely originates from the accretion disk.

Uniform density gas is associated with winds from the white dwarf.

Abstract

We present observations at 610 MHz and 235 MHz using the Giant Metrewave Radio Telescope (GMRT) of the recurrent nova V745 Scorpii which recorded its last outburst on 6 February 2014. This is the second symbiotic recurrent nova whose light curve at low frequencies has been followed in detail, the first being RS Ophiuchi in 2006. We fitted the 610 MHz light curve by a model of synchrotron emission from an expanding shell being modified by radiative transfer effects due to local absorbing gas consisting of a uniformly distributed and a clumpy component. Using our model parameters, we find that the emission at 235 MHz peaked around day 35 which is consistent with our GMRT observations. The two main results of our study are: (1) The radio emission at a given frequency is visible sooner after the outburst in successive outbursts of both V745 Scorpii and RS Ophiuchi. The earlier detection of radio emission is interpreted to be caused by decreasing foreground densities. (2) The clumpy material, if exists, is close to the white dwarf and can be interpreted as being due to the material from the hot accretion disk. The uniform density gas is widespread and attributed to the winds blown by the white dwarf. We present implications of these results on the evolution of both novae. Such studies alongwith theoretical understanding have the potential of resolving several outstanding issues such as why all recurrent novae are not detectable in synchrotron radio and whether recurrent novae are progenitor systems of type 1a supernova.