Doyle, Amanda (2015) Spectral analyses of solar-like stars. Doctoral thesis, Keele University.
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Accurate stellar parameters are important not just to understand the stars themselves, but also for understanding the planets that orbit them. Despite the availability of high quality spectra, there are still many uncertainties in stellar spectroscopy. In this thesis, the finer details of spectroscopic analyses are discussed and critically evaluated, with a focus on improving the stellar parameters.
Using high resolution, high signal-to-noise HARPS spectra, accurate parameters were determined for 22 WASP stars. It is shown that there is a limit to the accuracy of stellar parameters that can be achieved, despite using high S/N spectra. It is also found that the selection of spectral lines used and the accuracy of atomic data is crucial, and different line lists can result in different values of parameters.
Different spectral analysis methods often give vastly different results even for the same spectrum of the same star. Here it is shown that many of these discrepancies can be explained by the choice of lines used and by the various assumptions made. This will enable a more reliable homogeneous study of solar-like stars in the future.
The Rossiter-McLaughlin effect observed for transiting exoplanets often requires prior knowledge of the projected rotational velocity (v sin i). This is usually provided via spectroscopy, however this method has uncertainties as spectral lines are also broadened by photospheric velocity fields known as “macroturbulence” (vmac). Using rotational splitting frequencies for 28 Kepler stars that were provided via asteroseismology, accurate v sin i values have been determined.
By inferring the vmac for 28 Kepler stars, it was possible to obtain a new calibration between vmac, effective temperature and surface gravity. Therefore macroturbulence, and thus v sin i, can now be determined with confidence for stars that do not have asteroseismic data available. New spectroscopic vsini values were then determined for the WASP planet host stars.
|Item Type:||Thesis (Doctoral)|
|Subjects:||Q Science > QB Astronomy|
|Divisions:||Faculty of Natural Sciences > School of Physical and Geographical Sciences|
|Depositing User:||Michael Debenham|
|Date Deposited:||29 Jul 2015 12:43|
|Last Modified:||29 Jul 2015 12:43|
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