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This work focuses on particle production described by a nonminimally coupled model during inflation. In this model, three parameters determine the characteristic frequency and strength of the induced gravitational waves (GWs). Considering the impact of particle production on inflation, we identify the parameter values that generate the strongest GWs without violating the slow-roll mechanism at the CMB scale. However, even with such extreme parameters, the power spectrum of induced GWs is only about three thousandths of that of primordial GWs. This contribution remains insignificant when identifying the primary source of a detected CMB B-mode polarization. However, to precisely confirm the energy scale of inflation and extract information about quantum gravity, distinguishing between the CMB B-mode polarization from different sources is crucial. We compare the total power spectrum with that of primordial GWs, revealing a characteristic peak in the total spectrum. This peak can be used to test the model and differentiate it from other inflationary sources., Comment: 6 pages,4 figures

Early detection and localization of gravitational waves (GWs) are crucial for identifying and capturing their electromagnetic (EM) counterparts, playing a significant role in multi-messenger astronomy. For second-generation (2G) detectors such as LIGO, Virgo, and KAGRA, the typical duration of GW signals ranges from $\mathcal{O}(0.1)$ seconds to several tens of seconds due to their optimal sensitivities only at higher frequencies. This limited duration is insufficient to provide adequate early warning and localization for potential GWs and their associated EM counterparts. In this paper, we investigate whether eccentricity-induced higher harmonic modes, which enter the detector band much earlier than the dominant mode, can aid early detection and localization of GW sources using the 2G ground-based detector network. We select two typical events, a GW170817-like BNS and a GW150914-like BBH, as illustrative examples. For a GW170817-like BNS, we find that the eccentric case with $e_0=0.4$ at 10 Hz can achieve an SNR of 4 and the threshold SNR of 8 approximately 12 minutes and 5 minutes before merger, representing 4.5- and 1.5-minute improvements in time-to-merger compared to the circular case, respectively. Additionally, with $e_0=0.4$, it can achieve a localization of $1000 \, (100)\, \rm deg^2$ at 5 (1) minutes before the merger, reflecting improvements of 2 minutes (15 seconds) compared to the circular case. For a typical GW150914-like BBH, due to the much shorter signal duration, the time-to-merger gained from higher modes for achieving the same SNR and localization is limited to $\mathcal{O}(0.1)-\mathcal{O}(1)$ seconds. Our results demonstrate the usefulness of eccentricity-induced higher harmonic modes in improving early warning and localization of GW and EM counterparts, particularly for BNS systems., Comment: 8 pages, 2 figures

As next-generation gravitational-wave (GW) observatories approach unprecedented sensitivities, the need for robust methods to analyze increasingly complex, overlapping signals becomes ever more pressing. Existing matched-filtering approaches and deep-learning techniques can typically handle only one or two concurrent signals, offering limited adaptability to more varied and intricate superimposed waveforms. To overcome these constraints, we present the UnMixFormer, an attention-based architecture that not only identifies the unknown number of concurrent compact binary coalescence GW events but also disentangles their individual waveforms through a multi-decoder architecture, even when confronted with five overlapping signals. Our UnMixFormer is capable of capturing both short- and long-range dependencies by modeling them in a dual-path manner, while also enhancing periodic feature representation by incorporating Fourier Analysis Networks. Our approach adeptly processes binary black hole, binary neutron star, and neutron star-black hole systems over extended time series data (16,384 samples). When evaluating on synthetic data with signal-to-noise ratios (SNR) ranging from 10 to 50, our method achieves 99.89% counting accuracy, a mean overlap of 0.9831 between separated waveforms and templates, and robust generalization ability to waveforms with spin precession, orbital eccentricity, and higher modes, marking a substantial advance in the precision and versatility of GW data analysis., Comment: 11 pages, 7 figures

The gravitational memory effect manifests the nonlinearity of the gravitation, reflects the degenerate gravitational vacua, and indicates the types of the asymptotic symmetries. However, by the received wisdom, it would be challenging to detect it. In this Letter, we envisioned employing the space-borne interferometer, especially DECIGO, to detect memory signals generated by the stellar-mass binary black hole (BBHs) systems, the conventional targets of the ground-based detectors. We estimated that during its 5 years' observation, DECIGO could detect nearly 2,258 loud enough memory signals. Among them, 102 have signal-to-noise ratios greater than 8. Our prediction was obtained with the BBH population model constrained by the recent gravitational wave observations in GWTC-3. The Power Law + Peak mass model and the DEFAULT spin model were employed, and the merger rate was chosen to be proportional to the Madau-Dickinson formation rate. In the analysis, the impact of the orbital eccentricity was also considered. The high rate is due to the sufficiently strong memory signal right at the bandwidth of DECIGO, and also because of the humongous number of the surely existing stellar-mass BBHs. The substantial, and yet conservative, number of detections enables to leverage statistical approaches to harness the memory effect for fundamental physics and astrophysics., Comment: 11 pages, comments very welcomed

The chemical abundance measurements of host stars and their substellar companions provide a powerful tool to trace the formation mechanism of the planetary systems. We present a detailed high-resolution spectroscopic analysis of a young M-type star, DH Tau A, which is located in the Taurus molecular cloud belonging to the Taurus-Auriga star-forming region. This star is host to a low-mass companion, DH Tau b, and both star and the companion are still in their accreting phase. We apply our technique (Hejazi et al. 2024) to measure the abundances of carbon and oxygen using carbon- and oxygen-bearing molecules, such as CO and OH, respectively. We determine a near-solar carbon-to-oxygen abundance ratio of C/O=0.555$\pm$0.063 for the host star DH Tau A. We compare this stellar abundance ratio with that of the companion from our previous study (C/O=0.54$^{+0.06}_{-0.05}$, Xuan et al. 2024), which also has a near-solar value. This confirms the chemical homogeneity in the DH Tau system, which suggests a formation scenario for the companion consistent with a direct and relatively fast gravitational collapse, rather than a slow core accretion process., Comment: 14 pages, 4 figures, Accepted for publication in the Astrophysical Journal

