Insight-HXMT observations on thermonuclear X-ray bursts from 4U~1608--52 in 2022: the accretion rate dependent anisotropy of burst emission
arXiv:2502.19827 · doi:10.1016/j.jheap.2023.11.001
Abstract
Thermonuclear X-ray bursts occur on the surface of an accreting neutron star (NS), and their characteristics and interplay with the surrounding circumstance could be a clue to understand the nature of the NS and accretion process. For this purpose, Insight-HXMT has performed high cadence observations on the bright thermonuclear X-ray burster--4U~1608--52 during its outburst in July and August 2022; nine bursts were detected, including seven bursts with the photospheric radius expansion (PRE). Time-resolved spectroscopy of the bright PRE bursts reveals that an enhancement of accretion rate or the Comptonization of the burst emission by the corona could reduce the residuals when fitting their spectra with the conventional model--blackbody. The inferred energy increment rate of the burst photon gained from the corona is up to 40\%, even though the bursts have different peak fluxes and locate at different accretion rates. Moreover, the flux shortage of the rising PRE is observed in the bursts at a high mass accretion rate, but not for the burst with a faint persistent emission, which has been predicted theoretically but first observed in this work. If the flux shortage is due to the disk obscuration, i.e., the burst emission is anisotropic, the phenomenon above could indicate that the anisotropy of the burst emission is accretion rate dependent, which could also be evidence of the truncated disk in the low/hard state.
2023, Journal of High Energy Astrophysics, 40, 76. arXiv admin note: text overlap with arXiv:2209.10721
References in corpus (18)
- Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
- Spectral and temporal properties of Compton scattering by mildly relativistic thermal electrons
- X-ray bursting neutron star atmosphere models using an exact relativistic kinetic equation for Compton scattering
- The effect of accretion on the measurement of neutron star mass and radius in the low-mass X-ray binary 4U 1608-52
- Evidence for enhanced persistent emission during sub-Eddington thermonuclear bursts
- Accretion disks and coronae in the X-ray flashlight
- The influence of accretion geometry on the spectral evolution during thermonuclear (type-I) X-ray bursts
- Biases for neutron-star mass, radius and distance measurements from Eddington-limited X-ray bursts
- X-Raying an Accretion Disk in Realtime: the Evolution of Ionized Reflection during a Superburst from 4U 1636-536
- A NICER look at thermonuclear X-ray bursts from Aql X-1
- Burst-induced coronal cooling in GS 1826-24 The clock wagging its tail
- A state-dependent influence of the type-I bursts on the accretion in 4U 1608--52?
- Burst-Disk Interaction in 4U 1636-536 as observed by NICER
- Insight-HXMT observation on 4U~1608--52: evidence of interplay between thermonuclear burst and accretion environments
- Evolution of accretion disc reflection spectra due to a Type I X-ray burst
- Broadband time-resolved spectroscopy of thermonuclear X-ray bursts from 4U 1636-536 using AstroSat
- Probing spectral and temporal evolution of the neutron star low-mass X-ray binary 4U 1724-30 with AstroSat
- Return of 4U~1730--22 after 49 years silence: the peculiar burst properties of the 2021/2022 outbursts observed by Insight-HXMT