Astronomy & Astrophysics

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Table 2: Spectral properties of the 13 brightest X-ray point sources. Pre-empting Sect. 3, the upper panel presents those sources associated with the cluster, while the lower panel contains those sources associated with foreground objects. Source IDs are given in Col. 2, the definitions of Cols. 3-5 given in Sect. 2.4 and the normalisation is related to the emission measure by $10^{-14}/4\pi D^2 \times \int n_{\rm e} n_{\rm h} {\rm d}V$ cm^-5. Finally, the observed and un-absorped 0.5-8 keV fluxes are presented in Cols. 9 and 10. X-ray luminosities for individual cluster sources may be obtained by multiplying the final column by $4\pi D^2$ ; given the uncertain distance to the foreground sources we have refrained from presenting these.
Table 3: Summary of the X-ray and optical properties of the X-ray point sources with high mass stellar counterparts. Columns 1-3 summarise the X-ray nomenclature, photon counts and Hardness Ratio, noting that only 164706.2-455048 was found to be variable in these observations; we highlight this by presenting the photon count in italics. Column 4 is the number of the source on the finding chart (Fig. 6); we strongly advise that these numbers should not form the basis for a new naming convention. Column 5 contains the optical designation (sources with 2MASS or Piatti et al. (1998) designations are indicated), with Cols. 6-9 presenting relevant broadband BVRI photometry. The current spectral classifications for the counterparts are given in Col. 10, noting that for those sources for which no entry is given but for which photometric data are available, we predict a spectral classification earlier than B0.5Ia (Sect. A.3). Finally, in Col. 11 we flag those stars which Bonanos (2007) find to be Eclipsing, Periodic or Aperiodic photometric variables.
Table 4: Limits on the count rates from spectroscopically-identified stars. Limits on the luminosities can be derived by noting that 1 count is equivalent to $2\times 10^{30}$ erg s^-1 for a 3 keV plasma at D=5 kpc, and $1\times 10^{31}$ erg s^-1 for a 0.5 keV plasma. As with Table 3, we also flag the photometric variables identified by Bonanos (2007) in Col. 6. Note that list is incomplete due to WR J and K being too close to nearby X-ray sources for meaningful limits to be determined.
Table 1: Catalogue of the properties of the 241 X-ray point sources detected in the 2 epochs of observations. Column 1 provides the X-ray identifier, Cols. 2 and 3 the Right Ascension and Declination of the source and Cols. 4 and 5 the angular offset from the aim point of the observations and the positional uncertainty. Columns 6-9 list the detector live time, net counts, hardness ratio (as defined in Sect. 2.4) and X-ray flux respectively, for each source. Column 10 indicates source variability, if present, on short or long timescales (as described in Sect. 2.3). Finally, Col. 11 indicates whether an X-ray source has an optical or near-IR counterpart. The source catalogues utilised are 1: Clark et al. (2005), 2: Piatti et al. (1998), 3: the 2MASS catalogue (Cutri et al. 2003) and 4: the USNO-B1.0 survey (Monet et al. 2003). Designations for optical or near-IR counterparts for sources within the $5'\times 5'$ field centred on Wd1 are presented in Table 3.