J/MNRAS/463/1332 Anomalous RRd stars in Magellanic Clouds (Soszynski+, 2016)
Anomalous double-mode RR Lyrae stars in the Magellanic Clouds.
Soszynski I., Smolec R., Dziembowski W.A., Udalski A., Szymanski M.K.,
Wyrzykowski L., Ulaczyk K., Poleski R., Pietrukowicz P., Kozlowski S.,
Skowron D., Skowron J., Mroz P., Pawlak M.
<Mon. Not. R. Astron. Soc., 463, 1332-1341 (2016)>
=2016MNRAS.463.1332S 2016MNRAS.463.1332S (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Stars, variable ; Asteroseismology
Keywords: stars: oscillations - stars: variables: RR Lyrae - Magellanic Clouds
Abstract:
We report the discovery of a new subclass of double-mode RR Lyrae
stars in the Large and Small Magellanic Clouds. The sample of 22
pulsating stars has been extracted from the latest edition of the
Optical Gravitational Lensing Experiment collection of RR Lyrae
variables in the Magellanic System. The stars pulsating simultaneously
in the fundamental (F) and first-overtone (1O) modes have distinctly
different properties than regular double-mode RR Lyrae variables (RRd
stars). The P1O/PF period ratios of our anomalous RRd stars are
within a range of 0.725-0.738, while 'classical' double-mode RR Lyrae
variables have period ratios in the range of 0.742-0.748. In contrast
to the typical RRd stars, in the majority of the anomalous pulsators,
the F-mode amplitudes are higher than the 1O-mode amplitudes. The
light curves associated with the F-mode in the anomalous RRd stars
show different morphology than the light curves of, both, regular RRd
stars and single-mode RRab stars. Most of the anomalous double-mode
stars show long-term modulations of the amplitudes (Blazhko-like
effect). Translating the period ratios into the abundance parameter,
Z, we find for our stars Z∈(0.002, 0.005) - an order of
magnitude higher values than typical for RR Lyrae stars. The mass
range of the RRd stars inferred from the WI versus PF diagram is
(0.55-0.75)M☉. These parameters cannot be accounted for with
single star evolution assuming a Reimers-like mass-loss. Much greater
mass-loss caused by interaction with other stars is postulated. We
blame the peculiar pulsation properties of our stars to the parametric
resonance instability of the 1O-mode to excitation of the F- and
2O-modes as with the inferred parameters of the stars
2ω1O~=ωF+ω2O.
Description:
The sample of anomalous RRd stars has been extracted from the OGLE
collection of 45451 RR Lyrae variables in the Magellanic Clouds
(Soszyski et al., 2016AcA....66..131S 2016AcA....66..131S).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 70 22 Basic properties of anomalous RRd stars
tablea.dat 81 133 Identifications of all detected frequencies
(tables A1-A22 of the paper)
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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- 20 A20 --- Name Star name
22- 29 F8.6 d P1O 1O mode period
31- 38 F8.6 d PF F mode period
40- 45 F6.4 --- F1O/PF P1O/PF period ratio
47- 51 F5.3 mag AF Fourier amplitude of the fundamental mode
53- 56 F4.2 --- A1O/AF A1O/AF amplitude ratio
58- 63 F6.3 mag <Imag> Mean I-band magnitude
65- 70 F6.3 mag <Vmag> ? Mean V-band magnitude
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Byte-by-byte Description of file: tablea.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- Name Star name
22- 41 A20 --- FreqID Frequency identification
44- 51 F8.6 d-1 Freq Frequency
54- 60 F7.6 d-1 e_Freq ? rms uncertainty on Freq
64- 66 I3 mmag A ? Amplitude
68 I1 mmag e_A ? rms uncertainty on A
70- 73 F4.2 rad phi ? Phase
75- 78 F4.2 rad e_phi ? rms uncertainty on rad
80- 81 A2 --- Rem [bl ] Remarks (1)
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Note (1): bl indicates a frequency of the Blazhko modulation, In case no
significant peak was detected in the frequency spectrum directly
at ν=νm. Amplitude and phase are not given then.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 03-May-2018