Accurate waveform templates of binary black holes (BBHs) with eccentric orbits are essential for the detection and precise parameter estimation of gravitational waves (GWs). While SEOBNRE produces accurate time-domain waveforms for eccentric BBH systems, its generation speed remains a critical bottleneck in analyzing such systems. Accelerating template generation is crucial to data analysis improvement and valuable information extraction from observational data. We present SEOBNRE_AIq5e2, an innovative AI-based surrogate model that crafted to accelerate waveform generation for eccentric, spin-aligned BBH systems. SEOBNRE_AIq5e2 incorporates an advanced adaptive resampling technique during training, enabling the generation of eccentric BBH waveforms with mass ratios up to 5, eccentricities below 0.2, and spins $|\chi_z|$ up to 0.6. It achieves an impressive generation speed of 4.3 ms per waveform with a mean mismatch of $1.02 \times 10^{-3}$. With the exceptional accuracy and rapid performance, SEOBNRE_AIq5e2 emerges as a promising waveform template for future analysis of eccentric gravitational wave data.

Multimodal large language models (MLLMs) are increasingly being applied in the medical field, particularly in medical imaging. However, developing MLLMs for ECG signals, which are crucial in clinical settings, has been a significant challenge beyond medical imaging. Previous studies have attempted to address this by converting ECGs into several text tags using an external classifier in a training-free manner. However, this approach significantly compresses the information in ECGs and underutilizes the reasoning capabilities of LLMs. In this work, we directly feed the embeddings of ECGs into the LLM through a projection layer, retaining more information about ECGs and better leveraging the reasoning abilities of LLMs. Our method can also effectively handle a common situation in clinical practice where it is necessary to compare two ECGs taken at different times. Recent studies found that MLLMs may rely solely on text input to provide answers, ignoring inputs from other modalities. We analyzed this phenomenon from a causal perspective in the context of ECG MLLMs and discovered that the confounder, severity of illness, introduces a spurious correlation between the question and answer, leading the model to rely on this spurious correlation and ignore the ECG input. Such models do not comprehend the ECG input and perform poorly in adversarial tests where different expressions of the same question are used in the training and testing sets. We designed a de-biased pre-training method to eliminate the confounder's effect according to the theory of backdoor adjustment. Our model performed well on the ECG-QA task under adversarial testing and demonstrated zero-shot capabilities. An interesting random ECG test further validated that our model effectively understands and utilizes the input ECG signal.

Direct imaging observations are biased towards wide-separation, massive companions that have degenerate formation histories. Although the majority of exoplanets are expected to form via core accretion, most directly imaged exoplanets have not been convincingly demonstrated to follow this formation pathway. We obtained new interferometric observations of the directly imaged giant planet AF Lep b with the VLTI/GRAVITY instrument. We present three epochs of 50$\mu$as relative astrometry and the K-band spectrum of the planet for the first time at a resolution of R=500. Using only these measurements, spanning less than two months, and the Hipparcos-Gaia Catalogue of Accelerations, we are able to significantly constrain the planet's orbit; this bodes well for interferometric observations of planets discovered by Gaia DR4. Including all available measurements of the planet, we infer an effectively circular orbit ($e<0.02, 0.07, 0.13$ at $1, 2, 3 \sigma$) in spin-orbit alignment with the host, and a measure a dynamical mass of $M_\mathrm{p}=3.75\pm0.5\,M_\mathrm{Jup}$. Models of the spectrum of the planet show that it is metal rich ([M/H]$=0.75\pm0.25$), with a C/O ratio encompassing the solar value. This ensemble of results show that the planet is consistent with core accretion formation., Comment: Accepted to the Astronomical Journal. 12 figures, 4 tables

Located 10.888 pc from Earth, COCONUTS-2b is a planetary-mass companion to a young (150-800 Myr) M3 star, with a wide orbital separation (6471 au) and a low companion-to-host mass ratio ($0.021\pm0.005$). We have studied the atmospheric properties of COCONUTS-2b using newly acquired 1.0-2.5 $\mu$m spectroscopy from Gemini/Flamingos-2. The spectral type of COCONUTS-2b is refined to T$9.5 \pm 0.5$ based on comparisons with T/Y dwarf spectral templates. We have conducted an extensive forward-modeling analysis, comparing the near-infrared spectrum and mid-infrared broadband photometry with sixteen state-of-the-art atmospheric model grids developed for brown dwarfs and self-luminous exoplanets near the T/Y transition. The PH$_{3}$-free ATMO2020++, ATMO2020++, and Exo-REM models best match the specific observations of COCONUTS-2b, regardless of variations in the input spectrophotometry. This analysis suggests the presence of disequilibrium chemistry, along with a diabatic thermal structure and/or clouds, in the atmosphere of COCONUTS-2b. All models predict fainter $Y$-band fluxes than observed, highlighting uncertainties in the alkali chemistry models and opacities. We determine a bolometric luminosity of $\log{(L_{\rm bol}/L_{\odot})}=-6.18$ dex, with a 0.5 dex-wide range of $[-6.43,-5.93]$ dex that accounts for various assumptions of models. Using thermal evolution models, we derive an effective temperature of $T_{\rm eff}=483^{+44}_{-53}$ K, a surface gravity of $\log{(g)}=4.19^{+0.18}_{-0.13}$ dex, a radius of $R=1.11^{+0.03}_{-0.04}$ R$_{\rm Jup}$, and a mass of $M=8 \pm 2$ M$_{\rm Jup}$. Various atmospheric model grids consistently indicate that COCONUTS-2b's atmosphere has sub- or near-solar metallicity and C/O. These findings provide valuable insights into COCONUTS-2b's formation history and the potential outward migration to its current wide orbit., Comment: Accepted for publication in AJ. Main text: Pages 1-25, Figures 1-11, Tables 1-4; Appendix: Pages 26-43, Figures 12-15. Mostly unchanged from the previous version, except for footnotes 6-15, which were updated based on suggestions from the AJ data editor. The Gemini/F2 spectrum of COCONUTS-2b is accessible via https://doi.org/10.5281/zenodo.13975825

