J/A+A/711/A215 XP-TEAL. Balmer lines in open clusters (Carrasco+, 2026)
XP-TEAL: Gaia XP Tool for emission and absorption lines.
I. Balmer lines in open clusters.
Carrasco J.M., Weiler M., Malhotra S., Anders F., Jordi C., Masana E.,
Castaneda J., Boix F.
<Astron. Astrophys. 711, A215 (2026)>
=2026A&A...711A.215C 2026A&A...711A.215C (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, open ; Photometry ; Optical ; Spectroscopy
Keywords: line: profiles - methods: data analysis - techniques: spectroscopic -
catalogs - stars: emission-line, Be -
open clusters and associations: general
Abstract:
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.
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 characterise the Balmer line
strengths as a function of colour.
We refine our XP Tool for Emission and Absorption Lines (XP-TEAL)
based on the analysis of the derivatives of the spectral coefficients
to analyse hydrogen Balmer lines in the Gaia DR3 XP spectra using the
derivatives of the internal Gaia DR3 XP spectra. We test our results
using stars in open clusters, considering both absorption and emission
features.
The analysis of the hydrogen lines in 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 that allows us to derive precise
colour excesses caused by interstellar extinction. We also identified
1256 stars with emission lines (356 of them unknown in the
literature).
We successfully tested our XP-TEAL code on stars belonging to clusters
and make both the source code and the online version available to the
community. Despite the low resolution of Gaia spectrophotometry, our
code has proven to be able to extract useful line information from it.
Description:
In table1.dat, colour excess and interstellar absorptions are
presented for clusters included Hunt & Reffert, 2023A&A...673A.114H 2023A&A...673A.114H,
Cat. J/A+A/673/114.
table2.dat includes the analysis of the Balmer lines of members in
clusters extracted from table1.
table3.dat includes the mastercurves used to estimate the BP-RP colour
excesses included in table1 for a given cluster.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tableb1.dat 224 7135 Color excess and interstellar absorptions
derived for clusters in Hunt & Reffert,
2023A&A...673A.114H 2023A&A...673A.114H, Cat. J/A+A/673/114
tableb2.dat 332 608159 Balmer lines widths for members of the clusters
in Hunt & Reffert, 2023A&A...673A.114H 2023A&A...673A.114H,
Cat. J/A+A/673/114
tableb3.dat 89 1972 Mastercurves used to determine the color excess
in BP-RP
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See also:
J/A+A/673/A114 : Improving the open cluster census. II. (Hunt+, 2023)
J/A+A/686/A42 : Improving the open cluster census. III. (Hunt+, 2024)
Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 20 A20 --- Cluster Name of the cluster
22- 42 F21.17 deg RAdeg Right ascension (J2000) of the cluster
44- 66 F23.19 deg DEdeg Declination (J2000) of the cluster
68- 89 E22.14 mag E(BP-RP) Colour excess in BP-RP of the cluster based
on the mastercurves in TableB3
91-113 E23.15 mag AG Absorption of the cluster in Gaia G band
predicted from EBPRP
115-137 E23.15 mag AV Absorption of the cluster in Johnson V
band predicted from EBPRP
139-162 E24.16 mag E(H-K) Excess in H-K 2MASS colour
164-187 E24.16 mag E(J-H) Excess in J-H 2MASS colour
189-212 E24.16 mag E(BP-K) Excess in BP-K Gaia-2MASS colour
218 I1 --- GoodEx [0/1] Flag indicating if determination of
E(BP-RP) is considered of good quality
224 I1 --- OC [0/1] Flag indicating if the cluster is
considered as open cluster
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Byte-by-byte Description of file: tableb2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaDR3 Gaia DR3 source identifier
