Open AccessIRAS 12311−3509: a carbon star with SiC 2 emission
Author(s) -
Lloyd Evans T.,
Hurst M. E.,
Sarre P. J.
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03819.x
Subject(s) - physics , astrophysics , carbon star , emission spectrum , infrared , spectral energy distribution , reflection nebula , astronomy , asymptotic giant branch , wavelength , spectral line , stars , planetary nebula , optics
The optical spectrum of the carbon star IRAS 12311−3509 is dominated by the Merrill–Sanford emission bands of SiC 2 , by absorption and emission in the Swan system of C 2 , and by resonance emission lines of neutral metals. The infrared energy distribution is flat from 1 to 60 μm. These observations are interpreted as arising from a star with a cool dusty disc which is edge‐on to the observer and obscures direct starlight. The infrared continuum is caused predominantly by absorption of stellar light by dust in the disc and re‐emission at longer wavelengths. The optical stellar spectrum is seen by reflection off dusty material which lies out of the plane of the disc, and the molecular and atomic emission arises in the same geometry through resonance fluorescence. The object has similarities to the J‐silicate stars, but may have a carbon‐rich rather than oxygen‐rich disc. A full spectroscopic assignment and discussion of the SiC 2 bands and their intensities are given. Modelling of the rotational contours of the band yields a rotational temperature of 250 K, indicating very cool gas.