TY - JOUR
T1 - IRC+10216'S innermost envelope-the eSMA'S view
AU - Shinnaga, Hiroko
AU - Young, Ken H.
AU - Tilanus, Remo P.J.
AU - Chamberlin, Richard
AU - Gurwell, Mark A.
AU - Wilner, David
AU - Hughes, A. Meredith
AU - Yoshida, Hiroshige
AU - Peng, Ruisheng
AU - Force, Brian
AU - Friberg, Per
AU - Bottinelli, Sandrine
AU - Van Dishoeck, Ewine F.
AU - Phillips, Thomas G.
N1 - Funding Information:
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.
Funding Information:
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.
Publisher Copyright:
© 2009 The American Astronomical Society. All rights reserved. Printed in the U.S.A.
PY - 2009/6/20
Y1 - 2009/6/20
N2 - 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 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.
AB - 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 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.
KW - Circumstellar matter
KW - Masers
KW - Stars: AGB and post-AGB
KW - Stars: individual (IRC+10216)
KW - Stars: mass loss
KW - Stars: winds, outflows
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U2 - 10.1088/0004-637X/698/2/1924
DO - 10.1088/0004-637X/698/2/1924
M3 - Article
AN - SCOPUS:78649356142
SN - 0004-637X
VL - 698
SP - 1924
EP - 1933
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
ER -