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Wenda Zhang

Publications and source records attributed to Wenda Zhang.

At least 19 recordsLinked to original sources

ER-EDF: A Psychology-Grounded Emotion Regulation Framework for Speech Empathetic Dialogue Generation in Large Audio-Language Models

Empathetic response generation in spoken dialogue systems requires both accurate emotion perception and appropriate emotion regulation. Grounded in psychological theories such as the Perception-Action Model and emotion regulation theory, effective empathy depends not only on inferring a user's affective state but also on regulating how it is expressed in responses. However, recent large audio-language models (LALMs) largely treat emotion as a direct conditioning signal, lacking explicit regulatory mechanisms, which often leads to affect mirroring rather than calibrated support. We propose ER-EDF, a psychology-grounded framework that explicitly decouples emotion perception and emotion regulation in LALMs. Perception tracks the user's emotional state, while regulation determines how this state should guide empathetic response generation. The framework is model-agnostic and integrates seamlessly into existing LALMs. We further construct a spoken empathetic dialogue dataset and introduce empathy-aware evaluation metrics beyond lexical matching. Experiments across five LALMs and two datasets show that ER-EDF consistently improves empathetic response quality in both automatic and human evaluations, highlighting the importance of jointly modeling emotion perception and regulation in spoken empathetic dialogue systems, paving a new direction for psychologically grounded empathetic AI.

cs.AI

Modeling surface radiation of rotating neutron stars with Monk-NS

Neutron stars serve as unique laboratories for studying ultra-dense nuclear matter. The equation of state of neutron star matter can be effectively constrained by their masses and radii. Particular attention has been paid to rapidly rotating neutron stars, where strong relativistic effects leave imprints on their electromagnetic emission. To model the emission of rotating neutron stars in more realistic situations, especially when their surface emission is further re-processed by a scattering medium, we develop Monk-NS, a customized version of the general relativistic Monte-Carlo radiative transfer code Monk. We validate the code through a series of benchmarking tests, including computing the energy spectrum, pulse profile, and polarisation of rotating neutron stars, and comparing the results with those of the established codes in the X-ray timing community, yielding consistent outcomes. As an example to demonstrate Monk-NS's capabilities, we apply it to investigate various models proposed to explain the low pulsation amplitude of neutron star low-mass X-ray binaries. Our findings indicate that the dependence of the X-ray polarisation degree on the observer's inclination can serve as a key factor in distinguishing these models. We also find that complex hotspot morphologies yield polarisation properties different from those of circular hotspots.

astro-ph.HE

Evidence for a Delayed UV Counterpart to X-ray Quasi-periodic Eruptions in Ansky

X-ray quasi-periodic eruptions (QPEs) represent a novel population of extreme, repeating nuclear transients whose physical origins remain debated. A defining characteristic of QPEs has been their exclusive detection in the X-ray band, with a notable absence of correlated multi-wavelength counterparts. Here we report the first detection of a recurrent UV response temporally coupled to the X-ray QPE signal in the source Ansky/ZTF19acnskyy. The UV emission displays coherent periodic modulations over five consecutive cycles, systematically lagging the X-ray eruptions by $0.96^{+0.38}_{-0.39}$ days, with a cross-correlation coefficient of $r_{\rm max} \sim 0.6$. We suggest that the detectability of this corresponding signal may be enabled by Ansky's unusually long recurrence timescale, which could reduce the temporal smearing of the UV response seen in more rapid QPEs. The observed delay may correspond to a diffusion timescale associated with heated blobs. However, we cannot exclude the possibility that the lag corresponds to the light-crossing time associated with X-ray irradiation that originates near the central black hole and propagates to the outer UV-emitting region. While numerous QPE models have been proposed, any viable model for Ansky must be able to simultaneously explain the presence of a UV counterpart, its measured time lag, and the previously observed steadily increasing recurrence period.

astro-ph.HE

Scaling Ambiguity: Augmenting Human Annotation in Speech Emotion Recognition with Audio-Language Models

