High-Energy Stellar, Protostellar, and Protoplanetary Physics
The Formation of Stars and Planets and their High-Energy Environments
Recent research points to protostellar and pre-main sequence X-ray and energetic particle activity as crucial aspects of star and planet formation. These produce the ionization necessary for accretion to proceed in stellar systems throughout protostar evolution, and mediate both terrestrial and Jovian planet formation (Glassgold et al. 2004). X-rays from large flares reprocessed into cold iron K lines by circumstellar disks have been detected in several protostars (Imanishi et al. 2001, Tsujimoto et al. 2004). The time-dependence of the Fe K flux can be used for "reverberation mapping" of the structure of gas and dust in inner protoplanetary disks revealing gaps at the locations of inner planets in the process of formation.
A schematic illustrating the influence of stellar activity on protoplanetary disks through magnetically driven high-energy photon and particle emission. Ionizing X-rays penetrates deeply into disks, inducing MHD turbulence, which affects accretion, Jovian planet formation and migration. Terrestrial planets are believed to be formed in a disk "dead zone", which is sufficiently obscured by overlying material that ionizing X-ray photons and energetic particles cannot penetrate (From Feigelson 2003).
An illustration of the technique of reverberation mapping of protoplanetary disks. Bright flares on the central star are reprocessed by the disk and this signal is revealed in spectra in the light of the cold iron K-shell fluorescence line. The variations of the flux from this line with time can reveal the location of gaps in the disk where planets are forming.
Chandra and XMM-Newton grating spectra have detected shock-heated plasma from magnetospheric accretion from two out of the five or so CTTS studied at high resolution to date: in TW Hya (Kastner et al. 2002; Stelzer and Schmitt 2004) and BP Tau (Schmitt et al. 2005). The soft X-ray accretion signatures are high densities seen in the lines of He-like O and Ne and are completely missed at low resolution. Only a small handful of the very nearest CTTS are accessible to Chandra and XMM-Newton gratings. Constellation- X will instead probe accretion signatures at high resolution in stars up to 500 pc away, including those in the nearest regions of copious star formation such as Orion.
Refrences
Feigelson, E., 2003, IAUS, 219, 217Glassgold, A. E., Feigelson, E. D., Montmerle, T., and Wolk, S., 2004, in Workshop on Chondrites and the Protoplanetary Disk, ASP Conf. Series, 9026
Imanishi, K., Koyama, K., and Tsuboi, Y., 2001, ApJ, 557, 747
Kastner, J. H., Huenemoerder, D. P., Schulz, N. S., and Canizares, C. R., 2002, ApJ, 567, 434
Schmitt, J. H. M. M., Robrade, J., Ness, J.-U., Favata, F., and Stelzer, B., 2005, A&A, 432, L35
Stelzer, B., and Schmitt, J.H.M.M., 2004, A&A, 418, 687
Tsujimoto, M., et al., 2004, (astro-ph/0412608)
