The MACHO project Large Magellanic Cloud variable-star inventory. IX. Frequency analysis of the first-overtone RR Lyrae stars and the indication for nonradial pulsations

C. Alcock, R. Allsman, D. R. Alves, T. Axelrod, A. Becker, D. Bennett, C. Clement, K. H. Cook, A. Drake, K. Freeman, M. Geha, K. Griest, G. Kovács, D. W. Kurtz, M. Lehner, S. Marshall, D. Minniti, C. Nelson, B. Peterson, P. PopowskiP. Quinn, A. Rodgers, J. Rowe, C. Stubbs, W. Sutherland, A. Tomaney, T. Vandehei, D. L. Welch

Resultado de la investigación: Article

90 Citas (Scopus)

Resumen

More than 1300 variables classified provisionally as first-overtone RR Lyrae pulsators in the MACHO variable-star database of the Large Magellanic Cloud (LMC) have been subjected to standard frequency analysis. Based on the remnant power in the prewhitened spectra, we found 70% of the total population to be monoperiodic. The remaining 30% (411 stars) are classified as one of nine types according to their frequency spectra. Several types of RR Lyrae pulsational behavior are clearly identified here for the first time. Together with the earlier discovered double-mode (fundamental and first-overtone) variables, this study increased the number of known double-mode stars in the LMC to 181. During the total 6.5 yr time span of the data, 10% of the stars showed strong period changes. The size, and in general also the patterns of the period changes, exclude a simple evolutionary explanation. We also discovered two additional types of multifrequency pulsators with low occurrence rates of 2% for each. In the first type, there remains one closely spaced component after prewhitening by the main pulsation frequency. In the second type, the number of remnant components is two; they are also closely spaced, and are symmetric in their frequency spacing relative to the central component. This latter type of variables are associated with their relatives among the fundamental pulsators, known as Blazhko variables. Their high frequency (≈20%) among the fundamental-mode variables versus the low occurrence rate of their first-overtone counterparts makes it more difficult to explain the Blazhko phenomenon by any theory depending mainly on the role of aspect angle or magnetic field. None of the current theoretical models are able to explain the observed close frequency components without invoking nonradial pulsation components in these stars.

Idioma originalEnglish
Páginas (desde-hasta)257-280
Número de páginas24
PublicaciónAstrophysical Journal
Volumen542
N.º1 PART 1
EstadoPublished - 10 oct 2000

Huella dactilar

massive compact halo objects
variable stars
frequency analysis
Magellanic clouds
indication
harmonics
stars
spacing
magnetic field
prewhitening
occurrences
frequency standards
project
rate
magnetic fields

