With the growing number of gamma-ray monitors in operation, several research teams have adopted a strategy of joint operation and scientific duty to improve efficiency. A successful example is the GECAM–HXMT–SVOM (GHS) constellation collaboration, which sets a precedent for other gamma-ray monitor constellations. However, joint duty also presents challenges to burst advocates (BAs), including an increased number of triggers and, more importantly, frequent switching between various systems due to incompatibilities among different missions, which complicates the situation. To address the current requirements of multiwavelength and multimessenger astronomy, we developed a customized framework for unified trigger processing within the GHS joint duty, named “BAs’ Rapid Evaluation and Analysis Kit for Formulating Alerts and Summary Tools” ( BREAKFAST ). This framework incorporates a series of automated, semiautomated, and manual pipelines designed to rapidly process triggers of prompt emissions in the gamma-ray band from different instruments, while maintaining flexible compatibility for future missions. The pursuit of BREAKFAST goes beyond merely providing trigger processing for BAs. BREAKFAST also aims to identify high-value targets through rapid analysis and to guide follow-up telescopes by providing timely reports, thereby serving as an important bridge between prompt-emission observations and afterglow observations. To this end, a suite of comprehensive analysis modules is included in BREAKFAST , particularly the specially designed module that predicts X-ray afterglow brightness based on prompt-emission properties. The framework’s effectiveness has already been demonstrated in recent observational campaigns, and it is expected to play a significant role in the discovery and observation of peculiar transients in the future.

Rapid and robust laser-frequency auto-locking is essential for the field deployment of quantum communications, quantum computing, and precision-measurement technologies; however, achieving this remains a considerable challenge. Here, we propose and demonstrate an auto-locking scheme employing Bayesian optimization and discrete biorthogonal wavelet transformation. First, the reference is rapidly sought by making intelligent use of historical observations, eliminating the inherent blindness of the traditional parameter-scanning method. Second, the frequency reference is robustly identified by pinpointing transition signals with the discrete biorthogonal wavelet transformation and analyzing their immutable frequency differences and relative magnitudes, which are determined by the inherent atomic structure and remain resistant to environmental disturbances. This proposed approach achieves a fivefold acceleration in reference searching compared to conventional scanning methods in the case where the laser frequency drifts far away from the reference. Crucially, it achieves an identification accuracy of more than 99.5

Abstract High-energy cosmic-ray monitoring in low Earth orbit (LEO) is important for space science and exploration, yet it is usually limited to the dedicated cosmic-ray detectors. Here we show that GECAM, although designed as a gamma-ray all-sky monitor, can monitor high-energy cosmic rays through its novel design of simultaneous-event (STE). We first combine multi-component incident-particle models with \textsc{Geant4} simulations to calibrate the particle component--energy--multiplicity response of STE, and then apply to the GECAM observation data during geomagnetic storms. The simulations show that STE signals are dominated by GeV--TeV protons, whereas the highest-fold channels, especially STE(21--25), contain a significant contribution from $\sim 10$--$20$ GeV electrons. Thus, STE(5--20) mainly trace rigidity-dependent variations of primary protons, while STE(21--25) provides an electron-sensitive diagnostic. By analyzing the GECAM observation data during geomagnetic storms, we find a STE multiplicity-dependent response which is consistent with rigidity-dependent Forbush modulation and time-dependent geomagnetic transmissivity near cutoff and penumbral regions. These results demonstrate that GECAM can monitor high-energy cosmic-ray variations in LEO as a Micro Cosmic-Ray Observatory (MICRO), complementing those dedicated cosmic-ray instruments.