Speech Emotion Recognition models typically use single categorical labels, overlooking the inherent ambiguity of human emotions. Ambiguous Emotion Recognition addresses this by representing emotions as probability distributions, but progress is limited by unreliable ground-truth distributions inferred from sparse human annotations. This paper explores whether Large Audio-Language Models (ALMs) can mitigate the annotation bottleneck by generating high-quality synthetic annotations. We introduce a framework leveraging ALMs to create Synthetic Perceptual Proxies, augmenting human annotations to improve ground-truth distribution reliability. We validate these proxies through statistical analysis of their alignment with human distributions and evaluate their impact by fine-tuning ALMs with the augmented emotion distributions. Furthermore, to address class imbalance and enable unbiased evaluation, we propose DiME-Aug, a Distribution-aware Multimodal Emotion Augmentation strategy. Experiments on IEMOCAP and MSP-Podcast show that synthetic annotations enhance emotion distribution, especially in low-ambiguity regions where annotation agreement is high. However, benefits diminish for highly ambiguous emotions with greater human disagreement. This work provides the first evidence that ALMs could address annotation scarcity in ambiguous emotion recognition, but highlights the need for more advanced prompting or generation strategies to handle highly ambiguous cases.

eess.AS

A fast powerful X-ray transient from possible tidal disruption of a white dwarf

Stars captured by black holes (BHs) can be torn apart by strong tidal forces, producing electromagnetic flares. To date, more than 100 tidal disruption events (TDEs) have been observed, each involving invariably normal gaseous stars whose debris falls onto the BH, sustaining the flares over years. White dwarfs (WDs), which are the most prevalent compact stars and a million times denser--and therefore tougher--than gaseous stars, can only be disrupted by intermediate-mass black holes (IMBHs) of 10^2--10^5 solar masses. WD-TDEs are considered to generate more powerful and short-lived flares, but their evidence has been lacking. Here we report observations of a fast and luminous X-ray transient EP250702a detected by Einstein Probe. Its one-day-long X-ray peak as luminous as 10^(47-49) erg/s showed strong recurrent flares with hard spectra extending to several tens of MeV gamma-rays, as detected by Fermi/GBM and Konus-Wind, indicating relativistic jet emission. The jet's X-ray dropped sharply from 3 x 10^49 erg/s to around 10^44 erg/s within 20 days (10 days in the source rest frame). These characteristics are inconsistent with any known transient phenomena other than a jetted-TDE evolving over an unprecedentedly short timescale, indicating the disruption of a WD by an IMBH. At late times, a new soft component progressively dominates the X-ray spectrum, exhibiting an extreme super-Eddington luminosity, which possibly originates from an accretion disc. WD-TDEs open a new window for investigating the elusive IMBHs and their surrounding stellar environments, and they are prime sources of gravitational waves in the band of space-based interferometers.

astro-ph.HE

Interaction between disk and extended corona in a general relativistic framework

The energy equilibrium between the corona and the underlying disk in a two-phase accretion flow sets a lower limit on the achievable photon index. A slab corona may not explain the hard state observations of X-ray binaries (XRBs). We incorporate energy feedback to the accretion disk resulting from illumination by an extended corona, and vice versa. The interaction between these two components allows for the possibility of finding an energetically self-consistent equilibrium solution for a given disk-corona system. We have upgraded the existing Monte Carlo radiative transfer code, MONK, to incorporate the interaction between the disk and the extended corona within the general relativistic framework. We introduce an albedo parameter to specify the fraction of the incident flux that is reflected by the disk, while the remainder is absorbed and added to the intrinsic dissipation. Reflection is modeled assuming a semi-infinite electron atmosphere. We find global equilibrium solutions by iterating interaction between disk and extended slab corona. A higher black hole spin, higher coronal temperature, and higher albedo all lead to harder spectra. For typical coronal temperatures and disk albedo, the lowest achievable photon index with a static slab corona fully covering the disk is approximately 1.7-1.8. With the upgraded version of MONK, we are now able to achieve global energy equilibrium for a given disk-corona system. This approach holds significant potential for constraining the coronal geometry using not only the observed flux but also polarization. A static slab does not appear to be a favorable coronal geometry for the hard state of XRBs, even when global energy balance is taken into account. In future work, we will explore truncated disk geometries and outflowing coronae as potential alternatives. (shortened)

astro-ph.HE

Possible Coronal Geometry in the Hard and Soft State of Black Hole X-ray Binaries from MONK Simulations

Understanding the coronal geometry in different states of black hole X-ray binaries is important for more accurate modeling of the system. However, it is difficult to distinguish different geometries by fitting the observed Comptonization spectra. In this work, we use the Monte Carlo ray-tracing code MONK to simulate the spectra for three simple corona toy models widely proposed in observational studies: sandwich, spherical, and lamppost, varying their optical depth and size (height). By fitting the simulated NuSTAR observations with the simplcut*kerrbb model, we infer the possible parameter space for the hard state and soft state of different coronal geometries. The influence of the disk inclination angle, black hole spin and coronal temperature is discussed. We find that in the lamppost model, if we exclude the case of a very extended corona, the disk emission is always dominant, making the lamppost geometry incompatible with the hard state. While the sandwich and spherical models can produce similar spectra in both the hard and soft states, the simulated IXPE polarimetric spectra show the potential to break this degeneracy. Geometrical effects arising from the limited size of the corona become evident in lower-spin black holes and affect the spectral fitting, where the larger ISCO reduces the corona coverage of the inner disk.

