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Sun-as-a-Star Spectroscopic Observations of the 2017 August 21 Solar Eclipse

The solar eclipse of 2017 August 21 was observed with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) on the Large Binocular Telescope (LBT), which is located at Mt. Graham International Observatory (MGIO), Arizona, USA. At this location, a partial eclipse was observed with maximum obscuration of 61.6%. The 11-millimeter-aperture, binocular Solar Disk-Integrated (SDI) telescope, located on the kitchen balcony of the LBT building, feeds sunlight to PEPSI, which has recorded a total of 116 Sun-as-a-star spectra in the wavelength range of 5300 – 6300 Å, with a spectral resolution R=250,000 and S/N of about 733:1. The temporal evolution of the Fraunhofer Na I D doublet at 5890/5896 Å is analyzed using contrast profiles that illustrate subtle changes in the spectral line, not obvious in the intensity profiles.

Time-series of the radial velocity obtained from the Na D2 (blue) and Na D1 (red) lines observed during solar eclipse. The vertical lines indicate the time of maximum obscuration. The line-core velocities (top-left) are computed from a parabola fit to the line core, whereas the line-wing velocities reflect bisector velocities at certain distances from the line core, which are given in milli-Ångstrom in the lower-right corner of each panel. The relative formation heights are given in the corresponding color in the lower-left corner of each panel.

Read more: Dineva et al., 2024, Sol. Phys. 299, 123