We present new spatially resolved astrometry and photometry from the Gemini Planet Imager of the inner binary of the young multiple star system V343 Normae, which is a member of the beta Pictoris (beta Pic) moving group. V343 Normae comprises a K0 and mid-M star in a similar to 4.5 year orbit (AaAb) and a wide 10 '' M5 companion (B). By combining these data with archival astrometry and radial velocities we fit the orbit and measure individual masses for both components of M-Aa = 1.10 +/- 0.10M(circle dot) and M-Ab= 0.290 +/- 0.018 M-circle dot. Comparing to theoretical isochrones, we find good agreement for the measured masses and JHK band magnitudes of the two components consistent with the age of the beta Pic moving group. We derive a model-dependent age for the beta Pic moving group of 26 +/- 3 Myr by combining our results for V343 Normae with literature measurements for GJ. 3305, which is another group member with resolved binary components and dynamical masses.

We study the formation of planetesimals in protoplanetary disks from the gravitational collapse of solid over-densities generated via the streaming instability. To carry out these studies, we implement and test a particle-mesh self-gravity module for the ATHENA code that enables the simulation of aerodynamically coupled systems of gas and collisionless self-gravitating solid particles. Upon employment of our algorithm to planetesimal formation simulations, we find that (when a direct comparison is possible) the ATHENA simulations yield predicted planetesimal properties that agree well with those found in prior work using different numerical techniques. In particular, the gravitational collapse of streaming-initiated clumps leads to an initial planetesimal mass function that is well-represented by a power law, dN / dM(p) proportional to M-p(-p), with p similar or equal to 1.6 +/- 0.1, which equates to a differential size distribution of dN / dR(p) proportional to R-p(-q), with q similar or equal to 2.8 +/- 0.1. We find no significant trends with resolution from a convergence study of up to 512(3) grid zones and N-par approximate to 1.5 x 10(8) particles. Likewise, the power-law slope appears indifferent to changes in the relative strength of self-gravity and tidal shear, and to the time when (for reasons of numerical economy) self-gravity is turned on, though the strength of these claims is limited by small number statistics. For a typically assumed radial distribution of minimum mass solar nebula solids (assumed here to have dimensionless stopping time tau = 0.3), our results support the hypothesis that bodies on the scale of large asteroids or Kuiper Belt Objects could have formed as the high-mass tail of a primordial planetesimal population.

The asteroid (16) Psyche is of scientific interest because it contains similar to 1% of the total mass of the asteroid belt and is thought to be the remnant metallic core of a protoplanet. Radar observations have indicated the significant presence of metal on the surface with a small percentage of silicates. Prior ground-based observations showed rotational variations in the near-infrared (NIR) spectra and radar albedo of this asteroid. However, no comprehensive study that combines multi-wavelength data has been conducted so far. Here we present rotationally resolved NIR spectra (0.7-2.5 mu m) of (16) Psyche obtained with the NASA Infrared Telescope Facility. These data have been combined with shape models of the asteroid for each rotation phase. Spectral band parameters extracted from the NIR spectra show that the pyroxene band center varies from similar to 0.92 to 0.94 mu m. Band center values were used to calculate the pyroxene chemistry of the asteroid, whose average value was found to be Fs(30)En(65)Wo(5). Variations in the band depth (BD) were also observed, with values ranging from 1.0% to 1.5%. Using a new laboratory spectral calibration method, we estimated an average orthopyroxene content of 6% +/- 1%. The mass-deficit region of Psyche, which exhibits the highest radar albedo, also shows the highest value for the spectral slope and the minimum BD. The spectral characteristics of Psyche suggest that its parent body did not have the typical structure expected for a differentiated body or that the sequence of events that led to its current state was more complex than previously thought.

