GS 0836–429 is a neutron star X-ray transient that displays Type-I X-ray bursts .
In 2003 and 2004 it experienced two outbursts in X-rays .
We present here an analysis of the system bursting properties during these outbursts .
We studied the evolution of the 2003–2004 outbursts in soft X-rays using RXTE ( 2.5–12 keV ; ASM ) , and in hard X-rays with INTEGRAL ( 17–80 keV , IBIS/ISGRI ) .
Using data from the JEM-X monitor onboard INTEGRAL we studied the bursting properties of the source .
We detected 61 Type-I X-ray bursts during the 2004 outburst , and confirm that the source displayed a quasi-periodic burst recurrence time of about 2.3 hours .
We improve the characterization of the fuel composition , as well as the description of the typical burst durations and fluences .
We estimate the average value of \alpha to be 49 \pm 3 .
This value together with the observed burst profiles indicate a regime of a mixed He/H runaway triggered by unstable helium ignition .
In addition , we report the detection of four series of double bursts , with burst recurrence times of \leq 20 minutes .
The secondary bursts are always shorter and less energetic than the primary and typical bursts from the source .
The measured recurrence time in double bursts is too short to allow the accretion of enough fresh material , necessary to trigger a Type-I X-ray burst .
This suggests the presence of left-over , unburned material from the preceding burst which gets ignited in a time scale of minutes .
The energies and time scales of the secondary bursts suggest a lower fraction of hydrogen compared to that estimated for the primary bursts .
The persistent emission was roughly constant during the period when the Type I X-ray bursts were detected .
We derive an average accretion rate during our observations of \dot { m } \sim 8 \% \dot { m } _ { Edd } .
The spectrum of the persistent emission during these observations can be fit with a non-thermal component , indicative for the source to be in a hard state when the INTEGRAL observations were performed .