The Extremely Low Luminosity White Dwarf ESO 439–26

, , , and

© 1995. The American Astronomical Society. All rights reserved. Printed in U.S.A.
, , Citation María Teresa Ruiz et al 1995 ApJ 455 L159 DOI 10.1086/309845

1538-4357/455/2/L159

Abstract

We present a detailed analysis of the extremely low luminosity white dwarf ESO 439-26. The measured trigonometric parallax of π = 0farcs0237 ± 0farcs0030, together with the observed V magnitude of 20.52, yields an absolute visual magnitude of MV = 17.4 ± 0.3. ESO 439-26 thus lies more than 1 mag faintward of the observed cutoff of the white-dwarf luminosity function in the Galactic disk and could therefore be the coolest and hence oldest white dwarf ever detected. However, we show from a detailed analysis of the optical energy distribution that the intrinsic low luminosity of ESO 439-26 is the result of its small radius, or large mass. Our best solution is reached with Teff = 4560 ± 100 K, log g = 9.04 ± 0.14, and a pure-helium atmospheric composition. Evolutionary models are used to derive a mass of M = 1.21 ± 0.07 M and a cooling age of 6.4 ± 0.3 Gyr, a value that is smaller than the current estimates of the age of the Galactic disk.

Export citation and abstract BibTeX RIS

Please wait… references are loading.
10.1086/309845