Discovery of a Possible Cool White Dwarf Companion from the AllWISE Motion Survey

November 2016 • 2016ApJ...832...62F

Authors • Fajardo-Acosta, Sergio B. • Kirkpatrick, J. Davy • Schneider, Adam C. • Cushing, Michael C. • Stern, Daniel • Gelino, Christopher R. • Bardalez-Gagliuffi, Daniella C. • Kellogg, Kendra • Wright, Edward L.

Abstract • We present optical and near-infrared spectroscopy of WISEA J061543.91-124726.8, which we rediscovered as a high motion object in the AllWISE survey. The spectra of this object are unusual; while the red optical (λ > 7000 Å) and near-infrared spectra exhibit characteristic TiO, VO, and H2O bands of a late-M dwarf, the blue portion of its optical spectrum shows a significant excess of emission relative to late-M-type templates. The excess emission is relatively featureless, with the exception of a prominent and very broad Na I D doublet. We find that no single, ordinary star can reproduce these spectral characteristics. The most likely explanation is an unresolved binary system of an M7 dwarf and a cool white dwarf. The flux of a cool white dwarf drops in the optical red and near-infrared, due to collision-induced absorption, thus allowing the flux of a late-M dwarf to show through. This scenario, however, does not explain the Na D feature, which is unlike that of any known white dwarf, but which could perhaps be explained via unusual abundance or pressure conditions.


IPAC Authors

Sergio Fajardo-Acosta

Associate Scientist

Chris Gelino

Associate Scientist


Davy Kirkpatrick

Senior Scientist