J/ApJ/748/107 A global model for MC and Galactic Cepheids (Pejcha+, 2012)
A global physical model for cepheids.
Pejcha O., Kochanek C.S.
<Astrophys. J., 748, 107 (2012)>
=2012ApJ...748..107P 2012ApJ...748..107P
ADC_Keywords: Models ; Stars, variable ; Radial velocities ; Reddening ;
Stars, distances ; Magellanic Clouds
Keywords: distance scale - stars: abundances - stars: variables: Cepheids
Abstract:
We perform a global fit to ∼5000 radial velocity and ∼177000 magnitude
measurements in 29 photometric bands covering 0.3µm to 8.0µm
distributed among 287 Galactic, Large Magellanic Cloud, and Small
Magellanic Cloud Cepheids with P>10 days. We assume that the Cepheid
light curves and radial velocities are fully characterized by
distance, reddening, and time-dependent radius and temperature
variations. We construct phase curves of radius and temperature for
periods between 10 and 100 days, which yield light-curve templates for
all our photometric bands and can be easily generalized to any
additional band. With only four to six parameters per Cepheid,
depending on the existence of velocity data and the amount of freedom
in the distance, the models have typical rms light and velocity curve
residuals of 0.05mag and 3.5km/s. The model derives the mean Cepheid
spectral energy distribution and its derivative with respect to
temperature, which deviate from a blackbody in agreement with
metal-line and molecular opacity effects. We determine a mean
reddening law toward the Cepheids in our sample, which is not
consistent with standard assumptions in either the optical or near-IR.
Based on stellar atmosphere models, we predict the biases in distance,
reddening, and temperature determinations due to the metallicity and
quantify the metallicity signature expected for our fit residuals.
Description:
In order to obtain well-determined templates, the properties of
individual Cepheids, and the global parameters of the model solution,
we require a sample of Cepheids with a large quantity of photometric
and radial velocity measurements. The data include the huge database
of OGLE-III V and I measurements from Soszynski et al. (2008,
Cat. J/AcA/58/163, 2010, Cat. J/AcA/60/17), the major databases of
Berdnikov (1995ASPC...83..349B 1995ASPC...83..349B) and Gorynya et al. (1992, 1996, 1998,
Cat. III/229), the large sample of near-IR measurements by Persson et
al. (2004, Cat. J/AJ/128/2239), and the Spitzer IRAC measurements of
Freedman et al. (2008, Cat. J/ApJ/679/71), Marengo et al.
(2010ApJ...709..120M 2010ApJ...709..120M), and Ngeow & Kanbur (2010ApJ...720..626N 2010ApJ...720..626N).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 63 380 Template coefficients
table5.dat 94 98 Galactic Cepheids
table6.dat 94 136 LMC Cepheids
table7.dat 94 53 SMC Cepheids
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See also:
III/229 : Radial Velocities of Cepheids (Gorynya+ 1992-98)
J/A+A/550/A70 : Galactic & MC Cepheids distance (Groenewegen 2013)
J/MNRAS/420/585 : AKARI observations of SMC Cepheids (Ngeow+, 2012)
J/AcA/61/285 : VI light curves of Galactic Bulge Cepheids (Soszynski+, 2011)
J/A+A/534/A95 : LMC Cepheids radial velocities (Storm+, 2011)
J/ApJ/743/76 : Spitzer photometry of LMC Cepheids (Scowcroft+, 2011)
J/AcA/60/17 : VI light curves of SMC classical Cepheids (Soszynski+, 2010)
J/AcA/60/91 : VI light curves of SMC type II Cepheids (Soszynski+, 2010)
