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arXiv · 2606.16520

XP-TEAL: Gaia XP tool for emission and absorption lines. I. Balmer lines in open clusters

J. M. Carrasco·M. Weiler·S. Malhotra·F. Anders·C. Jordi·E. Masana·J. Castañeda·F. Boix
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Abstract

Context. The third Gaia data release (Gaia DR3) includes blue and red low-resolution spectrophotometry for more than 200 million sources. These Gaia XP spectra are represented by sets of coefficients multiplying linear combinations of basis functions related to Hermite functions. In a previous work we introduced a method that maximally exploits the information encoded in the Gaia spectrophotometric coefficients in order to identify absorption and emission lines. Aims. Our aim is to detect hydrogen Balmer emission and absorption lines in stars belonging to open clusters included in the released Gaia DR3 blue and red spectrophotometry, and to characterise the Balmer line strengths as a function of colour. Methods. We refined our XP tool for emission and absorption lines (XP-TEAL), using derivatives of the internal spectral coefficients to analyse hydrogen Balmer lines in the Gaia DR3 XP spectra. We tested our results using stars in open clusters, considering both absorption and emission features. Results. The analysis of the hydrogen lines in the spectra of open cluster stars allows us to assess the performance and limitations of the method. We find an empirical dependence of the absorption-line equivalent widths on the intrinsic colour of the stars, which allows us to derive precise colour excesses caused by interstellar extinction. We also identify 1256 stars with emission lines, 356 of which have not previously been reported in the literature. Conclusions. We successfully tested our XP-TEAL code on stars in clusters and have made both the source code and the online version available to the community. Despite the low resolution of Gaia spectrophotometry, our code is able to extract useful line information.

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J. M. Carrasco, M. Weiler, S. Malhotra, F. Anders, C. Jordi, E. Masana, J. Castañeda, F. Boix. 2026-06-15. XP-TEAL: Gaia XP tool for emission and absorption lines. I. Balmer lines in open clusters. https://doi.org/10.1051/0004-6361%2F202659924

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