Early X-ray Research Articles

GRB 210610B: The Internal and External Plateau as Evidence for the Delayed Outflow of Magnetar

After launching a jet, outflows of magnetar were used to account for the achromatic plateau of afterglow and the early X-ray flux plateau known as “internal plateau”. The lack of detecting magnetic dipole emission together with the energy injection feature in a single observation poses confusion until the long gamma-ray burst (GRB) 210610B is detected. GRB 210610B is presented with an optical bump following an early X-ray plateau during the afterglow phase. The plateau followed by a steep decline flux overlays in the steadily decaying X-ray flux with index α X,1 ∼ 2.06, indicating an internal origin and that can be fitted by the spin-down luminosity law with the initial plateau luminosity log10LX∼48.29ergs−1 and the characteristic spin-down timescale T ∼ 2818 s. A subsequent bump begins at ∼4000 s in the R band with a rising index α R,1 ∼ − 0.30 and peaks at ∼14125 s, after which a decay index α R,2 ∼ 0.87 and finally transiting to a steep decay with α R,3 ∼ 1.77 achieve the closure relation of the external shock for the normal decay phase as well as the magnetar spin-down energy injection phase, provided that the average value of the photon index Γ γ = 1.80 derived from the spectral energy distributions (SEDs) between the X-ray and optical afterglow. The closure relation also works for the late X-ray flux. Akin to the traditional picture of GRB, the outflow powers the early X-ray plateau by dissipating energy internally and collides with the leading decelerating blast burst as time goes on, which could interpret the exotic feature of GRB 210610B. We carry out a Markov Chain Monte Carlo simulation and obtain a set of best parameters: ϵ B ≃ 4.7 × 10−5, ϵ e ≃ 0.15, E K,iso ≃ 4.6 × 1053erg, Γ0 ≃ 832, A * ≃ 0.10, L inj,0 ≃ 3.55 × 1050erg s−1. The artificial light curve can fit the afterglow data well. After that, we estimated the average Lorentz factor and the X-ray radiation efficiency of the later ejecta are 35% and 0.13%, respectively.

Constraining the properties of Population III galaxies with multiwavelength observations

ABSTRACT The early Universe, spanning 400 000 to 400 million years after the big bang (z ≈ 1100–11), has been left largely unexplored as the light from luminous objects is too faint to be observed directly. While new experiments are pushing the redshift limit of direct observations, measurements in the low-frequency radio band promise to probe early star and black hole formation via observations of the hydrogen 21-cm line. In this work, we explore synergies between 21-cm data from the HERA and SARAS 3 experiments and observations of the unresolved radio and X-ray backgrounds using multiwavelength Bayesian analysis. We use the combined data set to constrain properties of Population II and Population III stars as well as early X-ray and radio sources. The joint fit reveals a 68 percentile disfavouring of Population III star formation efficiencies $\gtrsim 5.7~{{\ \rm per\ cent}}$. We also show how the 21-cm and the X-ray background data synergistically constrain opposite ends of the X-ray efficiency prior distribution to produce a peak in the 1D posterior of the X-ray luminosity per star formation rate. We find (at 68 per cent confidence) that early galaxies were likely 0.3–318 times as X-ray efficient as present-day starburst galaxies. We also show that the functional posteriors from our joint fit rule out global 21-cm signals deeper than ≲−203 mK and power spectrum amplitudes at k = 0.34 h Mpc−1 greater than $\Delta _{21}^2 \gtrsim 946\ \mathrm{mK}^2$ with 3σ confidence.

Probing Electromagnetic Gravitational-wave Emission Coincidence in a Type I Binary-driven Hypernova Family of Long Gamma-Ray Bursts at Very High Redshift

