The MACHO project large magellanic cloud variable star inventory. XI. Frequency analysis of the fundamental-mode RR Lyrae stars

C. Alcock, D. R. Alves, A. Becker, D. Bennett, K. H. Cook, A. Drake, K. Freeman, M. Geha, K. Griest, G. Kovács, M. Lehner, S. Marshall, D. Minniti, C. Nelson, B. Peterson, P. Popowski, M. Pratt, P. Quinn, A. Rodgers, C. StubbsW. Sutherland, T. Vandehei, D. L. Welch

Resultado de la investigación: Article

75 Citas (Scopus)

Resumen

We have frequency-analyzed 6391 variables classified earlier as fundamental-mode RR Lyrae (RRO) stars in the MACHO database on the Large Magellanic Cloud (LMC). The overwhelming majority (i.e., 96%) of these variables have been proved to be indeed RR0 stars, whereas the remaining ones have fallen into one of the following categories: single- and double-mode Cepheids, binaries, first-overtone and double-mode RR Lyrae stars, and nonclassified variables. Special attention has been paid to the properties of the amplitude- and phase-modulated RR0 stars (the Blazhko stars). We found altogether 731 Blazhko variables showing either a doublet or an equidistant triplet pattern at the main pulsation component in their frequency spectra. This sample overwhelmingly exceeds the number of Blazhko stars known in all other systems combined. The incidence rate of the Blazhko variables among the RR0 stars in the LMC is 11.9%, which is 3 times higher than their rate among the first-overtone RR Lyrae stars. No difference is found in the average brightness between the single-mode and Blazhko variables. However, the latter ones show a somewhat lower degree of skewness in their average light curves and a concomitant lower total amplitude in their modulation-free light curves. From the frequency spectra we found that variables with larger modulation amplitudes at the higher frequency side of the main pulsation component are 3 times more common than the ones showing the opposite amplitude pattern. A search for a modulation component with the Blazhko period in the average brightness of the individual variables showed the existence of such a modulation with an overall amplitude of ≈0.006 mag. On the other hand, a similar search for quadruple modulation patterns around the main pulsation component has failed to clearly detect such components at the ≈0.004 mag level. This means that the amplitudes of the quadruple components (if they exist) should be, on average, at least 10 times smaller than those of the triplet components. This finding and the existence of Blazhko variables with highly asymmetric modulation amplitudes not only question the validity of the magnetic oblique rotator model but also put stringent constraints on models based on mode-coupling theories.

Idioma originalEnglish
Páginas (desde-hasta)597-609
Número de páginas13
PublicaciónAstrophysical Journal
Volumen598
N.º1 I
DOI
EstadoPublished - 20 nov 2003

Huella dactilar

massive compact halo objects
variable stars
frequency analysis
Magellanic clouds
stars
modulation
light curve
brightness
skewness
harmonics
project
coupled modes
incidence

