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arXiv · 1411.1481

Solar rotation inferred from radial velocities of the sun-as-a-star during the 2012 May 21 eclipse

Yoichi Takeda·Osamu Ohshima·Eiji Kambe·Hiroyuki Toda·Hisashi Koyano·Bun'ei Sato·Yasuhisa Nakamura·Norio Narita·Takashi Sekii
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Abstract

With an aim to examine how much information of solar rotation can be obtained purely spectroscopically by observing the sun-as-a-star during the 2012 May 21 eclipse at Okayama Astrophysical Observatory, we studied the variation of radial velocities (V_r), which were derived by using the iodine-cell technique based on a set of 184 high-dispersion spectra consecutively obtained over the time span of ~4 hours. The resulting V_r(t) was confirmed to show the characteristic variation (Rossiter-McLaughlin effect) caused by time-varying visibility of the solar disk. By comparing the observed V_r(t) curve with the theoretical ones, which were simulated with the latitude (psi) dependent solar rotation law omega(psi) = A + B sin^2(psi) (deg/day), we found that the relation B = -5.5 A + 77 gives the best fit, though separate determinations of A and B were not possible. Since this relationship is consistent with the real values known for the sun (A = 14.5, B = -2.8), we may state that our analysis yielded satisfactory results. This consequence may provide a prospect of getting useful information on stellar rotation of eclipsing binaries from radial-velocity studies during eclipse, if many spectra of sufficiently high time-resolution are available.

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Yoichi Takeda, Osamu Ohshima, Eiji Kambe, Hiroyuki Toda, Hisashi Koyano, Bun'ei Sato, Yasuhisa Nakamura, Norio Narita, Takashi Sekii. 2014-11-06. Solar rotation inferred from radial velocities of the sun-as-a-star during the 2012 May 21 eclipse. https://doi.org/10.1093/pasj%2Fpsu139

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