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Session 32 - Stars in Various Throes of Stellar Evolution.
Oral session, Monday, January 13
Piers 2/3,

[32.03] Young Binary Star \iota Pegasi with Separation of 1 mas in R.A.

X. Pan, S. Kulkarni (California Institute of Technology), M. M. Colavita, M. Shao (Jet Propulsion Laboratory)

Observations of the young (8\times 10^7 yr) binary star \iota Peg were recently conducted with the Palomar Testbed Interferometer funded by the ASEPS program. For the first time we have determined its visual orbit with separations of 1 mas in R.A. This system has a circular orbit with a radii of 9.4 mas. By combining our data with previous radial velocity measurements we infer that the primary is F5V, mass 1.3 M_ødot and the secondary is G9V, mass 0.8 M_ødot. The distance of the star is determined as 12.1 pc. The two solar-type stars rotate about each other with a separation of only 0.12 AU. By combining these measurements with earlier Mark III Stellar Interferometer data, the V magnitude of the two components is 3.86 mag and 6.36 mag. The corresponding theoretical estimated diameters are 1 mas and 0.7 mas. Both of the components fit the main sequence on the H-R diagram extremely well. Earlier spectroscopic studies have suggested that the system may be an eclipsing binary. Our measured inclination is 94^\circ and we predict that the eclipse will be grazing and last for 3 hours. Photometric observations of the system at the predicted eclipse would be extremely useful.

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