The spectral evolution characteristics of the prompt emission in gamma-ray bursts (GRBs) have been extensively studied, but detailed investigations of the spectral evolution in a GRB flare remain lacking. In this work, we present the first analysis of spectral parameter evolution in a GRB flare through high-time-resolved spectral fitting of the brightest flare in GRB 221009A. We find that the alpha-flux, Ep-flux, and Ep-alpha relationships during both the overall phase and the rising phase of the flare can be well described by a simple power-law model, showing positive correlations. Therefore, we conclude that the brightest flare exhibits "double-tracking" behavior. Since values of alpha do not exceed the synchrotron "death line" (-2/3), we explain this phenomenon using the magnetic dissipation synchrotron radiation model. In the decay phase of the flare, the Ep-flux and Ep-alpha correlations become notably flatter, with their power-law indices decreasing significantly compared to those in the rising phase. This may be due to the fact that the next flare begins to erupt before the brightest flare has completely ended, resulting in the combined effects of both two flares. Our study of the spectral parameter relations of the brightest flare provides new insights into the radiation mechanisms of both the GRB prompt emission and flares.

Silicon photomultiplier (SiPM) has been increasingly used in detectors of space telescopes. As a critical parameter of SiPM, dark current could be affected by many factors, such as temperature, overvoltage, and radiation damage. However, how the dark current of SiPM evolves in long-term under different space environments has not been systematically studied yet. SiPM is utilized in a series of GECAM instruments operating in different orbits and conditions, which provides a great opportunity to study this problem. Here, we present the first results on the SiPM dark current long-term (up to 5 yr) evolution of GECAM instruments, including GECAM-A, GECAM-B, and GECAM-C. We find that, while the short-term variation of SiPM dark current is primarily caused by the temperature fluctuation, the long-term evolution is predominantly determined by the accumulated radiation dose. Based on the GECAM design, we developed a model to describe the long-term evolution of the SiPM dark current, and all the long-term dark current evolution of GECAM-A/B/C could be well fitted by our model. Based on the comparison between GECAM instruments, it is evident that the SiPM dark current growth rate is independent of the working status of the SiPM but dependent on the radiation level, which is closely related to the altitude of orbit (500-600 km). We also find that the growth of the dark current can explain the decrease in energy gain of the detector. These results provide important guidelines for the performance study and prediction of GECAM instruments as well as the design of SiPM-based detectors of future missions.

Flares are usually observed during the afterglow phases of Gamma-ray bursts (GRBs) in the soft-X-ray, optical, and radio bands—but rarely in the gamma-ray band. Despite its extraordinary brightness, GECAM-C has accurately measured both the bright prompt emission and flare emission of GRB 221009A without instrumental effects, offering a good opportunity to study the relation between them. In this work, we present a comprehensive analysis of the flare emission of GRB 221009A, which is composed of a series of flares. Among them, we identify an exceptionally bright flare with a record-breaking isotropic energy E _iso = 1.82 × 10 ^53 erg for GRB flares. It exhibits the highest peak energy ever detected in GRB flares, E _peak ∼ 300 keV, making it a genuine gamma-ray flare. It also shows rapid rise and decay timescales, significantly shorter than those of typical X-ray flares observed in the soft-X-ray or optical bands but comparable to those observed in prompt emissions. Despite these exceptional properties, the flare shares several common properties with typical GRB flares. We note that this is the first observation of a GRB flare in the keV–MeV band with sufficiently high temporal resolution and high statistics, bridging the last gap between the prompt emission and flare.

Dynamic atom gravimeters enable absolute gravity measurements on moving platforms. However, their performance is severely degraded due to the complex dynamic environment. This paper finds that the amplitude-modulation noise (AMN) is a key factor contributing to the degradation of gravity- measurement performance. We find that the AMN is induced by the cold atomic cloud trajectory and velocity variation. We build a model to illustrate the principles and magnitude of AMN arising from various experiment processes. Then we propose a method to fit the normalized AMN with respect to the kinematic parameters of the cold atomic cloud and successfully suppress this noise from 0.11 to 0.038 using the fitting result. With this method, we improve the fringe phase resolution from 0.244 to 0.092 rad and reduce the dynamic gravity-measurement noise from 2.69 to 1.68 mGal. This study finds and suppresses a key noise source in dynamic atom gravimeters, which is useful for further improving their precision. The proposed method can also be applied for precision enhancement for other dynamic atom-interferometer-based sensors, such as atom gradiometers and gyroscopes.

