J/MNRAS/432/3047 LCID project VIII. Cepheids of Leo A (Bernard+, 2013)
The ACS LCID project. VIII. The short-period Cepheids of Leo A.
Bernard E.J., Monelli M., Gallart C., Fiorentino G., Cassisi S.,
Aparicio A., Cole A.A., Drozdovsky I., Hidalgo S.L., Skillman E.D.,
Stetson P.B., Tolstoy E.
<Mon. Not. R. Astron. Soc., 432, 3047-3061 (2013)>
=2013MNRAS.432.3047B 2013MNRAS.432.3047B (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Stars, variable ; Photometry, HST
Keywords: stars: variables: Cepheids - stars: variables: RR Lyrae -
galaxies: evolution - galaxies: individual: Leo A dIrr -
Local Group - galaxies: stellar content
Abstract:
We present the results of a new search for variable stars in the Local
Group dwarf galaxy Leo A, based on deep photometry from the Advanced
Camera for Surveys onboard the Hubble Space Telescope. We detected 166
bona fide variables in our field, of which about 60% are new
discoveries and 33 candidate variables. Of the confirmed variables, we
found 156 Cepheids, but only 10 RR Lyrae stars despite nearly
100percent completeness at the magnitude of the horizontal branch. The
RR Lyrae stars include seven fundamental and three first-overtone
pulsators, with mean periods of 0.636 and 0.366d, respectively. From
their position on the period-luminosity (PL) diagram and light-curve
morphology, we classify 91, 58 and 4 Cepheids as fundamental,
first-overtone and second-overtone mode Classical Cepheids (CC),
respectively, and two as Population II Cepheids. However, due to the
low metallicity of Leo A, about 90percent of the detected Cepheids
have periods shorter than 1.5d. Comparison with theoretical models
indicate that some of the fainter stars classified as CC could be
Anomalous Cepheids. We estimate the distance to Leo A using the tip of
the red giant branch (TRGB) and various methods based on the
photometric and pulsational properties of the Cepheids and RR Lyrae
stars. The distances obtained with the TRGB and RR Lyrae stars agree
well with each other while that from the Cepheid PL relations is
somewhat larger, which may indicate a mild metallicity effect on the
luminosity of the short-period Cepheids. Due to its very low
metallicity, Leo A thus serves as a valuable calibrator of the
metallicity dependences of the variable star luminosities.
Description:
The observations of Leo A were carried out with the ACS onboard the
HST between 2005 December 26 and 2006 January 8.
The candidate variables were extracted from the photometric catalogues
using the variability index of Welch & Stetson (1993AJ....105.1813W 1993AJ....105.1813W)
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 116 166 Pulsational properties of the variable stars
table4.dat 46 33 Properties of the candidate variable stars
tablea1.dat 77 72 Cross-identification with previously known
variables in Leo A
table2.dat 108 3184 Photometry of the variable and candidate
variable stars
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See also:
J/ApJ/699/1742 : LCID project. I. Cetus and Tucana variables (Bernard+, 2009)
J/ApJ/712/1259 : LCID project. II. Variables in IC1613 (Bernard+, 2010)
J/AJ/123/3154 : RV light curves of variable stars in Leo A (Dolphin+, 2002)
J/ApJS/214/19 : Suprime-Cam wide-field photometry of Leo A (Stonkute+, 2014)
J/A+A/614/A144 : Photometry of stars in LeoA HST WFC3 field (Stonkute+, 2018)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- VName Object identification, VNNN
6- 8 A3 --- VType Variable classification (1)
10- 11 I2 h RAh Right Ascension (J2000)
13- 14 I2 min RAm Right Ascension (J2000)
16- 20 F5.2 s RAs Right Ascension (J2000)
22 A1 --- DE- Declination sign (J2000)
23- 24 I2 deg DEd Declination (J2000)
26- 27 I2 arcmin DEm Declination (J2000)
29- 32 F4.1 arcsec DEs Declination (J2000)
34- 38 F5.3 d Per Period
40- 45 F6.3 [d] logPer Logarithm of the Period
47- 52 F6.3 mag F475W Intensity-averaged F475W magnitude
54- 58 F5.3 mag Amp475 The F475W amplitude
60- 65 F6.3 mag F814W Intensity-averaged F814W magnitude
67- 71 F5.3 mag Amp814 The F814W amplitude
73- 77 F5.3 mag F475W-F814W Intensity-averaged F475W-F814W color
79- 84 F6.3 mag Bmag Intensity-averaged B magnitude
86- 90 F5.3 mag AmpB The B amplitude
92- 97 F6.3 mag Vmag Intensity-averaged V magnitude
99-103 F5.3 mag AmpV The V amplitude
105-110 F6.3 mag Imag Intensity-averaged I magnitude
112-116 F5.3 mag AmpI The I amplitude
