Astronomy & Astrophysics

All Figures

$\begin{figure} \par\resizebox{\hsize}{!}{\includegraphics[angle=-90,width=6.5cm]{1932fig1.ps}}\end{figure}$ Figure 1: Target field of our monitoring campaign. The borders of our field of view are shown as solid lines. All VLM candidates in this region, selected by multi-filter photometry, are shown with large dots. The bright star $\epsilon$ Ori is located close to the lower left corner of the field.
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In the text

$\begin{figure} \par\resizebox{7.9cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932fig2.ps}}\end{figure}$ Figure 2: Sampling of the time series in the $\epsilon$ Ori field. Plotted is the non-integer fraction of the observing time vs. the observing time.
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In the text

$\begin{figure} \par\resizebox{8.1cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932fig3.ps}}\end{figure}$ Figure 3: Root mean square of the light curves in the $\epsilon$ Ori field vs. I-band magnitude for one CCD. The solid line is the median rms. The values for the reference stars in the relative calibration process are marked with filled squares.
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In the text

$\begin{figure} \par\resizebox{8.0cm}{!}{\includegraphics[angle=-90,width=6.5cm]{... ...ebox{8.0cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932fig5.ps}}\end{figure}$ Figure 4: Colour-magnitude diagrams (CMD) for objects in our $\epsilon$ Ori field. Probable cluster members are marked with filled squares. Error bars indicate typical photometry errors for the candidates. Left panel: (I, R-I) CMD with the separation line between candidates and field stars shown as straight line. The dashed lines indicate the positions of isochrones of Baraffe et al. (1998) for 3 Myr ( right), 5 Myr ( middle), 10 Myr ( left). Right panel: (J, J-H) CMD for the candidates constructed from 2MASS data. The marked outlier was excluded from the candidate list. The three isochrones are nearly indistinguishable.
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In the text

$\begin{figure} \par\resizebox{8cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932fig6.ps}}\end{figure}$ Figure 5: Simulated (I, R-I) CMD for a 1 sq. deg. field centred on $\epsilon$ Ori. The solid lines shows the 5 Myr Baraffe et al. (1998) isochrone. All objects in a 0.3 mag wide band around this line are marked as larger dots.
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In the text

$\begin{figure} \par\resizebox{5.5cm}{!}{\includegraphics[angle=-90,width=6.5cm]{... ...zebox{5.5cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932ts6.ps}}\end{figure}$ Figure 6: Light curves of objects with high-amplitude, partly irregular variations. Five panels show the complete light curves for objects Nos. 51, 63, 87, 104, 120, which show strong variations on timescales of a few hours. The lower right panel shows a part of the light curve of object No. 87, whose brightness varies very rapidly on timescales below one hour. Plotted are only the data points for the third observing night.
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In the text

$\begin{figure} \par\resizebox{8.2cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932ts7.ps}}\end{figure}$ Figure 7: Flare event in the light curve of object No. 45. Shown are only the data points from the 20th December, the complete light curve is plotted in Fig. 8.
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In the text

$\begin{figure} \par\resizebox{5.5cm}{!}{\includegraphics[angle=-90]{1932ph1.ps}}... ...{5mm} \resizebox{5.5cm}{!}{\includegraphics[angle=-90]{1932ph15.ps}}\end{figure}$ Figure 8: Phased light curves for the detected periodicities (part 1). At the top of the diagrams we give the object number and the period from Table 1.
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In the text

$\begin{figure} \par\resizebox{5.5cm}{!}{\includegraphics[angle=-90]{1932ph16.ps}... ...5mm} \resizebox{5.5cm}{!}{\includegraphics[angle=-90]{1932ph30.ps}}\end{figure}$ Figure 9: Phased light curves (part 2).
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In the text

$\begin{figure} \par\resizebox{7.8cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932fig7.ps}}\end{figure}$ Figure 10: Deviation between real and detected period for a sample of periods with amplitude-to-noise ratio of 2.5, which is typical for our detected periods. The dotted line corresponds to a period error of 10%. Our period search is highly reliable up to periods of 110 h.
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In the text

