The structure and dynamics of young star clusters: King 16, NGC 1931, NGC 637 and NGC 189

In this paper, using 2MASS photometry, we study the structural and dynamical properties of four young star clusters viz. King 16, NGC 1931, NGC 637 and NGC 189. For the clusters King 16, NGC 1931, NGC 637 and NGC 189, we obtain the limiting radii of 7', 12', 6' and 5' which correspond to linear radii of 3.6 pc, 8.85 pc, 3.96 pc and 2.8 pc respectively. The reddening values $E(B-V)$ obtained for the clusters are 0.85, 0.65--0.85, 0.6 and 0.53 and their true distances are 1786 pc, 3062 pc, 2270 pc and 912 pc respectively. Ages of the clusters are 6 Myr, 4 Myr, 4 Myr and 10 Myr respectively. We compare their structures, luminosity functions and mass functions ($\phi(M) = dN/dM \propto M^{-(1+\chi)}$) to the parameter $\tau = t_{age}/t_{relax}$ to study the star formation process and the dynamical evolution of these clusters. We find that, for our sample, mass seggregation is observed in clusters or their cores only when the ages of the clusters are comparable to their relaxation times ($\tau \geq 1$). These results suggest mass seggregation due to dynamical effects. The values of $\chi$, which characterise the overall mass functions for the clusters are 0.96 $\pm$ 0.11, 1.16 $\pm$ 0.18, 0.55 $\pm$ 0.14 and 0.66 $\pm$ 0.31 respectively. The change in $\chi$ as a function of radius is a good indicator of the dynamical state of clusters.Comment: Accepted for publication in Astrophysics & Space Scienc

Searching for star-planet magnetic interaction in CoRoT observations

Close-in massive planets interact with their host stars through tidal and magnetic mechanisms. In this paper, we review circumstantial evidence for star-planet interaction as revealed by the photospheric magnetic activity in some of the CoRoT planet-hosting stars, notably CoRoT-2, CoRoT-4, and CoRoT-6. The phenomena are discussed in the general framework of activity-induced features in stars accompanied by hot Jupiters. The theoretical mechanisms proposed to explain the activity enhancements possibly related with hot Jupiter are also briefly reviewed with an emphasis on the possible effects at photospheric level. The unique advantages of CoRoT and Kepler observations to test these models are pointed out.Comment: Invited review paper accepted by Astrophysics and Space Science, 13 pages, 5 figure

Stellar modelling of Spica, a high-mass spectroscopic binary with a β Cep variable primary component

Contains fulltext : 157952.pdf (publisher's version ) (Open Access

Pulsations Beneath the Winds: Unique Precise Photometry from MOST

Contains fulltext : 72155.pdf (publisher's version ) (Open Access)Mass Loss from Stars and the Evolution of Stellar Clusters, 29 mei 200

Strukturanalyse und Optimierung einer Vielbus Architektur zur Datenerfassung

Beschrieben wird der Entwurf eines optimierten Datenerfassungssystem fuer Streuexperimente am Speicherring COSY (COoler SYnchrotron Juelich). Das C40-System mit der Programmiersprache OCCAM-2 hat eine maximale Datenerfassungsrate von 26,66 Mbytes/s. (HP)The report describes the design of an optimized data acquisition system for scattering experiments at the COSY storage ring (COSY = COoler SYnchrotron Juelich). The C40 system uses the programming language OCCAM-2; it has a maximum data acquisition speed of 26.66 Mbytes/s. (HP)SIGLEAvailable from TIB Hannover: RA 831(3013) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman