We have developed water vapour radiometers (WVRs) for the Australia Telescope Compact Array that are capable of determining signal path-length fluctuations by virtue of measuring small temperature fluctuations in the atmosphere using the 22.2-GHz water vapour line for each of the six antennae. By measuring the line-of-sight variations of the water vapour, the induced path excess and thus the phase delay can be estimated and corrections can then be applied during data reduction. This reduces decorrelation of the source signal. We demonstrate how this recovers the telescope's efficiency as well as how this improves the telescope's ability to use longer baselines at higher frequencies, thereby resulting in higher spatial resolution. A description of the WVR hardware design, their calibration, and water vapour retrieval mechanism is given.

Magnetism defines the complex and dynamic solar corona. Twists and tangles in coronal magnetic fields build up energy and ultimately erupt, hurling plasma into interplanetary space. These coronal mass ejections (CMEs) are transient riders on the ever-outflowing solar wind, which itself possesses a three-dimensional morphology shaped by the global coronal magnetic field. Coronal magnetism is thus at the heart of any understanding of the origins of space weather at the Earth. However, we have historically been limited by the difficulty of directly measuring the magnetic fields of the corona, and have turned to observations of coronal plasma to trace out magnetic structure. This approach is complicated by the fact that plasma temperatures and densities vary among coronal magnetic structures, so that looking at any one wavelength of light only shows part of the picture. In fact, in some regimes it is the lack of plasma that is a significant indicator of the magnetic field. Such a case is the coronal cavity: a dark, elliptical region in which strong and twisted magnetism dwells. I will elucidate these enigmatic features by presenting observations of coronal cavities in multiple wavelengths and from a variety of observing vantages, including unprecedented coronal magnetic field measurements now being obtained by the Coronal Multichannel Polarimeter (CoMP). These observations demonstrate the presence of twisted magnetic fields within cavities, and also provide clues to how and why cavities ultimately erupt as CMEs.

Until now, just a few extrasolar planets (30 out of 860) have been found through the direct imaging method. This number should greatly improve when the next generation of High Contrast Instruments like Gemini Planet Imager (GPI) at Gemini South Telescope or SPHERE at VLT will became operative at the end of this year. In particular, the Integral Field Spectrograph (IFS), one of the SPHERE subsystems, should allow a first characterization of the spectral type of the found extrasolar planets. Here we present the results of the last performance tests that we have done on the IFS instrument at the Institut de Planetologie et d'Astrophysique de Grenoble (IPAG) in condition as similar as possible to the ones that we will find at the telescope. We have found that we should be able to reach contrast down to 5 × 10−7 and make astrometry at sub-mas level with the instrument in the actual conditions. A number of critical issues have been identified. The resolution of these problems could allow to further improve the performance of the instrument.

Understanding how a disk surrounding a young star evolves and disperses is crucial in order to understand the subsequent planet formation. In this proceeding, we summarize the results reported by Rigliaco et al. (2013) on the origin of the [OI] low-velocity component as a possible disk dispersal indicator.

Recent simulation and observational data have been used to investigate the ability of Kozai oscillations to explain the formation of “hot Jupiter” planetary systems. One of the first exoplanets discovered, τ Boo Ab, orbits a star with a binary companion, making it an excellent testbed for this scenario. We have written a three-dimensional Markov Chain Monte Carlo (MCMC) simulator to constrain the orbit of the distant stellar companion τ Boo B, and are currently deriving orbital parameters and confidence intervals. These orbital parameters will confirm or reject Kozai oscillations as a plausible formation mechanism for τ Boo Ab.

A new high-contrast imaging subtraction algorithm (TLOCI) is presented to maximize a planet signal-to-noise ratio. The technique uses an input spectrum and template PSFs to optimize the reference image coefficient determination to minimize the flux contamination via self-subtraction (thus maximizing its throughput wavelength per wavelength) of any planet that have a similar spectrum to the template spectrum in the image, while trying, at the same time, to maximize the speckle noise subtraction. The optimization is performed by a correlation matrix conditioning. Using laboratory Gemini Planet Imager data, the new algorithm is shown to be superior to the simple/double difference, polynomial fit and original LOCI algorithm.

