The stellar content of the compact H II region Sh2-88B

International audienceWe present a photometric study of the compact H II region Sh2-88B and its associated stellar cluster. The positions and JHK magnitudes are obtained for 125 stars over an 80``\texttimes80'' field centered on the region. The region has two components, called Sh2-88B1 and Sh2-88B2. B1 is a compact cometary H II region associated with a cluster containing several massive stars. The dominant exciting star, at the center of the cometary structure, has an ionizing radiation flux corresponding to a spectral type in the range O8.5V-O9.5V. It is highly reddened, with a visual extinction in the 30-42 mag range, and exhibits a near-IR excess. B1 has a simple morphology, with the ionized and neutral gas clearly separated. Its unidentified infrared band (UIB) emission, observed by ISOCAM in the 5-8.5 \ensuremathμm passband, comes from the photodissociation region at the periphery of the ionized gas. B2 is an ultracompact H II region whose exciting star, probably of spectral type later than B0.5V, is not detected; this indicates a visual extinction greater than 60 mag. A very steep and regular increase of the extinction from west to east is observed over the whole of Sh2-88B. Based on observations done at the Canada-France-Hawaii Telescope and at the Observatoire de Haute Provence. The CFHT is operated by the Centre National de la Recherche Scientifique of France, the National Research Council of Canada, and the University of Hawaii. Table 1 is available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html Fig. 3 is only available electronically with the On-Line publication at http://link.springer.de/link/service/00230