Flares are usually observed during the afterglow phase of Gamma-Ray Bursts (GRBs) in soft X-ray, optical and radio bands, but rarely in gamma-ray band. Despite the extraordinary brightness, GECAM-C has accurately measured both the bright prompt emission and flare emission of GRB 221009A without instrumental effects, offering a good opportunity to study the relation between them. In this work, we present a comprehensive analysis of flare emission of GRB 221009A, which is composed of a series of flares. Among them, we identify an exceptionally bright flare with a record-breaking isotropic energy E_ iso = 1.82 × 10^53 erg of GRB flares. It exhibits the highest peak energy ever detected in GRB flares, E_ peak∼ 300 keV, making it a genuine gamma-ray flare. It also shows rapid rise and decay timescales, significantly shorter than those of typical X-ray flares observed in soft X-ray or optical band, but comparable to those observed in prompt emissions. Despite these exceptional properties, the flare shares several common properties with typical GRB flares. We note that this is the first observation of a GRB flare in the keV-MeV band with sufficiently high temporal resolution and high statistics, which bridges the last gap between prompt emission and flare.

We propose and demonstrate a dynamical mirror compensation scheme to restore velocity immunity in a large-area dual-atom-interferometer gyroscope. In an ideal Mach-Zehnder configuration, the phase shift is inherently immune to atomic velocity, but this property is broken by the Earth's rotation via the Coriolis effect. We overcome this by actively rotating the Raman mirrors during the pulse sequence to cancel the time-dependent angular offset. The implementation relies on a decouplable calibration-compensation chain to remove rotation-induced time-dependent terms. The scheme is validated on a dual-atom-interferometer gyroscope with an interference area of 21.1 cm^2. After compensation, the phase's dependence on atomic velocity is reduced 40-fold, and the velocity contribution to scale-factor stability is evaluated to be 0.13 ppm. The sensor achieves a rotation sensitivity of 1.3×10^-8 rad/s/Hz^1/2 and a stability of 1.9×10^-10 rad/s at 4500 s integration, together with a common-mode noise rejection ratio of up to 459, demonstrated in a seismic event. This work removes a key obstacle to scale-factor stabilization in atom-interferometer gyroscopes and paves the way for their applications in inertial navigation and geophysics.

GECAM is a constellation of all-sky monitors in hard X-ray and gamma-ray band primarily aimed at high energy transients such as gamma-ray bursts, soft gamma-ray repeaters, solar flares and terrestrial gamma-ray flashes. As GECAM has the highest temporal resolution (0.1 μs) among instruments of its kind, it can identify the so-called simultaneous events (STE) that deposit signals in multiple detectors nearly at the same time (with a 0.3 μs window). However, the properties and origin of STE have not yet been explored. In this work, we implemented, for the first time, a comprehensive analysis of the STE detected by GECAM, including their morphology, energy deposition, and the dependence on the geomagnetic coordinates. We find that these STE probably result from direct interactions between high-energy charged cosmic rays and satellite. These results demonstrate that GECAM can detect, identify, and characterize high-energy cosmic rays, making it a Micro Cosmic-Ray Observatory (MICRO) in low Earth orbit.

The Gamma-Ray Monitor (GRM) is a key payload of the Space-based multiband astronomical Variable Objects Monitor (SVOM) mission, which is designed to detect gamma ray bursts (GRBs) within the energy range of 15 keV to 5 MeV. The GRM Instrument Center (GRM_IC) features real-time data processing through the X-band, enabling rapid response of high-energy GRB events. The system employs an event-driven architecture and distributed design, achieving efficient processing and real-time monitoring of massive observational data. Through comprehensive data production processes and scientific data product management, the system achieves efficient production of scientific data products of the L1B / C level through the submission of jobs to the task scheduling system. Through modular architecture design and automated processing workflow, the GRM data processing system realizes precise conversion and scientific analysis of GRB detection data, providing robust technical support for future system upgrades and cross-platform collaboration.

