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) x 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 x 1039 erg s−1, which is comparable to the Eddington luminosity of this system.
Recommended Citation
H. Suzuki and N. Tsuji and Y. Kanemaru and M. Shidatsu and L. Olivera-Nieto and S. Safi-Harb and S. S. Kimura and E. de la Fuente and S. Casanova and K. Mori and X. Wang and S. Kato and D. Tateishi and H. Uchiyama and T. Tanaka and H. Uchida and S. Inoue and D. Huang, "Detection Of Extended X-Ray Emission Around The PeVatron Microquasar V4641 Sgr With XRISM," Astrophysical Journal Letters, vol. 978, no. 2, article no. L20, American Astronomical Society; IOP Publishing, Jan 2025.
The definitive version is available at https://doi.org/10.3847/2041-8213/ad9d11
Department(s)
Physics
Publication Status
Open Access
International Standard Serial Number (ISSN)
2041-8213; 2041-8205
Document Type
Article - Journal
Document Version
Final Version
File Type
text
Language(s)
English
Rights
© 2025 The Authors, All rights reserved.
Creative Commons Licensing
This work is licensed under a Creative Commons Attribution 4.0 License.
Publication Date
10 Jan 2025
Comments
Universidad de Guadalajara, Grant 2024i-F-05