Bow-shocks, nova shells, disc winds and tilted discs: The Nova-Like V341 Ara Has It All

TL;DR

V341 Ara is a nearby, bright nova-like system with a surrounding nebula, bow-shock, and tilted accretion disc, offering insights into nova eruptions, disc winds, and system dynamics through comprehensive multi-wavelength observations.

Contribution

This study provides the first detailed multi-wavelength analysis of V341 Ara, revealing its unique features such as super-orbital variations, a tilted disc, and a potential historical nova event.

Findings

Detection of super-orbital variations with 10-16 day period

Identification of a negative superhump indicating a tilted disc

Constraints on wind mass-loss rate from bow-shock emission

Abstract

V341 Ara was recently recognised as one of the closest (d ~ 150 pc) and brightest (V~ 10) nova-like cataclysmic variables. This unique system is surrounded by a bright emission nebula, likely to be the remnant of a recent nova eruption. Embedded within this nebula is a prominent bow-shock, where the system's accretion disc wind runs into its own nova shell. In order to establish its fundamental properties, we present the first comprehensive multi-wavelength study of the system. Long-term photometry reveals quasi-periodic, super-orbital variations with a characteristic time-scale of 10-16 days and typical amplitude of ~1 mag. High-cadence photometry from TESS reveals for the first time both the orbital period and a "negative superhump" period. The latter is usually interpreted as the signature of a tilted accretion disc. We propose a recently developed disc instability model as a plausible explanation for the photometric behaviour. In our spectroscopic data, we clearly detect anti-phased absorption and emission line components. Their radial velocities suggest a high mass ratio, which in turn implies an unusually low white dwarf mass. We also constrain the wind mass-loss rate of the system from the spatially resolved [O iii] emission produced in the bow-shock; this can be used to test and calibrate accretion disc wind models. We suggest a possible association between V341 Ara and a "guest star" mentioned in Chinese historical records in AD1240. If this marks the date of the system's nova eruption, V341 Ara would be the oldest recovered nova of its class and an excellent laboratory for testing nova theory.