Long-term X-ray light curve of OV Boo in the 0.2−10 keV energy range. The Chandra and XMM-Newton observations correspond to the first and last points, respectively. The Swift observations of the DN outburst are shown in the inset. Error bars are at 1σ significance. The luminosity has been calculated using the 210 pc distance; the relative uncertainty is about 7%. The vertical line in the inset indicates the time of the first outburst optical observation.