Hydrodynamical simulations of convection-related stellar micro-variability

Summary, in English

We used a series of CO⁵BOLD hydrodynamical model atmospheres covering stellar objects from white dwarfs to red giants to derive theoretical estimates of the photometric and photocentric stellar variability in wavelength-integrated light across the Hertzsprung-Russell diagram. We validated our models against solar measurements from the SoHO/VIRGO instrument. Within our set of models we find a systematic increase of the photometric as well as photocentric variability - which turn out to be closely connected - with decreasing surface gravity. The estimated absolute levels of the photocentric variability do not affect astrometric observations on a precision level expected to be achieved by the GAIA mission - with the exception of close-by giants. The case of supergiants remains to be investigated. In view of the ongoing debate about the photometric non-detection of p-modes in Procyon by the Canadian MOST satellite we remark that we obtain a factor of approximately equals 3 in amplitude between the granular background "noise" in the Sun and Procyon. This statement refers to a particular representation of temporal power spectra as discussed in Sect. 5.

• Författare: Fredrik Svensson; Hans-Günter Ludwig
• Avdelning/ar: Astronomi - Genomgår omorganisation
• Publiceringsår: 2005
• Språk: Engelska
• Sidor: 979-984
• Publikation/Tidskrift/Serie: European Space Agency, (Special Publication) ESA SP
• Volym: 560
• Länkar: http://front.math.ucdavis.edu/0409.1714
• Dokumenttyp: Konferensbidrag
• Förlag: European Space Agency
• Ämne: Astronomy, Astrophysics and Cosmology
• Nyckelord: Exoplanets; Granulations; Variability; Astrometry
• Conference name: 13th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun
• Conference date: 2004-07-05 - 2004-07-09
• Conference place: Hamburg, Germany
• Status: Published
• ISBN/ISSN/Övrigt: ISSN: 1609-042X; ISSN: 0379-6566; CODEN: ESPUD4