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The Keck Aperture Masking Experiment: dust-enshrouded red giants

Blasius, T. D. and Monnier, J. D. and Tuthill, P. G. and Danchi, W. C. and Anderson, M. (2012) The Keck Aperture Masking Experiment: dust-enshrouded red giants. Monthly Notices of the Royal Astronomical Society, 426 (4). pp. 2652-2667. ISSN 0035-8711. https://resolver.caltech.edu/CaltechAUTHORS:20121126-103306963

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Abstract

While the importance of dusty asymptotic giant branch (AGB) stars to galactic chemical enrichment is widely recognized, a sophisticated understanding of the dust formation and wind-driving mechanisms has proven elusive due in part to the difficulty in spatially resolving the dust-formation regions themselves. We have observed 20 dust-enshrouded AGB stars as part of the Keck Aperture Masking Experiment, resolving all of them in multiple near-infrared bands between 1.5 and 3.1  μm. We find 45 per cent of the targets to show measurable elongations that, when correcting for the greater distances of the targets, would correspond to significantly asymmetric dust shells at par with the well-known cases of IRC + 10216 or CIT 6. Using radiative transfer models, we find the sublimation temperature of T_sub (silicates) = 1130 ± 90 K and T_sub (amorphous carbon) = 1170 ± 60 K, both somewhat lower than expected from laboratory measurements and vastly below temperatures inferred from the inner edge of young stellar objects discs. The fact that O-rich and C-rich dust types showed the same sublimation temperature was surprising as well. For the most optically thick shells (τ_2.2μm > 2) , the temperature profile of the inner dust shell is observed to change substantially, an effect we suggest could arise when individual dust clumps become optically thick at the highest mass-loss rates.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1111/j.1365-2966.2012.21543.xDOIArticle
ORCID:
AuthorORCID
Monnier, J. D.0000-0002-3380-3307
Additional Information:© 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS. Accepted 2012 June 18. Received 2012 June 7; in original form 2012 March 31. Article first published online: 17 Oct. 2012. We thank Dr Charles Townes for his long-standing support of this work. We also thank Angela Speck for her insightful comments upon reading a draft of this manuscript. We acknowledge interesting discussions with Peter Woitke regarding the effect of clumpy structures on the temperature profile, and we thank Rita Loidl Gautschy for her help in acquiring the C-star synthetic spectrum. This research has made use of the SIMBAD data base, operated at CDS, Strasbourg, France. This publication makes use of data products from the Two Micron All Sky Survey (2MASS), which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Keck Observatory was made possible by the generous financial support of the W. M. Keck Foundation. We wish to recognize and acknowledge the very significant cultural role and reverence that the summit ofMauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
Funders:
Funding AgencyGrant Number
NASAUNSPECIFIED
NSFUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:radiative transfer; instrumentation: interferometers; circumstellar matter
Issue or Number:4
Record Number:CaltechAUTHORS:20121126-103306963
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20121126-103306963
Official Citation:Blasius, T. D., Monnier, J. D., Tuthill, P. G., Danchi, W. C. and Anderson, M. (2012), The Keck Aperture Masking Experiment: dust-enshrouded red giants. Monthly Notices of the Royal Astronomical Society, 426: 2652–2667. doi: 10.1111/j.1365-2966.2012.21543.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35630
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:26 Nov 2012 21:49
Last Modified:09 Mar 2020 13:19

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