1998/09/02 by M. A. T. Groenewegen, Groenewegen, M. A. T., H.‐G. Ludwig +2
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #Geomagnetism and Paleomagnetism Studies #Ionosphere and magnetosphere dynamics #Magnetic confinement fusion research #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9809010
Astronomy & Astrophysics, accepted. Incorrect figure 2 replaced
openalex publication_date 1998/09/02 · arxiv created 1998/09/25 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
A CO(1-0) on-source spectrum of the well-known carbon star IRC+10216 taken with the IRAM 30m telescope in June 1996 shows excess emission between -18.3 and -14.3 km/s at the red wing of the underlying profile. The excess emission is confirmed in January 1997 but is absent in April 1997 and June 1998 IRAM spectra. Such a transient feature has not been seen before in this star or any other AGB star. In April 1997 we mapped the circumstellar shell out to 110". Both the J = 1-0 and J = 2-1 spectra show ``spikes'' or components which vary in strength with position in the envelope. One of these components corresponds to the velocity interval mentioned above. An immediate conclusion is that the circumstellar shell is not spherically symmetric, contrary to what was believed based on lower spectral resolution data. We are probably seeing emission from a complex geometrical structure. Neither a disk structure nor a double-wind structure seem to be able to explain the observations. The on-source transient behaviour of the red excess emission can reasonably well be explained by a single large (about 5 x 1013 cm) blob, that expands due to internal motion.