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J/MNRAS/369/723    Fourier parameters for Cepheid variables    (Ngeow+, 2006)
Period-colour and amplitude-colour relations in classical Cepheid variables.
IV: The multi-phase relations
    Ngeow C., Kanbur S.M
   <Mon. Not. R. Astron. Soc. 369, 723 (2006)>
   =2006MNRAS.369..723N
ADC_Keywords: Stars, variable ; Photometry

Keywords: Cepheids - stars: fundamental parameters


Abstract:
    The superb phase resolution and quality of the OGLE data on LMC and
    SMC Cepheids, together with existing data on Galactic Cepheids, are
    combined to study the period-colour (PC) and amplitude-colour (AC)
    relations as a function of pulsation phase. Our results confirm
    earlier work that the LMC PC relation (at mean light) is more
    consistent with two lines of differing slopes, separated at a period
    of 10 days. However, our multi-phase PC relations reveal much new
    structure which can potentially increase our understanding of Cepheid
    variables. These multi-phase PC relations provide insight into why the
    Galactic PC relation is linear but the LMC PC relation is non-linear.
    This is because the LMC PC relation is shallower for short (logP<1)
    and steeper for long (logP>1) period Cepheids than the corresponding
    Galactic PC relation. Both of the short and long period Cepheids in
    all three galaxies exhibit the steepest and shallowest slopes at
    phases around 0.75-0.85, respectively. A consequence is that the PC
    relation at phase ∼0.8 is highly non-linear. Further, the Galactic and
    LMC Cepheids with logP>1 display a flat slope in the PC plane at
    phases close to the maximum light. When the LMC period- luminosity
    (PL) relation is studied as a function of phase, we confirm that it
    changes with the PC relation. The LMC PL relation in V- and I-band
    near the phase of 0.8 provides compelling evidence that this relation
    is also consistent with two lines of differing slopes joined at a
    period close to 10 days.

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
tablea1.dat      209      154   V-band Fourier parameters for the Galactic Cepheid
tablea2.dat      209      154   I-band Fourier parameters for the Galactic Cepheid
tablea3.dat      209      641   V-band Fourier parameters for the LMC Cepheid
tablea4.dat      209      641   I-band Fourier parameters for the LMC Cepheid
tablea5.dat      209      390   V-band Fourier parameters for the SMC Cepheid
tablea6.dat      209      390   I-band Fourier parameters for the SMC Cepheid


See also:
 J/AcA/49/543 : OGLE LMC + SMC Cepheids VI photometry (Pietrzynski+, 1999)
 J/AcA/49/437 : BVI photometry of OGLE SMC Cepheids (Udalski+, 1999)
 J/AcA/49/223 : BVI photometry of OGLE LMC Cepheids  (Udalski+, 1999)


Byte-by-byte Description of file: tablea?.dat

   Bytes Format Units   Label     Explanations

   1- 15  A15   ---     Name      Cepheid identification (1)
  17- 21  F5.3  mag     E(B-V)    Extinction value
  23- 30  F8.6  [d]     log(P)    Log period
  32- 37  F6.3  mag     A0        V or I band mean magnitude
  39- 44  F6.4  mag     A1        Fourier amplitude A1
  46- 51  F6.4  rad     phi1      Fourier phase phi1
  53- 58  F6.4  mag     A2        Fourier amplitude A2
  60- 65  F6.4  rad     phi2      Fourier phase phi2
  71- 76  F6.4  mag     A3        Fourier amplitude A3
  78- 83  F6.4  rad     phi3      Fourier phase phi3
  85- 90  F6.4  mag     A4        ? Fourier amplitude A4
  92- 97  F6.4  rad     phi4      ? Fourier phase phi4
  99-104  F6.4  mag     A5        ? Fourier amplitude A5
 106-111  F6.4  rad     phi5      ? Fourier phase phi5
 113-118  F6.4  mag     A6        ? Fourier amplitude A6
 120-125  F6.4  rad     phi6      ? Fourier phase phi6
 127-132  F6.4  mag     A7        ? Fourier amplitude A7
 134-139  F6.4  rad     phi7      ? Fourier phase phi7
 141-146  F6.4  mag     A8        ? Fourier amplitude A8
 148-153  F6.4  rad     phi8      ? Fourier phase phi8
 155-160  F6.4  mag     A9        ? Fourier amplitude A9
 162-167  F6.4  rad     phi9      ? Fourier phase phi9
 169-174  F6.4  mag     A10       ? Fourier amplitude A10
 176-181  F6.4  rad     phi10     ? Fourier phase phi10
 183-188  F6.4  mag     A11       ? Fourier amplitude A11
 190-195  F6.4  rad     phi11     ? Fourier phase phi11
 197-202  F6.4  mag     A12       ? Fourier amplitude A12
 204-209  F6.4  rad     phi12     ? Fourier phase phi12

Note (1): Variable name for Galactic Cepheids (tables A1 and A2),
          OGLE (Udalski et al., 1999, Cat. J/AcA/49/437) name for
          SMC Cepheids (tables A3 and A4),
          OGLE (Udalski et al., 1999, Cat. J/AcA/49/223) or
          HV (Hodge & Wright, 1967SAOP.4699....1H) name for LMC Cephedis
          (tables A5 and A6)


Acknowledgements: Chow-Choong Ngeow, cngeow(at)astro.uiuc.edu

(End)                                      Patricia Vannier [CDS]    19-May-2006