The Maser-emitting Structure and Time Variability of the SiS Lines J=14-13 and 15-14 in IRC+10216

J. P. Fonfría, M. Fernández-López, J. R. Pardo, M. Agúndez, C. Sánchez Contreras, L. Velilla Prieto, J. Cernicharo, M. Santander-García, G. Quintana-Lacaci, A. Castro-Carrizo, S. Curiel. 2018. The Maser-emitting Structure and Time Variability of the SiS Lines J=14-13 and 15-14 in IRC+10216. Astrophysical Journal 860, 2, DOI: 10.3847/1538-4357/aac5e3

We present new high angular resolution interferometer observations of the v = 0 J = 14-13 and 15-14 SiS lines toward IRC+ 10216, carried out with the Combined Array for Research in Millimeter-wave Astronomy and the Atacama Large Millimeter Array. The maps, with angular resolutions of similar or equal to 0 ”.25 and 0 ”.55, reveal (1) an extended, roughly uniform, and weak emission with a size of similar or equal to 0 ”.5; (2) a component elongated approximately along the east-west direction peaking at similar or equal to 0 ”.13 and 0 ”.17 at both sides of the central star; and (3) two blue-and redshifted compact components peaking around 0 ”.07 to the NW of the star. We have modeled the emission with a 3D radiation transfer code, finding that the observations cannot be explained only by thermal emission. Several maser clumps and one arc-shaped maser feature arranged from 5 to 20 R-star from the central star, in addition to a thin shelllike maser structure at similar or equal to 13 R-star, are required to explain the observations. This maser-emitting set of structures accounts for 75% of the total emission, while the other 25% is produced by thermally excited molecules. About 60% of the maser emission comes from the extended emission, and the rest comes from the set of clumps and the arc. The analysis of a time monitoring of these and other SiS and (SiS)-Si-29 lines carried out with the IRAM 30 m telescope from 2015 to present suggests that the intensity of some spectral components of the maser emission strongly depends on the stellar pulsation, while other components show a mild variability. This monitoring evidences a significant phase lag of similar or equal to 0.2 between the maser and near-IR light curves.

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