All Figures

$\begin{figure} \par\includegraphics[width=8.7cm,clip]{figs/Hb281_CaHK_SpMic-HD155885amplcoresCaHK-Heps_sLSD.ps}\end{figure}$ Figure 1: A spectrum of BO Mic (rotation phase 0.306, gray broad-lined spectrum), approximately fitted by a rotationally broadened template spectrum. The fit is rendered in black, the broadening function is shown in the small inset panel. The narrow-lined template spectrum was generated from an observed K-dwarf spectrum by massively amplifying its Ca H, Ca K and H $_\epsilon$ emission cores. See text for details.
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In the text

$\begin{figure} \par\includegraphics[width=6.3cm,clip]{figs/Hb281_CaKcore_SpMic-1stminmax.eps} \end{figure}$ Figure 2: Variations of the Ca K line core observed for BO Mic during two stellar rotations. The symbols show the maximum ( $\times$ ) and minimum ( +) flux observed at each radial velocity $v_\mathsf{rad}$ ; note that neither the minimum nor the maximum profile have been observed at a single phase. The upper red/gray line shows one sample profile from the time series with a typical SNR (phase 0.616). The lower blue/gray profile shows a fit to the minimum profile representing a uniform surface distribution of emission features, subjected to a linear limb brightening.
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In the text

$\begin{figure} \par\includegraphics[width=17cm,clip]{figs/Hb281_CaK-minprof_1st_55-110deg_90-300_incl3x2nd.ps} \end{figure}$ Figure 3: Residual Ca K core profile variations of BO Mic. The continuous profiles cover one complete stellar rotation, observed on 2002 August 2; the dotted lines show three sample profiles observed on August 7 for comparison. The rotation phase is given right of each graph which shows the difference of the observed profile to the minimum profile plotted in Fig. 2. Subsequent profiles are shifted by 0.24 in flux. The symbols mark the radial velocity of tentative features fixed on the stellar surface. Note that the squares are not associated with any discernible migrating deformations of the profiles, see text.
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In the text

$\begin{figure} \par\includegraphics[width=7.6cm,clip]{figs/Hb281_EWCaK_lc.ps} \end{figure}$ Figure 4: Equivalent width variations $EW_{\mathsf{CaK}}$ of the CaK core emission ( +) and the photospheric brightness ( $\diamond$ ) of BO Mic on 2002 August 2, as a function of rotation phase. Lacking strictly simultaneous photometry to our spectral observations, the photospheric brightness has been calculated from our Doppler images (WSW 2005). A value of $EW_{\mathsf{CaK}}=0$ would correspond to the minimum profile shown in Fig. 2.
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In the text