Read more: Woodward et al., 2020, AJ, 159, 231
Read more: Woodward et al., 2020, AJ, 159, 231
January 2019 featured a total lunar eclipse. The Moon dimmed by a factor of 20,000 (10.75 mag) during totality. Therefore, the light gathering capability of the 11.8 m Large Binocular Telescope (LBT) in Arizona was needed for the observations. Additionally, the high spectral resolution of the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) was necessary to separate the expected tiny spectral-line absorptions of the Earth’s atmosphere from the normal solar spectrum at unprecedented spectral resolution and in polarized light. The radial velocities trace a wavelength dependent Rossiter-McLaughlin effect of the Earth eclipsing the Sun as seen from the Tycho crater confirming earlier observations. No line polarization of any spectral-line feature is detected outside nor inside eclipse. This places an upper limit of ≈0.2% on the degree of line polarization during transmission through Earth’s atmosphere and magnetosphere.
Read more: Strassmeier et al., 2020, A&A, 635, 156
LBT/PEPSI spectropolarimetry tested the hypothesis that the surface magnetic morphology is a crucial component for the spin down of stars. Solar-type stars are born with relatively rapid rotation and strong magnetic fields. Through a process known as magnetic braking, the rotation slows over time as stellar winds gradually remove angular momentum from the system. The rate of angular momentum loss depends sensitively on the magnetic morphology, with the dipole field exerting the largest torque on the star. One hypothesis to explain this reduction in efficiency is a shift in magnetic morphology from predominantly larger to smaller spatial scales. We tested this hypothesis with spectropolarimetric measurements of two stars that sample chromospheric activity levels on opposite sides of the proposed magnetic transition. As predicted, the more active star (HD 100180) exhibits a significant circular polarization signature due to a non-axisymmetric large-scale magnetic field, while the less active star (HD 143761) shows no significant signal.
Read more: Metcalfe et al. 2019, ApJ Letters, 887, 38
We investigated the potassium excess absorption around 7699 Å of the exoplanets HD189733b and HD209458b using high-spectral resolution transit observations acquired with the 2 × 8.4 m Large Binocular Telescope (LBT) and the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI). For a bandwidth of 0.8 Å, we present a detection >7σ with an absorption level of 0.18 per cent for HD189733b. Applying the same analysis to HD209458b, we can set 3σ upper limit of 0.09 per cent, even though a K-excess absorption was not detected. The investigation suggests that the K feature is less present in the atmosphere of HD209458b than in the one of HD189733b and confirms previous claims that the atmospheres of these two planets must have fundamentally different properties.
Read more: Keles et al. 2019, MNRAS, 489, L37
We present a temperature and a magnetic-field surface map of the K2 subgiant of the active binary II Peg. Employed are high resolution Stokes IV spectra obtained with the new Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT). Our main result is that the temperature features on II Peg closely correlate with its magnetic field topology. We find a warm spot (350K warmer with respect to the effective temperature) of positive polarity and radial field density of 1.1 kG coexisting with a cool spot (780K cooler) of negative polarity of 2 kG.
Read more: Strassmeier, Carroll & Ilyin 2019 A&A, 625, 27
The 33 meters long (in A0 format) spectrum of epsilon Eridani is available for download. See the Wallposters section among the Library links. Note that the whole spectrum is in two PDF files, each having a size of almost 18 MB.
The new measure of the carbon 12C/13C isotope ratio of the primary component of Capella, 17.8 ± 1.9, using high-resolution R ≈ 250 000 spectra obtained with PEPSI at both the Vatican Advanced Technology Telescope (VATT) and the Large Binocular Telescope (LBT) is significantly lower than the previous value of 27 ± 4 but now agrees better with the recent model prediction of 18.8-20.7.
Read more: Sablowski et al. 2019 A&A, 622, L11
The first temperature surface map of EK Dra from very-high-resolution spectra obtained with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope shows four cool spots. The temperature morphology of one of them appears to show so far the best evidence for the existence of a solar-like penumbra for a starspot.
Read more: Järvinen et al. 2018, A&A, 620, 162