The transverse-traceless gauge condition is an important concept in the theory of gravitational wave. It is well known that vacuum is one of the key conditions to guarantee the existence of the transverse-traceless gauge. Although it is thin, interstellar medium is ubiquitous in the universe. Therefore, it is important to understand the concept of gravitational wave when matter is presented. Bondi-Metzner-Sachs theory has solved the gauge problem related to gravitational wave. But it does not help with the cases when gravitational wave propagates in matters. This paper discusses possible extensions of the transverse-traceless gauge condition to Minkowski perturbation with matter presented., Comment: 8 pages

We advocate for a large scale imaging survey of nearby young moving groups and star-forming regions to directly detect exoplanets over an unexplored range of masses, ages and orbits. Discovered objects will be identified early enough in JWST's lifetime to leverage its unparalleled capabilities for long-term atmospheric characterisation, and will uniquely complement the known population of exoplanets and brown dwarfs. Furthermore, this survey will constrain the occurrence of the novel wide sub-Jovian exoplanet population, informing multiple theories of planetary formation and evolution. Observations with NIRCam F200W+F444W dual-band coronagraphy will readily provide sub-Jupiter mass sensitivities beyond ~0.4" (F444W) and can also be used to rule out some contaminating background sources (F200W). At this large scale, targets can be sequenced by spectral type to enable robust self-referencing for PSF subtraction. This eliminates the need for dedicated reference observations required by GO programs and dramatically increases the overall science observing efficiency. With an exposure of ~30 minutes per target, the sub-Jupiter regime can be explored across 250 targets for ~400 hours of exposure time including overheads. An additional, pre-allocated, ~100 hours of observing time would enable rapid multi-epoch vetting of the lowest mass detections (which are undetectable in F200W). The total time required for a survey such as this is not fixed, and could be scaled in conjunction with the minimum number of detected exoplanet companions., Comment: 5 pages, 2 figures. This white paper was submitted following a call from the "Working Group on Strategic Exoplanet Initiatives with HST and JWST" (https://sites.google.com/view/exoplanet-strategy-wg, final report in 10.48550/arXiv.2404.02932)

Several pulsar timing array (PTA) groups have recently claimed the detection of nanohertz gravitational wave (GW) background, but the origin of this GW signal remains unclear. Nanohertz GWs generated by supermassive binary black holes (SMBBHs) are one of the most important GW sources in the PTA band. Utilizing data from numerical cosmology simulation, we generate mock SMBBHs within the observable universe and treat them as PTA band GW sources. We present their statistical properties, and analyze the isotropic and anisotropic characteristics of the gravitational wave background (GWB) signal they produce. Specifically, we derive the characteristic amplitude and spectrum of the GWB signal, and calculate the angular power spectrum for both GW strains/energy density and the position distribution of GW sources. We predict that the angular power spectrum of GWB energy density has $C_1/C_0\approx0.40\pm0.32$, and $C_l/C_0\simeq \frac{1}{2(2l+1)}$ (for $l>1$). Furthermore, for the upcoming Chinese Pulsar Timing Array (CPTA) and Square Kilometre Array (SKA) PTA, we predict the spatial distribution, numbers and signal-to-noise ratio (SNR) distribution of individual GW sources that may be detected with SNR>8, and study the anisotropy property in the spatial distribution of these individual GW sources., Comment: 26 pages,18 figures,1 table

Future GW observatories, such as the Einstein Telescope (ET), are expected to detect gravitational wave signals, some of which are likely to overlap with each other. This overlap may lead to misidentification as a single GW event, potentially biasing the estimated parameters of mixture GWs. In this paper, we adapt the concept of speech separation to address this issue by applying it to signal separation of overlapping GWs. We show that deep learning models can effectively separate overlapping GW signals. The proposed method may aid in eliminating biases in parameter estimation for such signals., Comment: 15 pages, 8 figures

We study the nonadiabatic dynamics of a two-dimensional higher-order topological insulator when the system is slowly quenched across the boundary-obstructed phase transition, which is characterized by edge band gap closing. We find that the number of excitations produced after the quench exhibits power-law scaling behaviors with the quench rate. Boundary conditions can drastically modify the scaling behaviors: The scaling exponent is found to be $\alpha=1/2$ for hybridized and fully open boundary conditions, and $\alpha=2$ for periodic boundary condition. We argue that the exponent $\alpha=1/2$ cannot be explained by the Kibble-Zurek mechanism unless we adopt an effective dimension $d^{\rm eff}=1$ instead of the real dimension $d=2$. For comparison, we also investigate the slow quench dynamics across the bulk-obstructed phase transitions and a single multicritical point, which obeys the Kibble-Zurek mechanism with dimension $d=2$., Comment: 6+10 pages, 3=7 figures

