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UNNOTICED MAGNETIC FIELD OSCILLATIONS IN THE VERY QUIET SUN REVEALED BY SUNRISE/IMaX
Martí,nez Gonzá,lez, M. J.,Asensio Ramos, A.,Manso Sainz, R.,Khomenko, E.,Martí,nez Pillet, V.,Solanki, S. K.,Ló,pez Ariste, A.,Schmidt, W.,Barthol, P.,Gandorfer, A. IOP Publishing 2011 ASTROPHYSICAL JOURNAL LETTERS - Vol.730 No.2
<P>We present observational evidence for oscillations of magnetic flux density in the quiet areas of the Sun. The majority of magnetic fields on the solar surface have strengths of the order of or lower than the equipartition field (300-500 G). This results in a myriad of magnetic fields whose evolution is largely determined by the turbulent plasma motions. When granules evolve they squash the magnetic field lines together or pull them apart. Here, we report on the periodic deformation of the shapes of features in circular polarization observed at high resolution with SUNRISE. In particular, we note that the area of patches with a constant magnetic flux oscillates with time, which implies that the apparent magnetic field intensity oscillates in antiphase. The periods associated with this oscillatory pattern are compatible with the granular lifetime and change abruptly, which suggests that these oscillations might not correspond to characteristic oscillatory modes of magnetic structures, but to the forcing by granular motions. In one particular case, we find three patches around the same granule oscillating in phase, which means that the spatial coherence of these oscillations can reach 1600 km. Interestingly, the same kind of oscillatory phenomenon is also found in the upper photosphere.</P>
Multi-site, multi-year monitoring of the oscillating Algol-type eclipsing binary CT Herculis
Lampens, P.,Strigachev, A.,Kim, S.-L.,Rodrí,guez, E.,Ló,pez-Gonzá,lez, M. J.,Vidal-Saí,nz, J.,Mkrtichian, D.,Koo, J.-R.,Kang, Y. B.,Van Cauteren, P.,Wils, P.,Kraicheva, Z.,Dimi EDP Sciences 2011 Astronomy and astrophysics Vol.534 No.2
<P>We present the results of a multi-site photometric campaign carried out in 20042008 for the Algol-type eclipsing binary system CT Her, the primary component of which displays δ Scuti-type oscillations. Our data consist of differential light curves collected in the filters B and V, which were analysed using the method of Wilson-Devinney (PHOEBE). After identifying an adequate binary model and removing the best-fit light-curve solution, we performed a Fourier analysis of the residual B and V light curves to investigate the pulsational behaviour. We confirm the presence of rapid pulsations with a main period of 27.2 min. Up to eight significant frequencies with semi-amplitudes in the range 3 to 1 mmag were detected, all of which lie in the frequency range 43.553.5 d<SUP>−1</SUP>. This result is independent of the choice of the primary’s effective temperature (8200 or 8700 K) since the light-curve models of the binary are very similar in both cases. This is yet another case of a complex frequency spectrum observed for an accreting δ Scuti-type star (after Y Cam). In addition, we demonstrate that the amplitudes of several pulsation frequencies provide evidence of variability on timescales as short as 12 years, perhaps even less. Moreover, our analysis takes into account some recently acquired spectra, from which we obtained the corresponding radial velocities for the years 20072009. Investigation of the OC diagram shows that further monitoring of the epochs of eclipse minima of CT Her will cast new light on the evolution of its orbital period.</P>