arXiv subjects

Hong-bo Cai

Publications and source records attributed to Hong-bo Cai.

7 recordsLinked to original sources

arXiv2026

SVOM Science User Support Services at Chinese Science Center

The Chinese-French SVOM (Space-based Multi-band Astronomical Variable Objects Monitor) mission is dedicated to the study of gamma-ray bursts (GRBs) from the distant universe. A key component of the SVOM Chinese Ground Segment, the Science User Support Services (SUSS) provides comprehensive support for the mission's scientific operations. SUSS consists of two integral pillars: a suite of specialized software tools that automate key workflows, and a dedicated User Support Team that delivers expert-led, human services. These human-delivered services include operational coordination across telescope networks, direct technical assistance to astronomers, user training, and proactive problem-solving throughout the observation lifecycle. This paper focuses on the organization of SVOM scientific operations and the role of SUSS in facilitating these tasks. We provide a detailed description of the SUSS software architecture and its functionalities, encompassing the General Platform, the Burst Advocate (BA) support tools for GRB counterpart identification, the Target of Opportunity (ToO) support tools, and the General Program (GP) support tools. The structure and services provided by the user support team at the Chinese Science Center (CSC) are also elaborated. Furthermore, we evaluate the performance of SUSS during its first operational year, assessing its effectiveness in fulfilling user requirements. The evaluation offers valuable insights to guide future user support strategies and software enhancements, ultimately enabling better service for the SVOM scientific community.

astro-ph.IM↗

arXiv2026

Alert Chain and Observation Planning for Ground Wide Angle Camera Network

The Ground Wide Angle Camera Network (GWAC-N) is a robotic telescope network. It consists of ten wide-field core telescopes (GWAC-A) and two 60cm narrow-field rapid follow-up telescopes (GWAC-F60A/B). The primary scientific goal of GWAC-N is to detect optical counterparts of gamma-ray bursts (GRBs) discovered by the SVOM satellite. This is achieved through synchronized monitoring with the GWAC-A array. Upon receiving a GRB trigger alert, the network conducts rapid, multi-band follow-up observations using the GWAC-F60A/B telescopes. The two-stage observation process involves many telescopes, making manual control impractical. Automated operations are therefore essential. They are realized through an integrated alert processing chain and an automated observation scheduling and dispatching mechanism. To enable this, we employ the SVOM Follow-up Observation Coordinating Service (FOCS) and GWAC-N's Automatic Observation Management (AOM) system. This paper presents the integrated alert processing workflow. It also describes the formulation of observation strategies, and the scheduling and execution of observations enabled by FOCS and AOM.

astro-ph.IM↗

arXiv2026

SVOM/VT: On-ground processing of VT-VHF data

The VT--VHF data comprise three types of onboard-processed data results generated from four sequential observational sequences and transmitted to the ground via a Very High Frequency (VHF) downlink. On the ground, these data are processed by three successive pipelines: the pre-processing pipeline, the VT--VHF data processing pipeline (VVPP), and the VT afterglow candidate pipeline (VTAC). These pipelines perform packet decoding, astrometric and photometric calibration, and afterglow candidate identification, respectively. This paper describes the architecture and operational implementation of the VT--VHF ground processing system and assesses its end-to-end performance using the first year of SVOM operations. These data enable rapid identification of GRB optical counterparts. Early detections, while the source is still optically bright, facilitate spectroscopic redshift measurements. Dual-band colors provide preliminary redshift constraints and help identify high-redshift candidates, whereas non-detections in both bands may indicate very high redshift, significant extinction, or intrinsically dark bursts. In-orbit operations show that the VT--VHF ground processing system successfully identifies optical afterglow candidates for a significant fraction of ECLAIRs triggers with available VT--VHF data, demonstrating its robustness and readiness.

astro-ph.IM↗

arXiv2025

SVOM Follow-up Observation Coordinating Service

The Sino-French SVOM (Space Variable Objects Monitor) mission is a space-based astronomy mission complemented with ground-based dedicated instrumentation. It aims to explore and study high-energy cosmic phenomena, such as gamma-ray bursts (GRBs). This unprecedented combination of space-based and ground-based instruments will provide leading multi-wavelength observational capabilities in gamma-rays, X-rays, optical, and near-infrared bands. The complete observation sequence of each GRB triggered by the SVOM mission consists of three stages, the GRB detections, followed by the on-board and grounded automatic follow-ups, and rapid deep multi-band photometry and spectroscopy re-visit observations. To efficiently organize all grounded instruments performing automatic follow-ups and re-visit observations, we develop a follow-up observation coordinating service (FOCS), which is capable of performing GRB trigger distributing, automatic observation scheduling and observation coordination supporting by providing a user support platform. The FOCS also facilitates the provision of observational planning for ground-based telescopes to conduct synchronized observations of identical celestial regions as SVOM. The FOCS is utilized for the SVOM-dedicated ground-based telescopes as well as for associated partner telescopes. Since the launch of SVOM in June 2024, as the FOCS system joining the operations of SVOM, multiple successful observations have been made for SVOM GRBs. In this paper, we present the goals of the FOCS system as well as the principle and workflow developed to achieve these goals. The structure, technical design, implementation, and performance of the FOCS system are also described in detail. We conclude with a summary of the current status of the FOCS system and our near-future development plan.

