Detached shells as tracers of asymptotic giant branch-interstellar medium bow shocks

New Spitzer imaging observations have revealed the structure around the Mira variable star R Hya to be a one-sided parabolic arc 100 arcsec to the west, stretching from north to south. We successfully model R Hya and its surroundings in terms of an interaction of the stellar wind from an asymptotic giant branch (AGB) star with the interstellar medium (ISM) the star moves through. Our three-dimensional hydrodynamic simulation reproduces the structure as a bow shock into the oncoming ISM. We propose this as another explanation of detached shells around such stars, which should be considered alongside current theories of internal origin. The simulation predicts the existence of a tail of ram-pressure-stripped AGB material stretching downstream. Indications for such a tail behind R Hya are seen in IRAS maps.

[1]  A. Zijlstra,et al.  The shaping of planetary nebula Sh 2 − 188 through interaction with the interstellar medium , 2013 .

[2]  S. Falle,et al.  Dynamical and pressure structures in winds with multiple embedded evaporating clumps – I. Two-dimensional numerical simulations , 2005, astro-ph/0506342.

[3]  Properties of detached shells around carbon stars Evidence of interacting winds , 2005, astro-ph/0503245.

[4]  Paul S. Smith,et al.  The Multiband Imaging Photometer for Spitzer (MIPS) , 2004 .

[5]  E. Wright,et al.  The Spitzer Space Telescope Mission , 2004, astro-ph/0406223.

[6]  F. Crifo,et al.  3D mapping of the dense interstellar gas around the Local Bubble , 2003 .

[7]  H. E. Schwarz,et al.  Imaging polarimetry of stellar light scattered in detached shells around the carbon stars R Scl and U Ant , 2003 .

[8]  Ram Pressure Stripping in Planetary Nebulae , 2003, astro-ph/0301307.

[9]  The evolution of the Mira variable R Hydrae , 2002, astro-ph/0203328.

[10]  A. Zijlstra,et al.  A Wall of Dust around a Proto-Mira? , 2002, astro-ph/0203326.

[11]  D. Van Buren,et al.  A Robotic Wide‐Angle Hα Survey of the Southern Sky , 2001, astro-ph/0108518.

[12]  H. E. Schwarz,et al.  Imaging of detached shells around the carbon stars R Scl and U Ant through scattered stellar light , 2001, astro-ph/0104140.

[13]  G. Knapp,et al.  Discovery of Parsec-sized Dust Shells around AFGL 2688 and AFGL 618 , 2000 .

[14]  M. Feast,et al.  Mira kinematics from Hipparcos data: a Galactic bar to beyond the Solar circle , 2000 .

[15]  M. Feast,et al.  Mira kinematics from Hipparcos data: a Galactic bar to beyond the Solar circle , 2000, astro-ph/0004107.

[16]  P. Wood,et al.  Evolution of Low- and Intermediate-Mass Stars to the End of the Asymptotic Giant Branch with Mass Loss , 1993 .

[17]  G. Knapp,et al.  Circumstellar shells resolved in IRAS survey data. II - Analysis , 1993 .

[18]  S. Falle.  Self-similar jets , 1991 .

[19]  O. Eggen.  A systematic search for members of the Hyades supercluster. V. The red giants. , 1985 .

[20]  M. S. Roberts.  Galactic astronomy. , 1981, Science.

[21]  Lyman Spitzer,et al.  Physical processes in the interstellar medium , 1998 .

[22]  B. Smith,et al.  Radiative cooling of a low-density plasma , 1971 .

[23]  R. Wilson,et al.  General Catalogue of Stellar Radial Velocities , 1953 .