XRISM High-Resolution X-ray Spectroscopy of Cygnus X-1 -- highly ionized Iron absorption structures

Abstract

We present the first high-resolution X-ray spectral analysis of Cygnus X-1 using XRISM. The observation was carried out from April 7 to 10, 2024, covering the orbital phase range 0.65--0.17 during its low/hard state. Taking advantage of the exceptional energy resolution of the Resolve instrument, we examined highly ionized iron absorption lines and characterized the ionization states, column densities, and line-of-sight velocities of the absorbing plasma. Spectral analysis revealed an ionization parameter of approximately 3, column densities of a few times 10^21 cm^-2, and a blueshifted velocity of approximately 100 km s^-1. The observation was divided into two phases: before and after orbital phase phi_orb = 0.9, corresponding to non-dipping and dipping intervals. While only weak absorption features were present before phi_orb = 0.9, strong absorption by He-like and H-like Fe appeared during the dipping phase. We measured equivalent widths of 2.3 eV, 0.4 eV, and 1.2 eV for He-like Fe K-alpha, and H-like Ly-alpha1 and Ly-alpha2, respectively, demonstrating the capability of XRISM Resolve to securely detect narrow absorption features of only a few eV. These measurements trace the motion of the absorbing material and offer insight into the kinematics and spatial distribution of the wind in the vicinity of the black hole. These findings enhance our understanding of wind-fed accretion in Cygnus X-1 and highlight the importance of continued high-resolution X-ray observations to further constrain the physical properties of winds and accretion flows in high-mass X-ray binaries.

References in corpus (17)

• X-ray Properties of Black-Hole Binaries
• Modelling the behaviour of accretion flows in X-ray binaries
• Cygnus X-1 contains a 21-solar mass black hole -- implications for massive star winds
• Polarized x-rays constrain the disk-jet geometry in the black hole x-ray binary Cygnus X-1
• Systematic comparison of photoionised plasma codes with application to spectroscopic studies of AGN in X-rays
• Superorbital variability of X-ray and radio emission of Cyg X-1 - II. Dependence of the orbital modulation and spectral hardness on the superorbital phase
• Chandra X-ray spectroscopy of the focused wind in the Cygnus X-1 system. I. The non-dip spectrum in the low/hard state
• Polarized X-rays from windy accretion in Cygnus X-1
• Long term variability of Cygnus X-1: VII. Orbital variability of the focussed wind in Cyg X-1 / HDE 226868 system
• Systematically Revisiting All NuSTAR Spins of Black Holes in X-Ray Binaries
• Chandra X-ray spectroscopy of the focused wind in the Cygnus X-1 system III. Dipping in the low/hard state
• Stellar wind in state transitions of high-mass X-ray binaries
• Long term variability of Cygnus X-1. VIII. A spectral-timing look at low energies with NICER
• Dramatic Variability of X-ray Absorption Lines in the Black Hole Candidate Cygnus X-1
• Comprehensive UV and Optical spectral analysis of Cygnus X-1: Stellar and wind parameters, abundances, and evolutionary implications
• Peering into the tilted heart of Cyg X-1 with high-precision optical polarimetry
• Formation of Wind-Fed Black Hole High-mass X-ray Binaries: The Role of Roche-lobe-Overflow Post Black-Hole Formation