PG 0922+162: Discovery of the Youngest Visual Double Degenerate

Details PG 0922+162: Discovery of the Youngest Visual Double Degenerate PG 0922+162: Discovery of the Youngest Visual Double Degenerate

Nov 1997

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997apj...489l..79f&link_type=abstract

Astrophysical Journal Letters v.489, p.L79

Astronomy and Astrophysics

Astronomy

10

Stars: Fundamental Parameters, Stars: Binaries: Visual, Stars: Atmospheres, Stars: Evolution, Stars: Individual Alphanumeric: Pg 0922+162, Stars: White Dwarfs

Scientific paper

We recently discovered PG (WD) 0922+162 to be a visual double degenerate pair, the youngest found to date. Both components have effective temperatures just above 22,000 K, a region in which detailed fitting of the Balmer line profiles from high signal-to-noise spectra provides very accurate temperatures and gravities. Spatially resolved visual double degenerates can, in principle, be used to determine the initial-final mass ( Mi - Mf ) relation for white dwarfs. PG 0922+162 is the first resolved double degenerate for which the physical parameters may be derived with sufficient accuracy to improve on cluster results for the Mi - Mf relation. Using Wood's WD cooling models to determine the masses, our results are that the more luminous member of the pair, PG 0922+162 A, has T_{{eff}} = 22,740 +/- 230 K, log g = 8.27 +/- 0.05, and M = 0.79 +/- 0.03 Msolar , while the fainter star, PG 0922+162 B, has T_{{eff}} = 22,130 +/- 220 K, log g = 8.78 +/- 0.05, and M = 1.10 +/- 0.03 Msolar . The corresponding WD cooling times are about 90 and 260 Myr, respectively. Given the lack of an independent determination of the age of the system, we cannot directly obtain the progenitor mass for PG 0922+162 B. However, previous cluster results provide plausible limits to the progenitor mass for PG 0922+162 B of 5.5--7.5 Msolar , which in turn limits the age of the PG 0922+162 system to the range of about 290--350 Myr. Given that age range, we find that the initial mass of the progenitor of PG 0922+162 A must lie within the narrow range of 3.6--4.0 Msolar .

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