Gravitational-wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) is a constellation of all-sky monitors in hard X-ray and gamma-ray bands, primarily observing high-energy transients such as gamma-ray bursts, soft gamma-ray repeaters, solar flares, and terrestrial gamma-ray flashes. As GECAM has the highest temporal resolution (0.1 μs) among instruments of its kind, it can identify the so-called simultaneous events (STEs) that deposit signals in multiple detectors nearly at the same time (with a time window of 0.3 μs). However, the properties and origin of STEs have not yet been explored. In particular, STEs may impact the observation of high-energy transients. In this work, we present the first systematic study of the properties of STEs detected by GECAM, including the morphology, energy deposition, and the dependence on the geomagnetic latitude. Based on their properties, we suggest that these STEs probably result from direct interactions between high-energy charged cosmic rays and the satellite. GEANT4 Monte Carlo simulations using the GECAM spacecraft mass model were carried out to provide additional support for this interpretation. Our result indicates that GECAM could potentially detect and characterize the high-energy cosmic rays through STEs, thereby extending its scientific capability.

Fast radio burst (FRB) is mysterious phenomenon with millisecond-duration radio pulses observed mostly from cosmological distance. The association between FRB 200428 and a magnetar X-ray burst (MXB) from SGR J1935 + 2154 has significantly advanced the understanding of FRB and magnetar bursts. However, it is uncertain whether this association between MXB and FRB (i.e. MXB/FRB 200428) is genuine or just coincidental only based on this single event. Here we report the discovery of a bright (similar to 7.6 x 10(-7) erg . cm(-2) in 1-250 keV) magnetar X-ray burst detected by Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) on 2022 October 14 (dubbed as MXB 221014) from SGR J1935 + 2154, which is associated with an FRB detected by Canadian Hydrogen Intensity Mapping Experiment and Green Bank Telescope. We conducted a detailed temporal and spectral analysis of MXB 221014 with GECAM data and find that it is a bright and typical (T-90 similar to 250 ms) X-ray burst from this magnetar. Interestingly, we find two narrow X-ray pulses in the MXB, one of which temporally aligns with the main pulse of the FRB 221014 similar to 5.70 ms latter than the peak time of FRB 221014), resembling the feature found in MXB/FRB 200428. Furthermore, we did comprehensive comparison between MXB/FRB 221014 and MXB/FRB 200428, and find that while the two events share several common features, they also exhibit distinct differences, highlighting the variety of the MXB-FRB association morphology. This finding not only confirms the association between MXB and FRB but also provides new insights into the mechanism of and the relationship between FRB and MXB.

We propose a method for extracting the phase from atom interference fringes based on orthogonal subspace projection. By projecting the shear interference fringes from an atom interferometer into an orthogonal subspace, this method characterizes and removes the atomic ensemble envelope, thereby isolating the interference phase information. We systematically investigate the phase extraction accuracy of this method under various conditions, including different atomic ensemble envelope shapes and fringe contrasts, and apply it to analyze experimental data from two practical atom interferometers. The study demonstrates that, compared to the conventional direct model fitting method, our approach more accurately extracts the interference phase under conditions involving nonideal and dynamically varying atomic ensemble envelopes as well as low-contrast fringes, thereby improving the accuracy and robustness of the atom interferometer. This makes it particularly valuable for application-oriented atom shear interferometers operating in complex environments.

