Letter to the Editor

Low-mass star formation in R Coronae Australis: observations of organic molecules with the APEX telescope

¹ Stockholm Observatory, AlbaNova University Center, 106 91 Stockholm, Sweden e-mail: fredrik@astro.su.se
² Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS42, Cambridge, MA 02138, USA
³ Division of Geological and Planetary Sciences, California Institute of Technology, MS 150-21, Pasadena, CA 91125, USA
⁴ European Southern Observatory, Casilla 19001, Santiago 19, Chile

Received: 31 March 2006
Accepted: 15 May 2006

Abstract

This paper presents new APEX submillimetre molecular line observations of three low-mass protostars, IRS7A, IRS7B, and IRAS32, in the R Coronae Australis molecular cloud complex. The molecular excitation analysis is performed using a statistical equilibrium radiative transfer code. The derived beam averaged fractional abundances vary by less than a factor of two among the three sources, except those of H₂CO and CH₃OH, which show differences of about an order of magnitude. The molecular abundances are similar to those typically found in other star-forming regions in the Galaxy, such as the ρ  Oph and Perseus molecular clouds. There is a marked difference in the kinetic temperatures derived for the protobinary source IRS7 from H₂CO (≈40–60 K) and CH₃OH (≈20 K), possibly indicating a difference in origin of the emission from these two molecules.