APA
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Ninoyu, K., Yamada, S., Hell, N., Costantini, E., Adegoke, O., Draghis, P., … Ito, S. (2026). XRISM high-resolution X-ray spectroscopy of Cygnus X-1: Orbital and short-term variability of iron absorption. Nippon Tenmon Gakkai Obun Kenkyu Hokoku.
Chicago/Turabian
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Ninoyu, Kaito, Shinya Yamada, N. Hell, E. Costantini, O. Adegoke, P. Draghis, K. Ebisawa, et al. “XRISM High-Resolution X-Ray Spectroscopy of Cygnus X-1: Orbital and Short-Term Variability of Iron Absorption.” Nippon Tenmon Gakkai obun kenkyu hokoku (2026).
MLA
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Ninoyu, Kaito, et al. “XRISM High-Resolution X-Ray Spectroscopy of Cygnus X-1: Orbital and Short-Term Variability of Iron Absorption.” Nippon Tenmon Gakkai Obun Kenkyu Hokoku, 2026.
BibTeX Click to copy
@article{kaito2026a,
title = {XRISM high-resolution X-ray spectroscopy of Cygnus X-1: Orbital and short-term variability of iron absorption},
year = {2026},
journal = {Nippon Tenmon Gakkai obun kenkyu hokoku},
author = {Ninoyu, Kaito and Yamada, Shinya and Hell, N. and Costantini, E. and Adegoke, O. and Draghis, P. and Ebisawa, K. and García, Javier A. and Hodges-Kluck, E. and Kitamoto, S. and Kobayashi, S. and Kohmura, T. and Kubota, A. and Miller, Jon M. and Mizumoto, M. and Mizuno, T. and Takahashi, H. and Uchida, Y. and Yamaoka, K. and Zhang, Sixuan and Tomaru, R. and Ito, S.}
}
We present the first high-resolution spectroscopy of the black hole high-mass X-ray binary Cygnus X-1 with XRISM, including orbital-phase-resolved analyses and tentative evidence of short-term variability in the Fe K band on second timescales. Using data from the Performance Verification phase in 2024 April, we analyzed spectral variability across orbital phases with the Resolve microcalorimeter and the Xtend CCD imager. The unprecedented resolution of Resolve reveals variability in highly ionized Fe absorption lines. The absorption features show orbital-phase-dependent variability in column density, ionization state, and blueshifted velocity, suggesting structural variations in the focused stellar wind along the line of sight. We also find indications of subtle broadening of the neutral Fe emission profile. In addition, intensity-sorted spectroscopy during dip phases suggests possible variability on timescales of a few seconds in the absorption features, consistent with cooler, denser, and lower-ionized gas clumps. Although the statistical significance is limited, these results hint that the stellar wind and the X-rays from the accretion disk around the black hole may interact on timescales as short as a few seconds. These XRISM results constrain wind-fed accretion in Cyg X-1 and highlight Resolve’s capability to probe plasma environments in high-mass X-ray binaries.