The H-alpha stellar and interstellar emission in the open cluster NGC 6910

TL;DR

This study investigates emission-line stars in NGC 6910 using H-alpha spectroscopy, confirming the nature of specific stars, correcting classifications, and analyzing spectral variability amidst nebular emission challenges.

Contribution

It provides a detailed spectral analysis of emission-line stars in NGC 6910, including classification corrections and variability observations, with careful nebular emission subtraction.

Findings

Confirmed NGC 6910 37 as a Be star.

Corrected V1973 Cyg classification to A type.

Detected H-alpha variability in HD 229196.

Abstract

We verify the nature of emission-line stars in the field of the open cluster NGC 6910. % Spectroscopy in the H-alpha region was obtained. Raw CCD frames of spectra of all stars fainter than V = 9 mag observed by us are significantly affected by nebular emission originating in the surrounding HII region IC 1318. After careful data reduction and subtraction of the nebular radiation we succeeded in obtaining reliable stellar spectra. We confirm that the star NGC 6910 37 is a Be star, and we have corrected the classification of V1973 Cyg from an Ae star to a normal A type star. Since the diffuse interstellar bands do not appear in the spectrum of this star while being present in the other stars we observed, we confirm that V1973 Cyg is a foreground object with respect to IC 1318 and NGC 6910. We also find that the H-alpha line in HD 194279 has a P Cygni profile and the H-alpha line profile is variable in HD 229196.