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.

Massive stars die as core-collapse supernovae, whose optical light emerges days after the implosion. Theory predicts that the initial collapse-driven shock, upon breaking through the star and dense circumstellar medium, emits a brief thermal flash of soft X-rays and ultraviolet. Yet these elusive first signals have remained largely undetected, owing to limited wide-field soft X-ray monitoring. Here we report the discovery of a soft X-ray flash, EP260321a, followed days later by a broad-lined supernova from an envelope-stripped progenitor. Its X-ray spectrum, best modeled with blackbody, establishes it as the long-sought archetypal shock breakout. The burst's duration and energetics place the breakout at a radius of 300 solar radii, tracing a dense surrounding shell and revealing abrupt mass ejection within the final month before collapse.

The Chinese Ground Follow-up Telescope (C-GFT) is an optical facility upgraded to support the Space Variable Objects Monitor mission (SVOM). Located at the Jilin Observation Station, it is capable of rapidly identifying and monitoring the optical counterparts of Gamma-Ray Bursts (GRBs). The 1.2-m telescope is equipped with two switchable focal-plane instruments: the prime-focus wide-field LATIOS camera and the Cassegrain-focus three-channel CATCH camera. In this paper, we present a system overview, including the observatory, the telescope, the instrumentation, the automated operational framework managed by the Operations Center, and the data processing pipelines. We also report the performance results obtained during over one year of SVOM's post-launch operations. The results demonstrate that the system meets its design specifications and delivers robust observational and operational performance.

Context. Detecting faint and cross-shaped sources in long-exposure images from lobster-eye X-ray telescopes is particularly challenging due to the low signal-to-noise ratio (S/N), complex noise, and unique point spread function (PSF) of these instruments. Conventional deep learning networks struggle in such conditions as they fail to effectively incorporate astrophysical priors such as photon arrival time, energy, and PSF morphology. Furthermore, the significant flux-scale differences between faint and bright sources complicate feature extraction in the standard feature pyramid network (FPN). Aims. The goal is to propose a PSF-guided multi-scale detection framework that integrates prior physical features and is specifically designed for the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP). Methods. Our approach began by constructing three-channel inputs, combining conventional grayscale images with photon energy and arrival time data. We then introduced a PSF-guided morphological convolution module (PSFConv) and a multi-kernel multi-scale FPN (MKMS-FPN) to enhance the extraction of morphological features and improve multi-scale target perception. Additionally, we integrated high-level convolutional features with prior physical statistics within a multibranch binary classifier of our detection network to boost both detection sensitivity and interpretability. Results. Using simulated long-exposure WXT data and in-orbit EP observations, our framework achieves 90% precision with recall rates of 0.85 and 0.95 for sources with flux >2 mCrab (i.e. 3.21 × 10−11 erg cm−2 s−1, unabsorbed, 0.5-4 keV) and flux >3 mCrab, respectively. At moderate precision levels, the framework further doubles the number of detectable sources with flux < 1 mCrab compared to conventional CNNs and the SExtractor pipeline. Conclusions. The integration of physical priors with deep convolutional features demonstrates a robust detection performance across diverse flux regimes. The proposed framework offers a practical reference for data processing in future lobster-eye X-ray missions, promising enhanced sensitivity for detecting faint sources in challenging astrophysical observations.

Extragalactic fast X-ray transients (eFXTs) represent a rapidly growing class of high-energy phenomena, whose physical origins remain poorly understood. With its wide-field, sensitive all-sky monitoring, the Einstein Probe (EP) has greatly increased the discovery rate of eFXTs. The search for and identification of the optical counterparts of eFXTs are vital for understanding their classification and constraining their physical origin. Yet, a considerable fraction of eFXTs still lack secure classifications due to the absence of timely follow-up observations. We carry out a systematic search of publicly available optical survey data and transient databases (including the Zwicky Transient Facility and the Transient Name Server) for optical counterparts to eFXT candidates detected by EP. In this paper, we describe our ongoing program and report the first results. Specifically, we identified the eFXT EP240506a to be associated with a UV/optical counterpart, AT 2024ofs. Spectroscopy of its host galaxy with the Very Large Telescope yields a redshift of z = 0.120 +/- 0.002. By combining archival survey data with early-time multiwavelength observations, we find that the luminosity and light-curve evolution of AT 2024ofs are consistent with a core-collapse supernova origin. From detectability simulations, we estimate a local event rate density rho 0=8.8-3.9+21.2yr-1Gpc-3 for EP240506a-like events, and completeness-corrected rate of about 36-78 yr-1 Gpc-3 for EP-detected X-ray transients associated with supernovae. Our results demonstrate the potential of EP to uncover prompt high-energy emission from core-collapse supernovae and underscore the critical importance of timely follow-up of future eFXT events.

