@article {22744,
	title = {A Relativistic Bremsstrahlung/Inverse Compton Origin for 2EG J1857+0118 Associated with Supernova Remnant W44},
	volume = {482},
	year = {1997},
	month = {1997/06/1},
	pages = {874 - 880},
	abstract = {We show that relativistic bremsstrahlung and inverse Compton scattering of radio-emitting electrons can easily account for the observed γ-ray spectrum of 2EG J1857+0118 if the field strength in the shell is below ~30 μG. This source is located at the eastern border of the composite SNR W44, where the expanding radio shell is interacting with a dense molecular cloud. The nondetection of this remnant above 250 GeV implies a cutoff or steepening in the electron spectrum above ~100 GeV. The E<SUP>-1.66</SUP> spectrum of this radio/γ-ray-emitting electron component is too flat to have its origin in standard first-order Fermi acceleration, but electron injection into the shell by the pulsar PSR B1853+01 over the 2 {\texttimes} 10<SUP>4</SUP> yr lifetime may explain why the Crab-like radio spectrum (S<SUB>ν</SUB> ~ ν<SUP>-0.33</SUP>) is about the hardest of all shell-type remnants. The injected energy would be sufficient to account for the required energy of 6 {\texttimes} 10<SUP>49</SUP> ergs if the initial spin-down power of PSR B1853+01 was about 10 times larger than the present spin-down power of the Crab pulsar. A steeper Fermi electron component may be present, but the observational data are not constraining enough to provide a meaningful limit on the presence of an additional ~E<SUP>-2</SUP> shell-type electron component. The predicted γ-ray contribution from high-energy proton-gas interactions is about 20\% of the observed EGRET flux above 100 MeV, which confirms our conclusion that the γ-ray emission from W44 is dominated by a leptonic component.},
	keywords = {acceleration of particles, gamma rays: theory, ISM: Individual: Alphanumeric: W44, ISM: supernova remnants, Radiation Mechanisms: Nonthermal, Stars: Pulsars: Individual: Alphanumeric: PSR B1853+01},
	isbn = {0004-637X},
	url = {https://ui.adsabs.harvard.edu/abs/1997ApJ...482..874D},
	author = {de Jager, O. C. and Mastichiadis, A.}
}
