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Published March 2021 | public
Journal Article

Data-driven Spectroscopic Estimates of Absolute Magnitude, Distance, and Binarity: Method and Catalog of 16,002 O- and B-type Stars from LAMOST

Abstract

We present a data-driven method to estimate absolute magnitudes for O- and B-type stars from the LAMOST spectra, which we combine with Gaia DR2 parallaxes to infer distance and binarity. The method applies a neural network model trained on stars with precise Gaia parallax to the spectra and predicts Kₛ-band absolute magnitudes Mₖₛ with a precision of 0.25 mag, which corresponds to a precision of 12% in spectroscopic distance. For distant stars (e.g., >5 kpc), the inclusion of constraints from spectroscopic Mₖₛ significantly improves the distance estimates compared to inferences from Gaia parallax alone. Our method accommodates for emission-line stars by first identifying them via principal component analysis reconstructions and then treating them separately for the Mₖₛ estimation. We also take into account unresolved binary/multiple stars, which we identify through deviations in the spectroscopic Mₖₛ from the geometric Mₖₛ inferred from Gaia parallax. This method of binary identification is particularly efficient for unresolved binaries with near equal-mass components and thus provides a useful supplementary way to identify unresolved binary or multiple-star systems. We present a catalog of spectroscopic Mₖₛ, extinction, distance, flags for emission lines, and binary classification for 16,002 OB stars from LAMOST DR5. As an illustration, we investigate the Mₖₛ of the enigmatic LB-1 system, which Liu et al. had argued consists of a B star and a massive stellar-mass black hole. Our results suggest that LB-1 is a binary system that contains two luminous stars with comparable brightness, and the result is further supported by parallax from the Gaia eDR3.

Additional Information

© 2021. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. H.-W.R. acknowledges funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project-ID 138713538—SFB 881 ("The Milky Way System", subproject A03). M.X. is grateful for Dr. Bodem for the successful dental surgery and the attentive care from him during recovery. Y.S.T. is grateful to be supported by the NASA Hubble Fellowship grant HST-HF2-51425.001 awarded by the Space Telescope Science Institute. This work has made use of data acquired through the Guoshoujing Telescope. Guoshoujing Telescope (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope; LAMOST) is a National Major Scientific Project built by the Chinese Academy of Sciences. Funding for the project has been provided by the National Development and Reform Commission. LAMOST is operated and managed by the National Astronomical Observatories, Chinese Academy of Sciences. This work has also made use of data from the European Space Agency (ESA) mission Gaia, processed by the Gaia Data Processing and Analysis Consortium (DPAC). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

Additional details

Created:
August 22, 2023
Modified:
October 24, 2023