In the future, the third generation (3G) gravitational wave (GW) detectors, exemplified by the Einstein Telescope (ET), will be operational. The detection rate of GW from binary neutron star (BNS) is expected to reach approximately $10^4$ per year. To address the challenges posed by BNS GW data processing for 3G GW detectors, this paper explores the extraction of BNS waveforms from ET. Drawing inspiration from SPIIR's matched filtering approach, we introduce a novel framework leveraging deep learning for BNS waveform extraction. By integrating denoised outputs of time-delayed strain, we can reconstruct the embedded BNS waveform. We have established three distinct BNS GW denoising models, each tailored to address the early inspiral, later inspiral, and merger phases of BNS GW, respectively. To further regulate the waveform shape, we propose the Amplitude Regularity Model that takes denoised output as input and regulated waveform as output. The experiments conducted on test data demonstrate the efficacy of the denoising models, the Amplitude Regularity Models, as well as the overall waveform construction method. To the best of our knowledge, this marks the first instance of deep learning being utilized for the task of BNS waveform extraction. We believe that the proposed method holds promise for early warning, searching, and localization of BNS GWs., Comment: 14 pages, 16 figures

With a dynamical mass of $3 \, M_\mathrm{Jup}$, the recently discovered giant planet AF Lep b is the lowest-mass imaged planet with a direct mass measurement. Its youth and spectral type near the L/T transition make it a promising target to study the impact of clouds and atmospheric chemistry at low surface gravities. In this work, we present JWST/NIRCam imaging of AF Lep b. Across two epochs, we detect AF Lep b in F444W ($4.4 \, \mathrm{\mu m}$) with S/N ratios of $9.6$ and $8.7$, respectively. At the planet's separation of $320 \, \mathrm{mas}$ during the observations, the coronagraphic throughput is ${\approx}7\%$, demonstrating that NIRCam's excellent sensitivity persists down to small separations. The F444W photometry of AF Lep b affirms the presence of disequilibrium carbon chemistry and enhanced atmospheric metallicity. These observations also place deep limits on wider-separation planets in the system, ruling out $1.1 \, M_\mathrm{Jup}$ planets beyond $15.6 \, \mathrm{au}$ ($0.58$ arcsec), $1.1 \, M_\mathrm{Sat}$ planets beyond $27 \, \mathrm{au}$ ($1$ arcsec), and $2.8 \, M_\mathrm{Nep}$ planets beyond $67 \, \mathrm{au}$ ($2.5$ arcsec). We also present new Keck/NIRC2 $L'$ imaging of AF Lep b; combining this with the two epochs of F444W photometry and previous Keck $L'$ photometry provides limits on the long-term $3{-}5 \, \mathrm{\mu m}$ variability of AF Lep b on months-to-years timescales. AF Lep b is the closest-separation planet imaged with JWST to date, demonstrating that planets can be recovered well inside the nominal (50\% throughput) NIRCam coronagraph inner working angle., Comment: 17 pages, 4 figures, accepted in ApJL

In the preclinical translational studies, drug candidates with remarkable anti-epileptic efficacy demonstrate long-term suppression of spontaneous recurrent seizures (SRSs), particularly convulsive seizures (CSs), in mouse models of chronic epilepsy. However, the current methods for monitoring CSs have limitations in terms of invasiveness, specific laboratory settings, high cost, and complex operation, which hinder drug screening efforts. In this study, a camera-based system for automated detection of CSs in chronically epileptic mice is first established to screen potential anti-epilepsy drugs.

We synthesize JWST NIRCam photometry for the F164N, F187N, F212N narrow filters, F140M, F162M, F182M, F210M medium filters, and F115W, F150W, F200W wide filters, Euclid Near Infrared Spectrometer and Photometer (NISP) photometry for the $Y_E J_E H_E$ filters, and Roman Wide Field Instrument (WFI) photometry for the F106, F129, F146, F158, F184 and F213 filters using SpeX prism spectra and parallaxes of 688 field-age and 151 young ($\lesssim$ 200 Myr) ultracool dwarfs (spectral types M6-T9). We derive absolute magnitude-spectral type polynomial relations that enable the calculation of photometric distances for ultracool dwarfs observed with JWST, and to be observed with Euclid and Roman, in the absence of parallax measurements. Additionally, using the synthesized photometry to generate color-color figures can help distinguish high-redshift galaxies from brown dwarf interlopers in survey datasets. In particular, anticipating the upcoming Euclid Early Release Observations, we provide synthetic Euclid colors for ultracool dwarfs in our sample., Comment: 6 pages, 3 figures, 1 table

We advocate for the prioritization of high-precision photometric monitoring of exoplanet and brown dwarf companions to detect brightness variability arising from features in their atmospheres. Measurements of photometric variability provide not only an insight into the physical appearances of these companions, but are also a direct probe of their atmospheric structures and dynamics, and yield valuable estimates of their rotation periods. JWST is uniquely capable of monitoring faint exoplanet companions over their full rotation periods, thanks to its inherent stability and powerful high-contrast coronagraphic imaging modes. Rotation period measurements can be further combined with measurements of v sin i obtained using high-resolution spectroscopy to infer the viewing angle of a companion. Photometric monitoring over multiple rotation periods and at multiple epochs will allow both short- and long-term time evolution in variability signals to be traced. Furthermore, the differences between the layers in a companion's atmosphere can be probed by obtaining simultaneous photometric monitoring at different wavelengths through NIRCam dual-band coronagraphy. Overall, JWST will reach the highest sensitivities to variability to date and enable the light curves of substellar companions to be characterised with unprecedented cadence and precision at the sub-percent level., Comment: 4 pages, 2 figures, white paper submitted in response to the call by the Working Group on Strategic Exoplanet Initiatives with HST and JWST (details at https://outerspace.stsci.edu/display/HPR/Strategic+Exoplanet+Initiatives+with+HST+and+JWST & final report at arXiv:2404.02932), adapted to include author list and affiliations

