ALMA Monitoring of Millimeter Line Variation in IRC +10216. I. Overview of Millimeter Variability

• Published in: The Astrophysical journal Vol. 883; no. 2; pp. 165 - 180
• Main Authors: He, J. H., Kami ski, T., Mennickent, R. E., Shenavrin, V. I., Mardones, Diego, Wang, Wei, Tang, Baitian, Schmidt, M. R., Szczerba, R., Ge, Jixing
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.10.2019; IOP Publishing
• Subjects: Arrays; Astrophysics; Carbon stars; Infrared radiation; line: identification; line: profiles; Monitoring; Radio telescopes; Spectral sensitivity; stars: AGB and post-AGB; stars: carbon; stars: individual (IRC +10216); stars: winds, outflows; Stellar envelopes; Stellar evolution; Stellar winds
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab3d37

Temporal variation of millimeter lines is a new direction of research for evolved stars. It has the potential to probe the dynamical wind-launching processes from a time dimension. We report here the first Atacama Large Millimeter Array (ALMA) results that cover 817 days of ongoing monitoring of 1.1 mm lines in the archetypal carbon star IRC +10216. The monitoring is done with the compact 7 m array and in infrared with a 1.25 m telescope in Crimea. High sensitivity of the cumulative spectra covering a total of ∼7.2 GHz between 250 and 270 GHz has allowed us to detect about 148 known transitions of 20 molecules, together with more of their isotopologues, and 81 unidentified lines. An overview of the variabilities of all detected line features is presented in spectral plots. Although a handful of lines are found to be very possibly stable in time, most other lines are varying either roughly in phase or in anticorrelation with the near-infrared light. Several lines have their variations in the ALMA data coincident with existing single-dish monitoring results, while several others do not, which requires a yet-unknown mechanism in the circumstellar envelope to explain.