Discovery of very low amplitude 9-minute multiperiodic pulsations in the magnetic Ap star HD75445
2009 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 493, no 3, L45-L48 p.Article in journal (Refereed) Published
We present our discovery of pulsational radial-velocity variations in the cool Ap star HD75445, an object spectroscopically similar to the bright, rapidly-oscillating Ap (roAp) star gamma 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 20-30 m s(-1). Substantial variation in 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 HD75445 indicates that the roAp excitation mechanism produces variability in the radial velocity amplitude of between a few tens ms(-1) and several km s(-1). This supports the idea that many, if not all, cool Ap stars occupying the roAp instability strip may harbour non-radial pulsations, which currently remain undetected due to their small photometric and radial-velocity amplitudes.
Place, publisher, year, edition, pages
2009. Vol. 493, no 3, L45-L48 p.
stars: atmospheres, stars: chemically peculiar, stars: oscillations, stars: individual: HD75445
IdentifiersURN: urn:nbn:se:uu:diva-137351DOI: 10.1051/0004-6361:200811419ISI: 000262641100002OAI: oai:DiVA.org:uu-137351DiVA: diva2:378214