arXiv subjects

Xiliang Zhang

Publications and source records attributed to Xiliang Zhang.

12 recordsLinked to original sources

arXiv2026

Post-perihelion Coma Composition of the Interstellar Comet 3I/ATLAS from Optical Spectroscopy

We present multi-epoch optical spectroscopy of the interstellar comet 3I/ATLAS obtained between December 2025 and January 2026 (heliocentric distances 1.8-3.3 au), yielding post-perihelion production rates and mixing ratios for CN, C$_3$, C$_2$, CH, and gaseous metals (Fe I and Ni I). Our results show that the coma is less depleted in C$_2$ after perihelion than before, indicative of subsurface activation or compositional heterogeneity. The outgassing profiles reveal a pronounced perihelion asymmetry: CN and metal production rates decline more gradually outbound than inbound, consistent with the reported behavior of H$_2$O and implying a change in the comet's activity pattern across perihelion. Despite being metal-rich relative to its H$_2$O content, 3I follows the metal-CO correlation observed in comets of diverse origins, suggesting that gaseous metal release is more closely linked to a CO-bearing volatile reservoir than to H$_2$O, potentially in the form of metal carbonyls. In addition, the [O I] $\lambda6300$ emission shows a significant residual after subtracting the expected contributions from H$_2$O, CO$_2$, and CO, which may reflect systematic uncertainties in the photodissociation yields of those molecules or a contribution from additional oxygen-bearing parents.

astro-ph.EP↗

arXiv2026

Tianwen-2 target asteroid (469219) Kamo'oalewa probably develops an Itokawa-compositional but ultra-highly space-weathered surface

China's Tianwen-2 mission plans to return samples from a small, rapidly spinning Earth quasi-satellite (469219) Kamo'oalewa. Previous studies linked Kamo'oalewa to lunar composition and origin. Here, we propose another scenario. We reanalyzed the reflectance spectrum of Kamo'oalewa and obtained an absorption band center at 1.001+-0.028 um (error is 1sigma), consistent with LL chondrites. We then conducted space weathering (SW) experiments on meteorites and found that highly space-weathered LL chondrite powder (but not slab) successfully reproduced the reflectance spectrum of Kamo'oalewa. We further traced the dynamical origin of Kamo'oalewa and found that it probably originated from the v6 secular resonance, and more specifically, the Flora family. Kamo'oalewa exhibits a similar composition to Itokawa and 7 objects in the Flora family, but with a higher degree of space weathering. We, therefore, proposed that Kamo'oalewa probably originated from the Flora family and developed an Itokawa-compositional, highly space-weathered, fine-regolith-dominated surface.

astro-ph.EP↗

arXiv2024

A Cascade Dual-Decoder Model for Joint Entity and Relation Extraction

In knowledge graph construction, a challenging issue is how to extract complex (e.g., overlapping) entities and relationships from a small amount of unstructured historical data. The traditional pipeline methods are to divide the extraction into two separate subtasks, which misses the potential interaction between the two subtasks and may lead to error propagation. In this work, we propose an effective cascade dual-decoder method to extract overlapping relational triples, which includes a text-specific relation decoder and a relation-corresponded entity decoder. Our approach is straightforward and it includes a text-specific relation decoder and a relation-corresponded entity decoder. The text-specific relation decoder detects relations from a sentence at the text level. That is, it does this according to the semantic information of the whole sentence. For each extracted relation, which is with trainable embedding, the relation-corresponded entity decoder detects the corresponding head and tail entities using a span-based tagging scheme. In this way, the overlapping triple problem can be tackled naturally. We conducted experiments on a real-world open-pit mine dataset and two public datasets to verify the method's generalizability. The experimental results demonstrate the effectiveness and competitiveness of our proposed method and achieve better F1 scores under strict evaluation metrics. Our implementation is available at https://github.com/prastunlp/DualDec.

cs.CL↗

arXiv2024

Photonic Spin-Orbit Coupling Induced by Deep-Subwavelength Structured Light

We demonstrate both theoretically and experimentally beam-dependent photonic spin-orbit coupling in a two-wave mixing process described by an equivalent of the Pauli equation in quantum mechanics. The considered structured light in the system is comprising a superposition of two orthogonal spin-orbit-coupled states defined as spin up and spin down equivalents. The spin-orbit coupling is manifested by prominent pseudo spin precession as well as spin-transport-induced orbital angular momentum generation in a photonic crystal film of wavelength thickness. The coupling effect is significantly enhanced by using a deep-subwavelength carrier envelope, different from previous studies which depend on materials. The beam-dependent coupling effect can find intriguing applications; for instance, it is used in precisely measuring variation of light with spatial resolution up to 15 nm.

