Short Bursts Research Articles

The Jet Opening Angle and Event Rate Distributions of Short Gamma-Ray Bursts from Late-time X-Ray Afterglows

We present a comprehensive study of 29 short gamma-ray bursts (SGRBs) observed ≈0.8−60 days postburst using Chandra and XMM-Newton. We provide the inferred distributions of the SGRB jet opening angles and true event rates to compare against neutron star merger rates. We perform a uniform analysis and modeling of their afterglows, obtaining 10 opening angle measurements and 19 lower limits. We report on two new opening angle measurements (SGRBs 050724A and 200411A) and eight updated values, obtaining a median value of 〈θ j〉 ≈ 6.°1 [−3.°2, +9.°3] (68% confidence on the full distribution) from jet measurements alone. For the remaining events, we infer θ j ≳ 0.°5–26°. We uncover a population of SGRBs with wider jets of θ j ≳ 10° (including two measurements of θ j ≳ 15°), representing ∼28% of our sample. Coupled with multiwavelength afterglow information, we derive a total true energy of 〈E true,tot〉 ≈ 1049–1050 erg, which is consistent with magnetohydrodynamic jet launching mechanisms. Furthermore, we determine a range for the beaming-corrected event rate of Gpc−3 yr−1, set by the inclusion of a population of wide jets on the low end, and the jet measurements alone on the high end. From a comparison with the latest merger rates, our results are consistent with the majority of SGRBs originating from binary neutron star mergers. However, our inferred rates are well above the latest neutron star–black hole merger rates, consistent with at most a small fraction of SGRBs originating from such mergers.

A Unified Picture of Short and Long Gamma-Ray Bursts from Compact Binary Mergers

The recent detections of the ∼10 s long γ-ray bursts (GRBs) 211211A and 230307A followed by softer temporally extended emission (EE) and kilonovae point to a new GRB class. Using state-of-the-art first-principles simulations, we introduce a unifying theoretical framework that connects binary neutron star (BNS) and black hole–NS (BH–NS) merger populations with the fundamental physics governing compact binary GRBs (cbGRBs). For binaries with large total masses, M tot ≳ 2.8 M ⊙, the compact remnant created by the merger promptly collapses into a BH surrounded by an accretion disk. The duration of the pre-magnetically arrested disk (MAD) phase sets the duration of the roughly constant power cbGRB and could be influenced by the disk mass, M d . We show that massive disks (M d ≳ 0.1 M ⊙), which form for large binary mass ratios q ≳ 1.2 in BNS or q ≲ 3 in BH–NS mergers, inevitably produce 211211A-like long cbGRBs. Once the disk becomes MAD, the jet power drops with the mass accretion rate as , establishing the EE decay. Two scenarios are plausible for short cbGRBs. They can be powered by BHs with less massive disks, which form for other q values. Alternatively, for binaries with M tot ≲ 2.8 M ⊙, mergers should go through a hypermassive NS (HMNS) phase, as inferred for GW170817. Magnetized outflows from such HMNSs, which typically live for ≲1 s, offer an alternative progenitor for short cbGRBs. The first scenario is challenged by the bimodal GRB duration distribution and the fact that the Galactic BNS population peaks at sufficiently low masses that most mergers should go through an HMNS phase.

Educator's blueprint: A how-to guide for creating analog serious games for learning in medical education.

Serious games are an emerging tool for teaching and learning within medical education. These games can be used to facilitate learning or to demonstrate complex concepts in short bursts of interactive learning. This educator's blueprint will provide 10 strategies for creating a serious game, focusing on card and board games. These strategies include creating a project charter; determining the nature of the game; establishing game mechanics; selecting the best medium; prototyping and playtesting; reviewing sensitivity to equity, diversity, and inclusion; reviewing and refining content; funding game development, manufacture, and distribution; marketing and publicizing the game; and future-proofing the game. This blueprint hopes to help aspiring serious game designers and educators to conceptualize the steps for successfully creating a new serious game for medical education.

