  IGR J18483-0311 is a supergiant fast X-ray transient whose compact object is
located in a wide (18.5 d) and eccentric (e~0.4) orbit, which shows sporadic
outbursts that reach X-ray luminosities of ~1e36 erg/s. We investigated the
timing properties of IGR J18483-0311 and studied the spectra during bright
outbursts by fitting physical models based on thermal and bulk Comptonization
processes for accreting compact objects. We analysed archival INTEGRAL data
collected in the period 2003-2010, focusing on the observations with IGR
J18483-0311 in outburst. We searched for pulsations in the INTEGRAL light
curves of each outburst. We took advantage of the broadband observing
capability of INTEGRAL for the spectral analysis. We observed 15 outbursts,
seven of which we report here for the first time. This data analysis almost
doubles the statistics of flares of this binary system detected by INTEGRAL. A
refined timing analysis did not reveal a significant periodicity in the
INTEGRAL observation where a ~21s pulsation was previously detected. Neither
did we find evidence for pulsations in the X-ray light curve of an archival
XMM-Newton observation of IGR J18483-0311. In the light of these results the
nature of the compact object in IGR J18483-0311 is unclear. The broadband X-ray
spectrum of IGR J18483-0311 in outburst is well fitted by a thermal and bulk
Comptonization model of blackbody seed photons by the infalling material in the
accretion column of a neutron star. We also obtained a new measurement of the
orbital period using the Swift/BAT light curve.
