Shinnaga, Hiroko and Young, Ken H. and Tilanus, Remo P. J. and Chamberlin, Richard and Gurwell, Mark A. and Wilner, David and Hughes, A. Meredith and Yoshida, Hiroshige and Peng, Ruisheng and Force, Brian and Friberg, Per and Bottinelli, Sandrine and Van Dishoeck, Ewine F. and Phillips, Thomas G. (2009) IRC+10216'S Innermost Envelope — The eSMA'S View. Astrophysical Journal, 698 (2). pp. 1924-1933. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20090908-095644822
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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 0".22 × 0".46, 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 ≾ 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 Si^(34)S 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.
|Additional Information:||© 2009 The American Astronomical Society. Received 2008 November 24; accepted 2009 April 3; published 2009 June 5. The Caltech Submillimeter Observatory is supported by grant AST-0540882 from the National Science Foundation. The eSMA developments at the JCMT are financially supported by a Netherlands NWO-M grant, the Netherlands Organization for Scientific Research, and NWO. The development of the eSMA has been facilitated by grant 614.061.416 from the Netherlands Organisation for Scientific Research, NWO. The JCMT is supported by the United Kingdom’s Science and Technology Facilities Council (STFC), the National Research Council Canada (NRC), and the Netherlands Organization for Scientific Research (NWO). The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. We sincerely appreciate strong support from Ray Blundell, Gary Davis, and Tom Phillips, the directors of the SMA, JCMT, and CSO, respectively. H.S. is grateful to Ray S. Furuya, Charlie Qi, Nick Scoville, and Frank Lovas for various discussion. A.M.H. is supported by a National Science Foundation Graduate Research Fellowship. Facilities: eSMA, CSO, JCMT, SMA.|
|Subject Keywords:||circumstellar matter; masers; stars: AGB and post-AGB; stars: individual (IRC+10216); stars: mass loss; stars: winds, outflows|
|Official Citation:||IRC+10216'S Innermost Envelope—The eSMA'S View Hiroko Shinnaga, Ken H. Young, Remo P. J. Tilanus, Richard Chamberlin, Mark A. Gurwell, David Wilner, A. Meredith Hughes, Hiroshige Yoshida, Ruisheng Peng, Brian Force, Per Friberg, Sandrine Bottinelli, Ewine F. Van Dishoeck, and Thomas G. Phillips 2009 ApJ 698 1924-1933 doi: 10.1088/0004-637X/698/2/1924.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||15 Sep 2009 16:49|
|Last Modified:||26 Dec 2012 11:20|
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