We describe observations of a white-light flare (SOL2011-02-24T07:35:00, M3.5) close to the limb of the Sun, from which we obtain estimates of the heights of the optical continuum sources and those of the associated hard X-ray sources.For this purpose we use hard X-ray images from the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI), and optical images at 6173 AA from the Solar Dynamics Observatory (SDO). We find that the centroids of the impulsive-phase emissions in white light and hard X-rays (30-80 keV) match closely in central distance (angular displacement from Sun center), within uncertainties of order 0.2. This directly implies a common source height for these radiations, strengthening the connection between visible flare continuum formation and the accelerated electrons. We also estimate the absolute heights of these emissions, as vertical distances from Sun center. Such a direct estimation has not been done previously, to our knowledge. Using a simultaneous 195 AA image from the Solar-Terrestrial RElations Observatory (STEREO-B) spacecraft to identify the heliographic coordinates of the flare footpoints, we determine mean heights above the photosphere (as normally defined; tau = 1 at 5000 AA) of 305 pm 170 km and 195 pm 70 km, respectively, for the centroids of the hard X-ray (HXR) and white light (WL) footpoint sources of the flare. These heights are unexpectedly low in the atmosphere, and are consistent with the expected locations of tau = 1 for the 6173 AA and the ~40 keV photons observed, respectively.
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