Acknowledgments are only available in electronic form at http://www.edpsciences.org

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The most variable objects in this diagram are two sources that are probably background large-amplitude eclipsing binaries that do not belong to the cluster according to their ${\it BRIJHK}_{\rm s}$ magnitudes. One of these binaries shows a light curve with primary and secondary minima of similar amplitude ( $\approx$ 0.6 mag) and a period of $\approx$ 5.5 h (coordinates J2000: 05 38 19.50 -02 41 22.5).

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... $\log{(L_{{\rm H}\alpha} / L_{\rm bol})} = -2.4 \pm 0.3$

If the object were brighter in Vthan expected, e.g. V = 20.0 $\pm$ 0.5, $\log{(L_{{\rm H}\alpha} / L_{\rm bol})}$ could be as high as -2.0 $\pm$ 0.3.

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