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

TL;DR

This study identifies candidate O-type stars in the North America and Pelican nebulae region using infrared color indices, estimating their extinction and potential role in ionization, with some stars possibly responsible for observed radio features.

Contribution

It presents a method to identify heavily reddened O-type star candidates using multi-band photometry and star counts in a complex nebular region, expanding knowledge of ionizing sources.

Findings

Four or five stars have a high probability of being O-type stars.

Estimated interstellar extinction A(V) ranges from 16 to 35 mag.

Two stars may be responsible for specific radio rims.

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).