Stars getting close enough to 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 102-105 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 1047-49ergs-1showed 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-rays dropped sharply from 3×1049ergs-1 to around 1044ergs-1within 20 days (10 days in the source rest frame). These characteristics are inconsistent with any previously known transient phenomena. We suggest that this fast-evolving event over the unprecedentedly short timescale arises likely from disruption of a WD by an IMBH. At late times, a soft component progressively dominates the X-ray spectrum, reaching a luminosity as high as 1044 erg s-1, which is consistent with being extreme super-Eddington emission from an accretion disk expected to form in an IMBH-WD TDE. 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.

The Space-based multiband astronomical Variable Objects Monitor (SVOM) detected its first short gamma-ray burst (GRB), GRB 240715A, in flight, which was jointly observed by Fermi. Based on observational data of SVOM/GRM and Fermi/GBM, we perform a comprehensive temporal and spectral analysis of individual pulses in the prompt emission of this burst, and novel characteristics are revealed. First, opposite evolutions of spectral lag are found in the first and third pulse of this burst. Second, the large negative lag of the first pulse is an outlier in the short GRB sample, especially when the pulse duration is considered. Spectral analysis shows that the negative lag of the first pulse is caused by the evolution of the spectrum index and is irrelevant to E _peak , which is inconsistent with the previous study. The intrinsic mechanism is probably attributed to electron cooling in the decaying magnetic field, which leads to the continuous hardening of the spectrum index and results in negative lag. Furthermore, spectral analysis also shows that the third pulse is more likely to be described by a quasi-thermal spectrum, indicating the existence of photospheric emission. It is difficult to explain how the synchrotron radiation appears before photospheric emission in a single GRB, and some assumptions are discussed.

The Netherlands-China Low-Frequency Explorer (NCLE) (Boonstra et al., 2017, https://www.ursi.org/proceedings/procGA17/papers/Paper_J19-2(1603).pdf; Chen et al., 2020, https://ui.adsabs.harvard.edu/abs/2020AAS & mldr;23610203C/abstract) is a radio instrument for astrophysical studies in the low-frequency range (80 kHz-80 MHz). As a technology demonstrator, NCLE shall inform the design of future radio receivers that aim at low-frequency radio astronomy. NCLE can make observations at very high spectral resolution (<1 kHz) and generate radio sky maps at an angular resolution of approximate to 1.5 radians. NCLE uses three monopole antennas, each 5 m long, and three identical analog signal chains to process the signal from each antenna. A single digital receiver samples the signal and calculates the auto-correlated and cross-correlated spectra. The instrument's analog and digital signal chains are extensively configurable. They can be fine-tuned to produce broadband spectra covering the instrument's complete operating frequency range or sub-bands. NCLE was developed within a veryshort timescale of 2 years, and currently, it is on board Queqiao, the relay spacecraft of the Chang'e- 4 mission, in a halo orbit around the Earth-Moon L2 point. This paper outlines the science cases, instrument architecture with focus on the signal chain, and discusses the laboratory measurements during the pre-launch phase.

We report the discovery of a peculiar X-ray transient, EP240408a, by Einstein Probe (EP) and follow-up studies made with EP, Swift, NICER, GROND, ATCA and other ground-based multi-wavelength telescopes. The new transient was first detected with Wide-field X-ray Telescope (WXT) on board EP on April 8th, 2024, manifested in an intense yet brief X-ray flare lasting for 12 seconds. The flare reached a peak flux of 3.9x10^(-9) erg/cm2/s in 0.5-4 keV, about 300 times brighter than the underlying X-ray emission detected throughout the observation. Rapid and more precise follow-up observations by EP/FXT, Swift and NICER confirmed the finding of this new transient. Its X-ray spectrum is non-thermal in 0.5-10 keV, with a power-law photon index varying within 1.8-2.5. The X-ray light curve shows a plateau lasting for about 4 days, followed by a steep decay till becoming undetectable about 10 days after the initial detection. Based on its temporal property and constraints from previous EP observations, an unusual timescale in the range of 7-23 days is found for EP240408a, which is intermediate between the commonly found fast and long-term transients. No counterparts have been found in optical and near-infrared, with the earliest observation at 17 hours after the initial X-ray detection, suggestive of intrinsically weak emission in these bands. We demonstrate that the remarkable properties of EP240408a are inconsistent with any of the transient types known so far, by comparison with, in particular, jetted tidal disruption events, gamma-ray bursts, X-ray binaries and fast blue optical transients. The nature of EP240408a thus remains an enigma. We suggest that EP240408a may represent a new type of transients with intermediate timescales of the order of about 10 days. The detection and follow-ups of more of such objects are essential for revealing their origin.

