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Title:
IRC+10216'S Innermost Envelope—The eSMA'S View
Authors:
Shinnaga, Hiroko; Young, Ken H.; Tilanus, Remo P. J.; Chamberlin, Richard; Gurwell, Mark A.; Wilner, David; Hughes, A. Meredith; Yoshida, Hiroshige; Peng, Ruisheng; Force, Brian; Friberg, Per; Bottinelli, Sandrine; Van Dishoeck, Ewine F.; Phillips, Thomas G.
Affiliation:
AA(California Institute of Technology Submillimeter Observatory (CSO), 111 Nowelo St., Hilo, HI 96720, USA ), AB(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA ), AC(Joint Astronomy Centre, 660 North A'ohoku Place, University Park, Hilo, HI 96720, USA ; Netherlands Organization for Scientific Research, P.O. Box 93138, NL-2509 AC The Hague, Netherlands ), AD(California Institute of Technology Submillimeter Observatory (CSO), 111 Nowelo St., Hilo, HI 96720, USA ), AE(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA ), AF(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA ), AG(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA ), AH(California Institute of Technology Submillimeter Observatory (CSO), 111 Nowelo St., Hilo, HI 96720, USA ), AI(California Institute of Technology Submillimeter Observatory (CSO), 111 Nowelo St., Hilo, HI 96720, USA ), AJ(California Institute of Technology Submillimeter Observatory (CSO), 111 Nowelo St., Hilo, HI 96720, USA ), AK(Joint Astronomy Centre, 660 North A'ohoku Place, University Park, Hilo, HI 96720, USA ), AL(Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, Netherlands), AM(Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, Netherlands), AN(California Institute of Technology Submillimeter Observatory (CSO), 111 Nowelo St., Hilo, HI 96720, USA )
Publication:
The Astrophysical Journal, Volume 698, Issue 2, pp. 1924-1933 (2009). (ApJ Homepage)
Publication Date:
06/2009
Origin:
IOP
ApJ Keywords:
circumstellar matter, masers, stars: AGB and post-AGB, stars: individual: IRC+10216, stars: mass loss, stars: winds, outflows
DOI:
10.1088/0004-637X/698/2/1924
Bibliographic Code:
2009ApJ...698.1924S

Abstract

We used the Extended Submillimeter Array (eSMA) in its most extended configuration to investigate the innermost (within a radius of ~290 R * from the star) circumstellar envelope (CSE) of IRC+10216 where acceleration of gas and dust due to strong stellar radiation is taking place. We imaged the CSE using HCN and other molecular lines with a beam size of 0farcs22 × 0farcs46, deeply into the very inner edge (~15 R *) of the envelope where the expansion velocity is only ~3 km s-1. The excitation mechanisms of hot HCN and KCl lines are discussed. HCN maser components are spatially resolved for the first time on an astronomical object. We identified two discrete regions in the envelope: a region with a radius of lsim 15 R *, where molecular species have just formed and the gas has begun to be accelerated (Region I) and a shell region (Region II) with a radius of 23 R * and a thickness of 15 R *, whose expansion velocity has reached up to 13 km s-1, nearly the terminal velocity of 15 km s-1. The Si34S line detected in Region I shows a large expansion velocity of 16 km s-1 due to strong wing components, indicating that the emission may arise from a shock region in the innermost envelope. In Region II, the position angle of the most copious mass-loss direction was found to be ~ 120° ± 10°, which may correspond to the equatorial direction of the star. Region II contains a torus-like feature. These two regions may have emerged due to significant differences in the size distributions of the dust particles in the two regions.
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