The spectral evolution characteristics of the prompt emission in gamma-ray bursts (GRBs) have been extensively studied, but detailed investigations of spectral evolution in a GRB flare remain lacking. In this work, we present the first analysis of spectral parameter evolution in a GRB flare through high time-resolved spectral fitting of the Brightest Flare in GRB 221009A. We find that the α-Flux, E_p-Flux, and E_p-α relationships during both the overall phase and the rise phase of flare can be well described by simple power-law model, showing positive correlations. Therefore, we conclude that Brightest Flare exhibits "Double-tracking" behavior. Since values of α do not exceed the synchrotron "death line" (-2/3), we explain this phenomenon using a magnetic dissipation synchrotron radiation model. In the decay phase of flare, the E_p-Flux and E_p-α correlations become notably flatter, with their power-law indices decreasing significantly compared to those in the rise phase. This may be due to the fact that the next flare begins to erupt before the Brightest Flare has completely ended, resulting in the combined effects of both two flares. Our study of spectral parameter relations of the Brightest Flare provides new insights into the radiation mechanisms of both GRB prompt emission and flares.

Defect-free single-atom arrays in optical tweezers are a promising platform for scalable quantum computing, quantum simulation, and quantum metrology. Extending single-species arrays to mixed-species ones promises to offer other possibilities. In our recent proof-of-principle realization of defect-free Lett. 128, 083202 (2022)], the filling fractions were limited by imperfect atom transfer and algorithmic limitations during the rearrangement process. To scale up defect-free mixed-species atom arrays, we increase the tweezer-array size, improve atom-transfer efficiency, and upgrade the heuristic heteronuclear algorithm-removing the need for subpartitioning, incorporating flexibility moves to overcome path blocking, enabling efficient multicycle rearrangement, and thereby achieving higher success rates in larger arrays. Consequently, we successfully created defect-free arrays containing 120 mixed-species atoms. The resulting filling fraction and defect-free probability improved to 98.3(1)% and 14(2)%, respectively. We anticipate that the enhanced algorithm can be extended to other atomic species combinations, making these mixed-species arrays readily available for studies of many-body physics, quantum error correction, and quantum metrology.

Fast radio bursts (FRBs) are enigmatic cosmic transients of millisecond duration observed in the radio band. The identification of FRB-associated magnetar X-ray bursts (MXBs) from the galactic magnetar SGR J1935+2154 suggests that at least a fraction of FRBs can be produced from magnetar activity. However, the sample size of FRB-associated MXBs is still very small. Here we report a bright and peculiar FRB-associated MXB from SGR J1935+2154 detected by GECAM on November 20, 2022, dubbed MXB 221120. We find that the temporal and spectral properties of MXB 221120 exhibit distinctive features. Its light curve could generally be described by a single FRED function with the superposition of several narrow pulses. Interestingly, we identified a possible quasiperiodic oscillation feature with a center frequency of ∼18 Hz in this MXB. The time-integrated spectrum is best fit by a blackbody model with a temperature (kT) of 18.6 keV, rendering it the first thermal spectrum FRB-associated MXB from SGR J1935+2154. Compared to other MXBs with a single emission episode, MXB 221120 has a longer duration and a higher blackbody temperature, making it an outlier in the burst sample. These results indicate that MXB 221120 may have been produced by a special mechanism with extreme physical conditions.

Differential light shift (DLS) is an important error term that limits the atom interferometer’s measurement precision, especially for the case of the electro-optic modulator (EOM)-based scheme, where multiple laser sidebands exist, and their ratios are hard to control synchronously. This article carried out an experimental and theoretical study on this subject. By conducting long-term gravity measurement, we find that the gravity exhibits drifts of about 13.13 μGal, and is strongly correlated to the Raman laser’s sidebands. A model of the DLS-induced gravity error is established and a DLS compensation method is proposed to suppress the gravity drift to 2.54 μGal. Besides the compensation method, we propose a Dual-Sideband Ratio Locking scheme to more robustly eliminate the gravity measurement drift. By feeding back to both the EOM microwave power and the tapered amplifier’s temperature, this method locks both the ±1 order sideband to a stability level of 10−5, which corresponds to a gravity error of less than 0.1 μGal. Long-term gravity measurement is carried out after the locking method, showing a long-term stability of 1.6 μGal. The proposed methods will benefit the suppression of the DLS effect for high-precision atom interference measurement.