Discovery of X-ray burst triplets in EXO 0748-676

Abstract

[Abridged] Type-I X-ray bursts are thermonuclear flashes that take place on the surface of accreting neutron stars. The wait time between consecutive bursts is set by the time required to accumulate the fuel needed to trigger a new burst; this is at least one hour. Sometimes secondary bursts are observed, approximately 10 min after the main burst. These short wait-time bursts are not yet understood. We observed the low-mass X-ray binary and X-ray burster EXO 0748-676 with XMM-Newton for 158 h, during 7 uninterrupted observations lasting up to 30 h each. We detect 76 X-ray bursts. Most remarkably, 15 of these bursts occur in burst triplets, with wait times of 12 min between the three components of the triplet. We also detect 14 doublets with similar wait times between the two components of the doublet. The characteristics of the bursts indicate that possibly all bursts in this system are hydrogen-ignited, in contrast with most other frequent X-ray bursters in which bursts are helium-ignited, but consistent with the low mass accretion rate in EXO 0748-676. Possibly the hydrogen ignition is the determining factor for the occurrence of short wait-time bursts.

23 pages, 16 figures, accepted for publication in A&A

Cited by in corpus (24)

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• The Burst Spectra of EXO 0748-676 during a Long 2003 XMM-Newton Observation
• Intermediate long X-ray bursts from the ultra-compact binary source SLX 1737-282
• Turbulent Mixing in the Surface Layers of Accreting Neutron Stars
• Thermonuclear Bursts with Short Recurrence Times from Neutron Stars Explained by Opacity-Driven Convection
• Localised thermonuclear bursts from accreting magnetic white dwarfs
• Long tails on thermonuclear X-ray bursts from neutron stars: a signature of inward heating?
• Properties of the ionised plasma in the vicinity of the neutron-star X-ray binary EXO 0748-676
• A NICER look at thermonuclear X-ray bursts from Aql X-1
• The Incompatibility of Rapid Rotation with Narrow Photospheric X-ray Lines in EXO 0748-676
• Indications for a slow rotator in the Rapid Burster from its thermonuclear bursting behaviour
• Thermonuclear X-ray Bursts with late secondary peaks observed from 4U 1608-52
• Puzzling thermonuclear burst behaviour from the transient low-mass X-ray binary IGR J17473-2721
• Discovery of Thermonuclear Type-I X-ray Bursts from the X-ray binary MAXI J1807+132
• Discovery of transition from marginally stable burning to unstable burning after a superburst in Aql X-1
• The study of multi-peaked type-I X-ray bursts in the neutron-star low mass X-ray binary 4U 1636$-$536 with RXTE
• Multiple X-ray bursts and the model of a spreading layer of accreting matter over the neutron star surface
• XMMU J181227.8-181234: a new ultracompact X-ray binary candidate
• The thermonuclear X-ray bursts of 4U 1730-22
• Hydrogen-triggered X-ray Bursts from SAX J1808.4-3658? The Onset of Nuclear Burning
• Simultaneous Optical and X-ray Detection of a Thermonuclear Burst in the 2024 Outburst of EXO 0748-676
• X-ray and optical orbital modulation of EXO 0748-676: A co-variability study using XMM-Newton
• NuSTAR and AstroSat observations of thermonuclear X-ray bursts with short-recurrence times in 4U 1636$-$536