The development of large language models (LLMs) has brought unprecedented possibilities for artificial intelligence (AI) based medical diagnosis. However, the application perspective of LLMs in real diagnostic scenarios is still unclear because they are not adept at collecting patient data proactively. This study presents a LLM-based diagnostic system that enhances planning capabilities by emulating doctors. Our system involves two external planners to handle planning tasks. The first planner employs a reinforcement learning approach to formulate disease screening questions and conduct initial diagnoses. The second planner uses LLMs to parse medical guidelines and conduct differential diagnoses. By utilizing real patient electronic medical record data, we constructed simulated dialogues between virtual patients and doctors and evaluated the diagnostic abilities of our system. We demonstrated that our system obtained impressive performance in both disease screening and differential diagnoses tasks. This research represents a step towards more seamlessly integrating AI into clinical settings, potentially enhancing the accuracy and accessibility of medical diagnostics., Comment: Work in Progress

HD 21997 is host to a prototypical "hybrid" debris disk characterized by debris disk-like dust properties and a CO gas mass comparable to a protoplanetary disk. We use Transiting Exoplanet Survey Satellite time series photometry to demonstrate that HD 21997 is a high-frequency delta Scuti pulsator. If the mode identification can be unambiguously determined in future works, an asteroseismic age of HD 21997 may become feasible., Comment: 3 pages, 1 figure, submitted to RNAAS

Giant planets grow by accreting gas through circumplanetary disks, but little is known about the timescale and mechanisms involved in the planet assembly process because few accreting protoplanets have been discovered. Recent visible and infrared (IR) imaging revealed a potential accreting protoplanet within the transition disk around the young intermediate-mass Herbig Ae star, AB Aurigae (AB Aur). Additional imaging in H$\alpha$ probed for accretion and found agreement between the line-to-continuum flux ratio of the star and companion, raising the possibility that the emission source could be a compact disk feature seen in scattered starlight. We present new deep Keck/NIRC2 high-contrast imaging of AB Aur to characterize emission in Pa$\beta$, another accretion tracer less subject to extinction. Our narrow band observations reach a 5$\sigma$ contrast of 9.6 mag at 0.6$''$, but we do not detect significant emission at the expected location of the companion, nor from other any other source in the system. Our upper limit on Pa$\beta$ emission suggests that if AB Aur b is a protoplanet, it is not heavily accreting or accretion is stochastic and was weak during the observations., Comment: Accepted for publication in The Astronomical Journal

Gravitational wave (GW) astronomy has opened new frontiers in understanding the cosmos, while the integration of artificial intelligence (AI) in science promises to revolutionize data analysis methodologies. However, a significant gap exists, as there is currently no dedicated platform that enables scientists to develop, test, and evaluate AI algorithms efficiently. To address this gap, we introduce GWAI, a pioneering AI-centered software platform designed for gravitational wave data analysis. GWAI contains a three-layered architecture that emphasizes simplicity, modularity, and flexibility, covering the entire analysis pipeline. GWAI aims to accelerate scientific discoveries, bridging the gap between advanced AI techniques and astrophysical research., Comment: 10 pages, 5 figures

As with the laser interferometer gravitational-wave observatory (LIGO), the matched filtering technique will be critical to the data analysis of gravitational wave detection by space-based detectors, including LISA, Taiji and Tianqin. Waveform templates are the basis for such matched filtering techniques. To construct ready-to-use waveform templates, numerical relativity waveforms are a starting point. Therefore, the accuracy issue of numerical relativity waveforms is critically important. There are many investigations regarding this issue with respect to LIGO. But unfortunately there are few results on this issue with respect to space-based detectors. The current paper investigates this problem. Our results indicate that the existing numerical relativity waveforms are as accurate as 99% with respect to space-based detectors, including LISA, Taiji and Tianqin. Such an accuracy level is comparable to that with respect to LIGO.

The search for Galactic binary gravitational waves is a critical challenge for future space-based gravitational wave detectors, such as LISA. We propose an innovative approach to simultaneously explore gravitational waves originating from Galactic binaries by developing a new Local Maxima Particle Swarm Optimization (LMPSO) algorithm. Our method identifies local maxima in the $\mathcal{F}$-statistic and applies astrophysical models and the properties of the $\mathcal{F}$-statistic within parameter space to uncover Galactic binary gravitational wave signals in the dataset. This new approach effectively addresses the inaccuracies often associated with signal subtraction contamination, a challenge for traditional iterative subtraction methods, particularly when dealing with low signal-to-noise ratio (SNR) signals (e.g., SNR $<$ 15). We also account for the effects of overlapping signals and degeneracy noise. To demonstrate the effectiveness of our approach, we use residuals from the LISA mock data challenge (LDC1-4), where 10,982 injected sources with SNR $\ge$ 15 have been removed. For the remaining low-SNR sources (SNR $<$ 15), our method efficiently identifies 6,508 signals, achieving a 63.2\% detection rate.

