sdA in SDSS DR12 are Overwhelmingly Not Extremely Low-Mass (ELM) White Dwarfs [SSA]

In a search for new white dwarfs in DR12 of the Sloan Digital Sky Survey, Kepler et al. (2016) found atmospheric parameters for thousands of objects with effective temperatures below 20,000 K and surface gravities between 5.5 < log(g) < 6.5. They classified these objects as cool subdwarfs — sdA — and speculated that many may be extremely low-mass (ELM) white dwarfs (helium-core white dwarfs with masses below 0.3 Msun). We present evidence — using radial velocities, photometric colors, and reduced proper motions — that the vast majority (>99%) of these objects are unlikely to be ELM white dwarfs. Their true identity remains an interesting question.

Read this paper on arXiv…

J. Hermes, B. Gaensicke and E. Breedt
Mon, 27 Feb 17

Comments: 7 pages, 3 figures, 2 tables. As appears in the ASP Conference Series proceedings of “20th European Workshop Workshop on White Dwarfs” held at the University of Warwick, UK on July 25-29th, 2016