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1. A Panchromatic View of Late-time Shock Power in the Type II Supernova 2023ixf

   https://doi.org/10.3847/2041-8213/ae157a  

   Jacobson-Galán, W V; Dessart, L; Kilpatrick, C D; Patel, P J; Auchettl, K; Tinyanont, S; Margutti, R; Dwarkadas, V V; Bostroem, K A; Chornock, R; et al (November 2025, The Astrophysical Journal Letters)

   Abstract We present multiwavelength observations of the Type II supernova (SN II) 2023ixf during its first 2 yr of evolution. We combine ground-based optical/near-infrared spectroscopy with Hubble Space Telescope far- and near-ultraviolet spectroscopy and James Webb Space Telescope near- and mid-infrared photometry and spectroscopy to create spectral energy distributions of SN 2023ixf at +374 and +620 days postexplosion, covering a wavelength range of ∼0.1–30μm. The multiband light curve of SN 2023ixf follows a standard radioactive decay decline rate after the plateau until ∼500 days, at which point shock-powered emission from ongoing interaction between the SN ejecta and circumstellar material (CSM) begins to dominate. This evolution is temporally consistent with 0.3–10 keV X-ray detections of SN 2023ixf and broad “boxy” spectral line emission, which we interpret to signal reprocessing of shock luminosity in a cold dense shell located between forward and reverse shocks. Using the expected absorbed radioactive decay power and the detected X-ray luminosity, we quantify the total shock-powered emission at the +374 and +620 day epochs and find that it can be explained by nearly complete thermalization of the reverse shock luminosity as SN 2023ixf interacts with a continuous, “wind-like” CSM with a progenitor mass-loss rate of $\dot{M}\approx 10^{-4}$ M_⊙yr⁻¹(v_w = 20 ± 5 km s⁻¹). Additionally, we construct multiepoch spectral models from the non-LTE radiative transfer codeCMFGENthat contain radioactive decay and shock powers as well as dust absorption, scattering, and emission. We find that models with shock powers ofL_sh = (0.5–1) × 10⁴⁰erg s⁻¹and ∼(0.5–1) × 10⁻³M_⊙of silicate dust in the cold dense shell and/or inner SN ejecta can effectively reproduce the global properties of the late-time (>300 days) UV-to-IR spectra of SN 2023ixf. 

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2. SN 2021aaev: A Hydrogen-rich Superluminous Supernova with Early Flash and Long-lived Circumstellar Interaction in an Unusual Host Environment

   https://doi.org/10.3847/1538-4357/ae374c  

   Hu_胡, Yang 阳; Lunnan, Ragnhild; Pessi, Priscila J; Saldana-Lopez, Alberto; Jerkstrand, Anders; Sollerman, Jesper; Schulze, Steve; Anderson, Joseph P; Brennan, Seán J; Cosentino, Stefano P; et al (March 2026, The Astrophysical Journal)

   Abstract We present photometric and spectroscopic observations of SN 2021aaev, a hydrogen-rich, superluminous supernova with persistent (at least ∼100 days) narrow Balmer lines (SLSN-IIn) at redshiftz= 0.1557. SN 2021aaev rose over 28.1  ±  1.0 rest-frame days after explosion, reaching a peak absolute magnitude of −21.46 ± 0.01 in the ATLASoband. The prepeak spectra resemble those of typical Type IIn SNe with flash-ionization features arising from the interaction with a dense, confined circumstellar medium (CSM), albeit the flash timescale is longer than usual (>20 days). Postpeak, the narrow emission lines evolve slowly, and the absence of ejecta features indicates strong deceleration by the CSM. The total radiated energy (about 1.41 × 10⁵¹erg) is possibly explained by a low-mass (1–2M_⊙) ejecta ploughing into a massive (9–19M_⊙), extended (outer radius >1 × 10¹⁶cm) H-rich CSM, or alternatively by magnetar-powered models. Interestingly, the host environment consists of a spiral galaxy with a red substructure in the southeastern part, and the SN’s exact location coincides with this quiescent red region (star formation rate $=0.02_{-0.02}^{+0.13}{M}_{\odot }$ yr⁻¹). Given the atypical environment and the obscuring effect of the massive CSM, a thermonuclear (Type Ia-CSM) origin cannot be ruled out. Altogether, SN 2021aaev is a compelling case to study the diversity of SLSN-IIn features and their host environments. 