Space-based gravitational wave (GW) detectors are expected to detect the stellar-mass binary black holes (SBBHs) inspiralling in the low-frequency band, which exist in several years before the merger. Accurate GW waveforms in the inspiral phase are crucial for the detection and analysis of those SBBHs. In our study, based on post-Newtonian (PN) models, we investigate the differences in the detection, accuracy requirement, and parameter estimation of SBBHs in the cases of LISA, Taiji, and their joint detection. We find that low-order PN models are sufficient for simulating low-mass ($\le 50\ \mathrm{M}_\odot$) SBBHs population. Moreover, for detectable SBBHs in space-based GW detectors, over 90% of the GW signals from low-order PN models meet accuracy requirement. Additionally, different PN models do not exhibit significant differences in Bayesian inference. Our research provides a comprehensive reference for balancing computational resources and the desired accuracy of GW waveform generation. It highlights the suitability of low-order PN models for simulating SBBHs and emphasizes their potential in the detection and parameter estimation of SBBHs., Comment: 16 pages, 11 figures

When it comes to long-wavelength gravitational waves (GWs), diffraction effect becomes significant when these waves are lensed by celestial bodies. Typically, the traditional diffraction integral formula neglects large-angle diffraction, which is often adequate for most of cases. Nonetheless, there are specific scenarios, such as when a GW source is lensed by a supermassive black hole in a binary system, where the lens and source are in close proximity, where large-angle diffraction can play a crucial role. In our prior research, we have introduced an exact, general diffraction integral formula that accounts for large-angle diffraction as well. This paper explores the disparities between this exact diffraction formula and the traditional, approximate one under various special conditions. Our findings indicate that, under specific parameters, such as a lens-source distance of $D_{\rm LS}=0.1$\,AU and a lens mass of $M_{\rm L}=4\times10^{6}M_\odot$, the amplification factor for the exact diffraction formula is notably smaller than that of the approximate formula, differing by a factor of approximately $r_F\simeq0.806$. This difference is substantial enough to be detectable. Furthermore, our study reveals that the proportionality factor $r_F$ gradually increases from 0.5 to 1 as $D_{\rm LS}$ increases, and decreases as $M_{\rm L}$ increases. Significant differences between the exact and approximate formulas are observable when $D_{\rm LS}\lesssim0.2$ AU (assuming $M_{\rm L}=4\times10^{6}M_\odot$) or when $M_{\rm L}\gtrsim2\times10^6M_\odot$ (assuming $D_{\rm LS}=0.1$ AU). These findings suggest that there is potential to validate our general diffraction formula through future GW detections., Comment: 17 pages, 7 figures, comments are welcome

HIP 65426 hosts a young giant planet that has become the first exoplanet directly imaged with JWST. Using time-series photometry from the Transiting Exoplanet Survey Satellite (TESS), we classify HIP 65426 as a high-frequency $\delta$ Scuti pulsator with a possible large frequency separation of $\Delta \nu =$7.23$\pm$0.02 cycles day$^{-1}$. We check the TESS data for pulsation timing variations and use the nondetection to estimate a 95% dynamical mass upper limit of 12.8 Mjup for HIP 65426 b. We also identify a low-frequency region of signal that we interpret as stellar latitudinal differential rotation with two rapid periods of 7.85$\pm$0.08 hr and 6.67$\pm$0.04 hr. We use our TESS rotation periods together with published values of radius and $v \sin{i}$ to jointly measure the inclination of HIP 65426 to $i_{\star}=107_{-11}^{+12}$$^\circ$. Our stellar inclination is consistent with the orbital inclination of HIP 65426 b ($108_{-3}^{+6}$$^{\circ}$) at the $68\%$ percent level based on our orbit fit using published relative astrometry. The lack of significant evidence for spin-orbit misalignment in the HIP 65426 system supports an emerging trend consistent with preferential alignment between imaged long-period giant planets and their host stars., Comment: 18 pages, 9 figures, 2 tables. Accepted to AJ after minor constructive revisions. Uncertainty on HIP65426 inclination is now more realistic; Figures 5 and 7 are updated accordingly

The unprecedented medium-resolution (R~1500-3500) near- and mid-infrared (1-18um) spectrum provided by JWST for the young (140+/-20Myr) low-mass (12-20MJup) L-T transition (L7) companion VHS1256b gives access to a catalogue of molecular absorptions. In this study, we present a comprehensive analysis of this dataset utilizing a forward modelling approach, applying our Bayesian framework, ForMoSA. We explore five distinct atmospheric models to assess their performance in estimating key atmospheric parameters: Teff, log(g), [M/H], C/O, gamma, fsed, and R. Our findings reveal that each parameter's estimate is significantly influenced by factors such as the wavelength range considered and the model chosen for the fit. This is attributed to systematic errors in the models and their challenges in accurately replicating the complex atmospheric structure of VHS1256b, notably the complexity of its clouds and dust distribution. To propagate the impact of these systematic uncertainties on our atmospheric property estimates, we introduce innovative fitting methodologies based on independent fits performed on different spectral windows. We finally derived a Teff consistent with the spectral type of the target, considering its young age, which is confirmed by our estimate of log(g). Despite the exceptional data quality, attaining robust estimates for chemical abundances [M/H] and C/O, often employed as indicators of formation history, remains challenging. Nevertheless, the pioneering case of JWST's data for VHS1256b has paved the way for future acquisitions of substellar spectra that will be systematically analyzed to directly compare the properties of these objects and correct the systematics in the models., Comment: 32 pages, 16 figures, 6 tables, 2 appendices

Measurements of the C/O ratio in brown dwarfs are lacking, in part due to past models adopting solar C/O only. We have expanded the ATMO 2020 atmosphere model grid to include non-solar metallicities and C/O ratios in the T dwarf regime. We change the C/O ratio by altering either the carbon or oxygen elemental abundances, and we find that non-solar abundances of these elements can be distinguished based on the shapes of the $H$- and $K$- bands. We compare these new models with medium-resolution ($R\approx1700$), near-infrared ($0.8-2.4\,\mu$m) Gemini/GNIRS spectra of three benchmark late-T dwarfs, GJ 570D, HD 3651B, and Ross 458C. We find solar C/O ratios and best-fitting parameters ($T_\mathrm{eff}$, $\log(g)$, $Z$) broadly consistent with other analyses in the literature based on low-resolution ($R\sim100$) data. The model-data discrepancies in the near-infrared spectra are consistent across all three objects. These discrepancies are alleviated when fitting the Y, J, H and K bands individually, but the resulting best-fit parameters are inconsistent and disagree with the results from the full-spectrum. By examining the model atmosphere properties we find this is due to the interplay of gravity and metallicity on $\mathrm{H_2-H_2}$ collisionally induced absorption. We therefore conclude that there are no significant issues with the molecular opacity tables used in the models at this spectral resolution. Instead, deficiencies are more likely to lie in the model assumptions regarding the thermal structures. Finally, we find a discrepancy between the GNIRS, SpeX, and other near-infrared spectra in the literature of Ross 458C, indicating potential spectroscopic variability., Comment: 63 pages, 29 Figures, 7 Tables. Accepted in the Astrophysical Journal. Models and data available on http://opendata.erc-atmo.eu

