J. Meaburn’s research while affiliated with University of Manchester and other places

We present the discovery and characterisation of the exoplanets WASP-113b and WASP-114b by the WASP survey, {\it SOPHIE} and {\it CORALIE}. The planetary nature of the systems was established by performing follow-up photometric and spectroscopic observations. The follow-up data were combined with the WASP-photometry and analysed with an MCMC code to obtain system parameters. The host stars WASP-113 and WASP-114 are very similar. They are both early G-type stars with an effective temperature of $\sim 5900\,$K, [Fe/H]$\sim 0.12$ and $T_{\rm eff}$ $\sim 4.1$dex. However, WASP-113 is older than WASP-114. Although the planetary companions have similar radii, WASP-114b is almost 4 times heavier than WASP-113b. WASP-113b has a mass of $0.48\,$ $\mathrm{M}_{\rm Jup}$ and an orbital period of $\sim 4.5\,$days; WASP-114b has a mass of $1.77\,$ $\mathrm{M}_{\rm Jup}$ and an orbital period of $\sim 1.5\,$days. Both planets have inflated radii, in particular WASP-113 with a radius anomaly of $\Re=0.35$. The high scale height of WASP-113b ($\sim 950$ km ) makes it a good target for follow-up atmospheric observations.

HFG1 is the first well observed planetary nebula (PN) which reveals a cometary-like structure. Its main morphological features consist of a bow shaped shell, which surrounds the central star, accompanied by a long collimated tail. In this study we perform two-dimensional hydrodynamic simulations modeling the formation of HFG1 from the interaction of the local ambient medium with the mass outflows of its Asymptotic Giant Branch (AGB) progenitor star. We attribute the cometary appearance of HFG1 to the systemic motion of the PN with respect to the local ambient medium. Due to its vital importance, we re-estimate the distance of HFG1 by modeling the spectral Energy distribution of its central star, V664 Cas, and we find a distance of (490 +/_ 50) pc. Our simulations show that none of our models with time invariant stellar wind and ambient medium properties are able to reproduce simultaneously the extended bow shock and the collimated tail observed in HFG1. Given this, we increase the complexity of our modeling considering that the stellar wind is time variable. The wind description is based on the predictions of the AGB and post-AGB evolution models. Testing a grid of models we find that the PROPERTIES of HFG1 are best reproduced by the mass outflows of a 3 M_sun AGB star. Such a scenario is consistent with the current observed properties of V664 Cas primary star, an O-type subdwarf, and bridges the evolutionary history of HFG1 central star with the observables of the PN. We discuss the implications of our study in the understanding of the evolution of AGB/post-AGB stars towards the formation of O-type subdwarfs surrounded by PNe.

The Galactic planetary nebula HFG1 reveals an intriguing morphology consisting of a bow shaped shell which surrounds the central star followed by a collimated tail. This unique cometary-like morphology of HFG1 has been attributed to the systemic motion of the planetary nebula (PN) with respect to the local ambient medium. In this work we model HFG1 and we find that its main features can best be explained by the time-dependent stellar winds of a supersonically moving star during its Asymptotic Giant Branch (AGB) and post-AGB phase. Given that the primary component of its central binary system (V664 Cas) is a ~ 0.6 M_sun O-type subdwarf, we consider the mass of its progenitor to be 3 M_sun as predicted by stellar evolution theory. We perform two-dimensional hydrodynamic simulations modeling the formation of the PN from the interaction of the mass outflows of a 3 M_sun runaway star with the local ambient medium. To keep the model self-consistent, the time-variable stellar wind is described by following the predictions of the AGB, post-AGB stellar evolutionary theory for such a star. The results show a good agreement with the observed morphological and emission properties of HFG1 achieving to connect the evolutionary history of its central star with the observables of the PN. We discuss the possible implications of our study in the understanding of the evolutionary paths towards the formation of O-type subdwarf and the observed properties of their surrounding PNe.

The Manchester-Athens Wide-Field Camera (MAWFC) is a joint project between the National Observatory of Athens and the Jodrell Bank Centre for Astrophysics of the Manchester University which aims to conduct a large-area sky survey with the aid of a customized camera and narrow-band filters properly designed for studying extended interstellar medium (ISM) structures in the optical emission lines of Ηα, [O III], and Hβ. Here, we present the main steps of the automated image processing pipeline which, apart from the basic analysis (e.g., bias, dark, and flat-fielding calibration), intends to remove the stellar contamination from the narrow-band images by means of advanced detection and smoothing techniques, and to compose mosaics of pure large-scale ISM filaments as further step. The procedure is applied to the first raw images of the survey (expected to be obtained during the spring/early summer of 2015) as well as to unprocessed images taken from older surveys.