2015年9月28日月基光学望远镜(Lunar-based Ultraviolet Telescope,LUT)在任务期间经历了唯一一次完整的月全食过程,为研究地球对太阳光的几何遮挡是否会对月面辐射环境产生影响提供了难得机遇.首先,利用月食期间连续长达2 h 27 min的电荷耦合器件(Charge-Coupled Device,CCD)天文观测图像,统计分析了月食期间的宇宙线事件计数,发现月食期间宇宙线计数不存在明显变化,在30 s曝光时间内,宇宙线事件平均计数为129.27(±15.78);其次,分析了8月、10～12月采集的CCD暗场图像中的宇宙线事件计数,分别为119.92(±6.37)次、117.00(±10.90)次、118.61(±8.94)次和123.90(±8.92)次,在1σ误差范围内,与月食期间的宇宙线事件计数一致,说明地球对太阳光的几何遮挡对月面辐射环境没有产生明显影响.最后对以上结果进行了分析讨论.

嫦娥四号着陆器搭载的低频射电频谱仪已成功开展观测，每月把观测数据回传到地面，并且把经过一定的预处理后的2C级别的频谱数据释放给了科学团队。本文旨在评估该级别数据是否满足探测宇宙黑暗时代21cm整体谱的要求。我们对生成的2C级别数据进行了长时间积分，并对银河系前景射电辐射被着陆器接收进行了模拟仿真。通过对两套数据进行比对分析，发现2C 数据被减弱40-50 dB，几乎不包含银河系前景的远场辐射信号，这种大幅度的减弱进而影响到了该载荷对宇宙黑暗时代的探测能力。

嫦娥四号着陆器搭载的低频射电频谱仪(Low Frequency Radio Spectrometer,LFRS)已成功开展观测,每月把观测数据传回地面,并且把经过一定预处理后的2C级别的频谱数据释放给科学团队.旨在评估该级别数据是否满足探测宇宙黑暗时代21 cm整体谱的要求,对生成的2C级别数据进行了长时间积分,并模拟仿真银河系前景射电辐射.通过对两套数据进行对比分析发现,2C数据减弱40～50 dB,几乎不包含银河系前景的远场辐射信号,这种大幅度的减弱进而影响了该载荷对宇宙黑暗时代的探测能力.

宇宙线事件是CCD和CMOS空间探测图像中普遍存在的现象,对目标的识别和提取造成了干扰.对于空间天文观测图像,提出了一种基于天文位置定标的识别算法,并在230帧嫦娥三号月基光学望远镜的CCD图像中,共检测到29731例宇宙线事件.与传统的拉普拉斯算法相比,本算法检测到的宇宙线事件总数多11.14％,多出的部分主要是形态与星像类似的宇宙线事件;在拉普拉斯算法检测到的样本中,98.07％可被本算法检测到;对本算法没有检测到的1.93％样本进行了检查,发现其中48.64％为恒星星像,是错误识别.分析统计了宇宙线事件在月基光学望远镜CCD靶面上的电子沉积分布,和哈勃太空望远镜的两个CCD探测器的结果对比,发现两者形态类似,但前者的峰值略高;进一步分析了宇宙线事件入射角度在CCD靶面上的二维分布,发现在两个方向上有明显超出,可以理解为探测器在嫦娥三号着陆器内部等效铝厚度较小.最后,本文提取出所有识别出的宇宙线事件的形态,建立了"CCD探测器宇宙线实体样本库",可为空间天文望远镜图像仿真系统提供依据.

