Detection of Extended X-Ray Emission around the PeVatron Microquasar V4641 Sgr with XRISM

Suzuki, Hiromasa; Tsuji, Naomi; Kanemaru, Yoshiaki; Shidatsu, Megumi; Olivera-Nieto, Laura; Safi-Harb, Samar; Kimura, Shigeo S.; de la Fuente, Eduardo; Casanova, Sabrina; Mori, Kaya; Wang, Xiaojie; Kato, Sei; Tateishi, Dai; Uchiyama, Hideki; Tanaka, Takaaki; Uchida, Hiroyuki; Inoue, Shun; Huang, Dezhi; Lemoine-Goumard, Marianne; Miura, Daiki; Ogawa, Shoji; Kobayashi, Shogo B.; Done, Chris; Parra, Maxime; Díaz Trigo, Maria; Muñoz-Darias, Teo; Padilla, Montserrat Armas; Tomaru, Ryota; Ueda, Yoshihiro

Abstract

A recent report on the detection of very-high-energy gamma rays from V4641 Sagittarii (V4641 Sgr) up to ≈0.8 PeV has made it the second confirmed “PeVatron” microquasar. Here we report on the observation of V4641 Sgr with X-Ray Imaging and Spectroscopy Mission (XRISM) in 2024 September. Thanks to the large field of view and low background, the CCD imager Xtend successfully detected for the first time X-ray extended emission around V4641 Sgr with a significance of ≳4.5σ and >10σ based on our imaging and spectral analysis, respectively. The spatial extent is estimated to have a radius of 7′ ± 3′ (13 ± 5 pc at a distance of 6.2 kpc) assuming a Gaussian-like radial distribution, which suggests that the particle acceleration site is within ~10 pc of the microquasar. If the X-ray morphology traces the diffusion of accelerated electrons, this spatial extent can be explained by either an enhanced magnetic field (∼80 μG) or a suppressed diffusion coefficient (∼1027 cm2 s−1 at 100 TeV). The integrated X-ray flux, (4–6) × 10−12 erg s−1 cm−2 (2–10 keV), would require a magnetic field strength higher than the Galactic mean (≳8 μG) if the diffuse X-ray emission originates from synchrotron radiation and the gamma-ray emission is predominantly hadronic. If the X-rays are of thermal origin, the measured extension, temperature, and plasma density can be explained by a jet with a luminosity of ∼2 × 1039 erg s−1, which is comparable to the Eddington luminosity of this system.

Citation

Suzuki, H., Tsuji, N., Kanemaru, Y., Shidatsu, M., Olivera-Nieto, L., Safi-Harb, S., Kimura, S. S., de la Fuente, E., Casanova, S., Mori, K., Wang, X., Kato, S., Tateishi, D., Uchiyama, H., Tanaka, T., Uchida, H., Inoue, S., Huang, D., Lemoine-Goumard, M., Miura, D., …Ueda, Y. (2025). Detection of Extended X-Ray Emission around the PeVatron Microquasar V4641 Sgr with XRISM. Astrophysical Journal Letters, 978(2), Article L20. https://doi.org/10.3847/2041-8213/ad9d11

• Journal Article Type: Article
• Acceptance Date: Dec 10, 2024
• Online Publication Date: Jan 3, 2025
• Publication Date: Jan 10, 2025
• Deposit Date: Jan 17, 2025
• Publicly Available Date: Jan 17, 2025
• Journal: The Astrophysical Journal Letters
• Print ISSN: 2041-8205
• Electronic ISSN: 2041-8213
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 978
• Issue: 2
• Article Number: L20
• DOI: https://doi.org/10.3847/2041-8213/ad9d11
• Keywords: Non-thermal radiation sources, Gamma-ray sources, Low-mass x-ray binary stars, Radio jets
• Public URL: https://durham-repository.worktribe.com/output/3332489