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What obscures low-X-ray-scattering active galactic nuclei
Hönig, S. F.; Gandhi, P.; Asmus, D. +4 more
X-ray surveys have revealed a new class of active galactic nuclei (AGN) with a very low observed fraction of scattered soft X-rays, fscat <0.5 per cent. Based on X-ray modelling, these `X-ray new-type', or low observed X-ray-scattering (hereafter, `low-scattering') sources have been interpreted as deeply buried AGN with a high coveri…
The Galactic plane at faint X-ray fluxes - II. Stacked X-ray spectra of a sample of serendipitous XMM-Newton sources
Pérez-Ramírez, D.; Warwick, R. S.; Byckling, K.
We have investigated the X-ray spectral properties of a sample of 138 X-ray sources detected serendipitously in XMM-Newton observations of the Galactic plane, at an intermediate to faint flux level. We divide our sample into five subgroups according to the spectral hardness of the sources, and stack (i.e. co-add) the individual source spectra with…
Current constraints on early and stressed dark energy models and future 21 cm perspectives
Mena, Olga; Archidiacono, Maria; Lopez-Honorez, Laura
Despite the great progress of current cosmological measurements, the nature of the dominant component of the Universe, coined dark energy, is still an open question. Early dark energy is a possible candidate which may also alleviate some fine-tuning issues of the standard paradigm. Using the latest available cosmological data, we find that the 95%…
Hemispheric Distribution of Subsurface Kinetic Helicity and Its Variation with Magnetic Activity
Komm, R.; Pevtsov, A. A.; Gosain, S.
We study the hemispheric distribution of the kinetic helicity of subsurface flows in the near-surface layers of the solar convection zone and its variation with magnetic activity. We determine subsurface flows with a ring-diagram analysis applied to Global Oscillation Network Group (GONG) Dopplergrams and Dynamics Program data from the Michelson D…
Photometric studies of Abell 1664: the subtle effect a minor merger has on cluster galaxies
Pimbblet, Kevin A.; Owers, Matt S.; Jones, D. Heath +2 more
A combination of BRI photometry and archival Chandra X-ray data have been used to analyse the effects a minor merger has on the galaxy population of A1664. We utilize adaptive smoothing techniques in the 2D spatial distribution of cluster galaxies to reveal substructure ∼800 kpc south of the cluster core. We identify this substructure as most like…
Exploring Overstabilities in Saturn's A Ring Using Two Stellar Occultations
Nicholson, P. D.; Hedman, M. M.; Salo, H.
Certain regions of Saturn's rings exhibit periodic opacity variations with characteristic radial wavelengths of up to a few hundred meters that have been attributed to viscous overstabilities. The Visual and Infrared Mapping Spectrometer on board the Cassini spacecraft observed two stellar occultations of the star γ Crucis that had sufficient reso…
Colour matters: the effects of lensing on the positional offsets between optical and submillimetre galaxies in Herschel-ATLAS
Ivison, R. J.; de Zotti, G.; González-Nuevo, J. +9 more
We report an unexpected variation in the positional offset distributions between Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) submillimetre (submm) sources and their optical associations, depending on both 250-µm signal-to-noise ratio and 250/350-µm colour. We show that redder and brighter submm sources have optical ass…
Near-UV Absorption in Very Cool DA White Dwarfs
Saumon, D.; Holberg, J. B.; Kowalski, P. M.
The atmospheres of very cool, hydrogen-rich white dwarfs (WDs) (T eff < 6000 K) are challenging to model because of the increased complexity of the equation of state, chemical equilibrium, and opacity sources in a low-temperature, weakly ionized dense gas. In particular, many models that assume relatively simple models for the broade…
Discovery of a new Wolf-Rayet star and a candidate star cluster in the Large Magellanic Cloud with Spitzer
Gruendl, R. A.; Sander, A.; Hamann, W. -R. +8 more
We report the first-ever discovery of a Wolf-Rayet (WR) star in the Large Magellanic Cloud via detection of a circular shell with the Spitzer Space Telescope. Follow-up observations with Gemini-South resolved the central star of the shell into two components separated from each other by ≈2 arcsec (or ≈0.5 pc in projection). One of these components…
Revealing a new symbiotic X-ray binary with Gemini Near-infrared Integral Field Spectrograph
Bahramian, Arash; Heinke, Craig O.; Wijnands, Rudy +3 more
We use K-band spectroscopy of the counterpart to the rapidly variable X-ray transient XMMU J174445.5-295044 to identify it as a new symbiotic X-ray binary. XMMU J174445.5-295044 has shown a hard X-ray spectrum (we verify its association with an INTEGRAL/Imager on-Board the INTEGRAL Satellite 18-40 keV detection in 2013 using a short Swift/X-Ray Te…