Abstract The Murchison Widefield Array (MWA) is one of three Square Kilometre Array Precursor telescopes and is located at the Murchison Radio-astronomy Observatory in the Murchison Shire of the mid-west of Western Australia, a location chosen for its extremely low levels of radio frequency interference. The MWA operates at low radio frequencies, 80–300 MHz, with a processed bandwidth of 30.72 MHz for both linear polarisations, and consists of 128 aperture arrays (known as tiles) distributed over a ~3-km diameter area. Novel hybrid hardware/software correlation and a real-time imaging and calibration systems comprise the MWA signal processing backend. In this paper, the as-built MWA is described both at a system and sub-system level, the expected performance of the array is presented, and the science goals of the instrument are summarised.
This Review discusses the emerging field of mid-infrared frequency comb generation, including technologies based on novel laser gain media, nonlinear frequency conversion and microresonators, as well as the applications of these combs in precision spectroscopy and direct frequency comb spectroscopy. Laser frequency combs are coherent light sources that emit a broad spectrum of discrete, evenly spaced narrow lines whose absolute frequency can be measured to within the accuracy of an atomic clock. Their development in the near-infrared and visible domains has revolutionized frequency metrology while also providing numerous unexpected opportunities in other fields such as astronomy and attosecond science. Researchers are now exploring how to extend frequency comb techniques to the mid-infrared spectral region. Versatile mid-infrared frequency comb generators based on novel laser gain media, nonlinear frequency conversion or microresonators promise to significantly expand the applications of frequency combs. In particular, novel approaches to molecular spectroscopy in the 'fingerprint region', with dramatically improved precision, sensitivity, recording time and/or spectral bandwidth may lead to new discoveries in the various fields relevant to molecular science.
AbstractPerturbations of stars and black holes have been one of the main topics of relativistic astrophysics for the last few decades. They are of particular importance today, because of their relevance to gravitational wave astronomy. In this review we present the theory of quasi-normal modes of compact objects from both the mathematical and astrophysical points of view. The discussion includes perturbations of black holes (Schwarzschild, Reissner-Nordström, Kerr and Kerr-Newman) and relativistic stars (non-rotating and slowly-rotating). The properties of the various families of quasi-normal modes are described, and numerical techniques for calculating quasi-normal modes reviewed. The successes, as well as the limits, of perturbation theory are presented, and its role in the emerging era of numerical relativity and supercomputers is discussed.
Recent advances in graph neural networks have transformed structural pattern learning in domains ranging from social network analysis to biomolecular modeling. Nevertheless, practical deployments in mission-critical scenarios such as binary code similarity detection face two fundamental obstacles: first, the inherent noise in graph construction processes exemplified by incomplete control flow edges during binary function recovery; second, the substantial distribution discrepancies caused by cross-architecture instruction set variations. Conventional GNN architectures demonstrate severe performance degradation under such low signal-to-noise ratio conditions and cross-domain operational environments, particularly in security-sensitive vulnerability identification tasks where feature instability or domain shifts could trigger critical false judgments. To address these challenges, we propose GBsim, a novel approach that combines graph neural networks with natural language processing. GBsim employs a cross-architecture language model to transform binary functions into semantic graphs, leverages a multilayer GCN for structural feature extraction, and employs a Transformer layer to integrate semantic information, generates robust cross-architecture embeddings that maintain high performance despite significant distribution shifts. Extensive experiments on a large-scale cross-architecture dataset show that GBsim achieves an MRR of 0.901 and a Recall@1 of 0.831, outperforming state-of-the-art methods. In real-world vulnerability detection tasks, GBsim achieves an average recall rate of 81.3% on a 1-day vulnerability dataset, demonstrating its practical effectiveness in identifying security threats and outperforming existing methods by 2.1%. This performance advantage stems from GBsim’s ability to maximize information preservation across architectural boundaries, enhancing model robustness in the presence of noise and distribution shifts.
The WASP-47 system is notable as the first known system hosting both inner and outer low-mass planetary companions around a hot Jupiter, with an ultra-short-period (USP) planet as the innermost planetary companion. The formation of such a unique configuration poses challenges to the lonely hot Jupiter formation model. Hot Jupiters in multiple planetary systems may have a similar formation process with warm Jupiter systems, which are more commonly found with companions. This implies that the WASP-47 system could bridge our understanding of both hot and warm Jupiter formation. In this work, we propose a possible formation scenario for the WASP-47 system based on its orbital configuration. The mean motion resonance trapping, giant planet perturbations, and tidal effects caused by the central star are key factors in the formation of USP planets in multiple planetary systems with hot Jupiters. Whether a planet can become a USP planet or a short-period super-Earth planet depends on the competition between eccentricity excitation by nearby giant planet perturbations and the eccentricity damping due to tidal effects. The ${Q}_{p}^{{\prime} }$ value of the innermost planet is essential for the final planetary configuration. Our results suggest that a ${Q}_{p}^{{\prime} }$ in the range of [1, 10] is favorable for the formation of the WASP-47 system. Based on the formation scenario, we estimate an occurrence rate of 8.4% ± 2.4% for USP planets in systems similar to WASP-47.
Katherine A. Bennett, David K. Sing, Kevin B. Stevenson
et al.