$\begin{figure} \par\resizebox{8cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932fig8.ps}}\end{figure}$ Figure 11: (H-K, J-H) colour-colour diagram for the $\epsilon$ Ori targets constructed from 2MASS data: the solid line is the 5 Myr isochrone of Baraffe et al. (1998). The dotted lines mark the extinction path, the arrow indicates a visual extinction of 1 mag. The five highly variable objects are marked with a square. For two of them, which clearly appear to be reddened, we over-plot their photometry errors.
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In the text

$\begin{figure} \par\resizebox{8.3cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932fig9.ps}}\end{figure}$ Figure 12: Period-mass relationship for the $\epsilon$ Ori cluster. The crosses are the periods measured in this study. Filled squares mark the median period for the mass bins $0<M\le 0.1~M_{\odot}$ , $0.1<M \le 0.2~M_{\odot}$ , and $0.2<M\le 0.3~M_{\odot}$ . The horizontal lines are the quartiles for these values. The solid line shows the period-mass-relationship for the ONC, as derived by Herbst et al. (2001).
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In the text

$\begin{figure} \par\resizebox{8cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932fig0.ps}}\end{figure}$ Figure 13: Period-mass relationship for the $\epsilon$ Ori and the Trapezium cluster in comparison with the breakup period (dashed line). The filled squares show the median period from our $\epsilon$ Ori sample for the mass bins $0<M\le 0.1~M_{\odot}$ , $0.1<M \le 0.2~M_{\odot}$ , and $0.2<M\le 0.3~M_{\odot}$ . Horizontal lines are the quartiles for these bins. The solid line is the period-mass relationship for the Trapezium cluster (Herbst et al. 2001).
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In the text

$\begin{figure} \par\resizebox{\hsize}{!}{\includegraphics[angle=-90,width=6.5cm]{1932fig1.ps}}\end{figure}$	Figure 1: Target field of our monitoring campaign. The borders of our field of view are shown as solid lines. All VLM candidates in this region, selected by multi-filter photometry, are shown with large dots. The bright star $\epsilon$ Ori is located close to the lower left corner of the field.
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$\begin{figure} \par\resizebox{7.9cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932fig2.ps}}\end{figure}$	Figure 2: Sampling of the time series in the $\epsilon$ Ori field. Plotted is the non-integer fraction of the observing time vs. the observing time.
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$\begin{figure} \par\resizebox{8.1cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932fig3.ps}}\end{figure}$	Figure 3: Root mean square of the light curves in the $\epsilon$ Ori field vs. I-band magnitude for one CCD. The solid line is the median rms. The values for the reference stars in the relative calibration process are marked with filled squares.
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$\begin{figure} \par\resizebox{8cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932fig6.ps}}\end{figure}$	Figure 5: Simulated (I, R-I) CMD for a 1 sq. deg. field centred on $\epsilon$ Ori. The solid lines shows the 5 Myr Baraffe et al. (1998) isochrone. All objects in a 0.3 mag wide band around this line are marked as larger dots.
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$\begin{figure} \par\resizebox{8.2cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932ts7.ps}}\end{figure}$	Figure 7: Flare event in the light curve of object No. 45. Shown are only the data points from the 20th December, the complete light curve is plotted in Fig. 8.
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$\begin{figure} \par\resizebox{5.5cm}{!}{\includegraphics[angle=-90]{1932ph1.ps}}... ...{5mm} \resizebox{5.5cm}{!}{\includegraphics[angle=-90]{1932ph15.ps}}\end{figure}$	Figure 8: Phased light curves for the detected periodicities (part 1). At the top of the diagrams we give the object number and the period from Table 1.
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$\begin{figure} \par\resizebox{5.5cm}{!}{\includegraphics[angle=-90]{1932ph16.ps}... ...5mm} \resizebox{5.5cm}{!}{\includegraphics[angle=-90]{1932ph30.ps}}\end{figure}$	Figure 9: Phased light curves (part 2).
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$\begin{figure} \par\resizebox{7.8cm}{!}{\includegraphics[angle=-90,width=6.5cm]{1932fig7.ps}}\end{figure}$	Figure 10: Deviation between real and detected period for a sample of periods with amplitude-to-noise ratio of 2.5, which is typical for our detected periods. The dotted line corresponds to a period error of 10%. Our period search is highly reliable up to periods of 110 h.
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