The Institute for Astrophysics and Geophysics (IAG) in Göttingen operates a Fourier-Transform Spectrograph (FTS) that can be fed by either a 50cm siderostat or an integrating sphere. In 2016, we published a solar flux atlas (disk-integrated) at wavelengths 405-2300nm. Being largely comparable to the Kitt Peak spectral atlases in terms of resolution and signal-to-noise, our focus lies on an accurate calibration of frequencies (wavelengths) because we are interested in absolute convective blueshift of solar surface features.
Recently, we published an atlas of the quiet solar surface at different limb positions (spatially resolved Sun) and investigated convective velocities across the solar surface and in different spectral lines (Ellwarth et al., 2023 and in press). Furthermore, we studied the impact of centre-to-limb variation on exoplanet transit observations (Reiners et al., 2023). We are currently collecting data of active solar regions with the goal to measure convective blueshift as a function of limb position and magnetic field strength. In the talk, I will provide an overview of our program with a focus on the challenges we met in our attempts to determine Doppler velocities at the solar surface at m/s accuracy.

Zoom link: https://rediris.zoom.us/j/97531318437?pwd=TEpGZGVkNkpBcXBLWVlNTGt6bkdNU…
Meeting ID: 975 3131 8437

Passcode: 147922