The repointing time of the X-Ray Telescope (XRT) instrument on the Neil Gehrels Swift Observatory satellite has posed challenges in observing and studying the early X-ray emissions within ≈40 s after a gamma-ray burst (GRB) trigger. To address this issue, we adopt a novel approach that capitalizes on the cosmological time dilation in GRBs with redshifts ranging from 3 to 9. Applying this strategy to Swift/XRT data, we investigate the earliest X-ray emissions of 368 GRBs from the Swift catalog, including short and long GRBs. We compare the observed time delay between the GRB trigger and the initial Swift/XRT observation, measured in the GRB observer frame, and the corresponding cosmological rest-frame time delay (RTD). This technique is here used in the analysis of GRB 090423 at z = 8.233 (RTD ∼8.2 s), GRB 090429B at z ≈ 9.4 (RTD ∼10.1 s), and GRB 220101A at z = 4.61 (RTD ∼14.4 s). The cosmological time dilation enables us to observe the very early X-ray afterglow emission in these three GRBs. We thus validate the observation of the collapse of the carbon–oxygen core and the coeval newborn neutron star (νNS) formation triggering the GRB event in the binary-driven hypernova (BdHN) scenario. We also evidence the νNS spin-up due to supernova ejecta fallback and its subsequent slowing down due to the X-ray/optical/radio synchrotron afterglow emission. A brief gravitational-wave signal may separate the two stages owing to a fast-spinning νNS triaxial-to-axisymmetric transition. We also analyze the long GRB redshift distribution for the different BdHN types and infer that BdHNe II and III may originate the NS binary progenitors of short GRBs.

Cascade Radiations of e ± from γγ-annihilation Process as an Extra Component of the Early Optical/X-Ray Afterglows of Gamma-Ray Bursts

Chromatic break and/or plateau observed in the early optical and X-ray afterglow lightcurves challenge the conventional external shock models of gamma-ray bursts (GRBs). Detection of TeV gamma-ray afterglows indicates strong gamma-ray production within the afterglow jets. We investigate the cascade radiations of the e ± production via the γ γ interaction in the jets. Our numerical calculations show that the cascade synchrotron emission can make a significant contribution to the early optical/X-ray afterglows. The combination of the primary and cascade emission fluxes can shape a chromatic break and/or plateau in the early optical/X-ray lightcurves, depending on the jet properties. Applying our model to GRBs 050801 and 080310, we found that their optical plateaus and the late X-ray/optical lightcurves can be explained with our model in reasonable parameter values. We suggest that such a chromatic optical plateau could be a signature of strong e ± production in GRB afterglow jets. The TeV gamma-ray flux of such GRBs should be significantly reduced and hence tends to be detectable for those GRBs that have a single power-law decaying optical afterglow lightcurve.

Ending the prompt phase in photospheric models of gamma-ray bursts

The early steep decay, a rapid decrease in X-ray flux as a function of time following the prompt emission, is a robust feature seen in almost all gamma-ray bursts with early enough X-ray observations. This peculiar phenomenon has often been explained as emission from high latitudes of the last flashing shell. However, in photospheric models of gamma-ray bursts, the timescale of high-latitude emission is generally short compared to the duration of the steep decay phase, and hence an alternative explanation is needed. In this paper we show that the early steep decay can directly result from the final activity of the dying central engine. We find that the corresponding photospheric emission can reproduce both the temporal and spectral evolution observed. This requires a late-time behaviour that should be common to all gamma-ray burst central engines, and we estimate the necessary evolution of the kinetic power and the Lorentz factor. If this interpretation is correct, observation of the early steep decay can give us insights into the last stages of central activity, and provide new constraints on the late evolution of the Lorentz factor and photospheric radius.

What Powered the Kilonova-like Emission after GRB 230307A in the Framework of a Neutron Star–White Dwarf Merger?

The second brightest gamma-ray burst, GRB 230307A (with a duration T 90 ∼ 40 s), exhibited characteristics indicative of a magnetar engine during the prompt emission phase. Notably, a suspected kilonova was identified in its follow-up optical and infrared observations. Here we propose that the origin of GRB 230307A is a neutron star–white dwarf (NS–WD) merger as this could naturally explain the long duration and the large physical offset from the center of its host galaxy. In the framework of such an NS–WD merger event, the late-time kilonova-like emission is very likely to be powered by the spin-down of the magnetar and the radioactive decay of 56Ni, rather than by the decay of r-process elements as these heavy elements may not easily be synthesized in an NS-WD merger. It is demonstrated that the above scenario can be supported by our fit to the late-time observational data, where a mass of ∼10−3 M ⊙ 56Ni is involved in the ejecta of a mass of ∼0.1 M ⊙. Particularly, the magnetar parameters required by the fit are consistent with those derived from the early X-ray observation.

