Search Publications
Broad line emission from iron K- and L-shell transitions in the active galaxy 1H0707-495
Larsson, J.; Young, A. J.; Brandt, W. N. +14 more
Since the 1995 discovery of the broad iron K-line emission from the Seyfert galaxy MCG-6-30-15 (ref. 1), broad iron K lines have been found in emission from several other Seyfert galaxies, from accreting stellar-mass black holes and even from accreting neutron stars. The iron K line is prominent in the reflection spectrum created by the hard-X-ray…
An intermediate-mass black hole of over 500 solar masses in the galaxy ESO243-49
Godet, Olivier; Webb, Natalie A.; Barret, Didier +2 more
Ultraluminous X-ray sources are extragalactic objects located outside the nucleus of the host galaxy with bolometric luminosities exceeding 1039ergs-1. These extreme luminosities-if the emission is isotropic and below the theoretical (Eddington) limit, where the radiation pressure is balanced by the gravitational pressure-imp…
Liquid water on Enceladus from observations of ammonia and 40Ar in the plume
Young, D. T.; Ip, W. -H.; Lunine, J. I. +13 more
Jets of water ice from surface fractures near the south pole of Saturn's icy moon Enceladus produce a plume of gas and particles. The source of the jets may be a liquid water region under the ice shell-as suggested most recently by the discovery of salts in E-ring particles derived from the plume-or warm ice that is heated, causing dissociation of…
Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus
Kempf, S.; Postberg, F.; Srama, R. +5 more
Saturn's moon Enceladus emits plumes of water vapour and ice particles from fractures near its south pole, suggesting the possibility of a subsurface ocean. These plume particles are the dominant source of Saturn's E ring. A previous in situ analysis of these particles concluded that the minor organic or siliceous components, identified in many ic…
A massive hypergiant star as the progenitor of the supernova SN 2005gl
Gal-Yam, A.; Leonard, D. C.
Our understanding of the evolution of massive stars before their final explosions as supernovae is incomplete, from both an observational and a theoretical standpoint. A key missing piece in the supernova puzzle is the difficulty of identifying and studying progenitor stars. In only a single case-that of supernova SN 1987A in the Large Magellanic …
The cluster Terzan 5 as a remnant of a primordial building block of the Galactic bulge
Dalessandro, E.; Ransom, S. M.; Valenti, E. +9 more
Globular star clusters are compact and massive stellar systems old enough to have witnessed the entire history of our Galaxy, the Milky Way. Although recent results suggest that their formation may have been more complex than previously thought, they still are the best approximation to a stellar population formed over a relatively short timescale …
Two distinct sequences of blue straggler stars in the globular cluster M 30
Dalessandro, E.; Beccari, G.; Ferraro, F. R. +7 more
Stars in globular clusters are generally believed to have all formed at the same time, early in the Galaxy's history. `Blue stragglers' are stars massive enough that they should have evolved into white dwarfs long ago. Two possible mechanisms have been proposed for their formation: mass transfer between binary companions and stellar mergers result…
A high stellar velocity dispersion for a compact massive galaxy at redshift z = 2.186
van Dokkum, Pieter G.; Franx, Marijn; Kriek, Mariska
Recent studies have found that the oldest and most luminous galaxies in the early Universe are surprisingly compact, having stellar masses similar to present-day elliptical galaxies but much smaller sizes. This finding has attracted considerable attention, as it suggests that massive galaxies have grown in size by a factor of about five over the p…
Observed variations of methane on Mars unexplained by known atmospheric chemistry and physics
Lefèvre, Franck; Forget, François
The detection of methane on Mars has revived the possibility of past or extant life on this planet, despite the fact that an abiogenic origin is thought to be equally plausible. An intriguing aspect of the recent observations of methane on Mars is that methane concentrations appear to be locally enhanced and change with the seasons. However, metha…
Early assembly of the most massive galaxies
Hilton, Matt; Stott, John P.; West, Michael J. +15 more
The current consensus is that galaxies begin as small density fluctuations in the early Universe and grow by in situ star formation and hierarchical merging. Stars begin to form relatively quickly in sub-galactic-sized building blocks called haloes which are subsequently assembled into galaxies. However, exactly when this assembly takes place is a…