Abstract We detect two high-confidence star-forming sources in the environment of a chemically near-pristine ([Fe/H] <−3.66 ; 2σ) Damped Lyα system (DLA) using Keck/KCWI. These are found via the hydrogen Lyα emission line at Δv = −1200 km s−1 (LAE1) and Δv = −200 km s−1 (LAE2) relative to the DLA redshift (zabs = 3.078) at an impact parameter of b = 66 physical kpc and b = 137 physical kpc. We measure Lyα fluxes of $F(\rm Ly\alpha )_{\rm LAE1} =4.4\pm 0.7\times 10^{-18}~\rm erg\, s^{-1}\, cm^{-2}$ and $F(\rm Ly\alpha )_{\rm LAE2} =3.8\pm 0.9\times 10^{-18}~\rm erg\, s^{-1}\, cm^{-2}$. This marks the first detection of star formation in the environment of a chemically near-pristine DLA. We use red channel Keck/KCRM data to place limits on the associated He ii 1640Å emission flux of these sources, $F(\rm He\textsc {ii}) <3.8\times 10^{-19}~\rm erg\, s^{-1}\, cm^{-2}~(3\sigma )$ and $F(\rm He\textsc {ii}) <3.7\times 10^{-19}~\rm erg\, s^{-1}\, cm^{-2}~(3\sigma )$. The weak and narrow properties of the Lyα emission, combined with the inferred position on the mass-metallicity relation, suggest a metal-paucity of these galaxies. Future rest-frame optical observations are required to pin down the metallicity of LAE1 and LAE2 and test if chemically near-pristine DLAs can be used as a signpost to search for primitive, metal-poor galaxies 2 Gyrs after the Big Bang.
Abstract We present a morpho-kinematic study of the Necklace Nebula based on spatially resolved spectroscopic observations and 3D modeling performed with the shape software. The nebula is characterized by an equatorial disrupted ring accompanied by bipolar outflows. The geometry and velocity field of these different components are derived from the comparison between observed and synthetic images and position-velocity diagrams. The best model successfully reproduces the main morphological and kinematic features of the nebula, allowing us to constrain its 3D structure. We confirm that the disrupted ring is tilted about 60○ from the plane of the sky, but the bipolar outflows are inclined by 46○ with respect to the line of sight. This situation might indicate that the bipolar structures are not simple extensions of the equatorial ring, but instead correspond to a distinct mass-ejection event. The slight misalignment between these two components suggests either precession of the ejection axis, a temporal change in the dominant mass-loss geometry, or a misalignment in the magnetic field. Given that the Necklace Nebula hosts a close binary central star and is a well-established post-common envelope planetary nebula, our results support a scenario in which binary interaction plays a central role in shaping its morphology, even before the common envelope phase.
Abstract Near-infrared interferometric surveys have revealed extended emission around the photosphere of ≈40 main-sequence stars, attributed to the presence of hot exozodiacal dust (HEZD). A promising technique for investigating this phenomenon is nulling interferometry. The VLTI nulling interferometer NOTT (Nulling Observations of exoplaneTs and dusT) is designed to characterise exoplanets and HEZD in the L′ band (3.5 − 4.0 μm). We aim to assess NOTT’s potential for the detection and characterisation of HEZD with various instrumental and model parameter configurations. We model the HEZD as an optically thin dust ring, using the nearby Sun-like star τ Ceti with HEZD as a reference model. Applying the end-to-end nulling tool SCIFYsim to model the instrumental response of NOTT to simulated HEZD brightness distributions, we evaluate how variations in HEZD and instrumental parameters affect NOTT’s key observables: the photon flux rate and the null depth. We demonstrate that NOTT is capable of disentangling stellar and dust contributions to the signal and detecting HEZD. The null depth and photon flux rate are sensitive to the HEZD geometry, with inclination, position angle, and ring location having the strongest impact on the signal. Although the detailed temporal signatures are target-specific, the results can be generalised to other systems. NOTT has the potential to deliver unprecedented sensitivity for HEZD observations, granting access to detailed information through spectral dispersion, beam-combination schemes, and exploitation of sky rotation. This enables more sensitive HEZD detections than is possible with current instruments, and improved spatial constraints on the dust, as well as variability studies.
Abstract Sensitivity study of nuclear properties, particularly given that most remain experimentally unmeasured, is critical for understanding nucleosynthesis processes. Because it both reveals the features of the elements evolution and provides the valuable guidance to experiment. In the weak rapid neutron capture process, the (α,n) reactions are predicted to play dominated roles while the neutron capture reactions are suppressed due to insufficient neutron exposure. A number of measurements on the cross sections of (α,n) reactions are performed with various techniques subsequently. Measurements employing short-lived beams are particularly significant for understanding the weak r-process, since the nucleosynthesis path lies far from the valley of stability. However, the beam energy, which is directly corresponds to the astrophysical temperature, are not easily varied during the experiment especially when detection relies on γ-ray or neutron. Therefore, it would be highly instructive for energy setting if the temperature ranges of maximum sensitivity could be determined prior to the experiment. In this work, a sensitivity study,which focuses on the steps of the reaction flow, is proposed. It monitors the reaction rate of each type of reactions and the density of relevant nuclei which participate in, then determines the order of importance of nuclear reactions. The leading role of the (α,n) reaction is confirmed by this method, and the sensitive temperature ranges of all key reactions are then tabulated. Several characteristics found in this study are also discussed, including the upbend of matter flow at closed shells and the correlation between nuclear properties and the model trajectory.
ABSTRACT Rocky exoplanets are particularly abundant around M-type stars. These stars’ small radii and low luminosities provide favourable conditions for detecting transiting terrestrial planets and probing their atmospheric properties. We report the discovery and statistical validation of TOI-4616 b, an Earth-sized planet transiting a nearby mid-M dwarf observed by TESS. We confirm the planetary nature of the signal and determine the system parameters by combining TESS photometry with ground-based multi-band transit observations, high-resolution imaging, and optical/near-infrared spectroscopy. The host star lies at a distance of $28.10\pm 0.07$ pc and has $R_\star = 0.1889\pm 0.0096\, \mathrm{R}_\odot$, $M_\star = 0.1881\pm 0.0094\, \mathrm{M}_\odot$, and $T_{\rm eff}=3150\pm 75$ K. TOI-4616 b has a radius of $1.22\, R_{\rm{\oplus }}$ and an orbital period of 1.55 d. The planet receives an incident flux of $\sim 40\, S_{\rm{\oplus }}$, corresponding to an equilibrium temperature of $\sim 525$ K. This places TOI-4616 b in a regime intermediate between Earth-sized planets orbiting early M dwarfs and those around ultra-cool hosts. Statistical validation with triceratops, supported by high-resolution imaging and chromatic transit constraints, yields a false-positive probability of 0.0135 below the recommended threshold of 0.015, confirming TOI-4616 b as a validated planet. Owing to its proximity to Earth, well-constrained stellar properties, and extensive multi-band follow-up, TOI-4616 b constitutes a valuable benchmark system for comparative studies of terrestrial planets around mid-M dwarfs and for future atmospheric investigations.
