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First detection of a type I X-ray burst from AX J1754.2-2754

ATEL # 1094; I.V. Chelovekov, S.A. Grebenev (Space Research Institute, Moscow)
on 1 Jun 2007; 15:01 UT
Password Certification: S.A.Grebenev (

Subjects: X-ray, Binaries, Neutron Stars

We report the detection of an intense type I X-ray burst from the unidentified source AX J1754.2-2754 (Sakano et al. ApJS, 2002, 138, 19). The burst occurred on April 16, 2005. It was found in archival data of both the JEM-X and IBIS/ISGRI telescopes of the INTEGRAL observatory (with the S/N ratio 28 and 16 respectively). In the JEM-X 3-15 keV band the burst started at UT 22h10m25s and lasted more than 150 s showing a typical FRED profile (with a 10 s rise time and 65 s e-folding time). In the ISGRI 15-25 keV band the profile was almost symmetric with a 70 s duration and a maximum at UT 22h11m13s. The peak fluxes were equal to 2.01 and 0.85 Crab in the 3-15 and 15-25 keV bands respectively.

The position for the burst derived with JEM-X was R.A.=17h54m12s, Decl.=-27o54m58s, equinox 2000.0, error radius 1 arcmin (with ISGRI R.A.=17h54m13s, Decl.=-27o54m11s, error radius 2 arcmin) that is only 28 (42) arcsec away from the position of AXJ1754.2-2754.

There are some indications of the presence of photospheric cooling and radius expansion at the initial stage of this burst. Assuming that the Eddington luminosity for the source is equal to 2x10^{38} erg/s we can estimate its distance to be 6.8+/-0.7 kpc. The persistent emission from the source was not detected during these observations.

This is the first report of bursting behaviour from this source, suggesting a neutron star as its compact object.

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