Variable Hard X-Ray Emission from the Central Star of the Eskimo Nebula

DOI: 
10.3847/1538-4357/ab4256
Publication date: 
01/10/2019
Main author: 
Guerrero, Martín A.
IAA authors: 
Guerrero, Martín A.
Authors: 
Guerrero, Martín A.;Toalá, Jesús A.;Chu, You-Hua
Journal: 
The Astrophysical Journal
Refereed: 
Yes
Publication type: 
Article
Volume: 
884
Pages: 
134
Abstract: 
The central star of NGC 2392 shows the hardest X-ray emission among central stars of planetary nebulae (CSPNe). The recent discovery of a spectroscopic companion with an orbital period of 1.9 days could provide an explanation for its hard X-ray emission, as well as for the collimation of its fast outflow. Here, we analyze the available Chandra and XMM-Newton X-ray observations to determine accurately the spectral and temporal variation properties of the CSPN of NGC 2392. The X-ray emission can be described by an absorbed thermal plasma model with temperature {26}<SUB>-5</SUB><SUP>+8</SUP> MK and X-ray luminosity (8.7 ± 1.0) × 10<SUP>30</SUP> erg s<SUP>−1</SUP>. No long-term variability is detected in the X-ray emission level, but the Chandra light curve is suggestive of short-term variations with a period ∼0.26 days. The possible origins of this X-ray emission are discussed. X-ray emission from the coronal activity of a companion or shocks in the stellar wind can be ruled out. Accretion of material from an unseen main-sequence companion onto the CSPN or from the CSPN wind onto a white dwarf companion are the most plausible origins for its hard X-ray emission, although the mismatch between the rotational period of the CSPN and the modulation timescale of the X-ray emission seems to preclude the former possibility.
Database: 
ADS
SCOPUS
URL: 
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075180388&doi=10.3847%2f1538-4357%2fab4256&partnerID=40&md5=41e50a198379f0b5b967fbfbf561da06
ADS Bibcode: 
2019ApJ...884..134G
Keywords: 
Planetary nebulae;Planetary nebulae nuclei;X-ray stars;Stellar winds;Astrophysics - Solar and Stellar Astrophysics;Astrophysics - High Energy Astrophysical Phenomena