J/AJ/123/3154 RV light curves of variable stars in Leo A (Dolphin+, 2002)
Variable stars in Leo A:
RR Lyrae stars, short-period Cepheids, and implications for stellar content.
Dolphin A.E., Saha A., Claver J., Skillman E.D., Cole A.A., Gallagher J.S.,
Tolstoy E., Dohm-Palmer R.C., Mateo M.
<Astron. J. 123, 3154 (2002)>
=2002AJ....123.3154D 2002AJ....123.3154D
ADC_Keywords: Stars, variable ; Photometry, UBV
Keywords: Cepheids - galaxies: individual (Leo A) - Local Group
Abstract:
We present the results of a search for short-period variable stars in
Leo A. We have found 92 candidate variables, including eight candidate
RR Lyrae stars. From the RR Lyrae stars, we measure a distance modulus
of (m-M)0=24.51±0.12, or 0.80±0.04Mpc. This discovery of RR Lyrae
stars confirms for the first time the presence of an ancient (older
than ∼11Gyr) population in Leo A, accounting for at least 0.1% of the
galaxy's V luminosity. We have also discovered a halo of old (more
than ∼2Gyr) stars surrounding Leo A, with a scale length roughly 50%
larger than that of the dominant young population. We also report the
discovery of a large population of Cepheids in Leo A. The median
absolute magnitude of our Cepheid sample is MV=-1.1, fainter than
96% of SMC and 99% of LMC Cepheids. Their periods are also unusual,
with three Cepheids that are deduced to be pulsating in the
fundamental mode having periods of under 1 day. Upon examination,
these characteristics of the Leo A Cepheid population appear to be a
natural extension of the classical Cepheid period-luminosity relations
to low metallicity, rather than being indicative of a large population
of "anomalous" Cepheids. We demonstrate that the periods and
luminosities are consistent with the expected values of low-metallicity
blue helium-burning stars (BHeB's), which populate the instability
strip at lower luminosities than do higher metallicity BHeB's.
Observations of Leo A were obtained at the WIYN 3.5 m telescope on the
nights of 20-22 December 2000, using the MIMO camera.
Objects:
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RA (2000) DE Designation(s)
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09 59 26.5 +30 44 47 Leo A = UGC 5364
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 35 2444 BV light curves
table3.dat 68 109 Variable stars
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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- 6 A6 --- [DSC2002] Variable name (VN-CNN)
8 A1 --- Band [RV] Band
10- 21 F12.4 d HJD Heliocentric Julian date of observation
23- 28 F6.3 mag mag B or V magnitude
30- 34 F5.3 mag e_mag rms uncertainty on mag
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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- 6 A6 --- [DSC2002] Variable name (1)
9 I1 --- Chip Chip number
11- 17 F7.2 pix Xpos X position (2)
19- 25 F7.2 pix Ypos Y position (2)
27- 31 F5.2 mag Vmag V magnitude
33- 36 F4.2 mag e_Vmag rms uncertainty on Vmag
38- 42 F5.2 mag Rmag R magnitude
44- 47 F4.2 mag e_Rmag rms uncertainty on Rmag
49- 52 F4.2 d Per Period
54- 57 F4.2 d e_Per rms uncertainty on Per
58 A1 --- n_Per [*] *: Upper limits of the periods of stars
C2-V08, C2-V63, and C2-V64 are unconstrained
60 I1 --- Q [1/4] Quality flag (3)
62- 71 A10 --- Class Variable classification (4)
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Note (1): Stars listed multiple times have periods with multiple potential
aliases
Note (2): North is to the left, and east is down. 1 pix =0.141".
See Fig. 3 in the paper.
Note (3): Variable-star quality is based on the cleanness of the light
curves, uniqueness of the period, and coherence between V and R light
curves, where 4 is highest quality and 0 is lowest quality
Note (4): RR Lyrae stars classified into subclasses (RRab, RRc, and RRd)
when possible. Cepheid classifications are:
(FM) fundamental mode,
(FO) first overtone,
(SO) second overtone, made only for objects with unambiguous periods
and quality ratings of 3 or 4.
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History:
From electronic version of the journal
(End) James Marcout, Patricia Bauer [CDS] 06-Sep-2002