Type I X-ray bursts, burst oscillations and kHz quasi-periodic oscillations in the neutron star system IGR J17191-2821

TL;DR

This study analyzes the spectral and timing properties of the neutron star system IGR J17191-2821, revealing kHz QPOs, burst oscillations, and outburst behavior, confirming its classification as an atoll source.

Contribution

First detailed spectral and timing analysis of IGR J17191-2821, discovering kHz QPOs, burst oscillations, and outburst precursors, establishing its atoll source nature.

Findings

Detected four pairs of kHz QPOs with frequencies 315-362 Hz

Observed five thermonuclear type-I X-ray bursts with burst oscillations at ~294 Hz

Identified a faint outburst precursor two months before the main outburst

Abstract

We present a detailed study of the X-ray energy and power spectral properties of the neutron star transient IGR J17191-2821. We discovered four instances of pairs of simultaneous kilohertz quasi-periodic oscillations (kHz QPOs). The frequency difference between these kHz QPOs is between 315 Hz and 362 Hz. We also report on the detection of five thermonuclear type-I X-ray bursts and the discovery of burst oscillations at ~294 Hz during three of them. Finally, we report on a faint and short outburst precursor, which occurred about two months before the main outburst. Our results on the broadband spectral and variability properties allow us to firmly establish the atoll source nature of IGR J17191-2821.