The Very Early Soft X-Ray Plateau of GRB 230307A: Signature of an Evolving Radiative Efficiency in Magnetar Wind Dissipation?

Very recently, a particularly long gamma-ray burst (GRB) 230307A was reported and proposed to originate from a compact binary merger based on its host galaxy property, kilonova, and heavy elements. More intriguingly, a very early plateau followed by a rapid decline in the soft X-ray band was detected in its light curve by the Lobster Eye Imager for Astronomy, indicating strong evidence of the existence of a magnetar as the merger product. This Letter explores the magnetar wind internal gradual magnetic dissipation model, in which the radiative efficiency evolves over time, and successfully fits it to the observed data. Our results reinforce the notion that the X-ray plateau serves as a powerful indicator of a magnetar and imply that an evolving efficiency is likely to be a common feature in X-ray plateaus of GRB afterglows. In addition, we also discuss the explanations for the prompt emission, GRB afterglows, as well as kilonova, and predict possible kilonova afterglows in a magnetar central engine.

Gustav Peter Bucky: An Engineer in the Service of Health.

This history page in the series "Leaders in MSK radiology" is dedicated to the memory and achievements of the German radiologist Gustav Peter Bucky who invented the Bucky diaphragm grids. He wanted to become an engineer but bowed to his parents' wishes and went to medical school. By using his technical skills, he made revolutionary contributions to the early X-ray technique.

A prospective study on lung parenchymal changes in ingestional poisoning

Abstract Introduction:The ingestion of poison constitutes a critical medical emergency necessitating immediate attention in the emergency department. Respiratory symptoms associated with ingested poisons may manifest through aspiration, cardiopulmonary effects, or direct lung toxicity resulting from alveolar epithelium injury. In the emergency setting, chest imaging, including chest radiographs and CT scans, is commonly employed to assess such symptoms. This study aims to observe and document radiological changes in lung parenchyma among cases of ingestional poisoning admitted to GGH Kakinada. Material and Methods : A prospective observational study was conducted, encompassing cases of ingestional poisoning admitted to GGH Kakinada from January 1st, 2023, to June 1st, 2023. Results: Our findings revealed a predominance of males (71.2%), with the most common age group being 31-40 years (36.6%). Paraquat emerged as the most frequently consumed poison (39.39%). Radiological changes were most prevalent in paraquat poisoning cases (66.67%), and the mortality rate was 39.39%. Conclusion: Paraquat poisoning demonstrates substantial and delayed lung involvement, likely linked to aspiration. All cases resulted in mortality. Early chest X-ray assessment is vital in the emergency department for prompt detection and intervention, anticipating respiratory symptoms in patients with radiological changes.

Assessing Acetabular Index Angle in Infants: A Deep Learning-Based Novel Approach.

Developmental dysplasia of the hip (DDH) is a disorder characterized by abnormal hip development that frequently manifests in infancy and early childhood. Preventing DDH from occurring relies on a timely and accurate diagnosis, which requires careful assessment by medical specialists during early X-ray scans. However, this process can be challenging for medical personnel to achieve without proper training. To address this challenge, we propose a computational framework to detect DDH in pelvic X-ray imaging of infants that utilizes a pipelined deep learning-based technique consisting of two stages: instance segmentation and keypoint detection models to measure acetabular index angle and assess DDH affliction in the presented case. The main aim of this process is to provide an objective and unified approach to DDH diagnosis. The model achieved an average pixel error of 2.862 ± 2.392 and an error range of 2.402 ± 1.963° for the acetabular angle measurement relative to the ground truth annotation. Ultimately, the deep-learning model will be integrated into the fully developed mobile application to make it easily accessible for medical specialists to test and evaluate. This will reduce the burden on medical specialists while providing an accurate and explainable DDH diagnosis for infants, thereby increasing their chances of successful treatment and recovery.

