Search results for " Rotation"

Effects of computer game playing on spatial skills

2004

Stochastic gravito-inertial modes discovered by CoRoT in the hot Be star HD 51452

2012

International audience; Context. Be stars are rapidly rotating stars with a circumstellar decretion disk. They usually undergo pressure and/or gravity pulsation modes excited by the κ-mechanism, i.e. an effect of the opacity of iron-peak elements in the envelope of the star. In the Milky Way, p-modes are observed in stars that are hotter than or equal to the B3 spectral type, while g-modes are observed at the B2 spectral type and cooler. Aims. We observed a B0IVe star, HD 51452, with the high-precision, high-cadence photometric CoRoT satellite and high-resolution, ground-based HARPS and SOPHIE spectrographs to study its pulsations in great detail. We also used the lower resolution spectra a…

Activity-rotation relation in the young cluster h Per

2015

The activity-rotation relation in PMS stars is still an open issue. To bridge the gap between the well constrained case of MS stars and the puzzling case of very young PMS stars, we studied the activity-rotation relation in the young cluster h Persei. Because of its age (˜13 Myr) h Per contains both fast and slow rotators, allowing us therefore to test the different regimes of stellar dynamo. We analyzed a deep Chandra/ACIS-I observation to constrain the activity level of h Per members. Rotational periods were derived by tet{MorauxArtemenko2013}. From the comparison of the 1002 detected X-ray sources, and the 586 h Per members with measured rotational period, we obtained a final catalog of …

CSI 2264: Simultaneous optical and X-ray variability in the pre-main sequence stars of NGC 2264

2019

Context. Pre-main sequence stars are variable sources. In diskless stars this variability is mainly due to the rotational modulation of dark photospheric spots and active regions, as in main sequence stars even if associated with a stronger magnetic activity.Aims. We aim at analyzing the simultaneous optical and X-ray variability in these stars to unveil how the activity in the photosphere is connected with that in the corona, to identify the dominant surface magnetic activity, and to correlate our results with stellar properties, such as rotation and mass.Methods. We analyzed the simultaneous optical and X-ray variability in stars without inner disks (e.g., class III objects and stars with…

The close classical T Tauri binary V4046 Sgr: Complex magnetic fields & distributed mass accretion

2011

We report here the first results of a multi-wavelength campaign focussing on magnetospheric accretion processes within the close binary system V4046 Sgr, hosting two partly-convective classical T Tauri stars of masses ~0.9 Msun and age ~12 Myr. In this paper, we present time-resolved spectropolarimetric observations collected in 2009 September with ESPaDOnS at the Canada-France-Hawaii Telescope (CFHT) and covering a full span of 7d or ~2.5 orbital/rotational cycles of V4046 Sgr. Small circularly polarised Zeeman signatures are detected in the photospheric absorption lines but not in the accretion-powered emission lines of V4046 Sgr, thereby demonstrating that both system components host lar…

Jacobi Fields, Conjugate Points

2001

Let us go back to the action principle as realized by Jacobi, i.e., time is eliminated, so we are dealing with the space trajectory of a particle. In particular, we want to investigate the conditions under which a path is a minimum of the action and those under which it is merely an extremum. For illustrative purposes we consider a particle in two-dimensional real space.

Non-stationary dynamo and magnetospheric accretion processes of the classical T Tauri star V2129 Oph

2011

We report here the first results of a multiwavelength campaign focussing on magnetospheric accretion processes of the classical T Tauri star V2129 Oph. In this paper, we present spectropolarimetric observations collected in 2009 July with ESPaDOnS at the Canada-France-Hawaii Telescope and contemporaneous photometry secured with the SMARTS facility. Circularly polarized Zeeman signatures are clearly detected, both in photospheric absorption and accretion-powered emission lines, from time-series of which we reconstruct new maps of the magnetic field, photospheric brightness and accretion-powered emission at the surface of V2129 Oph using our newest tomographic imaging tool - to be compared wi…

Positive Effects of Videogame Use on Visuospatial Competencies: The Impact of Visualization Style in Preadolescents and Adolescents

2019

Use of videogames (VGs) is almost ubiquitous in preadolescents' and adolescents' everyday life. One of the most intriguing research topics about positive effects of VG use is about the domain of visuospatial competencies. Previous research show that training with videogames enables children and adolescents to improve their scores in visuospatial tests (such as mental rotation of shapes and cubes), and that such training could overcome gender differences in these domains. Our study aimed at (1) verifying the positive effects of videogame use in the visuospatial domain both for male and female adolescents and preadolescents and (2) verifying whether the visualization style (2D or isometric 3D…