Synchrotron Radiation Research Articles

Gamma-ray burst spectral-luminosity correlations in the synchrotron scenario

For over two decades, gamma-ray burst (GRB) prompt emission spectra were modeled with smoothly broken power laws (Band function), and a positive and tight correlation between the spectral rest-frame peak energy and the total isotropic-equivalent luminosity was found, constituting the so-called Yonetoku relation. However, more recent studies show that many prompt emission spectra are well described by the synchrotron radiation model, and hence significantly deviate from the Band function. In this work, we test the impact of a more refined spectral model such as an idealized synchrotron spectrum from nonthermal electrons on the Yonetoku relation and its connection with physical parameters. We selected GRBs with measured redshift observed by together with high-energy observations (>30 MeV), and performed a spectral analysis, dividing them in two samples: the single-bin sample, using the light curve peak spectrum of each GRB, and the multiple-bin sample, for which we explored the whole duration of 13 bright bursts with time-resolved spectral analysis. We observed that the of synchrotron spectra in a fast-cooling regime ( is generally larger than the one provided by the Band function. For this reason, we do not find any correlation in our samples except for the GRBs in an intermediate-cooling regime ($1<ratio <3$); namely, where peak and break energies are very close. We instead find in both our samples a new tight correlation between the rest-frame cooling frequency, $ c,z $, and c,z iso These results suggest that, assuming that prompt emission spectra are produced by synchrotron radiation, the physical relation is between $ c,z $ and $L_ iso $. The fit of the Band function to an intrinsic synchrotron spectrum returns peak energy values of $E_ p,z Band c,z $. This may explain why the systematic interpretation of prompt spectra through the Band function returns the $E_ p,z -L_ iso $ relation.

A study of rare earth intermetallide La<sub>0.73</sub>Dy<sub>0.27</sub>Mn<sub>2</sub>Si<sub>2</sub> by Raman spectroscopy, magnetic force microscopy and resonance photoemission spectroscopy

The features of the magnetic microstructure of La0.73Dy0.27Mn2Si2 at 293 K have been visualized by atomic force and magnetic force microscopy. Magnetic force images reveal the presence of low-contrast magnetic domains. The change of Raman spectral characteristics of light scattering in the process of cooling La0.73Dy0.27Mn2Si2 to a temperature of 263 K is experimentally detected. The electronic structure of La0.73Dy0.27Mn2Si2 is investigated by resonance photoemission spectroscopy with the use of the synchrotron radiation. Resonances at 3d and 4d levels of electronic structure show different properties of valence electrons. Using the 3d–4f (M4.5 absorption edge) resonance, the distribution of 4f states of dysprosium in the valence band is determined. Photoemission upon the giant Dy 4d–4f (N4.5 absorption edge) resonance is determined by the contribution of all states in the valence band due to the sudden involvement of the Coulomb interaction. The energies of La and 4f levels of La, the 4f level of Dy, and the 3d level of Mn in the valence band have been determined.

Mechanistic Study of Ethanol Decomposition on Co3O4(111) and Pd/Co3O4(111) Model Catalysts

In many advanced catalytic materials, different functionalities are coupled through spillover of active species across heterogeneous interfaces. In the present work, we consider the coupling of a C−C bond cleavage functionality of palladium with the self‐cleaning functionality of reducible Co3O4. On the model catalysts Pd/Co3O4(111)/Ir(100), we probed the interplay of the two functionalities for the selective decomposition of ethanol. In a systematic study, we compared the decomposition mechanisms of ethanol on Co3O4(111)/Ir(100) and Pd/Co3O4(111)/Ir(100) model catalysts using a variety of analytical techniques including synchrotron radiation photoelectron spectroscopy (SRPES), resonant photoemission spectroscopy (RPES), temperature programmed desorption (TPD), and near ambient pressure X‐ray photoelectron spectroscopy (NAP‐XPS). We found that ethanol decomposes via an ethoxy intermediate yielding acetaldehyde on Co3O4(111)/Ir(100). Remarkably, the spillover of ethanol/ethoxy species on Pd/Co3O4(111)/Ir(100) results in the selective formation of methane, hydrogen, and CO. Additionally, we observed CO2 resulting from the oxidative removal of carbonaceous deposits on Pd nanoparticles via spillover of active oxygen species released by Co3O4(111)/Ir(100) at higher temperatures. The onset of product formation and the product spectrum on both Co3O4(111)/Ir(100) and Pd/Co3O4(111)/Ir(100) depend strongly on the oxidation state of Co3O4. Complete removal of lattice oxygen from Co3O4(111) results in the deposition of large amounts of carbon.