astro-ph.HE

Tidal disruption events in active galactic nuclei: on orbital inclination and Schwarzschild apsidal precession

Tidal disruption events (TDEs) in active galactic nuclei (AGNs) mark a regime where traditional vacuum models fail to capture the full dynamics, especially due to interaction between stellar debris and pre-existing accretion disks. We perform meshless hydrodynamic simulations incorporating both general relativistic (GR) effects and radiative cooling to study TDEs in AGNs with different orbital inclinations ($θ_{\rm inc}$) of the disrupted star, ranging from projected prograde to retrograde orbits. We post-process the simulations to derive multi-wavelength light curves and identify several distinct features in the light curves, including a precursor flare from early debris-disk collision and a major flare driven by fallback. The dynamics of the stellar debris and accretion disk, and subsequently the light curve features, are strongly affected by $θ_{\rm inc}$ and GR effects. Retrograde orbits ($θ_{\rm inc}=135^\circ$) yield a more luminous, shorter major flare and a more prominent precursor than prograde ones ($θ_{\rm inc}=22.5^\circ$). During fallback, prograde cases ($θ_{\rm inc} = 22.5^\circ$, $45^\circ$) develop a central cavity with spirals in the inner region of the AGN disk, leading to transient UV/X-ray suppression accompanied by oscillations, while higher inclinations ($θ_{\rm inc}=90^\circ$, $135^\circ$) form a gradually tilting inner disk, potentially causing UV/X-ray dips via geometric effects at certain viewing angles. Relativistic apsidal precession alters stream collisions, producing structural differences in the inner disk, outer disk, and debris compared to Newtonian cases, and drives quasi-periodic signals in prograde configurations. These results provide predictive diagnostics for identifying AGN TDEs and interpreting observed light-curve diversity.

astro-ph.HE

Probing the Strong Gravity Region of Black Holes with eXTP

We present the novel capabilities of the enhanced X-ray Timing and Polarimetry (eXTP) mission to study the strong gravity region around stellar-mass black holes in X-ray binary systems and supermassive black holes in active galactic nuclei. eXTP can combine X-ray spectral, timing, and polarimetric techniques to study the accretion process near black holes, measure black hole masses and spins, and test Einstein's theory of General Relativity in the strong field regime. We show how eXTP can improve the current measurements of black holes of existing X-ray missions and we discuss the scientific questions that can be addressed.

astro-ph.HE

Dense Matter in Neutron Stars with eXTP

In this White Paper, we present the potential of the enhanced X-ray Timing and Polarimetry (eXTP) mission to constrain the equation of state of dense matter in neutron stars, exploring regimes not directly accessible to terrestrial experiments. By observing a diverse population of neutron stars - including isolated objects, X-ray bursters, and accreting systems - eXTP's unique combination of timing, spectroscopy, and polarimetry enables high-precision measurements of compactness, spin, surface temperature, polarimetric signals, and timing irregularity. These multifaceted observations, combined with advances in theoretical modeling, pave the way toward a comprehensive description of the properties and phases of dense matter from the crust to the core of neutron stars. Under development by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Sciences, the eXTP mission is planned to be launched in early 2030.

astro-ph.HE

Meta-aware Learning in text-to-SQL Large Language Model

The advancements of Large language models (LLMs) have provided great opportunities to text-to-SQL tasks to overcome the main challenges to understand complex domain information and complex database structures in business applications. In this paper, we propose a meta-aware learning framework to integrate domain knowledge, database schema, chain-of-thought reasoning processes, and metadata relationships to improve the SQL generation quality. The proposed framework includes four learning strategies: schema-based learning, Chain-of-Thought (CoT) learning, knowledge-enhanced learning, and key information tokenization. This approach provides a comprehensive understanding of database structure and metadata information towards LLM through fine-tuning to improve its performance on SQL generation within business domains. Through two experimental studies, we have demonstrated the superiority of the proposed methods in execution accuracy, multi-task SQL generation capability, and reduction of catastrophic forgetting.