The scalefree non-Hermitian skin effect (NHSE) refers to the phenomenon that the localization length of skin modes scales proportionally with system size in non-Hermitian systems. Authors of recent studies have demonstrated that the scalefree NHSE can be induced through various mechanisms, including the critical NHSE, local non-Hermiticity, and the boundary impurity effect. Nevertheless, these methods require careful modeling and precise parameter tuning. In contrast, in this paper, we suggest that the scalefree NHSE is a universal phenomenon, observable in extensive systems if these systems can be described by non-Bloch band theory and host Bloch points on the energy spectrum in the thermodynamic limit. Crucially, we discover that the geometry of the generalized Brillouin zone determines the scaling rule of the localization length, which can scale either linearly or quadratically with the system size. In this paper, we enriches the phenomenon of the scalefree NHSE.

We present a photometric variability survey of young planetary-mass objects using the New Technology Telescope in the Js and Ks bands. Surface gravity plays an important role in the atmospheric structure of brown dwarfs, as young low gravity L dwarfs have a higher variability rate than field L dwarfs. In this study, we extend variability studies to young T-type planetary-mass objects and investigate the effects of surface gravity on the variability of L and T dwarfs across a large sample. We conduct continuous monitoring for 18 objects with spectral types from L5 to T8 and detect four new variables and two variable candidates. Combining with previous variability surveys of field and young L and T objects, we find that young objects tend to be more variable than field objects within peak-to-peak variability amplitude ranges of 0.5-10 per cent and period ranges of 1.5-20 hr. For the first time, we constrain the variability rate of young T dwarfs to be 56 per cent compared to 25 per cent for field T dwarfs. Both field and young samples have higher variability rates at the L/T transition than outside the L/T transition. The differences in the variability rates between field and young samples are about 1 sigma and therefore larger sample sizes are needed to confirm and refine the results. Besides the L/T transition, young L dwarfs with strong variability tend to assemble in a narrow spectral type range of L6-L7.5. This work supports the critical role of surface gravity on the atmospheric structure from L to T spectral types., Comment: Accepted for publication in MNRAS, 23 pages of main text + 26 pages of appendix + 5 pages of online supplementary material

We examine the relationship between metallicity and $J-K$ color for 64 benchmark late-M and L dwarfs, all of which are wide companions to higher mass stars, and 6 of which are new discoveries. We assess the correlation between the $\Delta(J-K)$ color anomaly (the difference of an object's $J-K$ color with the median color for field objects of the same spectral type) and the host star metallicity to investigate how metallicity affects ultracool photospheres. Using Spearman's rank correlation test and Student's t test, the late-M dwarf (L dwarf) sample's $\Delta(J-K)$ and metallicity show a positive correlation with 95\% (90\%) confidence level. A linear fit to color anomaly as a function of metallicity finds a slope of $0.17\pm0.07$ for the late-M dwarfs and a slope of $0.20^{+0.07}_{-0.08}$ for the L dwarfs. We also computed the $\Delta(J-K)$ versus metallicity relationship predicted by multi-metallicity model spectra generated using Drift-Phoenix. The modeled late-M dwarfs show a slope of 0.202$\pm$0.03, which is close to our observational results, but the modeled L dwarfs show a slope of 0.493$\pm$0.02, steeper than our observational results. Both our empirical results and the models indicate that more metal-rich objects should appear redder photometrically. We speculate that higher metallicity drives more condensate formation in these atmospheres, thus making these ultracool dwarfs appear redder.

We present a uniform forward-modeling analysis of 90 late-M and L dwarfs in nearby young (~$10-200$ Myr) moving groups, the Pleiades, and the Hyades using low-resolution ($R\approx150$) near-infrared ($0.9-2.4$ $\mathrm{\mu m}$) spectra and the BT-Settl model atmospheres. We derive the objects' effective temperatures, surface gravities, radii, and masses by comparing our spectra to the models using a Bayesian framework with nested sampling and calculate the same parameters using evolutionary models. Assuming the evolutionary-based parameters are more robust, our spectroscopically inferred parameters from BT-Settl exhibit two types of systematic behavior for objects near the M-L spectral type boundary. Several are clustered around $T_\mathrm{eff} \approx 1800$ K and $\log g\approx5.5$ dex, implying impossibly large masses ($150-1400$ $M_\mathrm{Jup}$), while others are clustered around $T_\mathrm{eff}\gtrsim3000$ K and $\log g\lesssim3.0$ dex, implying non-physical low masses and unreasonably young ages. We find the fitted BT-Settl model spectra tend to overpredict the peak $J$ and $H$-band flux for objects located near the M-L boundary, suggesting the dust content included in the model atmospheres is insufficient to match the observations. By adding an interstellar medium-like reddening law to the BT-Settl model spectra, we find the fits between models and observed spectra are greatly improved, with the largest reddening coefficients occurring at the M-L transition. This work delivers a systematic examination of the BT-Settl model atmospheres and constitutes the largest spectral analysis of benchmark late-M and L-type brown dwarfs to date., Comment: ApJ, in Press

