Spectral and photometric variability of SS 433 observed with XRISM and simultaneous optical and near-infrared telescopes

Abstract We present results from coordinated multiwavelength observations of the microquasar SS 433, obtained with XRISM, optical telescopes (Seimei, LCO, Tomo-e Gozen, MITSuME), and the kSIRIUS near-infrared camera during 2024 April and 2025 March. The XRISM exposures amounted to ${\sim}200$ ks in 2024 and ~100 ks in 2025, corresponding to different combinations of orbital and precessional phases. With XRISM/Resolve’s high spectral resolution and large effective area, we clearly resolved numerous emission lines even in short time segments, achieving improved accuracy in Doppler-shift measurements relative to earlier observations. The simultaneously obtained X-ray and optical Doppler shifts suggest a possible tendency for the optical emission to lag slightly behind the X-rays. In the Resolve data, the Doppler shifts of the two jet components exhibited apparent asymmetries, with jet speeds fluctuating around ${\sim}0.26 \pm 0.01c$ in 2024 and ${\sim}0.30 \pm 0.01c$ in 2025. The velocity variations indicated modulations on a timescale of ~6.3 d, with a phase offset of about $-90^{\circ }$ relative to the nutation cycle. The observed line widths and flux of the approaching and receding jets appear consistent with the expected geometrical effects, indicating systematically larger line widths in the inner regions of the jets, as proposed by Shidatsu et al. (2025, PASJ, 77, 1313). Optical light curves show flares of ~400 s in 2024 and ~1600 s in 2025, with amplitudes up to ~15% during out-of-eclipse intervals, while the XRISM/Xtend light curves show no significant variability within the overlapping intervals and given the statistical uncertainties. Near-infrared photometry in 2024, obtained during an out-of-eclipse interval at a different epoch from the optical observations, showed no flare-like variability, and the X-ray band also remained constant within uncertainties. These coordinated observations provide a foundation for future XRISM studies aimed at probing the dynamical properties of the relativistic jets in SS 433.

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Journal
Publications of the Astronomical Society of Japan
Published
2025-12-27
DOI
https://doi.org/10.1093/pasj/psaf152
Primary Topic
Astrophysical Phenomena and Observations
Type
article
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0.00

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article

Spectral and photometric variability of SS 433 observed with XRISM and simultaneous optical and near-infrared telescopes

T. Takagi, Yusuke Sakai, Yuu Niino, Masafumi Niwano et al.
Publications of the Astronomical Society of Japan
Astrophysical Phenomena and Observations
article

Spectral and photometric variability of SS 433 observed with XRISM and simultaneous optical and near-infrared telescopes

T. Takagi, Yusuke Sakai, Yuu Niino, Masafumi Niwano, Daiki Miura, Kei Fujiwara, Kenta Taguchi, Marina Yoshimoto, D. Hiramatsu, Ichiro Takahashi, Taichi Igarashi, Keisuke ISOGAI, Haruka Sakemi, Katsuhiro L. Murata, Yuki Niida, Tomoko Nakamoto, Takahiro Nagayama, Kosuke Namekata, Miyu Uenishi, Hideki Uchiyama, Tomoya Usuki, Shigeyuki Sako, Yoichi Yatsu, Megumi Shidatsu, Kyuseok Oh, Robert Petre, Hiromasa Suzuki, Mahito Sasada, Shogo B Kobayashi, Mariko Kimura, Shinya Yamada, Nobuyuki Kawai, Chulsoo Kang, Hiroya Yamaguchi, Taro Kotani, Miho Tan, Yoshihiro Ueda, Yuta Okada, Mami Machida
article en

Abstract

Abstract We present results from coordinated multiwavelength observations of the microquasar SS 433, obtained with XRISM, optical telescopes (Seimei, LCO, Tomo-e Gozen, MITSuME), and the kSIRIUS near-infrared camera during 2024 April and 2025 March. The XRISM exposures amounted to ${\sim}200$ ks in 2024 and ~100 ks in 2025, corresponding to different combinations of orbital and precessional phases. With XRISM/Resolve’s high spectral resolution and large effective area, we clearly resolved numerous emission lines even in short time segments, achieving improved accuracy in Doppler-shift measurements relative to earlier observations. The simultaneously obtained X-ray and optical Doppler shifts suggest a possible tendency for the optical emission to lag slightly behind the X-rays. In the Resolve data, the Doppler shifts of the two jet components exhibited apparent asymmetries, with jet speeds fluctuating around ${\sim}0.26 \pm 0.01c$ in 2024 and ${\sim}0.30 \pm 0.01c$ in 2025. The velocity variations indicated modulations on a timescale of ~6.3 d, with a phase offset of about $-90^{\circ }$ relative to the nutation cycle. The observed line widths and flux of the approaching and receding jets appear consistent with the expected geometrical effects, indicating systematically larger line widths in the inner regions of the jets, as proposed by Shidatsu et al. (2025, PASJ, 77, 1313). Optical light curves show flares of ~400 s in 2024 and ~1600 s in 2025, with amplitudes up to ~15% during out-of-eclipse intervals, while the XRISM/Xtend light curves show no significant variability within the overlapping intervals and given the statistical uncertainties. Near-infrared photometry in 2024, obtained during an out-of-eclipse interval at a different epoch from the optical observations, showed no flare-like variability, and the X-ray band also remained constant within uncertainties. These coordinated observations provide a foundation for future XRISM studies aimed at probing the dynamical properties of the relativistic jets in SS 433.

Publications of the Astronomical Society of Japan
Kanazawa University (JP), Kagoshima University (JP), Tokyo Institute of Technology (JP), University of Miyazaki (JP), Kanazawa Institute of Technology (JP), Shizuoka University (JP), Goddard Space Flight Center (US), Aoyama Gakuin University (JP), Rikkyo University (JP), Tokyo University of Science (JP), University of America (US), Yamaguchi University (JP), The Graduate University for Advanced Studies, SOKENDAI (JP), Kyoto University (JP), Korea Astronomy and Space Science Institute (KR), Japan Aerospace Exploration Agency (JP), University of Florida (US), Kanagawa University (JP), Heliophysics (US), Institute of Astronomy (RU), Center for Astrophysics Harvard & Smithsonian (US), Institute of Space and Astronautical Science (JP), Astronomy and Space (AU), National Astronomical Observatory of Japan (JP), The NSF AI Institute for Artificial Intelligence and Fundamental Interactions (US), Ehime University (JP), The University of Tokyo (JP), Catholic University of America (US)
National Science Foundation, National Aeronautics and Space Administration, Kagoshima University, National Research Foundation, Ministry of Education, Culture, Sports, Science and Technology, Korea Astronomy and Space Science Institute, National Research Foundation of Korea, National Astronomical Observatory of Japan, Ministry of Science and ICT, South Korea, Goddard Space Flight Center, Japan Society for the Promotion of Science, Institute for Cosmic Ray Research, University of Tokyo
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