Impact of anisotropic ejecta on jet dynamics and afterglow emission in binary neutron-star mergers

ABSTRACT Binary neutron-stars mergers widely accepted as potential progenitors of short gamma-ray bursts. After the remnant of the merger has collapsed to a black hole, a jet is powered and may breakout from the the matter expelled during the collision and the subsequent wind emission. The interaction of the jet with the ejecta may affect its dynamics and the resulting electromagnetic counterparts. We here examine how an inhomogeneous and anisotropic distribution of ejecta affects such dynamics, dictating the properties of the jet-ejecta cocoon and of the afterglow radiated by the jet upon deceleration. More specifically, we carry out general-relativistic hydrodynamical simulations of relativistic jets launched within a variety of geometrically inhomogeneous and anisotropic distributions of ejected matter. We find that different anisotropies impact the variance of the afterglow light curves as a function of the jet luminosity and ejected mass. A considerable amount of the jet energy is deposited in the cocoon through the jet-ejecta interaction with a small but important dependence on the properties of the ejecta. Furthermore, all configurations show a two-component behaviour for the polar structure of the jet, with a narrow core at large energies and Lorentz factors and a shallow segment at high latitudes from the jet axis. Hence, afterglows measured on off-axis lines of sight could be used to deduce the properties of the ejected matter, but also that the latter need to be properly accounted for when modelling the afterglow signal and the jet-launching mechanisms.

Gamma-ray burst precursors from tidally resonant neutron star oceans: potential implications for GRB 211211A

ABSTRACT Precursors have been observed seconds to minutes before some short gamma-ray bursts. While the precursor origins remain unknown, one explanation relies on the resonance of neutron star pulsational modes with the tidal forces during the inspiral phase of a compact binary merger. In this paper, we present a model for short gamma-ray burst precursors that relies on tidally resonant neutron star oceans. In this scenario, the onset of tidal resonance in the crust–ocean interface mode ignites the precursor flare, possibly through the interaction between the excited neutron star ocean and the surface magnetic fields. From just the precursor total energy, the time before the main event, and a detected quasi-periodic oscillation frequency, we may constrain the binary parameters and neutron star ocean properties. Our model can immediately distinguish neutron star–black hole mergers from binary neutron star mergers without gravitational wave detection. We apply our model to GRB 211211A, the recently detected long duration short gamma-ray burst with a quasi-periodic precursor, and explore the parameters of this system. The precursor of GRB 211211A is consistent with a tidally resonant neutron star ocean explanation that requires an extreme mass ratio neutron star–black hole merger and a high-mass neutron star. While difficult to reconcile with the main gamma-ray burst and associated kilonova, our results constrain the possible precursor mechanisms in this system. A systematic study of short gamma-ray burst precursors with the model presented here can test precursor origin and probe the possible connection between gamma-ray bursts and neutron star–black hole mergers.

A targeted search for FRB counterparts with Konus-Wind

ABSTRACT We present results of the search for hard X-ray/soft gamma-ray emission in coincidence with publicly reported (via Transient Name Server, TNS1) fast radio bursts (FRBs). The search was carried out using continuous Konus-Wind data with 2.944 s time resolution. We perform a targeted search for each individual burst from 581 FRBs, along with a stacking analysis of the bursts from eight repeating sources in our sample and a separate stacking analysis of the bursts from the non-repeating FRBs. We find no significant associations in either case. We report upper bounds on the hard X-ray (20–1500 keV) flux assuming four spectral models, which generally describe spectra of short and long gamma-ray bursts (GRBs), magnetar giant flares, and the short burst, coincident with FRB 200428 from a Galactic magnetar. Depending on the spectral model, our upper bounds are in the range of (0.1–2) × 10−6 erg cm−2. For 18 FRBs with known distances, we present upper bounds on the isotropic equivalent energy release and peak luminosity. For the nearest FRB 200120E, we derive the most stringent upper bounds of Eiso ≤ 2.0 × 1044 erg and Liso ≤ 1.2 × 1044 erg s−1. Furthermore, we report lower bounds on radio-to-gamma-ray fluence ratio Eradio/Eiso ≥ 10−11–10−9 and compare our results with previously reported searches and theoretical predictions for high-energy counterparts to FRBs.