The inner regions of discs around close binary systems are dominated by tidally truncated eccentric cavities. These are believed to play a key role in dictating where planets formed in these circumbinary discs halt their disc-driven migration. In this thesis we present work examining processes which could impact the evolution and structure of this region, and the planets which interact with it. First, we investigate the role of self-gravity and disc-mass on circumbinary discs and planets. The greatest impact of self-gravity was found in discs around highly eccentric binaries, and in discs with high masses. In these cases, self-gravity acts to compact the scale of the inner cavity region. For the highest disc masses, additional eccentric features arise in the outer disc. A range of scenarios examining planetary migration, accretion and disc dissipation find that if planets form and evolve in a high-mass environment, the disc structures formed by self-gravity can leave a fingerprint on the planetary architecture once the disc has dissipated. We also significantly modify the publicly available fargo-adsg hydrodynamical code, to include radiative effects such as disc irradiation by the binary stars, radiative transport and disc surface cooling. We present preliminary results of simulations of adiabatic circumbinary discs with these effects included, and consider also the migration of protoplanets within them. Fully radiative discs produce a smaller inner cavity than obtained in previous isothermal models - a promising result for the end point of planet migration in these discs. Whilst we have found significant alteration of the circumbinary enviroment by self-gravity and radiative effects, future simulations that capture the 3-D nature of these discs will be required to fully describe the observed architecture of the circumbinary systems.

Over the last decade, 135 extrasolar planets have been discovered, the vast majority found by ongoing radial velocity searches. Of the stars sampled in these searches, 1% have `Hot Jupiter' planets associated with them. Having masses equivalent to Jupiter yet orbital periods of only a few days, this new class of planet is clearly unlike anything in our Solar System.¶ Hot Jupiters present us with an intriguing prospect. If the orientation of the planetary orbit is close to edge-on, the planet will periodically transit across the face of its star, resulting in a small drop in brightness. This transit phenomenon has been successfully used for planet detection over the last couple of years, allowing determination of the planetary radius and accurate mass estimates when coupled with radial velocity observations.¶ To aid understanding of the effect stellar environment plays on Hot Jupiter formation and survivability, this thesis presents the results of a wide-field search for transiting Hot Jupiters in the globular cluster 47 Tucanae. This cluster presents many thousands of stars in a moderate field of view and provides the perfect target for a search of this nature. One previous transit search has been made in the central core of 47 Tuc; using the HST for 8.3 continuous days, Gilliland et.al (2000) expected 17 transits yet found none. This null result suggests that either system metallicity or stellar density may be inhibiting Hot Jupiter formation or survivability in the cluster.¶ This thesis presents a search for transits with a field of view 250 times larger than the HST search and samples the uncrowded outer halo of the cluster (previously unsampled for transits), providing important constraints on the effect of environment on Hot Jupiter formation. If planets are found, then stellar density would seem responsible for the Gilliland et.al (2000) core null result. If no planets are found to a significant level, the survey would provide strong evidence that system metallicity is the dominant factor. Using the ANU 40'' (1m) telescope at Siding Spring Observatory, a 30.4 night observing run was executed and photometry was derived via differential imaging. The dataset numbers 109,000 cluster (and field) stars for photometric analysis, of which 22,000 are suitable for the transit search. With a custom-written transit detection algorithm and extensive Monte Carlo simulations to model the dataset, seven planets should be detectable if the occurrence rate of Hot Jupiters is the same in the cluster as in the Solar Neighbourhood.¶ Despite a detailed search, no transit signatures were identified. This result strongly indicates that the low metallicity of the cluster is the dominant factor inhibiting planet formation in 47 Tuc. Current results in the Solar Neighbourhood show that planet frequency is strongly biased towards stars of high metallicity. This thesis shows that the metallicity trend is likely a universal phenomenon, not only limited to the immediate Solar Neighbourhood and raises questions of whether planets were much rarer in the earlier Universe.¶ As a side result of the search, 100 variable stars were identified in the field, 69 of which are new discoveries. Subsequent analysis reveals a strong period segregation among the cluster eclipsing binaries, indicating previously unobserved dynamical effects in the cluster. Distance estimates for both 47 Tuc and the SMC are in agreement with previously published values and an independent identification of the binary period-colour relation was observed. Two binaries seem to have low-luminosity companions worthy of followup and one variable is likely a star in the early phases of planetary nebula formation. All of the results presented in this thesis have been published in three separately refereed research papers.

