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Category: research

New paper: Magnetic activity of old cool stars ?>

New paper: Magnetic activity of old cool stars

Happy to report that my PhD student Rachel Booth has successfully published her first paper! It’s a very interesting analysis of the magnetic activity of old cool stars, with a surprising find about the decline of activity at old stellar ages. Our paper has also been featured on the Astrobites blog: https://astrobites.org/2017/07/03/adventures-in-watchmaking-for-cool-stars/. Here’s the abstract of the paper: Stars with convective envelopes display magnetic activity, which decreases over time due to the magnetic braking of the star. This age-dependence of…

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Conference “Atmospheres of disks and planets” at castle Ringberg ?>

Conference “Atmospheres of disks and planets” at castle Ringberg

I just spent a really exciting week at castle Ringberg in south Germany, where the Max-Planck Institute for Astronomy held a conference on exoplanet formation and atmospheric composition. Lots of interesting discussions and new results. I was invited to give a talk on the topic of “Stellar activity and planet characterisation” – one of my favourite topics to talk about. My personal highlight of the conference was Yamila Miguel’s presentation about the latest results from the Juno mission: we finally…

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Today’s seminar: R Coronae Borealis stars ?>

Today’s seminar: R Coronae Borealis stars

Today Geoff Clayton from Louisiana State University gave a talk about R Coronae Borealis stars at our astrophysics seminar. These kinds of stars show erratic drops of several magnitudes in brightness over hundreds of years (R Coronae Borealis itself was discovered to be variable in 1795), and it’s still a somewhat open question what these things actually *are*. It’s not at all my field of study, but it was a really interesting talk and exactly the kind of talk I…

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New paper: Testing if Fomalhaut b is a neutron star ?>

New paper: Testing if Fomalhaut b is a neutron star

Happy to report that our paper has also been picked for presentation on the Astrobites blog: https://astrobites.org/2017/03/24/a-neutron-star-in-the-eye-of-sauron/. Here’s the abstract of the paper: Fomalhaut b is a directly imaged object in the debris disk of the star Fomalhaut. It has been hypothesized to be a planet, however there are issues with the observed colours of the object that do not fit planetary models. An alternative hypothesis is that the object is a neutron star in the near fore- or background…

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New paper on magnetic cycle simulation of Proxima Centauri ?>

New paper on magnetic cycle simulation of Proxima Centauri

The recent discovery of an Earth-like exoplanet around Proxima Centauri has shined a spot light on slowly rotating fully convective M-stars. When such stars rotate rapidly (period <20 days), they are known to generate very high levels of activity that is powered by a magnetic field much stronger than the solar magnetic field. Recent theoretical efforts are beginning to understand the dynamo process that generates such strong magnetic fields. However, the observational and theoretical landscape remains relatively uncharted for fully…

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New papers on the ARCUS mission ?>

New papers on the ARCUS mission

Arcus is a NASA/MIDEX mission under development in response to the anticipated 2016 call for proposals. It is a freeflying, soft X-ray grating spectrometer with the highest-ever spectral resolution in the 8-51 Å (0.24 – 1.55 keV) energy range. The Arcus bandpass includes the most sensitive tracers of diffuse million-degree gas: spectral lines from O VII and O VIII, H- and He-like lines of C, N, Ne and Mg, and unique density- and temperature-sensitive lines from Si and Fe ions….

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New paper on the disappearing disk of TYC 8241 2652 1 ?>

New paper on the disappearing disk of TYC 8241 2652 1

TYC 8241 2652 1 is a young star that showed a strong mid-infrared (mid-IR, 8-25 mu) excess in all observations before 2008 consistent with a dusty disk. Between 2008 and 2010 the mid-IR luminosity of this system dropped dramatically by at least a factor of 30 suggesting a loss of dust mass of an order of magnitude or more. We aim to constrain possible models including removal of disk material by stellar activity processes, the presence of a binary companion,…

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Exoplanets conference in Bonn ?>

Exoplanets conference in Bonn

This week I am in Bonn, Germany, to give an invited talk entitled “Interactions between exoplanets and their host stars” at the conference Exoplanets – Bridging the gap between theory and observations. The conference takes place at the beautiful historical Physikzentrum in Bad Honnef. Lots of interesting talks and posters, from planet definitions (and how we should change them) to upcoming observational missions and planet formation theory. Plenty of time for discussion with all participants!

New paper on geodynamo simulations ?>

New paper on geodynamo simulations

Earth sustains its magnetic field by a dynamo process driven by convection in the liquid outer core. Geodynamo simulations have been successful in reproducing many observed properties of the geomagnetic field. However, while theoretical considerations suggest that flow in the core is governed by a balance between Lorentz force, rotational force and buoyancy (called MAC balance for Magnetic, Archimedean, Coriolis) with only minute roles for viscous and inertial forces, dynamo simulations must employ viscosity values that are many orders of…

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Cool Stars 19 conference review ?>

Cool Stars 19 conference review

One of my favourite conferences, the Cool Stars Workshop, took place in Uppsala last week. My PhD student Rachel Booth presented her work in a talk at the splinter session on Stellar Magnetic Activity – her first talk at a conference! And she did great! A lot of interesting stuff is going on at the moment with the spin-down and decrease in magnetic activity of old cool stars, and it seems like there may be different trends of rotation with…

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