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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Alcock, C., Alves, D. R., Becker, A., Bennett, D., Cook, K. H., Drake, A., ... Welch, D. L. (2003). The MACHO project large magellanic cloud variable star inventory. XI. Frequency analysis of the fundamental-mode RR Lyrae stars. Astrophysical Journal, 598(1 I), 597-609. https://doi.org/10.1086/378689
Alcock, C. ; Alves, D. R. ; Becker, A. ; Bennett, D. ; Cook, K. H. ; Drake, A. ; Freeman, K. ; Geha, M. ; Griest, K. ; Kovács, G. ; Lehner, M. ; Marshall, S. ; Minniti, D. ; Nelson, C. ; Peterson, B. ; Popowski, P. ; Pratt, M. ; Quinn, P. ; Rodgers, A. ; Stubbs, C. ; Sutherland, W. ; Vandehei, T. ; Welch, D. L. / The MACHO project large magellanic cloud variable star inventory. XI. Frequency analysis of the fundamental-mode RR Lyrae stars. En: Astrophysical Journal. 2003 ; Vol. 598, N.º 1 I. pp. 597-609.
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title = "The MACHO project large magellanic cloud variable star inventory. XI. Frequency analysis of the fundamental-mode RR Lyrae stars",
abstract = "We have frequency-analyzed 6391 variables classified earlier as fundamental-mode RR Lyrae (RRO) stars in the MACHO database on the Large Magellanic Cloud (LMC). The overwhelming majority (i.e., 96{\%}) of these variables have been proved to be indeed RR0 stars, whereas the remaining ones have fallen into one of the following categories: single- and double-mode Cepheids, binaries, first-overtone and double-mode RR Lyrae stars, and nonclassified variables. Special attention has been paid to the properties of the amplitude- and phase-modulated RR0 stars (the Blazhko stars). We found altogether 731 Blazhko variables showing either a doublet or an equidistant triplet pattern at the main pulsation component in their frequency spectra. This sample overwhelmingly exceeds the number of Blazhko stars known in all other systems combined. The incidence rate of the Blazhko variables among the RR0 stars in the LMC is 11.9{\%}, which is 3 times higher than their rate among the first-overtone RR Lyrae stars. No difference is found in the average brightness between the single-mode and Blazhko variables. However, the latter ones show a somewhat lower degree of skewness in their average light curves and a concomitant lower total amplitude in their modulation-free light curves. From the frequency spectra we found that variables with larger modulation amplitudes at the higher frequency side of the main pulsation component are 3 times more common than the ones showing the opposite amplitude pattern. A search for a modulation component with the Blazhko period in the average brightness of the individual variables showed the existence of such a modulation with an overall amplitude of ≈0.006 mag. On the other hand, a similar search for quadruple modulation patterns around the main pulsation component has failed to clearly detect such components at the ≈0.004 mag level. This means that the amplitudes of the quadruple components (if they exist) should be, on average, at least 10 times smaller than those of the triplet components. This finding and the existence of Blazhko variables with highly asymmetric modulation amplitudes not only question the validity of the magnetic oblique rotator model but also put stringent constraints on models based on mode-coupling theories.",
keywords = "Globular clusters: general, Stars: horizontal-branch, Stars: oscillations, Stars: variables: other (RR Lyrae)",
author = "C. Alcock and Alves, {D. R.} and A. Becker and D. Bennett and Cook, {K. H.} and A. Drake and K. Freeman and M. Geha and K. Griest and G. Kov{\'a}cs and M. Lehner and S. Marshall and D. Minniti and C. Nelson and B. Peterson and P. Popowski and M. Pratt and P. Quinn and A. Rodgers and C. Stubbs and W. Sutherland and T. Vandehei and Welch, {D. L.}",
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Alcock, C, Alves, DR, Becker, A, Bennett, D, Cook, KH, Drake, A, Freeman, K, Geha, M, Griest, K, Kovács, G, Lehner, M, Marshall, S, Minniti, D, Nelson, C, Peterson, B, Popowski, P, Pratt, M, Quinn, P, Rodgers, A, Stubbs, C, Sutherland, W, Vandehei, T & Welch, DL 2003, 'The MACHO project large magellanic cloud variable star inventory. XI. Frequency analysis of the fundamental-mode RR Lyrae stars', Astrophysical Journal, vol. 598, n.º 1 I, pp. 597-609. https://doi.org/10.1086/378689

The MACHO project large magellanic cloud variable star inventory. XI. Frequency analysis of the fundamental-mode RR Lyrae stars. / Alcock, C.; Alves, D. R.; Becker, A.; Bennett, D.; Cook, K. H.; Drake, A.; Freeman, K.; Geha, M.; Griest, K.; Kovács, G.; Lehner, M.; Marshall, S.; Minniti, D.; Nelson, C.; Peterson, B.; Popowski, P.; Pratt, M.; Quinn, P.; Rodgers, A.; Stubbs, C.; Sutherland, W.; Vandehei, T.; Welch, D. L.

En: Astrophysical Journal, Vol. 598, N.º 1 I, 20.11.2003, p. 597-609.

Resultado de la investigación: Article

TY - JOUR

T1 - The MACHO project large magellanic cloud variable star inventory. XI. Frequency analysis of the fundamental-mode RR Lyrae stars

AU - Alcock, C.

AU - Alves, D. R.

AU - Becker, A.

AU - Bennett, D.

AU - Cook, K. H.

AU - Drake, A.

AU - Freeman, K.

AU - Geha, M.

AU - Griest, K.

AU - Kovács, G.

AU - Lehner, M.

AU - Marshall, S.

