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  • Discovery of Spin-pulse Correlated Magnetic Gating Bursts in the Long-period Intermediate Polar PBC J0801.2–4625
    We present the first discovery of small-amplitude (tens of millimagnitudes), short-duration (several hours) episodic brightenings in the Transiting Exoplanet Survey Satellite (TESS) light curve of the intermediate polar PBC J0801.2–4625 that are strongly correlated with the white dwarf spin. Specifically, during the bursts, the spin period remains unchanged, while the pulse amplitude increases markedly in a highly asymmetric manner, with only the pulse maximum being enhanced by a factor of ∼2. Essentially, the bursts are a mere amplification of the spin modulation and lack the characteristic morphology of a typical burst. These events reach peak luminosities of order 1031 erg s−1 and release total energies of ∼1037 erg. The observed burst properties, including the durations and energy scales involved, favor magnetically gated accretion as their likely origin. Using the condition for magnetic gating instability, we infer a magnetic field of about 2.6 MG, consistent with the intermediate polar nature of the source. Furthermore, based on our TESS timing analysis, we confirm the previously reported orbital period and refine it to 11.8099210(65) hr. The orbital phase curve is dominated by ellipsoidal modulation from the secondary and exhibits a time-variable morphology. Additionally, the previously reported spin period of ∼1307.5 s is confirmed and found to vary modestly from sector to sector.

  • Four-hundred Very Metal-poor Stars Studied with LAMOST and Subaru. IV. Heavy Element Enhanced Stars
    We perform a homogeneous analysis of 82 heavy-element-enhanced metal-poor stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) /Subaru sample, including 64 r-process-enhanced stars, two limited-r stars, and 16 stars exhibiting significant or moderate carbon enhancement (comprising nine s-process-enhanced, two r-process-enhanced, two r/s, and three r+s stars). Systematic differences in [X/Eu] between r-I and r-II stars, together with their distinct dynamical properties, suggest that r-II stars likely formed in low-mass dwarf galaxies where contamination from additional nucleosynthetic channels was minimal. We have also discovered a number of peculiar objects. We identify an extremely metal-poor r-II star, J1158+0734 ([Fe/H] = −2.93), whose enhanced Zn abundance ([Zn/Fe] = +0.67) is best explained by yields from a high-energy, massive core-collapse supernova. The surface abundances of s-process-enhanced stars exhibit pronounced dispersion, consistent with enrichment from asymptotic giant branch (AGB) progenitors with diverse properties. Notably, one star, J2256+0215, reveals compelling evidence for additional evolutionary mixing, as indicated by its unusually low carbon abundance ([C/Fe] = +0.08) and extremely low 12C/13C ratio of 2.33. Additionally, we identify three carbon-enhanced metal-poor (CEMP) r+s stars whose abundance patterns reveal combined contributions from both the r- and s-processes. We further propose a modified diagnostic scheme for the identification of CEMP-r+s stars, defined as −0.2 ≤ [La/Nd] ≤ 0.2 and −0.5 ≤ [Eu/Nd] ≤ 0.0.

  • Turbulence Mode Decomposition and Anisotropy in Magnetically Dominated Collisionless Plasmas
    We use 3D fully kinetic simulations to study different turbulence modes and turbulence anisotropy of relativistic turbulence in magnetically dominated collisionless plasmas. We extend the method developed by J. Cho & A. Lazarian for decomposing nonrelativistic magnetohydrodynamic (MHD) turbulence into Alfvén, fast, and slow modes to the regime of collisionless plasmas. We find that Alfvén and slow modes are anisotropic, following the P. Goldreich & H. Sridhar scaling, while fast modes are isotropic. We observe a larger kinetic energy fraction of fast modes compared to that found in the nonrelativistic MHD turbulence, suggesting a stronger coupling of Alfvén and fast modes in relativistic magnetized turbulence in collisionless plasmas. We further examine the dynamic alignment and find a weaker scale dependence of the alignment angle than previously proposed. The dominant thermal fluctuations in the kinetic range can cause flattening of the turbulent velocity structure function and weakening of the turbulence anisotropy and dynamic alignment near the kinetic scales.

  • The Goldilocks Problem for Detecting Water in Terrestrial Planets: Constraining Water Abundances in the Mid-infrared with LIFE
    We investigate how well the Large Interferometer for Exoplanets (LIFE) mission concept can detect habitable conditions on exoplanets through the presence of atmospheric water vapor as a proxy for surface oceans. We model the atmosphere of a prebiotic Earth-like planet across a range of water concentrations, from water-poor to water-rich, with surface partial pressures from 10−7 to 1 bar of H2O. We simulate LIFE-like noise at spectral resolutions R = 50 and 100 using LIFEsim and perform Bayesian atmospheric retrievals to determine the technical requirements for LIFE to confirm habitability. We model three vertical water distributions—a vertically constant profile, a Manabe–Wetherald-based Earth-like profile, and a diffusion and photochemistry profile—to test how the assumed vertical structure influences the retrieved abundances. Clouds are not modeled. We find the ability for LIFE to detect water strongly depends on the vertical profile assumed. LIFE is unable to constrain the highest-water cases and provides upper limits on low-water planets. For the highest-water abundances, absorption features saturate and reduce the sensitivity for characterizing precise H2O levels. Water vapor is not detectable in any profile modeled for ≤10−6 bar in surface water, comparable to Mars. For an Earth-like profile, LIFE could constrain H2O concentrations from ∼10−3 to 1 bar, spanning below and above present-day Earth concentrations of 10−2 bar. Detectable atmospheric water may imply surface oceans, as water is highly reactive and rapidly removed by surface mineral reactions. Thus, LIFE can characterize water abundances indicative of habitable surface conditions.

  • TeV γ-Rays from the Low-luminosity Active Galactic Nucleus NGC 4278: Implications for the Diffuse Neutrino Background
    This work investigates the origin of the TeV emission detected by the Large High Altitude Air Shower Observatory (LHAASO) from NGC 4278, a galaxy hosting a low-luminosity active galactic nucleus (LLAGN). Considering two plausible scenarios, active galactic nucleus jets and winds, we model the X-ray, GeV, and TeV emission during both TeV-low (quasi-quiet) and TeV-high (active) states. The spectral energy distributions can be explained either by single-zone leptonic emission from moderately relativistic jets or by leptohadronic emission from subrelativistic winds. The best-fit parameters suggest that the transition from the quasi-quiet to the active state may be driven jointly by an enhanced accretion rate and the jet deceleration or wind expansion. We further show that future MeV and very-high-energy γ-ray observations can discriminate between the leptonic and leptohadronic scenarios. Although the neutrino flux from NGC 4278 predicted by the wind model is too low to be detected with current neutrino observatories, a leptohadronic wind scenario can account for the PeV diffuse neutrino background when adopting a local LLAGN density (nL,0) corrected for the TeV duty cycle (ΔTTeV/T, the fraction of a LLAGN’s lifetime spent in a TeV-emitting phase), nL,0(ΔTTeV/T) ∼ 10−5 Mpc−3, as inferred from the LHAASO detection.