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Swift/XRT localisation of SAX J1324.4-6200

ATEL # 1346; P. Romano (INAF-OAB), L. Sidoli, S. Mereghetti (INAF-IASFMi)
on 2 Jan 2008; 15:29 UT
Password Certification: Pat Romano (

Subjects: X-ray, Binaries, Transients

The X-ray source SAX J1324.4-6200 was recently observed by Swift/XRT for a total of 7.4ks, on 2007-12-21 07:20:40 to 13:32:56 UT (1.6 ks onsource) and 2007-12-30 00:02:31 to 08:21:57 UT (5.8 ks onsource). The source is detected at a >5-sigma level on Dec 21 [at a count rate of CR=(2.88+/-0.53)E-02 counts s^-1], and at a 11.5-sigma level on Dec 30 [CR=(3.82+/-0.33)E-02 counts s^-1].

The position derived with Swift is RA, Dec(J2000)=201.11176, -62.02198, which is equivalent to:
RA (J2000): 13h 24m 26.81s
Dec (J2000): -62d 01' 19.1"
with an uncertainty of 3.8 arcsec (radius, 90% confidence).
This position is within the BeppoSAX and ASCA error circles (1.5 arcmin radii) reported by Angelini et al. 1998 (A&A,339,L41).

The spectrum (206 counts) can be fit in the 0.5-9 keV energy range using Cash statistics. Adopting an absorbed power-law model, we obtain a photon index of 1.24(+0.63-0.75) and a column density NH=(7.5+3.0-3.1)E22 cm^-2, in excess of the Galactic one (1.07E22 cm^-2). The observed (unabsorbed) 1-10 keV flux is 5.1E-12 (8.6e-12) ergs cm^-2 s^-1.

Since the distance is estimated to be in excess of 3.4 kpc (Angelini et al. 1998), the unabsorbed 1-10 keV luminosity is in excess of 1.1E34 erg s^-1. The Swift results are consistent with those found by Angelini et al (1998), and support a non-transient nature for this source.

We would like to thank the Swift Team for making these observations possible, in particular N. Gehrels, the duty scientists as well as the science planners.

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R. E. Rutledge , Editor
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