Predicting Stellar Angular Diameters from VV, ICI_C, HH, KK Photometry

Determining the physical properties of microlensing events depends on having accurate angular sizes of the source star. Using long-baseline optical interferometry we are able to measure the angular sizes of nearby stars with uncertainties $\leq 2\%$. We present empirically derived relations of angular diameters that are calibrated using both a sample of dwarfs/subgiants and a sample of giant stars. These relations are functions of five color indices in the visible and near-infrared, and have uncertainties of 1.8-6.5% depending on the color used. We find that a combined sample of both main-sequence and evolved stars of A-K spectral types is well fit by a single relation for each color considered. We find that in the colors considered, metallicity does not play a statistically significant role in predicting stellar size, leading to a means of predicting observed sizes of stars from color alone.Comment: 8 pages, 1 figure, accepted for publication in MNRA

Turning Earth into Venus: A Stochastic Model of Possible Evolutions of Terrestrial Topography

Venus may have had both an Earth-like climate as well as extensive water oceans and active (or incipient) plate tectonics for an extended interval of its history. The topographical power spectrum of Venus provides important clues to the planet's past evolution. By drawing detailed contrast with the strong low-order odd-$l$ dominated global topography of Earth, we demonstrate that the relatively flat Venusian topography can be interpreted to have arisen from the transition from active terrestrial-like plate tectonics to the current stagnant lid configuration at a time $\tau = 544^{+886}_{-193}$ million years before present. This scenario is plausible if loss of oceans and the attendant transition to a CO$_2$-dominated atmosphere were accompanied by rapid continental-scale erosion, followed by gradual lava resurfacing at an outflow rate $\sim$ 1 km$^{3}$ yr$^{-1}$. We study Venus' proposed topographical relaxation with a global diffusion-like model that adopts terrestrial erosion rates scaled to account for the increased rainfall and temperatures that would accompany a planet-wide transition from an Earth-like climate to the runaway greenhouse climate that could ultimately yield present-day Venus, with an estimate of $5.1^{+1.8}_{-1.1}$ Myr if the global erosion operated as efficiently as that of a typical bedrock river basin on Earth.Comment: 17 pages, 4 figures, submitted to AAS Journal

A new specimen of Dicynodon traquairi (Newton) (Synapsida: Anomodontia) from the Late Permian (Tartarian) of northern Scotland

A recently discovered natural mould of a complete, almost undistorted, skull and lower jaw of a dicynodont (c. 237mmoverall length), in a block of Upper Permian sandstone (= Dicynodon Assemblage Zone: Hopeman Sandstone Formation) from Clashach Quarry, Hopeman, Morayshire, is described using novel techniques, including Computed Tomography scanning (CT), Magnetic Resonance Imaging (MRI) and rapid-prototype modelling. It is assigned to the taxon Dicynodon traquairi (Newton, 1893). When compared with Dicynodon lacerticeps Owen, 1845, it is distinguished principally by having the pineal opening sunk deeply between the diverging parietals, subparallel pterygoid rami narrowly separated, with no transverse flanges, and in addition, a deeply grooved lower jaw symphysis. The southern African fauna lived on river flats in a higher (southern) palaeolatitude than the possibly desert-dwelling Scottish species. The Hopeman Sandstone Formation is of the same age as the better-known Cutties Hillock Sandstone Formation, whose fauna is briefly discussed and reviewed

On elliptic factors in real endoscopic transfer I

This paper is concerned with the structure of packets of representations and some refinements that are helpful in endoscopic transfer for real groups. It includes results on the structure and transfer of packets of limits of discrete series representations. It also reinterprets the Adams-Johnson transfer of certain nontempered representations via spectral analogues of the Langlands-Shelstad factors, thereby providing structure and transfer compatible with the associated transfer of orbital integrals. The results come from two simple tools introduced here. The first concerns a family of splittings of the algebraic group G under consideration; such a splitting is based on a fundamental maximal torus of G rather than a maximally split maximal torus. The second concerns a family of Levi groups attached to the dual data of a Langlands or an Arthur parameter for the group G. The introduced splittings provide explicit realizations of these Levi groups. The tools also apply to maps on stable conjugacy classes associated with the transfer of orbital integrals. In particular, they allow for a simpler version of the definitions of Kottwitz-Shelstad for twisted endoscopic transfer in certain critical cases. The paper prepares for spectral factors in twisted endoscopic transfer that are compatible in a certain sense with the standard factors discussed here. This compatibility is needed for Arthur's global theory. The twisted factors themselves will be defined in a separate paper.Comment: 48 pages, to appear in Progress in Mathematics, Volume 312, Birkha\"user. Also renumbering to match that of submitted versio

Planet Eclipse Mapping with Long-Term Baseline Drifts

High precision lightcurves combined with eclipse mapping techniques can reveal the horizontal and vertical structure of a planet's thermal emission and the dynamics of hot Jupiters. Someday, they even may reveal the surface maps of rocky planets. However, inverting lightcurves into maps requires an understanding of the planet, star and instrumental trends because they can resemble the gradual flux variations as the planet rotates (ie. partial phase curves). In this work, we simulate lightcurves with baseline trends and assess the impact on planet maps. Baseline trends can be erroneously modeled by incorrect astrophysical planet map features, but there are clues to avoid this pitfall in both the residuals of the lightcurve during eclipse and sharp features at the terminator of the planet. Models that use a Gaussian process or polynomial to account for a baseline trend successfully recover the input map even in the presence of systematics but with worse precision for the m=1 spherical harmonic terms. This is also confirmed with the ThERESA eigencurve method where fewer lightcurve terms can model the planet without correlations between the components. These conclusions help aid the decision on how to schedule observations to improve map precision. If the m=1 components are critical, such as measuring the East/West hotspot shift on a hot Jupiter, better characterization of baseline trends can improve the m=1 terms' precision. For latitudinal North/South information from the remaining mapping terms, it is preferable to obtain high signal-to-noise at ingress/egress with more eclipses.Comment: AJ, accepted, 22 page