Katja Poppenhaeger

The latest paper of my recently graduated PhD student Laura Ketzer is now in print – and as a side note, an all-female author list spanning two different research groups at the AIP: Three young planets around the K-dwarf K2-198: high-energy environment, evaporation history, and expected future Ketzer, L.; Poppenhaeger, K.; Baratella, M.; Ilin, E., Monthly Notices of the Royal Astronomical Society, Volume 527, Issue 1, pp.374-385 (2024) Planets orbiting young stars are thought to experience atmospheric evaporation as a…

Read More Read More

Two new papers that my group contributed to: a study of flares on the Sun, but with the Sun seen as a star, which provides a “translation table” between stellar and solar flare observations; and spectroscopic observation of the great dimming of Beutelgeuse, which happened in 220 and was observed (among others) with the AIP’s STELLA telescope on Tenerife. A comparative study of two X2.2 and X9.3 solar flares observed with HARPS-N. Reconciling Sun-as-a-star spectroscopy and high-spatial resolution solar observations…

Read More Read More

My group is contributing the the second-light instrument suite for the Extremely Large Telescope: we are developing and building the optical-ultraviolet (UBV) part of the high-resolution spectrograph ANDES. And of course, we are also highly interested in the scientific avenues that will open up with this instrument. The two recent White Papers on exoplanetary and stellar science with ANDES lay out many of the exciting ideas that we can explore: Ground-breaking Exoplanet Science with the ANDES spectrograph at the ELT…

Read More Read More

My PhD student Nikoleta Ilic has investigated a really interesting object, the close M dwarf / brown dwarf pair NLTT 41135, which forms a hierarchical wide triple system with the M dwarf NLTT 41136. Nikoleta found an elevated activity of about an order of magnitude in X-rays that is most likely caused by tidal interaction between the brown dwarf and the M dwarf. Nikoleta was able to quantify this with the help of other wide M dwarf systems from the…

Read More Read More

Laura Ketzer, one of my PhD students, recently published a detailed study on the fate of small exoplanets – super-Earths and mini-Neptunes – under different time evolutions of the magnetic activity of the host star. The so-called radius gap manisfests itself differently for stars that experience an early versus a late spin-down. Also in samples of mixed stellar spin-down histories the features of the gap as a whole change with age, so that uniform age samples, such as open stellar…

Read More Read More

My PhD student Nikoleta Ilic has published a project we have been working on for the past two years: the identification of tidal star-planet interaction in a sample of planet-hosting stars. The tidal interaction leads to a spin-up of the host stars, which we identified through comparisons with co-eval companion stars in wide orbits around the star-planet systems. The paper was also featured in a joint press release of the AIP and the Harvard-Smithsonian Center for Astrophysics: https://chandra.harvard.edu/press/22_releases/press_110222.html Ilic, N….

Read More Read More

The second paper of the PEPSI Exoplanet Transit Survey (PETS) performs a search for possible atomic and molecular species that may drive the thermal inversion in the atmospheres of ultrahot Jupiters, and it rules out several species in the case of KELT-20 b/MASCARA-2 b: Title: “The PEPSI-LBT Exoplanet Transit Survey (PETS). II. A Deep Search for Thermal Inversion Agents in KELT-20 b/MASCARA-2 b with Emission and Transmission Spectroscopy” Johnson, Marshall C.; Wang, Ji; Pai Asnodkar, Anusha; Bonomo, Aldo S.; Gaudi,…

Read More Read More

One possible manifestation of (magnetic) star-planet interactions is flare triggering by a planet passing by some active region of the star and disturbing the magnetic field structure of the active region enough that a flare is triggered earlier than it usually would have occurred. My PhD student Ekaterina Ilin recently studied the many TESS-observed flares of the young planet-hosting star AU Mic to test whether there is any significant correlation of flare timing with the orbit of the exoplanet or…

Read More Read More

Our group is in a collaboration with other groups from Germany, Italy and the US to perform the PEPSI Exoplanet Transit Survey (PETS), which investigates exoplanet atmospheres in transmission and reflection observations. The first paper of the paper series is now published, and it’s an investigation of the nature of 55 Cnc e, a small rocky exoplanet, performed by my postdoc Engin Keles. The PEPSI exoplanet transit survey (PETS) I: investigating the presence of a silicate atmosphere on the super-earth…

Read More Read More