Astronomy and Astrophysics – Astronomy
Scientific paper
Jun 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008apj...680l.121t&link_type=abstract
The Astrophysical Journal, Volume 680, Issue 2, pp. L121-L124.
Astronomy and Astrophysics
Astronomy
7
Astrochemistry, Stars: Circumstellar Matter, Ism: Molecules, Radio Lines: Stars, Stars: Individual: Alphanumeric: Crl 2688, Stars: Individual: Alphanumeric: Irc +10216
Scientific paper
We present the results of a search for the JK=10-->00 transition of PH3 (phosphine) at 267 GHz toward several circumstellar envelopes using the Arizona Radio Observatory 10 m Submillimeter Telescope (SMT). In the carbon-rich shells of IRC +10216 and CRL 2688, we have detected emission lines exactly at the PH3 frequency. Toward the oxygen-rich supergiant VY Canis Majoris, only an upper limit was obtained, while in the evolved carbon-rich proto-planetary nebula CRL 618, the transition is contaminated by vibrationally excited HC3N (ν7 = 4). The line shape in IRC +10216 appears to consist of two distinct components: a flat-topped profile with a width of ~28 km s-1, as is typical for this source, and a narrower feature approximately 4 km s-1 wide. The narrow component likely arises from the inner envelope (r<8R*) where the gas has not reached the terminal expansion velocity, or it is nonthermal emission. Based on the broader component, the abundance of PH3 with respect to H2 is estimated to be 5 × 10-8 in a region with a radius of r<150R*. If the narrower component is thermal, it implies a phosphine abundance of ~5 × 10-7 close to the stellar photosphere (r<8R*). In CRL 2688, the PH 3 abundance is less constrained, with plausible values ranging from 3 × 10 -8 to 4 × 10-7, assuming a spherical distribution. Phosphine appears to be present in large concentrations in the inner envelope of C-rich AGB stars, and thus may function as a parent molecule for other phosphorus species.
Tenenbaum Emily D.
Ziurys Lucy M.
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