National Astronomical Observatories

Joint Modeling of GD-1 and C-19 as Old Streams

Abstract DESI observational data for the GD-1 and C-19 streams are compared to stream simulations in an evolving multihalo potential of a Milky Way–like galaxy based on a cosmological Milky Way–like simulation. The number of subhalos decreases with time, and the subhalo-stream en...

Improved YOLOv11 Framework with Channel Attention for High-Precision Identification of Luffa Leaf Diseases

Early accurate identification of luffa crop diseases is essential for timely treatment and high-quality agricultural production. Currently, luffa disease diagnosis relies solely on manual field inspection, which is labor-intensive and error-prone, and lacks assessment uniformity....

Gas absorption of soft X-rays strongly impacts the redshift distribution of dark Fast X-ray Transients

Abstract The progenitors of many Fast X-ray Transients (FXTs) and those of γ-ray bursts (GRBs) are strongly linked. Given that ”dark” GRBs are typically found to be events suffering from enhanced extinction in the host galaxy, we investigate the nature of ”dark” FXTs. However, un...

Mapping the nuclear environments of extreme coronal line emitting galaxies

Abstract Extreme coronal line emitters (ECLEs) are a rare class of galactic nuclei exhibiting unusually strong high-ionisation forbidden emission lines, and several ECLEs have been linked to tidal disruption events (TDEs). In this work, we compile and analyse optical spectra of 3...

A Comparative Study of Machine-Learning Methods for Early Classification from Sparse Astronomical Light Curves

The booming data volume of modern time-domain surveys demands fast, robust early classification of sparsely sampled light curves, as newly discovered transients typically have only a handful of observations. We compare classifiers for extremely sparse light curves (3–30 observati...

Astronomical spectra as language: Order-agnostic foundation model for low-SNR reconstruction and stellar parameter prediction

Large-scale spectroscopic surveys contain numerous low-SNR stellar spectra that are difficult to analyze with traditional pipelines but remain valuable for Galactic archaeology, chemical-evolution studies, and population-level stellar characterization. We propose an order-agnosti...

Earliest simultaneous multi-color optical observations of GRB 230328B: from 41 seconds to the host-galaxy identification

Abstract We present a multiwavelength study of the long-duration gamma-ray burst GRB 230328B, combining prompt γ-ray observations with exceptionally early simultaneous optical photometry and extensive X-ray, radio, and host-galaxy follow-up. NUTTELA-TAO began simultaneous g′r′i′...

GRB 260310A / SN 2026fgk: A Multi-Wavelength Study of a Nearby Underluminous Long GRB and SN with a Complex Afterglow

Abstract We present a comprehensive multi-wavelength study of GRB 260310A / SN 2026fgk, a nearby (z = 0.153), long-duration gamma-ray burst (GRB) with an exceptionally underluminous prompt γ-ray emission and a Comptonized spectrum. The burst occurred at the edge of a blue host ga...

Effects of rainfall on permafrost degradation in alpine desert regions of the Tibetan Plateau

Rainfall is increasing across the Tibetan Plateau, yet its effects on permafrost in alpine desert regions remain poorly understood. Using a validated one-dimensional land-surface model for a representative site, we conducted idealized experiments to isolate the effects of summer...