astro-ph.IM↗

arXiv2025

GRB 240825A: Early Reverse Shock and Its Physical Implications

Early multiwavelength observations offer crucial insights into the nature of the relativistic jets responsible for gamma-ray bursts and their interaction with the surrounding medium.We present data of GRB 240825A from 17 space- and ground-based telescopes/instruments, covering wavelengths from NIR/optical to X-ray and GeV, and spanning from the prompt emission to the afterglow phase triggered by Swift and Fermi. The early afterglow observations were carried out by SVOM/C-GFT, and spectroscopic observations of the afterglow by GTC, VLT, and TNG determined the redshift of the burst ($z = 0.659$) later.A comprehensive analysis of the prompt emission spectrum observed by Swift-BAT and Fermi-GBM/LAT reveals a rare and significant high-energy cutoff at ~76 MeV. Assuming this cutoff is due to $γγ$ absorption allows us to place an upper limit on the initial Lorentz factor, $Γ_0 < 245$. The optical/NIR and GeV afterglow light curves be described by the standard external shock model, with early-time emission dominated by a reverse shock (RS) and a subsequent transition to forward shock (FS) emission. Our afterglow modelling yields a consistent estimate of the initial Lorentz factor ($Γ_{\rm 0} \sim 234$). Furthermore, the RS-to-FS magnetic field ratio ($\mathcal{R}_B \sim 302$) indicates that the reverse shock region is significantly more magnetized than the FS region. An isotropic-equivalent kinetic energy of $E_{\text{k,iso}} = 5.25 \times 10^{54}$ erg is derived, and the corresponding $γ$-ray radiation efficiency is estimated to be $η_γ$ = 3.1%. On the other hand, the standard afterglow model can not reproduce the X-ray light curve of GRB 240825A, calling for improved models to characterize all multiwavelength data.

astro-ph.HE↗

arXiv2024

An Image Simulator of Lunar Far-Side Impact Flashes Captured from the Earth-Moon L2 Point

Impact flashes on the moon are caused by high-speed collisions of celestial bodies with the lunar surface. The study of the impacts is critical for exploring the evolutionary history and formation of the Moon, and for quantifying the risk posed by the impacts to future human activity. Although the impacts have been monitored from the Earth by a few projects in past 20 years, the events occurring on the lunar far side have not been explored systematically so far. We here present an end-to-end image simulator dedicated to detecting and monitoring the impacts from space, which is useful for future mission design. The simulator is designed for modularity and developed in the Python environment, which is mainly composed of four components: the flash temporal radiation, the background emission, the telescope and the detector used to collect and measure the radiation. Briefly speaking, with a set of input parameters, the simulator calculates the flash radiation in the context of the spherical droplet model and the background emission from the lunar surface. The resulting images are then generated by the simulator after considering a series observational effects, including the stray light, transmission of the instrument, point spread function and multiple kinds of noise caused by a CCD/CMOS detector. The simulator is validated by comparing the calculation with the observations taken on the ground. The modular design enables the simulator to be improved and enhanced by including more complex physical models in the future, and to be flexible for other future space missions.

astro-ph.IM↗

arXiv2013

A new ignition scheme using hybrid indirect-direct drive for inertial confinement fusion

A new hybrid indirect-direct-drive ignition scheme is proposed for inertial confinement fusion: a cryogenic capsule encased in a hohlraum is first compressed symmetrically by indirect-drive x-rays, and then accelerated and ignited by both direct-drive lasers and x-rays. A steady high-density plateau newly formed between the radiation and electron ablation fronts suppresses the rarefaction at the radiation ablation front and greatly enhances the drive pressure. Meanwhile, multiple shock reflections at the fuel/hot-spot interface are prevented during capsule deceleration. Thus rapid ignition and burn are realized. In comparison with the conventional indirect drive, the hybrid drive implodes the capsule with a higher velocity ($\sim4.3\times10^7$ cm/s) and a much lower convergence ratio ($\sim$25), and the growth of hydrodynamic instabilities is significantly reduced, especially at the fuel/hot-spot interface.

physics.plasm-ph↗