TY  - JOUR
A1  - Fang, X.
A1  - Guerrero, Martín A.
A1  - Marquez-Lugo, R. A.
A1  - Toala, Jesús Alberto
A1  - Arthur, S. J.
A1  - Chu, Y.-H.
A1  - Blair, William P.
A1  - Gruendl, R. A.
A1  - Hamann, Wolf-Rainer
A1  - Oskinova, Lida
A1  - Todt, Helge Tobias
T1  - Expansion of hydrogen-poor knots in the born-again planetary nebulae A30 and A78
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We analyze the expansion of hydrogen-poor knots and filaments in the born-again planetary nebulae A30 and A78 based on Hubble Space Telescope ( HST) images obtained almost 20 yr apart. The proper motion of these features generally increases with distance to the central star, but the fractional expansion decreases, i.e., the expansion is not homologous. As a result, there is not a unique expansion age, which is estimated to be 610-950 yr for A30 and 600-1140 yr for A78. The knots and filaments have experienced complex dynamical processes: the current fast stellar wind is mass loaded by the material ablated from the inner knots; the ablated material is then swept up until it shocks the inner edges of the outer, hydrogen-rich nebula. The angular expansion of the outer filaments shows a clear dependence on position angle, indicating that the interaction of the stellar wind with the innermost knots channels the wind along preferred directions. The apparent angular expansion of the innermost knots seems to be dominated by the rocket effect of evaporating gas and by the propagation of the ionization front inside them. Radiation-hydrodynamical simulations show that a single ejection of material followed by a rapid onset of the stellar wind and ionizing flux can reproduce the variety of clumps and filaments at different distances from the central star found in A30 and A78.
KW  - ISM: kinematics and dynamics
KW  - planetary nebulae: individual (A30 and A78)
Y1  - 2014
U6  - https://doi.org/10.1088/0004-637X/797/2/100
SN  - 0004-637X
SN  - 1538-4357
VL  - 797
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Toalá, Jesús Alberto
A1  - Guerrero, Martín A.
A1  - Chu, Y.-H.
A1  - Arthur, S. J.
A1  - Gruendl, R. A.
T1  - Diffuse X-ray Emission within Wolf-Rayet Nebulae
JF  - Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.–5. June 2015
N2  - We discuss our most recent findings on the diffuse X-ray emission within Wolf-Rayet (WR) nebulae. The best-quality X-ray observations of these objects are those performed by XMM- Newton and Chandra towards S 308, NGC 2359, and NGC 6888. Even though these three WR nebulae might have different formation scenarios, they all share similar characteristics: i) the main plasma temperatures of the X-ray-emitting gas is found to be T =[1–2]×^K, ii) the diffuse X-ray emission is confined inside the [O iii] shell, and iii) their X-ray luminosities and electron densities in the 0.3–2.0 keV energy range are LX ≈10^33–10^34 erg s-1  and ne ≈0.1–1 cm^-3 . These properties and the nebular-like abundances of the hot gas suggest mixing and/or thermal conduction is taking an important rôle reducing the temperature of the hot bubble.
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-88316
SP  - 333
EP  - 336
ER  - 
TY  - JOUR
A1  - Arthur, S. J.
T1  - Wolf-Rayet nebulae and the wind-interstellar medium interaction
JF  - Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.–5. June 2015
N2  - I review our current understanding of the interaction between a Wolf-Rayet star's fast wind and the surrounding medium, and discuss to what extent the predictions of numerical simulations coincide with multiwavelength observations of Wolf-Rayet nebulae. Through a series of examples, I illustrate how changing the input physics affects the results of the numerical simulations. Finally, I discuss how numerical simulations together with multiwavelength observations of these objects allow us to unpick the previous mass-loss history of massive stars.
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-88267
SP  - 315
EP  - 320
ER  -