The Magnificent Seven in the dusty prairie -- The role of interstellar absorption on the observed neutron star population

TL;DR

This paper investigates how interstellar absorption affects the observed properties of neutron stars, especially those farther away, by modeling the 3D distribution of interstellar hydrogen and testing these models with X-ray sources.

Contribution

It introduces two simple 3D models of interstellar hydrogen distribution based on Local Bubble measurements and evaluates their impact on neutron star observations.

Findings

Models help estimate neutron star distances more accurately.

Interstellar absorption significantly influences observed X-ray spectra.

Potential applications in population synthesis and distance estimation.

Abstract

The Magnificent Seven have all been discovered by their exceptional soft X-ray spectra and high ratios of X-ray to optical flux. They all are considered to be nearby sources. Searching for similar neutron stars with larger distances, one expects larger interstellar absorption resulting in harder X-ray counterparts. Current interstellar absorption treatment depends on chosen abundances and scattering cross-sections of the elements as well as on the 3D distribution of the interstellar medium. After a discussion of these factors we use the comprehensive 3D measurements of the Local Bubble by Lallement et al. 2003 to construct two simple models of the 3D distribution of the hydrogen column density. We test these models by using a set of soft X-ray sources with known distances. Finally, we discuss possible applications for distance estimations and population synthesis studies.