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Paper on the day-side temperature of KELT-1b, a low-mass brown dwarf ?>

Paper on the day-side temperature of KELT-1b, a low-mass brown dwarf

In a recent work by Prof. Carolina von Essen, with large contributions from our group from the side of Dr. Matthias Mallonn (and minor contributions from myself), we investigate the TESS phase curve and the dayside temperature of KELT-1b, which is a bit too heavy to still be called a planet and is therefore classified as a low-mass brown dwarf. From the abstract: We present the detection and analysis of the phase curve of KELT-1b at optical wavelengths, analyzing data…

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Paper on stellar winds blowing around our nearest exoplanet neighbour ?>

Paper on stellar winds blowing around our nearest exoplanet neighbour

A recent work led by our Schwarzschild-Fellow Dr. Julián Alvarado-Gómez shows through numerical simulations that our nearest exoplanetary neighbour experiences a space weather environment similar to our own Earth. The planet is Proxima Centauri c, a planet a few times the size of the Earth, which orbits our nearest stellar neighbour Proxima Centauri in a roughly 5-year orbit. From the abstract: A new planet has been recently discovered around Proxima Centauri. With an orbital separation of ∼1.44 au and a…

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Paper on stellar flares in open clusters ?>

Paper on stellar flares in open clusters

Ekaterina Ilin, a PhD student in my group, has recently published her work on stellar flares in three young and two middle-aged open clusters. From the abstract: “Drawing from the complete K2 archive, we searched 3435∼80 day long light curves of 2111 open cluster members for flares using the open-source software packages K2SC to remove instrumental and astrophysical variability from K2 light curves, and AltaiPony to search and characterize the flare candidates. We confirmed a total of 3844 flares on…

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Paper on the atmospheric evaporation of four very young exoplanets ?>

Paper on the atmospheric evaporation of four very young exoplanets

Together with my PhD student Laura Ketzer and postdoc Matthias Mallonn, we have published a new paper on the atmospheric evaporation of the four very young planets around the star V1298 Tau. We measured the star’s X-ray spectrum by combining ROSAT and Chandra observations, and found that the star is highly active with an X-ray luminosity above 10^30 erg/s. Laura developed a numerical code to estimate the planetary evaporation as the star ages and becomes less X-ray bright. Depending on…

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Paper on the magnetic activity of old sunlike stars ?>

Paper on the magnetic activity of old sunlike stars

My freshly graduated PhD student, Dr. Rachel Booth, has published the final paper from her PhD thesis together with me and a few coworkers. We have analysed how the magnetic activity of sun-like stars decays as they age, and have used a sample of stars that all have well-determined asteroseismic ages. We find that even at old stellar ages on the main sequence the spin down and therefore the decay of stellar activity continues. For a read go here: “Chromospheric…

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Paper on alkali metals in an exoplanet’s atmosphere ?>

Paper on alkali metals in an exoplanet’s atmosphere

Together with my colleagues at AIP, and led by Engin Keles, a PhD student in my Star-Planet Systems group, we have published a paper on the detection of potassium in the atmosphere of a Hot Jupiter using high-resolution transmission spectroscopy. The potassium absorption on HD189733b and HD209458b, Keles, E.; Mallonn, M.; von Essen, C.; Carroll, T. A.; Alexoudi, X.; Pino, L.; Ilyin, I.; Poppenhäger, K.; Kitzmann, D.; Nascimbeni, V.; Turner, J. D.; Strassmeier, K. G. The Large Binocular Telescope (LBT)…

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White paper on X-ray interferometry ?>

White paper on X-ray interferometry

Together with many colleagues, I have contributed to a White Paper on a possible X-ray Interferometry mission. This project is led by Phil Uttley from the University of Amsterdam, and we hope to be considered for ESA’s Vision 2050 mission slot. X-ray interferometry can yield amazing spatial resolution for bright X-ray sources, even though there is still quite some technology to be developed. For stars and exoplanets, we could spatially resolve transits in front of the stellar corona – see…

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New papers: exoplanets and stellar results from NGTS ?>

New papers: exoplanets and stellar results from NGTS

The Next Generation Transit Survey has had some new discoveries over the past few months which I was happy to contribute to. We’ve discovered a new exoplanet (an inflated hot Jupiter), a fully-convective eclipsing binary system, and a giant flare with pulsations on a pre-main sequence M star. The papers are: “NGTS-2b: an inflated hot-Jupiter transiting a bright F-dwarf”, L. Raynard and 44 co-authors including K. Poppenhaeger, Monthly Notices of the Royal Astronomical Society, Volume 481, Issue 4, p.4960-4970 (2018)…

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New paper: X-ray emission line spectra of main-sequence stars ?>

New paper: X-ray emission line spectra of main-sequence stars

We investigated the X-ray emission line spectra of cool main-sequence stars in order to construct their emission measure distributions and compare them to the Sun: “A Chandra/LETGS Survey of Main-sequence Stars” We analyze the X-ray spectra of 19 main-sequence stars observed by Chandra using its LETGS configuration. Emission measure (EM) distributions are computed based on emission line measurements, an analysis that also yields evaluations of coronal abundances. The use of newer atomic physics data results in significant changes compared to…

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New paper: Unmasking a hot Jupiter in an unresolved binary system ?>

New paper: Unmasking a hot Jupiter in an unresolved binary system

The NGTS planet-search project in which I take part has detected a new planet in an interesting system: “Unmasking the hidden NGTS-3Ab: a hot Jupiter in an unresolved binary system” We present the discovery of NGTS-3Ab, a hot Jupiter found transiting the primary star of an unresolved binary system. We develop a joint analysis of multi-colour photometry, centroids, radial velocity (RV) cross-correlation function (CCF) profiles and their bisector inverse slopes (BIS) to disentangle this three-body system. Data from the Next…

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