J/A+A/700/A201 Variable stars on Leo II dSph (Monelli+, 2025)
Variable stars in Local Group galaxies. VII. New insights into the Leo II dSph.
Monelli M., Piersimoni A.-M., Martinez-Vazquez C.-E., Cassisi S.,
Stetson P.-B., Marconi M., Perez-Garcia P.-J., Bono G., Dall'Ora M.,
Fiorentino G., Gallart C., Marengo M.
<Astron. Astrophys. 700, A201 (2025)>
=2025A&A...700A.201M 2025A&A...700A.201M (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Stars, variable ; Photometry, UBVRI ;
Stars, distances
Keywords: stars: variable: Cepheids - stars: variable: RR Lyrae -
galaxies: individual: Leo II - Local Group - galaxies: stellar content
Abstract:
Pulsating variable stars are invaluable tracers for reconstructing the
star formation history and chemical evolution of their host galaxies.
In this work, we explore the variable star population of Leo II, a
distant dwarf spheroidal satellite of the Milky Way.
We analyse an extensive dataset of ground-based BVRI time-series
photometry spanning over 35 years. By examining the properties of RR
Lyrae stars, we constrain the early chemical enrichment and spatial
variation within Leo II. Additionally, we investigate the anomalous
Cepheids in order to connect their characteristics with the galaxy's
prolonged star formation history, as revealed by deep HST/WFC3
colour-magnitude diagrams.
We identified and characterised 175 variable stars, with all but one
associated with Leo∼II. Our work includes the discovery of 25 new RR
Lyrae stars and two new anomalous Cepheids. Moreover, we reclassified
V88 as a BL Her variable star. By employing multiple independent
methods, including metallicity-luminosity relations for RR Lyrae stars
and period-luminosity and period-Wesenheit relations for both RR Lyrae
and anomalous Cepheids, we derived a true distance modulus of
(m-M)_0=21.60±0.03mag, corresponding to 209±4kpc. Furthermore, we
discuss potential formation scenarios for anomalous Cepheids and
suggest that, despite the extended star formation history, they are
all compatible having originated from old binary stars, with no
contribution from young, evolved single stars.
Description:
We analyse the light curve of 175 variable stars detected in the field
of the Leo II dSph galaxy. BVRI are taken from the homogeneous
photometry by P. B. Steton.
Objects:
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RA (2000) DE Designation(s)
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11 13 28.13 +22 09 10.1 Leo II dSph = DDO 93 = Leo B
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 110 175 Summary table of detected variable stars
table3.dat 32 56966 Time series photometry
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See also:
J/AJ/120/284 : Variables in Leo II dwarf spheroidal (Siegel+, 2000)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Star Variable star identifier (V1 to V201),
[SM2000] VNNN in Simbad
6- 7 I2 h RAh Right Ascension J2000, Epoch 2000.0
9- 10 I2 min RAm Right Ascension J2000, Epoch 2000.0
12- 16 F5.2 s RAs Right Ascension J2000, Epoch 2000.0
18 A1 --- DE- Declination sign J2000, Epoch 2000.0
19- 20 I2 deg DEd Declination J2000, Epoch 2000.0
22- 23 I2 arcmin DEm Declination J2000, Epoch 2000.0
25- 28 F4.1 arcsec DEs Declination J2000, Epoch 2000.0
30- 39 F10.8 d Per Period
41- 46 F6.3 mag <Bmag> Mean B magnitude
48- 52 F5.3 mag AB Amplitude in B band
54- 59 F6.3 mag <Vmag> Mean V magnitude
61- 65 F5.3 mag AV Amplitude in V band
67- 72 F6.3 mag <Rmag> ?=99.999 Mean R magnitude
74- 78 F5.3 mag AR ?=9.999 Amplitude in R band
80- 85 F6.3 mag <Imag> Mean I magnitude
87- 91 F5.3 mag AI Amplitude in I band
93- 97 F5.2 [-] [Fe/H] ? Photometric metallicity derived from the
Period-Metallicity-Luminosity relation in
the I band
99-103 A5 --- Type type of variable star
105-108 A4 --- Mode Pulsation mode
110 I1 --- Q1 [0/1] Quality flag for light curve (1)
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Note (1): Flag related with the quality of the light curve as follows:
0 = well sampled and not too noisy
1 = not well sampled and/or too noisy
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Star Variable star identifier (V1 to V201)
6 A1 --- Filter [BVRI] Filter
8- 17 F10.4 d HJD Modified Heliocentric Julian date of
mid-exposure (HJD-2400000)
19- 25 F7.4 mag mag Magnitude in Filter
27- 32 F6.4 mag e_mag rms uncertainty on mag
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Acknowledgements:
Matteo Monelli, matteo.monelli(at)inaf.it
References:
Martinez-Vazquez et al., Paper I 2015MNRAS.454.1509M 2015MNRAS.454.1509M
Martinez-Vazquez et al., Paper II 2016MNRAS.462.4349M 2016MNRAS.462.4349M
Monelli et al., Paper III 2017ApJ...842...60M 2017ApJ...842...60M
Monelli et al., Paper IV 2018MNRAS.479.4279M 2018MNRAS.479.4279M
Martinez-Vazquez et al., Paper V 2021MNRAS.508.1064M 2021MNRAS.508.1064M
Neeley et al., Paper VI 2021ApJ...920..152N 2021ApJ...920..152N, Cat. J/ApJ/920/153
(End) Matteo Monelli [INAF - OAR]. Patricia Vannier [CDS] 25-Jun-2025