2015/11/01 by Mark J. Pecaut
Physics and Astronomy · #Astronomy and Astrophysical Research #Diagram #Electrical and Electromagnetic Research #Extinction (optical mineralogy) #Hertzsprung–Russell diagram #Main sequence #Sequence (biology) #Spectral analysis #Stars #Stellar classification #Stellar, planetary, and galactic studies #astro-ph.SR
paper · pdf · doi:10.1017/s1743921315006079
published as IAUS, 314, 85-90 (2016) · 6 pages, 4 figures; Proceedings IAU Symposium No. 314, 2015, Young Stars & Planets Near the Sun
openalex publication_date 2015/11/01 · arxiv created 2016/07/12 · arxiv updated 2016/07/14 · openalex created_date 2016/07/22 · openalex updated_date 2026/08/05
Abstract We highlight differences in spectral types and intrinsic colors observed in pre-main sequence (pre-MS) stars. Spectral types of pre-MS stars are wavelength-dependent, with near-infrared spectra being 3-5 spectral sub-classes later than the spectral types determined from optical spectra. In addition, the intrinsic colors of young stars differ from that of main-sequence stars at a given spectral type. We caution observers to adopt optical spectral types over near-infrared types, since Hertzsprung-Russell (H-R) diagram positions derived from optical spectral types provide consistency between dynamical masses and theoretical evolutionary tracks. We also urge observers to deredden pre-MS stars with tabulations of intrinsic colors specifically constructed for young stars, since their unreddened colors differ from that of main sequence dwarfs. Otherwise, V -band extinctions as much as ~0.6 mag erroneously higher than the true extinction may result, which would introduce systematic errors in the H-R diagram positions and thus bias the inferred ages.