HAT-P-30b: A Transiting Hot Jupiter on a Highly Oblique Orbit

We report the discovery of HAT-P-30b, a transiting exoplanet orbiting the V = 10.419 dwarf star GSC 0208-00722. The planet has a period P = 2.810595 ± 0.000005 days, transit epoch Tc = 2455456.46561 ± 0.00037 (BJD), and transit duration 0.0887 ± 0.0015 days. The host star has a mass of 1.24 ± 0.04 M_⊙, radius of 1.21 ± 0.05 R_⊙, effective temperature of 6304 ± 88 K, and metallicity [Fe/H] = +0.13 ± 0.08. The planetary companion has a mass of 0.711 ± 0.028 M J and radius of 1.340 ± 0.065 R J yielding a mean density of 0.37 ± 0.05 g cm^(–3). We also present radial velocity measurements that were obtained throughout a transit that exhibit the Rossiter-McLaughlin effect. By modeling this effect, we measure an angle of λ = 73.°5 ± 9.°0 between the sky projections of the planet's orbit normal and the star's spin axis. HAT-P-30b represents another example of a close-in planet on a highly tilted orbit, and conforms to the previously noted pattern that tilted orbits are more common around stars with T_(eff*) ≳ 6250 K

A novel approach to relativistic ray-tracing technique in N-body simulations

N-body simulations are fundamental to cosmology and essential for high-precision investigations. Theoretical predictions are made in the simulations and compared to observations, owing to their known cosmological parameters, and hence makes them crucial for future tests of general relativity (GR) on cosmological scales – specifically, a test of GR via cosmic magnification in the weak lensing regime. Whilst N-body simulations are the theoretical tool that is requisite for generating mock weak lensing galaxy catalogues, it is ray-tracing technique that permits the study of light propagation within the catalogues; to trace simulated light paths through spacetime. However, there must be assurance that ray-tracing technique does not ignore the effects of gravitational lensing. Most studies simulate light paths along straight trajectories in three-dimensional space. Yet on larger scales, this assumption will lead to inaccuracies; photons follow a curved trajectory as they pass a gravitational field. A small number of relativistic ray-tracing codes have been developed to address this issue. Therefore, I investigate an existing relativistic ray-tracing algorithm and evaluate, experiment and modify the code for the purpose of testing GR physics via cosmic magnification in future research. A novel experimentation design has been applied to the code – a proof-of-concept methodological approach – that ultimately seeks to input an extended list of particle values and output gravitational lensing results. More specifically, the modified code assigns the non-gridded gravitational potentials from a Gadget-2 dark matter halo simulation file onto a three-dimensional grid, in which the values are interpolated and integrated through the remainder of the modified code. Gadget-2 simulation files are a popular choice for cosmologists and astrophysicists to conduct their studies of light propagation via ray-tracing, hence this modified design is a contribution to the field. Additionally, the results are further verified by establishing contour plots of the displacement angles, which will be compared to the projected mass surface density, Σ, in the next stage of research; by inputting the solutions to the geodesic equations and outputting a projection of the three-dimensional mass distribution onto a two-dimensional surface. This modified relativistic ray-tracing algorithm will be employed for an upcoming test of GR on cosmological scales, where the simulation will be populated with real data from the EMU radio galaxy survey. Theoretical predictions of cosmic magnification will be made, via the cross-correlation of distant radio galaxies and nearby optical galaxies, in which the lensing measurements will indicate if there is conformity to GR

Extracting Radial Velocities of A- and B-type Stars from Echelle Spectrograph Calibration Spectra

