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Titolo:
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
Autore:
Alcock, C; Allsman, R; Alves, DR; Axelrod, T; Becker, A; Bennett, D; Clement, C; Cook, KH; Drake, A; Freeman, K; Geha, M; Griest, K; Kovacs, G; Kurtz, DW; Lehner, M; Marshall, S; Minniti, D; Nelson, C; Peterson, B; Popowski, P; Pratt, M; Quinn, P; Rodgers, A; Rowe, J; Stubbs, C; Sutherland, W; Tomaney, A; Vandehei, T; Welch, DL;
Indirizzi:
Univ Calif Lawrence Livermore Natl Lab, Inst Geophys & Planetary Phys, Livermore, CA 94550 USA Univ Calif Lawrence Livermore Natl Lab Livermore CA USA 94550 A 94550 USA Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston Creek, ACT0200, Australia Australian Natl Univ Weston Creek ACT Australia 0200 , ACT0200, Australia Space Telescope Sci Inst, Baltimore, MD 21218 USA Space Telescope Sci Inst Baltimore MD USA 21218 , Baltimore, MD 21218 USA Univ Washington, Dept Astron, Seattle, WA 98195 USA Univ Washington Seattle WA USA 98195 , Dept Astron, Seattle, WA 98195 USA Univ Notre Dame, Dept Phys, Notre Dame, IN 46556 USA Univ Notre Dame Notre Dame IN USA 46556 pt Phys, Notre Dame, IN 46556 USA Univ Toronto, Dept Astron, Toronto, ON M5S 3H8, Canada Univ Toronto Toronto ON Canada M5S 3H8 stron, Toronto, ON M5S 3H8, Canada Univ Calif San Diego, Dept Phys, La Jolla, CA 92093 USA Univ Calif San Diego La Jolla CA USA 92093 t Phys, La Jolla, CA 92093 USA Konkoly Observ Budapest, H-1525 Budapest, Hungary Konkoly Observ BudapestBudapest Hungary H-1525 H-1525 Budapest, Hungary Univ Cape Town, Dept Astron, ZA-7701 Rondebosch, South Africa Univ Cape Town Rondebosch South Africa ZA-7701 Rondebosch, South Africa Univ Sheffield, Dept Phys, Sheffield S3 7RH, S Yorkshire, England Univ Sheffield Sheffield S Yorkshire England S3 7RH S Yorkshire, England Catholic Univ, Dept Astron, Santiago, Chile Catholic Univ Santiago Chile atholic Univ, Dept Astron, Santiago, Chile Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA Univ Calif Berkeley Berkeley CA USA 94720 pt Phys, Berkeley, CA 94720 USA European So Observ, D-85748 Garching, Germany European So Observ Garching Germany D-85748 v, D-85748 Garching, Germany Univ Oxford, Dept Phys, Oxford OX1 3RH, England Univ Oxford Oxford England OX1 3RH d, Dept Phys, Oxford OX1 3RH, England McMaster Univ, Dept Phys & Astron, Hamilton, ON L82 4M1, Canada McMaster Univ Hamilton ON Canada L82 4M1 on, Hamilton, ON L82 4M1, Canada
Titolo Testata:
ASTROPHYSICAL JOURNAL
fascicolo: 1, volume: 542, anno: 2000,
parte:, 1
pagine: 257 - 280
SICI:
0004-637X(20001010)542:1<257:TMPLMC>2.0.ZU;2-F
Fonte:
ISI
Lingua:
ENG
Soggetto:
GLOBULAR-CLUSTERS; PERIOD CHANGES; PHOTOMETRY; MODES; AGE; M15;
Keywords:
globular clusters : general; Magellanic Clouds; stars : horizontal-branch; stars : oscillations; stars : variables : other;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
34
Recensione:
Indirizzi per estratti:
Indirizzo: Alcock, C Univ Calif Lawrence Livermore Natl Lab, Inst Geophys & PlanetaryPhys, Livermore, CA 94550 USA Univ Calif Lawrence Livermore Natl Lab Livermore CA USA 94550 A
Citazione:
C. Alcock et al., "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", ASTROPHYS J, 542(1), 2000, pp. 257-280

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 oneof 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 (approximate to 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 held. None of the current theoretical models are able to explain the observed close frequency components without invoking nonradial pulsation components in these stars.
ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 21/05/13 alle ore 21:36:11