Hubble Space Telescope Imaging of the Site of the Red Transient V4332 Sagittarii

TL;DR

This study uses Hubble Space Telescope imaging to analyze the dusty ejecta of the 1994 red transient V4332 Sagittarii, revealing its morphology and potential stellar companion, contributing to understanding stellar merger events.

Contribution

First optical imaging of V4332 Sgr's ejecta with HST, providing detailed morphology and suggesting a possible stellar companion based on proper motion analysis.

Findings

Ejecta dimensions are consistent with 1994 eruption timing.

Optical nebula morphology matches CO emission maps.

Potential stellar companion identified at similar distance.

Abstract

V4332 Sgr is a red optical transient that erupted in 1994. It is generally considered to have been due to a stellar merger similar to V838 Mon and V1309 Sco. I obtained optical images of the site with HST in 2014. The images resolve the dusty ejecta, with dimensions of about 0.53 x 0.42 arcsec; these are approximately consistent with expectation if the ejecta were launched in 1994. The size and morphology of the optical nebula are similar to those seen in recent ALMA and SMA maps of CO emission. The Gaia DR2 parallax of V4332 Sgr has a large uncertainty. However, I point out a 12th-mag star 10 arcsec south of V4332 Sgr that has a DR2 proper motion and radial velocity similar to those of the transient; its distance is 1.63 kpc. If V4332 Sgr is a physical companion of this star, its absolute visual magnitude at maximum was only -3.6.