- Ponti, G;
- Bianchi, S;
- Muñoz-Darias, T;
- De Marco, B;
- Dwelly, T;
- Fender, RP;
- Nandra, K;
- Rea, N;
- Mori, K;
- Haggard, D;
- Heinke, CO;
- Degenaar, N;
- Aramaki, T;
- Clavel, M;
- Goldwurm, A;
- Hailey, CJ;
- Israel, GL;
- Morris, MR;
- Rushton, A;
- Terrier, R
AX J1745.6-2901 is a high-inclination (eclipsing) neutron star Low Mass X-ray
Binary (LMXB) located less than ~1.5 arcmin from Sgr A*. Ongoing monitoring
campaigns have targeted Sgr A* frequently and these observations also cover AX
J1745.6-2901. We present here an X-ray analysis of AX J1745.6-2901 using a
large dataset of 38 XMM-Newton observations, including eleven which caught AX
J1745.6-2901 in outburst. Fe K absorption is clearly seen when AX J1745.6-2901
is in the soft state, but disappears during the hard state. The variability of
these absorption features does not appear to be due to changes in the ionizing
continuum. The small Kalpha/Kbeta ratio of the equivalent widths of the Fe xxv
and Fe xxvi lines suggests that the column densities and turbulent velocities
of the absorbing ionised plasma are in excess of N_H ~ 10^23 cm^-2 and v_turb
>~ 500 km s^-1. These findings strongly support a connection between the wind
(Fe K absorber) and the accretion state of the binary. These results reveal
strong similarities between AX J1745.6-2901 and the eclipsing neutron star
LMXB, EXO 0748-676, as well as with high-inclination black hole binaries, where
winds (traced by the same Fe K absorption features) are observed only during
the accretion-disc-dominated soft states, and disappear during the hard states
characterised by jet emission.