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Note (1): Variable classification as follows:
ab = Fundamental mode RR Lyrae
c = First-overtone mode RR Lyrae
F = Fundamental mode Classical Cepheid
FO = First overtone Classical Cepheid
SO = Second overtone Classical Cepheid
P2C = Population II Cepheid
Cep = Candidate Cepheid
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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- 4 A4 --- VName Object identification, VCNN
6- 8 A3 --- VType Variable classification (1)
10- 11 I2 h RAh Right Ascension (J2000)
13- 14 I2 min RAm Right Ascension (J2000)
16- 20 F5.2 s RAs Right Ascension (J2000)
22 A1 --- DE- Declination sign (J2000)
23- 24 I2 deg DEd Declination (J2000)
26- 27 I2 arcmin DEm Declination (J2000)
29- 32 F4.1 arcsec DEs Declination (J2000)
34- 39 F6.3 mag F475W Intensity-averaged F475W magnitude
41- 46 F6.3 mag F814W Intensity-averaged F814W magnitude
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Note (1): Variable classification as follows:
ISV = instability strip variable
LPV = long-period variable
MSV = main-sequence variable
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- VName Object identification, VNNN or VCNN
6- 10 F5.3 d Per ?=- Period, this paper
12- 14 A3 --- VType Variable classification, this paper (1)
16- 21 A6 --- ID02 ID from Dolphin et al., 2002,
Cat. J/AJ/123/3154
23- 26 F4.2 d Per02 ?=- Period from Dolphin et al., 2002,
Cat. J/AJ/123/3154
28- 31 F4.2 d e_Per02 ? rms uncertainty on Per02
33- 39 A7 --- VType02 Variable classification from Dolphin et al.,
2002, Cat. J/AJ/123/3154,
[DSC2002] CN-VNN in Simbad (2)
41- 56 A16 -- IDG07 ID from Munich group (3)
57- 63 F7.3 d PerG07 ? Period from Munich group (3)
65- 67 A3 --- IDH94 ID from Hoessel et al., 1994AJ....108..645H 1994AJ....108..645H
[HSK94] VNN in Simbad
70- 77 F8.5 d PerH94 ? Period from Hoessel et al.,
1994AJ....108..645H 1994AJ....108..645H
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Note (1): Veriable type as follows:
aab = fundamental mode RR Lyrae star
F = fundamental mode CC
FO = first-overtone CC
P2C = Population II Cepheid
LPV = long-period variable
MSV = main-sequence variable
Note (2): Type from D02 as follows:
RR = RR Lyrae star
C-FM = fundamental mode CC
C-FO = first-overtone CC
C-SO = second-overtone CC
C = Cepheid of unknown type
Note (3): Munich group (Goessl, Snigula & Hopp PhD thesis, 2006
Ludwig-Maximilians-Universitat Munchen
http://edoc.ub.uni-muenchen.de/4980/
Snigula , PhD thesis , 2006 Ludwig-Maximilians-Universitat Munchen
http://edoc.ub.uni-muenchen.de/4980/
Goessl 2007, PhD thesis , 2007 Ludwig-Maximilians-Universitat Munchen
http://edoc.ub.uni-muenchen.de/7948/
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- VName Object identification, VNNN or VCNN
6- 17 F12.6 d MHJD475 Modified Heliocentric Julian Date for m475/B (1)
19- 24 F6.3 mag F475W The F475W magnitude
26- 30 F5.3 mag e_F475W Error in F475W
32- 37 F6.3 mag Bmag The B magnitude
39- 43 F5.3 mag e_Bmag Error in Bmag
45- 56 F12.6 d MHJDV Modified Heliocentric Julian Date for V (2)
58- 63 F6.3 mag Vmag The V magnitude
65- 69 F5.3 mag e_Vmag Error in Vmag
71- 82 F12.6 d MHJD814 Modified Heliocentric Julian Date for m814/I (1)
84- 89 F6.3 mag F814W The F814W magnitude
91- 95 F5.3 mag e_F814W Error in F814W
97-102 F6.3 mag Imag The I magnitude
104-108 F5.3 mag e_Imag Error in Imag
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Note (1): Heliocentric Julian Date minus 2400000.0 at mid-exposure.
Note (2): Midpoint of F475W and F814W MHJD.
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History:
From electronic version of the journal
References:
Bernard et al., Paper I 2009ApJ...699.1742B 2009ApJ...699.1742B, Cat. J/ApJ/699/1742
Bernard et al., Paper II 2010ApJ...712.1259B 2010ApJ...712.1259B, Cat. J/ApJ/712/1259
Monelli et al., Paper III 2010ApJ...720.1225M 2010ApJ...720.1225M
Monelli et al., Paper IV 2010ApJ...718..707M 2010ApJ...718..707M
Hidalgo et al., Paper V 2011ApJ...730...14H 2011ApJ...730...14H
Monelli et al., Paper VI 2010ApJ...722.1864M 2010ApJ...722.1864M
Monelli et al., Paper VII 2012ApJ...744..157M 2012ApJ...744..157M
Hidalgo et al., Paper IX 2013ApJ...778..103H 2013ApJ...778..103H
Skillman et al., Paper X 2014ApJ...786...44S 2014ApJ...786...44S
Aparicio et al., Paper XI 2016ApJ...823....9A 2016ApJ...823....9A
(End) Patricia Vannier [CDS] 07-Dec-2018