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1. Nonthermal Signatures of Radiative Supernova Remnants

   https://doi.org/10.3847/1538-4357/ad74f0  

   Diesing, Rebecca; Guo_郭, Minghao_明浩; Kim, Chang-Goo; Stone, James; Caprioli, Damiano (October 2024, The Astrophysical Journal)

   Abstract The end of supernova remnant (SNR) evolution is characterized by a so-called “radiative” stage, in which efficient cooling of the hot bubble inside the forward shock slows expansion, leading to eventual shock breakup. Understanding SNR evolution at this stage is vital for predicting feedback in galaxies, since SNRs are expected to deposit their energy and momentum into the interstellar medium at the ends of their lives. A key prediction of SNR evolutionary models is the formation at the onset of the radiative stage of a cold, dense shell behind the forward shock. However, searches for these shells via their neutral hydrogen emission have had limited success. We instead introduce an independent observational signal of shell formation arising from the interaction between nonthermal particles accelerated by the SNR forward shock (cosmic rays) and the dense shell. Using a semi-analytic model of particle acceleration based on state-of-the-art simulations coupled with a high-resolution hydrodynamic model of SNR evolution, we predict the nonthermal emission that arises from this interaction. We demonstrate that the onset of the radiative stage leads to nonthermal signatures from radio to gamma rays, including radio and gamma-ray brightening by nearly 2 orders of magnitude. Such a signature may be detectable with current instruments, and will be resolvable with the next generation of gamma-ray telescopes (namely, the Cherenkov Telescope Array). 

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2. Observation of radiative double electron capture for

   https://doi.org/10.1002/xrs.3063  

   Kumara, Nuwan; La_Mantia, David_S; Buglione, Stephanie_L; McCoy, Craig_P; Taylor, Charles_J; White, Jacob_S; Kayani, Asghar; Tanis, John_A (June 2019, X-Ray Spectrometry)

   Radiative double electron capture (RDEC), occurring when two electrons are captured to a projectile ion with the simultaneous emission of a single photon, has been investigated. RDEC can be considered as the time inverse process of double photoionization. Strong evidence for RDEC is found in F⁹⁺+ N₂collisions and additionally for one‐electron F⁸⁺for which the probability for the process is expected to be considerably smaller. Preliminary values for the cross sections for RDEC have been determined. A significant advantage of the gas target is that multiple‐collision effects seen for a solid target are avoided due to the single‐collision conditions that prevail for gas targets. 

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3. Radiative energy and mass shifts of quantum cyclotron states

   https://doi.org/10.1140/epjd/s10053-025-00982-3  

   Jentschura, U_D (April 2025, The European Physical Journal D)

   AbstractWe discuss relativistic and radiative corrections to the energies of quantum cyclotron states. In particular, it is shown analytically that the leading logarithmic radiative (self-energy) correction to the bound-state energy levels of quantum cyclotron states is state independent and must be interpreted as a magnetic field-dependent correction to the electron’s mass in a Penning trap. Graphical abstract 

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4. Vapor condensation with daytime radiative cooling

   https://doi.org/10.1073/pnas.2019292118  

   Zhou, Ming; Song, Haomin; Xu, Xingyu; Shahsafi, Alireza; Qu, Yurui; Xia, Zhenyang; Ma, Zhenqiang; Kats, Mikhail A.; Zhu, Jia; Ooi, Boon S.; et al (March 2021, Proceedings of the National Academy of Sciences)

   A radiative vapor condenser sheds heat in the form of infrared radiation and cools itself to below the ambient air temperature to produce liquid water from vapor. This effect has been known for centuries, and is exploited by some insects to survive in dry deserts. Humans have also been using radiative condensation for dew collection. However, all existing radiative vapor condensers must operate during the nighttime. Here, we develop daytime radiative condensers that continue to operate 24 h a day. These daytime radiative condensers can produce water from vapor under direct sunlight, without active consumption of energy. Combined with traditional passive cooling via convection and conduction, radiative cooling can substantially increase the performance of passive vapor condensation, which can be used for passive water extraction and purification technologies. 

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5. Stochastic Averaging of Radiative Transfer Coefficients for Relativistic Electrons

   https://doi.org/10.3847/1538-4357/ad4636  

   Mościbrodzka, Monika; Gammie, Charles F (June 2024, The Astrophysical Journal)

   Abstract Synchrotron emissivities, absorptivities, and Faraday rotation and conversion coefficients are needed in modeling a variety of astrophysical sources, including Event Horizon Telescope (EHT) sources. We develop a method for estimating transfer coefficients that exploits their linear dependence on the electron distribution function, decomposing the distribution function into a sum of parts each of whose emissivity can be calculated easily. We refer to this procedure as stochastic averaging and apply it in two contexts. First, we use it to estimate the emissivity of an isotropicκdistribution function with a high-energy cutoff. The resulting coefficients can be evaluated efficiently enough to be used directly in ray-tracing calculations, and we provide an example calculation. Second, we use stochastic averaging to assess the effect of subgrid turbulence on the volume-averaged emissivity and along the way provide a prescription for a turbulent emissivity. We find that for parameters appropriate to EHT sources turbulence reduces the emissivity slightly. In the infrared, turbulence can dramatically increase the emissivity. 

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