The Emergence of Regional Industrial Policy in Britain: The Case of Wales, 1939 to 1947

From the 1940s to the 1970s, British governments steered manufacturing businesses to peripheral regions designated as needing more employment. This approach was delivered through a Regional Policy that deployed industrial location controls and financial incentives. Effectiveness varied over time but was dramatic in the mid-1940s, when it boosted the regional stock of secondary manufacturing to the extent that its legacy remains visible today. The literature describes how this Regional Policy was a peacetime policy, albeit one formulated during the war. This article, however, proposes that the most successful phase of Regional Policy was an extension of wartime policies governing regional manufacturing businesses producing munitions. It uses a case study of Wales to make two arguments. One is that the Regional Policy associated with the postwar period began to be implemented before the war had ended. The other is that the Board of Trade pursued the policy through repurposed wartime governance mechanisms within an economy that remained subject to onerous state controls. The case outlines a short but consequential burst of assertive state involvement that shaped business activity throughout much of regional Britain, echoing Philip Scranton and Patrick Fridenson’s arguments concerning “the state always being in” given its role in shaping markets, business behavior, and regulations.

Burst c-VEP Based BCI: Optimizing stimulus design for enhanced classification with minimal calibration data and improved user experience

The utilization of aperiodic flickering visual stimuli under the form of code-modulated Visual Evoked Potentials (c-VEP) represents a pivotal advancement in the field of reactive Brain–Computer Interface (rBCI). A major advantage of the c-VEP approach is that the training of the model is independent of the number and complexity of targets, which helps reduce calibration time. Nevertheless, the existing designs of c-VEP stimuli can be further improved in terms of visual user experience but also to achieve a higher signal-to-noise ratio, while shortening the selection time and calibration process. In this study, we introduce an innovative variant of code-VEP, referred to as “Burst c-VEP”. This original approach involves the presentation of short bursts of aperiodic visual flashes at a deliberately slow rate, typically ranging from two to four flashes per second. The rationale behind this design is to leverage the sensitivity of the primary visual cortex to transient changes in low-level stimuli features to reliably elicit distinctive series of visual evoked potentials. In comparison to other types of faster-paced code sequences, burst c-VEP exhibit favorable properties to achieve high bitwise decoding performance using convolutional neural networks (CNN), which yields potential to attain faster selection time with the need for less calibration data. Furthermore, our investigation focuses on reducing the perceptual saliency of c-VEP through the attenuation of visual stimuli contrast and intensity to significantly improve users’ visual comfort. The proposed solutions were tested through an offline 4-classes c-VEP protocol involving 12 participants. Following a factorial design, participants were instructed to focus on c-VEP targets whose pattern (burst and maximum-length sequences) and amplitude (100% or 40% amplitude depth modulations) were manipulated across experimental conditions. Firstly, the full amplitude burst c-VEP sequences exhibited higher accuracy, ranging from 90.5% (with 17.6s of calibration data) to 95.6% (with 52.8s of calibration data), compared to its m-sequence counterpart (71.4% to 85.0%). The mean selection time for both types of codes (1.5 s) compared favorably to reports from previous studies. Secondly, our findings revealed that lowering the intensity of the stimuli only slightly decreased the accuracy of the burst code sequences to 94.2% while leading to substantial improvements in terms of user experience. Taken together, these results demonstrate the high potential of the proposed burst codes to advance reactive BCI both in terms of performance and usability. The collected dataset, along with the proposed CNN architecture implementation, are shared through open-access repositories.

Room temperature control of grain orientation via directionally modulated current pulses

Traditional approaches to control the microstructure of materials, such as annealing, require high temperature treatment for long periods of time. In this study, we present a room temperature microstructure manipulation method by using the mechanical momentum of electrical current pulses. In particular, a short burst of high-density current pulses with low duty cycle is applied to an annealed FeCrAl alloy, and the corresponding response of microstructure is captured by using Electron Backscattered Diffraction (EBSD) analysis. We show evidence of controllable changes in grain orientation at specimen temperature around 28 °C. To demonstrate such microstructural control, we apply the current pulses in two perpendicular directions and observe the corresponding grain rotation. Up to 18° of grain rotation was observed, which could be reversed by varying the electropulsing direction. Detailed analysis at the grain level reveals that electropulsing in a specific direction induces clockwise rotation from their pristine state, while subsequent cross-perpendicular electropulsing results in an anticlockwise rotation. In addition, our proposed room temperature processing yields notable grain refinement, while the average misorientation and density of low-angle grain boundaries (LAGBs) remain unaltered. The findings of this study highlight the potentials of ‘convective diffusion’ in electrical current based materials processing science towards microstructural control at room temperature.

