Iodine-Cell Spectroscopy Applied to Investigating the Solar Differential Rotation |
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Authors: | Y Takeda S Ueno |
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Institution: | 1.National Astronomical Observatory of Japan,Tokyo,Japan;2.Kwasan and Hida Observatories,Kyoto University,Takayama,Japan |
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Abstract: | In an attempt to examine whether the spectroscopic Doppler method with an iodine cell (which is known to be successful for
precise radial-velocity determinations in stellar astronomy) could be effective for investigating the solar differential rotation,
we carried out intensive observations to collect spectra at a large number of points on the solar disk by using the Domeless
Solar Telescope along with the horizontal spectrograph of the Hida Observatory. Having converted the resulting line-of-sight
velocity component into the angular rotational rate (ω), we derived a differential rotation law, wsidereal (deg day-1) = 14.03 (±0.06)-1.84 (±0.57) sin2y-1.92 (±0.85) sin4y\omega_{\mathrm{sidereal}} (\mathrm{deg}\,\mathrm{day}^{-1}) =14.03 (\pm0.06)-1.84 (\pm0.57) \sin^{2}\psi-1.92 (\pm0.85) \sin^{4}\psi (ψ: heliographic latitude), which is reasonably consistent with other spectroscopic determinations published so far. Our analysis
also revealed several practical points to note for successful application (e.g., exclusion of those data that are not well distant from the meridian; mutual data subtraction/averaging for symmetric counterparts
at the eastern and western hemisphere). Considering its easiness and cheapness, this iodine-cell-featured spectroscopic method
may be regarded as an effective and practical tool for studying the differential rotation of the Sun. |
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