Infrared photometry of the dwarf nova V2051 Ophiuchi: I - The mass donor star and the distance

TL;DR

This study analyzes infrared photometry of dwarf nova V2051 Oph to determine the donor star's properties and distance, revealing implications for the outburst mechanism.

Contribution

It provides the first detailed infrared analysis of the donor star and estimates the system's distance, challenging existing models of dwarf nova outbursts.

Findings

Donor star has spectral type M8 ± 1.5.

Distance to the system is approximately 102 ± 16 parsecs.

Outburst temperatures are too low for the disc-instability model.

Abstract

We report the analysis of time-series of infrared $JHK_s$ photometry of the dwarf nova V2051 Oph in quiescence. We modelled the ellipsoidal variations caused by the distorted mass-donor star to infer its $JHK_s$ fluxes. From its infrared colors we estimate a spectral type of $M(8.0\pm 1.5)$ and an equivalent blackbody temperature of $T_\mathrm{BB}=(2700\pm270)\,K$. We used the Barnes & Evans relation to infer a photometric parallax distance of $d_\mathrm{BE}=(102\pm16)$ pc to the binary. At this short distance, the corresponding accretion disc temperatures in outburst are too low to be explained by the disc-instability model for dwarf nova outbursts, underscoring a previous suggestion that the outbursts of this binary are powered by mass-transfer bursts.