2024A&A...682A..75L

Aims. In this work, we study the silicate dust content in the disk of one of the youngest eruptive stars, V900 Mon, at the highest angular resolution, probing down to the inner 10 au of said disk, and study the historical evolution of the system, traced in part by a newly discovered emission clump.
Methods. We performed high angular resolution MIR interferometric observations of V900 Mon with MATISSE/VLTI with a spatial coverage ranging from 38 to 130-m baselines, and compared them to archival MIDI/VLTI data. We also mined and re-analyzed archival optical and infrared photometry of the star to study its long-term evolution since its eruption in the 1990s. We complemented our findings with integral field spectroscopy data from MUSE/VLT.
Results. The MATISSE/VLTI data suggest a radial variation in the silicate feature in the dusty disk, whereby at large spatial scales (≥10 au) the protostellar disk's emission is dominated by large-sized (≥1μm) silicate grains, while at smaller spatial scales and closer to the star (≤5 au) silicate emission is absent, suggesting self-shielding. We propose that the self-shielding may be the result of small dust grains at the base of the collimated CO outflow previously detected by ALMA. A newly discovered knot in the MUSE/VLT data, located at a projected distance approximately 27 000 au from the star, is co-aligned with the molecular gas outflow at a P.A. of 250°(±5°) consistent with the position angle and inclination of the disk. The knot is seen in emission in Hα [N II], and the [S II] doublet and its kinematic age is about 5150 yr. This ejected material could originate from a previous eruption.