J/A+A/677/A177 EPA K2 first-overtone RR Lyrae stars analysis (Netzel+, 2023)
Frequency analysis of the first-overtone RR Lyrae stars based on the Extended
Aperture Photometry from the K2 data.
Netzel H., Molnar L., Plachy E., Benko J.
<Astron. Astrophys. 677, A177 (2023)>
=2023A&A...677A.177N 2023A&A...677A.177N (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Stars, horizontal branch
Keywords: stars: variables: RR Lyrae - stars: oscillations -
stars: horizontal-branch
Abstract:
Additional low-amplitude signals are observed in many RR Lyrae stars,
beside the pulsations in radial modes. The most common ones are
short-period signals forming a period ratio of around 0.60--0.65 with
the first overtone, or long-period signals forming a period ratio of
around 0.68. The RR Lyrae stars may also exhibit quasi-periodic
modulation of the light curves, known as the Blazhko effect.
We used the extensive sample of the first-overtone RR Lyrae stars
observed by the Kepler telescope during the K2 mission to search for
and characterize these low-amplitude additional signals. K2 data
provides space-based photometry for a statistically significant
sample. Hence this data is excellent to study in detail pulsation
properties of RR Lyrae stars. We used K2 space-based photometry for RR
Lyrae candidates from Campaigns 0-19. We selected RR Lyrae stars
pulsating in the first overtone and performed a frequency analysis for
each star to characterize their frequency contents.
We classified 452 stars as first-overtone RR Lyrae. From that sample,
we selected 281 RR0.61 stars, 67 RR0.68 stars, and 68 Blazhko
stars. We found particularly interesting stars which show all of the
above phenomena simultaneously. We detected signals in RR0.61 stars
that form period ratios lower than observed for the majority of stars.
These signals likely form a new sequence in the Petersen diagram,
around a period ratio of 0.60. In 32 stars we detected additional
signals that form a period ratio close to that expected in RRd stars,
but the classification of these stars as RRd is uncertain. We also
report a discovery of additional signals in eight stars that form a
new group in the Petersen diagram around the period ratio of
0.465-0.490. The nature of this periodicity remains unknown.
Description:
Based on K2 EAP photometry we classified 452 RRc stars listed in
table1.dat.
Properties of selected RR0.61 stars are collected in table2.dat.
Properties of selected RR0.68 stars are collected in table3.dat.
Properties of selected Blazhko stars are collected in table4.dat.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 51 452 RRc stars
table2.dat 100 675 Properties of RR0.61 stars
table3.dat 96 72 Properties of RR0.68 stars
table4.dat 113 70 Properties of Blazhko stars
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See also:
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- EPIC EPIC number
10 A1 --- n_EPIC [*] Note on EPIC (1)
14- 21 F8.4 deg RAdeg Right Ascension (J2000)
24- 31 F8.4 deg DEdeg Declination (J2000)
35- 41 F7.4 mag Kpmag Brightness in Kp passband
44- 51 F8.6 d P Period of pulsation
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Note (1): * when information about mean brightness was not available in the
input catalogue, but was calculated from the light curve during the analysis.
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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- 9 I9 --- EPIC EPIC number
11- 21 F11.9 d P First-overtone period
23- 33 F11.9 d e_P First-overtone period error
35- 45 F11.9 d P0.61 Period of the 0.61 signal
48- 58 F11.9 d e_P0.61 Period of the 0.61 signal error
60- 66 F7.5 --- P0.61/P Period ratio of the 0.61 signal with the
first overtone
68- 74 F7.5 mag Amp First-overtone Fourier amplitude
76- 82 F7.5 mag e_Amp First-overtone Fourier amplitude error
84- 88 F5.3 --- A061/A Amplitude ratio of the 0.61 signal with the
first overtone
90-100 A11 --- Remarks Additional remarks (1)
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Note (1): Remarks as follows:
c = combination signal of the first overtone and the additional signal
d = another additional signal which does not correspond to RR0.61 group
s = subharmonics of the RR0.61 signal
bl = the Blazhko effect
0.68 = signal corresponding to RR0.68 stars
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- EPIC EPIC number
11- 20 F10.8 d P First-overtone period
22- 31 F10.8 d e_P First-overtone period error
33- 43 F11.9 d P0.68 Period of the 0.61 signal
45- 55 F11.9 d e_P0.68 Period of the 0.61 signal error
58- 64 F7.5 --- P/P0.68 Period ratio of the 0.68 signal with the
first overtone
66- 72 F7.5 mag A First-overtone Fourier amplitude
74- 80 F7.5 mag e_A First-overtone Fourier amplitude error
82- 86 F5.3 --- A068/A Amplitude ratio of the 0.68 signal with the
first overtone
88- 96 A9 --- Remarks Additional remarks (1)
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Note (1): Remarks as follows:
c = combination signal of the first overtone and the additional signal
(two stars marked with c? are discussed in the Appendix)
d = another additional signal which does not correspond to the RR0.61,
RR0.68 or Blazhko stars
bl = the Blazhko effect
0.61 = signals corresponding RR0.61 stars
h = harmonic of the additional signal detected
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- EPIC EPIC number
11- 20 F10.8 d P First-overtone period
22- 31 F10.8 d e_P First-overtone period error
33- 42 F10.7 d PBL Blazhko period
44- 52 F9.7 d e_PBL Blazhko period error
54- 60 F7.5 mag A First-overtone Fourier amplitude
62- 68 F7.5 mag e_A First-overtone Fourier amplitude error
70- 76 F7.5 mag A+ ? Fourier amplitude of the higher-frequency
sidepeak
78- 84 F7.5 mag e_A+ ? Fourier amplitude of the higher-frequency
sidepeak error
86- 92 F7.5 mag A- ? Fourier amplitude of the lower-frequency
sidepeak
94-100 F7.5 mag e_A- ? Fourier amplitude of the lower-frequency
sidepeak error
102-113 A12 --- Remarks Additional remarks (1)
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Note (1): Remarks as follows:
a = modulation signal in the low-frequency range
c = combination signals between the Blazhko sidepeaks in the case of
multiple Blazhko modulations
d = additional signal in the frequency spectrum
m = higher multiplets
0.61 = additional signal corresponding to RR0.61 stars
0.68 = additional signal corresponding to RR0.68 stars
v = modulation visible in the light curve data
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Acknowledgements:
Henryka Netzel, henia(at)netzel.pl
(End) Patricia Vannier [CDS] 28-Apr-2023