Jets, accretion, coronae and all that: The enigmatic X-rays from the Herbig star HD 163296

TL;DR

This study analyzes X-ray emissions from the Herbig star HD 163296, revealing multiple temperature components and suggesting a jet shock origin for soft X-rays and a coronal origin for hot X-rays, advancing understanding of HAeBe star emissions.

Contribution

First detailed X-ray spectral analysis of HD 163296, proposing a jet shock origin for soft X-rays and a coronal origin for hot X-rays in Herbig Ae/Be stars.

Findings

Three temperature components identified (0.2 keV to 2.7 keV)

X-ray formation region likely above stellar surface

Jet shock and coronal origins proposed for different X-ray components

Abstract

Herbig Ae/Be stars (HAeBe) are pre-main sequence objects in the mass range between 2 and 8 solar masses. Their X-ray properties are uncertain and, as yet, unexplained. We want to elucidate the X-ray generating mechanism in HAeBes. We present a XMM-Newton observation of the HAeBe HD 163296. We analyse the light curve, the broad band and the grating spectra, fit emission measures and abundances and apply models for accretion and wind shocks. We find three temperature components ranging from 0.2 keV to 2.7 keV. The O VII He-like triplet indicates a X-ray formation region in a low density environment with a weak UV photon field, i. e. above the stellar surface. This makes an origin in an accretion shock unlikely, instead we suggest a shock at the base of the jet for the soft component and a coronal origin for the hot component. A mass outflow of 10^{-10} solar masses per year is sufficient to power the soft X-rays. HD 163296 is thought to be single, so this data represent genuine HAeBe X-ray emission. HD 163296 might be prototypical for its class.