Which rocky exoplanets have atmospheres? This presumably simple question is the first that must be answered to understand the prevalence of nearby habitable planets. A mere 6.9 pc from Earth, LTT 1445A is the closest transiting M dwarf system, and its largest known planet, at 1.31 R _⊕ and 424 K, is one of the most promising targets in which to search for an atmosphere. We use Hubble Space Telescope/Wide Field Camera 3 transmission spectroscopy with the G280 and G141 grisms to study the spectrum of LTT 1445Ab between 0.2 and 1.65 μ m. In doing so, we uncover an ultraviolet (UV) flare on the neighboring star LTT 1445C that is completely invisible at optical wavelengths; we report one of the first simultaneous near-UV/optical spectra of an M dwarf flare. The planet spectrum is consistent with a flat line (with median transit depth uncertainties of 128 and 52 ppm for the G280 and G141 observations, respectively), though the infrared (IR) portion displays potential features that could be explained by known opacity sources such as HCN. Some atmospheric retrievals weakly favor (∼2 σ ) an atmosphere, but it remains challenging to discern between stellar contamination, an atmosphere, and a featureless spectrum at this time. We do, however, confidently rule out ≤100× solar metallicity atmospheres. Although stellar contamination retrievals cannot fit the IR features well, the overall spectrum is consistent with stellar contamination from hot or cold spots. Based on the UV/optical data, we place limits on the extent of stellar variability expected in the near-IR (30–40 ppm), which will be critical for future James Webb Space Telescope observations.
M. Ghasemi-Nodehi, Fatemeh S. Tabatabaei, Lang Cui
General relativity has been tested in weak field regimes, but strong gravity regimes are still to be verified. The strong gravity regime with synchrotron radiation has not yet been explored. The nonthermal synchrotron emission traces the magnetic field and cosmic-ray electrons. This paper presents a test of a strong gravity regime using synchrotron radiation with two different spacetime metrics: Kerr and Cardoso, Pani, and Rico (CPR). We investigate the effects of variation in model parameters such as the spin, inclination angle, magnetic field, and nonthermal spectral index of the synchrotron radiation on flux density as a function of frequency as an observable, first in the Kerr and then in the CPR spacetime. We generate mock data observations and fit the model using Bayesian inference for both spacetimes. Assuming a uniform prior, analyzed synchrotron radiation with a Bayesian approach can distinguish Kerr and CPR spacetimes by constraining spin and deformation parameters. A Gaussian prior also allows for this distinction. However, if a Gaussian prior is used for the spin while keeping the deformation parameters uniform, only the spin can be constrained, making it impossible to differentiate between Kerr and CPR spacetime.
We present a comprehensive 3D dust-reddening map covering the entire Milky Way, constructed by combining reddening estimates based on Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST) low-resolution spectra ( E ( B − V ) _LAMOST ) with those derived from Gaia XP spectra ( E ( B − V ) _XP ), along with revised Gaia distances. E ( B − V ) _LAMOST values of ∼4.6 million unique sources were obtained with the standard-pair analysis using LAMOST DR11 stellar parameters and synthesized B- / V -band photometry from Gaia XP spectra, showing a typical precision of ∼0.01 mag. The E ( B − V ) _XP from the catalog of X. Zhang et al., which was derived using forward modeling of Gaia XP spectra, were cross-validated with E ( B − V ) _LAMOST , leading to the selection of ∼150 million high-reliability measurements. The combined data set achieves a median precision of ∼0.03 mag for E ( B − V ). To model the reddening–distance relationship along various lines of sight, we implemented a parametric approach that accounts for contributions from the Local Bubble, diffuse interstellar medium, and multiple potential molecular clouds. The sky was adaptively partitioned based on stellar density, resulting in angular resolutions ranging from 3 $\mathop{.}\limits{^{\prime} }$ 4 to 58′, with about half of the sky having a resolution better than 6 $\mathop{.}\limits{^{\prime} }$ 9. The reddening precision of our 3D map for individual stars reaches ∼0.01 mag in most regions at ∣ b ∣ > 20°, but degrades to 0.01–0.05 mag at ∣ b ∣ < 20°. The map reaches a maximum distance of 3–5 kpc in high-extinction regions with ∣ b ∣ < 5°, and extends to 10–15 kpc elsewhere. An interactive platform and Python package have been developed for utilization of the 3D dust map.
While the geodetic excitation χ(t) of polar motion p(t) is essential to improve our understanding of global mass redistributions and relative motions with respect to the terrestrial frame, the widely adopted method to derive χ(t) from p(t) has biases in both amplitude and phase responses. This study has developed a new simple but more accurate method based on the combination of the frequency- and time-domain Liouville's equation (FTLE). The FTLE method has been validated not only with 6-h sampled synthetic excitation series but also with daily and 6-h sampled polar motion measurements as well as χ(t) produced by the interactive webpage tool of the International Earth Rotation and Reference Systems Service (IERS). Numerical comparisons demonstrate that χ(t) derived from the FTLE method has superior performances in both the time and frequency domains with respect to that obtained from the widely adopted method or the IERS webpage tool, provided that the input p(t) series has a length around or more than 25 years, which presents no practical limitations since the necessary polar motion data are readily available. The FTLE code is provided in the form of MatLab function.
In modular invariant models of flavor, observables must be modular invariant. The observables discussed so far in the literature are functions of the modulus τ and its conjugate, τ¯. We point out that certain combinations of observables depend only on τ, i.e. are meromorphic, and in some cases even holomorphic functions of τ. These functions, which we dub “invariants” in this Letter, are highly constrained, renormalization group invariant, and allow us to derive many of the models' features without the need for extensive parameter scans. We illustrate the robustness of these invariants in two existing models in the literature based on modular symmetries, Γ3 and Γ5. We find that, in some cases, the invariants give rise to robust relations among physical observables that are independent of τ. Furthermore, there are instances where additional symmetries exist among the invariants. These symmetries are relevant phenomenologically and may provide a dynamical way to realize symmetries of mass matrices.