A&A 480, 187-191 (2008)
The pulsating Bootis star 15 Andromedae: results from a three-site photometry campaignT. N. Dorokhova1, G. Handler2, N. I. Dorokhov1, E. Rodriguez3, and S. N. Udovichenko1
1 Astronomical Observatory of Odessa National University, Marazlievskaya 1v, 65014 Odessa, Ukraine
2 Institut für Astronomie, Universität Wien, Türkenschanzstrasse 17, 1180 Wien, Austria
3 Instituto de Astrofisica de Andalucia, C.S.I.C., Apdo. 3004, 18080 Granada, Spain
(Received 27 September 2007 / Accepted 29 November 2007)
Context.The Bootis stars are a chemically peculiar subgroup of main sequence A/F stars. Several of these fall into the instability strip of the Scuti stars and the whole spectroscopic group shows a high incidence of pulsational variability.
Aims.We investigated the pulsational behaviour of the Bootis star 15 And (HD 221756) to determine as many intrinsic mode frequencies as possible for asteroseismic applications.
Methods.The star was included as a secondary target for three telescopes during a campaign devoted to the Cep stars 12 and 16 Lac, due to its proximity to these targets. 302.8 h of time-resolved photometry spanning 161.2 d were acquired and analyzed.
Results.Our frequency analysis revealed f1 = 24.7887(2) c/d as the main pulsation frequency, with an amplitude of only 1.9(1) mmag. The residual periodogram suggests the presence of additional frequencies in an interval from 20 to 25 c/d, with very low amplitudes. We succeeded in detecting a second frequency f2 = 22.2580(9) with an amplitude of 0.6(1) mmag. Low-frequency light variations of the comparison star HD 220575 were revealed as well.
Conclusions.The pulsational behaviour of 15 And as a typical Boo-type star is compared with that of Scuti stars with normal abundances and with metallic-line Scuti stars. We discuss the value of Boo stars in understanding accretion and mixing in pulsating stars. The difficulties in the selection of reliable comparison stars for such high-precision research are pointed out.
Key words: stars: chemically peculiar -- stars: individual: HD 221756 -- stars: individual: HD 220575 -- stars: oscillations -- stars: variables: Scuti
© ESO 2008