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Monte Carlo modelling of the propagation and annihilation of nucleosynthesis positrons in the Galaxy
Jean, P.; Ferrière, K.; Alexis, A. +1 more
Aims: We want to estimate whether the positrons produced by the β+-decay of 26Al, 44Ti, and 56Ni synthesised in massive stars and supernovae are sufficient to explain the 511 keV annihilation emission observed in our Galaxy. Such a possibility has often been put forward in the past. In a previous st…
The wind of W Hydrae as seen by Herschel. II. The molecular envelope of W Hydrae
Waters, L. B. F. M.; Menten, K. M.; Blommaert, J. A. D. L. +18 more
Context. The evolution of low- and intermediate-mass stars on the asymptotic giant branch (AGB) is mainly controlled by the rate at which these stars lose mass in a stellar wind. Understanding the driving mechanism and strength of the stellar winds of AGB stars and the processes enriching their surfaces with products of nucleosynthesis are paramou…
Very Large Baseline Array observations of Mrk 6: probing the jet-lobe connection
Hardcastle, M. J.; Croston, J. H.; O'Dea, C. P. +5 more
We present the results of high-resolution VLBI (very long baseline interferometry) observations at 1.6 and 4.9 GHz of the radio-loud Seyfert galaxy, Mrk 6. These observations are able to detect a compact radio core in this galaxy for the first time. The core has an inverted spectral index (α ^{1.6}_{4.9} = +1.0 ± 0.2) and a brightness temperature …
Galaxy formation as a cosmological tool - I. The galaxy merger history as a measure of cosmological parameters
Conselice, Christopher J.; Bluck, Asa F. L.; Mortlock, Alice +2 more
As galaxy formation and evolution over long cosmic time-scales depends to a large degree on the structure of the universe, the assembly history of galaxies is potentially a powerful approach for learning about the universe itself. In this paper, we examine the merger history of dark matter haloes based on the Extended Press-Schechter formalism as …
Investigating the sensitivity of observed spectral energy distributions to clumpy torus properties in Seyfert galaxies
Packham, C.; González-Martín, O.; Levenson, N. A. +5 more
We present nuclear spectral energy distributions (SEDs) from 1 to 18 µm of a small sample of nearby, nearly face-on and undisturbed Seyfert galaxies without prominent nuclear dust lanes. These nuclear SEDs probe the central ∼35 pc of the galaxies, on average, and include photometric and spectroscopic infrared (IR) data. We use these SEDs, th…
SHARAD soundings and surface roughness at past, present, and proposed landing sites on Mars: Reflections at Phoenix may be attributable to deep ground ice
Mellon, Michael T.; Putzig, Nathaniel E.; Phillips, Roger J. +3 more
We use the Shallow Radar (SHARAD) on the Mars Reconnaissance Orbiter to search for subsurface interfaces and characterize surface roughness at the landing sites of Viking Landers 1 and 2, Mars Pathfinder, the Mars Exploration Rovers Spirit and Opportunity, the Phoenix Mars lander, the Mars Science Laboratory Curiosity rover, and three other sites …
The Knotted Sky I: Planck constraints on the primordial power spectrum
Aslanyan, Grigor; Easther, Richard; Price, Layne C. +1 more
Using the temperature data from Planck we search for departures from a power-law primordial power spectrum, employing Bayesian model-selection and posterior probabilities. We parametrize the spectrum with n knots located at arbitrary values of logk, with both linear and cubic splines. This formulation recovers both slow modulations and sharp trans…
In situ spatiotemporal measurements of the detailed azimuthal substructure of the substorm current wedge
Wild, J. A.; Fazakerley, A. N.; Karlsson, T. +14 more
The substorm current wedge (SCW) is a fundamental component of geomagnetic substorms. Models tend to describe the SCW as a simple line current flowing into the ionosphere toward dawn and out of the ionosphere toward dusk, linked by a westward electrojet. We use multispacecraft observations from perigee passes of the Cluster 1 and 4 spacecraft duri…
Dynamic auroral storms on Saturn as observed by the Hubble Space Telescope
Brown, R. H.; Baines, K. H.; Dougherty, M. K. +14 more
We present observations of significant dynamics within two UV auroral storms observed on Saturn using the Hubble Space Telescope in April/May 2013. Specifically, we discuss bursts of auroral emission observed at the poleward boundary of a solar wind-induced auroral storm, propagating at ∼330% rigid corotation from near ∼01 h LT toward ∼08 h LT. We…
X-ray time delays in the narrow line Seyfert 1 galaxy PG 1244+026
Done, C.; Vaughan, S.; Alston, W. N.
We analyse the X-ray time-lags in the narrow line Seyfert 1 (NLS1) galaxy PG 1244+026 (MBH ∼ 107 M⊙, L/LEdd ∼ 1). The time delay between the soft (0.3-0.7 keV) and harder (1.2-4.0 keV) variations shows the well-established switch from hard lags at low frequencies to soft lags at high frequencies. The low…