Document Type
Article
Publication Date
6-15-2023
Department
Department of Physics
Abstract
3-ray observations of the Cygnus Cocoon, an extended source surrounding the Cygnus X star-forming region, suggest the presence of a cosmic-ray accelerator reaching energies up to a few PeV. The very-high-energy (VHE, 0.1-100 TeV) 3-ray emission may be explained by the interaction of cosmic-ray hadrons with matter inside the Cocoon, but an origin of inverse Compton radiation by relativistic electrons cannot be ruled out. Inverse Compton 3-rays at VHE are accompanied by synchrotron radiation peaked in X-rays. Hence, X-ray observations may probe the electron population and magnetic field of the source. We observed 11 fields in or near the Cygnus Cocoon with the Neil Gehrels Swift Observatory's X-Ray Telescope (Swift-XRT) totaling 110 ks. We fit the fields to a Galactic and extragalactic background model and performed a log-likelihood ratio test for an additional diffuse component. We found no significant additional emission and established upper limits in each field. By assuming that the X-ray intensity traces the TeV intensity and follows a dN/dE E-2.5 spectrum, we obtained a 90 % upper limit of F X < 8.7 × 10-11 erg cm-2 s-1 or < 5.2 × 10-11 erg cm-2 s-1 on the X-ray flux of the entire Cygnus Cocoon between 2 and 10 keV depending on the choice of hydrogen column density model for the absorption. The obtained upper limits suggest that no more than one-quarter of the 3-ray flux at 1 TeV is produced by inverse Compton scattering, when assuming an equipartition magnetic field of 1/420 μG.
Publication Title
Astrophysical Journal
Recommended Citation
Guevel, D.,
Beardmore, A.,
Page, K.,
Lien, A.,
Fang, K.,
Tibaldo, L.,
Casanova, S.,
&
Huentemeyer, P.
(2023).
Limits on Leptonic TeV Emission from the Cygnus Cocoon with Swift-XRT.
Astrophysical Journal,
950(2).
http://doi.org/10.3847/1538-4357/accdde
Retrieved from: https://digitalcommons.mtu.edu/michigantech-p/17392
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Version
Publisher's PDF
Publisher's Statement
© 2023. The Author(s). Published by the American Astronomical Society. Publisher’s version of record: https://doi.org/10.3847/1538-4357/accdde