J/MNRAS/438/2440 Fourier analysis of 13095 LMC RR Lyr stars (Deb+, 2014)
Chemical and structural analysis of the Large Magellanic Cloud using the
fundamental mode RR Lyrae stars.
Deb S., Singh H.P.
<Mon. Not. R. Astron. Soc., 438, 2440-2455 (2014)>
=2014MNRAS.438.2440D 2014MNRAS.438.2440D
ADC_Keywords: Magellanic Clouds ; Stars, variable
Keywords: stars: fundamental parameters - stars: Population II -
stars: variables: RR Lyrae - Magellanic Clouds -
galaxies: statistics - galaxies: structure
Abstract:
We present a careful and detailed light-curve analysis of publicly
available I-band data on fundamental mode RR Lyrae (RRab) stars of the
Large Magellanic Cloud (LMC) obtained by the Optical Gravitational
Lensing Experiment phase-III project. Using the Fourier parameters of
13095 RRab stars, metallicities and absolute magnitudes of individual
stars are obtained. The representation of stars on the P-φ31V
plane shows the existence of three significant metallicity groups with
mean metallicities as -1.20±0.12, -1.57±0.10 and -1.89±0.09dex.
The corresponding absolute magnitudes of these three groups are
obtained as 0.70±0.08, 0.59±0.06 and 0.49±0.08mag, respectively.
Distribution of these three groups as a function of vertical |z|
distance indicates that the formation of the LMC disc predates the
formation of the inner halo. Issue of the existence of a metallicity
gradient as a function of galactocentric distances has also been
addressed. Approximating the structure of the LMC disc as a triaxial
ellipsoid, the inclination angle (i) relative to the plane of
the sky and the position angle of the line of nodes (θlon) were
estimated as 24.20° and 176.01°, respectively. The axes
ratios and the eccentricity were also determined using the principal
axis transformation method.
Description:
We selected RRab stars from OGLE-III catalogue that consists of 8yr
archival data identified and characterized by the Fourier coefficients
of the light curves (Soszynski et al., 2009AcA....59....1S 2009AcA....59....1S, Cat.
J/AcA/59/1). The catalogue contains 17693 RRab stars having a mean
period of <Pab≥0.576d. The OGLE field in the LMC covers nearly
40°2. Most of the observations were carried out using the
Cousins I-band filter with exposure time of 180s having an average of
400 photometric observations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 88 13095 Various parameters extracted from Fourier
coefficients for 13095 RRab variables
table1.dat 175 13095 *Fourier parameters of 13095 OGLE RRab stars
table2.dat 154 13095 *Fourier parameters of 13095 OGLE RRab stars
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Note on table1.dat and table2.dat: Fourier parameters of 13095 OGLE RRab stars
with increasing period used for the analysis obtained from the Fourier cosine
decomposition of the I-band light curves as given by equation (2).
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See also:
J/AcA/59/1 : VI light curves of LMC RR Lyrae stars (Soszynski+, 2009)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- --- [OGLE-LMC-RRLYR-]
16- 20 I05 --- OGLE [1/24902] OGLE-LMC-RRLYR identification
number, in Simbad.
22- 26 F5.2 [Sun] [Fe/H] [-2.5/-0.8] Metallicity
28- 31 F4.2 [Sun] e_[Fe/H] rms uncertainty on [Fe/H] (1)
33- 36 F4.2 mag VMAG [0.2/1.1] Absolute V magnitude
38- 42 F5.3 mag e_VMAG rms uncertainty on VMAG (1)
44- 47 F4.2 [Lsun] logL Luminosity
49- 53 F5.3 [Lsun] e_logL rms uncertainty on logL (1)
55- 59 F5.2 mag <Imag> Average I magnitude
61- 65 F5.2 mag <Vmag> Average V magnitude
67- 71 F5.2 mag MOD [16.3/20.2] Distance modulus
73- 76 F4.2 mag e_MOD rms uncertainty no MOD (1)
78- 83 F6.2 kpc Dist [18/107] Distance
85- 88 F4.2 kpc e_Dist rms uncertainty on Dist (1)
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Note (1): Errors represent the uncertainties in the Fourier parameters.
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- --- [OGLE-LMC-RRLYR-]
16- 20 I05 --- OGLE [1/24902] OGLE identification number
22- 30 F9.7 d Per [0.4/0.83] Period
32- 39 F8.5 mag A0 [17/21] Fundamental Fourier coefficient A0 (2)
41- 47 F7.5 mag A1 First order Fourier coefficient A1 (2)
49- 55 F7.5 mag A2 Second order Fourier coefficient A2 (2)
57- 63 F7.5 mag A3 Third order Fourier coefficient A3 (2)
65- 71 F7.5 mag A4 Fourth order Fourier coefficient A4 (2)
73- 79 F7.5 rad phi1 [0/6.283] φ1 Fourier coefficient (2)
81- 87 F7.5 rad phi2 [0/6.283] φ2 Fourier coefficient (2)
89- 95 F7.5 rad phi3 [0/6.283] φ3 Fourier coefficient (2)
97-103 F7.5 rad phi4 [0/6.283] φ4 Fourier coefficient (2)
105-111 F7.5 mag e_A0 rms uncertainty on A0
113-119 F7.5 mag e_A1 rms uncertainty on A1
121-127 F7.5 mag e_A2 rms uncertainty on A2
129-135 F7.5 mag e_A3 rms uncertainty on A3
137-143 F7.5 mag e_A4 rms uncertainty on A4
145-151 F7.5 rad e_phi1 rms uncertainty on phi1
153-159 F7.5 rad e_phi2 rms uncertainty on phi2
161-167 F7.5 rad e_phi3 rms uncertainty on phi3
169-175 F7.5 rad e_phi4 rms uncertainty on phi4
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Note (2): coefficients of the Fourier decomposition
m(t) = A0 + ΣAicos(2iπ/P(t-t0)+φi)
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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- 15 A15 --- --- [OGLE-LMC-RRLYR-]
16- 20 I05 --- OGLE [1/24902] OGLE identification number
22- 25 I4 --- Nobs [42/1600] Number of observations
27- 34 F8.5 --- chi2r [0/15] Reduced χ2 value
36- 42 F7.5 mag sigfit [0.01/0.21] σfit
44- 50 F7.5 mag AI Amplitude in I band
52- 58 F7.5 --- R21 R21 = A2/A1 Fourier coefficient
60- 66 F7.5 --- R31 R31 = A3/A1 Fourier coefficient
68- 74 F7.5 --- R41 R41 = A4/A1 Fourier coefficient
76- 82 F7.5 rad phi21 [0/6.283] φ21 Fourier coefficient
84- 90 F7.5 rad phi31 [0/6.283] φ31 Fourier coefficient
92- 98 F7.5 rad phi41 [0/6.283] φ41 Fourier coefficient
100-106 F7.5 mag e_AI rms uncertainty on AI
108-114 F7.5 --- e_R21 rms uncertainty on R21
116-122 F7.5 --- e_R31 rms uncertainty on R31
124-130 F7.5 --- e_R41 rms uncertainty on R41
132-138 F7.5 rad e_phi21 rms uncertainty on phi21
140-146 F7.5 rad e_phi31 rms uncertainty on phi31
148-154 F7.5 rad e_phi41 rms uncertainty on phi41
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 05-Dec-2014