J/A+A/706/A225 23 Classical Cepheids abundances (Catanzaro+, 2026)
Cepheid Metallicity in the Leavitt Law (C-MetaLL) survey:
VII. High-Resolution IGRINS Spectroscopy of 23 Classical Cepheids:
Validating NIR Abundances.
Catanzaro G., Bhardwaj A., Ripepi V., Trentin E., Marconi M., Romaniello M.,
Matsunaga N., De Somma G., Sicignano T., Musella I., Luongo E., Testa V.,
Soung-Chul Y.
<Astron. Astrophys. 706, A225 (2026)>
=2026A&A...706A.225C 2026A&A...706A.225C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Abundances
Keywords: stars: abundances - stars: distances - stars: fundamental parameters -
stars: variables: Cepheids - infrared: stars
Abstract:
Classical Cepheids are fundamental primary distance indicators and
crucial tracers of the young stellar population in the Milky Way and
nearby galaxies. While most chemical abundance studies of Cepheids
have been carried out in the optical domain, near-infrared (NIR)
spectroscopy offers unique advantages in terms of reduced extinction
and access to new elemental tracers.
Our goal is to validate NIR abundance determinations against
well-established optical results and to explore the diagnostic power
of previously unexplored NIR lines. NIR spectroscopy is far less
hampered by interstellar extinction than optical observations, which
allows us to probe Cepheids at larger distances and in highly obscured
regions of the Galaxy. Moreover, the H and K bands provide access to
diagnostic lines of elements (e.g., P, K, and Yb) that are not
available in the optical domain.
We acquired high-resolution (R∼45000) spectra of 21 Galactic and 2
Large Magellanic Cloud (LMC) classical Cepheids with the
high-resolution Immersion Grating Infrared Spectrometer (IGRINS) in
the H and K bands. Effective temperatures were derived from a
photometric approach and line-depth ratios, and the gravities and
microturbulent velocities were estimated using empirical calibrations
and statistical constraints. The abundances of 16 elements were
determined through a full spectral synthesis in local thermodynamic
equilibrium. We performed an extensive error analysis and compared our
results with previous optical studies of the same stars.
Our NIR abundances and the optical literature values agree very well
({DELTA}[Fe/H]≤0.02 dex and σ≃0.07dex), which confirms the
reliability of IGRINS-based measurements. The derived abundance
gradients in the Galactic disk are fully consistent with previous
optical determinations, with slopes of -0.06, -0.05, and -0.05dex/kpc
for Fe, Mg, and Si, respectively. We provide homogeneous
determinations of P, K, and Yb abundances from NIR lines for classical
Cepheids for the first time, and we report trends that are consistent
with Galactic chemical evolution models. Moreover, the two LMC
Cepheids included in our sample that were previously analyzed in the
optical provide a direct benchmark that confirms the accuracy of NIR
abundance determinations in extragalactic metal-poor environments.
Our study demonstrates that high-resolution NIR spectroscopy of
Cepheids yields robust abundances that are fully compatible with
optical results and provides access to additional elements of
nucleosynthetic interest. These results pave the way for future
large-scale NIR surveys of Cepheids with facilities such as MOONS,
ELT, and JWST, which are crucial for tracing the chemical evolution of
the Milky Way and nearby galaxies in heavily obscured regions.
Description:
Table 3 lists the spectral lines adopted in the abundance analysis,
with their atomic parameters. Table 4 provides LTE abundance ratios
[X/H] for 16 elements, together with 1-sigma uncertainties, for the 23
Classical Cepheids analysed in this work (21 Galactic and 2 LMC
Cepheids).
Abundances are expressed as [X/H], using the solar reference scale
adopted in the paper. In Table 3, wavelengths are air wavelengths
(Angstrom), level energies are in eV, and the last three columns give
log10 radiative, Stark, and van der Waals broadening parameters as
provided by the adopted atomic database.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 70 283 Spectral line list and atomic parameters
table4.dat 226 23 *LTE abundances [X/H] and uncertainties
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Note on table4.dat: LTE abundances for 16 chemical elements derived from the
IGRINS spectra for the 23 classical Cepheids. Abundances are given as [X/H]
relative to the solar values grevesse2011, along with associated uncertainties.
