Determining Bolometric Corrections for BATSE Burst Observations

We compare the energy and count fluxes obtained by integrating over the finite bandwidth of BATSE with a measure proportional to the bolometric energy flux, the phi-measure, introduced by Borgonovo & Ryde. We do this on a sample of 74 bright, long, and smooth pulses from 55 GRBs. The correction factors show a fairly constant behavior over the whole sample, when the signal-to-noise-ratio is high enough. We present the averaged spectral bolometric correction for the sample, which can be used to correct flux data.Comment: 3 pages, 3 figures, to appear in AIP proc. "Gamma-Ray Burst and Afterglow Astronomy 2001" Woods Hole, Massachusett

Modelling Circumbinary Gas Flows in Close T Tauri Binaries

Young close binaries open central gaps in the surrounding circumbinary accretion disc, but the stellar components may still gain mass from gas crossing through the gap. It is not well understood how this process operates and how the stellar components are affected by such inflows. Our main goal is to investigate how gas accretion takes place and evolves in close T Tauri binary systems. In particular, we model the accretion flows around two close T Tauri binaries, V4046 Sgr and DQ Tau, both showing periodic changes in emission lines, although their orbital characteristics are very different. In order to derive the density and velocity maps of the circumbinary material, we employ two-dimensional hydrodynamic simulations with a locally isothermal equation of state. The flow patterns become quasi-stable after a few orbits in the frame co-rotating with the system. Gas flows across the circumbinary gap through the co-rotating Lagrangian points, and local circumstellar discs develop around both components. Spiral density patterns develop in the circumbinary disc that transport angular momentum efficiently. Mass is preferentially channelled towards the primary and its circumstellar disc is more massive than the disc around the secondary. We also compare the derived density distribution to observed line profile variability. The line profile variability tracing the gas flows in the central cavity shows clear similarities with the corresponding observed line profile variability in V4046 Sgr, but only when the local circumstellar disc emission was excluded. Closer to the stars normal magnetospheric accretion may dominate while further out the dynamic accretion process outlined here dominates. Periodic changes in the accretion rates onto the stars can explain the outbursts of line emission observed in eccentric systems such as DQ Tau.Comment: Accepted for publication in MNRA

Ressenyes

Obra ressenyada: Josep ABAD I SENTÍS, La vila de Sabadell davant la Guerra Patriòtica o dels Segadors (1598-1659). Sabadell: Arxiu Històric de Sabadell, 2003 ; Antoni SIMON I TARRÉS (a cura de), Cròniques de la Guerra dels Segadors. Barcelona: Fundació Pere Coromines, 2003

Ressenyes

Obres ressenyades: Luis Antonio RIBOT GARCÍA, La Monarquía de España y la guerra de Mesina (1674-1678). Madrid: Actas, 2002; Guy ROWLANDS, The Dynastic State and the Army under Louis XIV. Royal Service and Private Interest, 1661-1701. Cambridge: Cambridge University Press, 2002

Ressenyes

Index de les obres ressenyades: Antoni VILADAMOR, Història general de Catalunya (2 vols.). Edició crítica d'Eulàlia MIRALLES. Pròleg d'Eulàlia DURAN

Catalunya i Castella, 1598-1652 : "nosaltres i els altres"

Aquesta tesi ha analitzat la literatura i la iconografia de Catalunya i de Castella entre els anys 1598 i 1652, una època de grans tensions entre les institucions catalanes i la Monarquia Hispànica. L'objectiu és demostrar que les expressions artístiques poden ser fonts historiogràfiques per a l'anàlisi de les identitats col·lectives de caràcter nacional.Esta tesis ha analizado la literatura y la iconografía de Cataluña y Castilla entre los años 1598 y 1652, una época de grandes tensiones entre las instituciones catalanas y la Monarquía Hispánica. Su objetivo es demostrar que las expresiones artísticas pueden ser fuentes historiográficas para el análisis de las identidades colectivas de carácter nacional.This PhD thesis analyses the literature and iconography of Catalonia and Castile between 1598 and 1652, a period of great tensions between the Catalan institutions and the Hispanic Monarchy. Its aim is to demonstrate that these artistic expressions can be used as historiographical sources for the study of a nation's collective identity

Catalans i castellans: estereotips durant la primera meitat del segle XVII.

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Water production in comet 81P/Wild 2 as determined by Herschel/HIFI

The high spectral resolution and sensitivity of Herschel/HIFI allows for the detection of multiple rotational water lines and accurate determinations of water production rates in comets. In this Letter we present HIFI observations of the fundamental 1_(10)–1_(01) (557 GHz) ortho and 1_(11)–0_(00) (1113 GHz) para rotational transitions of water in comet 81P/Wild 2 acquired in February 2010. We mapped the extent of the water line emission with five point scans. Line profiles are computed using excitation models which include excitation by collisions with electrons and neutrals and solar infrared radiation. We derive a mean water production rate of 1.0 × 10^(28) molecules s^(−1) at a heliocentric distance of 1.61 AU about 20 days before perihelion, in agreement with production rates measured from the ground using observations of the 18-cm OH lines. Furthermore, we constrain the electron density profile and gas kinetic temperature, and estimate the coma expansion velocity by fitting the water line shapes