PG 2131+066 is a composite–spectrum binary with a hot pulsating PG 1159-type pre–white dwarf and an early M-type main sequence star .
Analysis of Whole Earth Telescope observations of the pulsating pre-white dwarf component provided an asteroseismological determination of its mass , luminosity , and effective temperature .
These determinations allowed Kawaler et al .
( 1995 ) to determine the distance to this star .
In this paper , we refine the asteroseismological distance determination , and confirm the distance by an independent measurement to the system via the spectroscopic parallax of the M star .
PG 2131+066 was observed by the HST using the original PC in September 1993 .
Exposures with filters F785LP and F555W both showed the companion at a distance of 0.3 arc seconds .
Photometry of the images provides an apparent magnitude for the main sequence companion of m _ { v } = 18.97 \pm 0.15 , from which we find a distance of 560 ^ { +200 } _ { -134 } pc .
We also recalculated the asteroseismological distance to the pre–white dwarf using updated models and new spectroscopic constraints from UV spectra .
The new seismological distance is 668 ^ { +78 } _ { -83 } parsecs , in satisfactory agreement with the distance of the secondary star .
These results suggest that this is indeed a physical binary , and that the seismological distance determination technique may be the best way to determine the distance to the pulsating hot pre-white dwarf stars .