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See also:
J/MNRAS/508/4047 : 47 classical Cepheids HARPSN@TNG spectroscopy
(Ripepi+, 2021)
J/ApJ/913/38 : Compilation of Cepheids in the MW and MCs (Breuval+, 2021)
J/A+A/681/A65 : Cepheids PL relation metallicity dependence (Trentin+, 2024)
J/A+A/683/A234 : Cepheid Metallicity in the Leavitt Law Survey
(Bhardwaj+, 2024)
J/A+A/690/A246 : Cepheid radial abundance gradients (Trentin+, 2024)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Species Chemical species
7- 15 F9.3 0.1nm lambda Air wavelength
16 A1 --- n_lambda [*] * indicates blended lines
20- 25 F6.3 --- loggf log10(gf)
28- 32 F5.2 eV Ei Lower excitation energy
35- 37 F3.1 --- Ji Lower level total angular momentum J
40- 45 F6.2 eV Ef Upper excitation energy
48- 50 F3.1 --- Jf Upper level total angular momentum J
53- 56 F4.2 --- logGR ?=0 log10(gamma_rad), radiative damping
constant
59- 63 F5.2 --- logGS ?=0 log10(gamma_Stark), Stark damping constant
66- 70 F5.2 --- logGW ?=0 log10(gamma_vdW), Van der Waals damping
constant
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 21 A21 --- ID Star identifier
22- 26 F5.2 --- [C/H] Abundance [C/H]
28- 31 F4.2 --- e_[C/H] 1-sigma uncertainty on [C/H]
35- 39 F5.2 --- [N/H] Abundance [N/H]
41- 44 F4.2 --- e_[N/H] 1-sigma uncertainty on [N/H]
48- 52 F5.2 --- [Na/H] Abundance [Na/H]
54- 57 F4.2 --- e_[Na/H] 1-sigma uncertainty on [Na/H]
61- 65 F5.2 --- [Mg/H] Abundance [Mg/H]
67- 70 F4.2 --- e_[Mg/H] 1-sigma uncertainty on [Mg/H]
74- 78 F5.2 --- [Al/H] Abundance [Al/H]
80- 83 F4.2 --- e_[Al/H] 1-sigma uncertainty on [Al/H]
87- 91 F5.2 --- [Si/H] Abundance [Si/H]
93- 96 F4.2 --- e_[Si/H] 1-sigma uncertainty on [Si/H]
100-104 F5.2 --- [P/H] Abundance [P/H]
106-109 F4.2 --- e_[P/H] 1-sigma uncertainty on [P/H]
113-117 F5.2 --- [S/H] Abundance [S/H]
119-122 F4.2 --- e_[S/H] 1-sigma uncertainty on [S/H]
126-130 F5.2 --- [K/H] Abundance [K/H]
132-135 F4.2 --- e_[K/H] 1-sigma uncertainty on [K/H]
139-143 F5.2 --- [Ca/H] Abundance [Ca/H]
145-148 F4.2 --- e_[Ca/H] 1-sigma uncertainty on [Ca/H]
152-156 F5.2 --- [Ti/H] Abundance [Ti/H]
158-161 F4.2 --- e_[Ti/H] 1-sigma uncertainty on [Ti/H]
165-169 F5.2 --- [Mn/H] Abundance [Mn/H]
171-174 F4.2 --- e_[Mn/H] 1-sigma uncertainty on [Mn/H]
178-182 F5.2 --- [Fe/H] Abundance [Fe/H]
184-187 F4.2 --- e_[Fe/H] 1-sigma uncertainty on [Fe/H]
191-195 F5.2 --- [Ni/H] Abundance [Ni/H]
197-200 F4.2 --- e_[Ni/H] 1-sigma uncertainty on [Ni/H]
204-208 F5.2 --- [Ce/H] Abundance [Ce/H]
210-213 F4.2 --- e_[Ce/H] 1-sigma uncertainty on [Ce/H]
217-221 F5.2 --- [Yb/H] Abundance [Yb/H]
223-226 F4.2 --- e_[Yb/H] 1-sigma uncertainty on [Yb/H]
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Acknowledgements:
Giovanni Catanzaro, giovanni.catanzaro(at)inaf.it
References:
Ripepi et al., Paper I 2021MNRAS.508.4047R 2021MNRAS.508.4047R, Cat. J/MNRAS/508/4047
Trentin et al., Paper II 2023MNRAS.519.2331T 2023MNRAS.519.2331T
Molinaro et al., Paper III 2023MNRAS.520.4154M 2023MNRAS.520.4154M
Trentin et al., Paper IV 2024A&A...681A..65T 2024A&A...681A..65T, Cat. J/A+A/681/A65
Bhardwaj et al., Paper V 2024A&A...683A.234B 2024A&A...683A.234B
Trentin et al., Paper VI 2024A&A...690A.246T 2024A&A...690A.246T, Cat. J/A+A/690/A246
(End) Patricia Vannier [CDS] 26-Dec-2025