This report describes StarMapper, a mobile appliation designed for the Android platform that interactively maps the celestial sky and can provide information from Wikipedia about celestial objects to the user. The stars, constellations, planets, sun, and moon are all rendered in real-time and the user can navigate the celestial map simply by pointing the device around the sky to find and identify the different celestial objects. However, if the user prefers, a manual touch-based map navigation feature is also available in StarMapper. While other Android applications currently exist for mapping the sky, such as Google's Sky Map, StarMapper aims to enhance the experience by also providing additional information about celestial objects to the user by means of a simple click on the screen. For obtaining more information about a particular constellation or other celestial object, the user only needs to click on the object's name in the map, and the device's web browser opens to the Wikipedia page of the clicked object. Through this simple mechanism, the user can learn much more about astronomy than just locations of celestial objects. / text

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We present an equatorial (± 30◦ Decl.) sample of all known single (within 4′′) mid M-dwarfs (M2.5V-M8.0V) extending out to 10 pc. For this sample of 58 stars, we provide photometry, low dispersion optical (6000−9000 ̊A) spectra from which spectral types are determined, Hα equivalent widths, and gravity sensitive NaI indices. For 45 of these 58 stars, strict limits are placed on the presence of companions, based on precise infrared radial velocities. Our spectroscopic results indicate that on average, we rule out the existence of companions with masses of 1.5 MJUP or greater in 10 day orbital periods around slowly rotating (vsini < 6.5 km s−1) M-dwarfs. Similarly, strict limits are placed on the presence of companions to 53 out of the 58 stars with astrometry. Our astrometric results show that, on average, we rule out the presence of companions with masses greater than 9 MJUP with an orbital period of 8 years. These results establish these stars as the nearest set of single mid M-dwarfs. Two additional stars, GJ 867B and LHS 1610, were initially included in this program, but later discovered to be spectroscopic binaries (SB). The binary GJ 867BD is a wide (24.5') companion to the M2 dwarf GJ 867AC. With this discovery, the GJ 867 system (d =8.82 ± 0.08 pc) becomes one of only four quadruple systems with in 10 pc of the Sun and the only among these with all M-dwarf (or cooler components). To measure how the rotational velocities vary with spectral type, we assembled a list of all known single (within 3′′) mid M-dwarfs that have trigonometric parallaxes within 25 pc and reside between −30◦ and +65◦ Decl from the RECONS sample. From this list of 402 stars, only 169 stars have previously reported vsini values. We obtained spectroscopic measurements for an additional 75 stars. Of those, 17 have vsini values above our detection threshold of 3 km s−1. Our data are consistent with the trend of more low mass M-dwarfs having high projected rotational velocity values than high mass M-dwarfs.

We present updated observations of a pilot survey of 14 pulsating DA white dwarfs, monitored for evidence of center-of-mass motion caused by a planetary companion. We have nearly doubled the number of periodicites for which we can produce O-C diagrams that document pulse arrival times from our stars, and have implemented a method to minimize the apertures we use in our reductions in order to reduce sky noise. In addition to a previously published candidate, GD66, we have identi fed at least four more systems worthy of rigorous observational follow-up. We have also implemented a method, a generalized Lomb-Scargle periodogram, that takes into account weighted points in order to characterize any periodic behavior present in our O-C diagrams. For at least one DAV within this same sample, we have found strong observational evidence for an evolutionary time scale (via the rate of period change) that is inconsistent with cooling alone. In that star, WD0111+0018, we report for the first time measurement of the rate of period change of nonlinear combination frequencies in a pulsating white dwarf. We speculate that this may be caused by a changing rotation rate that aff ects only modes with m not equal to 0. / text

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