AU - Minniti, D.

AU - Nelson, C.

AU - Peterson, B.

AU - Popowski, P.

AU - Pratt, M.

AU - Quinn, P.

AU - Rodgers, A.

AU - Stubbs, C.

AU - Sutherland, W.

AU - Vandehei, T.

AU - Welch, D. L.

PY - 2003/11/20

Y1 - 2003/11/20

N2 - We have frequency-analyzed 6391 variables classified earlier as fundamental-mode RR Lyrae (RRO) stars in the MACHO database on the Large Magellanic Cloud (LMC). The overwhelming majority (i.e., 96%) of these variables have been proved to be indeed RR0 stars, whereas the remaining ones have fallen into one of the following categories: single- and double-mode Cepheids, binaries, first-overtone and double-mode RR Lyrae stars, and nonclassified variables. Special attention has been paid to the properties of the amplitude- and phase-modulated RR0 stars (the Blazhko stars). We found altogether 731 Blazhko variables showing either a doublet or an equidistant triplet pattern at the main pulsation component in their frequency spectra. This sample overwhelmingly exceeds the number of Blazhko stars known in all other systems combined. The incidence rate of the Blazhko variables among the RR0 stars in the LMC is 11.9%, which is 3 times higher than their rate among the first-overtone RR Lyrae stars. No difference is found in the average brightness between the single-mode and Blazhko variables. However, the latter ones show a somewhat lower degree of skewness in their average light curves and a concomitant lower total amplitude in their modulation-free light curves. From the frequency spectra we found that variables with larger modulation amplitudes at the higher frequency side of the main pulsation component are 3 times more common than the ones showing the opposite amplitude pattern. A search for a modulation component with the Blazhko period in the average brightness of the individual variables showed the existence of such a modulation with an overall amplitude of ≈0.006 mag. On the other hand, a similar search for quadruple modulation patterns around the main pulsation component has failed to clearly detect such components at the ≈0.004 mag level. This means that the amplitudes of the quadruple components (if they exist) should be, on average, at least 10 times smaller than those of the triplet components. This finding and the existence of Blazhko variables with highly asymmetric modulation amplitudes not only question the validity of the magnetic oblique rotator model but also put stringent constraints on models based on mode-coupling theories.

AB - We have frequency-analyzed 6391 variables classified earlier as fundamental-mode RR Lyrae (RRO) stars in the MACHO database on the Large Magellanic Cloud (LMC). The overwhelming majority (i.e., 96%) of these variables have been proved to be indeed RR0 stars, whereas the remaining ones have fallen into one of the following categories: single- and double-mode Cepheids, binaries, first-overtone and double-mode RR Lyrae stars, and nonclassified variables. Special attention has been paid to the properties of the amplitude- and phase-modulated RR0 stars (the Blazhko stars). We found altogether 731 Blazhko variables showing either a doublet or an equidistant triplet pattern at the main pulsation component in their frequency spectra. This sample overwhelmingly exceeds the number of Blazhko stars known in all other systems combined. The incidence rate of the Blazhko variables among the RR0 stars in the LMC is 11.9%, which is 3 times higher than their rate among the first-overtone RR Lyrae stars. No difference is found in the average brightness between the single-mode and Blazhko variables. However, the latter ones show a somewhat lower degree of skewness in their average light curves and a concomitant lower total amplitude in their modulation-free light curves. From the frequency spectra we found that variables with larger modulation amplitudes at the higher frequency side of the main pulsation component are 3 times more common than the ones showing the opposite amplitude pattern. A search for a modulation component with the Blazhko period in the average brightness of the individual variables showed the existence of such a modulation with an overall amplitude of ≈0.006 mag. On the other hand, a similar search for quadruple modulation patterns around the main pulsation component has failed to clearly detect such components at the ≈0.004 mag level. This means that the amplitudes of the quadruple components (if they exist) should be, on average, at least 10 times smaller than those of the triplet components. This finding and the existence of Blazhko variables with highly asymmetric modulation amplitudes not only question the validity of the magnetic oblique rotator model but also put stringent constraints on models based on mode-coupling theories.

KW - Globular clusters: general

KW - Stars: horizontal-branch

KW - Stars: oscillations

KW - Stars: variables: other (RR Lyrae)

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