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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.
| The spectral variability of DR Tauri
We present a series of CCD spectra of the very active T Tauri star DRTau. The amount of veiling of the stellar absorption lines was unusuallylarge and highly variable on timescales as short as a few hours. InverseP Cygni profiles are visible over a wide range of line excitation: Na ID, Fe II, H-beta, and even He I A5867. The equivalent widths of theemission and the inverse P Cygni absorption lines are 2 to 10 timeslarger in the high veiling state. However, the velocity structure of theinverse P Cygni lines is not affected by changes in the amount ofveiling. We find a factor of 2-3 difference in the mean temperatures ofthe veiling continuum source between the most extreme veiling states. Ifthe continuum source is an optically thick spot on the star itself, theprojected area was 60 percent of the star in the 'low' and less thanabout 30 percent in the 'high' veiling states, respectively. Theseobservations are most easily explained by magnetic accretion models,where an accretion shock is formed by matter falling freely along fieldlines from the circumstellar disk onto the star.
| Dwarf K and M stars of small proper motion found in a large spectroscopic survey
More than 2000 candidates for K and M dwarf status, generally havingproper motions that are either unknown or less than 0.2 arcsec perannum, have been identified in an objective-prism survey covering theentire sky north of declination - 25 degrees and more than 10 degreesfrom the galactic plane. More than 95 percent have no previousindication that they are dwarfs. Several dozen appear to be visualdouble stars.
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