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

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.