The IACOB project XII. A new grid of northern standards for the spectral classification of B-type stars

TL;DR

This paper introduces a comprehensive new spectral classification grid for B-type stars, enhancing the accuracy and consistency of stellar parameter estimation using modern spectra, and supporting future research including Gaia/RVS data.

Contribution

It develops a detailed, high-quality classification grid for B-type stars based on modern spectra, improving upon previous standards and enabling better physical parameter correlation.

Findings

New classification grid is more comprehensive and self-consistent.

Demonstrates improved correlation with physical stellar parameters.

Provides a tool for studying B-type stars across wide parameter ranges.

Abstract

With the advent of large spectroscopic surveys, automated stellar parameter determination has become commonplace. Nevertheless, spectral classification still offers a quick and useful alternative for obtaining parameter estimates for large samples of spectra of varying quality. We present a new atlas of stellar spectra covering the B-type range, with the intention of providing detailed classification criteria valid for modern spectra and improving the grid of reliable standards. This new grid will be used in future works to provide classification criteria beyond the classical classification range and addressing, in particular, the use of Gaia/RVS spectra. We analysed historical standards by means of multiple high-resolution spectra, marking out problematic cases and complementing the grid with a new set of reliable comparators. We then elaborated on a new set of classification criteria based on high-quality R=4000 spectra. Our new classification grid is much thicker than any previous set of standards, presenting a high degree of self-consistency. Although it is based entirely on morphological criteria, the grid demonstrates a much better correlation with different physical parameters. The new grid can be used to study classification criteria in other spectral ranges, providing a valuable tool for the study of B-type stars that covers a very wide range of temperatures, luminosities, and stellar masses. The very process of classification also offers valuable insights into stellar evolution.