The Galactic neutron star population – II. Systemic velocities and merger locations of binary neutron stars

ABSTRACT The merger locations of binary neutron stars (BNSs) encode their galactic kinematics and provide insights into their connection to short gamma-ray bursts (SGRBs). In this work, we use the sample of Galactic BNSs with measured proper motions to investigate their kinematics and predict their merger locations. Using a synthetic image of the Milky Way and its Galactic potential we analyse the BNS mergers as seen from an extragalactic viewpoint and compare them to the location of SGRBs on and around their host galaxies. We find that the Galactocentric transverse velocities of the BNSs are similar in magnitude and direction to those of their Local Standards of Rest, which implies that the present-day systemic velocities are not isotropically oriented and the peculiar velocities might be as low as those of BNS progenitors. Both systemic and peculiar velocities fit a lognormal distribution, with the peculiar velocities being as low as ∼22–157 km s−1. We also find that the observed BNS sample is not representative of the whole Galactic population, but rather of systems born around the Sun’s location with small peculiar velocities. When comparing the predicted BNS merger locations to SGRBs, we find that they cover the same range of projected offsets, host-normalized offsets, and fractional light. Therefore, the spread in SGRB locations can be reproduced by mergers of BNSs born in the Galactic disc with small peculiar velocities, although the median offset match is likely a coincidence due to the biased BNS sample.

Quasi-periodic oscillations during magnetar giant flares in the strangeon star model

ABSTRACT Soft gamma-ray repeaters (SGRs) are widely understood as slowly rotating isolated neutron stars. Their generally large spin-down rates, high magnetic fields, and strong outburst energies render them different from ordinary pulsars. In a few giant flares (GFs) and short bursts of SGRs, high-confidence quasi-periodic oscillations (QPOs) were observed. Although remaining an open question, many theoretical studies suggest that the torsional oscillations caused by starquakes could explain QPOs. Motivated by this scenario, we systematically investigate torsional oscillation frequencies based on the strangeon star (SS) model with various values of harmonic indices and overtones. To characterize the strong-repulsive interaction at short distances and the non-relativistic nature of strangeons, a phenomenological Lennard–Jones model is adopted. We show that, attributing to the large shear modulus of SSs, our results explain well the high-frequency QPOs (≳150 Hz) during the GFs. The low-frequency QPOs (≲150 Hz) can also be interpreted when the ocean–crust interface modes are included. We also discuss possible effects of the magnetic field on the torsional mode frequencies. Considering realistic models with general-relativistic corrections and magnetic fields, we further calculate torsional oscillation frequencies for quark stars. We show that it would be difficult for quark stars to explain all QPOs in GFs. Our work advances the understanding of the nature of QPOs and magnetar asteroseismology.

What constraints can one pose on the maximum mass of neutron stars from multimessenger observations?

ABSTRACT The maximum mass of neutron stars (MTOV) plays a crucial role in understanding their equation of state (EoS). Previous studies have used the measurements for the compactness of massive pulsars and the tidal deformability of neutron stars in binary neutron star (BNS) mergers to constrain the EoS and thus the MTOV. The discovery of the most massive pulsar, PSR J0952−0607, with a mass $\sim 2.35\, {\rm M}_{\odot }$, has provided a valuable lower limit for MTOV. Another efficient method to constrain MTOV is by examining the type of central remnant formed after a BNS merger. Gravitational wave (GW) data can provide the total mass of the system, while accompanying electromagnetic signals can help infer the remnant type. In this study, we combine all the previous constraints and utilize the observational facts that about 24 per cent of the short gamma-ray bursts are followed by an X-ray internal plateau, which indicate that roughly this fraction of BNS mergers yield supermassive neutron stars, to perform (Markov Chain) Monte Carlo simulations. These simulations allow us to explore the probability density distribution of MTOV and other parameters related to BNS mergers. Our findings suggest that MTOV is likely around $2.49\!-\!2.52\, {\rm M}_{\odot }$, with an uncertainty range of approximately [$-0.16$, $0.15\, {\rm M}_{\odot }$] ([$-0.28$, $0.26\, {\rm M}_{\odot }$]) at 1σ (2σ) confidence level. Furthermore, we examine the type of merger remnants in specific events like GW170817 and GW190425 to further constrain MTOV and other relevant parameters, which can help to understand the physical processes involved in BNS mergers.

