Tentative detection of phosphine in IRC+10216

TL;DR

This paper reports a tentative detection of phosphine (PH3) in the circumstellar envelope IRC+10216, suggesting possible grain surface formation and challenging existing chemical models.

Contribution

First tentative identification of PH3 in IRC+10216, providing new insights into phosphorus chemistry in stellar environments.

Findings

PH3 abundance relative to H2 is approximately 6 x 10^(-9)

PH3 may account for about 5% of phosphorus in IRC+10216

Detection challenges existing chemical formation theories

Abstract

The J,K = 1,0-0,0 rotational transition of phosphine (PH3) at 267 GHz has been tentatively identified with a T_MB = 40 mK spectral line observed with the IRAM 30-m telescope in the C-star envelope IRC+10216. A radiative transfer model has been used to fit the observed line profile. The derived PH3 abundance relative to H2 is 6 x 10^(-9), although it may have a large uncertainty due to the lack of knowledge about the spatial distribution of this species. If our identification is correct, it implies that PH3 has a similar abundance to that reported for HCP in this source, and that these two molecules (HCP and PH3) together take up about 5 % of phosphorus in IRC+10216. The abundance of PH3, as that of other hydrides in this source, is not well explained by conventional gas phase LTE and non-LTE chemical models, and may imply formation on grain surfaces.