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| X-ray light curves of HD 98800 (top) and CD-33 7795 (bottom). Each point represents one orbit, or approximately 2500 s of effective observing time. The dashed lines indicate the mean count rates for each target excluding the flare events. |
HR diagram of candidate young stars. The evolutionary tracks and isochrones are from D'Antona and Mazzitelli (1994) with Alexander opacities and CM convection. The dashed line shows V = 7.8 at a distance of 50 pc, with a bolometric correction added; the Hipparcos catalog is incomplete below this level.
Proper motions of confirmed young stars, projected back in time from the stars' current positions. The tips of the arrows show the stars' positions on the sky 10^7 yr ago; the boxes show the uncertainty on the proper motion. If the stars formed together, the arrows should point toward their common place of origin. This appears not to be the case. Note that the length of the arrows represents motion over the estimated 10^7 yr ages of TW Hya and HD 98800. Young stars without known proper motions are shown with crosses. The dashed lines show the effect of 1 sigma distance uncertainties on the subtracted solar motion. The numbers represent the current distances in pc used to calculate the motions.
Last modified: Mon Jun 1 13:33:59 1998