Issue |
A&A
Volume 514, May 2010
Science with AKARI
|
|
---|---|---|
Article Number | A16 | |
Number of page(s) | 6 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361/200913455 | |
Published online | 03 May 2010 |
The interface between the stellar wind and interstellar medium around R Cassiopeiae revealed by far-infrared imaging*
1
Department of Physics and Astronomy, University of Denver,
2112 E. Wesley Ave., Denver, CO 80208, USA e-mail: tueta@du.edu
2
Institute of Space and Aeronautical Science,
Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara,
Kanagawa 229-8510, Japan
3
Max-Planck-Institut für Extraterrestrische Physik,
Giessenbachstraat 1, 85748 Garching, Germany
4
Leiden Observatory, Leiden University, PO Box 9513,
2300 RA Leiden, The Netherlands
5
Okayama Astrophysical Observatory, National
Astronomical Observatory, Kamogata, Asakuchi, Okayama 719-0232, Japan
6
Institute of Astronomy, School of Science,
University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
7
Department of Physics and Astronomy, University
College London, Gower Street, London WC1E 6BT, UK
8
Mullard Space Science Laboratory, University
College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
9
National Astronomical Observatory of Japan, 2-21-1
Osawa, Mitaka, Tokyo 181-8588, Japan
10
Kiso Observatory, Institute of Astronomy, School of
Science, University of Tokyo, Mitake, Kiso, Nagano 397-0101, Japan
11
Department of Physics & Astronomy, University of Missouri,
Columbia, MO 65211, USA
Received:
12
October
2009
Accepted:
6
November
2009
Aims. The circumstellar dust shells of intermediate initial-mass (~1 to
8 ) evolved stars are generated by copious mass loss during
the asymptotic giant branch phase.
The density structure of their circumstellar shell is the direct
evidence of mass loss processes, from which we can investigate the
nature of mass loss.
Methods. We used the AKARI infrared astronomy satellite and the Spitzer space telescope to obtain the surface brightness maps of an evolved star R Cas at far-infrared wavelengths, since the temperature of dust decreases as the distance from the star increases and one needs to probe dust at lower temperatures, i.e., at longer wavelengths. The observed shell structure and the star's known proper motion suggest that the structure represents the interface regions between the dusty wind and the interstellar medium. The deconvolved structures are fitted with the analytic bow shock structure to determine the inclination angle of the bow shock cone.
Results. Our data show that (1) the bow shock cone of 1 – 5 × 10-5
dust mass is inclined
at 68° with respect to the
plane of the sky; and (2) the dust temperature in the bow shock cone is
raised to more than 20 K by collisional shock interaction in addition to
the ambient interstellar radiation field.
By comparison between the apex vector of the bow shock and space motion
vector of the star we infer that there is a flow of interstellar medium
local to R Cas whose flow velocity is at least 55.6 km s-1,
consistent with an environment conducive to dust heating by shock
interactions.
Key words: circumstellar matter / infrared: stars / stars: AGB and post-AGB / stars: individual: R Cas / stars: mass loss / ISM: kinematics and dynamics
© ESO, 2010
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