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Author: ktj

New paper: evaporation of three young planets in the K2-198 system ?>

New paper: evaporation of three young planets in the K2-198 system

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…

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New papers: spectroscopy of the Sun and stars ?>

New papers: spectroscopy of the Sun and stars

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…

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New papers: Science with the ANDES spectrograph for the ELT ?>

New papers: Science with the ANDES spectrograph for the ELT

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…

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Celebration barbecue ?>

Celebration barbecue

This week we had a really nice afternoon barbecue with a bunch of people I like to call “star-planet group and friends” – i.e. my own group plus other colleagues mainly from the solar group and the MHD group. We had a lot to celebrate: my postdoc Ekaterina Ilin will start a new postdoctoral position in Groningen very soon, where she will work with Harish Vedantham on radio signatures of star-planet interactions; Prachi Rahate and Joana Wokittel have successfully defended…

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Paper on tidally-induced activity in an M dwarf / brown dwarf pair ?>

Paper on tidally-induced activity in an M dwarf / brown dwarf pair

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…

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EAS conference in Krakow ?>

EAS conference in Krakow

A good chunk of my research group plus myself spent last week in Krakow/Poland at the annual meeting of the European Astronomical Society (EAS). First time for me: we all took a “Eurocity” train that goes directly from Berlin to Krakow and takes 7 hours. Ecofriendly, and I was actually less wrung out after the train trip than I would have been after two flights (since there are no direct plane connections between Berlin and Krakow). The conference itself was…

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XMM-Newton Large Program: magnetism of old suns ?>

XMM-Newton Large Program: magnetism of old suns

I’m very excited these days because the first observation from my recently awarded XMM-Newton large observing program keeps getting scheduled and then re-scheduled by the XMM team. If all goes well, the first data will be collected before the end of June. The observing program is about the magnetism of old sun-like stars; specifically, my co-investigators and I want to figure out if there is still a magnetic braking mechanism operating in old stars that are rotating anomalously quickly. The…

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Conference: Heraeus-Seminar on the heliosphere, astrospheres and exoplanets ?>

Conference: Heraeus-Seminar on the heliosphere, astrospheres and exoplanets

Last week a huge delegation from my group attended the international Heraeus-Seminar “From the Heliosphere to Astrospheres – Lessons for Exoplanets and their Habitability” in Bad Honnef, Germany (conference website). We had contributed talks given by my group members Judy Chebly and Nikoleta Ilic, plus contributed talks by my group’s guests Yu Xu and Florian Rünger; posters given by Eliana Amazo-Gomez and Joana Wokittel; and three (!) invited talks by Ekaterina Ilin, Julian Alvarado-Gomez and myself. Unfortunately I became sick…

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Paper on host star activity and the exoplanet radius gap ?>

Paper on host star activity and the exoplanet radius gap

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…

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Paper on tidal star-planet interactions ?>

Paper on tidal star-planet interactions

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….

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