INTEGRAL, XMM-Newton and ESO/NTT identification of AX J1749.1-2733: An obscured and probably distant Be/X-ray binary

Context. AX J1749.1-2733 is an unclassified transient X-ray source discovered during surveys by ASCA in 1993-1999. The transient behaviour and the short and bright flares of the source have led to the idea that it is part of the recently revealed subclass of supergiant fast X-ray transients.Aims. A multi-wavelength study in NIR, optical, X-rays, and hard X-rays of AX J1749.1-2733 is undertaken in order to determine its nature.Methods. Public INTEGRAL data and our target of opportunity observation with XMM-Newton were used to study the high-energy source through timing and spectral analysis. Multi-wavelength observations in optical and NIR with the ESO/NTT telescope were also performed to search for the counterpart.Results. AX J1749.1-2733 is a new high-mass X-ray binary pulsar with an orbital period of days (or with ) and a spin period of ~66 s, parameters typical of a Be/X-ray binary. The outbursts last ~12 d. A spin-down of s yr is also observed, very likely due to the propeller effect. The most accurate X-ray position is RA (2000) and Dec . The high-energy broad-band spectrum is well-fitted with an absorbed powerlaw and a high-energy cutoff with values cm, , and keV. The only optical/NIR candidate counterpart within the X-ray error circle has magnitudes of , , , , and , which points towards a Be star located far away ($]]>8.5 kpc) and highly absorbed ( cm). The average 22-50 keV luminosity is 0.4- during the long outbursts and during the bright flare that occurred on MJD 52891 for an assumed distance of 8.5 kpc.