High resolution ALMA and HST imaging of κ CrB : a broad debris disc around a post-main sequence star with low-mass companions

κ CrB is a ~2.5 Gyr old K1 sub-giant star, with an eccentric exo-Jupiter at ~2.8 au and a debris disc at tens of au. We present ALMA Band 6 (1.3 mm) and HST scattered light (0.6 μm) images, demonstrating κ CrB's broad debris disc, covering an extent 50 - 180 au in the millimetre (peaking at 110 au), and 51 - 280 au in scattered light (peaking at 73 au). By modelling the millimetre emission, we estimate the dust mass as ~0.016 M⊕, and constrain lower-limit planetesimal sizes as Dmax ≳ 1 km and the planetesimal belt mass as Mdisc ≳ 1 M⊕. We constrain the properties of an outer body causing a linear trend in 17 years of radial velocity data to have a semi-major axis 8 - 66 au and a mass 0.4 - 120 MJup. There is a large inner cavity seen in the millimetre emission, which we show is consistent with carving by such an outer massive companion with a string of lower mass planets. Our scattered light modelling shows that the dust must have a high anisotropic scattering factor (g ~ 0.8 - 0.9) but an inclination (i ~ 30 - 40○) that is inferred to be significantly lower than the i ~ 61○ millimetre inclination. The origin of such a discrepancy is unclear, but could be caused by a misalignment in the micron and millimetre sized dust. We place an upper limit on the CO gas mass of MCO < (4.2 - 13) × 10-7 M⊕, and show this to be consistent with levels expected from planetesimal collisions, or from CO-ice sublimation as κ CrB begins its giant branch ascent

WD 0141−675: a case study on how to follow-up astrometric planet candidates around white dwarfs

This work combines spectroscopic and photometric data of the polluted white dwarf WD 0141−675, which has a now retracted astrometric super-Jupiter candidate, and investigates the most promising ways to confirm Gaia astrometric planetary candidates and obtain follow-up data. Obtaining precise radial velocity measurements for white dwarfs is challenging due to their intrinsic faint magnitudes, lack of spectral absorption lines, and broad spectral features. However, dedicated radial velocity campaigns are capable of confirming close-in giant exoplanets (a few MJup) around polluted white dwarfs, where additional metal lines aid radial velocity measurements. Infrared emission from these giant exoplanets is shown to be detectable with JWST Mid-Infrared Instrument (MIRI) and will provide constraints on the formation of the planet. Using the initial Gaia astrometric solution for WD 0141−675 as a case study, if there were a planet with a 33.65 d period or less with a nearly edge-on orbit, (1) ground-based radial velocity monitoring limits the mass to &lt;15.4 MJup, and (2) space-based infrared photometry shows a lack of infrared excess and in a cloud-free planetary cooling scenario, a substellar companion would have to be &lt;16 MJup and be older than 3.7 Gyr. These results demonstrate how radial velocities and infrared photometry can probe the mass of the objects producing some of the astrometric signals, and rule out parts of the brown dwarf and planet mass parameter space. Therefore, combining astrometric data with spectroscopic and photometric data is crucial to both confirm and characterize astrometric planet candidates around white dwarfs

Historic landscape character and sense of place

This is an Author's Accepted Manuscript of an article published in Landscape Research, 2013, Vol. 38, Issue 2 pp.179-202, copyright Taylor & Francis, available online at: http://www.tandfonline.com/10.1080/01426397.2012.672642.Most studies of landscape character within archaeology and historical geography have focused on morphological features such as whether settlement patterns were nucleated or dispersed, but this paper discusses how adding depth to this, for example by studying place-names, vernacular architecture, and the territorial structures within which a landscape was managed in the past, gives us a far greater understanding of its texture and meaning to local communities. In two case-studies in southern Essex, for example, it is shown how the connections that once existed between inland and coastal communities can be used today to promote public access to the countryside. A further case study, in southwest England, shows how field-/place-names and vernacular architecture also make an important contribution to our appreciation of the time depth and complexity of landscape character.Arts and Humanities Research Council (AHRC)Southend-on-Sea Borough Counci

The English medieval first-floor hall: part 2 – The evidence from the eleventh to early thirteenth century

The concept of the first-floor hall was introduced in 1935, but Blair’s paper of 1993 cast doubt on many of those buildings which had been identified as such. Following the recognition of Scolland’s Hall, Richmond Castle as an example of a hall at first-floor level, the evidence for buildings of this type is reviewed (excluding town houses and halls in the great towers of castles, where other issues apply). While undoubtedly a number of buildings have been mistakenly identified as halls, there is a significant group of structures which there are very strong grounds to classify as first-floor halls. The growth of masonry architecture in elite secular buildings, particularly after the Norman Conquest, allowed halls to be constructed on the first floor. The key features of these are identified and the reasons for constructing the hall at this level – prestige and security – are recognized. The study of these buildings allows two further modifications to the Blair thesis: in some houses, halls and chambers were integrated in a single block at an early date, and the basic idea of the medieval domestic plan was already present by the late eleventh century

Thasos

n/

Unresolved stellar companions with Gaia DR2 astrometry

For stars with unresolved companions,motions of the centre of light and that of mass decouple, causing a single-source astrometric model to perform poorly. We show that such stars can be easily detected with the reduced χ2 statistic, or renormalized unit weight error (RUWE), provided as part of Gaia DR2. We convert RUWE into the amplitude of the image centroid wobble, which, if scaled by the source distance, is proportional to the physical separation between companions (for periods up to several years).We test this idea on a sample of known spectroscopic binaries and demonstrate that the amplitude of the centroid perturbation scales with the binary period and the mass ratio as expected. We apply this technique to the Gaia DR2 data and show how the binary fraction evolves across the Hertzsprung-Russell diagram. The observed incidence of unresolved companions is high for massive young stars and drops steadily with stellarmass, reaching its lowest levels for white dwarfs.We highlight the elevated binary fraction for the nearby blue stragglers and blue horizontal branch stars.We also illustrate how unresolved hierarchical triples inflate the relative velocity signal in wide binaries. Finally, we point out a hint of evidence for the existence of additional companions to the hosts of extrasolar hot Jupiters