A Multiwavelength Interpretation of HESS J1857+026 Emission Using the Fermi-LAT, VERITAS, and HAWC Observatories

Authors

• J. Eagle, NASA Goddard Space Flight Center
• S. Kumar, University of Maryland, College Park
• A. Archer, DePauw University
• P. Bangale, College of Science and Technology
• J. T. Bartkoske, The University of Utah
• W. Benbow, Center for Astrophysics∣Harvard & Smithsonian
• N. R. Bond, University College Dublin
• Y. Chen, University of California, Los Angeles
• J. L. Christiansen, California Polytechnic State University, San Luis Obispo
• A. J. Chromey, Center for Astrophysics∣Harvard & Smithsonian
• A. Duerr, The University of Utah
• M. Errando, Washington University in St. Louis
• M. Escobar Godoy, Santa Cruz Institute for Particle Physics
• J. Escudero Pedrosa, Center for Astrophysics∣Harvard & Smithsonian
• S. Feldman, University of California, Los Angeles
• Q. Feng, The University of Utah
• S. Filbert, The University of Utah
• L. Fortson, College of Science and Engineering
• A. Furniss, Santa Cruz Institute for Particle Physics
• W. Hanlon, Center for Astrophysics∣Harvard & Smithsonian
• C. E. Hinrichs, Smithsonian Institution
• J. Holder, The Bartol Research Institute
• T. B. Humensky, College of Computer, Mathematical, & Natural Sciences
• M. Iskakova, Washington University in St. Louis
• W. Jin, University of California, Los Angeles
• M. N. Johnson, Santa Cruz Institute for Particle Physics
• E. Joshi, Deutsches Elektronen-Synchrotron (DESY)
• P. Kaaret, University of Iowa
• M. Kertzman, DePauw University
• M. Kherlakian, Ruhr-Universitat Bochum
• D. Kieda, The University of Utah

Document Type

Article

Publication Date

7-10-2026

Abstract

We present a new study on the MeV–TeV γ-ray origin of HESS J1857+026 using data collected from the Fermi–LAT, VERITAS, and HAWC observatories. A spatial and spectral study of HESS J1857+026 including radiative modeling of the MeV–TeV spectrum determines the likely dominant γ-ray origin as a pulsar wind nebula (PWN) powered by the energetic pulsar PSR J1856+0245. The MeV–TeV spectrum is further characterized through basic evolutionary radiative modeling assuming a PWN origin to constrain the physical properties of the system such as the magnetic field strength and PWN age. The results of the PWN evolutionary model are consistent with the observational constraints of the system, finding an age of the system between τ = [16, 21] kyr and a magnetic field strength between B = [0.4, 1.6] μG. These estimates support an evolved PWN scenario where the observed γ-ray emission is generated by the relativistic electrons' inverse Compton (IC) scattering off local photon fields; however, the low-energy (E < 10 GeV) spectral component could be dominated by hadronic emission originating from a supernova remnant (SNR). For a PWN component above 10 GeV, we measure the conditions for particle diffusion, finding that the local diffusion (D(50 TeV) ∼ 10²⁸ cm⁻² s⁻¹) is suppressed compared to the interstellar medium (ISM) value, in agreement with similar TeV PWNe. By measuring the radial surface brightness profiles of the γ-ray source across multiple instruments, we demonstrate that the combined MeV–TeV spatial information is a powerful tool to constrain particle diffusion properties.

Publication Title

Astrophysical Journal

Recommended Citation

Eagle, J., Kumar, S., Archer, A., Bangale, P., Bartkoske, J., Benbow, W., Bond, N., Chen, Y., Christiansen, J., Chromey, A., Duerr, A., Errando, M., Escobar Godoy, M., Pedrosa, J., Feldman, S., Feng, Q., Filbert, S., Fortson, L., Furniss, A., Hanlon, W., Hinrichs, C., Holder, J., Humensky, T., Iskakova, M., Jin, W., Johnson, M., Joshi, E., Kaaret, P., Kertzman, M., Kherlakian, M., & Kieda, D. (2026). A Multiwavelength Interpretation of HESS J1857+026 Emission Using the Fermi-LAT, VERITAS, and HAWC Observatories. Astrophysical Journal, 1005(2). http://doi.org/10.3847/1538-4357/ae706f
Retrieved from: https://digitalcommons.mtu.edu/michigantech-p2/2816