J/MNRAS/517/1907 Physical parameters of RRab stars with OGLE (Jurcsik+, 2022)
RRab variables with identical light-curve shapes at different pulsation periods.
Jurcsik J., Juhasz A.
<Mon. Not. R. Astron. Soc. 517, 1907-1918 (2022)>
=2022MNRAS.517.1907J 2022MNRAS.517.1907J (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Galactic center ; Milky Way ; Photometry ;
Optical ; Infrared ; Abundances, [Fe/H] ; Stars, diameters ;
Magnitudes, absolute ; Effective temperatures
Keywords: techniques: photometric - stars: fundamental parameters -
stars: variables: RR Lyrae - Galaxy: bulge
Abstract:
In this paper, we report on the detection of RRab stars with
quasi-identical-shape light curves but period differences as large as
0.05-0.21 d using the Galactic bulge data of the OGLE-IV survey. We
have examined stars with shorter periods than the Oosterhoff I ridge
of the bulge. These stars generally have smaller amplitudes and larger
Fourier phase-differences than the typical bulge RRab stars have at
the same period. Many of these 'anomalous' stars have good-quality
light curves without any sign of the Blazhko modulation. Examining
their Fourier parameters revealed that several of these stars show
very similar light curve to the typical bulge RR Lyrae. We found
hundreds of quasi-identical-shape light-curve pairs with different
periods between the 'anomalous'- and the 'normal'-position RRab stars
based on the OGLE I-band data. The OGLE V-band, and the archive VVV
and MACHO surveys Ks-, b- and r-band data of these stars were also
checked for light-curve-shape similarity. Finally, 149 pairs with
identical-shape light curves in each available photometric band were
identified. Calculating the physical properties of the variables using
empirical formulae, on average, -0.5 dex, -0.13 mag, 0.67, and 165 K
differences between the [Fe/H], MV, R/R☉, and Teff values of
the members of the pairs are derived, being the short-period stars
less metal-poor, fainter, smaller, and hotter than the long-period
variables. To explain the existence of variables with different
physical properties and pulsation periods but with identical-shape
light curves is a challenging task for modelling.
Description:
In this study, we aim to show that RRab stars with quasi-identical
light-curve shapes do exist at significantly different pulsation
periods. We use selected sample of Prudil et al. (2017MNRAS.466.2602P 2017MNRAS.466.2602P,
Cat. J/MNRAS/466/2602, P17) of 3341 variables showing Blazhko
modulation using a selected sample of variables from OGLE IV catalog
of Soszynski et al. (2014AcA....64..177S 2014AcA....64..177S, Cat. J/AcA/64/177). Omitting
these Blazhko stars, the uncertain Blazhko candidates and also the
period-changing ones from P17 and applying criteria given in Prudil et
al. (2019MNRAS.484.4833P 2019MNRAS.484.4833P, Cat. J/MNRAS/484/4833) to exclude possible
foreground stars. It remains 4862 bona fide non-Blazhko stars of the
Galactic bulge RRab sample (i.e see section 2). More, the OGLE V, the
Macho instrumental b and r and the VVV Ks-data, if available, were
also used for the stars in our interest. We use Period04 software for
frequency analysis to generate Fourier parameters and their errors.
Next, we separated anomalous A stars selected based on their positions
on the period AI, R21, R31, φ21, φ31 plots using
OGLE data (i.e any star with light-curve parameters below the lower
left-side boundary defined by the main sample of RRab stars on any of
these plots was regarded as 'anomalous' compared to the bulk of the
bulge variables). To find similar-shaped RRLs to A stars among the
normal bulge RRL variables (i.e N stars). Then, we arrived at a sample
of 312 A stars with period shorter than those of 3068 RRab N stars
(located at proper positions in any parameter space, including the
period, i.e see figure 1 of the section 3).
As explained in section 4, we searched for the smallest values of the
square roots of the sums of the normalized quadratic differences
between A and N stars Fourier parameters in lcs I-OGLE band (search
was restricted to variables with period differences larger than 0.05
d). For each A stars we selected the first five N stars with the
smallest differences. To find pairs of identical shapes, the OGLE I-
and V-band light curves of these pairs were then fitted in magnitude
and phase, and their similarity was checked visually (i.e see section
4 figure 2). In the way procedure when it is needed, the MACHO and the
VVV data, if they are available and are of good enough quality are
also checked for similarity. Finally, we remained at 149
quasi-identical shape, but different-period pairs between 95 and 116
RRLs of the A and N samples. IDs, periods and bands used are provided
in table1.dat. As described in section 5, we determined their physical
parameters as ([Fe/H], MV, R, Teff) using light-curve parameters
method from severals studies as Dekany et al. (2021ApJ...920...33D 2021ApJ...920...33D,
Cat. J/ApJ/920/33). These results are available in table2.dat.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 37 149 *Photometry band used and periods RRab pair stars
quasi identical-shape lc at different periods
table2.dat 101 149 Derived physical parameters of RRab pair stars
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Note on table1.dat: The remaining 149 quasi-identical shape but different-period
pair stars are made between 95 and 116 RRLs of the "Anomalous" and "Normal"
samples. Good accuracy VVV and MACHO data are available for 106 and 11 of
these pairs, respectively.The short-period (A) and long-period (N) members of
the pairs are denoted by the 's' and 'l' subscripts in the following (i.e refer
to section 3 and 4).
