Spectral Classification of B Stars: The Empirical Sequence Using SDSS-IV/APOGEE Near-IR Data
Abstract
We present a semi-empirical spectral classification scheme for normal B-type stars using near-infrared (NIR) spectra (1.5-1.7 μm) from the Sloan Digital Sky Survey Apache Point Observatory Galaxy Evolution Experiment (APOGEE2)-N data release 14 (DR14) database. The main motivation for working with B-type stars is their importance in the evolution of young stellar clusters; however, we also take advantage of having a numerous sample (316 stars) of B-type star candidates in APOGEE2-N, for which we also have optical (3600-9100 Å) counterparts from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey. By first obtaining an accurate spectral classification of the sources using the LAMOST DR3 spectra and the canonical spectral classification scheme, we found a linear relation between optical spectral types and the equivalent widths of the hydrogen lines of the Brackett series in the APOGEE2-N NIR spectra. This relation extends smoothly from a similar relation for O and early B stars found by Roman-Lopes et al. This way, we obtain a catalog of B-type sources with features in both the optical and NIR and a classification scheme refined down to one spectral subclass.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 2020
- DOI:
- 10.3847/1538-4357/ab8127
- arXiv:
- arXiv:2003.09469
- Bibcode:
- 2020ApJ...894....5R
- Keywords:
-
- B stars;
- Spectroscopy;
- Infrared astronomy;
- Optical identification;
- 128;
- 1558;
- 786;
- 1167;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 11 pages, 7 figures and 1 table