Journal Article

On the spectroscopic nature of the cool evolved Am star HD 151878*

L. M. Freyhammer, V. G. Elkin and D. W. Kurtz

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 390, issue 1, pages 257-264
Published in print October 2008 | ISSN: 0035-8711
Published online October 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13726.x
On the spectroscopic nature of the cool evolved Am star HD 151878*

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Recently, Tiwari, Chaubey & Pandey detected the bright component of the visual binary HD 151878 to exhibit rapid photometric oscillations through a Johnson B filter with a period of 6 min (2.78 mHz) and a high, modulated amplitude up to 22 mmag peak-to-peak, making this star by far the highest amplitude rapidly oscillating Ap (roAp) star known. As a new roAp star, HD 151878 is of additional particular interest as a scarce example of the class in the northern sky, and only the second known case of an evolved roAp star – the other being HD 116114. We used the FIbre-fed Echelle Spectrograph at the Nordic Optical Telescope to obtain high time-resolution spectra at high dispersion to attempt to verify the rapid oscillations. We show here that the star at this epoch is spectroscopically stable to rapid oscillations of no more than a few tens of m s−1. The high-resolution spectra furthermore show the star to be of type Am rather than Ap and we show the star lacks most of the known characteristics for roAp stars. We conclude that this is an Am star that does not pulsate with a 6-min period. The original discovery of pulsation is likely to be an instrumental artefact.

Keywords: stars: oscillations; stars: variables: other; stars: individual: HD 151878; stars: magnetic field

Journal Article.  5877 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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