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High-Energy Processes in Young Stellar Objects
Observational studies of low-mass stars during their early stages ofevolution, from protostars through the zero-age main sequence, showhighly elevated levels of magnetic activity. This activity includesstrong fields covering much of the stellar surface and powerful magneticreconnection flares seen in the X-ray and radio bands. The flaring mayoccur in the stellar magnetosphere, at the star-disk interface, or abovethe circumstellar disk. Ionization from the resulting high-energyradiation may have important effects on the astrophysics of the disk,such as promotion of accretion and coupling to outflows, and on thesurrounding interstellar medium. The bombardment of solids in the solarnebula by flare shocks and energetic particles may account for variousproperties of meteorites, such as chondrule melting and spallogenicisotopes. X-ray surveys also improve our samples of young stars,particularly in the weak-lined T Tauri phase after disks havedissipated, with implications for our understanding of star formation inthe solar neighborhood.
| The Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
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