Category Archives: Publications

Potassium detected on exoplanet atmosphere

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.

Artist’s impression of a hot Jupiter (right) and its cool host star. Credit: AIP/Kristin Riebe.

Read more: Keles et al. 2019, MNRAS, 489, L37

AIP press release
LBT press release

First ZDI with PEPSI

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.

Temperature map from four different viewing angles.

Magnetic field map from four different viewing angles.

Read more: Strassmeier, Carroll & Ilyin 2019 A&A, 625, 27 

AIP press release
LBT press release

 

 

Revised carbon 12C/13C isotope ratio of α Aurigae

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.

The spectrum synthesis fitting.

Read more: Sablowski et al. 2019 A&A, 622, L11

 

 

EK Draconis showing evidence for starspot penumbrae

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.

Left: Temperature Doppler image of EK Draconis. Right: iMap reconstruction of the spot that indicates evidence for penumbra.

Read more: Järvinen et al. 2018, A&A, 620, 162

 

KELT-9 b optical Mg I triplet detected

PEPSI has detected the optical Mg I triplet at 7.8-sigma in the extended atmosphere of the ultra-hot Jupiter KELT-9 b. Constraints are placed on the density and radial extent of the excited hydrogen envelope.

Average line profiles for the Mg triplet lines of the Kelt-9 b atmosphere.
Average line profiles for the Mg triplet lines of the Kelt-9 b atmosphere. ST is the ratio stellar spectrum in transit divided by stellar spectrum out of transit. Possible contaminating atomic transitions are marked with vertical red lines. Spectral resolution R is 50,000.

 

Read more: Cauley et al., 2019, AJ 157, 69

Kelt-21b: A hot Jupiter transiting the rapidly-rotating metal-poor late-A primary of a likely hierarchical triple system

Detection of the line profile perturbations confirmed that the planet candidate Kelt-21b does indeed transit its rapidly rotating host star. Furthermore, the motion of the line profile perturbation across the line profile during the transit diagnosted the spin-orbit misalignment, which is the angle between the stellar spin and planetary orbital angular momentum vectors projected onto the plane of the sky.

Kelt-21b
The Doppler tomographic PEPSI data for KELT-21. Time is from bottom up. Vertical lines mark the center of the line profile at v=0 and the edges at v = v sin i, a horizontal line shows the time of mid-transit, and the four small crosses depict the times of first through fourth contacts.

 

Read more: Johnson et al. 2018, AJ, 2018, 155, 100

Posters presented at the 2nd LBT users meeting in Florence on June 20-23, 2017.