cs.AI

Proper Motion and Natal Kick in the Galactic Black Hole X-ray Binary AT2019wey

Understanding the formation mechanisms of stellar-mass black holes in X-ray binaries (BHXBs) remains a fundamental challenge in astrophysics. The natal kick velocities imparted during black hole formation provide crucial constraints on these formation channels. In this work, we present a new-epoch very long baseline interferometry (VLBI) observation of the Galactic BHXB AT2019wey carried out in 2023. Combining with archival VLBI data from 2020, we successfully measure the proper motion of AT2019wey over a 3-year timescale, namely $0.78\pm0.12$~\masyr\ in right ascension and $-0.42\pm0.07$~\masyr\ in declination. Employing the measured proper motion, we estimate its peculiar velocity and the potential kick velocity (PKV), through Monte Carlo simulations incorporating uncertainties of its distance and radial velocity. The estimated PKV distributions and height above the Galactic plane suggest that AT2019wey's black hole likely formed through a supernova explosion rather than direct collapse.

astro-ph.HE

AT2021aeuk: A Repeating Partial Tidal Disruption Event Candidate in a Narrow-line Seyfert 1 galaxy

A black hole (BH) can tear apart a star that ventures within its tidal radius, producing a luminous flare as the stellar debris falls back, known as a tidal disruption event (TDE). While TDEs in quiescent galaxies are relatively well understood, identifying TDEs in active galactic nuclei (AGN) still remains a significant challenge. We present the discovery of AT2021aeuk, a transient exhibiting dual flares within around three years in a narrow-line Seyfert 1 galaxy. Multi-wavelength observations triggered during the second flare in 2023 revealed an extraordinary X-ray V-shaped light curve, strongly anti-correlated with the optical light curve and accompanied by a lag of $\sim$40 days. This behavior is inconsistent with both supernova and pure AGN origins. In addition, a new broad component emerges in the Balmer lines during the second flare, showing a clear reverberation signal to the continuum variation. We propose that the dual-flare may be linked to a repeating partial TDE (rpTDE), where the second flare results from a collision between the TDE stream and the inner accretion disk, triggering an optical flare while simultaneously partially destroying the X-ray corona. However, other mechanisms, such as a stellar-mass BH (sBH) merger within an accretion disk, could produce similar phenomena, which we cannot entirely rule out. The Vera C. Rubin Observatory will be a powerful tool for further investigating the nature of such events in the future.

astro-ph.HE

LEIA discovery of the longest-lasting and most energetic stellar X-ray flare ever detected

The Lobster Eye Imager for Astronomy (LEIA) detected a new X-ray transient on 2022 November 7, identified as a superflare event occurring on a nearby K-type giant star HD 251108. The flux increase was also detected in follow-up observations at X-ray, UV and optical wavelengths. The flare lasted for about 40 days in soft X-ray observations, reaching a peak luminosity of ~1.1 * 10^34 erg/s in 0.5-4.0 keV, which is roughly 60 times the quiescent luminosity. Optical brightening was observed for only one night. The X-ray light curve is well described by a double fast rise and exponential decay model, attributed to the cooling process of a loop arcade structure formed subsequent to the initial large loop with a half-length of ~1.9 * 10^12 cm. Time-resolved X-ray spectra were fitted by a four-temperature apec model (with three components being the quiescent background), showing significant evolution of plasma temperature and emission measure over time. The estimated energy released in the LEIA band is ~3 * 10^39 erg, suggesting that this is likely the most energetic X-ray stellar flare with the longest duration detected to date.

astro-ph.HE

Correlated spectro-polarimetric study along the Z track in XTE J1701-462 puts constraints on its coronal geometry

Context. In September 2022, the transient neutron star low-mass X-ray binary XTE J1701-462 went into a new outburst. Aims. The objective of this work is to examine the evolution of the accretion geometry of XTE J1701-462 by studying the spectro-polarimetric properties along the Z track of this source. The simultaneous observations archived by the Insight-Hard X-ray Modulation Telescope (HXMT) and the Imaging X-ray Polarimetry Explorer (IXPE) give us the opportunity. Methods. We present a comprehensive X-ray spectro-polarimetric analysis of XTE J1701-462, using simultaneous observations from IXPE, Insight-HXMT and NuSTAR. For IXPE observations, two methods are employed to measure the polarization: a model-independent measurement with PCUBE and a model-dependent polarization-spectral analysis with XSPEC. The corresponding spectra from Insight-HXMT and NuSTAR are studied with two configurations that correspond to a slab-like corona and a spherical shell-like corona, respectively. Results. Significant polarization characteristics are detected in XTE J1701-462. The polarization degree shows a decreasing trend along the Z track, reducing from (4.84 $\pm$ 0.37)% to (3.76 $\pm$ 0.43)% on the horizontal branch and jumping to less than 1% on the normal branch. The simultaneous spectral analysis from Insight-HXMT and NuSTAR suggests that the evolution of the PD is closely linked to changes in the flux of the Comptonized component and its covering factor along the Z track, supporting a shrinking corona.