Identifying N Coordination Types of Single‐Atom Catalysts by Spin‐Modulated Luminol Cathodic Electrochemiluminescence

The type of coordinated N atoms in the metal‐N coordination structure is of paramount importance to the catalytic property of carbon‐based metal single‐atom catalysts (SACs). Extended X‐ray absorption fine structure (EXAFS) spectroscopy is a powerful tool for analyzing the coordination environments of SACs. Despite its efficacy, the limited availability of synchrotron light sources and the complexity of data analysis have constrained its broader application in identifying metal‐N coordination types within SACs. In this work, two kind of CoN4 SACs were prepared by varying the N source. Then their electrochemiluminescence (ECL) behavior in the luminol/dissolved oxygen system during cathodic scanning were investigated. In comparison to CoN4(pyridinic N), for which the spin density displays dz2 orbital characteristics, CoN4(pyrrolic N) exhibits dxz orbital features, which was more conducive to the subsequent cleavage of the O‐O bond in O2•‐ to •OH, resulting in the generation of more active intermediates *OH and the promotion of cathodic ECL emission. This work demonstrates that the ECL technique provides a novel method for the rapid identification of Co‐N coordination types and the spin nature of the metal center in CoN4 SACs.

Identifying N Coordination Types of Single-Atom Catalysts by Spin-Modulated Luminol Cathodic Electrochemiluminescence.

The type of coordinated N atoms in the metal-N coordination structure is of paramount importance to the catalytic property of N-modified carbon-based single-atom catalysts (SACs). Extended X-ray absorption fine structure (EXAFS) spectroscopy is a powerful tool for analyzing the coordination environments of SACs. Despite its efficacy, the limited availability of synchrotron light sources and the complexity of data analysis have constrained its broader application in identifying metal-N coordination types within SACs. In this work, two kind of CoN4 SACs, were prepared by varying the N source. Then their electrochemiluminescence (ECL) behavior in the luminol/dissolved oxygen system during cathodic scanning were investigated. In comparison to CoN4(pyridinic N), for which the spin density displays dz2 orbital characteristics, CoN4(pyrrolic N) exhibits dxz orbital features, which was more conducive to the subsequent cleavage of the O-O bond in O2⋅- to ⋅OH, resulting in the generation of more active intermediates *OH and the promotion of cathodic ECL emission. This work demonstrates that the ECL technique provides a novel method for the rapid identification of Co-N coordination types and the spin nature of the metal center in CoN4 SACs.

High-temperature measurements of acetylene VUV absorption cross sections and application to warm exoplanet atmospheres

Most observed exoplanets have high equilibrium temperatures (T$_ eq $ > 500 K). Understanding the chemistry of their atmospheres and interpreting their observations requires the use of chemical kinetic models including photochemistry. The thermal dependence of the vacuum ultraviolet (VUV) absorption cross sections of molecules used in these models is poorly known at high temperatures, leading to uncertainties in the resulting abundance profiles. The aim of our work is to study experimentally the thermal dependence of VUV absorption cross sections of molecules of interest for exoplanet atmospheres and provide accurate data for use in atmospheric models. This study focuses on acetylene (C$_ $H$_ We measured absorption cross sections of C$_ $H$_ $ at seven temperatures ranging from 296 to 773 K recorded in the 115-230 nm spectral domain using VUV spectroscopy and synchrotron radiation. These data were used in our 1D thermo-photochemical model, to assess their impact on the predicted composition of a generic hot Jupiter-like exoplanet atmosphere. The absolute absorption cross sections of C$_ $H$_ $ increase with temperature. This increase is relatively constant from 115 to 185 nm and rises sharply from 185 to 230 nm. The abundance profile of C$_ $H$_ $ calculated using the model shows a slight variation, with a maximum decrease of 40<!PCT!> near 5 times 10$^ $ bar, when using C$_ $H$_ $ absorption cross sections measured at 773 K compared to those at 296 K. This is explained by the absorption, higher in the atmosphere, of the actinic flux from 150 to 230 nm due to the increase in the C$_ $H$_ $ absorption in this spectral range. This change also impacts the abundance profiles of other by-products such as methane (CH$_ $) and ethylene (C$_ $H$_ We present the first experimental measurements of the VUV absorption cross sections of C$_ $H$_ $ at high temperatures. Similar studies of other major species are needed to improve our understanding of exoplanet atmospheres.