J/AcA/58/163 : VI light curves of LMC classical Cepheids (Soszynski+, 2008)
J/ApJ/679/71 : Mid-IR period-luminosity relations (Freedman+, 2008)
J/A+A/462/599 : JHKs photometry of LMC cluster Cepheids (Testa+, 2007)
J/AJ/128/2239 : JHKs photometry of 92 LMC Cepheids (Persson+, 2004)
J/A+A/415/531 : Radial velocities of 10 Galactic Cepheids (Storm+, 2004)
J/A+A/415/521 : BVRIJK and velocities for MC Cepheids (Storm+, 2004)
J/A+A/404/423 : BVI photometry of Galactic Cepheids (Tammann+, 2003)
J/A+A/385/793 : Cepheids in Magellanic Clouds. II. (Antonello+, 2002)
J/ApJS/142/71 : BVRI observations of LMC Cepheids (Sebo+, 2002)
J/A+AS/143/211 : Galactic Cepheids BVRI photometry (Berdnikov+, 2000)
J/AcA/49/543 : OGLE LMC + SMC Cepheids VI photometry (Pietrzynski+, 1999)
J/AcA/49/223 : BVI photometry of OGLE LMC Cepheids (Udalski+, 1999)
J/AcA/49/437 : BVI photometry of OGLE SMC Cepheids (Udalski+, 1999)
J/PASP/111/812 : V(RI)C Phot of Cepheids in the MC (Barnes+ 1999)
J/ApJS/117/135 : Photometry of Cepheids in Magellanic Clouds (Moffett+ 1998)
J/AJ/116/469 : VI photometry of galactic cepheids (Metzger+ 1998)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 4 F4.2 [10d] logP [0/1] Log of period divided by 10 days (1)
6- 7 I2 --- j [1/20] Coefficient number (1)
9- 21 E13.6 --- ctauj [-0.73/0.22] The cτ,j coefficient (1)
23- 35 E13.6 --- stauj [-0.80/0.24] The sτ,j coefficient (1)
37- 49 E13.6 --- crhoj [-0.23/1] The cρ,j coefficient (1)
51- 63 E13.6 --- srhoj [-0.05/0.12] The sρ,j coefficient (1)
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Note (1): The table lists Fourier coefficients of the templates at NP=19
anchor points from log(P/10d)=0.00 to 1.00. Each anchor point contains
four columns representing the coefficients of the Fourier series for
the variations of the logarithmic temperature τ=log(T/5400K) and
the variations of the logarithmic radius ρ=log(R/10R☉) as:
δτ = Σj [cτ,j cos(2πjφ) +
sτ,j,sin(2πjφ)]
δρ = Σj [cρ,j cos(2πjφ) +
sρ,j,sin(2πjφ)]
Each line gives the j-th coefficient, j=1 ... n, where n=20. The
template at any period is obtained by linear interpolation of all
coefficients in logP bracketing the desired period.
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Byte-by-byte Description of file: table[567].dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Cepheid name
12- 18 F7.4 d Per [10/100] Period
20- 25 F6.3 mag DM [7.8/19.5] Distance modulus
27- 31 F5.3 mag e_DM ? Uncertainty in DM
33- 38 F6.3 mag E(B-V) The E(B-V) reddening
40- 44 F5.3 mag e_E(B-V) Uncertainty in E(B-V)
46- 50 F5.1 km/s <RVel> ? Mean radial velocity
52- 55 F4.1 km/s e_<RVel> ? Uncertainty in <RVel>
57- 61 F5.3 [10Rsun] [0.65/1.53] Mean log radius ρ (1)
63- 67 F5.3 [10Rsun] e_ Uncertainty in
69- 74 F6.3 [5400K] [-0.1/0.2] Mean log temperature τ (1)
76- 80 F5.3 [5400K] e_ Uncertainty in
82- 87 F6.4 % A2 [0.7/7.4] Dimensionless amplitude A2 (1)
89- 94 F6.4 % e_A2 Uncertainty in A2
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Note (1): The radius and temperatures are given with respect to the "mean"
Cepheid with radius of Ro=10R☉ and and temperature To=5400K.
The A2 dimensionless amplitude expresses the variations of radius
and luminosity with the phase φ as (Eqs. (4) and (5)):
* log(R(t)/Ro) = + A2δρ(φ)
* log(T(t)/To) = + A2δτ(φ)
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 17-Oct-2013