PROBING THE MASS-LOSS HISTORY OF THE YELLOW HYPERGIANT IRC+10420

Journal Article · Wed May 20 04:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/697/1/409; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21300584

Dinh-V-Trung,; Muller, Sebastien; Lim, Jeremy ^[1]; Kwok, Sun ^[2]

---

1. Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan (China)
2. Department of Physics, Faculty of Science, University of Hong Kong (Hong Kong)

We have used the submillimeter array to image the molecular envelope around the yellow hypergiant IRC+10420. Our observations reveal a large and clumpy expanding envelope around the star. The molecular envelope shows a clear asymmetry in {sup 12}CO J = 2-1 emission in the southwest direction. The elongation of the envelope is found even more pronounced in the emission of {sup 13}CO J = 2-1 and SO J {sub K} = 6{sub 5}-5{sub 4}. A small positional velocity gradient across velocity channels is seen in these lines, suggesting the presence of a weak bipolar outflow in the envelope of IRC+10420. In the higher resolution {sup 12}CO J = 2-1 map, we find that the envelope has two components: (1) an inner shell (shell I) located between radius of about 1'' and 2''; (2) an outer shell (shell II) located between 3'' and 6'' in radius. These shells represent two previous mass-loss episodes from IRC+10420. We attempt to derive in self-consistent manner the physical conditions inside the envelope by modeling the dust properties, and the heating and cooling of molecular gas. We estimate a mass-loss rate of {approx}9 x 10{sup -4} M {sub sun} yr{sup -1} for shell I and 7 x 10{sup -4} M {sub sun} yr{sup -1} for shell II. The gas temperature is found to be unusually high in IRC+10420 in comparison with other oxygen-rich envelopes. The elevated gas temperature is mainly due to higher heating rate, which results from the large luminosity of the central star. We also derive an isotopic ratio {sup 12}C/{sup 13}C = 6.

• OSTI ID: 21300584
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 697; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
99 GENERAL AND MISCELLANEOUS
ASYMMETRY
CARBON 12
CARBON 13
EMISSION
HEATING RATE
ISOTOPE RATIO
LUMINOSITY
MATTER
OXYGEN
SIMULATION
STARS