Search Publications
Is Active Region Core Variability Age Dependent?
Warren, Harry P.; Ugarte-Urra, Ignacio
The presence of both steady and transient loops in active region cores has been reported from soft X-ray and extreme-ultraviolet observations of the solar corona. The relationship between the different loop populations, however, remains an open question. We present an investigation of the short-term variability of loops in the core of two active r…
Discovery of an Active Supermassive Black Hole in the Bulgeless Galaxy NGC 4561
Ferrarese, L.; Fiore, F.; Mathur, S. +2 more
We present XMM-Newton observations of the Chandra-detected nuclear X-ray source in NGC 4561. The hard X-ray spectrum can be described by a model composed of an absorbed power law with Γ = 2.5+0.4 - 0.3 and column density NH = 1.9+0.1 - 0.2 × 1022 atoms cm-2. The absorptio…
The near-infrared detection of PSR B0540-69 and its nebula
De Luca, A.; Mignani, R. P.; Kanbach, G. +4 more
Context. The ~1700 year old PSR B0540-69 in the Large Magellanic Clouds (LMC) is considered the twin of the Crab pulsar because of its similar spin parameters, magnetic field, and energetics. PSR B0540-69 (V ~ 22.5) is also one of the very few pulsars for which both optical pulsations and polarised emission have been measured. Its optical spectrum…
Temporal variations in the acoustic signal from faculae
Karoff, C.
The integrated brightness of the Sun shows variability on time-scales from minutes to decades. This variability is mainly caused by pressure mode oscillations, by granulation and by dark spots and bright faculae on the surface of the Sun. By analysing the frequency spectrum of the integrated brightness, we can obtain greater knowledge about these …
Planetary transit candidates in the CoRoT LRa01 field
Mazeh, T.; Aigrain, S.; Alapini, A. +70 more
Context. CoRoT is a pioneering space mission whose primary goals are stellar seismology and extrasolar planets search. Its surveys of large stellar fields generate numerous planetary candidates whose lightcurves have transit-like features. An extensive analytical and observational follow-up effort is undertaken to classify these candidates.
A…
On the Nature of the Progenitor of the Type Ia SN2011fe in M101
Liu, Jifeng; Wang, Tao; Di Stefano, Rosanne +1 more
The explosion of a Type Ia supernova, SN2011fe, in the nearby Pinwheel galaxy (M101 at 6.4 Mpc) provides an opportunity to study pre-explosion images and search for the progenitor, which should consist of a white dwarf (WD), possibly surrounded by an accretion disk, in orbit with another star. We report on our use of deep Chandra observations and …
Observations of classical and recurrent novae with X-ray gratings
Orio, M.
X-ray grating spectra have opened a new window on nova physics. High signal-to-noise spectra have been obtained for 12 novae after the outburst in the last 13 years, with the Chandra and XMM-Newton gratings. They offer the only way to probe the temperature, effective gravity and chemical composition of the hydrogen burning white dwarf before it tu…
Solar-like oscillations in the G9.5 subgiant β Aquilae
Grundahl, F.; Kjeldsen, H.; Leccia, S. +3 more
Context. An interesting asteroseismic target is the G9.5 IV solar-like star β Aql. This is an ideal target for asteroseismic investigations, because precise astrometric measurements are available from Hipparcos that greatly help in constraining the theoretical interpretation of the results. The star was observed during six nights in August 2009 by…
Radiative transfer analyses of Titan's tropical atmosphere
Tomasko, Martin G.; Griffith, Caitlin A.; Penteado, Paulo F. +2 more
Titan's optical and near-IR spectra result primarily from the scattering of sunlight by haze and its absorption by methane. With a column abundance of 92 km amagat (11 times that of Earth), Titan's atmosphere is optically thick and only ∼10% of the incident solar radiation reaches the surface, compared to 57% on Earth. Such a formidable atmosphere…
Distance to northern high-latitude HI shells
Lallement, R.; Puspitarini, L.
Context. A detailed three-dimensional (3D) distribution of interstellar matter in the solar neighborhood is increasingly necessary. It would allow a more realistic computation of photons and cosmic rays propagation, which is of prime importance for microwave and gamma-ray background emission interpretation, as well as a better understanding of the…