Intermediate long X-ray bursts from the ultra-compact binary candidate SLX 1737-282

Aims. The low persistent flux X-ray burster source SLX 1737-282 is classified as an ultra-compact binary candidate. We compare the data on SLX 1737-282 with the other similar objects and attempt to derive constraints on the physical processes responsible for the formation of intermediate long bursts. Methods. Up to now only four bursts, all with duration between similar or equal to 15-30 min, have been recorded for SLX 1737-282. The properties of three of these intermediate long X-ray bursts observed by INTEGRAL are investigated and compared to other burster sources. The broadband spectrum of the persistent emission in the 3-100 keV energy band is studied with the INTEGRAL data. Results. The persistent emission is measured to be 0.5% Eddington luminosity. From the photospheric radius expansion observed during at least one burst we derive the source distance at 7.3 kpc assuming a pure helium atmosphere. The observed intermediate long burst properties from SLX 1737-282 are consistent with helium ignition at the column depth of 5-8 x 10(9) g cm(-2) and a burst energy release of similar to 10(41) erg. The apparent recurrence time of similar or equal to 86 days between the intermediate long bursts from SLX 1737-282 suggests a regime of unstable burning of a thick, pure helium layer slowly accreted from a helium donor star.