We present a technique to extract radial velocity measurements from echelle spectrograph observations of rapidly rotating stars ($V\sin{i} \gtrsim 50$ km s$^{-1}$). This type of measurement is difficult because the line widths of such stars are often comparable to the width of a single echelle order. To compensate for the scarcity of lines and Doppler information content, we have developed a process that forward-models the observations, fitting the radial velocity shift of the star for all echelle orders simultaneously with the echelle blaze function. We use our technique to extract radial velocity measurements from a sample of rapidly rotating A- and B-type stars used as calibrator stars observed by the California Planet Survey observations. We measure absolute radial velocities with a precision ranging from 0.5-2.0 km s$^{-1}$ per epoch for more than 100 A- and B-type stars. In our sample of 10 well-sampled stars with radial velocity scatter in excess of their measurement uncertainties, three of these are single-lined binaries with long observational baselines. From this subsample, we present detections of two previously unknown spectroscopic binaries and one known astrometric system. Our technique will be useful in measuring or placing upper limits on the masses of sub-stellar companions discovered by wide-field transit surveys, and conducting future spectroscopic binarity surveys and Galactic space-motion studies of massive and/or young, rapidly-rotating stars.Comment: Accepted to ApJ

The Populations of Comet-Like Bodies in the Solar system

A new classification scheme is introduced for comet-like bodies in the Solar system. It covers the traditional comets as well as the Centaurs and Edgeworth-Kuiper belt objects. At low inclinations, close encounters with planets often result in near-constant perihelion or aphelion distances, or in perihelion-aphelion interchanges, so the minor bodies can be labelled according to the planets predominantly controlling them at perihelion and aphelion. For example, a JN object has a perihelion under the control of Jupiter and aphelion under the control of Neptune, and so on. This provides 20 dynamically distinct categories of outer Solar system objects in the Jovian and trans-Jovian regions. The Tisserand parameter with respect to the planet controlling perihelion is also often roughly constant under orbital evolution. So, each category can be further sub-divided according to the Tisserand parameter. The dynamical evolution of comets, however, is dominated not by the planets nearest at perihelion or aphelion, but by the more massive Jupiter. The comets are separated into four categories -- Encke-type, short-period, intermediate and long-period -- according to aphelion distance. The Tisserand parameter categories now roughly correspond to the well-known Jupiter-family comets, transition-types and Halley-types. In this way, the nomenclature for the Centaurs and Edgeworth-Kuiper belt objects is based on, and consistent with, that for comets.Comment: MNRAS, in press, 11 pages, 6 figures (1 available as postscript, 5 as gif). Higher resolution figures available at http://www-thphys.physics.ox.ac.uk/users/WynEvans/preprints.pd

From the Stadium to the Boardroom: Training Student-Athletes to Write Professional Emails

A librarian and a writing professor share teaching strategies employed during a workshop designed for student-athletes, for whom email communication is crucial to success at college and in the workplace. This collaborative workshop aims to improve student awareness of rhetorical situations. Attendees will experience some interactive workshop strategies, including a “flipped” approach, and will receive lesson plans and advice on expanding the workshop to different student populations

On the potential for extinction by Muller's Ratchet in Caenorhabditis elegans

<p>Abstract</p> <p>Background</p> <p>The self-fertile hermaphrodite worm <it>C. elegans </it>is an important model organism for biology, yet little is known about the origin and persistence of the self-fertilizing mode of reproduction in this lineage. Recent work has demonstrated an extraordinary degree of selfing combined with a high deleterious mutation rate in contemporary populations. These observations raise the question as to whether the mutation load might rise to such a degree as to eventually threaten the species with extinction. The potential for such a process to occur would inform our understanding of the time since the origin of self-fertilization in <it>C. elegans </it>history.</p> <p>Results</p> <p>To address this issue, here we quantify the rate of fitness decline expected to occur via Muller's ratchet for a purely selfing population, using both analytical approximations and globally distributed individual-based simulations from the evolution@home system to compute the rate of deleterious mutation accumulation. Using the best available estimates for parameters of how <it>C. elegans </it>evolves, we conclude that pure selfing can persist for only short evolutionary intervals, and is expected to lead to extinction within thousands of years for a plausible portion of parameter space. Credible lower-bound estimates of nuclear mutation rates do not extend the expected time to extinction much beyond a million years.</p> <p>Conclusion</p> <p>Thus we conclude that either the extreme self-fertilization implied by current patterns of genetic variation in <it>C. elegans </it>arose relatively recently or that low levels of outcrossing and other factors are key to the persistence of <it>C. elegans </it>into the present day. We also discuss results for the mitochondrial genome and the implications for <it>C. briggsae</it>, a close relative that made the transition to selfing independently of <it>C. elegans</it>.</p