J/ApJ/713/615 Very metal-poor Cepheid models (Marconi+, 2010)
Pulsation models for ultra-low (Z = 0.0004) metallicity classical Cepheids.
Marconi M., Musella I., Fiorentino G., Clementini G., Aloisi A.,
Annibali F., Contreras Ramos R., Saha A., Tosi M., van der Marel R.P.
<Astrophys. J., 713, 615-625 (2010)>
=2010ApJ...713..615M 2010ApJ...713..615M
ADC_Keywords: Models ; Photometry, VRI ; Stars, variable
Keywords: galaxies: dwarf - galaxies: individual (IZw18) - stars: distances -
stars: variables: Cepheids
Abstract:
Classical Cepheids are primary distance indicators playing a
fundamental role in the calibration of the extragalactic distance
scale. The possible dependence of their characteristic
period-luminosity (PL) relation on chemical composition is still
debated in the literature, and the behavior of these pulsators at very
low metallicity regimes is almost unexplored. In order to derive
constraints on the application of the PL relation at low metal
abundances, we investigate the properties of the few ultra-low
metallicity (Z∼0.0004) Cepheids recently discovered in the Blue
Compact Dwarf galaxy IZw18. To this purpose, we have computed an
updated and extended set of nonlinear convective models for Z=0.0004
and Y=0.24, spanning a wide range of stellar masses, and taking into
account the evolutionary constraints for selected luminosity levels.
As a result, we are able to predict the topology of the instability
strip, the variations of all the relevant quantities along the
pulsation cycle, including the morphology of the light curves, the
theoretical period-luminosity-color, period-Wesenheit, and PL
relations at such a low metallicity.
Description:
Using the same pulsation code (see Bono et al. 1999ApJS..122..167B 1999ApJS..122..167B
for details) adopted in our previous investigations of more metallic
Cepheids (Bono et al. 1999ApJS..122..167B 1999ApJS..122..167B; Fiorentino et al.
2002ApJ...576..402F 2002ApJ...576..402F; Marconi et al. 2005ApJ...632..590M 2005ApJ...632..590M), we
investigated for the first time the full amplitude behavior of
metal-poor Cepheid models. To this purpose, we fixed the metal and
helium abundances at Z=0.0004, Y=0.24 and selected model stellar
masses in the range from 4 to 13M☉.
Objects:
-----------------------------------------------------------
RA (2000) DE Designation(s)
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09 34 01.90 +55 14 26.0 IZw18 = Zw I 18 = Mrk 116A
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 64 99 Intrinsic stellar parameters, periods and
intensity-averaged mean magnitudes and colors
for fundamental models with Z=0.0004, Y=0.24,
and l/Hp=1.5
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See also:
J/ApJ/679/71 : Mid-IR period-luminosity relations (Freedman+, 2008)
J/A+A/476/73 : Calibration of Cepheid Period/Luminosity relation (Fouque+,
2007)
J/AJ/134/594 : Araucaria project: Cepheids in WLM galaxy (Pietrzynski+, 2007)
J/ApJ/652/1133 : BVI photometry of NGC 4258 Cepheids (Macri+, 2006)
J/A+A/415/531 : Radial velocities of 10 Galactic Cepheids (Storm+, 2004)
J/A+A/411/361 : VI photometry of extra-galactic Cepheids (Kanbur+, 2003)
J/ApJ/452/238 : HST photometry of I Zw 18 massive stars (Hunter+ 1995)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 F4.1 Msun Mass [4/13] Mass
6- 9 F4.2 [Lsun] logL Log of the luminosity
11- 14 I4 K Teff [4600/6200] Effective temperature
16- 21 F6.4 [d] logP Log of the period
23- 29 F7.4 mag VMag Intensity-weighted mean absolute V band magnitude
31- 36 F6.4 mag B-V The (B-V) color index
38- 43 F6.4 mag V-R The (V-R) color index
45- 50 F6.4 mag V-I The (V-I) color index
52- 57 F6.4 mag V-J The (V-J) color index
59- 64 F6.4 mag V-K The (V-K) color index
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 13-Apr-2012