TY - JOUR
T1 - X Herculis and TX Piscium
T2 - Two cases of ISM interaction with stellar winds observed by Herschel
AU - Jorissen, A.
AU - Mayer, A.
AU - Van Eck, S.
AU - Ottensamer, R.
AU - Kerschbaum, F.
AU - Ueta, T.
AU - Bergman, P.
AU - Blommaert, J. A.D.L.
AU - Decin, L.
AU - Groenewegen, M. A.T.
AU - Hron, J.
AU - Nowotny, W.
AU - Olofsson, H.
AU - Posch, Th
AU - Sjouwerman, L. O.
AU - Vandenbussche, B.
AU - Waelkens, C.
PY - 2011/8/5
Y1 - 2011/8/5
N2 - 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.
AB - 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.
KW - Infrared: stars
KW - ISM: general
KW - Stars: AGB and post-AGB
KW - Stars: carbon
KW - Stars: mass-loss
UR - http://www.scopus.com/inward/record.url?scp=79961219441&partnerID=8YFLogxK
U2 - 10.1051/0004-6361/201116927
DO - 10.1051/0004-6361/201116927
M3 - Article
AN - SCOPUS:79961219441
SN - 0004-6361
VL - 532
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A135
ER -