SED snapshots (solid lines) showing the evolution from a pre-flare steady state (dotted black line) to a new steady state that corresponds to the peak of a hard X-ray flare when protons are injected with ${\gamma }_{\text{p},\text{max}}^{\prime }$ = 10^3.5 (dashed blue line). For comparison, the pure SSC flare spectrum is overplotted (dotted orange line). The time interval between successive snapshots is $0.1t_{\text{cr}}^{\prime }$ and the total duration in the observer’s frame is $10t_{\text{cr}}^{\prime }\approx 4.6$ h. The left and right panels show the results for ℓ_e = 10⁻⁴, ℓ_p = 1 and ℓ_e = 10⁻⁶, ℓ_p = 10⁻¹, respectively. Other parameters used are B′ = 0.86 G, R′ = 10¹⁵ cm, s_e = s_p = 1.7, ${\gamma }_{\text{e},\text{max}}^{\prime }$ = 10⁵ (pre-flare) and 10^6.5 (flare), ${\gamma }_{\text{p},\max }^{\prime }\sim (m_{\text{e}}/m_{\text{p}}){\gamma }_{\text{e},\max }^{\prime }$, and δ = 20. The attenuation of VHE γ-rays due to the extragalactic background light is not included here.