ASTEROSEISMOLOGY OF A STAR COOLED BY NEUTRINO EMISSION - THE PULSATING PRE-WHITE DWARF PG-0122+200

Observation of g-mode pulsations in the variable pre-white dwarf (GW V irginis) stars provides a unique means to probe their interiors and to study the late stages of stellar evolution. Multisite campaigns have in several cases proved highly successful in decoding pre-white dwarf light curves. Three previous attempts to untangle the pulsation spectr um of the coolest GW Virginis star, PG 0122+200, confirmed the existen ce of multiple g-modes but left the fundamental period spacing and the refore the star's mass and luminosity in doubt. We present an analysis based on new observations of PG 0122+200 obtained during a Whole Eart h Telescope (WET) campaign conducted in the fall of 1996. Although our coverage was, because of bad weather, far poorer than in previous WET campaigns, we confirm the previous result that PG 0122+200 rotates on ce in 1.6 +/- 0.1 days. The most likely period spacing supported by th e data implies a mass of 0.69 +/- 0.03 M.. Based on the best seismolog y we can currently do, the cooling of PG 0122+200 is dominated by neut rino losses. This is not true for all pre-white dwarf stars and makes PG 0122+200 the prime candidate for learning useful physics. Constrain ts placed on the cooling rate of PG 0122+200 by future measurement of d Pi/dt could provide a unique test of the standard theory of lepton i nteractions in the (experimentally unexplored) region of phase-space a ppropriate to pre-white dwarf interiors.