Three-colour photographic photometry of the young open cluster NGC 7510 based upon UBV observations made with the 122cm and 182cm Asiago reflectors is presented here. A mean colour excess E(B-V)=1.12, a distance of 3.09kpc could be achieved for this cluster and 31 stars could be identified as photometric physical members. An age of 10^7^years has been derived by comparison with standard isochrones. The discrepancy between the photometric and spectroscopic distances obtained for some stars is discussed and comparisons with recent investigations of the same object are also given.
Photoelectric UBV observations were made in two associations in the Large Magellanic Cloud, in the magnitude range 10.6 to 16.2. The observations were made at the Cerro Tololo Inter-American Observatory with the 36-inch telescope in the nights of 1-5 December 1967. The positions were computed by B. Skiff (Lowell Obs.) in 2009.
It is generally believed that expanding superbubbles and mechanical feedback from massive stars trigger star formation, because there are numerous examples of superbubbles showing secondary star formation at their edges. However, although these systems show an age sequence, they do not provide strong evidence of a causal relationship. The W3/W4 Galactic star-forming complex suggests a three-generation hierarchy: the supergiant shell structures correspond to the oldest generation; these triggered the formation of IC 1795 in W3, the progenitor of a molecular superbubble that in turn triggered the current star-forming episodes in the embedded regions W3-North, W3-Main, and W3-OH. We present UBV photometry and spectroscopic classifications for IC 1795, which show an age of 3-5 Myr. This age is intermediate between the reported 6-20 Myr age of the supergiant shell system and the extremely young ages (10^4^-10^5^yr) for the embedded knots of the ultracompact HII regions, W3-North, W3-Main, and W3-OH. Thus, an age sequence is indeed confirmed for the entire W3/W4 hierarchical system. This therefore provides some of the first convincing evidence that superbubble action and mechanical feedback are indeed a triggering mechanism for star formation.
Two new Galactic Wolf-Rayet stars were found in open clusters: a WN4 star in the O9 cluster Sher 1 and a WN7 star in the O7 cluster Westerlund 2. This confirms a previous trend, namely that fainter, hotter WN stars tend to be older than brighter, cooler WN stars. This may be a consequence of evolution via extreme mass loss.
The results of photoelectric UBV photometry of 234 AB stars in the southern galactic halo are presented. The stars were chosen from the Curtis Schmidt objective-prism survey of Preston and Shectman and comprise a sample of halo objects selected without kinematic bias. The majority of the stars lie in the region of the (U-B, B-V) plane occupied by field and globular cluster blue horizontal-branch stars.
Magnitudes in V and B-V and U-B colors observed by the 91-cm telescope at Okayama are presented for 109 stars including both classical and marginal barium stars. The two-color diagram shows a fair amount of spread. This can be interpreted by interstellar reddening and variable amounts of line blocking effect. Both classical and marginal barium stars form a fairly homogeneous group.
A summary of results of the systematic UBV photoelectric monitoring of bright northern Be stars carried out at the Hvar Observatory between 1972 and 1990 is presented. Altogether, 76 Be stars of all luminosity classes were observed and 13848 UBV measurements secured. Simultaneously, 9648 UBV measurements of 48 check stars (most of them of early spectral types) were obtained. A careful transformation of all observations into the standard Johnson system allowed detection and monitoring of even very mild long-term light and colour variations of these objects. Almost all early-type Be stars in the sample turned out to be variable. For several stars phase-locked light variations related to their binary nature were established. Sudden brightenings, on a time scale of a few days, were detected for o Cas and QR Vul.
The data presented in this catalogue are the results of multicolor photometric observations of stars listed in the Bright Star Catalog. Observations were made on the 21-in, 28-in and 60-in telescopes of the Lunar and Planetary Laboratory, and at Tonanzintla Observatory on the 40-in telescope of the Observatorio Astronomico Nacional, Universidad Nacional de Mexico. This catalog of UBV photometry on almost 5000 bright stars covers the entire sky by including southern Cape photometry transformed to the UBV system.
We present UBV photometric observations of 55 wide visual double stars with K- and M- type primaries. Our observations have been compared and combined with information available in the literature. At least 58% of them are optical pairs.
UBV measurements of early-type stars, mostly eclipsing binaries, obtained at La Silla in the years 1990 to 1994 with the ESO 50cm telescope are presented. Most of these data were already used in our individual studies of several binaries. Now all photometric measurements were reduced again with an advanced technique and are made available electronically. Our data for MY Ser have not yet been published; new light curve is given and solved. The result is that MY Ser is a contact binary, with very large fill-out parameter. Also a light curve and its solution for V1051 Cen are provided, and the problem of the period of V871 Cen is pointed out. Besides binaries (and the comparison and check stars) data for several stars in southern H II regions are included. Extinction and transformation coefficients are given.
