O-like Stars in the Direction of the North America and Pelican Nebulae

Abstract

In the area covering the complex of the North America and Pelican nebulae we identified 13 faint stars with J-H and H-Ks color indices which simulate heavily reddened O-type stars. One of these stars is CP05-4 classified as O5 V by Comeron and Pasquali (2005). Combining magnitudes of these stars in the passbands I, J, H, Ks and [8.3] we were able to suspect that two of them are carbon stars and five are late M-type AGB stars. Interstellar extinction in the direction of these stars was estimated from the background red clump giants in the J-H vs. H-Ks diagram and from star counts in the Ks passband. Four or five stars are found to have a considerable probability of being O-type stars, contributing to the ionization of North America and Pelican. If they really are O-type stars, their interstellar extinction A(V) should be from 16 to 35 mag. Two of them seem to be responsible for bright E and J radio rims discovered by Matthews and Goss (1980).

17 pages, 6 figures