GWAC will have been built an integrated FOV of 5,000 degree2 and have already built 1,800 square degree2. The limit magnitude of a 10-second exposure image in the moonless night is 16R. In each observation night, GWAC produces about 0.7TB of raw data, and the data processing pipeline generates millions of single frame alerts. We describe the GWAC Data Processing and Management System (GPMS), including hardware architecture, database, detection-filtering-validation of transient candidates, data archiving, and user interfaces for the check of transient and the monitor of the system. GPMS combines general technology and software in astronomy and computer field, and use some advanced technologies such as deep learning. Practical results show that GPMS can fully meet the scientific data processing requirement of GWAC. It can online accomplish the detection, filtering and validation of millions of transient candidates, and feedback the final results to the astronomer in real-time. During the observation from October of 2018 to December of 2019, we have already found 102 transients.

随着Docker技术的快速发展和越来越多被用于天文软件应用程序的部署，如何理解容器技术，将容器技术运用到天文软件开发测试工作中，成为每一个相关从业人员应该思考和快速掌握的核心虚拟化技术。文章通过对Docker技术在天文数据档案库系统测试中的应用，实现对科学数据产品长期存档与数据产品查询检索，支持各级数据产品、工程数据、标定数据、辅助数据的管理，测试科学数据产品存储、检索、提取、维护、分析、控制功能，指出在传统软件环境部署及测试中，天文软件环境复杂且运行时依赖较多第三方库支持，测试中耗费大量时间定位软件缺陷重现测试环境，介绍Docker技术在天文数据档案库系统测试应用中带来的优势和重要性，实现测试环境标准化、测试数据隔离性、测试功能扩展性，提高测试工作效率。同时也为容器技术在其它天文软件测试与应用提供借鉴参考。

With its large field of view, GWAC can record hundreds of meteors every day. These meteors are valuable treasures for some meteor research groups. It is therefore very important to accurately find all of these meteors. To address the challenge of precisely distinguishing meteors from other elongated objects in a GWAC-like sky survey system, we design and implement a meteor candidate recognition algorithm, including the recognizing and morphology analysis of the light curves of the meteor candidates. Although the algorithm may filter out some real meteors, it can provide a sample of meteor with high confidence. After processing the images of Mini-GWAC taken in two months, we detect 109,000 elongated objects in which more than 90 percent of objects are not meteor. Among the elongated objects, about 5.9% objects are identified as meteors with high confidence, after the filters based upon an existence in a single frame, a single peak in the light curves, and a slow variation of the light curves.

The Einstein Probe is a small mission dedicated to time-domain astronomy to monitor the sky in the soft X-ray band (0.5-4 keV).It will carry out systematic survey and characterisation of high-energy transients at unprecedented sensitivity,spatial resolution,Grasp and monitoring cadence.Its wide-field imaging capability,as provided by an X-ray monitor with a field of view of 3600 square degrees,is enabled by using established technology of micro-pore lobster-eye focusing optics.Complementary to this wide-field instrument is a follow-up X-ray telescope with a large effective area and a narrow field of view.It is also capable of real time triggering and downlink of transient alerts on the fly,in order to activate multi-wavelength follow-up observations by other astronomical facilities worldwide.Its scientific goals are concerned with discovering new or rare types of transients,particularly tidal disruption events,supernova shock breakouts,high-redshift gamma-ray bursts and,particularly,electromagnetic sources associated with gravitational wave events.The mission is planned for launch around end of 2022,with a lifetime of three years and five years as a goal.

Astronomy has been one of the first areas of science to embrace and learn from big data. The amount of data we have on our universe is doubling every year thanks to big telescopes and better light detectors. Most leading research is based on data from a handful of very expensive telescopes. Undoubtedly, the data quality is the key basis for the leading scientific findings. It is imperative that software testers understand that big data is about far more than simply data volume. This paper will analyze characteristics, types, methods, strategies, problems, challenges and propose some possible solutions of software testing for astronomical big data.

天文瞬变源后随观测对于瞬变源证认具有重要的意义.瞬变源发生的偶然性和光变的快速性要求后随观测系统具有快速自动响应的能力.介绍了基于Python开发的天文瞬变源快速自动响应观测系统的研究和实现,核心是基于Django架构实现数据库交互与模块调度功能.系统有基于VOEvent的警报消息传递、 网络端状态监控与交互平台、 数据自动处理和结果自动反馈以及望远镜控制接口等主要功能.通过在北京的中法天文卫星科学中心和兴隆观测基地之间的消息数据传递和实际触发观测测试表明,系统能满足中法天文卫星项目地基观测系统瞬变源后随自动响应观测的基本要求,同时系统还具有良好的可移植性,适用于其他类似的自动响应观测系统.