The asteroids 36 Atalante and 48 DORIS - Rotation, UBV-photometry, and lightcurves

The asteroids 36 Atalante and 48 Doris were observed during their opposition in 1978, using the ESO-0.5 m telescope at the European Southern Observatory, Chile. Both asteroids were investigated in the same season by Harris and Young (1980).

For 36 Atalante a period of rotation was derived with P = 9^h.93±0^h.01 (0^d.4137±0^d.0005) The maximum amplitude of the double mode lightcurve was found to be 0^m.15. Frequent color measurements in UBV did not show any variation during the rotation, exceeding the scatter; mean colors are B-V 0.70±0.01 and U-B = 0.37±0.01.

48 Doris shows a rotation rate of P =11^h.900±0^h.005 (0^d.4958±0^h.0002) Considering observations by Harris and Young (1980) we state a double mode lightcurve, too, with a maximum amplitude of at least 0^m.30. The lightcurve is not completely covered by observation. For 48 Doris a color variation on its surface is indicated in B-V, the side causing the secondary extrema being at about 0^m.02 redder than that causing the primary ones; mean colors are B-V=0.71±0.01 and U-B=0.45±0.02.

Absolute magnitudes were computed for both asteroids using the mean phase coefficient φ = 0.039 mag/deg and considering that 48 Doris was observed at small phase angles.