physics.optics↗

arXiv2020

A Novel Hybrid Algorithm for Lucky Imaging

Lucky imaging is a high-resolution astronomical image recovery technique with two classic implementation algorithms, i.e. image selecting, shifting and adding in image space and data selecting and image synthesizing in Fourier space. This paper proposes a novel lucky imaging algorithm where with space-domain and frequency-domain selection rates as a link, the two classic algorithms are combined successfully, making each algorithm a proper subset of the novel hybrid algorithm. Experimental results show that with the same experiment dataset and platform, the high-resolution image obtained by the proposed algorithm is superior to that obtained by the two classic algorithms. This paper also proposes a new lucky image selection and storage scheme, which can greatly save computer memory and enable lucky imaging algorithm to be implemented in a common desktop or laptop with small memory and to process astronomical images with more frames and larger size. Besides, through simulation analysis, this paper discusses the binary star detection limits of the novel lucky imaging algorithm and traditional ones under different atmospheric conditions.

astro-ph.IM↗

arXiv2020

An authenticated and secure accounting system for international emissions trading

Expanding multi-country emissions trading system is considered as crucial to fill the existing mitigation gap for the 2\degree C climate target. Trustworthy emissions accounting is the cornerstone of such a system encompassing different jurisdictions. However, traditional emissions measuring, reporting, and verification practices that support data authenticity might not be applicable as detailed data from large utilities and production facilities to be covered in the multi-country emissions trading system are usually highly sensitive and of severe national security concern. In this study, we propose a cryptographic framework for an authenticated and secure emissions accounting system that can resolve this data dilemma. We demonstrate that integrating a sequence of cryptographic protocols can preserve data authenticity and security for a stylized multi-country emissions trading system. We call for more research to promote applications of modern cryptography in future international climate governance to build trust and strengthen collaboration.

econ.GN↗

arXiv2019

Semidiscrete quantum droplets and vortices

We consider a binary bosonic condensate with weak mean-field (MF) residual repulsion, loaded in an array of nearly one-dimensional traps coupled by transverse hopping. With the MF force balanced by the effectively one-dimensional attraction, induced in each trap by the Lee-Hung-Yang correction (produced by quantum fluctuations around the MF state), stable onsite-centered and intersite-centered semi-discrete quantum droplets (QDs) emerge in the array, as fundamental ones and self-trapped vortices, with winding numbers, at least, up to 5, in both tightly-bound and quasi-continuum forms. The application of a relatively strong trapping potential leads to squeezing transitions, which increase the number of sites in fundamental QDs, and eventually replace vortex modes by fundamental or dipole ones. The results provide the first realization of stable semi-discrete vortex QDs, including ones with multiple vorticity.

nlin.PS↗

arXiv2019

Two-dimensional composite solitons in Bose-Einstein condensates with spatially confined spin-orbit coupling

It was recently found that the spin-orbit (SO) coupling can help to create stable matter-wave solitons in spinor Bose-Einstein condensates in the two-dimensional (2D) free space. Being induced by external laser illumination, the effective SO coupling can be applied too in a spatially confined area. Using numerical methods and the variational approximation (VA), we build families of 2D solitons of the semi-vortex (SV) and mixed-mode (MM) types, and explore their stability, assuming that the SO-coupling strength is confined in the radial direction as a Gaussian. The most essential result is identification, by means of the VA and numerical methods, of the minimum size of the spatial confinement for which the 2D system maintains stable solitons of the SV and MM types.

nlin.PS↗

arXiv2018

Optical Observations of the Young Type Ic Supernova SN 2014L in M99

We present optical spectroscopic and photometric observations of the nearby type Ic supernova (SN Ic) SN 2014L. This SN was discovered by the Tsinghua-NAOC Transient Survey (TNTS) in the nearby type-Sc spiral galaxy M99 (NGC 4254). Fitting to the early-time light curve indicates that SN 2014L was detected at only a few hours after the shock breakout, and it reached a peak brightness of $M_{\rm V} = -17.73 \pm 0.28$ mag ($L= [2.06\pm 0.50] \times 10^{42}$ erg s$^{-1}$) approximately 13 days later. SN 2014L shows a close resemblance to SN 2007gr in the photometric evolution, while it shows stronger absorption features of intermediate-mass elements (especially \CaII) in the early-time spectra. Based on simple modeling of the observed light curves, we derived the mass of synthesized $^{56}$Ni as $M_{\rm Ni} = 0.075 \pm 0.025 M_{\odot}$, and the mass and total energy of the ejecta as $M_{\rm ej} = 1.00 \pm 0.20 M_\odot$ and $E_{\rm ej}=1.45\pm0.25$ foe, respectively. Given these typical explosion parameters, the early detection, and the extensive observations, we suggest that SN 2014L could be a template sample for the investigation of SNe Ic.

