We report on the results of INTEGRAL observations of the neutron star low mass X-ray binary SAX J1810.8-2609 during its latest active phase in August 2007 .
The current outburst is the first one since 1998 and the derived luminosity is 1.1 - 2.6 ~ { } \times~ { } 10 ^ { 36 } erg s ^ { -1 } in the 20–100 keV energy range .
This low outburst luminosity and the long-term time-average accretion rate of \sim~ { } 5 \times 10 ^ { -12 } { M } _ { \sun } yr ^ { -1 } suggest that SAX J1810.8–2609 is a faint soft X-ray transient .
During the flux increase , spectra are consistent with a thermal Comptonization model with a temperature plasma of kT _ { e } \sim 23-30 keV and an optical depth of \tau \sim 1.2-1.5 , independent from luminosity of the system .
This is a typical low hard spectral state for which the X-ray emission is attributed to the upscattering of soft seed photons by a hot , optically thin electron plasma .
During the decay , spectra have a different shape , the high energy tail being compatible with a single power law .
This confirm similar behavior observed by BeppoSAX during the previous outburst , with absence of visible cutoff in the hard X-ray spectrum . INTEGRAL /JEM-X instrument observed four X-ray bursts in Fall 2007 .
The first one has the highest peak flux ( \approx 3.5 ~ { } Crab in 3–25 keV ) giving an upper limit to the distance of the source of about 5.7 kpc , for a L _ { Edd } \approx 3.8 \times 10 ^ { 38 } erg s ^ { -1 } .
The observed recurrence time of \sim 1.2 days and the ratio of the total energy emitted in the persistent flux to that emitted in the bursts ( \alpha \sim 73 ) allow us to conclude that the burst fuel was composed by mixed hydrogen and helium with X \geq 0.4 .