Photometry of bright stars in the Small Magellanic Cloud.
A photoelectric photometry iii the UBV system down to a limiting visual magnitude of about 14rn.5 is presented for 118 stars in three fields of the Small Magellanic Cloud. Two of the fields are located in the Bar, the third one in the Wing of the SMC. Because of the small interstellar absorption in the SMC, it is rossible to distinguish early-type bright giant and supergiant stars which are probable SMC members, from a large fraction of the main sequence (foreground) stars by plotting the (U-B) vs (B- V) two-colour diagram. About one star out of three selected at random in the three fields in the visual magnitude range lom to 14m5 probably is a physical member of the SMC, 50% turn out to be probable foreground stars, while for the remaining objects no certain decision upon SMC membership is possible by means of UBV photometry. Among the 49 stars found to be certain or probable SMC members according to the results of the present photometry, 35 were previously known or suspected members, including 16 H emission-line stars selected for the photometry from the catalogue of Henlze (1956). Probable spectral types and luminosity classes have been derived from the two-colour diagram for all SMC and foreground stars, assuming the distance modulus of the SMC to be 19rn.2. Colour excesses could be obtained for 39 SMC members and 32 foreground stars, by comparing the observed colours to intrinsic colours of similar unreddened galactic stars. No difference is found between the mean reddening of the SMC members in the Bar and in the Wing of the SMC. The mean colour excess E(B is 0' 12 + O' k)4 for SMC emission-line stars, as compared to O' O6 + OrnOS for non-emission SMC bright giant and supergiant stars, and O'?O7 + OWOS (r.m.s. error) for foreground stars. This leads to the conclusion that the mean dust content of the H I component in the SMC is much smaller than in the Galaxy. Key words: Magellanic Clouds - stellar photometry - supergiants - interstellar reddening
Astronomy and Astrophysics
- Pub Date:
- November 1970