[ITAL]HST[/ITAL]/GHRS Observations of the β Pictoris System: Basic Parameters and the Age of the System

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Abstract
We have reevaluated the basic parameters and age of the A5 IV-V star, β Pictoris, making use of new observations obtained by the Goddard High-Resolution Spectrograph aboard the Hubble Space Telescope and using modern methods of atmospheric modeling and spectral synthesis. We derive stellar parameters appropriate to its spectral type (Teff = 8200 ± 150 K, log g = 4.25 ± 0.1) including a normal (solar) metallicity. When dated by comparison with current evolutionary tracks, we find that (1) the star is apparently "underluminous"—a situation we attribute to (gray) extinction by the disk—and (2) the star is either a pre-main-sequence (PMS) star nearing the zero-age main sequence (ZAMS), or it is a main-sequence star older than 0.3 Gyr. Given the apparent youth of the disk as inferred from its high density, we judge the PMS interpretation as most likely.