SHAPING THE DIFFUSE X-RAY SKY: STRUCTURE, VARIABILITY AND VISIBILITY

Girichidis P, Rea E, Klessen RS, Yeung MC, Maconi E, Sasaki M, Freyberg M, Soler JD (2026)

Publication Type: Journal article

Publication year: 2026

Book Volume: 9

Abstract

The Local Bubble (LB) is a hot, low-density cavity in the solar neighborhood, inside which the Solar System is currently located. The X-ray emission from such bubbles is strongly governed by the gas density, temperature, and the effects of line-of-sight column density. Yet the physical processes that control the formation and evolution of this emission remain incompletely understood. We analyze a LB analogue identified within a magnetohydrodynamical simulation to investigate the key physical factors that shape its X-ray properties. In post-processing, we examine the spatial distribution, variability, and observational constraints of the X-ray emission. Our study reveals three main results: (1) Shortly after a supernova (SN), the bulk of the X-ray emission arises from a small fraction of the bubble’s volume, concentrated in hot regions around recent SN sites. Approximately 95% of the X-ray luminosity originates from less than 1% of the total bubble volume. During quiescent phases without recent SNe, the emission morphology changes substantially, with X-ray-bright regions becoming more volume-filling. (2) Column density effects strongly modulate the observable X-ray signal. Gas with column densities exceeding NH ≳ 10²⁰ cm⁻² efficiently absorbs soft X-ray photons, limiting the depth to which observations can probe. This absorption causes a significant fraction of the sky to be obscured from external soft X-rays. Differences between active and quiescent phases further influence how much of the total bubble emission is visible from within. (3) The X-ray flux shows pronounced temporal variability on Myr timescales, with SN events producing rapid, transient luminosity enhancements, followed by steep declines due to adiabatic cooling. The total flux varies by several orders of magnitude, with SN-driven peaks fading within 10⁵ years. Subject headings: ISM:bubbles, Local Bubble, X-rays, magneto-hydrodynamics.

Authors with CRIS profile

Manami Sasaki Professur für Multiwellenlängenastronomie

Involved external institutions

Ruprecht-Karls-Universität Heidelberg

Germany (DE) Max-Planck-Institut für extraterrestrische Physik (MPE) / Max Planck Institute for Extraterrestrial Physics

Germany (DE) Universität Wien / University of Vienna

Austria (AT) National Institute for Astrophysics / Istituto Nazionale Astrofisica (INAF)

Italy (IT)

How to cite

APA:

Girichidis, P., Rea, E., Klessen, R.S., Yeung, M.C., Maconi, E., Sasaki, M.,... Soler, J.D. (2026). SHAPING THE DIFFUSE X-RAY SKY: STRUCTURE, VARIABILITY AND VISIBILITY. , 9. https://doi.org/10.33232/001c.159505

MLA:

Girichidis, Philipp, et al. "SHAPING THE DIFFUSE X-RAY SKY: STRUCTURE, VARIABILITY AND VISIBILITY." 9 (2026).

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