The Herschel view of GAS in Protoplanetary Systems (GASPS): First comparisons with a large grid of models

The Herschel GASPS key program is a survey of the gas phase of protoplanetary discs, targeting 240 objects which cover a large range of ages, spectral types, and disc properties. To interpret this large quantity of data and initiate self-consistent analyses of the gas and dust properties of protoplanetary discs, we have combined the capabilities of the radiative transfer code MCFOST with the gas thermal balance and chemistry code ProDiMo to compute a grid of ≈300  000 disc models (DENT). We present a comparison of the first Herschel/GASPS line and continuum data with the predictions from the DENT grid of models. Our objective is to test some of the main trends already identified in the DENT grid, as well as to define better empirical diagnostics to estimate the total gas mass of protoplanetary discs. Photospheric UV radiation appears to be the dominant gas-heating mechanism for Herbig stars, whereas UV excess and/or X-rays emission dominates for T Tauri stars. The DENT grid reveals the complexity in the analysis of far-IR lines and the difficulty to invert these observations into physical quantities. The combination of Herschel line observations with continuum data and/or with rotational lines in the (sub-)millimetre regime, in particular CO lines, is required for a detailed characterisation of the physical and chemical properties of circumstellar discs

Tracing the spiral arms in IP Pegasi

We report the analysis of time-resolved spectroscopy of IP Pegasi in outburst with eclipse mapping techniques to investigate the location and geometry of the observed spiral structures. We were able to obtain an improved view of the spiral structures with the aid of light curves extracted in velocity bins matching the observed range of velocities of the spiral arms combined with a double default map tailored for reconstruction of asymmetric structures. Two-armed spiral structures are clearly seen in all eclipse maps. The arms are located at different distances from the disc centre. The “blue” arm is farther out in the disc (R = 0.55 ± 0.05 R L1 ) than the “red” arm (R = 0.30 ± 0.05 R L1 ). There is evidence that the velocity of the emitting gas along the spiral pattern is lower than the Keplerian velocity for the same disc radius. The discrepancy is smaller in the outer arm (measured velocities 10–15 per cent lower than Keplerian) and is more significant in the inner arm (observed velocities up to 40 per cent lower than Keplerian). We measured the opening angle of the spirals from the azimuthal intensity distribution of the eclipse maps to be φ = 25◦ ± 3◦ . A comparison with similar measurements on data at different outburst stages reveals that the opening angle of the spiral arms in IP Peg decreases while the outbursting accretion disc cools and shrinks, in agreement with the expected evolution of a tidally driven spiral wave. The sub-Keplerian velocities along the spiral pattern and the clear correlation between the opening angle of the spirals and the outburst stage favors the interpretation of these asymmetric structures as tidally-induced spiral shocks

The mass and radius of the M-dwarf in the short period eclipsing binary RR Caeli

We present new photometry and spectroscopy of the eclipsing white dwarf - M-dwarf binary star RR Cae. We use timings of the primary eclipse from white-light photo-electric photometry to derive a new ephemeris for the eclipses. We find no evidence for any period change greater than Pdot/P ~ 5E-12 over a timescale of 10 years. We have measured the effective temperature of the white dwarf, T_WD, from an analysis of two high resolution spectra of RR Cae and find T_WD = (7540 +- 175)K. We estimate a spectral type of M4 for the companion from the same spectra. We have combined new spectroscopic orbits for the white dwarf and M-dwarf with an analysis of the primary eclipse and cooling models for helium white dwarfs to measure the mass and radius of the M-dwarf. The mass of the M-dwarf is (0.182 - 0.183) +- 0.013 Msun and the radius is (0.203 - 0.215) +- 0.013 Rsun, where the ranges quoted for these values reflect the range of white dwarf models used. In contrast to previous studies, which lacked a spectroscopic orbit for the white dwarf, we find that the mass and radius of the M-dwarf are normal for an M4 dwarf. The mass of the white dwarf is (0.440 +-0.022) Msun. With these revised masses and radii we find that RR Cae will become a cataclysmic variable star when the orbital period is reduced from its current value of 7.3 hours to 121 minutes by magnetic braking in 9-20 Gyr. We note that there is night-to-night variability of a few seconds in the timing of primary eclipse caused by changes to the shape of the primary eclipse. We speculate as to the possible causes of this phenomenon. (Abridged)Comment: Accepted for publication in MNRAS. The paper contains 10 figures and 3 table

Analysis of a spacecraft instrument ball bearing assembly lubricated by a perfluoroalkylether

An analysis of a spacecraft instrument ball bearing assembly, subjected to a scanning life test, was performed to determine the possible case of rotational problems involving these units aboard several satellites. The analysis indicated an ineffective transfer of a fluorinated liquid lubricant from a phenolic retainer to the bearing balls. Part of the analysis led to a novel HPLC separation method employing a fluorinated mobile phase in conjunction with silica based size exclusion columns

CIVIC LIFE: Evidence Base for the Triennial Review

This document forms part of the Equality and Human Rights Commission triennial review and covers equalities in civic life. It examines equality in political participation, freedom of language and freedom of worship. The primary aim is to map the various dimensions of equality and inequality in participation in civic and political life. We explore and review equalities, good relations and human rights in relation to civic life, and where possible we examine some of the driving forces behind the differences that we observe

Boundary Integral Equations for the Laplace-Beltrami Operator

We present a boundary integral method, and an accompanying boundary element discretization, for solving boundary-value problems for the Laplace-Beltrami operator on the surface of the unit sphere $\S$ in $\mathbb{R}^3$. We consider a closed curve ${\cal C}$ on ${\cal S}$ which divides ${\cal S}$ into two parts ${\cal S}_1$ and ${\cal S}_2$. In particular, ${\cal C} = \partial {\cal S}_1$ is the boundary curve of ${\cal S}_1$. We are interested in solving a boundary value problem for the Laplace-Beltrami operator in $\S_2$, with boundary data prescribed on \C