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This paper investigates the accretion of neutron stars (NSs) in active galactic nucleus (AGN) accretion discs. We classify potential accretion modes of NSs in AGN discs, proposing a hierarchical model of NS accretion: accretion flow from the Bondi sphere to accretion columns. The accretion of NSs in AGN discs differs from that of BHs, especially within the scale of the NS's magnetosphere due to its hard surface and magnetic field. As the accretion flow approaches the magnetosphere, the magnetic fields guide the accretion flow to form accretion columns, primarily dominated by neutrinos. While neutrinos generated from single NS accretion may not have observable effects, considering the all-sky background, they contribute to the neutrino background in the sub-MeV energy range comparable to that of supernova explosions. NS accretion may also lead to the generation of mass quadrupole moments, consequently generating gravitational waves (GWs). The GWs, which exhibit characteristic effects like periodic modulations and echoes, could be observed by third-generation GW detectors. The emission of neutrinos and GWs carries away energy and angular momentum brought by accretion, reducing the feedback effect on the AGN disc. This results in an exceptionally high NS accretion rate, leading to a collapse time-scale shorter than the migration-merge time-scale, making it less likely that binary NS mergers originate from AGN discs. [ABSTRACT FROM AUTHOR]

White dwarfs (WDs) in active galactic nucleus (AGN) discs might migrate to the inner radii of the discs and form restricted three-body systems with two WDs moving around the central supermassive black hole (SMBH) in close orbits. These systems could be dynamically unstable, which can lead to very close encounters or direct collisions. In this work, we use N -body simulations to study the evolution of such systems with different initial orbital separation p , relative orbital inclination Δ i , and SMBH mass M. It is found that close encounters of WDs occur mainly at |$1.1R_{\rm H} \lesssim p \lesssim 2\sqrt{3}R_{\rm H}$|⁠ , where R H is the mutual Hill radius. For p < 1.1 R H, the majority of WDs move in horseshoe or tadpole orbits, and only few of them with small initial orbital phase difference undergo close encounters. For p = 3.0 R H, WD–WD collisions occur in most of the samples within a time 105 P 1, and considerable collisions occur within a time t < 62 P 1 for small orbital radii, where P 1 is the orbital period. The peak of the closest separation distribution increases and the WD–WD collision fraction decreases with an increase in relative inclination. The closest separation distribution is similar in cases with different SMBH mass, but the WD–WD collision fraction decreases as the mass of SMBHs increases. According to our estimation, the event rate of cosmic WD–WD collisions in AGN discs is about 300 Gpc−3 yr−1, roughly 1 per cent of that of observed Type Ia supernovae. The corresponding electromagnetic emission signals can be observed through large surveys of AGNs. [ABSTRACT FROM AUTHOR]

In the inner region of the disc of an active galactic nucleus (AGN), the collision of two white dwarfs (WDs) through Jacobi capture might be inevitable, leading to a Type Ia supernova (SN Ia) explosion. This transient event, influenced by the disc gas and the gravity of the supermassive black hole (SMBH), exhibits distinct characteristics compared with normal SNe Ia. The energy of the explosion is mainly stored in the ejecta in the form of kinetic energy. Typically, the ejecta is not decelerated effectively by the AGN disc and rushes rapidly out of the AGN disc. However, under the influence of the SMBH, most of the ejecta falls back toward the AGN disc. As the fallback ejecta becomes more dispersed, it interacts with the disc gas, converting its kinetic energy into thermal energy. This results in a high-energy transient characterized by a rapid initial rise followed by a decay with L ∝ t −2.8. The time-scale of the transient ranges from hours to weeks, depending on the mass of the SMBH. This process generates high-energy radiation spanning from hard X-rays to the soft γ range. Additionally, the subsequent damage to the disc may result in changing-look AGNs. Moreover, the falling back of SNe Ia ejecta on to the AGN disc significantly increases the metallicity of the AGN and can even generate heavy elements within AGN discs. [ABSTRACT FROM AUTHOR]

Under the goals of carbon neutrality and peak carbon emissions, photovoltaic (PV) power generation is widely valued for its clean and green characteristics. However, the uncertainty and randomness of PV power pose challenges to energy management. Therefore, this study proposed a novel bimodal feature fusion network-based deep learning model with an intelligent fusion gate mechanism for short-term photovoltaic power point-interval forecasting. First, a threshold-guided iNNE-based outlier detection and repair method is designed for preprocessing PV data. Second, a bimodal feature fusion network was proposed to extract global and local features from PV power sequences, and the environmental factors-based rime optimization algorithm with growth mutation strategy and humidity perception mechanism was devised to optimize model's hyperparameters. Additionally, a photovoltaic power interval prediction model with a volatility segmentation strategy was introduced. Finally, the effectiveness of the proposed model, algorithm, and strategies was validated using measured datasets. The results demonstrated that under various weather conditions, the proposed model achieved point prediction evaluation metrics with an R2 exceeding 98 % and a prediction interval evaluation metric with a Prediction Interval Coverage Probability of 85.07 %. The obtained outcomes contribute to providing a basis for decision-making in the scientific scheduling and management of PV power systems. • The proposal of a bimodal feature fusion network-based deep learning model. • The proposal of a threshold-guided iNNE-based outlier detection and repair method. • The proposal of EFRIME with growth mutation and humidity perception mechanism. • The introduction of the TAP-MSIP model with the VSS strategy. [ABSTRACT FROM AUTHOR]