Partial proton ordering during phase transition in Friedel's salt

Friedel's salt, also known as Cl-Hydrocalumite, (Ca2[Al(OH)6]· Cl·2H2O), is one of the calcium aluminates phases (AFm phases). It can accommodate radioactive chlorine isotopes, serving as a potential material in radioactive waste applications. Earlier X-Ray diffraction and nuclear magnetic resonance (NMR) experiments demonstrated the existence of the first-order phase transition between 303 K and 313 K. The phase transition involves an orientational ordering of water molecules while lowering the temperature. However, such behavior was not properly reproduced in computer simulations using classical molecular dynamics. Here we apply density functional theory and ab initio molecular dynamics to study structural properties and rotational dynamics of water molecules in the interlayer space of Cl-AFm. The transition is characterized by the partial proton ordering in the low-temperature phase, which was not previously observed in experiments and computer simulations.

Magnetar Central Engines in Gamma-Ray Bursts Follow the Universal Relation of Accreting Magnetic Stars

Gamma-ray bursts (GRBs), both long and short, are explosive events whose inner engine is generally expected to be a black hole or a highly magnetic neutron star (magnetar) accreting high-density matter. Recognizing the nature of GRB central engines, and in particular the formation of neutron stars (NSs), is of high astrophysical significance. A possible signature of NSs in GRBs is the presence of a plateau in the early X-ray afterglow. Here we carefully select a subset of long and short GRBs with a clear plateau, and look for an additional NS signature in their prompt emission, namely a transition between the accretion and propeller phases in analogy with accreting, magnetic compact objects in other astrophysical sources. We estimate from the prompt emission the minimum accretion luminosity below which the propeller mechanism sets in, and the NS magnetic field and spin period from the plateau. We demonstrate that these three quantities obey the same universal relation in GRBs as in other accreting compact objects switching from accretion to propeller. This relation provides also an estimate of the radiative efficiency of GRBs, which we find to be several times lower than radiatively efficient accretion in X-ray binaries and in agreement with theoretical expectations. These results provide additional support to the idea that at least some GRBs are powered by magnetars surrounded by an accretion disk.

A Swift Response to Newly Discovered, Nearby Transients

The Neil Gehrels Swift Observatory has proven to be an extraordinary supernova (SN) observatory. The clearest application of Swift’s unique strengths is obtaining very early UV and X-ray data of young SNe, which enables robust constraints on their progenitor systems. As part of a year-long Swift Guest Investigator Key Project, we initiated a follow-up program to rapidly observe all of the nearest (distance < 35 Mpc or roughly z < 0.008) extragalactic transients without waiting for them to be spectroscopically classified as supernovae. Among the possible results were to measure any UV-bright radiative cooling following the shock breakout from core-collapse SNe and shock emission from the interaction of thermonuclear Type Ia SNe with a non-degenerate companion. Just as importantly, uniformly following up and analyzing a significant sample can constrain the fraction of events for which the shock emission is not seen. Here we present the UV and X-ray measurements performed during our campaign. Our sample of 24 observed triggers included three SNe Ia, six SNe II, three stripped-envelope, core-collapse SNe, five galactic transients, three extragalactic SN imposters, and four unconfirmed transients. For our sample, the median delay time from the discovery image to the first Swift image was 1.45 days. We tabulate the X-ray upper limits and find they are sufficiently deep to have detected objects as X-ray luminous as GRB060218/SN2006aj. Other X-ray-detected SNe such as SNe 2006bp, 2008D, and 2011dh would have been detectable in some of the observations. We highlight the spectroscopically classified Type II SN 2018hna with UV-optical light curves indicating a luminosity and flux evolution very similar to SN 1987A.

GRB 200829A: External-shock Origin of the Very Early Prompt Emission?

Long-duration GRB 200829A was detected by Fermi-GBM and Swift-BAT/XRT, and then rapidly observed by other ground-based telescopes. It has a weak γ-ray emission in the very early phase and is followed by a bright spiky γ-ray emission pulse. The radiation spectrum of the very early emission is best fitted by a power-law function with index ∼−1.7. However, the bright spiky γ-ray pulse, especially the time around the peak, exhibits a distinct two-component radiation spectrum, i.e., Band function combined with a blackbody radiation spectrum. We infer the photospheric properties and reveal a medium magnetization at a photospheric position by adopting the initial size of the outflow as r 0 = 109 cm. It implies that the Band component in this pulse may be formed during the dissipation of the magnetic field. The power-law radiation spectra found in the very early prompt emission may imply the external-shock origination of this phase. Then, we perform the Markov Chain Monte Carlo method fitting on the light curves of this burst, where the jet corresponding to the γ-ray pulse at around 20 s is used to refresh the external shock. It is shown that the light curves of the very early phase and X-ray afterglow after 40 s, involving the X-ray bump at around 100 s, can be well modeled in the external-shock scenario. For the obtained initial outflow, we estimate the minimum magnetization factor of the jet based on the fact that the photospheric emission of this jet is missed in the very early phase.