Thermal Evolution of Expanded Phases Formed by PIII Nitriding in Super Duplex Steel Investigated by In Situ Synchrotron Radiation

The Plasma Immersion Ion Implantation (PIII) nitriding was used to form a modified layer rich in expanded austenite (γN) and expanded ferrite (αN) phases in super duplex steel. The thermal stability of these phases was investigated through the in situ synchrotron X-ray diffraction. All the surfaces were analyzed by SEM, EDS, and nanoindentation. During the heating stage of the thermal treatments, the crystalline structure of the γN phase expanded thermally up to a temperature of 350 °C and, above this temperature, a reduction in the lattice parameter was observed due to the diffusion of nitrogen into the substrate. During the isothermal heating, the gradual diffusion of nitrogen continued and the lattice parameter of the γN phase decreased. Increasing the treatment temperature from 450 °C to 550 °C, a greater reduction in the lattice parameter of the γN phase occured and the peaks related to the CrN, α, and αN phases became more evident in the diffractograms. This phenomenon is associated with the decomposition of the γN phase into CrN + α + αN. After the heat treatments, the thickness of the modified layers increased and the hardness values close to the surface decreased, according to the diffusion of the nitrogen to the substrate.

Phase composition and crystal structure of alumina-zirconia ceramics with varying LaAl11O18 content

This study investigates the phase composition and structure of alumina-zirconia ceramics containing varying amounts of LaAl11O18 plates. The research addresses the significant influence of lanthanum hexaaluminate on the structural and physical properties of these ceramics, specifically focusing on its effects on crystal lattice parameters and phase volume content. Using synchrotron radiation and the Rietveld refinement method, the influence of lanthanum hexaaluminate content on the parameters of crystal lattices and phase content of the investigated materials were evaluated. Scanning electron microscopy was employed to analyze the grain size, morphology, and distribution within the material matrix. High-purity powders of α-Al2O3, 3Y-ZrO2, and La2O3 were used as initial materials. The materials were obtained by the pressureless sintering techniques in two hours at 1520 °C. A series of materials comprising 50 wt.% ZrO2 and varying percentage (0–15 wt.%) of LaAl11O18 was obtained. The coherent scattering regions of the alumina and zirconia matrix phases remained relatively unchanged in the composites. The coherent scattering regions of lanthanum hexaaluminate increased significantly with its concentration in the materials. The analysis revealed a decrease in alumina grain size with increasing LaAl11O18 content, while the size of the LaAl11O18 plates displayed a consistent increase. The best properties were observed for alumina-zirconia ceramics with the calculated content of lanthanum hexaaluminate of 12 wt.%. The relative density of this material is 95.3±0.3%, the hardness is 1490 Hv, and the indentation fracture resistance is 7.2±0.3 MPaThis study investigates the phase composition and structure of alumina-zirconia ceramics containing varying amounts of LaAl11O18 plates. The research addresses the significant influence of lanthanum hexaaluminate on the structural and physical properties of these ceramics, specifically focusing on its effects on crystal lattice parameters and phase volume content. Using synchrotron radiation and the Rietveld refinement method, the influence of lanthanum hexaaluminate content on the parameters of crystal lattices and phase content of the investigated materials were evaluated. Scanning electron microscopy was employed to analyze the grain size, morphology, and distribution within the material matrix. High-purity powders of α-Al2O3, 3Y-ZrO2, and La2O3 were used as initial materials. The materials were obtained by the pressureless sintering techniques in two hours at 1520 °C. A series of materials comprising 50 wt.% ZrO2 and varying percentage (0–15 wt.%) of LaAl11O18 was obtained. The coherent scattering regions of the alumina and zirconia matrix phases remained relatively unchanged in the composites. The coherent scattering regions of lanthanum hexaaluminate increased significantly with its concentration in the materials. The analysis revealed a decrease in alumina grain size with increasing LaAl11O18 content, while the size of the LaAl11O18 plates displayed a consistent increase. The best properties were observed for alumina-zirconia ceramics with the calculated content of lanthanum hexaaluminate of 12 wt.%. The relative density of this material is 95.3±0.3%, the hardness is 1490 Hv, and the indentation fracture resistance is 7.2±0.3 MPa.m1/2.

