1994A&AS..104..557T

Homogeneous uvbyβ photometry of 150 stars associated with the star forming regions Taurus-Auriga, Orion, Canis Mayoris, Ophiuchus, Serpens and Cygnus, is presented here. We also present uvbyβ photometry of 10 Herbig Ae/Be stars not belonging to the specific regions studied here. Using the (V,b-y), (β,[m1]), ([c1],[m1]) and ([u-b], T_eff) diagrams we study the photometric properties of the sample. The effects of duplicity, stellar rotation, and interstellar extinction on the location in the magnitude-color and color-color diagrams of our program stars are briefly investigated. We derive reliable photometric spectral types and discuss membership to the regions and to the Orion population, as well as peculiarities of the individual stars. We also find new B stars associated with the CMa R1 star forming region and new intermediate-low mass PMS members associated with the BD+404124/BD+413731 region. The FU-Orionis stars Z CMa, V1515 Cyg and V1057 Cyg have a peculiar position in the reddening free (β,[m1]) diagram. With diagrams such as (V-M _v-5 log r+5) vs. E(b-y), E(c1) vs. E(b-y), E(m1) vs. E(b-y) and E(u-b) vs. E(b-y) we investigate the IS extinction law towards the star-forming regions. We find that the total to selective extinction ratio to these regions is steeper than normal with R_y=5.4 (R_v=4.0) and the coefficients E(c1)/E(b-y) and E(m1)/E(b-y) used to define the reddening free indices [c1] and [m1] should be numerically smaller than the generally adopted values.