Letter to the Editor

Dust and water in V883 Ori: Relics of a retreating snowline

¹ Department of Astronomy, Tsinghua University, 30 Shuangqing Rd, Haidian, DS, 100084 Beijing, China
² Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
³ Department of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, UK
⁴ Center for Star and Planet Formation, GLOBE Institute, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen, Denmark
⁵ European Southern Observatory, Karl-Schwarzschild-Str 2, 85748 Garching, Germany

^⋆ Corresponding author: wang-y21@mails.tsinghua.edu.cn

Received: 13 September 2025
Accepted: 31 October 2025

Abstract

V883 Ori is an FU-Orionis-type outburst system characterized by a shoulder at 50–70 au in its ALMA band 6 and 7 intensity profiles. Previously, this feature was attributed to dust pile-up from pebble disintegration at the water snowline. However, recent multiwavelength observations show continuity in the spectral index across the expected snowline region, disfavoring abrupt changes in grain properties. Moreover, extended water emission is detected beyond 80 au, pointing to a snowline further out. This Letter aims to explain both features with a model in which the snowline is receding. We constructed a 2D disk model that solves the cooling and subsequent vapor recondensation during the post-outburst dimming phase. Our results show that both the intensity shoulder and the extended water emission are natural relics of a retreating snowline: the shoulder arises from excess surface density generated by vapor recondensation at the moving condensation front, while the outer water vapor reservoir persists due to the long recondensation timescales of 10² − 10³ yr at the disk atmosphere. As V883 Ori continues to fade, we predict that the intensity shoulder will migrate inward by an observationally significant amount of 10 au over about 25 years.