Resolving LB 11146 with Hubble Space Telescope's Fine Guidance Sensor

Details Resolving LB 11146 with Hubble Space Telescope's Fine Guidance Sensor Resolving LB 11146 with Hubble Space Telescope's Fine Guidance Sensor

Nov 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aj....134.1934n&link_type=abstract

The Astronomical Journal, Volume 134, Issue 5, pp. 1934-1937 (2007).

Astronomy and Astrophysics

Astronomy

2

Binaries: Close, Stars: Individual: Lb 11146, Techniques: Interferometric, White Dwarfs

Scientific paper

On the basis of its observed spectra, LB 11146 was identified as a binary system composed of pair of massive (~0.9 Modot) white dwarf stars. However, observations with the Hubble Space Telescope (HST) Faint Object Camera did not resolve the system, and searches for radial velocity variations yielded null results. Subsequent observations of LB 11146 with the HST's Fine Guidance Sensor have resolved the system at three epochs spanning 295 days, thereby confirming the binary nature of this object. We find a nearly constant component separation of approximately 15 mas and a large change in position angle, consistent with a low-inclination, low-eccentricity orbit with a period of approximately 130 days. At a distance of 40 pc, this corresponds to a component separation of about 0.6 AU, which in turn also results in a Keplerian orbit with a period of about 130 days, assuming the spectroscopic masses of the white dwarfs. The size of the orbit is significantly smaller than the size of the progenitor stars as they evolved through the asymptotic giant branch, so one or more phases of binary star evolution is likely to have occurred. LB 11146 joins PG 1115+116, but in a more extreme sense, as an example of a close binary composed of massive white dwarfs that did not evolve to become a short-period system, thereby providing an additional key observational test for models of binary star evolution.
Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

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