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A Survey for Pulsating Ap Stars from Naini Tal

Published online by Cambridge University Press:  12 April 2016

Peter Martinez ,
D. W. Kurtz ,
U. S. Chaubey ,
S. K. Gupta ,
S. Joshi ,
R. Sagar ,
B. N. Ashoka  and
S. Seetha
Peter Martinez
Affiliation:
SAAO, P.O. Box 9, Observatory 7935, South Africa
D. W. Kurtz
Affiliation:
Department of Astronomy, University of Cape Town, Rondebosch 7701, South Africa
U. S. Chaubey
Affiliation:
Uttar Pradesh State Observatory, Manora Peak, Naini Tal 263 129, India
S. K. Gupta
Affiliation:
Uttar Pradesh State Observatory, Manora Peak, Naini Tal 263 129, India
S. Joshi
Affiliation:
Uttar Pradesh State Observatory, Manora Peak, Naini Tal 263 129, India
R. Sagar
Affiliation:
Uttar Pradesh State Observatory, Manora Peak, Naini Tal 263 129, India
B. N. Ashoka
Affiliation:
Technical Physics Division, ISRO Satellite Centre, Vimanapura PO, Airport Rd, Bangalore 560 017, India
S. Seetha
Affiliation:
Technical Physics Division, ISRO Satellite Centre, Vimanapura PO, Airport Rd, Bangalore 560 017, India

Extract

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Pulsation is ubiquitous among chemically normal A-type stars, but comparatively rare among chemically peculiar Am and Ap stars of the same temperature range. The conventional explanation for this is that diffusion produces the surface abundance anomalies in the Am and Ap stars, and also drains He from the He-II ionisation zone, thus quenching the κ-mechanism that drives δ Scuti pulsation. The pulsating Am and Ap stars exhibit dichotomous pulsation characteristics. The Am stars (and related stars) exhibit low-overtone δ Scuti pulsation, with amplitudes ranging from a few mmag to 0.1 mag. The pulsating Ap stars exhibit high-overtone pulsation with periods in the range 6-16 min and Johnson B semi-amplitudes typically ≤ 5 mmag. These stars are referred to as rapidly oscillating Ap stars, or ‘roAp’ stars (the see review by Martinez & Kurtz 1995).

Type
Part 6. Variables Close to the Main Sequence
Information
International Astronomical Union Colloquium , Volume 176: The Impact of Large-Scale Surveys on Pulsating Star Research , 2000 , pp. 485 - 486
Copyright
Copyright © Astronomical Society of the Pacific 2000

References

Martinez, P. & Kurtz, D.W. 1995, Ap&SS, 230, 29 Google Scholar
Martinez, P., Ashoka, B.N., Kurtz, D.W., Gupta, S.K., & Chaubey, U.S. 1999a, Inf. Bull. Var. Stars, No. 4677 Google Scholar
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Renson, P., Gerbaldi, M., & Catalano, F.A. 1991, A&AS, 89, 429 Google Scholar