Discovery of transition from marginally stable burning to unstable burning after a superburst in Aql X-1

Abstract

Superbursts are long duration, rare, and extremely energetic thermonuclear explosions of neutron star low-mass X-ray binaries (NS LMXBs), which are proposed to be due to unstable carbon ignition. We report the superburst properties and consequences from Aql X-1 observed by the Neutron Star Interior Composition Explorer (NICER), the Monitor of All-sky X-ray Image, Swift, and Insight Hard X-ray Modulation Telescope (Insight-HXMT) on the MJD 59130.7. We found two faint type I X-ray bursts 9.44 days after the superburst with a short recurrence time of 7.6 minutes, which is the most accurate measurement of the quenching time in all NS LMXBs with observed superbursts. We also discovered mHz quasi-periodic oscillations in the frequency range 2.7--11.3 mHz immediately after the superburst, before and after the resumption of the first type I X-ray burst from NICER, Swift, and Insight-HXMT observations. For the first time, we observed the transition from superburst, via marginally stable burning to unstable burning in NS LMXBs. We compared the quenching time and the recurrence time of type I X-ray bursts with simulations.

Minor changes to match version published in ApJ

References in corpus (16)

• An online repository of Swift/XRT light curves of GRBs
• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Assessing statistical significance of periodogram peaks
• Evaluating Spectral Models and the X-ray States of Neutron-Star X-ray Transients
• Discovery of coherent millisecond X-ray pulsations in Aql X-1
• Intermediate long X-ray bursts from the ultra-compact binary source SLX 1737-282
• Superburst Models for Neutron Stars with Hydrogen and Helium-Rich Atmospheres
• Discovery of X-ray burst triplets in EXO 0748-676
• Turbulent Mixing in the Surface Layers of Accreting Neutron Stars
• The donor of Aquila X-1 revealed by high angular resolution near-infrared spectroscopy
• Thermonuclear Bursts with Short Recurrence Times from Neutron Stars Explained by Opacity-Driven Convection
• Maxi observations of long X-ray bursts
• Crust cooling of the neutron star in Aql X-1: Different depth and magnitude of shallow heating during similar accretion outbursts
• The superburst recurrence time in luminous persistent LMXBs
• Simultaneous constraints on the mass and radius of Aql X-1 from quiescence and X-ray burst observations
• Drifts of the marginally stable burning frequency in the X-ray binaries 4U 1608--52 and Aql X--1

Cited by in corpus (8)

• A NICER look at thermonuclear X-ray bursts from Aql X-1
• NICER views moderate, strong, and extreme photospheric expansion bursts from the ultracompact X-ray binary 4U 1820$-$30
• Discovery of a 584.65 Hz Burst Oscillation in the Low Mass X-Ray Binary 4U 1730--22
• Discovery of a long thermonuclear X-ray burst from the ultra-compact binary 4U 1850$-$087
• Quenching and recovery of persistent X-ray emission during a superburst in 4U 1820$-$30
• A transition from mixed-fuel to pure-helium thermonuclear bursts in Terzan 5 X-3/Swift J174805.3-244637
• Long thermonuclear burst driven thermal-viscous instability of accretion disk: triggering an outburst-like X-ray flare
• Tracing the outburst decay of soft X-ray transients Aql X-1 and 4U 1608-52 with XSPECT