astro-ph.HE

Science objectives of the Einstein Probe mission

The Einstein Probe (EP) is an interdisciplinary mission of time-domain and X-ray astronomy. Equipped with a wide-field lobster-eye X-ray focusing imager, EP will discover cosmic X-ray transients and monitor the X-ray variability of known sources in 0.5-4 keV, at a combination of detecting sensitivity and cadence that is not accessible to the previous and current wide-field monitoring missions. EP can perform quick characterisation of transients or outbursts with a Wolter-I X-ray telescope onboard. In this paper, the science objectives of the Einstein Probe mission are presented. EP is expected to enlarge the sample of previously known or predicted but rare types of transients with a wide range of timescales. Among them, fast extragalactic transients will be surveyed systematically in soft X-rays, which include γ-ray bursts and their variants, supernova shock breakouts, and the predicted X-ray transients associated with binary neutron star mergers. EP will detect X-ray tidal disruption events and outbursts from active galactic nuclei, possibly at an early phase of the flares for some. EP will monitor the variability and outbursts of X-rays from white dwarfs, neutron stars and black holes in our and neighbouring galaxies at flux levels fainter than those detectable by the current instruments, and is expected to discover new objects. A large sample of stellar X-ray flares will also be detected and characterised. In the era of multi-messenger astronomy, EP has the potential of detecting the possible X-ray counterparts of gravitational wave events, neutrino sources, and ultra-high energy γ-ray and cosmic ray sources. EP is expected to help advance the studies of extreme objects/phenomena and their underlying physical processes revealed in the dynamic X-ray universe, as well as studies in other areas of X-ray astronomy.

astro-ph.HE

Detection of an Orphan X-ray Flare from a Blazar Candidate EP240709a with Einstein Probe

Blazars are often observed to flare across multiple wavelengths. Orphan flares from blazars have been only detected a few times, providing an opportunity to understand the structure of the jet in the accreting system. We report a remarkable orphan X-ray flare from a blazar candidate EP240709a, detected by Einstein Probe (EP) in July 2024. The multi-band spectral properties and variability support EP240709a as a high-energy peaked BL Lacertae-type object. The flux in 0.5-10 keV increases by at least 28 times to the value of low state in 2020, with non-detection of remarkable flaring in other bands during the same period. EP240709a exhibits the harder-when-brighter tendency in the X-ray band during the orphan flare, while its infrared-optical spectra are featureless. We employ one-zone and two-zone leptonic synchrotron self-Compton models to perform the spectral energy distribution fitting. Detecting this rare orphan flare shows the potential of EP in discovering peculiar activities from AGN in high-cadence X-ray sky surveys.

astro-ph.HE

Investigating the consistency of the shape and flux of X-ray reflection spectra in the hard state with an accretion disk reaching close to the black hole

The observed spectra from black hole (BH) X-ray binaries (XRBs) typically consist of two primary components: multitemperature blackbody (BB) originating from the accretion disk in soft X-ray, and a power-law like component in hard X-ray due to Comptonization of soft photons by the hot corona. Illumination of the disk by the corona gives rise to another key component known as reflection. A fraction of the incident hard X-ray radiation is naturally absorbed and re-emitted as a BB at lower energies, referred to as reprocessed BB. For densities relevant to XRBs and typical ionization values, the reprocessed BB may become significant in the soft X-ray region and should be noticeable in the observed spectra as a consequence of reflection. The absence of any BB component in the low/hard state of BH XRB may not be consistent with reflection of high irradiating flux observed as power-law from appropriately dense disk of XRB. We focus on the low/hard state of the BH XRB MAXI J1820+070. We simultaneously fit the shape and flux of the reflection spectra, allowing us to estimate the correct density and ionization of the slab and, correspondingly, the reprocessed BB. Our fitting suggests that the disk in principle may extend close to the BH and still the reprocessed BB due to disk illumination remains small enough to be consistent with the data as opposed to earlier study. The inner reflection component is highly ionized and its fit is primarily driven by its contribution to the continuum. The reprocessed BB cannot resolve whether the disk is extended close to the BH or not in the hard state. For this specific observation, the flux in inner reflection component turns out to be quite low with respect to outer reflection or power-law. Outflowing slab corona covering the inner region of the disk could be the possible geometry of the source with the underlying disk reaching close to the BH. (shortened)

astro-ph.HE