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Citar esto

Alcock, C., Allsman, R., Alves, D. R., Axelrod, T., Becker, A., Bennett, D., ... Welch, D. L. (2000). The MACHO project Large Magellanic Cloud variable-star inventory. IX. Frequency analysis of the first-overtone RR Lyrae stars and the indication for nonradial pulsations. Astrophysical Journal, 542(1 PART 1), 257-280.
Alcock, C. ; Allsman, R. ; Alves, D. R. ; Axelrod, T. ; Becker, A. ; Bennett, D. ; Clement, C. ; Cook, K. H. ; Drake, A. ; Freeman, K. ; Geha, M. ; Griest, K. ; Kovács, G. ; Kurtz, D. W. ; Lehner, M. ; Marshall, S. ; Minniti, D. ; Nelson, C. ; Peterson, B. ; Popowski, P. ; Quinn, P. ; Rodgers, A. ; Rowe, J. ; Stubbs, C. ; Sutherland, W. ; Tomaney, A. ; Vandehei, T. ; Welch, D. L. / The MACHO project Large Magellanic Cloud variable-star inventory. IX. Frequency analysis of the first-overtone RR Lyrae stars and the indication for nonradial pulsations. En: Astrophysical Journal. 2000 ; Vol. 542, N.º 1 PART 1. pp. 257-280.
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title = "The MACHO project Large Magellanic Cloud variable-star inventory. IX. Frequency analysis of the first-overtone RR Lyrae stars and the indication for nonradial pulsations",
abstract = "More than 1300 variables classified provisionally as first-overtone RR Lyrae pulsators in the MACHO variable-star database of the Large Magellanic Cloud (LMC) have been subjected to standard frequency analysis. Based on the remnant power in the prewhitened spectra, we found 70{\%} of the total population to be monoperiodic. The remaining 30{\%} (411 stars) are classified as one of nine types according to their frequency spectra. Several types of RR Lyrae pulsational behavior are clearly identified here for the first time. Together with the earlier discovered double-mode (fundamental and first-overtone) variables, this study increased the number of known double-mode stars in the LMC to 181. During the total 6.5 yr time span of the data, 10{\%} of the stars showed strong period changes. The size, and in general also the patterns of the period changes, exclude a simple evolutionary explanation. We also discovered two additional types of multifrequency pulsators with low occurrence rates of 2{\%} for each. In the first type, there remains one closely spaced component after prewhitening by the main pulsation frequency. In the second type, the number of remnant components is two; they are also closely spaced, and are symmetric in their frequency spacing relative to the central component. This latter type of variables are associated with their relatives among the fundamental pulsators, known as Blazhko variables. Their high frequency (≈20{\%}) among the fundamental-mode variables versus the low occurrence rate of their first-overtone counterparts makes it more difficult to explain the Blazhko phenomenon by any theory depending mainly on the role of aspect angle or magnetic field. None of the current theoretical models are able to explain the observed close frequency components without invoking nonradial pulsation components in these stars.",
keywords = "Globular clusters: general, Magellanic clouds, Stars: horizontal-branch, Stars: oscillations, Stars: variables: other",
author = "C. Alcock and R. Allsman and Alves, {D. R.} and T. Axelrod and A. Becker and D. Bennett and C. Clement and Cook, {K. H.} and A. Drake and K. Freeman and M. Geha and K. Griest and G. Kov{\'a}cs and Kurtz, {D. W.} and M. Lehner and S. Marshall and D. Minniti and C. Nelson and B. Peterson and P. Popowski and P. Quinn and A. Rodgers and J. Rowe and C. Stubbs and W. Sutherland and A. Tomaney and T. Vandehei and Welch, {D. L.}",
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month = "10",
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Alcock, C, Allsman, R, Alves, DR, Axelrod, T, Becker, A, Bennett, D, Clement, C, Cook, KH, Drake, A, Freeman, K, Geha, M, Griest, K, Kovács, G, Kurtz, DW, Lehner, M, Marshall, S, Minniti, D, Nelson, C, Peterson, B, Popowski, P, Quinn, P, Rodgers, A, Rowe, J, Stubbs, C, Sutherland, W, Tomaney, A, Vandehei, T & Welch, DL 2000, 'The MACHO project Large Magellanic Cloud variable-star inventory. IX. Frequency analysis of the first-overtone RR Lyrae stars and the indication for nonradial pulsations', Astrophysical Journal, vol. 542, n.º 1 PART 1, pp. 257-280.

The MACHO project Large Magellanic Cloud variable-star inventory. IX. Frequency analysis of the first-overtone RR Lyrae stars and the indication for nonradial pulsations. / Alcock, C.; Allsman, R.; Alves, D. R.; Axelrod, T.; Becker, A.; Bennett, D.; Clement, C.; Cook, K. H.; Drake, A.; Freeman, K.; Geha, M.; Griest, K.; Kovács, G.; Kurtz, D. W.; Lehner, M.; Marshall, S.; Minniti, D.; Nelson, C.; Peterson, B.; Popowski, P.; Quinn, P.; Rodgers, A.; Rowe, J.; Stubbs, C.; Sutherland, W.; Tomaney, A.; Vandehei, T.; Welch, D. L.

En: Astrophysical Journal, Vol. 542, N.º 1 PART 1, 10.10.2000, p. 257-280.

Resultado de la investigación: Article

TY - JOUR

T1 - The MACHO project Large Magellanic Cloud variable-star inventory. IX. Frequency analysis of the first-overtone RR Lyrae stars and the indication for nonradial pulsations

AU - Alcock, C.

