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Category: publications

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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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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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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Mission concept: X-ray Surveyor ?>

Mission concept: X-ray Surveyor

The X-ray Vision Workshop was held in DC in October last year, where a large group of astronomers including myself met to discuss the scientific potential of a new X-ray space telescope concept, The X-ray Surveyor. As part of the workshop we held a 2-hour brainstorming session on what kind of new scientific insights could come from this mission, and the results are now available in this publication: Allured et al. 2015, “X-ray Surveyor Discussion Session Results from the X-ray…

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