Hard X-Ray Emission from the Eastern Jet of SS 433 Powering the W50 “Manatee” Nebula: Evidence for Particle Reacceleration
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- University of Manitoba, Winnipeg, MB (Canada)
- Bard College, Annandale-On-Hudson, NY (United States)
- Columbia Astrophysics Laboratory, New York, NY (United States)
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Dublin Institute for Advanced Studies, Dublin (Ireland); Max-Planck-Institut for Nuclear Physics, Heidelberg (Germany)
- University of Wisconsin, Madison, WI (United States)
- Massachusetts Institute of Technology (MIT), Cambridge, MA (United States)
- University of Seoul (Korea, Republic of)
We present a broadband X-ray study of W50 (the “Manatee” nebula), the complex region powered by the microquasar SS 433, that provides a test bed for several important astrophysical processes. The W50 nebula, a Galactic PeVatron candidate, is classified as a supernova remnant but has an unusual double-lobed morphology likely associated with the jets from SS 433. Using NuSTAR, XMM-Newton, and Chandra observations of the inner eastern lobe of W50, we have detected hard nonthermal X-ray emission up to ~30 keV, originating from a few-arcminute-sized knotty region (“Head”) located ≲18' (29 pc for a distance of 5.5 kpc) east of SS 433, and constrained its photon index to 1.58 ± 0.05 (0.5–30 keV band). The index gradually steepens eastward out to the radio “ear” where thermal soft X-ray emission with a temperature kT ~ 0.2 keV dominates. The hard X-ray knots mark the location of acceleration sites within the jet and require an equipartition magnetic field of the order of ≳12 μG. The unusually hard spectral index from the “Head” region challenges classical particle acceleration processes and points to particle injection and reacceleration in the subrelativistic SS 433 jet, as seen in blazars and pulsar wind nebulae.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP); Natural Sciences and Engineering Research Council of Canada (NSERC); Canadian Space Agency; University of Manitoba; National Aeronautics and Space Administration; National Science Foundation (NSF)
- Grant/Contract Number:
- AC02-07CH11359; NNH19ZDA001N-FERMI; NNH20ZDA001N-FERMI; PHY-2110821
- OSTI ID:
- 1881947
- Report Number(s):
- FERMILAB-PUB-22-608-PPD; arXiv:2207.00573; oai:inspirehep.net:2104877; TRN: US2307890
- Journal Information:
- The Astrophysical Journal, Vol. 935, Issue 2; ISSN 0004-637X
- Publisher:
- IOP PublishingCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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