Reconstructing the mid-infrared environment in the stellar merger remnant V838 Monocerotis

TL;DR

This study uses high-resolution interferometric imaging to reveal a bipolar, asymmetric structure surrounding V838 Mon, a stellar merger remnant, providing new insights into its post-merger environment in the mid-infrared spectrum.

Contribution

The paper presents the first high-resolution images of V838 Mon in the mid-infrared, revealing a bipolar, asymmetric structure and jet-like features around the star.

Findings

V838 Mon exhibits a bipolar, asymmetric structure in the mid-infrared.

The extended structure shows a clumpy morphology aligned along a specific position angle.

Jet-like features suggest intrinsic asymmetry in the remnant's environment.

Abstract

V838 Mon is a stellar merger remnant that erupted in 2002 in a luminous red novae event. Although it is well studied in the optical, near infrared and submillimeter regimes, its structure in the mid-infrared wavelengths remains elusive. We observed V838 Mon with the MATISSE (LMN bands) and GRAVITY (K band) instruments at the VLTI and also the MIRCX/MYSTIC (HK bands) instruments at the CHARA array. We geometrically modelled the squared visibilities and the closure phases in each of the bands to obtain constraints on physical parameters. Furthermore, we constructed high resolution images of V838 Mon in the HK bands, using the MIRA and SQUEEZE algorithms to study the immediate surroundings of the star. Lastly, we also modelled the spectral features seen in the K and M bands at various temperatures. The image reconstructions show a bipolar structure that surrounds the central star in the post merger remnant. In the K band, the super resolved images show an extended structure (uniform disk diameter $\sim 1.94$ mas) with a clumpy morphology that is aligned along a north-west position angle (PA) of $-40^\circ$. Whereas in the H band, the extended structure (uniform disk diameter $\sim 1.18$ mas) lies roughly along the same PA. However, the northern lobe is slightly misaligned with respect to the southern lobe, which results in the closure phase deviations. The VLTI and CHARA imaging results show that V838 Mon is surrounded by features that resemble jets that are intrinsically asymmetric. This is also confirmed by the closure phase modelling. Further observations with VLTI can help to determine whether this structure shows any variation over time, and also if such bipolar structures are commonly formed in other stellar merger remnants.