The Manchester-Athens Wide-Field (Narrow-Band) Camera (MAWFC) is the first scientific instrument for astronomy that constructed and tested completely in Greece. The instrument is ready and after the first light tests, it started to conduct a large-area sky survey that will provide maps at 1 arcmin resolution, in order to investigate the very extensive, but faint, line emission regions over the whole sky. Deep observations of the northern sky in the optical emission lines of Hα, [O III], and Hβ are started to be taken and it is expected the results to have significant impact on topical astronomical areas of research, e.g., subtracting the foreground for the cosmic microwave background, investigating the giant, high latitude, radio filaments from the Galactic center or very close objects in the Galactic plane of extreme angular extent etc. The instrument and its first results are presented here.

Following the discovery of a long trail behind the planetary nebula HFG1 (Boumis et al. 2009), we performed single- and multi-slits high-resolution echelle spectroscopy covering both the bow-shock and the long tail of this PN. Furthermore, we performed 2-D hydrodynamical simulations of the cometary structure of this PN. Both the kinematic and modeling results are presented here.

We present high-dispersion spectroscopic data of the compact planetary nebula Vy 1-2, where high expansion velocities up to 100 km s−1 are found in the Hα, [N ii] and [O iii] emission lines. Hubble Space Telescope images reveal a bipolar structure. Vy 1-2 displays a bright ring-like structure with a size of 2.4 arcsec × 3.2 arcsec and two faint bipolar lobes in the east–west direction. A faint pair of knots is also found, located almost symmetrically on opposite sides of the nebula at position angle = 305°. Furthermore, deep low-dispersion spectra are also presented and several emission lines are detected for the first time in this nebula, such as the doublet [Cl iii] 5517, 5537, [K iv] 6101, C ii 6461 and the doublet C iv 5801, 5812Å. By comparison with the solar abundances, we find enhanced N, depleted C and solar O. The central star must have experienced the hot-bottom burning (CN-cycle) during the second dredge-up phase, implying a progenitor star of M ≥ 3 M⊙. The very low C/O and N/O abundance ratios suggest a likely post-common envelope close binary system. A simple spherically symmetric geometry with either a blackbody or an H-deficient stellar atmosphere model is not able to reproduce the ionization structure of Vy 1-2. The effective temperature and luminosity of its central star indicate a young nebula located at a distance of ∼9.7 kpc with an age of ∼3500 yr. The detection of stellar emission lines, C ii 6461, the doublet C iv λλ 5801, 5812 and O iii 5592 Å, emitted from an H-deficient star, indicates the presence of a late-type Wolf–Rayet or a WEL-type central star.

The Etched Hourglass Nebula is a typical tight-waisted, asymmetric, bipolar Planetary Nebula (PN). Here we consider near infra-red imagery, infra-red and long-slit narrowband spectroscopy and morpho-kinematic modelling with the view of understanding the structure of the nebula in terms of its ionisation along different directions, the origins of the extreme bipolar shaping and the effect of the off-centre central star. A series of infra-red images of MyCn 18, obtained using NACO (Naos-Conica) on ESO’s VLT (UT4) telescope, shows the full extent of the main hourglass shell and the finely detailed features of the nebula. Two-micron ISAAC spectra from a slit position intersecting the narrow waist of the nebula demonstrate that the ionised gas resides closer to the centre of the nebula than the molecular emission. The nebula is clearly ionisation-bounded in this central direction, in contrast to the open ends of the hourglass structure. The shape and structure of MyCn 18 was reconstructed using a morpho-kinematic code to better describe the nebula’s morphology. The putative central star, the much smaller ‘inner hourglass’, and the main nebulosity are somewhat offset from the geometric centre of the nebula, indicating the possibility of a binary companion. The role of exoplanets is also considered in the breaking of spherical symmetry of MyCn 18.

Since the discovery by Lopez, Vasquez and Rodriguez of the giant lobes projecting from the otherwise innocuous planetary nebula, KjPn 8, it has been imperative to obtain a robust distance (D) determination. This has now been achieved by comparing an image of the lobes taken in 2011 with the Greek Aristarchos telescope with that (POSSI-R) obtained in 1954: the baseline for expansive proper motions has therefore being extended to 57 yr. These proper motions, combined with previous radial velocity measurements and tilt of the most energetic outflow with respect to the sight line, as determined from HST imagery of the nebular core, give D = 1.8 ± 0.3 kpc. This value then lets the kinetic energy (approx 1047 erg) of the most recent and energetic outflow to be determined. It could be significant that this energy is consistent with an Intermediate Luminosity Optical Transient (ILOT) origin of the latest ejection as proposed for other similar objects by Soker and Kashi.