A decade's overview of Io's volcanic activity

Over the past decade some aspects of Io's volcanic activity have changed greatly, while others have essentially remained constant. This contrast has emerged from our study of multi-wavelength, infrared, observations of Io's thermal emission. From 1983 to 1992 we observed the disk integrated flux density of Io from the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. Our spectral coverage allows us to separate out the emission components due to volcanic thermal anomalies which are warmer than the background emission caused by solar heating. Our temporal coverage allows us to resolve individual eruptions and also to obtain the disk-integrated flux density as a function of longitude (or, equivalently, orbital phase angle). Characteristics that persisted over the decade involve Loki's location and intensity of emission, the leading hemisphere emission, and the average heat flow. The variable aspects of Io over the decade include Loki's hotter area(s) and the outbursts in the leading hemisphere

Identifying Near Earth Object Families

The study of asteroid families has provided tremendous insight into the forces that sculpted the main belt and continue to drive the collisional and dynamical evolution of asteroids. The identification of asteroid families within the NEO population could provide a similar boon to studies of their formation and interiors. In this study we examine the purported identification of NEO families by Drummond (2000) and conclude that it is unlikely that they are anything more than random fluctuations in the distribution of NEO osculating orbital elements. We arrive at this conclusion after examining the expected formation rate of NEO families, the identification of NEO groups in synthetic populations that contain no genetically related NEOs, the orbital evolution of the largest association identified by Drummond (2000), and the decoherence of synthetic NEO families intended to reproduce the observed members of the same association. These studies allowed us to identify a new criterion that can be used to select real NEO families for further study in future analyses, based on the ratio of the number of pairs and the size of strings to the number of objects in an identified association.Comment: Accepted for publication in Icarus. 19 pages including 11 figure

Bright fibrils in Ca II K

Context: Except for the Ca II resonance lines, fibrils are ubiquitously present in most high-resolution observations of chromospheric lines. Aims: We show that fibrils are also a prevailing feature in Ca II K, provided the spatial-resolution is sufficiently high. Methods: We present high spatial resolution observations of an active region in the Ca I} K line from the Swedish Solar Telescope. Through a comparison between photospheric intensity and magnetic field data, we study the connection between bright chromospheric fibrils and photospheric structures. Additionally, using Fourier analysis we study how the fibrils are linked to the observed dynamics. Results: We find that very narrow, bright fibrils are a prevailing feature over large portions of the observed field. We also find a clear connection between the fibril footpoints and photospheric magnetic features. We show that the fibrils play two distinct roles in the observed dynamics: depending on their location they can act as a canopy suppressing oscillations or they can channel low-frequency oscillations into the chromosphere. Conclusions: The Ca II K fibrils share many characteristics with fibrils observed in other chromospheric lines, but some features, such as the very small widths, are unique to these observations.Comment: To be published in A&A. High resolution version can be downloaded from: http://www.mps.mpg.de/homes/pietarila/fibrils.pd

Discovery of a powerful, transient, explosive thermal event at Marduk Fluctus, Io, in Galileo NIMS data.

Analysis of Galileo Near Infrared Mapping Spectrometer (NIMS) observations of Marduk Fluctus, a volcano on the jovian moon Io, reveals a style of volcanic activity not previously seen there – a powerful thermal event lasting only a few minutes in 1997. The thermal emission rapidly fades, suggesting extremely rapid cooling of small clasts. The duration and evolution of the explosive eruption is akin to what might be expected from a strombolian or vulcanian explosion. The presence of such events provides an additional volcanic process that can be imaged by future missions with the intent of determining lava composition from eruption temperature, an important constraint on the internal composition of Io. These data promise to be of particular use in understanding the mechanics of explosive volcanic processes on Io

What are the temperatures of T Tauri stars? - Constraints from coeval formation of young eclipsing binaries

We show how the assumption of coeval formation can be used to constrain the effective temperatures of the components of young eclipsing double-lined spectroscopic binaries. Our method extends the approach of White et al. (1999) to a two-step analysis. The first step compares evolutionary models to the observed masses and radii and selects those models that predict ages that are consistent with coeval formation. The second step then uses these models to constrain the effective temperatures. We applied the method on literature values of the stellar parameters of the eclipsing binaries RX J0529.4+0041 A and V1174 Ori and confirm that V1174 Ori A has dwarf-like temperatures at an age of 9 Myrs, while we cannot draw any conclusions for RX J0529.4+0041 A and V1174 Ori B. Considering these binaries, we find that none of the evolutionary models gives coeval solutions simultaneously in mass, radius and effective temperature.Comment: accepted for publication in A&A, sect. 7 on 24/06/2005; 7 pages + 2 appendices, 5 figures, 5 table

The final report of the independent inquiry into capital market activities of the London Borough of Hammersmith and Fulham

SIGLEAvailable from British Library Document Supply Centre- DSC:OP/LG-6893 / BLDSC - British Library Document Supply CentreGBUnited Kingdo