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3. Pre-peak Emission in Tidal Disruption Events

   https://doi.org/10.3847/1538-4357/ad6c39  

   Huang_黄, Xiaoshan 小珊; Davis, Shane W; Jiang_姜, Yan-fei 燕飞 (October 2024, The Astrophysical Journal)

   Abstract The rising part of a tidal disruption event light curve provides unique insight into early emission and the onset of accretion. Various mechanisms are proposed to explain the pre-peak emission, including shocks from debris interaction and reprocessing of disk emission. We study the pre-peak emission and its influence on the gas circularization by a series of gray radiation hydrodynamic simulations with varying black hole mass. We find that, given a super-Eddington fallback rate of $10{\dot{M}}_{\mathrm{Edd}}$ , the stream–stream collision can occur multiple times and drive strong outflows of up to $9{\dot{M}}_{\mathrm{Edd}}$ . By dispersing gas to ≳100r_s, the outflow can delay gas circularization and leads to sub-Eddington accretion rates during the first few stream–stream collisions. The stream–stream collision shock and circularization shock can sustain a luminosity of ∼10⁴⁴erg s⁻¹for days. The luminosity is generally sub-Eddington and shows a weak correlation with accretion rate at early times. The outflow is optically thick, yielding a reprocessing layer with a size of ∼10¹⁴cm and photospheric temperature of ∼4 × 10⁴K. 

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4. A Massive Black Hole 0.8 kpc from the Host Nucleus Revealed by the Offset Tidal Disruption Event AT2024tvd

   https://doi.org/10.3847/2041-8213/add7de  

   Yao, Yuhan; Chornock, Ryan; Ward, Charlotte; Hammerstein, Erica; Sfaradi, Itai; Margutti, Raffaella; Kelley, Luke Zoltan; Lu, Wenbin; Liu, Chang; Wise, Jacob; et al (May 2025, The Astrophysical Journal Letters)

   Abstract Tidal disruption events (TDEs) that are spatially offset from the nuclei of their host galaxies offer a new probe of massive black hole (MBH) wanderers, binaries, triples, and recoiling MBHs. Here we present AT2024tvd, the first off-nuclear TDE identified through optical sky surveys. High-resolution imaging with the Hubble Space Telescope shows that AT2024tvd is 0 $\stackrel{\text{″}}{.}$ 914 ± 0 $\stackrel{\text{″}}{.}$ 010 offset from the apparent center of its host galaxy, corresponding to a projected distance of 0.808 ± 0.009 kpc atz= 0.045. Chandra and Very Large Array observations support the same conclusion for the TDE’s X-ray and radio emission. AT2024tvd exhibits typical properties of nuclear TDEs, including a persistent hot UV/optical component that peaks atL_bb ∼ 6 × 10⁴³erg s⁻¹, broad hydrogen lines in its optical spectra, and delayed brightening of luminous (L_X,peak ∼ 3 × 10⁴³erg s⁻¹), highly variable soft X-ray emission. The MBH mass of AT2024tvd is 10^6±1M_⊙, at least 10 times lower than its host galaxy’s central black hole mass (≳10⁸M_⊙). The MBH in AT2024tvd has two possible origins: a wandering MBH from the lower-mass galaxy in a minor merger during the dynamical friction phase or a recoiling MBH ejected by triple interactions. Combining AT2024tvd with two previously known off-nuclear TDEs discovered in X-rays (3XMM J2150 and EP240222a), which likely involve intermediate-mass black holes in satellite galaxies, we find that the parent galaxies of all three events are very massive (∼10^10.9M_⊙). This result aligns with expectations from cosmological simulations that the number of offset MBHs scales linearly with the host halo mass. 

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5. A little red dot at z = 7.3 within a large galaxy overdensity

   https://doi.org/10.1038/s41550-025-02660-1  

   Schindler, Jan-Torge; Hennawi, Joseph F; Davies, Frederick B; Bosman, Sarah_E I; Endsley, Ryan; Wang, Feige; Yang, Jinyi; Barth, Aaron J; Eilers, Anna-Christina; Fan, Xiaohui; et al (November 2025, Nature Astronomy)

   Abstract The nature of ‘little red dots’ and their relation to other forms of accreting supermassive black holes remain an open question. Here we report the discovery of a little red dot atz = 7.3. It is attenuated by moderate amounts of dust,A_V = 2.79 mag, and has an intrinsic bolometric luminosity of 10^46.6 erg s⁻¹and a supermassive black hole mass of 5 × 10⁸ M_⊙. Most notably, this object is embedded in an overdensity of eight nearby galaxies, allowing us to calculate a spectroscopic estimate of the clustering of galaxies around little red dots. We find a little red dot versus galaxy cross-correlation length ofr₀ = 8 ± 2 h⁻¹ cMpc, comparable to that ofz ≈ 6 ultraviolet-luminous quasars. The resulting estimate of their minimum dark matter halo mass$$\log_{10}({M}_{{\rm{halo}},\min }/{{{M}}}_{\odot })=12.{0}_{-1.0}^{+0.8}$$ ${\log }_{10}\left(M_{\mathrm{halo},\min }/M_{\odot }\right)=12.0_{-1.0}^{+0.8}$ indicates that nearly all haloes above this mass must host actively accreting supermassive black holes atz ≈ 7, in strong contrast with the far smaller duty cycle of luminous quasars (<1%). Our results, taken at face value, motivate a picture in which supermassive black holes in little red dot phases could serve as the obscured precursors of ultraviolet-luminous quasars, which provides a natural explanation for the short ultraviolet-luminous lifetimes inferred from both quasar clustering and quasar proximity zones. 

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