We observed the middle-aged radio pulsar B0656+14 with a CCD detector at the 6-m telescope .
Broadband BVRI images show the following magnitudes of the pulsar counterpart : B = 24.85 ( +0.19 , -0.16 ) , V = 24.90 ( +0.16 , -0.14 ) , R = 24.52 ( +0.12 , -0.11 ) , I = 23.81 ( + % 0.27 , -0.21 ) .
We fitted the UV-optical ( space + ground-based ) data with a two-component model which combines a power law ( non-thermal component ) with a thermal spectrum emitted by the neutron star surface .
The power law component , with the energy power-law index \alpha = 1.5 ( +1.1 , -1.2 ) , dominates in the observed range .
Constraints on the thermal component correspond to the Rayleigh-Jeans parameter G \equiv T _ { 6 } ( R _ { 10 } / d _ { 500 } ) ^ { 2 } = 4.1 ( +2.1 , -4.1 ) , where T = 10 ^ { 6 } T _ { 6 } K is the brightness temperature , R _ { \infty } = 10 R _ { 10 } km is the neutron star radius as seen by a distant observer , and d = 500 d _ { 500 } pc is the distance .
The shape of the optical-UV spectrum of PSR B0656+14 differs considerably from those observed from other pulsars : the middle-aged Geminga and young Crab , Vela .