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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
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:
    ----------------------------------------------------------
       RA   (2000)   DE      Designation(s)
    ----------------------------------------------------------
    09 59 26.5   +30 44 47   Leo A = UGC 5364
    ----------------------------------------------------------

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
table2.dat        35     2444   BV light curves
table3.dat        71      109   Variable stars


Byte-by-byte Description of file: table2.dat

   Bytes Format Units   Label     Explanations

   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


Byte-by-byte Description of file: table3.dat

   Bytes Format Units   Label     Explanations

   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)

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.


History:
    From electronic version of the journal
(End)                         James Marcout, Patricia Bauer [CDS]    06-Sep-2002