Tunable in situ near-UV pulses by transient plasmonic resonance in nanocomposites.

We propose a concept for generation of ultrashort pulses based on transient field-induced plasmonic resonance in nanoparticle composites. Photoionization and free-carrier plasma generation change the susceptibility of nanoparticles on a few-femtosecond scale under the action of the pump pulse. This opens a narrow time window when the system is in plasmonic resonance, which is accompanied by a short burst of the local field. During this process, frequency-tunable few-fs pulses can be emitted. This paves a way to ultra-compact yet efficient generation of ultrashort pulses at short wavelengths.

Retracted: Cortical Plasticity Mechanism and Efficacy Prediction of Repeated Transcranial Magnetic Stimulation in the Treatment of Depression with Continuous Short Bursts of Rapid Pulse Stimulation (cTBS).

[This retracts the article DOI: 10.1155/2022/5741114.].

Drifting discrete Jovian radio bursts reveal acceleration processes related to Ganymede and the main aurora

Radio detection at high time-frequency resolutions is a powerful means of remotely studying electron acceleration processes. Radio bursts have characteristics (polarization, drift, periodicity) making them easier to detect than slowly variable emissions. They are not uncommon in solar system planetary magnetospheres, the powerful Jovian “short bursts (S-bursts)" induced by the Io-Jupiter interaction being especially well-documented. Here we present a detection method of drifting radio bursts in terabytes of high resolution time-frequency data, applied to one month of ground-based Jupiter observations. Beyond the expected Io-Jupiter S-bursts, we find decameter S-bursts related to the Ganymede-Jupiter interaction and the main Jovian aurora, revealing ubiquitous Alfvénic electron acceleration in Jupiter’s high-latitude regions. Our observations show accelerated electron energies are distributed in two populations, kilo-electron-Volts and hundreds of electron-Volts. This detection technique may help characterizing inaccessible astrophysical sources such as exoplanets.

A multimessenger model for neutron star–black hole mergers

ABSTRACT We present a semi-analytic model for predicting kilonova light curves from the mergers of neutron stars with black holes (NSBH). The model is integrated into the mosfit platform, and can generate light curves from input binary properties and nuclear equation-of-state considerations, or incorporate measurements from gravitational wave (GW) detectors to perform multimessenger parameter estimation. The rapid framework enables the generation of NSBH kilonova distributions from binary populations, light curve predictions from GW data, and statistically meaningful comparisons with an equivalent binary neutron star (BNS) model in mosfit. We investigate a sample of kilonova candidates associated with cosmological short gamma-ray bursts, and demonstrate that they are broadly consistent with being driven by NSBH systems, though most have limited data. We also perform fits to the very well sampled GW170817, and show that the inability of an NSBH merger to produce lanthanide-poor ejecta results in a significant underestimate of the early (≲2 d) optical emission. Our model indicates that NSBH-driven kilonovae may peak up to a week after merger at optical wavelengths for some observer angles. This demonstrates the need for early coverage of emergent kilonovae in cases where the GW signal is either ambiguous or absent; they likely cannot be distinguished from BNS mergers by the light curves alone from ∼2 d after the merger. We also discuss the detectability of our model kilonovae with the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST).

