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Title: SDSS J074511.56+194926.5: Discovery of a metal-rich and tidally distorted extremely low mass white dwarf

We present the discovery of an unusual, tidally distorted extremely low mass white dwarf (WD) with nearly solar metallicity. Radial velocity measurements confirm that this is a compact binary with an orbital period of 2.6975 hr and a velocity semi-amplitude of K = 108.7 km s{sup –1}. Analysis of the hydrogen Balmer lines yields an effective temperature of T {sub eff} = 8380 K and a surface gravity of log g = 6.21 that in turn indicate a mass of M = 0.16 M {sub ☉} and a cooling age of 4.2 Gyr. In addition, a detailed analysis of the observed metal lines yields abundances of log (Mg/H) = –3.90, log (Ca/H) = –5.80, log (Ti/H) = –6.10, log (Cr/H) = –5.60, and log (Fe/H) = –4.50, similar to the sun. We see no evidence of a debris disk from which these metals would be accreted, though the possibility cannot entirely be ruled out. Other potential mechanisms to explain the presence of heavy elements are discussed. Finally, we expect this system to ultimately undergo unstable mass transfer and merge to form a ∼0.3-0.6 M {sub ☉} WD in a few Gyr.
Authors:
; ;  [1] ; ;  [2] ; ;  [3] ;  [4]
  1. Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks St., Norman, OK 73019 (United States)
  2. Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States)
  3. Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA 02138 (United States)
  4. Département de Physique, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, Québec H3C 3J7 (Canada)
Publication Date:
OSTI Identifier:
22348088
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 781; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; AMPLITUDES; BALMER LINES; COMPACTS; GRAVITATION; HYDROGEN; MASS TRANSFER; METALLICITY; METALS; RADIAL VELOCITY; SUN; SURFACES; TRITIUM; WHITE DWARF STARS