English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We analyze the high-resolution X-ray spectrum of the supergiant O-star deltaOrionis (O9.5II) with line ratios of He-like ions and a thermal plasma model,and we examine its variability. The O-supergiant delta Ori was observed in thewavelength range 5-175 Angstrom by the X-ray detector HRC-S in combination withthe grating LETG aboard Chandra. We studied the He-like ions in combinationwith the UV-radiation field to determine local plasma temperatures and toestablish the distance of the X-ray emitting ions to the stellar surface. Wemeasured individual lines by means of Gaussian profiles, folded through theresponse matrix, to obtain wavelengths, line fluxes, half widths at halfmaximum (HWHM) and line shifts to characterize the plasma. We considermultitemperature models in collisional ionization equilibrium (CIE) todetermine temperatures, emission measures, and abundances. Analysis of theHe-like triplets extended to N VI and C V implies ionization stratificationwith the hottest plasma to be found within a few stellar radii 3R* (Mg XI) andthe coolest farther out, far beyond the acceleration zone, up to 49R* (N VI)and 75R* (C V). The observed temperatures cover a range from about 0.1 to 0.7keV, i.e., 1-8 MK. The X-ray luminosity L is about 1.5 x 10e+32 erg/s in therange from 0.07 to 3 keV covered by LETGS. Velocity widths of about 1040 km/shave been determined.

The X-ray spectrum of delta Orionis observed by LETGS aboard Chandra