X Herculis and TX Piscium: two cases of ISM interaction with stellar winds observed by Herschel
Journal article, 2011
The asymptotic giant branch (AGB) stars X Her and TX Psc have been imaged at 70 and 160 μm with the PACS instrument onboard the Herschel satellite, as part of the large MESS (Mass loss of Evolved StarS) guaranteed time key program. The images reveal an axisymmetric extended structure with its axis oriented along the space motion of the stars. This extended structure is very likely to be shaped by the interaction of the wind ejected by the AGB star with the surrounding interstellar medium (ISM). As predicted by numerical simulations, the detailed structure of the wind-ISM interface depends upon the relative velocity between star+wind and the ISM, which is large for these two stars (108 and 55 km s-1 for X Her and TX Psc, respectively). In both cases, there is a compact blob upstream whose origin is not fully elucidated, but that could be the signature of some instability in the wind-ISM shock. Deconvolved images of X Her and TX Psc reveal several discrete structures along the outermost filaments, which could be Kelvin-Helmholtz vortices. Finally, TX Psc is surrounded by an almost circular ring (the signature of the termination shock?) that contrasts with the outer, more structured filaments. A similar inner circular structure seems to be present in X Her as well, albeit less clearly.
stars: AGB and post-AGB
ISM: general
stars: mass-loss
infrared: stars
stars: carbon
Author
A. Jorissen
Université libre de Bruxelles (ULB)
A. Mayer
University of Vienna
S. Van Eck
Université libre de Bruxelles (ULB)
R. Ottensamer
Technische Universität Graz
University of Vienna
F. Kerschbaum
University of Vienna
T. Ueta
University of Denver
Per Bergman
Chalmers, Earth and Space Sciences, Onsala Space Observatory
Jadl Blommaert
KU Leuven
L. Decin
KU Leuven
M. A. T. Groenewegen
Royal Observatory of Belgium
J. Hron
University of Vienna
W. Nowotny
University of Vienna
Hans Olofsson
Chalmers, Earth and Space Sciences, Onsala Space Observatory
T. Posch
University of Vienna
Loránt Olivér Sjouwerman
National Radio Astronomy Observatory Socorro
B. Vandenbussche
KU Leuven
C. Waelkens
KU Leuven
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 532 A135Subject Categories
Astronomy, Astrophysics and Cosmology
Roots
Basic sciences
DOI
10.1051/0004-6361/201116927