Investigating Time Variability of X-Ray Absorption in Swift GRBs

The existence of excess absorption in the X-ray spectra of GRBs is well known, but the primary location of the absorbing material is still uncertain. To gain more knowledge about this, we have performed a time-resolved analysis of the X-ray spectra of 199 GRBs observed by the Swift X-ray telescope, searching for evidence of a decreasing column density () that would indicate that the GRBs are ionizing matter in their surroundings. We structured the analysis as Bayesian inference and used an absorbed power law as our baseline model. We also explored alternative spectral models in cases where decreasing absorption was inferred. The analysis reveals seven GRBs that show signs of a decrease in , but we note that alternative models for the spectral evolution cannot be ruled out. We conclude that the excess absorption in the vast majority of GRBs must originate on large scales of the host galaxies and/or in the intergalactic medium. Our results also imply that an evolving column density is unlikely to affect the spectral analysis of the early X-ray spectra of GRBs. In line with this, we show that estimating the total from early Swift data in Window Timing mode reveals the same increasing trend with redshift as previous results based on data taken at later times, but with tighter constraints.

Low-frequency Gravitational-wave Memories from Gamma-Ray Burst Afterglows with Energy Injections

Ultrarelativistic gamma-ray burst (GRB) jets are strong gravitational-wave (GW) sources with memory-type signals. The plateau (or shallow decay) phases driven by the energy injection may appear in the early X-ray afterglows of GRBs. In this paper, we investigate GW signals as well as X-ray afterglow emissions in the framework of GRB jets with energy injections, and both short- and long-duration GRBs are considered. We find that, regardless of the case, and because of the antibeaming and time delay effects, a rising slope that emerges in the waveform of the GW signal, due to the energy injection, lags far behind the energy ejection, and the typical frequencies of the characteristic amplitudes fall within a low-frequency region of ∼10−4–10−6 Hz; we also consider that the GW memories triggered by the GRB jets with energy injection have previously not been accounted for and that nearby GRBs with strong energy injections may disturb the measurement of the stochastic GW background. Such GW memory detection would provide a direct test for models of energy injection in the scenario of GRB jets.

Effects of X-ray application on infertility in new-born rats

In this study, the effect of early X-ray exposure on infertility was investigated by creating a newborn model with rats. Fifteen Pregnant rats were divided into five groups. After birth, the study was continued with 12 babies (6 males, 6 females) rat in each group. Different amounts of X-rays were applied to the experimental groups. At the end of the experiment, there was found that testosterone levels decreased in all experimental groups compared to the control group (P 0.05). When the experimental groups were compared to the control group, there was a decrease in the number of spermatogoniums from all the experimental groups. The decrease in group II, group III and group IV was found to be statistically significant (P 0.05). As a result, exposure to X-rays in new-borns and premature babies; It was observed that it caused disruption of caspase signaling in gonad organs, a serious decrease in hormonal activity, a significant decrease in spermatogonia number and a decrease in the number of primordial follicles. Considering these results, it can be predicted that exposure to X-rays in the neonatal period, especially in the premature period, may lead to infertility in later life.

