Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

A clean broad iron line in GS 1354--64 as seen by XRISM

Honghui Liu, Lingda Kong, Oluwashina K. Adegoke, Jiachen Jiang, Cosimo Bambi, Andrew C. Fabian, Adam Ingram, Swati Ravi, James F. Steiner, Qingcang Shui, Dominic J. Walton, Yerong Xu, Andrew J. Young, Yuexin Zhang, Zuobin Zhang, Andrea Santangelo

Abstract

We present a spectroscopic analysis of XRISM and NuSTAR observations of the black hole X-ray binary GS~1354--64 during its 2026 outburst. A total number of 3.5 million photons are collected by the microcalorimeter Resolve on board XRISM, providing an unprecedented high-resolution view of the iron line profile. A clean broad iron line is found in the data, without significant narrow features. Modeling the broad iron line with relativistic reflection from the inner accretion disk suggests a rapidly spinning black hole (a>0.98) in the system. Measurements of the disk inclination angle from the reflection method are model-dependent. This work demonstrates the power of X-ray microcalorimeters in studying the inner accretion flow and constraining black hole parameters.

A clean broad iron line in GS 1354--64 as seen by XRISM

Abstract

We present a spectroscopic analysis of XRISM and NuSTAR observations of the black hole X-ray binary GS~1354--64 during its 2026 outburst. A total number of 3.5 million photons are collected by the microcalorimeter Resolve on board XRISM, providing an unprecedented high-resolution view of the iron line profile. A clean broad iron line is found in the data, without significant narrow features. Modeling the broad iron line with relativistic reflection from the inner accretion disk suggests a rapidly spinning black hole (a>0.98) in the system. Measurements of the disk inclination angle from the reflection method are model-dependent. This work demonstrates the power of X-ray microcalorimeters in studying the inner accretion flow and constraining black hole parameters.
Paper Structure (11 sections, 5 figures, 2 tables)

This paper contains 11 sections, 5 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Observations and Data Reduction
  3. XRISM
  4. NuSTAR
  5. Strictly simultaneously datasets
  6. Spectral Analysis
  7. Reflection features
  8. Reflection analysis
  9. Simultaneous dataset
  10. Full dataset
  11. Discussion

Figures (5)

  • Figure 1: The hardness-intensity diagram for GS 1354--64 from MAXI data. The blue data represent the 2015 outburst, while the red and green data represent the 2026 outburst. The magenta star indicate the time of the XRISM and NuSTAR observations analyzed in this work.
  • Figure 2: Lightcurve of the XRISM and NuSTAR observations of GS 1354--64. The time resolution is 100 s. The red data represent overlapping time intervals between the two instruments. The simultaneous spectral dataset is extracted from these overlapping intervals.
  • Figure 3: Reflection features in the XRISM and NuSTAR observations of GS 1354--64. The data are fitted with a simple absorbed continuum model: Tbabs*Cutoffpl. The plot is only for illustration purposes and the data are binned for visual clarity. The broad excess around 6--7 keV and the hump near 30 keV indicate the presence of a relativistic reflection component.
  • Figure 4: Total spectra (upper panel) and residuals (lower panels) for the strictly simultaneous dataset fitted with Models 1 and 2. In the upper panel, the separate coronal and reflection components for Model 1 are also shown. The data are binned for visual clarity. The color coding is the same as in Figure \ref{['ironline']}.
  • Figure 5: Data-to-model ratio plot for the Resolve-only time-averaged data fitted with Model 1. For visual clarity, the data are divided into four energy panels.