  We report on the analysis of B band imaging data of 57 low-redshift QSOs and
Seyfert 1 galaxies selected from the Hamburg/ESO-Survey, for which host galaxy
dependent selection biases are greatly reduced compared to other optical
surveys. Only one object in the sample is known to be radio-loud.
  We adopted a procedure to remove the AGN contribution by subtracting a scaled
point spread functions from each QSO image. To reclaim the integrated host
galaxy flux we correct for oversubtraction based on simulations. This method
shows to be quite insensitive to the host galaxy morphological type, which we
can unambiguously established for 15 of the 57 objects.
  The quasar host galaxies are detected in all cases. The hosts are very
luminous, ranging in absolute magnitude M_B from -19.0 to -23.8, with an
average of M_B,gal = -21.5, considerably above L* for field galaxies. For the
luminous QSO subsample with M_B < -23 the average host absolute magnitude is
M_B,gal = -23.0, while for the complementary low-luminosity AGN we get M_B,gal
= -21.2, roughly equal to L*.
  The luminous host galaxies in the sample are typically approx. 1 mag brighter
than expected when inferring B band luminosities from studies of similar
objects at longer wavebands. We argue that this mismatch is not likely to be
explained by selection effects, but favor host galaxy colours significanlty
bluer than those of inactive galaxies. Although published B band data are
scant, this result and the findings of other authors are in good agreement.
