SIMBAD references

2000ApJ...544..881H - Astrophys. J., 544, 881-888 (2000/December-1)

Millimeter observations of vibrationally excited CS toward IRC +10216: a new circumstellar maser?


Abstract (from CDS):

New observations of vibrationally excited CS in its v=1 state have been conducted toward the circumstellar shell of IRC +10216 using the NRAO 12 m telescope and the CSO. The J=3⟶2, 6⟶5, and 7⟶6 transitions in the v=1 level at 146, 292, and 340 GHz have been detected toward this object, and the J=2⟶1 and 5⟶4 lines were also reobserved. After accounting for contamination from other species, these CS transitions all exhibit line profiles that are narrower (ΔV1/2∼10 km.s–1) than those displayed by most molecules in IRC +10216, indicating an origin in the inner stellar envelope. The J=3⟶2 line is particularly narrow (ΔV1/2∼1-2 km.s–1), and consists of two separate velocity components at VLSR~-26 and -22 km.s–1. These characteristics are suggestive of weak maser action in this transition. The narrow line widths observed in the other transitions indicate a source size ≲0".5, which implies a CS column density in the v=1 state of ∼2-6x1016 cm–2. The ground-state (v=0) column density is therefore on the order of 0.8-2x1018 cm–2 for Tvib=500 K. The fractional abundance of CS relative to H2 is consequently f∼3-7x10–5 at ∼14 R*. Such a high abundance close to the stellar photosphere is strong evidence that CS is a ``parent'' molecule in IRC +10216, as suggested by infrared studies of the v=0⟶1 vibrational transition and interferometric observations.

Abstract Copyright:

Journal keyword(s): Stars: Circumstellar Matter - Masers - Radio Lines: Stars - Stars: AGB and Post-AGB - stars: individual (IRC +10216)

Simbad objects: 13

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