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- Brown, A., et al.
(författare)
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Kepler Observations of Starspot Evolution, Differential Rotation, and Flares on Late-Type Stars
- 2011
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Ingår i: American Astronomical Society Meeting Abstracts #218.
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Konferensbidrag (refereegranskat)abstract
- The Kepler satellite is providing spectacular optical photometric light-curves of unprecedented precision and duration that routinely allow detailed studies of stellar magnetic activity on late-type stars that were difficult, if not impossible, to attempt previously. Rotational modulation due to starspots is commonly seen in the Kepler light-curves of late-type stars, allowing detailed study of the surface distribution of their photospheric magnetic activity. Kepler is providing multi-year duration light-curves that allow us to investigate how activity phenomena – such as the growth, migration, and decay of starspots, differential rotation, activity cycles, and flaring – operate on single and binary stars with a wide range of mass and convection zone depth. We present the first results from detailed starspot modeling using newly-developed light-curve inversion codes for a range of GALEX-selected stars with typical rotation periods of a few days, that we have observed as part of our 200 target Kepler Cycle 1/2 Guest Observer programs. The physical properties of the stars have been measured using high resolution optical spectroscopy, which allows the Kepler results to be placed within the existing framework of knowledge regarding stellar magnetic activity. These results demonstrate the powerful diagnostic capability provided by tracking starspot evolution essentially continuously for more than 16 months. The starspots are clearly sampling the stellar rotation rate at different latitudes, enabling us to measure the differential rotation and starspot lifetimes. As would be expected, stars with few day rotation show frequent flaring that is easily seen as ”white-light” flares in Kepler light-curves. We compare the observed flare rates and occurrence with the starspot properties. This work contains results obtained using the NASA Kepler satellite and from the Apache Point Observatory, the MMT (using NOAO community access time), and the Hobby-Eberly Telescope. Funding is provided by NASA Kepler grants NNX10AC51G and NNX11AC79G.
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2. |
- Morin, J., et al.
(författare)
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Multiple views of magnetism in cool stars
- 2013
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Ingår i: Astronomical Notes - Astronomische Nachrichten. - : Wiley. - 0004-6337 .- 1521-3994. ; 334:1-2, s. 48-52
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic fields are regarded as a crucial element for our understanding of stellar physics. They can be studied with a variety of methods which provide complementary - and sometimes contradictory - information about the structure, strength and dynamics of the magnetic field and its role in the evolution of stars. Stellar magnetic fields can be investigated either with direct methods based on the Zeeman effect or through the observation of activity phenomena resulting from the interaction of the field with the stellar atmosphere. In this Cool Stars 17 Splinter Session we discussed the results obtained by the many ongoing studies of stellar activity and direct studies of surface magnetic fields, as well as the state-of-the-art techniques on which they are based. We show the strengths and limitations of the various approaches currently used and point out their evolution as well as the interest of coupling various magnetism and activity proxies. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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