Multiple X-ray bursts and the model of a spreading layer of accreting matter over the neutron star surface

We report the detection of series of close type I X-ray bursts consisting of two or three events with a recurrence time much shorter than the characteristic (at the observed mean accretion rate) time of matter accumulation needed for a thermonuclear explosion to be initiated on the neutron star surface during the JEM-X/INTEGRAL observations of several X-ray bursters. We show that such series of bursts are naturally explained in the model of a spreading layer of accreting matter over the neutron star surface in the case of a sufficiently high (a(1)Euro ae(3) 1 x 10(-9) M (aS (TM)) yr(-1)) accretion rate (corresponding to a mean luminosity L (tot) ae(3) 1 x 10(37)erg s(-1)). The existence of triple bursts requires some refinement of the model-the importance of a central ring zone is shown. In the standard model of a spreading layer no infall of matter in this zone is believed to occur.