Runaway Dwarf Carbon Stars as Candidate Supernova Ejecta

Abstract

The dwarf carbon (dC) star SDSS J112801.67+004034.6 has an unusually high radial velocity, 531$\pm 4$ km s${}^{-1}$. We present proper motion and new spectroscopic observations which imply a large Galactic rest frame velocity, 425$\pm 9$ km s${}^{-1}$. Several other SDSS dC stars are also inferred to have very high galactocentric velocities, again each based on both high heliocentric radial velocity and also confidently detected proper motions. Extreme velocities and the presence of $C_2$ bands in the spectra of dwarf stars are both rare. Passage near the Galactic center can accelerate stars to such extreme velocities, but the large orbital angular momentum of SDSS J1128 precludes this explanation. Ejection from a supernova in a binary system or disruption of a binary by other stars are possibilities, particularly as dC stars are thought to obtain their photospheric $C_2$ via mass transfer from an evolved companion.

Accepted for publication in The Astrophysical Journal

References in corpus (7)

• The SEGUE Stellar Parameter Pipeline. I. Description and Initial Validation Tests
• The fastest unbound star in our Galaxy ejected by a thermonuclear supernova
• Maximum speed of hypervelocity stars ejected from binaries
• Carbon in Red Giants in Globular Clusters and Dwarf Spheroidal Galaxies
• The Nearest High-Velocity Stars Revealed by LAMOST Data Release 1
• HD271791: dynamical versus binary-supernova ejection scenario
• A Deep Proper Motion Catalog Within The Sloan Digital Sky Survey Footprint

Cited by in corpus (1)

• Discovery of carbon-rich Miras in the Galactic bulge