Abstract
Broad-band near-infrared photometry in the JHK (and sometimes L' and M) bands of 82 stars in h and x Persei is presented. The stars observed cover the upper main sequence of the central parts of the clusters as well as the giants and supergiants of the extended region. New UBV photoelectric photometry of 24 stars for which only photographic photometry was previously available is also reported. The infrared results are consistent with a unique value of the extinction in the direction of both clusters of AV= 1.85 ± 0.12. Comparisons between the infrared and visual data suggest that the observed dispersion towards large values of E(B- is not due to variable reddening as previously stated in the literature but that it may be intrinsic to the atmosphere of some B-type stars. Infrared excesses were found in the brightest B and A-type supergiants. These are explained by bremsstrahlung associated with their hot stellar winds. Most of the Be stars in x Persei also present significant infrared excesses due to circumstellar dust emission or bremsstrahlung or both.
