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 a NLTE code for expanding atmospheres which 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 temperature kT =0.088 keV ( T \approx 1.0 \times 10 ^ { 6 } K ) .
We estimate X-ray luminosities in the 0.2–2.0 keV energy band of L _ { \mathrm { X,CSPN } } = ( 1.2 \pm 0.3 ) \times 10 ^ { 31 } erg s ^ { -1 } and L _ { \mathrm { X,DIFF } } = ( 9.2 \pm 2.3 ) \times 10 ^ { 30 } erg s ^ { -1 } for the CSPN and diffuse components , respectively .