Pulsation in the atmosphere of the roAp star HD 24712: I. Spectroscopic observations and radial velocity measurements

Pulsation in the atmosphere of the roAp star HD 24712 : I. Spectroscopic observations and radial velocity measurements

Aims.We have investigated the structure of the pulsating atmosphere of one of the best studied rapidly oscillating Ap stars, HD 24712.Methods.For this purpose we analyzed spectra collected during 2001-2004. An extensive data set was obtained in 2004 simultaneously with the photometry of the Canadian MOST mini-satellite. This allows us to connect directly atmospheric dynamics observed as radial velocity variations with light variations seen in photometry. Results.We directly derived for the first time and for different chemical elements, respectively ions, phase shifts between photometric and radial velocity pulsation maxima indicating, as we suggest, different line formation depths in the atmosphere. This allowed us to estimate for the first time the propagation velocity of a pulsation wave in the outer stellar atmosphere of a roAp star to be slightly lower than the sound speed. We confirm large pulsation amplitudes (150-400 m s-1) for REE lines and the H core, while spectral lines of the other elements (Mg, Si, Ca, and Fe-peak elements) have nearly constant velocities. We did not find different pulsation amplitudes and phases for the lines of rare-earth elements before and after the Balmer jump, which supports the hypothesis of REE concentration in the upper atmosphere above the hydrogen line-forming layers. We also discuss radial velocity amplitudes and phases measured for individual spectral lines as tools for a 3D tomography of the atmosphere of HD 24712.

NATURVETENSKAP Fysik Astronomi, astrofysik och kosmologi hsv//swe
NATURAL SCIENCES Physical Sciences Astronomy, Astrophysics and Cosmology hsv//eng
stars: atmospheres
stars: chemically peculiar
stars: individual: HD 24712
stars: magnetic fields
stars: oscillations
Astronomy and astrophysics
Astronomi och astrofysik

Sachkov, M. (author)
Weiss, W.W. (author)
Kallinger, T. (author)
Kochukhov, OlegUppsala universitet,Institutionen för astronomi och rymdfysik(Swepub:uu)oko28508 (author)
Bagnulo, S. (author)
Ilyin, I. (author)
Landstreet, J.D. (author)
Leone, F. (author)
Lo Curto, G.Uppsala universitet,Institutionen för astronomi och rymdfysik (author)
Luftinger, T. (author)
Lyashko, D. (author)
Magazzu, A. (author)
Uppsala universitetInstitutionen för astronomi och rymdfysik (creator_code:org_t)

In:Astronomy and Astrophysics: EDP Sciences462:3, s. 1103-11120004-63611432-0746

By the author/editor: Ryabchikova, T.; Sachkov, M.; Weiss, W.W.; Kallinger, T.; Kochukhov, Oleg; Bagnulo, S.; show more...; Ilyin, I.; Landstreet, J.D.; Leone, F.; Lo Curto, G.; Luftinger, T.; Lyashko, D.; Magazzu, A.; show less...

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NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Astronomy Astrop ...

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