Chandra
Orion Ultradeep Project
Origins of young stellar X-rays
The astrophysical origin of X-rays in main sequence stars like the Sun is basically well-established: magnetic fields are generated by a dynamo at the boundary by rotational shear between the radiative and convective zones, rise bouyantly to the surface where convective motions twist the field lines until violent reconnection events (similar to an electrical short circuit) occur resulting in a burrst of X-rays. Magnetic activity is strongly correlated with stellar rotation in main sequence stars.
Here we plot the fractional emission of X-ray emission against rotational period for hundreds of COUP stars (filled circles) and main sequence stars (open squares; our Sun is the large circles). We see totally different behavior in the two samples: the COUP stars do not show the drop-off in magnetic activity as stars rotate more slowly. This suggests that the magnetic dynamo process is saturated in some way and/or that a different dynamo is operative in young staras that is independent of rotation. We do find that COUP X-rays are correlated with stellar mass and volume, which generally suggests a convective dynamo model.
Here we compare the X-ray plasma characteristics, plotting the temperatures of the cooler vs. the hotter components. COUP stars are filled circles, open boxes are older stars, and the circles show the Sun in its background, active region, and flare states. COUP stars are much more X-ray luminous and hotter than other stars, but otherwise follow the same trend in plasma properties
The full paper on COUP X-ray origins is:
The Origin of T Tauri X-ray Emission: New Insights from the Chandra Orion Ultradeep Project
Thomas Preibisch, Yong -Cheol Kim, Fabio Favata, Eric D. Feigelson, Ettore Flaccomio, Konstantin Getman, Giusi Micela, Salvatore Sciortino, Keivan Stassun, Beate Stelzer, Hans Zinnecker
Back to the COUP home page
Origins of young stellar X-rays
The astrophysical origin of X-rays in main sequence stars like the Sun is basically well-established: magnetic fields are generated by a dynamo at the boundary by rotational shear between the radiative and convective zones, rise bouyantly to the surface where convective motions twist the field lines until violent reconnection events (similar to an electrical short circuit) occur resulting in a burrst of X-rays. Magnetic activity is strongly correlated with stellar rotation in main sequence stars.
Here we plot the fractional emission of X-ray emission against rotational period for hundreds of COUP stars (filled circles) and main sequence stars (open squares; our Sun is the large circles). We see totally different behavior in the two samples: the COUP stars do not show the drop-off in magnetic activity as stars rotate more slowly. This suggests that the magnetic dynamo process is saturated in some way and/or that a different dynamo is operative in young staras that is independent of rotation. We do find that COUP X-rays are correlated with stellar mass and volume, which generally suggests a convective dynamo model.
Here we compare the X-ray plasma characteristics, plotting the temperatures of the cooler vs. the hotter components. COUP stars are filled circles, open boxes are older stars, and the circles show the Sun in its background, active region, and flare states. COUP stars are much more X-ray luminous and hotter than other stars, but otherwise follow the same trend in plasma properties
The full paper on COUP X-ray origins is:
The Origin of T Tauri X-ray Emission: New Insights from the Chandra Orion Ultradeep Project
Thomas Preibisch, Yong -Cheol Kim, Fabio Favata, Eric D. Feigelson, Ettore Flaccomio, Konstantin Getman, Giusi Micela, Salvatore Sciortino, Keivan Stassun, Beate Stelzer, Hans Zinnecker
Back to the COUP home page