EX Lupi-type young stars (EXors) show sporadic brightenings of several magnitudes, caused by the episodic increase in the accretion rate of the circumstellar matter onto the young star. As the inner disk plays a crucial role during the onset of the outburst, we examined the quiescent properties of the circumstellar environment of EXors, focusing on the inner regions. We found that in case of three EXors (VY Tau, V1143 Ori and EX Lup) the spectral energy distributions show no or weak excess above the stellar photosphere at NIR-MIR wavelengths, indicative of inner disk clearing. A detailed radiative transfer modeling of the sources revealed that the inner regions of these disks had to go through significant evolution, either the inner radius of the dusty disk is beyond the sublimation radius and/or the inner disks are flattened.

We present the preliminary findings of an investigation of the multiplicity of debris disk stars identified within our Volume-limited A-star (VAST) multiplicity survey. Previous studies have produced conflicting results regarding the multiplicity fraction of debris disk-hosting stars compared with non-excess stars. By combining our large-scale volume-limited AO survey of A-type stars with the all-sky WISE catalogue, we have investigated the frequency of binary companions to a large sample of A-type stars with and without measured 22μm excess. The results of this study will allow for a greater understanding of the interaction between a companion star and a circumstellar debris disk, informing future study into the formation and stability of planetary-mass companions within binary systems.

For over a decade, the structure of the inner “hole” in the transition disk around TW Hydrae has been a subject of debate. To probe the innermost regions of the protoplanetary disk, observations at the highest possible spatial resolution are required. We present new interferometric data of TW Hya from near-infrared to millimeter wavelengths. We confront existing models of the disk structure with the complete data set and develop a new, detailed radiative-transfer model. This model is characterized by: 1) a spatial separation of the largest grains from the small disk grains; and 2) a smooth inner rim structure, rather than a sharp disk edge.

The Next Generation Transit Survey (NGTS) is a new ground-based survey for transiting exoplanets. Our primary goal is to find the first statistically-significant sample of Neptunes and super-Earths that are bright enough for radial velocity confirmation. By measuring precise masses and radii we will constrain the bulk composition and internal structure of planets that span the transition between the gas giants and terrestrial planets. Our brightest exoplanets will also be suitable for atmospheric characterisation with large facilities such as the VLT, JWST and the E-ELT. NGTS construction began in June 2013, and the survey is due to commence in 2014.

The magnetic breakout model has been widely used to explain solar eruptive activities. Here, we apply it to explain successive filament eruptions occurred in a quadrupolar magnetic source region. Based on the high temporal and spatial resolution, multi-wavelengths observations taken by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO), we find some signatures that support the occurrence of breakout-like external reconnection just before the start of the successive filament eruptions. Furthermore, the extrapolated three-dimensional coronal field also reveals that the magnetic topology above the quadrupolar source region resembles that of the breakout model. We propose a possible mechanism within the framework of the breakout model to interpret the successive filament eruptions, in which the so-called magnetic implosion mechanism is firstly introduced to be the physical linkage of successive filament eruptions. We conclude that the structural properties of coronal fields are important for producing successive filament eruptions.

The global magnetic field of the Sun is the determining parameter of spreading the solar wind in the interplanetary space. The global field changes the polarity synchronically with the cycle of solar activity. The interesting indicator of the polarity change are the occurence so-called polar belts of the prominences. The article shows the performance of these belts on observational work from 1975 to 2009. A coordinated effort is suggested for the compilation of data from different observers following the method described by Rušin et al., 1988.

In the present study, we consider where large, stable solar filaments form relative to underlying magnetic polarities. We find that 92% of all large stable filaments form in magnetic configurations involving the interaction of two or more bipoles. Only 7% form above the Polarity Inversion Line (PIL) of a single bipole. This indicates that a key element in the formation of large-scale stable filaments is the convergence of magnetic flux, resulting in either flux cancellation or coronal reconnection.

We report observations of a long filament that underwent recurrent partial eruptions on August 4, 6, and 8, 2012. The filament reappeared in the subsequent rotation of the Sun, and disappeared completely on August 31, 2012. We implemented an automated filament detection algorithm developed by us for estimating different attributes of these filaments few hours prior to its disappearance in Hα and studied their evolution. Based on these attributes, we determine the onset time of the disappearance of Hα filaments. We then compared these onset times with that of the associated CMEs observed by LASCO/SOHO coronagraphs. This is also useful to understand temporal relationship of EUV and X-ray flux variation associated with filament disappearances in Hα. Our results show the importance of such studies in understanding the mechanism of CME initiation, particularly the role of eruptive filaments, in this process.