Near-Infrared Spectroscopy of Deeply Embedded, Young Massive Stars

Abstract

Using the highest spectral resolution (R ~ 10,000) currently available in the near-infrared on the Very Large Telescope, we have obtained K-band spectra of young massive stars deeply embedded in (ultra-) compact H II regions. Our sample consists of “normal” OB-type stars that seem to have settled on the main sequence, as well as massive stars that show no photospheric spectrum, but exhibit the spectral signatures of a dense circumstellar disk. In this paper we focus on the properties of the O5–O6 main-sequence star ionizing the cometary shaped UCHII region G29.96-0.02; on the identification of the long-sought-for ionizing star of the Flame Nebula (NGC 2024); and on the peculiar nature of the massive Young Stellar Object NGC 2024-IRS2.