J/MNRAS/545/F2216 CO and CN in Cepheids (Call+, 2026)
Near-IR CO and CN in classical Cepheids.
Call S., Griffith T., Hintz E., Ardern S., Scowcroft V., Davidson J.,
Boizelle B.
<Mon. Not. R. Astron. Soc. 545, staf2216 (2026)>
=2026MNRAS.545f2216C 2026MNRAS.545f2216C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Infrared sources ; Abundances
Keywords: stars: abundances - stars: variables: Cepheids - infrared: stars
Abstract:
We present medium resolution near-infrared spectral measurements of
the carbon monoxide (CO) and the cyano radical (CN) features in 12
Galactic classical Cepheids. The pulsation periods of our sample range
from 5.5 to 69 days, and the stars studied each had five or more
near-IR spectral observations. The CO and CN measurements were used to
probe CNO abundances of these stars, and elemental abundance values
from the literature were used to identify the trends of [C/N] and
[O/N] with CN and CO. To put these measurements in context, we
performed stellar atmosphere fitting to obtain estimates of stellar
parameters, with a primary focus on effective temperature. Our
measurements and temperature estimates show that CN is significantly
affected by dredge-up of processed material. We provide discussion as
to the potential nature of the recently confirmed classical Cepheid,
ET Vul, and connect our near-infrared CO measurements to the
mid-infrared period-colour-metallicity relation.
Description:
In this paper, we performed index measurements on four temperature
sensitive features. These features were two hydrogen and two
molecular. We compared observations to LTE synthetic model
atmospheres.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 35 12 List of studied Cepheids
tableb1.dat 98 115 Phase measurements and fitting results for
each Cepheid observation
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See also:
J/AJ/156/171 : Cepheid abund.: Multiphase results (Luck, 2018)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Star Cepheid name
10- 11 I2 h RAh Simbad right ascension (J2000)
13- 14 I2 min RAm Simbad right ascension (J2000)
16- 20 F5.2 s RAs Simbad right ascension (J2000)
22 A1 --- DE- Simbad declination sign (J2000)
23- 24 I2 deg DEd Simbad declination (J2000)
26- 27 I2 arcmin DEm Simbad declination (J2000)
29- 32 F4.1 arcsec DEs Simbad declination (J2000)
34- 35 I2 --- Nobs Number of observations in table B1
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Star Cepheid ID
10- 14 F5.3 --- Phase Phase from observation
16- 26 F11.3 d HJD Heliocentric Julian Date
28- 31 I4 --- redchi2 Reduced chi square of spectral fitting
33- 38 F6.1 K Teff Effective temperature
40- 43 F4.2 [cm/s2] logg Surface gravity
45- 48 F4.1 km/s vmic Microturbulence velocity
50- 55 F6.3 mag CO CO index
57- 61 F5.3 mag e_CO CO index uncertainty
63- 68 F6.3 mag CN CN index
70- 74 F5.3 mag e_CN CN index uncertainty
76- 80 F5.3 mag PaB Paschen Beta index
82- 86 F5.3 mag e_PaB Paschen Beta index uncertainty
88- 92 F5.3 mag PaD Paschen Delta index
94- 98 F5.3 mag e_PaD Paschen Delta index uncertainty
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Acknowledgements:
Scott Call, scall(at)uiowa.edu
(End) Patricia Vannier [CDS] 29-Dec-2025