Renewable energy and the promise of jobs, regional regeneration and first nations opportunities

ABSTRACT Carbon-exposed regions tied to the fossil-fuel industry have uncertain futures. The promise of regional regeneration and job stimulus through a transition to renewable energy has been presented by governments, environmental organisations and some unions as a viable solution to their dilemmas. In this paper, we critically evaluate the job generation and local development possibilities from two high profile renewable energy initiatives – offshore wind farms and hydrogen hubs. Our starting point is that the debate to date has tended to be very narrowly focused on ‘employment estimates for renewable versus fossil fuel industries’ without consideration of where these jobs will be located and the nature of these jobs. Adopting a case study method, we consider the development of offshore wind farms and hydrogen hubs in Australia and their location within global value chains (GVCs) and the temporal and spatial dimensions of work required for developing, operating and maintaining these emerging industries. We demonstrate how the low labour intensity of ongoing work in offshore wind and hydrogen hubs means that new jobs created are mostly in short bursts of temporary labour in project construction.

Deep Multimessenger Search for Compact Binary Mergers in LIGO, Virgo, and Fermi/GBM Data from 2016–2017

GW170817–GRB 170817A provided the first observation of gravitational waves from a neutron star merger with associated transient counterparts across the entire electromagnetic spectrum. This discovery demonstrated the long-hypothesized association between short gamma-ray bursts and neutron star mergers. More joint detections are needed to explore the relation between the parameters inferred from the gravitational wave and the properties of the gamma-ray burst signal. We developed a joint multimessenger analysis of LIGO, Virgo, and Fermi/GBM data designed for detecting weak gravitational-wave transients associated with weak gamma-ray bursts. As such, it does not start from confident (GWTC-1) events only. Instead, we take the full list of existing compact binary coalescence triggers generated with the PyCBC pipeline from the second Gravitational-Wave Observing Run (O2), and reanalyze the entire set of public Fermi/GBM data covering this observing run to generate a corresponding set of gamma-ray burst candidate triggers. We then search for coincidences between the gravitational-wave and gamma-ray burst triggers without requiring a confident detection in any channel. The candidate coincidences are ranked according to a statistic combining each candidate’s strength in gravitational-wave and gamma-ray data, their time proximity, and the overlap of their sky localization. The ranking is then converted to a false alarm rate using time shifts between the gravitational-wave and gamma-ray burst triggers. We present the results using O2 triggers, which allowed us to check the validity of our method against GW170817–GRB 170817A. We also discuss the different configurations tested to maximize the significance of the joint detection.

Patterns of physical activity and sedentary behavior in child and adolescent cancer survivors assessed using wrist accelerometry: A cluster analysis approach.

Physical activity levels among childhood cancer survivors are typically quantified as a total amount using time spent in various intensities. Yet, most analyses do not consider the transitory nature of children's behaviors and a more detailed approach could provide complimentary information. We aimed to explore various behavior profiles of survivors' daily and hourly physical activity patterns. We measured 8-18-year-old survivors' activity levels over 7days using wrist accelerometry and cluster analysis. Of the 37 participant datasets, survivors engaged in mean (SD) 36.3 (19.0) min/day of MVPA and 4.1 (1.9) hrs/day of sedentary activity. The cluster analysis revealed five daily movement patterns: 'most active' (prevalence 11%), 'active' (22%), 'moderately active + moderately sedentary' (35%), 'moderately active + high sedentary' (5%) and 'least active' (27%). Younger survivors and those with less time since treatment completion were more likely to be in the active clusters. Hourly behaviors were characterized by short bursts of MVPA and moderate bouts of sedentary activity. Our approach provides an insightful analysis into the nature and timing of childhood cancer survivors' movement behaviours. Our findings may assist in the development of targeted interventions to improve physical activity levels.

Semi‐blind demodulation algorithm for short burst FM‐MFSK based on STFT

AbstractIn the blind reception of non‐cooperative signals in short‐time burst communication, signal time domain detection is the premise and key of signal modulation parameter estimation, signal demodulation, decoding, interpretation, information acquisition and interference guidance. In this paper, the semi‐blind demodulation method of short‐time burst FM‐MFSK signal is studied under the condition of low signal‐to‐noise ratio. A short‐time burst FM‐MFSK semi‐blind demodulation method based on STFT is proposed. When SNR is higher than 3 dB, the correct demodulation probability for FM‐MFSK signal can reach 90%.