Massive Stars in the SDSS-IV-APOGEE Survey: Wolf–Rayet Stars of the WN Type

Abstract

In this paper, we describe the results obtained in our study of Galactic Wolf–Rayet stars of the WN type, using the APOGEE2 spectrographs. The APOGEE2 WN star near-infrared spectra presented here were selected through a careful examination of the APOGEE2 DR16 sample, being compound of at least one exemplar of each Wolf–Rayet star from WN4 to WN11 types. Besides the APOGEE2 WN sample, we also identified three new Galactic exemplars of the WN type. The first is WR 147–1, a narrow-lined Wolf–Rayet star of the WN4-5 type located in the direction of the Cygnus-X North complex. The two remaining objects, WR 48–11 and WR 48–12, are found at projected angular distances of several arcminutes southwest from the Danks 1 cluster. WR 48–12 has an estimated heliocentric distance of kpc, which is not compatible (within the quoted uncertainties) with that of about 3.8 ± 0.6 kpc for the G305 complex. On the other hand, WR 48–11 has a probable heliocentric distance of kpc, which is about three times that of the former, implying that it is probably placed well behind the G305 complex, perhaps at the outermost portion of the Perseus arm.