A photometric study of the bright cloud B in Sagittarius. VII. 1165 new variable stars and 65 diffuse objects.

As part of our on-going photometric study of the bright cloud B in Sagittarius, we investigated a new field (5.5^deg^ x 5.5^deg^, named B) situated in the direction of the galactic center: 1165 new variable stars were found on the basis of the inspection of B, V and R Schmidt plates acquired at the Mount Palomar Observatory and at the European Southern Observatory (ESO). The detection of the objects and the visual estimation of their magnitudes in the A filter have been made at the Observatoire de Lyon while the astrometry has been performed at ESO/ Garching. A catalogue is presented in Table 2 which, for each star, gives the position (equatorial and galactic coordinates), the R magnitudes at the observed extrema, the corresponding epochs as well as the amplitude of variation, and some remarks. A result of the present work is a considerable increase of the surface density per square degree of variable stars in this direction of the central part of the galactic bulge from 1.7 (in the General Catalogue of Variable Stars, GCVS) to 65. The amount of variables in the present B field is in fact similar to the one reported for the adjacent field A, which contrasts with the poorness of such stars in field D. The histogram of the amplitudes derived in the present work supports our hypothesis that the variable stars of type L and/or M are most probably more numerous in the direction of the galactic center than in other regions of the Galaxy. As an additional result of our investigation, new diffuse objects have been detected in the same field. We present in Table 5 a catalogue of 65 objects with a tentative classification (galaxy or nucleus of galaxy, nebulosity or diffuse object, and, even, probable galactic globular cluster) based only on their morphology as seen on the Schmidt plates. Sixteen other diffuse objects that look like planetary nebulae are excluded from the list: their study will be the subject of a subsequent paper.