Summary: Astronomy & Astrophysics manuscript no. 11419 c ESO 2008
December 10, 2008
LETTER TO THE EDITOR
Discovery of very low amplitude 9-minute multiperiodic
pulsations in the magnetic Ap star HD 75445
O. Kochukhov1, S. Bagnulo2, and G. Lo Curto3
1
Department of Physics and Astronomy, Uppsala University, SE-751 20, Uppsala, Sweden
2
Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland, UK
3
European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Casilla 19001 Santiago 19, Chile
Received 25 November 2008 / Accepted 08 December 2008
ABSTRACT
We discovered pulsational radial velocity variations in the cool Ap star HD 75445 ­ an object spectroscopically very similar to
the bright rapidly oscillating Ap (roAp) star Equ. Based on high-resolution time-series spectroscopy obtained with the HARPS
spectrometer at the European Southern Observatory 3.6-m telescope, we detected oscillations in Nd II and Nd III lines with a period
close to 9 min and amplitudes of 20­30 m s-1
. Substantial variation of the pulsational amplitude during our 3.8 h observing run reveals
the presence of at least three excited non-radial modes. The detection of extremely low amplitude pulsations in HD 75445 indicates

Source: Armagh Observatory

Collections: Physics