J/MNRAS/480/1229 Blazhko effect in the first overtone RR Lyrae (Netzel+, 2018)
Blazhko effect in the first overtone RR Lyrae stars of the OGLE-Galactic bulge
collection.
Netzel H., Smolec R., Soszynski I., Udalski A.
<Mon. Not. R. Astron. Soc., 480, 1229-1246 (2018)>
=2018MNRAS.480.1229N 2018MNRAS.480.1229N (SIMBAD/NED BibCode)
ADC_Keywords: Stars, horizontal branch ; Stars, variable
Keywords: stars: horizontal branch - stars: oscillations -
stars: variable: RR Lyrae
Abstract:
We present the analysis of the Blazhko effect - quasi-periodic
modulation of pulsation amplitude and/or phase - in the Galactic
bulge first overtone RR Lyrae stars (RRc). We used the data gathered
during the fourth phase of the Optical Gravitational Lensing
Experiment (OGLE). Out of 10826 analysed RRc stars, Blazhko effect was
detected in 607 stars which constitute 5.6 per cent of the sample. It
is the largest and most homogeneous sample of modulated RRc stars
analysed so far. Modulation periods cover a wide range, from slightly
above 2d to nearly 3000d. Multiperiodic modulation was detected
in 47 stars. The appearance of modulation in the frequency domain was
studied in detail. Modulation manifests either as close doublets or as
equidistant triplets and multiplets centred on radial mode frequency
and its harmonics. In a significant fraction (29 per cent) of stars,
we have detected the modulation frequency itself, which corresponds to
the modulation of the mean stellar brightness. Our search for period
doubling effect, that was discovered recently in modulated fundamental
mode RR Lyrae stars, and triggered development of new model behind the
Blazhko modulation, yielded negative result. In 104 stars, we detected
additional signals that could correspond to both radial and non-radial
modes. Statistical properties of modulated stars were analysed in
detail and confronted with properties of non-modulated stars and of
modulated fundamental mode RR Lyrae stars. Our analysis provides
constraints for the models to explain the Blazhko phenomenon, which
still remains a puzzle more than hundred years after its discovery.
Description:
In the OGLE collection of variable stars, there are over 38000 RR
Lyrae stars in the Galactic bulge (Soszynski et al.
2014AcA....64..177S 2014AcA....64..177S, Cat. J/AcA/64/177). Among them, 10826 are of RRc
type. We analyzed I-band photometry of these stars to find the
modulation of pulsation amplitude and phase, the Blazhko effect. After
automatic analysis and visual inspection, we have found 607 stars
showing evidence of the Blazhko modulation, i.e. either triplets and
multiplets (BLm) or dublets (BL1) in their power spectra. They
constitute 5.6 per cent of the analysed sample. We classified 463
stars to be BLm (76 per cent of the Blazhko stars) and 144 stars to be
BL1 (24 per cent of the Blazhko stars). Basic parameters for these
stars are presented in Table A1. In Table B1, we provide a list of 105
candidates for Blazhko stars. Majority of these stars come from the
analysis of combined OGLE data. They can be either Blazhko stars or
stars with complex period changes that may mimic quasi-periodic
modulation. Besides first overtone frequency, its harmonics, and
modulation frequencies, we have found additional significant signals
in 104 stars. These stars are marked with 'c' in the remarks column in
Table A1. Full list of stars with additional signals is included in
Table C1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 125 725 Properties of Blazhko stars
tableb1.dat 111 108 Properties of Blazhko candidates
tablec1.dat 68 138 Stars with additional frequencies in power
spectrum
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See also :
J/AcA/64/177 : VI light curves of Galactic Bulge RR Lyrae (Soszynski+, 2014)
J/AcA/67/297 : OGLE Galactic center Cepheids and RR Lyrae (Soszynski+, 2017)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- ID Star Optical Gravitational Lensing Experiment
(OGLE) ID (OGLE-BLG-RRLYR-NNNNN)
22- 24 A3 --- Type Star Blazhko Type (BLm or BL1)
26- 36 F11.9 d P1O Period of the first overtone
38- 48 F11.9 d e_P1O Error on the last digits of P10
50- 59 F10.5 d PBL Blazhko period
61- 69 F9.5 d e_PBL Error on the last digits of PBL
71- 76 F6.4 mag A1O ? Amplitude of the first overtone
78- 83 F6.4 mag e_A1O ? Error on the amplitude of the first overtone
85- 90 F6.4 mag A+ ? Amplitude of the sidepeak on the higher
frequency side of the first overtone
92- 97 F6.4 mag e_A+ ? Error on the last digits of A+
99-104 F6.4 mag A- ? Amplitude of the sidepeak on the lower
frequency side of the first overtone
106-111 F6.4 mag e_A- ? Error on the last digits of A-
113-117 F5.2 --- Qparam ? Asymmetry parameter (1)
119-125 A7 --- Rem ? Remarks (2)
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Note (1): The asymmetry parameter Q is defined as Q=(A+-A-)/(A++A-)
Note (2): Remarks as follows:
a = fmod detected in the power spectrum
b = stars with multiplet structures in the power spectrum
c = stars with additional significant signal
d = multiperiodic Blazhko effect
e = subharmonic of the Blazhko sidepeaks
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- ID Star Optical Gravitational Lensing Experiment
(OGLE) ID (OGLE-BLG-RRLYR-NNNNN)
22- 24 A3 --- Type Star Blazhko Type (BLm or BL1)
26- 36 F11.9 d P1O Period of the first overtone
38- 48 F11.9 d e_P1O Error on the last digits of P10
50- 56 F7.2 d PBL Blazhko period
58- 63 F6.2 d e_PBL Error on the last digits of PBL
65- 70 F6.4 mag A1O Amplitude of the first overtone
72- 77 F6.4 mag e_A1O Error on the amplitude of the first overtone
79- 84 F6.4 mag A+ ? Amplitude of the sidepeak on the higher
frequency side of the first overtone
86- 91 F6.4 mag e_A+ ? Error on the last digits of A+
93- 98 F6.4 mag A- Amplitude of the sidepeak on the lower
frequency side of the first overtone
100-105 F6.4 mag e_A- Error on the last digits of A-
107-111 F5.2 --- Qparam ? Asymmetry parameter (1)
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Note (1): The asymmetry parameter Q is defined as Q=(A+-A-)/(A++A-)
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Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 20 A20 --- ID Star Optical Gravitational Lensing Experiment
(OGLE) ID (OGLE-BLG-RRLYR-NNNNN)
22- 28 F7.5 d P1O Period of the first overtone
30- 38 F9.5 d PX Period of the additional variability
40- 46 F7.5 --- Ps/Pl Ratio of the two probabilities (shorter to
longer)
48- 54 F7.5 mag A1O Amplitude of the first overtone
56- 61 F6.4 --- AX/A1O Amplitude ratio
63- 68 A6 --- expl Possible explanation of the signal (1)
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Note (1): Explanation of the signal as follows:
RR0.61 = Separate group of double-mode radial-non-radial stars
RR0.68 = Stars whose main pulsation mode is the first overtone and
additionally we observe low-amplitude signal with longer
period
anRRdor = Anomalous RRd star
nr/BL = Single signals close to the first overtone frequency, which
can be either due to the Blazhko effect or due to
non-radial pulsation
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 16-May-2022