Exploring the circumstellar environment of the young eruptive star V2492 Cyg

TL;DR

This study investigates the light variability of the young eruptive star V2492 Cyg, revealing that its flux changes are primarily due to variable extinction caused by a dense inner disk dust cloud, with implications for planet formation.

Contribution

It provides the first detailed multi-wavelength analysis linking light variations to a long-lived inner disk dust structure in V2492 Cyg, challenging the notion that variability is solely due to accretion.

Findings

Light curves are self-similar across wavelengths, indicating a single variability process.

Variability is mainly caused by episodic occultation by a dense inner disk dust cloud.

The inner disk structure is azimuthally asymmetric and long-lived.

Abstract

Context. V2492 Cyg is a young eruptive star that went into outburst in 2010. The near-infrared color changes observed since the outburst peak suggest that the source belongs to a newly defined sub-class of young eruptive stars, where time-dependent accretion and variable line-of-sight extinction play a combined role in the flux changes. Aims. In order to learn about the origin of the light variations and to explore the circumstellar and interstellar environment of V2492 Cyg, we monitored the source at ten different wavelengths, between 0.55 \mu m and 2.2 \mu m from the ground and between 3.6 \mu m and 160 \mu m from space. Methods. We analyze the light curves and study the color-color diagrams via comparison with the standard reddening path. We examine the structure of the molecular cloud hosting V2492 Cyg by computing temperature and optical depth maps from the far-infrared data. Results. We find that the shapes of the light curves at different wavelengths are strictly self-similar and that the observed variability is related to a single physical process, most likely variable extinction. We suggest that the central source is episodically occulted by a dense dust cloud in the inner disk, and, based on the invariability of the far-infrared fluxes, we propose that it is a long-lived rather than a transient structure. In some respects, V2492 Cyg can be regarded as a young, embedded analog of UX Orionis-type stars. Conclusions. The example of V2492 Cyg demonstrates that the light variations of young eruptive stars are not exclusively related to changing accretion. The variability provided information on an azimuthally asymmetric structural element in the inner disk. Such an asymmetric density distribution in the terrestrial zone may also have consequences for the initial conditions of planet formation.