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See also:
J/MNRAS/491/4752 : Modelled parameters of Cepheid and RR Lyrae
(Bellinger+, 2020)
J/MNRAS/484/4833 : Oosterhoff dichotomy in Galactic bulge (Prudil+, 2019)
J/MNRAS/466/2602 : Blazhko effect in Galactic RR Lyrae (Prudil+, 2017)
J/MNRAS/402/226 : NGC 5053 variables VrI light curves (Arellano Ferro+, 2010)
J/ApJ/920/33 : Fe/H estimation of 104 RR Lyrae from I- light curve
(Dekany+, 2021)
J/ApJ/914/10 : Field RR Lyrae as Gal. probes. III. Abundances
(Crestani+, 2021)
J/ApJ/857/54 : JHKs photometry of VVV RR Lyrae stars (Dekany+, 2018)
J/A+A/371/579 : Empirical relations for cluster RR Lyrae (Kovacs+, 2001)
J/AcA/64/177 : VI light curves of Galactic Bulge RR Lyrae
(Soszynski+, 2014)
II/376 : VISTA Variable in the Via Lactea Survey (VVV) DR4.2
(Minniti+, 2023)
II/364 : VIRAC. The VVV Infrared Astrometric Catalogue (Smith+, 2019)
II/337 : VISTA Variables in the Via Lactea Survey DR1 (Saito+, 2012)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- OGLEs Identification number of short-period pair
member as in designation OGLE BLG-RRLYR-NNNNN
(ID_s) (G1)
7- 13 F7.5 d Ps Period of the short-period pair member
(Period_s)
15- 19 I5 --- OGLEl Identification number of long-period pair
member as in designation OGLE BLG-RRLYR-NNNNN
(ID_l) (G1)
21- 27 F7.5 d Pl Period of the long-period pair member
(Period_l)
29 A1 --- b-MACHO [+ -] Flag to indicate if the MACHO blue band
light curve photometric data is used "+" or
not "-" (b) (1)
31 A1 --- V-OGLE [+] Flag to indicate if the OGLE-IV/OGLE-V V
bands light curve photometric data is used "+"
or not "-" (V) (1)
33 A1 --- r-MACHO [+ -] Flag to indicate if the MACHO red band
light curve photometric data is used "+" or
not "-" (r) (1)
35 A1 --- I-OGLE [+ -] Flag to indicate if the OGLE-IV/OGLE-V I
bands light curve photometric data is used "+"
or not "-" (I) (1)
37 A1 --- Ks-VVV [+ -] Flag to indicate if the VVV IR Ks band
light curve photometric data is used "+" or
not "-" (Ks) (1)
--------------------------------------------------------------------------------
Note (1): Occurences of utilized bands are : 11 "+" and 138 "-" for b-MACHO,
149 "+" and 0 "-" for V-OGLE, 11 "+" and 138 "-" for r-MACHO,
149 "+" and 0 "-" for I-OGLE, 106 "+" and 43 "-" for Ks-VVV.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- OGLEs Identification number of short-period pair
member as in designation OGLE BLG-RRLYR-NNNNN
(ID_s) (G1)
7- 13 F7.5 d Ps Period of the short-period pair member
(Period_s)
15- 19 I5 --- OGLEl Identification number of long-period pair
member as in designation OGLE BLG-RRLYR-NNNNN
(ID_l) (G1)
21- 27 F7.5 d Pl Period of the long-period pair member
(Period_l)
29- 33 F5.2 [Sun] [Fe/H]s Iron to hydrogen abundance ratio for
short-period pair member ([Fe/H]_s) (1)
35- 39 F5.2 [Sun] [Fe/H]s* Iron to hydrogen abundance ratio for
short-period pair member ([Fe/H]_s*) (2)
41- 45 F5.2 [Sun] [Fe/H]l Iron to hydrogen abundance ratio for
long-period pair member ([Fe/H]_l) (1)
47- 51 F5.2 [Sun] [Fe/H]l* Iron to hydrogen abundance ratio for
long-period ([Fe/H]_l*) (2)
53- 56 F4.2 Rsun Rs Star radius for short-period pair member
(R_s) (1)
58- 61 F4.2 Rsun Rs* Star radius for short-period pair member
(R_s*) (2)
63- 66 F4.2 Rsun Rl Star radius for long-period pair member
(R_l) (1)
68- 71 F4.2 Rsun Rl* Star radius for long-period pair member
(R_l*) (2)
73- 76 F4.2 mag VsMag Absolute V magnitude for short-period pair
member (MVs) (1)
78- 81 F4.2 mag VlMag Absolute V magnitude for long-period pair
member (MVl) (1)
83- 86 I4 K Teffs Effective temperature for short-period pair
member (Teffs) (1)
88- 91 I4 K Teffs* Effective temperature for short-period pair
member (Teffs*) (2)
93- 96 I4 K Teffl Effective temperature for long-period pair
member (Teffl) (1)
98-101 I4 K Teffl* Effective temperature for long-period pair
member (Teffl*) (2)
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Note (1): Derived using light curve Fourier parameters as explained in
section 5.
Note (2): Derived using method formula of Dekany et al. 2021ApJ...920...33D 2021ApJ...920...33D,
Cat. J/ApJ/920/33.
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Global notes:
Note (G1): From Blazhko effect in Galactic RR Lyrae catalog from
Prudil et al. 2017MNRAS.466.2602P 2017MNRAS.466.2602P, Cat. J/MNRAS/466/2602.
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 01-Oct-2025