astro-ph.HE↗

arXiv2017

The physical constraints on a new LoBAL QSO at z=4.82

Very few low-ionization broad absorption line (LoBAL) QSOs have been found at high redshifts to date. One high-redshift LoBAL QSO, J0122+1216, was recently discovered at the Lijiang 2.4-m Telescope with an initial redshift determination of 4.76. Aiming to investigate its physical properties, we carried out follow-up observations in the optical and near-IR spectroscopy. Near-IR spectra from UKIRT and P200 confirms that it is a LoBAL, with a new redshift determination of $4.82\pm0.01$ based on the \mgii~ emission-line. The new \mgii~ redshift determination reveals strong blueshifts and asymmetry of the high-ionization emission lines. We estimated a black hole mass of $\sim 2.3\times 10^9 M_\odot$ and Eddington ratio of $\sim 1.0$ according to the empirical \mgii-based single-epoch relation and bolometric correction factor. It is possible that strong outflows are the result of an extreme quasar environment driven by the high Eddington ratio. A lower limit on the outflowing kinetic power ($>0.9\% L_{Edd}$) was derived from both emission and absorption lines, indicating these outflows play a significant role in the feedback process to regulate the growth of its black hole as well as host galaxy evolution.

astro-ph.GA↗

arXiv2016

A Luminous Peculiar Type Ia Supernova SN 2011hr: More Like SN 1991T or SN 2007if?

Photometric and spectroscopic observations of a slowly declining, luminous Type Ia supernova (SN Ia) SN 2011hr in the starburst galaxy NGC 2691 are presented. SN 2011hr is found to peak at $M_{B}=-19.84 \pm 0.40\,\rm{mag}$, with a post-maximum decline rate $Δ$m$_{15}$(B) = 0.92 $\pm$ 0.03\,$\rm{mag}$. From the maximum-light bolometric luminosity, $L=(2.30 \pm 0.90) \times 10^{43}\,\rm{erg\,s^{-1}}$, we estimate the mass of synthesized \Nifs\ in SN 2011hr to be $M(\rm{^{56}Ni})=1.11 \pm 0.43\,M_{\sun}$. SN 2011hr appears more luminous than SN 1991T at around maximum light, and the absorption features from its intermediate-mass elements (IMEs) are noticeably weaker than the latter at similar phases. Spectral modeling suggests that SN 2011hr has the IMEs of $\sim$\,0.07 M$_{\sun}$ in the outer ejecta, which is much lower than the typical value of normal SNe Ia (i.e., 0.3 -- 0.4 M$_{\sun}$) and is also lower than the value of SN 1991T (i.e., $\sim$\,0.18 M$_{\sun}$). These results indicate that SN 2011hr may arise from a Chandrasekhar-mass white dwarf progenitor that experienced a more efficient burning process in the explosion. Nevertheless, it is still possible that SN 2011hr may serve as a transitional object connecting the SN 1991T-like SNe Ia with the superluminous subclass like SN 2007if given that the latter also shows very weak IMEs at all phases.

astro-ph.SR↗

arXiv2014

Optical and Ultraviolet Observations of A Low-Velocity Type II-Plateau Supernova 2013am in M65

Optical and ultraviolet observations for the nearby type II-plateau supernova (SN IIP) 2013am in the nearby spiral galaxy M65 are presented in this paper. The early spectra are characterized by relatively narrow P-Cygni features, with ejecta velocities much lower than observed in normal SNe IIP (i.e., $\sim$2000 km s$^{-1}$ vs. $\sim$5000 km $^{-1}$ in the middle of the plateau phase). Moreover, prominent Ca II absorptions are also detected in SN 2013am at relatively early phases. These spectral features are reminiscent of those seen in the low-velocity and low-luminosity SN IIP 2005cs. However, SN 2013am exhibits different photometric properties, having shorter plateau phases and brighter light-curve tails if compared to SN 2005cs. Adopting $R_{V}$=3.1 and a mean value of total reddening derived from the photometric and spectroscopic methods(i.e., $E(B-V)=0.55\pm$0.19 mag), we find that SN 2013am may have reached an absolute $V$-band peak magnitude of $-15.83\pm0.71$ mag, and produced a $^{56}$Ni mass of $0.016^{+0.010}_{-0.006} solar masses in the explosion. These parameters are close to those derived for SN 2008in and SN 2009N which have been regarded as "gap-filler" objects linking the faint SNe IIP to the normal ones. This indicates that some low-velocity SNe IIP may not necessarily result from the low-energetic explosions, and the low expansion velocities could be due to a lower metallicity of the progenitor stars, a larger envelope mass ejected in the explosion, or that is was observed at an angle that is away from the polar direction.

astro-ph.SR↗