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Whole Earth Telescope discovery of a strongly distorted quadrupole pulsation in the largest amplitude rapidly oscillating Ap star

L. Holdsworth, Daniel; W. Kurtz, Donald; Saio, Hideyuki; L. Provencal, Judith; Letarte, Bruno; Sefako, Ramotholo; Petit, Véronique; Smalley, Barry; Thomsen, Hunter; L. Fletcher, Corinne

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Authors

Daniel L. Holdsworth

Donald W. Kurtz

Hideyuki Saio

Judith L. Provencal

Bruno Letarte

Ramotholo Sefako

Véronique Petit

Hunter Thomsen

Corinne L. Fletcher



Abstract

We present a new analysis of the rapidly oscillating Ap (roAp) star, 2MASS J19400781 - 4420093 (J1940; V = 13.1). The star was discovered using SuperWASP broadband photometry to have a frequency of 176.39 d-1 (2041.55 µHz; P = 8.2 min; (Holdsworth et al. 2014a) and is shown here to have a peak-to-peak amplitude of 34 mmag. J1940 has been observed during three seasons at the South African Astronomical Observatory, and has been the target of a Whole Earth Telescope campaign. The observations reveal that J1940 pulsates in a distorted quadrupole mode with unusual pulsational phase variations. A higher signal-to-noise ratio spectrum has been obtained since J1940’s first announcement, which allows us to classify the star as A7 Vp Eu(Cr). The observing campaigns presented here reveal no pulsations other than the initially detected frequency. We model the pulsation in J1940 and conclude that the pulsation is distorted by a magnetic field of strength 1.5 kG. A difference in the times of rotational maximum light and pulsation maximum suggests a significant offset between the spots and pulsation axis, as can be seen in roAp stars.

Citation

L. Holdsworth, D., W. Kurtz, D., Saio, H., L. Provencal, J., Letarte, B., Sefako, R., …L. Fletcher, C. (2018). Whole Earth Telescope discovery of a strongly distorted quadrupole pulsation in the largest amplitude rapidly oscillating Ap star. Monthly Notices of the Royal Astronomical Society, 473(1), 91-104. https://doi.org/10.1093/mnras/stx2401

Journal Article Type Article
Acceptance Date Sep 13, 2017
Online Publication Date Sep 16, 2017
Publication Date Jan 1, 2018
Publicly Available Date May 26, 2023
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 473
Issue 1
Pages 91-104
DOI https://doi.org/10.1093/mnras/stx2401
Keywords asteroseismology, stars, chemically peculiar, magnetic field, oscillations, individual, J1940, techniques, photometric
Publisher URL http://doi.org/10.1093/mnras/stx2401

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