Molecules in the Circumstellar Disk Orbiting BP Piscium - AstrophysicsReport as inadecuate

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Abstract: BP Psc is a puzzling late-type, emission-line field star with large infraredexcess. The star is encircled and enshrouded by a nearly edge-on, dustcircumstellar disk, and displays an extensive jet system similar to thoseassociated with pre-main sequence pre-MS stars. We conducted a mm-wavemolecular line survey of BP Psc with the 30 m telescope of the Institut deRadio Astronomie Millimetrique IRAM. We detected lines of 12CO and 13CO and,possibly, very weak emission from HCO+ and CN; HCN, H2CO, and SiO are notdetected. The CO line profiles of BP Psc are well fit by a model invoking adisk in Keplerian rotation. The mimumum disk gas mass, inferred from the 12COline intensity and 13CO-12CO line ratio, is ~0.1 Jupiter masses. The weaknessof HCO+ and CN relative to 13CO stands in sharp contrast to the strong HCO+and CN emission that characterizes most low-mass, pre-main sequence stars thathave been the subjects of molecular emission-line surveys, and is suggestive ofa very low level of X-ray-induced molecular ionization within the BP Psc disk.These results lend some support to the notion that BP Psc is an evolved starwhose circumstellar disk has its origins in a catastrophic interaction with aclose companion.

Author: Joel H. Kastner Laboratoire d'Astrophysique de Grenoble and Rochester Institute of Technology, B. Zuckerman UCLA, Thierry Fo


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