Space-based gravitational wave (GW) detection is one of the most anticipated GW detection projects in the next decade, which promises to detect abundant compact binary systems. At present, deep learning methods have not been widely explored for GW waveform generation and extrapolation. To solve the data processing difficulty and the increasing waveform complexity caused by the detector's response and second-generation time-delay interferometry (TDI 2.0), an interpretable pre-trained large model named CBS-GPT (Compact Binary Systems Waveform Generation with Generative Pre-trained Transformer) is proposed. For compact binary system waveforms, three models were trained to predict the waveforms of massive black hole binaries (MBHB), extreme mass-ratio inspirals (EMRIs), and galactic binaries (GB), achieving prediction accuracies of at most 99%, 91%, and 99%, respectively. The CBS-GPT model exhibits notable generalization and interpretability, with its hidden parameters effectively capturing the intricate information of waveforms, even with the complex instrument response and a wide parameter range. Our research demonstrates the potential of large models in the GW realm, opening up new opportunities and guidance for future researches such as complex waveforms generation, gap completion, and deep learning model design for GW science.

We present aperture masking interferometry (AMI) observations of the star HIP 65426 at $3.8\,\rm{\mu m}$ as a part of the JWST Direct Imaging Early Release Science (ERS) program obtained using the Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument. This mode provides access to very small inner working angles (even separations slightly below the Michelson limit of $0.5\lambda/D$ for an interferometer), which are inaccessible with the classical inner working angles of the JWST coronagraphs. When combined with JWST's unprecedented infrared sensitivity, this mode has the potential to probe a new portion of parameter space across a wide array of astronomical observations. Using this mode, we are able to achieve a $5\sigma$ contrast of $\Delta m{\sim}7.62{\pm}0.13$ mag relative to the host star at separations ${\gtrsim}0.07{"}$, and the contrast deteriorates steeply at separations ${\lesssim}0.07{"}$. However, we detect no additional companions interior to the known companion HIP 65426 b (at separation ${\sim}0.82{"}$ or, $87^{+108}_{-31}\,\rm{au}$). Our observations thus rule out companions more massive than $10{-}12\,\rm{M_{Jup}}$ at separations ${\sim}10{-}20\,\rm{au}$ from HIP 65426, a region out of reach of ground or space-based coronagraphic imaging. These observations confirm that the AMI mode on JWST is sensitive to planetary mass companions at close-in separations (${\gtrsim}0.07{"}$), even for thousands of more distant stars at $\sim$100 pc, in addition to the stars in the nearby young moving groups as stated in previous works. This result will allow the planning and successful execution of future observations to probe the inner regions of nearby stellar systems, opening an essentially unexplored parameter space., Comment: 23 pages, 14 figures, accepted for publication in ApJL

We present a performance analysis for the aperture masking interferometry (AMI) mode on board the James Webb Space Telescope Near Infrared Imager and Slitless Spectrograph (JWST/NIRISS). Thanks to self-calibrating observables, AMI accesses inner working angles down to and even within the classical diffraction limit. The scientific potential of this mode has recently been demonstrated by the Early Release Science (ERS) 1386 program with a deep search for close-in companions in the HIP 65426 exoplanetary system. As part of ERS 1386, we use the same data set to explore the random, static, and calibration errors of NIRISS AMI observables. We compare the observed noise properties and achievable contrast to theoretical predictions. We explore possible sources of calibration errors and show that differences in charge migration between the observations of HIP 65426 and point-spread function calibration stars can account for the achieved contrast curves. Lastly, we use self-calibration tests to demonstrate that with adequate calibration NIRISS F380M AMI can reach contrast levels of $\sim9-10$ mag at $\gtrsim \lambda/D$. These tests lead us to observation planning recommendations and strongly motivate future studies aimed at producing sophisticated calibration strategies taking these systematic effects into account. This will unlock the unprecedented capabilities of JWST/NIRISS AMI, with sensitivity to significantly colder, lower-mass exoplanets than lower-contrast ground-based AMI setups, at orbital separations inaccessible to JWST coronagraphy., Comment: 20 pages, 12 figures, accepted to Astrophysical Journal Letters

The early and precise localization of gravitational waves (GWs) is pivotal in detecting their electromagnetic (EM) counterparts, especially for binary neutron stars (BNS) and neutron star-black hole binaries (NSBH). In this letter, we pioneer the exploration of utilizing the higher harmonic modes induced by the eccentricity of compact binaries to localize GWs with ground-based detectors even before the quadrupole baseline $\ell=2$ mode enters the detector band. Our theoretical analysis marks a first in proposing a strategy for gaining the earliest possible warning and maximizing preparation time for observing pre- and/or post-merger EM counterparts. We simulate three typical binaries from GWTC-3 with eccentricities ranging from 0.05 to 0.4. Our results reveal that the third-generation (3G) detectors (low frequency cut-off $f_0=5$ Hz) can accumulate sufficient signal-to-noise ratios through higher modes before the onset of the baseline $\ell=2$ mode entry into the band. Notably, relying solely on the higher modes, the 3G detector network ET+2CE achieves an average localization on the order of $1-10^2~\rm deg^2$ around 1-1.8 hours before the merger of a GW170817-like BNS, and $10-10^3~\rm deg^2$ approximately 18-30 minutes prior to the merger of a GW200115-like NSBH. A $100~\rm deg^2$ localization is attainable even 2-4 hours prior to a BNS merger. Moreover, in the near face-on orientations which are generally more favorable for EM counterpart detection, the localization can be further improved., Comment: 8 pages, 2 figures, published in PRD