Prof Patrick Roche

Abstract:

Echelle spectroscopy of [Si VI] 1.96 μm, [Mg VIII] 3.03 μm, and [Ar VI] 4.53 μm, using UKIRT+CGS4, shows the line pro les in PN NGC 6302 are singly peaked and unresolved even at R ∼ 20 000, with line widths less than 22 kms-1. A photoionized structure is evidenced by spatial and velocity stratification as a function of ionization potential. But a variety of models, with density and Te gradients, reproduce the spectrum equally well. Preliminary analysis of the 3000-10000 Å echellogram of NGC 6302, acquired at R ∼ 80 000 using VLT+UVES, confirms the stratified nebular structure, but yields intriguing results concerning the line profiles: [Ne V] 3426 Å is broader than [Ne IV] 4723 Å. These observations rule out the existence of an evacuated cavity, or hot bubble, at least on 1″ and 3 km s-1 scales. We do not confirm the broad wings in [Ne V] 3426 Å reported by Meaburn & Walsh (1980).

Abstract:

In 1996, it was proposed to build a near-infrared imager for the 3.8-m UK Infrared Telescope in Hawaii, to exploit the 1024 pixel format detectors that were then becoming available. In order to achieve a fast delivery, the instrument was kept simple and existing designs were reused or modified where possible. UFTI was delivered within 2.5 years of the project start. The instrument is based around a 1k Rockwell Hawaii detector and a LSR Astrocam controller and uses the new Mauna Kea optimised J,H,K filter set along with I and Z broad-band filters and several narrow-band line filters. The instrument is cooled by a CTI cry-cooler, while the mechanisms are operated by cold, internal, Bergelahr stepping motors. On UKIRT it can be coupled to a Fabry-Perot etalon for tunable narrow-band imaging at K, or a waveplate for imaging polarimetry through 1-2.5μm; the cold analyser is a Barium Borate Wollaston prism. UFTI was designed to take full advantage of the good image quality delivered by UKIRT on conclusion of the upgrades programme, and has a fine scale of 0.09 arcsec/pixel. It is used within the UKIRT observatory environment and was the first instrument integrated into ORAC, the Observatory Reduction and Acquisition Control System. Results obtained during instrument characterisation in the lab and over the last 3 years on UKIRT are presented, along with performance figures. UFTI has now been used on UKIRT for several hundred nights, and aspects of instrument performance are discussed.

Abstract:

We present the results of an attempt to detect the hottest 'hot Jupiter' planets directly in the thermal infrared. A simple method based upon high signal-to-noise ratio spectroscopy of the central star at low spectral resolution is described. In the 2-4 μm region the contrast ratio between planet and star is expected to be relatively low and the planetary spectrum should appear as a faint signal on top of the stellar spectrum, distinguished by edges of H2O absorption. No water edges were found to 3σ limits of one part in a few hundred in each case. These upper limits are compared with the irradiated planetary atmosphere models of Barman, Hauschildt & Allard to derive upper limits on the size of the hot Jupiters, which are expected to be somewhat larger than Jupiter. If reasonably strong H2O absorption occurs in these objects then typical upper limits of R < 3 RJup are derived, the precision being limited by the stability of telluric transmission. Only a modest improvement in precision is needed (e.g. with space-based instruments) to reach the range of greatest interest (1 < R < 2 RJup).