Document Type
Article
Publication Date
1-10-2025
Department
Department of Physics
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.
Publication Title
Astrophysical Journal Letters
Recommended Citation
Suzuki, H.,
Tsuji, N.,
Kanemaru, Y.,
Shidatsu, M.,
Olivera-Nieto, L.,
Safi-Harb, S.,
Kimura, 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.,
Ogawa, S.,
Kobayashi, S.,
Done, C.,
Parra, M.,
Díaz Trigo, M.,
Muñoz-Darias, T.,
Padilla, M.,
Tomaru, R.,
&
Ueda, Y.
(2025).
Detection of Extended X-Ray Emission around the PeVatron Microquasar V4641 Sgr with XRISM.
Astrophysical Journal Letters,
978(2).
http://doi.org/10.3847/2041-8213/ad9d11
Retrieved from: https://digitalcommons.mtu.edu/michigantech-p2/1380
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Version
Publisher's PDF
Publisher's Statement
© 2025. The Author(s). Published by the American Astronomical Society. Publisher’s version of record: https://doi.org/10.3847/2041-8213/ad9d11