AU - Allsman, R.

AU - Alves, D. R.

AU - Axelrod, T.

AU - Becker, A.

AU - Bennett, D.

AU - Clement, C.

AU - Cook, K. H.

AU - Drake, A.

AU - Freeman, K.

AU - Geha, M.

AU - Griest, K.

AU - Kovács, G.

AU - Kurtz, D. W.

AU - Lehner, M.

AU - Marshall, S.

AU - Minniti, D.

AU - Nelson, C.

AU - Peterson, B.

AU - Popowski, P.

AU - Quinn, P.

AU - Rodgers, A.

AU - Rowe, J.

AU - Stubbs, C.

AU - Sutherland, W.

AU - Tomaney, A.

AU - Vandehei, T.

AU - Welch, D. L.

PY - 2000/10/10

Y1 - 2000/10/10

N2 - More than 1300 variables classified provisionally as first-overtone RR Lyrae pulsators in the MACHO variable-star database of the Large Magellanic Cloud (LMC) have been subjected to standard frequency analysis. Based on the remnant power in the prewhitened spectra, we found 70% of the total population to be monoperiodic. The remaining 30% (411 stars) are classified as one of nine types according to their frequency spectra. Several types of RR Lyrae pulsational behavior are clearly identified here for the first time. Together with the earlier discovered double-mode (fundamental and first-overtone) variables, this study increased the number of known double-mode stars in the LMC to 181. During the total 6.5 yr time span of the data, 10% of the stars showed strong period changes. The size, and in general also the patterns of the period changes, exclude a simple evolutionary explanation. We also discovered two additional types of multifrequency pulsators with low occurrence rates of 2% for each. In the first type, there remains one closely spaced component after prewhitening by the main pulsation frequency. In the second type, the number of remnant components is two; they are also closely spaced, and are symmetric in their frequency spacing relative to the central component. This latter type of variables are associated with their relatives among the fundamental pulsators, known as Blazhko variables. Their high frequency (≈20%) among the fundamental-mode variables versus the low occurrence rate of their first-overtone counterparts makes it more difficult to explain the Blazhko phenomenon by any theory depending mainly on the role of aspect angle or magnetic field. None of the current theoretical models are able to explain the observed close frequency components without invoking nonradial pulsation components in these stars.

AB - More than 1300 variables classified provisionally as first-overtone RR Lyrae pulsators in the MACHO variable-star database of the Large Magellanic Cloud (LMC) have been subjected to standard frequency analysis. Based on the remnant power in the prewhitened spectra, we found 70% of the total population to be monoperiodic. The remaining 30% (411 stars) are classified as one of nine types according to their frequency spectra. Several types of RR Lyrae pulsational behavior are clearly identified here for the first time. Together with the earlier discovered double-mode (fundamental and first-overtone) variables, this study increased the number of known double-mode stars in the LMC to 181. During the total 6.5 yr time span of the data, 10% of the stars showed strong period changes. The size, and in general also the patterns of the period changes, exclude a simple evolutionary explanation. We also discovered two additional types of multifrequency pulsators with low occurrence rates of 2% for each. In the first type, there remains one closely spaced component after prewhitening by the main pulsation frequency. In the second type, the number of remnant components is two; they are also closely spaced, and are symmetric in their frequency spacing relative to the central component. This latter type of variables are associated with their relatives among the fundamental pulsators, known as Blazhko variables. Their high frequency (≈20%) among the fundamental-mode variables versus the low occurrence rate of their first-overtone counterparts makes it more difficult to explain the Blazhko phenomenon by any theory depending mainly on the role of aspect angle or magnetic field. None of the current theoretical models are able to explain the observed close frequency components without invoking nonradial pulsation components in these stars.

KW - Globular clusters: general

KW - Magellanic clouds

KW - Stars: horizontal-branch

KW - Stars: oscillations

KW - Stars: variables: other

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M3 - Article

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VL - 542

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JF - Astrophysical Journal

SN - 0004-637X

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