Synchrotron self-compton emission in the two-component jet model for gamma-ray bursts

Gamma-ray bursts (GRBs) are intense bursts of high-energy photons (prompt emissions) caused by relativistic jets. After the emissions, multi-wavelength afterglows, from radio to very-high-energy (VHE) gamma-ray, last for more than a few days. In the past three years, the VHE gamma-ray photons from four GRBs (GRBs 180720B, 190114C, 190829A and 201216C) were detected by ground-based Imaging Atmospheric Cherenkov Telescopes, such as the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes and the High Energy Stereoscopic System (H.E.S.S.). One of them, GRB 190829A, had some peculiar features of showing achromatic peaks in X-ray and optical bands at 1.4×103 s and being classified as low-luminosity GRBs. Previously, we proposed a two-component jet model, which has ‘narrow jet’ with a small initial opening half-angle θ0=0.015 rad and large bulk Lorentz factor Γ0=350, and ‘wide jet’ with θ0=0.1 rad and Γ0=20. The narrow jet explained the early X-ray and optical emissions and apparently small isotropic gamma-ray energy and peak energy in the off-axis viewing case. Furthermore, the late X-ray and radio (1.3 and 15.5 GHz) afterglows were emitted from the wide jet. Here, we calculate the VHE gamma-ray flux by the synchrotron self-Compton (SSC) emission. The multi-wavelength afterglows of GRB 190829A including the VHE gamma-ray emission are well explained by our two-component jet model. The afterglow emissions from our two-component jet are also consistent with the observational results of GRBs 180720B, 190114C and 201216C, when the jets are viewed on-axis. Furthermore, we discuss the detectability of off-axis orphan afterglows by the Cherenkov Telescope Array (CTA).

A long-duration gamma-ray burst with a peculiar origin.

It is generally believed that long-duration gamma-ray bursts (GRBs) are associated with massive star core collapse1, whereas short-duration GRBs are associated with mergers of compact star binaries2. However, growing observations3-6 have suggested that oddball GRBs do exist, and several criteria (prompt emission properties, supernova/kilonova associations and host galaxy properties) rather than burst duration only are needed to classify GRBs physically7. A previously reported long-duration burst, GRB 060614 (ref. 3), could be viewed as a short GRB with extended emission if it were observed at a larger distance8 and was associated with a kilonova-like feature9. As a result, it belongs to the type I (compact star merger) GRB category and is probably of binary neutron star (NS) merger origin. Here we report a peculiar long-duration burst, GRB 211211A, whose prompt emission properties in many aspects differ from all known type I GRBs, yet its multiband observations suggest a non-massive-star origin. In particular, substantial excess emission in both optical and near-infrared wavelengths has been discovered (see also ref. 10), which resembles kilonova emission, as observed in some type I GRBs. These observations point towards a new progenitor type of GRBs. A scenario invoking a white dwarf (WD)-NS merger with a post-merger magnetar engine provides a self-consistent interpretation for all the observations, including prompt gamma rays, early X-ray afterglow, as well as the engine-fed11,12 kilonova emission.

Photometric and Spectroscopic Observations of GRB 210104A: Bright Reverse-shock Emission and Dense Circumburst Environment

Early afterglow observations of gamma-ray bursts (GRBs) are valuable for exploring the properties of their jets and ambient medium. We report our photometric and spectroscopic observations of GRB 210104A and discuss its jet properties with multiwavelength data. Our spectroscopic observation reveals several absorption features and a tentative redshift of 0.46 is identified. A bright optical flare that has a peak brightness of R = 13 mag at 112 ± 7 s was observed in the R band during 67 ∼ 165 s post the GRB trigger. The flux of the R-band afterglow decays with a slope of α O = − 0.91 ± 0.03 at t > 650 s. The early X-ray afterglow lightcurve is a smooth bump, and it decays with a slope of α X = −1.18 ± 0.01 at late epoch. Our joint spectral fit to the optical-X-ray afterglows during (1.1–1.3) × 104 s yields a photon index ΓO,X = −1.82 ± 0.04. The derived host galaxy extinction is A R = 0.87. Attributing the early optical flare to the reverse-shock (RS) emission and the late optical-X-ray emission to the forward shock emission, the optical and X-ray lightcurves at t < 3 × 104 s can be well fit adopting a Markov Chain Monte Carlo algorithm. Comparing the properties of GRB 210104A with other GRBs that have detection of bright RS emission, we show that its jet is mildly magnetized (R B = 28), with high radiation efficiency (77%), is subenergetic (E k,iso = 4.5 × 1051 erg), and moderately relativistic (Γ0 ∼ 35) in a density medium (n 0 ∼ 417 cm−3). It follows the tight L γ,iso–E p,z–Γ0 relation as with typical GRBs.