Outflowing photoionized plasma in Circinus X-1 using the high-resolution X-ray spectrometer Resolve onboard XRISM and the radiative transfer code cloudy

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Main Authors: Tsujimoto, Masahiro, Enoto, Teruaki, Trigo, María Díaz, Hell, Natalie, Chakraborty, Priyanka, Leutenegger, Maurice A., Loewenstein, Michael, Pradhan, Pragati, Shidatsu, Megumi, Takahashi, Hiromitsu, Yaqoob, Tahir
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Published: 2025
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author Tsujimoto, Masahiro
Enoto, Teruaki
Trigo, María Díaz
Hell, Natalie
Chakraborty, Priyanka
Leutenegger, Maurice A.
Loewenstein, Michael
Pradhan, Pragati
Shidatsu, Megumi
Takahashi, Hiromitsu
Yaqoob, Tahir
author_facet Tsujimoto, Masahiro
Enoto, Teruaki
Trigo, María Díaz
Hell, Natalie
Chakraborty, Priyanka
Leutenegger, Maurice A.
Loewenstein, Michael
Pradhan, Pragati
Shidatsu, Megumi
Takahashi, Hiromitsu
Yaqoob, Tahir
contents High-resolution X-ray spectroscopy is a key to understanding the mass inflow and outflow of compact objects. Spectral lines carry information about the ionization, density, and velocity structures through their intensity ratios and profiles. They are formed in non-local thermodynamic equilibrium conditions under the intense radiation field from the compact objects, thus radiative transfer (RT) calculation is a requisite for proper interpretations. We present such a study for a low-mass X-ray binary, Circinus X-1, from which the P Cygni profile was discovered using the X-ray grating spectrometer onboard Chandra. We observed the source using the X-ray microcalorimeter onboard XRISM at an orbital phase of 0.93-0.97 and revealed many spectral features unidentified before; the higher series transitions (n to 1; n > 2) of highly-ionized (H- and He-like) S, Ca, Ar, and Fe in emission and absorption, the Fe Kα and K\b{eta} inner-shell excitation absorption of mildly-ionized (O- to Li-like) Fe, and resolved fine-structure level transitions in the Fe Lyα and Heα complexes. They blend with each other at different velocity shifts on top of apparently variable continuum emission that changed its flux by an order of magnitude within a 70 ks telescope time. Despite such complexity in the observed spectra, most of them can be explained by a simple model consisting of the photoionized plasma outflowing at ~300 km s-1 and the variable blocking material in the line of sight of the incident continuum emission from the accretion disk. We demonstrate this with the aid of the RT code cloudy for the line ratio diagnostics and spectral fitting. We further constrain the physical parameters of the outflow and argue that the outflow is launched close to the outer edge of the accretion disk and can be driven radiatively by being assisted by the line force calculated using the RT simulation.
format Preprint
id arxiv_https___arxiv_org_abs_2503_08254
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Outflowing photoionized plasma in Circinus X-1 using the high-resolution X-ray spectrometer Resolve onboard XRISM and the radiative transfer code cloudy
Tsujimoto, Masahiro
Enoto, Teruaki
Trigo, María Díaz
Hell, Natalie
Chakraborty, Priyanka
Leutenegger, Maurice A.
Loewenstein, Michael
Pradhan, Pragati
Shidatsu, Megumi
Takahashi, Hiromitsu
Yaqoob, Tahir
High Energy Astrophysical Phenomena
High-resolution X-ray spectroscopy is a key to understanding the mass inflow and outflow of compact objects. Spectral lines carry information about the ionization, density, and velocity structures through their intensity ratios and profiles. They are formed in non-local thermodynamic equilibrium conditions under the intense radiation field from the compact objects, thus radiative transfer (RT) calculation is a requisite for proper interpretations. We present such a study for a low-mass X-ray binary, Circinus X-1, from which the P Cygni profile was discovered using the X-ray grating spectrometer onboard Chandra. We observed the source using the X-ray microcalorimeter onboard XRISM at an orbital phase of 0.93-0.97 and revealed many spectral features unidentified before; the higher series transitions (n to 1; n > 2) of highly-ionized (H- and He-like) S, Ca, Ar, and Fe in emission and absorption, the Fe Kα and K\b{eta} inner-shell excitation absorption of mildly-ionized (O- to Li-like) Fe, and resolved fine-structure level transitions in the Fe Lyα and Heα complexes. They blend with each other at different velocity shifts on top of apparently variable continuum emission that changed its flux by an order of magnitude within a 70 ks telescope time. Despite such complexity in the observed spectra, most of them can be explained by a simple model consisting of the photoionized plasma outflowing at ~300 km s-1 and the variable blocking material in the line of sight of the incident continuum emission from the accretion disk. We demonstrate this with the aid of the RT code cloudy for the line ratio diagnostics and spectral fitting. We further constrain the physical parameters of the outflow and argue that the outflow is launched close to the outer edge of the accretion disk and can be driven radiatively by being assisted by the line force calculated using the RT simulation.
title Outflowing photoionized plasma in Circinus X-1 using the high-resolution X-ray spectrometer Resolve onboard XRISM and the radiative transfer code cloudy
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2503.08254