Ultraviolet and optical observations of HDE 245770/ A 0535+26 system during an X-ray flare

We present high and low dispersion UV spectra of HDE 245770, which is the optical counterpart of the recurrent transient X-ray pulsar A 0535+26,during a decay of an X-ray flare. UBV photometric measurements and medium dispersion optical spectra were simultaneously obtained.The energy distribution of the star in the 12 – 10 micron range is compared with the models of Kurucz and Poeckert and Marlborough.In this phase, HDE 245770 does not show evaluable variations with respect to the quiescent X-ray phase.