Spectral energy distribution of Mrk 501. The BeppoSAX data from 1997 April 7 and 16 are indicated as labeled. The nearly simultaneous Whipple TeV data (from Catanese et al. 1997) are indicated as filled circles, while the open circle (1997 April 13) and the TeV spectral fit (1997 March 15–20), along with its 1 σ confidence range, are from the HEGRA experiment (Aharonian et al. 1997a). Nonsimultaneous measurements collected from the literature are shown as open squares (radio: Gear et al. 1994; millimeter: Steppe et al. 1988, Wiren et al. 1992, Lawrence et al. 1991, and Bloom & Marscher 1991; far‐infrared: Impey & Neugebauer 1988; optical: Véron‐Cetty & Véron 1993 and Burbidge & Hewitt 1987; UV: Pian & Treves 1993; TeV: Quinn et al. 1996, Breslin et al. 1997, and Bradbury et al. 1997). X‐ray spectral fits range in the low state are from Sambruna et al. 1994, Worrall & Wilkes 1990, and Comastri et al. 1997. Upper limits at 100 MeV are from Weekes et al. 1996 and Catanese et al. 1997. The solid lines indicate fits with a one‐zone, homogeneous synchrotron self‐Compton model. For all models, the size of the emitting region is ﹩R=5\times 10^{15}﹩ cm, the beaming factor is δ = 15, and the magnetic field is ﹩B\sim 0.8﹩ G. For the "quiescent state," the intrinsic luminosity (corrected for beaming) is ﹩L^{\prime }=4.6\times 10^{40}﹩ ergs s﹩^{-1}﹩, and electrons are continuously injected with a power‐law distribution (∝γ⁻²) between ﹩\gamma _{\mathrm{min}\,}=3\times 10^{3}﹩ and ﹩\gamma _{\mathrm{max}\,}=6\times 10^{5}﹩. For the fit to the April 7 spectrum, ﹩L^{\prime }=1.8\times 10^{41}﹩ ergs s﹩^{-1}﹩, and the injected electron distribution (∝γ^−1.5) extends from ﹩\gamma ^{4}_{\mathrm{min}\,}=1\times 10^{4}﹩ to ﹩\gamma _{\mathrm{max}\,}=3\times 10^{6}﹩. For the fit to the April 16 spectrum, ﹩L^{\prime }=5.5\times 10^{41}﹩ ergs s﹩^{-1}﹩, and the injected electron distribution (∝γ⁻¹) extends from ﹩\gamma _{\mathrm{min}\,}=4\times 10^{5}﹩ to ﹩\gamma _{\mathrm{max}\,}=3\times 10^{6}﹩. For the April 7 and 16 models, the seed photons for the Compton scattering are the sum of those produced by the assumed electron distribution plus those corresponding to the quiescent spectrum.