Doppler imaging of stellar surface structure - XV. A possible detection ofdifferential rotation and local meridional flows on the rapidly-rotating giant HD 218153 = KU Pegasi

Citation
M. Weber et Kg. Strassmeier, Doppler imaging of stellar surface structure - XV. A possible detection ofdifferential rotation and local meridional flows on the rapidly-rotating giant HD 218153 = KU Pegasi, ASTRON ASTR, 373(3), 2001, pp. 974-986
Citations number
48
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
ASTRONOMY & ASTROPHYSICS
ISSN journal
1432-0746 → ACNP
Volume
373
Issue
3
Year of publication
2001
Pages
974 - 986
Database
ISI
SICI code
1432-0746(200107)373:3<974:DIOSSS>2.0.ZU;2-B
Abstract
Time-resolved Doppler images of the rapidly rotating, but long-period (25 d ays), giant KU Pegasi show several cool low-to-medium latitude spots as wel l as an asymmetric polar feature. The average spot temperature is about 700 K below the photospheric temperature of 4700 K. KU Peg is one of the most massive, and currently the most evolved, late-type star with a Doppler imag e. We obtained two independent images from two consecutive stellar rotation s covering 50 nights with a total of 43 spectra. From a cross-correlation a nalysis of the two maps, we detect systematic longitudinal and latitudinal shifts that we tentatively interpret as latitude-dependent differential rot ation and local meridional flows, respectively. The differential-rotation p attern is more complex than on the Sun, but on average in the sense that th e poles rotate slower than the stellar equator, i.e. in the same direction and also of the same order than on the Sun. The latitudinal shifts are of t he order of 0.4 degrees day(-1) towards the stellar pole and occur at longi tudes of around 40 degrees and 330 degrees. The residual H alpha profiles s how a stationary emission component at rest wavelength and a blue-shifted a bsorption. The latter suggests an outward pointed velocity field with a ow velocity of approximately 35 km s(-1).