Relativistic X-ray Reflection Models for Accreting Neutron Stars

Abstract

We present new reflection models specifically tailored to model the X-ray radiation reprocessed in accretion disks around neutron stars, in which the primary continuum is characterized by a single temperature blackbody spectrum, emitted either at the surface of the star, or at the boundary layer. These models differ significantly from those with a standard power-law continuum, typically observed in most accreting black holes. We show comparisons with earlier reflection models, and test their performance in the NuSTAR observation of the neutron star 4U 1705−44. Simulations of upcoming missions such as XRISM-Resolve and Athena X-IFU are shown to highly the diagnostic potential of these models for high-resolution X-ray reflection spectroscopy. These new reflection models xillverNS, and their relativistic counterpart relxillNS, are made publicly available to the community as an additional flavor in the relxill suite of reflection models.

NICER observations of the evidence of Poynting-Robertson drag and disk reflection during type I X-ray bursts from 4U 1636$-$536

“…The deviations from the blackbody model of the burst spectra can also be explained by the disk reflection. In order to correctly characterize the reflection features in the burst spectra, we use the latest relativistic reflection model, relxillNS, 5 of a photoionized accretion disk illuminated by a blackbody spectrum from NS (García et al 2021). This model has been successfully fitted the continuum of NS and black hole LMXBs (Ludlam et al 2019;Connors et al 2020).…”