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Astron. Astrophys. 339, L41-L44 (1998)

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2. Source location

1SAX J1324.4-6200 lies within [FORMULA] of the center of the dark cloud DC 306.8+0.6 (Hartley et al. 1986) which has an angular size of [FORMULA]. If 1SAX J1324.4-6200 is located behind the cloud a limit on the N[FORMULA] and distance can be derived. Rowan-Robinson et al. (1991) present a simple relation to equate the IRAS 100 µm flux to the visual extinction, with an accuracy of [FORMULA]30% for 90% of sky. From the IRAS map at 100 µm, the flux at the source location is 725 MJy sr-1 which translates (using the above relation) to N[FORMULA] atom cm-2. This value is consistent with the N[FORMULA] measured from the X-ray spectra, giving a strong indication that the absorption measured in 1SAX J1324.4-6200 is not local to the system, but due to the dark cloud. Assuming the lower limit of the derived absorption and the average cloud density, as given in Stüwe (1990) of 3000 cm-3 for a single cloud, a cloud size of [FORMULA]6 pc is derived. This is intermediate between the average cloud size for dark cloud complexes (10 pc) and for simple dark clouds (1pc, Stüwe 1990). From the angular size of DC 306.8+0.6 and the above derived size, the distance to 1SAX J1324.4-6200 is estimated to be [FORMULA]3.4 kpc, giving unabsorbed 1-10 keV luminosities of [FORMULA][FORMULA] and [FORMULA][FORMULA] erg s-1 for the BeppoSAX and ASCA observations, respectively.

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© European Southern Observatory (ESO) 1998

Online publication: October 21, 1998