Observations of Magnetic Elements in the Quiet Sun Internetwork

We present here the analysis of high-resolution images of the quiet Sun at disk center taken with the Solar Optical Telescope (SOT) on board Hinode in the CN bandhead (388.35 nm) and magnetograms in the Mg I line (517.27 nm). These observations are complemented with data from the Swedish 1m Solar Telescope (SST). All data sets were obtained during the Hinode/Canary Islands joint campaign (HOP 0014) in September, 2007. In particular, we investigate the morphology, radiative and magnetic properties of small-scale elements in the solar atmosphere.

Evidence of small-scale magnetic concentrations dragged by vortex motion of solar photospheric plasma

Vortex-type motions have been measured by tracking bright points in high-resolution observations of the solar photosphere. These small-scale motions are thought to be determinant in the evolution of magnetic footpoints and their interaction with plasma and therefore likely to play a role in heating the upper solar atmosphere by twisting magnetic flux tubes. We report the observation of magnetic concentrations being dragged towards the center of a convective vortex motion in the solar photosphere from high-resolution ground-based and space-borne data.

SUNRISE/IMaX observations of convectively driven vortex flows in the Sun

We characterize the observational properties of the convectively driven vortex flows recently discovered on the quiet Sun, using magnetograms, Dopplergrams and images obtained with the 1-m balloon-borne Sunrise telescope. By visual inspection of time series, we find some 3.1e-3 vortices/(Mm^2 min), which is a factor of 1.7 larger than previous estimates. The mean duration of the individual events turns out to be 7.9 min, with a standard deviation of 3.2 min. In addition, we find several events appearing at the same locations along the duration of the time series (31.6 min).

V1 non-linearities emerge from local-to-global non-linear ICA

It has been argued that the aim of non-linearities in different visual and auditory mechanisms may be to remove the relations between the coefficients of the signal after global linear ICA-like stages. Specifically, in [Schwartz and Simoncelli 01], it was shown that masking effects are reproduced by fitting the parameters of a particular non-linearity in order to remove the dependencies between the energy of wavelet coefficients.

INTEGRAL long-term monitoring of the Supergiant Fast X-ray Transient XTE J1739-302

 In the past few years, a new class of High Mass X-Ray Binaries (HMXRB)
 has been claimed to exist, the Supergiant Fast X-ray Transients (SFXT).
 These are X-ray binary systems with a compact companion orbiting a
 supergiant star which show very short and bright outbursts in a series
 of activity periods overimposed on longer quiescent periods. Only very
 recently the first attempts to model the behaviour of these sources have
 been published, some of them within the framework of accretion from clumpy

Sunday, 1 Jun 2008

Very peculiar wind from BD+53 2790, the optical counterpart to 4U 2206+54

BD+53 2790, an O9.5Vp star, is the optical counterpart to the HMXRB
 4U 2206+54. This system was classified initially as a BeX, but
 observational evidence soon stressed the need to revise this classification.
 The permanent asymmetry in the H-alpha line profiles (in contrast with
 the cyclic variations shown by Be stars), the variations in the profile
 of this line in time scales of hours (while time scales from weeks to
 months are expected in Be stars), and the lack of correlation between

Sunday, 1 Jun 2008

Discovery of slow X-ray pulsations in the high-mass X-ray binary 4U 2206+54

The source 4U 2206+54 is one of the most enigmatic high-mass X-ray binaries.
In spite of intensive searches, X-ray pulsations have not been detected in
the time range 0.001-1000 s. A cyclotron line at ~30 keV has been suggested
by various authors but never detected with significance. The stellar wind
of the optical companion is abnormally slow. The orbital period, initially
reported to be 9.6 days, disappeared and a new periodicity of 19.25 days
emerged. Our new long and uninterrupted RXTE observations allow us to search

Thursday, 1 Jan 2009

Correlated optical/X-ray variability in the high-mass X-ray binary SAX J2103.5+4545

SAX J2103.5+4545 is the Be/X-ray binary with the shortest orbital period.
It shows extended bright and faint X-ray states that last for a few hundred
days. The main objective of this work is to investigate the relationship
between the X-ray and optical variability and to characterise the spectral
and timing properties of the bright and faint states. We have found a
correlation between the spectral and temporal parameters that fit the
energy and power spectra. Softer energy spectra correspond to softer power

Thursday, 1 Jan 2009
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