THE CHANDRA PLANETARY NEBULA SURVEY (ChanPlaNS). III. X-RAY EMISSION FROM THE CENTRAL STARS OF PLANETARY NEBULAE

Abstract

We present X-ray spectral analysis of 20 point-like X-ray sources detected in Chandra Planetary Nebula Survey observations of 59 planetary nebulae (PNe) in the solar neighborhood. Most of these 20 detections are associated with luminous central stars within relatively young, compact nebulae. The vast majority of these point-like X-rayemitting sources at PN cores display relatively "hard" ( 0.5 keV) X-ray emission components that are unlikely to be due to photospheric emission from the hot central stars (CSPN). Instead, we demonstrate that these sources are well modeled by optically thin thermal plasmas. From the plasma properties, we identify two classes of CSPN X-ray emission: (1) high-temperature plasmas with X-ray luminosities, L X , that appear uncorrelated with the CSPN bolometric luminosity, L bol and (2) lower-temperature plasmas with L X /L bol ∼ 10 −7 . We suggest these two classes correspond to the physical processes of magnetically active binary companions and self-shocking stellar winds, respectively. In many cases this conclusion is supported by corroborative multiwavelength evidence for the wind and binary properties of the PN central stars. By thus honing in on the origins of X-ray emission from PN central stars, we enhance the ability of CSPN X-ray sources to constrain models of PN shaping that invoke wind interactions and binarity.

A catalogue of 108 extended planetary nebulae observed by GALEX

“…It is also demonstrated that the Xray fluxes from shocks are necessary to explain the UV emission from high ionization species of oxygen (O VI and O VII) in the coolest CSPNe and can also play a role at higher CSPN temperatures Kaschinski et al 2012;Guerrero & De Marco 2013). Recently there have been several observations of PNe by Chandra X-ray observatory and XMM-Newton which have discovered both X-ray diffuse and point like observations (Soker & Kastner 2003;Kastner et al 2012;Freeman et al 2014;Montez et al 2015). We found six X-ray detections in our sample (PN G066.7−28.2, PN G083.5+12.7, PN G096.4+29.9, & PN G165.5−15.2 from Montez et al (2015), and PN G084.9−03.4, and PN G226.7+05.6 from Soker & Kastner (2003)), which contain point-like sources.…”

Stellar wind models of central stars of planetary nebulae

“…Some planetary nebulae are sources of X-ray emission, which may have a diffuse component coming from the nebula (e.g., Chu et al 2001, Heller et al 2018) and a point-source component associated with the central star (Freeman et al 2014, Montez et al 2015). X-ray emission of O stars, which is supposed to originate in their winds (Feldmeier et al 1997), shows a strong correlation between the X-ray luminosity and stellar luminosity roughly as L X ≈ 10 −7 L (Nazé 2009).…”

“…X-ray emission of O stars, which is supposed to originate in their winds (Feldmeier et al 1997), shows a strong correlation between the X-ray luminosity and stellar luminosity roughly as L X ≈ 10 −7 L (Nazé 2009). We compared the relation between the X-ray luminosity and the stellar luminosity of CSPNe derived from Chandra data (Montez et al 2015) with corresponding relations obtained for O stars and subdwarfs ( Fig. 7).…”

“…7. Relation between observed X-ray luminosities and bolometric luminosities for CSPNe (Montez et al 2015) and subdwarfs (Montez et al 2010, La Palombara et al 2012, 2014, Mereghetti et al 2013. We overplotted the mean relation for O stars (Nazé 2009, blue solid line) and the wind kinetic energy loss per unit of time (red dashed line; derived using v ∞ = 1000 km s −1 and mass-loss rate from Eq.…”

X-ray Shaping of Planetary Nebulae

“…These Chandra X-ray observations have made clear that the detections of diffuse X-ray emission is always confined within sharp closed innermost optical shells, i.e., the hot bubbles [8,26]. So far, there is no evidence of X-ray emission associated with fast collimated outflows, but for the highly collimated ultrafast (>1000 km s −1 ) proto-PN Hen 3-1475 [32].…”