21- 42 F22.18 deg RAdeg Right ascension (ICRS) at Ep=2016.0 of the
star
44- 64 E21.18 deg DEdeg Declination (ICRS) at Ep=2016.0 of the star
66- 75 F10.7 mag Gmag Gaia DR3 magnitude in G
77- 90 E14.11 mag BP-RP Gaia DR3 GBP-GRP colour
92-111 A20 --- Cluster Name of the cluster
113-125 E13.6 nm EWHa Equivalent width of the hydrogen alpha Balmer
line
127-142 F16.6 nm e_EWHa Standard error of EWHa
144-151 F8.6 --- HaP ?=- P-value significance of the local extremum
of the hydrogen alpha Balmer line
153-160 F8.6 nm HaD ?=- Line width of the hydrogen alpha Balmer
line relative to the LSF width
162 A1 --- HaOrder Detection order of the hydrogen alpha Balmer
line (1)
164-180 A17 --- HaRelEm Relative emission of the hydrogen alpha Balmer
line
182-195 E14.6 nm EWHb Equivalent width of the hydrogen beta Balmer
line
197-213 F17.6 nm e_EWHb Standard error of EWHb
215-222 F8.6 --- HbP ?=- P-value significance of the local extremum
of the Hbeta line
224-231 F8.6 --- HbD ?=- Line width of the hydrogen beta Balmer
line relative to the LSF width
233 A1 --- HbOrder Detection order of the hydrogen beta Balmer
(1)
235-254 A20 --- HbRelEm Relative emission of the hydrogen beta Balmer
line
256-268 E13.6 nm EWHg Equivalent width of the hydrogen gamma Balmer
line
270-286 F17.6 nm e_EWHg Standard error of EWHg
288-295 F8.6 --- HgP ?=- P-value significance of the local extremum
of the hydrogen gamma Balmer line
297-304 F8.6 --- HgD ?=- Line width of the hydrogen gamma Balmer
line relative to the LSF width
306 A1 --- HgOrder Detection order of the hydrogen gamma Balmer
line (1)
308-328 A21 --- HgRelEm Relative emission of the hydrogen gamma Balmer
line
330 A1 --- OC [F/T] Flag indicating if the cluster is
considered open cluster
332 A1 --- EmLit [F/T] Flag indicating if the cluster is
considered an emitter by the literature
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Note (1): Detection order as follows:
0 = extrema found in the spectrum
2 = extrema found in the second derivative
3 = no significant extremum is detected and only an upper limit is provided
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Byte-by-byte Description of file: tableb3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 20 F20.17 mag BP-RP Gaia DR3 GBP-GRP colour
22- 43 E22.14 nm EWHa Equivalent width of the Hidrogen alpha Balmer line
45- 66 E22.14 nm EWHb Equivalent width of the Hidrogen beta Balmer line
68- 89 E22.14 nm EWHg Equivalent width of the Hidrogen gamma Balmer line
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Acknowledgements:
From J. M. Carrasco, carrasco(at)fqa.ub.edu
This work was (partially) supported by the Spanish
MICIN/AEI/10.13039/501100011033 and by 'ERDF A way of making Europe'
by the 'European Union' through grant PID2021-122842OB-C21 and
PID2024-157964OB-C21, and the Institute of Cosmos Sciences University
of Barcelona (ICCUB, Unidad de Excelencia 'Maria de Maeztu') through
grant CEX2024-001451-M and the project 2021-SGR-00679 GRC de l'Agencia
de Gestio d'Ajuts Universitaris i de Recerca (Generalitat de
Catalunya).
This work was partially supported by the OCRE awarded project Galactic
Research in Cloud Services (Galactic RainCloudS). OCRE receives
funding from the European Union Horizon 2020 research and innovation
programme under grant agreement no. 824079.
This work has 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.
This research has made use of the SIMBAD database, operated at CDS,
Strasbourg, France. This research has made use of the TOPCAT and
STILTS tools (Taylor 2005).
We also thank R. Sordo for her insightful comments on the manuscript,
which helped improve the paper.
License: CC-BY-4.0
(End) Patricia Vannier [CDS] 28-May-2026