XP-TEAL: Gaia XP Tool for Emission and Absorption Lines II. Gaia-HELIX catalogue of Hα emitters in Gaia BP/RP spectra
Abstract
Context: With Gaia's third Data Release (DR3), low-resolution BP/RP (XP) spectra became available for more than 219 million sources. In previous work, we developed a fast method for detecting absorption and emission lines while measuring their equivalent widths directly from the XP spectral coefficients. Aims: We conduct a systematic search for Hα emitters in the Gaia DR3 XP spectra. Methods: We measured the equivalent width of the Balmer Hα line for all sources with Gaia XP spectra and selected an initial sample of 556100 sources depicting an Hα emission-like feature at 2σ level or above. Using a semi-supervised classifier complemented by manual spectral labelling, we removed sources that merely masqueraded as emission-line stars. Results: We find that 95% of the initial candidates are most likely cool M-type stars, where a molecular absorption band gives rise to a local maximum that can mimic Hα emission. Subsequently, 28394 sources were flagged as bona fide Hα emitters using the Gaia DR3 XP spectra. The majority are Be-like candidates (26287), M-type emission-line stars (717), Herbig Ae/Be candidates (525), quasi-stellar objects (204), Wolf-Rayet stars (177), cataclysmic variables (51), and carbon stars (18), among other sources. Our equivalent widths and stellar classifications agree well with results from higher-resolution studies and recent Gaia XP spectra-based catalogues. Ground-based spectroscopic follow-up for some of the newly found Hα emitters reinforces our confidence in the catalogue.
Versions
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BibTeX
@misc{malhotra2026xpteal,
title = {{XP-TEAL: Gaia XP Tool for Emission and Absorption Lines II. Gaia-HELIX catalogue of H$α$ emitters in Gaia BP/RP spectra}},
author = {S. Malhotra and M. Weiler and F. Anders and J. M. Carrasco and G. Garcia-Moreno and C. Jordi and N. Blagorodnova and A. Castro-Ginard and J. Castañeda and F. Boix and X. Luri},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2606.21420},
eprint = {2606.21420},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.21420},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - XP-TEAL: Gaia XP Tool for Emission and Absorption Lines II. Gaia-HELIX catalogue of Hα emitters in Gaia BP/RP spectra
AU - S. Malhotra
AU - M. Weiler
AU - F. Anders
AU - J. M. Carrasco
AU - G. Garcia-Moreno
AU - C. Jordi
AU - N. Blagorodnova
AU - A. Castro-Ginard
AU - J. Castañeda
AU - F. Boix
AU - X. Luri
PY - 2026
DA - 2026/08/17
PB - arXiv
DO - 10.48550/arxiv.2606.21420
UR - https://arxiv.org/abs/2606.21420
AB - Context: With Gaia's third Data Release (DR3), low-resolution BP/RP (XP) spectra became available for more than 219 million sources. In previous work, we developed a fast method for detecting absorption and emission lines while measuring their equivalent widths directly from the XP spectral coefficients. Aims: We conduct a systematic search for Hα emitters in the Gaia DR3 XP spectra. Methods: We measured the equivalent width of the Balmer Hα line for all sources with Gaia XP spectra and selected an initial sample of 556100 sources depicting an Hα emission-like feature at 2σ level or above. Using a semi-supervised classifier complemented by manual spectral labelling, we removed sources that merely masqueraded as emission-line stars. Results: We find that 95% of the initial candidates are most likely cool M-type stars, where a molecular absorption band gives rise to a local maximum that can mimic Hα emission. Subsequently, 28394 sources were flagged as bona fide Hα emitters using the Gaia DR3 XP spectra. The majority are Be-like candidates (26287), M-type emission-line stars (717), Herbig Ae/Be candidates (525), quasi-stellar objects (204), Wolf-Rayet stars (177), cataclysmic variables (51), and carbon stars (18), among other sources. Our equivalent widths and stellar classifications agree well with results from higher-resolution studies and recent Gaia XP spectra-based catalogues. Ground-based spectroscopic follow-up for some of the newly found Hα emitters reinforces our confidence in the catalogue.
ER -