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New photometry and astrometry of the isolated neutron star RX J0720.4-3125 using recent VLT/FORS observations
Neuhäuser, R.; Schmidt, T. O. B.; Ginski, C. +3 more
Since the first optical detection of RX J0720.4-3125 various observations have been performed to determine astrometric and photometric data. We present the first detection of the isolated neutron star in the V Bessel filter to study the spectral energy distribution and derive a new astrometric position. At ESO Paranal we obtained very deep images …
Supersoft sources in M 31: Comparing the XMM-Newton deep survey, ROSAT and Chandra catalogues
Stiele, H.; Pietsch, W.; Haberl, F. +3 more
To investigate the transient nature of supersoft sources (SSSs) in
The interior of the Sun in 3-D: Beyond the spherical Sun picture
Mathis, S.
With all the results now obtained by global helioseismology, it is clear that we have to go beyond the classical spherical modelling of the Sun. In this way, it is now necessary to draw a picture that takes into account internal dynamical processes such as rotation, magnetic field, and waves from the core to the surface. This is a challenging task…
Internal magnetic fields inferred from helioseismic data
Larson, T. P.; Antia, H. M.; Basu, S. +1 more
Measuring the internal solar magnetic fields and how they change over the course of a solar cycle is one of the key aims of helioseismology. We present the results of attempts to model the global mode splitting coefficients over solar cycle 23, assuming that the frequency splitting is only due to rotation and a large-scale magnetic field. The firs…
Spectropolarimetric analysis of 3D MHD sunspot simulations
Solanki, S. K.; Borrero, J. M.; Rempel, M.
We have employed 3D non-grey MHD simulations of sunspots to compute theoretical Stokes profiles and compare the levels of circular and linear polarization in the simulations with those observed in a real sunspot. We find that the spatial distribution and average values of these quantities agree very well with the observations, although the polariz…
Center to limb variation of penumbral Stokes V profiles
Franz, M.; Schlichenmaier, R.
We investigated the horizontal and the vertical component of the Evershed flow (EF). To this end, we computed average Stokes V profiles for various velocity classes in penumbrae at different heliocentric angles. Our results show that for blueshifted profiles an additional lobe with the same polarity as the spot is present in the blue side of the a…
A new code for Fourier-Legendre analysis of large datasets: First results and a comparison with ring-diagram analysis
Thompson, M. J.; Roth, M.; Doerr, H. -P. +2 more
Fourier-Legendre decomposition (FLD) of solar Doppler imaging data is a promising method to estimate the sub-surface solar meridional flow. FLD is sensible to low-degree oscillation modes and thus has the potential to probe the deep meridional flow. We present a newly developed code to be used for large scale FLD analysis of helioseismic data as p…
Recent discoveries of supersoft X-ray sources in M 31
Stiele, H.; Pietsch, W.; Haberl, F. +9 more
Classical novae (CNe) have recently been reported to represent the major class of supersoft X-ray sources (SSSs) in the central area of our neighbouring galaxy M 31. This paper presents a review of results from recent X-ray observations of M 31 with XMM-Newton and Chandra. We carried out a dedicated optical and X-ray monitoring program of CNe and …
Quantitative solar spectroscopy
Wilhelm, K.
Quantitative solar spectroscopy must be based on calibrated instrumentation. The basic requirement of a calibration, i.e., a comparison between the instrument under test and a primary laboratory standard through appropriate procedures, will be briefly reviewed, and the application to modern space instruments will be illustrated. Quantitative measu…
Local helioseismology and the active Sun
Schunker, H.
The goal of local helioseismology is to elicit three-dimensional information about the sub-surface (or far-side) structure and dynamics of the Sun from observations of the helioseismic wave field at the surface. The physical quantities of interest include flows, sound-speed deviations and magnetic fields. However, strong surface magnetic fields in…