2026/06/10 by Wenhui Yu, Zhaosheng Li, Yuanyue Pan +2
Physics and Astronomy · #astro-ph.HE
paper · pdf · doi:10.3847/1538-4357/ae7be8
We report on NICER and MAXI observations of a long-duration thermonuclear X-ray burst and a subsequent outburst-like X-ray flare from the neutron star low-mass X-ray binary MAXI J0911--655. Prior to the burst, the source was in a persistent low/hard state with a power-law-dominated spectrum (Γ∼ 1.7) and a mass accretion rate of ∼ 1% of the Eddington limit. The long burst, detected by MAXI on 2020 May 22 (MJD 58991.7101), was rapidly followed up by NICER. From time-resolved spectroscopy of the cooling tail, we estimate an exponential decay time of ≈43 minutes, the ignition column depth of ≈0.1× 1012~\rm g ~cm-2, the burst fluence of ≈ 1.1× 10-4~\rm erg~cm-2, and the total energy release of ≈1.2×1042 erg. Approximately one day after the burst onset, the 0.5-10 keV light curve unexpectedly re-brightened, initiating an outburst-like flare. During the peak of this flare, the persistent power-law flux increased from its pre-burst level of ∼0.27×10-9~\rm erg~cm-2~s-1 to 1.4×10-9~\rm erg~cm-2~s-1. This flux enhancement was accompanied by significant spectral softening, with the photon index increasing to Γ∼ 2.2. Subsequently, the flux decayed and the source returned to its baseline low/hard state. The observed timescales and energetics suggest that intense irradiation from the long burst amplified the ongoing thermal-viscous accretion process. This heating drove an inside-out heating front that temporarily enhanced the mass accretion rate, providing compelling observational evidence of a thermonuclear burst directly modulating the accretion dynamics of its surrounding disk.