... Chandra[*]
Full Tables 1-3 are only available in electronic form at http://www.aanda.org 
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... HST-STIS[*]
Data from Hubble Space Telescope (HST) with the Space Telescope Imaging Spectrograph (STIS). 
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... EPIC[*]
European Photon Image Camera has about six times less spatial resolution than Chandra ACIS-I camera. 
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... 2006 August 31[*]
Observation start date is JD 273 350 372.4528. 
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... WFPCII[*]
Hubble Space Telescope - Wide Filed Planetary Camera 2. 
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... CIAO 3.3.0.1[*]
http://cxc.harvard.edu/ciao/ 
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... PWDetect[*]
See http://www.astropa.unipa.it/progetti_ricerca/PWDetect 
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... noise[*]
This last quantity was determined from extensive simulations of source-free fields (see Damiani et al. 1997a). 
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...=2.0 keV)[*]
http://asc.harvard.edu/ciao/download/doc/expmap_intro.ps 
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... FOV[*]
See reasons of this choice in Albacete Colombo et al. (2007). 
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... afterglow[*]
Afterglow is defined as the residual charge from the interaction of a cosmic ray with the CCD. If afterglow events are not removed from the data, they can result in the spurious ``detection'' of faint sources. 
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... TARA[*]
http://www.astro.psu.edu/xray/docs/TARA/ 
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... FTOOLS[*]
http://heasarc.gsfc.nasa.gov/docs/software/ftools/ 
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... PWDetect[*]
PWDetect assumes a symmetric PSF. 
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... positions[*]
Please follow Acis-Extract technical procedures at website http://www.astro.psu.edu/xray/docs/TARA/ae_users_guide 
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... convention[*]
http://cxc.harvard.edu/cdo/scipubs.html 
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... (PSC)[*]
See http://www.ipac.caltech.edu/2mass 
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... objects[*]
We note that the 2MASS catalog appears to have a ``hole'' around $\eta $ Carinae ($\sim $1.5 arcmin radius). 
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... respectively[*]
The adopted radii were computed following technical procedures presented in Albacete Colombo et al. (2007). 
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... sources[*]
Individual photometric errors of up to 0.1 mag at $K_{\rm s}$ and J-H color errors of $\sim $0.14, could results for $A_{\rm v}$ errors up to $\sim $0.7 mag. 
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... CM diagrams[*]
The choice of the J band is justified because, (i) in the presence of disk excesses, the J-band is the most representative of the photospheric emission, i.e. least affected; and (ii) the mass ranges in which the mass-luminosity relationship is degenerate are narrower than for a similar relationship in the H and $K_{\rm s}$ bands. 
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... stars[*]
This method suffers from photometry inaccuracy, distance, and age spread. Mass values should be adopted carefully and should not be considered to measure the slope of the mass function. 
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...(Luo et al. 1990)[*]
Whenever the wind velocities of two stars are not equal, shocked CWR should be subject to the rapid growth of dynamical (Kelvin-Helmholtz) instabilities, reaching the radiative cooling state. This limit becomes important for massive binaries with typical orbital periods $\leq $20 days (Antokhin et al. 2004). 
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... companion[*]
Variability like HD 93205's has been seen also on theta 2 Ori-A and has been interpreted by Schulz et al. (2006) as evidence of binary-induced reconnection. However, image reconstruction shows that hard, short-term variations are from an intermediate-mass tertiary companion at $\sim $0.3 arcsec (Harvin et al. 2002). 
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... curve[*]
Seven sources (#150, #305, #342, #388, #692, #868 and #944) appear to have $N_{\rm H}$ below 1021 cm-2, and are likely foreground stars. 
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... (CF)[*]
It was computed as the median ratio between the individual unabsorbed X-ray luminosities (from best-fit spectral models) and the source count rates. 
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... low-mass[*]
We defined the low-mass range M< 7 $M_\odot $, based on the presence of a significant convection envelope (at the adopted age) that explains X-ray emission from magnetic activity. 
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... literature[*]
In the ONC, stellar masses were computed from optical spectra, available for many stars, while $L_{\rm x}$ was obtained for many stars from an X-ray spectral analysis based on a relatively high photon statistics (Getman et al. 2005). 
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...$v_\infty^2$)[*]
Adopted values were taken from Smith (2006, Table 1). 
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...)[*]
Because of observed flare-like variability in Tr16-#5 and #11, we suspect that most of X-rays emission comes from a low-mass companion, and therefore we have discarded these sources in computing the median $L_{\rm x}$. 
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...-axis[*]
It was unresolved along the FGS x-axis down to 20 AU, suggesting an eccentric orbit. 
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Copyright ESO 2008