HD 98800: A Unique Stellar System of Post-T Tauri Stars

HD 98800 is a system of four stars, and it has a large infrared excess that is thought to be due to a dust disk within the system. In this paper we present new astrometric observations made with Hipparcos, as well as photometry from Hubble Space Telescope WFPC2 images. Combining these observations and reanalyzing previous work allow us to estimate the age and masses of the stars in the system. Uncertainty in these ages and masses results from uncertainty in the temperatures of the stars and any reddening they may have. We find that HD 98800 is most probably about 10 Myr old, although it may be as young as 5 Myr or as old as 20 Myr. The stars in HD 98800 appear to have metallicities that are about solar. An age of 10 Myr means that HD 98800 is a member of the post-T Tauri class of objects, and we argue that the stars in HD 98800 can help us understand why post-T Tauris have been so elusive. HD 98800 may have formed in the Centaurus star-forming region, but it is extraordinary in being so young and yet so far from where it was born.

[1]  T. Forveille,et al.  X-ray and molecular emission from the nearest region of recent star formation. , 1997, Science.

[2]  E. Feigelson,et al.  On "A New Stellar Nursery in the Southern Cross" [Astron.J.112,693(1996)] , 1997 .

[3]  K. Cunha,et al.  Lithium Abundances in the Solar Twins 16 CYG A and B and the Solar Analog alpha CEN A, Calibration of the 6707 Angstrom Li Region Linelist, and Implications , 1997 .

[4]  L. Hartmann,et al.  X-Rays Surveys and the Post-T Tauri Problem , 1997 .

[5]  E. Covino,et al.  Search for young low-mass stars in a ROSAT selected sample south of the Taurus-Auriga molecular clouds , 1996, astro-ph/9612193.

[6]  F. Palla,et al.  Post-T Tauri Stars: A False Problem , 1996, astro-ph/9612139.

[7]  E. Feigelson.  Dispersed T Tauri stars and galactic star formation , 1996 .

[8]  D. James,et al.  2RE J0241 — 525: a nearby post-T Tauri visual binary system , 1996 .

[9]  J. Finley,et al.  A new stellar nursery in the southern cross , 1996 .

[10]  M. Shetrone,et al.  The Evolution of the Lithium Abundances of Solar-Type Stars. VI. The End of Lithium in the Pleiades , 1996 .

[11]  M. Barlow,et al.  Optical, infrared and millimetre-wave properties of Vega-like systems - II. Radiative transfer modelling , 1996 .

[12]  M. Shetrone,et al.  The Age-related Properties of the HD 98800 System , 1996 .

[13]  T. Mazeh,et al.  Study of Spectroscopic Binaries with TODCOR. IV. The Multiplicity of the Young Nearby Star HD 98800 , 1995 .

[14]  Stefano Casertano,et al.  THE PERFORMANCE AND CALIBRATION OF WFPC2 ON THE HUBBLE SPACE TELESCOPE , 1995 .

[15]  Alexander Brown,et al.  X-ray sources in regions of star formation. 5: The low mass stars of the Upper Scorpius association , 1994 .

[16]  B. Zuckerman,et al.  Infrared observations of the remarkable main-sequence star HD 98800 , 1993 .

[17]  S. Wood,et al.  Geochim. cosmochim. acta , 1990 .

[18]  M. Skrutskie,et al.  A sensitive 10-micron search for emission arising from circumstellar dust associated with solar-type pre-main-sequence stars , 1990 .

[19]  David R. Soderblom,et al.  Calculating Galactic Space Velocities and Their Uncertainties, with an Application to the Ursa Major Group , 1987 .

[20]  Michael S. Bessell,et al.  UBVRI PHOTOMETRY II: THE COUSINS VRI SYSTEM, ITS TEMPERATURE AND ABSOLUTE FLUX CALIBRATION, AND RELEVANCE FOR TWO-DIMENSIONAL PHOTOMETRY. , 1979 .

[21]  C. Sneden.  The nitrogen abundance of the very metal-poor star HD 122563. , 1973 .

[22]  G. Herbig.  BD -10 4662 interpreted as a post-T Tauri star. , 1973 .

[23]  A. Blaauw.  The O Associations in the Solar Neighborhood , 1964 .

[24]  F. Bertiau.  Absolute Magnitudes of Stars in the Scorpio-Centaurus Association. , 1958 .

[25]  U. Bastian,et al.  PPM star catalogue : positions and proper motions of 181731 stars north of -2.5 degrees declination for equinox and epoch J2000.0 , 1991 .

[26]  N. Grevesse,et al.  Abundances of the elements: Meteoritic and solar , 1989 .