Synthetic X-ray emission from white dwarf accreting planetary material

Publication date: 
Main author: 
Estrada-Dorado, S.
IAA authors: 
Guerrero, M. A.
Estrada-Dorado, S.;Lora, V.;Toalá, J. A.;Esquivel, A.;Guerrero, M. A.;Maldonado, R. F.;Chu, Y. -H.
Monthly Notices of the Royal Astronomical Society
Publication type: 
The emission of hard X-rays associated with white dwarfs (WDs) can be generated by the presence of a stellar companion, either by the companion's coronal emission or by an accretion disc formed by the material stripped from the companion. Recent studies have suggested that a Jupiter-like planet can also be a donor of the material whose accretion on to the WD can generate hard X-rays. We use the GUACHO code to reproduce the conditions of this WD-planet scenario. With the example of the hard X-ray WD KPD 0005+5106, we explore different terminal wind velocities and mass-loss rates of a donor planet for a future network of simulations to investigate the luminosity and the spectral and temporal properties of the hard X-ray emission in the WD-planet systems. Our simulations show that the material stripped from the planet forms a disc and accretes on to the WD to reach temperatures high enough to generate hard X-rays as usually seen in X-ray binaries with low-mass companions. For high terminal wind velocities, the planet material does not form a disc, but it rather accretes directly on to the WD surface. The simulations reproduce the X-ray luminosity of another X-ray accreting WD (G 29-38), and only sometimes reaches the hard X-ray luminosity of KPD 0005+5106. The X-ray variability is stochastic and does not reproduce the period of KPD 0005+5106, suggesting that the additional physical processes (e.g. hot spots resulting from magnetic channelling of the accreting material) need to be explored.
ADS Bibcode: 
stars: evolution;stars: low-mass;white dwarfs;X-rays: individual: KPD 0005+5106;G 29-38;Astrophysics - Solar and Stellar Astrophysics;Astrophysics - Earth and Planetary Astrophysics;Astrophysics - High Energy Astrophysical Phenomena