Identification and spectroscopic characterization of 128 new Herbig stars

TL;DR

This study spectroscopically confirms 128 new Herbig stars, expanding the known sample by 50%, and analyzes their accretion properties, revealing a mass-dependent break in accretion behavior and evidence of inner-disk photoevaporation.

Contribution

It provides the largest spectroscopic confirmation and characterization of Herbig stars, refining their accretion properties and supporting the existing catalog of candidates.

Findings

128 new Herbig stars confirmed, increasing known objects by 50%.

Identified a break in accretion properties at ~3.87 M_sun.

Evidence of intense inner-disk photoevaporation in stars above 7 M_sun.

Abstract

We present optical spectroscopy observations of 145 high-mass pre-main sequence candidates from the catalogue of Vioque et al. (2020). From these, we provide evidence for the Herbig nature of 128 sources. This increases the number of known objects of the class by $\sim50\%$. We determine the stellar parameters of these sources using the spectra and Gaia EDR3 data. The new sources are well distributed in mass and age, with 23 sources between $4$-$8$ M$_{\odot}$ and 32 sources above $8$ M$_{\odot}$. Accretion rates are inferred from H$\alpha$ and H$\beta$ luminosities for 104 of the new Herbigs. These accretion rates, combined with previous similar estimates, allow us to analyze the accretion properties of Herbig stars using the largest sample ever considered. We provide further support to the existence of a break in accretion properties at $\sim3$-$4$ M$_{\odot}$, which was already reported for the previously known Herbig stars. We re-estimate the potential break in accretion properties to be at $3.87^{+0.38}_{-0.96}$ M$_{\odot}$. As observed for the previously known Herbig stars, the sample of new Herbig stars independently suggests intense inner-disk photoevaporation for sources with masses above $\sim7$ M$_{\odot}$. These observations provide robust observational support to the accuracy of the Vioque et al. (2020) catalogue of Herbig candidates.