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Shape of a slowly rotating star measured by asteroseismology
- Source :
- Science Advances 16 Nov 2016, Vol. 2, no. 11, e1601777
- Publication Year :
- 2016
-
Abstract
- Stars are not perfectly spherically symmetric. They are deformed by rotation and magnetic fields. Until now, the study of stellar shapes has only been possible with optical interferometry for a few of the fastest-rotating nearby stars. We report an asteroseismic measurement, with much better precision than interferometry, of the asphericity of an A-type star with a rotation period of 100 days. Using the fact that different modes of oscillation probe different stellar latitudes, we infer a tiny but significant flattening of the star's shape of $\Delta R/R = (1.8 \pm 0.6) \times 10^{-6}$. For a stellar radius $R$ that is $2.24$ times the solar radius, the difference in radius between the equator and the poles is $\Delta R = 3 \pm 1$ km. Because the observed $\Delta R/R$ is only one-third of the expected rotational oblateness, we conjecture the presence of a weak magnetic field on a star that does not have an extended convective envelope. This calls to question the origin of the magnetic field.<br />Comment: 15 pages, 2 tables, 3 figures
- Subjects :
- Astrophysics - Solar and Stellar Astrophysics
Subjects
Details
- Database :
- arXiv
- Journal :
- Science Advances 16 Nov 2016, Vol. 2, no. 11, e1601777
- Publication Type :
- Report
- Accession number :
- edsarx.1611.06435
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.1126/sciadv.1601777