TY  - JOUR
A1  - Toala, Jesús Alberto
A1  - Guerrero, Martín A.
A1  - Todt, Helge Tobias
A1  - Hamann, Wolf-Rainer
A1  - Chu, Y.-H.
A1  - Gruendl, R. A.
A1  - Schönberner, Detlef
A1  - Oskinova, Lida
A1  - Marquez-Lugo, R. A.
A1  - Fang, X.
A1  - Ramos-Larios, Gerardo
T1  - The born-again Planetary nebula A78: an X-RAY twin of A30
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We present the XMM-Newton discovery of X-ray emission from the planetary nebula (PN) A78, the second born-again PN detected in X-rays apart from A30. These two PNe share similar spectral and morphological characteristics: they harbor diffuse soft X-ray emission associated with the interaction between the H-poor ejecta and the current fast stellar wind and a point-like source at the position of the central star (CSPN). We present the spectral analysis of the CSPN, using for the first time an NLTE code for expanding atmospheres that takes line blanketing into account for the UV and optical spectra. The wind abundances are used for the X-ray spectral analysis of the CSPN and the diffuse emission. The X-ray emission from the CSPN in A78 can be modeled by a single C VI emission line, while the X-ray emission from its diffuse component is better described by an optically thin plasma emission model with a temperature of kT = 0.088 keV (T approximate to 1.0 x 10(6) K). We estimate X-ray luminosities in the 0.2-2.0 keV energy band of L-X,L-CSPN =(1.2 +/- 0.3) x 10(31) erg s(-1) and L-X,L-DIFF =(9.2 +/- 2.3) x 10(30) erg s(-1) for the CSPN and diffuse components, respectively.
KW  - planetary nebulae: general
KW  - planetary nebulae: individual (A78)
KW  - stars: winds, outflows
KW  - X-rays: ISM
Y1  - 2015
U6  - https://doi.org/10.1088/0004-637X/799/1/67
SN  - 0004-637X
SN  - 1538-4357
VL  - 799
IS  - 1
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  -