XRISM spectroscopy on orbital modulation of Fe Lyα lines in Cygnus X-3

Abstract To understand physical processes such as mass transfer and binary evolution in X-ray binaries, the orbital parameters of the system are fundamental and crucial information. Cygnus X-3 is a high-mass X-ray binary composed of a compact object of unknown nature and a Wolf–Rayet star, which is of great interest in the context of wind-fed mass accretion and binary evolution. Here we present XRISM/Resolve high-resolution spectroscopy, focusing on the Fe Ly$\alpha$ lines when the source was in its hypersoft state. We perform an orbital phase-resolved spectral analysis of the lines to study the orbital modulation of the emission and absorption lines. It is found that the emission lines reflect the orbital motion of the compact object whose estimated velocity amplitude is $430^{+150}_{-140}$ km s$^{-1}$, while the absorption lines show a variation that can be interpreted as originating from the stellar wind. We discuss possible mass ranges for the binary components using the mass function with the estimated value of the velocity amplitude in this work, combined with the relation between the mass-loss rate and the orbital period derivative and the empirical mass and mass-loss rate relation for Galactic Wolf–Rayet stars. They are constrained to be (1.3–5.1) and (9.3–12) M$_\odot$, respectively, for the assumed inclination angle of $i =25^\circ$, and become more relaxed, (1.3–24) and (9.3–16) M$_\odot$, for $i = 35^\circ$. Thus, it remains unclear whether the system harbors a black hole or a neutron star.

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Journal
Publications of the Astronomical Society of Japan
Published
2025-06-16
DOI
https://doi.org/10.1093/pasj/psaf057
Primary Topic
Astrophysical Phenomena and Observations
Type
article
Field-Weighted Citation Impact
0.00

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article

XRISM spectroscopy on orbital modulation of Fe Lyα lines in Cygnus X-3

Tomohiro Hakamata, Michael L. McCollough, Kazutoshi Okabe, Hirokazu Odaka et al.
Publications of the Astronomical Society of Japan
Astrophysical Phenomena and Observations
article

XRISM spectroscopy on orbital modulation of Fe Lyα lines in Cygnus X-3

Tomohiro Hakamata, Michael L. McCollough, Kazutoshi Okabe, Hirokazu Odaka, J. M. Mïller, T. R. Kallman, Daiki Miura, K. I. I. Koljonen, Hiroya Yamaguchi, Ryota Tomaru, K. Yamaoka, Teruaki Enoto, Natalie Hell, Tasuku Hayashi, Ralf Ballhausen, Shunji Kitamoto, S. Yamada, Shin Watanabe, Hiroshi Nakajima, Itsuki Maruzuka
article en

Abstract

Abstract To understand physical processes such as mass transfer and binary evolution in X-ray binaries, the orbital parameters of the system are fundamental and crucial information. Cygnus X-3 is a high-mass X-ray binary composed of a compact object of unknown nature and a Wolf–Rayet star, which is of great interest in the context of wind-fed mass accretion and binary evolution. Here we present XRISM/Resolve high-resolution spectroscopy, focusing on the Fe Ly$\alpha$ lines when the source was in its hypersoft state. We perform an orbital phase-resolved spectral analysis of the lines to study the orbital modulation of the emission and absorption lines. It is found that the emission lines reflect the orbital motion of the compact object whose estimated velocity amplitude is $430^{+150}_{-140}$ km s$^{-1}$, while the absorption lines show a variation that can be interpreted as originating from the stellar wind. We discuss possible mass ranges for the binary components using the mass function with the estimated value of the velocity amplitude in this work, combined with the relation between the mass-loss rate and the orbital period derivative and the empirical mass and mass-loss rate relation for Galactic Wolf–Rayet stars. They are constrained to be (1.3–5.1) and (9.3–12) M$_\odot$, respectively, for the assumed inclination angle of $i =25^\circ$, and become more relaxed, (1.3–24) and (9.3–16) M$_\odot$, for $i = 35^\circ$. Thus, it remains unclear whether the system harbors a black hole or a neutron star.

Publications of the Astronomical Society of JapanVol. 77(Supplement_1)
Lawrence Livermore National Laboratory (US), Goddard Space Flight Center (US), Aoyama Gakuin University (JP), Rikkyo University (JP), Kanto Gakuin University (JP), Norwegian University of Science and Technology (NO), Kyoto University (JP), University of Michigan (US), Japan Aerospace Exploration Agency (JP), Center for Astrophysics Harvard & Smithsonian (US), Astrophysics Science Division (US), Institute of Space and Astronautical Science (JP), Nagoya University (JP), University of Maryland, College Park (US), The University of Tokyo (JP), The University of Osaka (JP)
U.S. Department of Energy, National Aeronautics and Space Administration, Japan Science and Technology Corporation, European Research Council, Japan Society for the Promotion of Science
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