Forensic Elemental Analysis of Five Rupee and One Pound Coin with EDXRF Technique

Energy dispersive X-ray Fluorescence (EDXRF) technique using synchrotron radiation has been employed for elemental analysis of one pound and five rupees coins of two different countries- the UK and India. Total number of 12 coins - 4 one pound and 8 five rupees coin were analysed. A Peltier cooled Vortex solid state detector (SII Nano Technology, USA) having energy resolution of 138 eV at 5.96 keV X-rays was employed for the present analysis. A Peltier cooled Vortex solid state detector (SII Nano Technology, USA) having energy resolution of 138 eV at 5.96 keV X-rays was employed for the present analysis. The investigations were carried out to determine the similarities between the elemental composition and structure of coins. The major elements Cu, Ni, Fe, Cr and traces of two elements Mn and Mo were found during analysis. One of the elements i.e. Cu was found as primary major element in most of the coins. Two other elements Fe and Cr are also found as major element in 2 five rupees coins. Fe was generally considered as cheap metal composition in comparison to Cu. Besides these traces of Mo, S, Ca and Si were also observed whose compositional amount found very low (below 1%). The present study confirms the favorable economic conditions of two countries during their minting time. The XRF spectra and graphical representation of elemental concentration also helps to identify the similarities in structure and composition of coins. Results of present analysis of different types of coins are found in good agreement with standard composition and also with each other. The EDXRF analysis shows its effectiveness in forensic science without alteration of precious samples. Forensic analysis of such coins using Synchrotron radiation is very helpful in archeological study.

Studies About Atomic Compositions based on Synchrotron Radiation X- ray Microfluorescence (SR-μXRF) Analysis of Materials (at Micro- and Nano-Scale) Obtained by Sol-Gel Processes

Sol-gel is a wide-spread methodology for low-temperature synthesis of ceramics, nanocomposites and hybrid (inorganic-organic) materials. Ormosil (Organically Modified Silicates) belong to these class of hybrid materials, which have potential uses as optical materials, chemical sensors, catalysts, membranes, self-cleaning coatings. We are especially interested on the application of Synchrotron Radiation X-ray Microfluorescence (SR-μXRF) for the non-destructive analysis of such materials, benefiting of the high intensity obtained from this source of X-rays. SR-μXRF has demonstrated to be a useful analytical tool for qualitative and semi-quantitative determination of Hybrid films containing phosphotungstates ([PW<sub>12</sub>O<sub>40</sub>]<sup>3-</sup>/PWA), in order to determine the local concentration, as also the correlation among elements. For ormosil films, SR-μXRF enabled the qualitative determination of Titanium (Ti) that is heterogeneously distributed, oppositely to the case of Zinc (Zn) and Tungsten (W). For PI-ORMOSIL-PWA films, SR-μXRF maps have shown the heterogeneous distribution of the Silicon (Si) and a quasi-homogenous distribution of Tungsten (W). SR-μXRF results for Silicon (Si) and Tungsten (W) are consistent with the corresponding concentrations obtained by ICP-OES analyses, which were taken as the reference results. For PDMSUr-PWA films, SR-μXRF mapping have shown the heterogenous distribution pattern for Tungsten (W) and the capacity for the identification of Bromine (Br). For these materials NAA analyses were taken as the reference results for Tungsten (W). Furthermore, they are presented the HorRat parameters, in order to estimate approximately the degree of heterogeneity of these materials, which are in agree with the observed in the corresponding mappings obtained by SR-μXRF, giving hints about segregation at surface and at bulk level. HorRat parameters for concentrations obtained by ICP-OES and NAA (bulk analyses) are close to the expected value (2.0), which make possible using as reference values for SR-μXRF results (analyses at surface and medium-bulk levels), due to the non-existence of standards for these hybrid materials (at Micro- and Nano-Scale).

Development of an infrared diagnostic system with multi-spectrum or high frame rate for measuring the synchrotron radiation emitted by runaway electrons on EAST

In order to meet the requirements for high frame rate and synchrotron radiation spectrum of infrared diagnostic systems when studying runaway electron, an infrared diagnostic system with multi-spectrum or high frame rate has been developed and installed on the Experimental Advanced Superconducting Tokamak(EAST) for studying the runaway electrons. It is based on a high frame rate infrared camera with a high-speed rotating filter wheel and an endoscope. The infrared camera can achieve a maximum frame rate of 120 kHz in sub-windowing mode with an image size of 64 × 2. In experiments, effective data has been obtained at a frame rate of 10 kHz and an image size of 64 × 4. This diagnostic system may become a valuable tool for studying the interaction between runaway electrons and magnetohydrodynamic instability in the future. The equipped high-speed rotating filter wheel on the camera can be utilized to capture the synchrotron radiation spectrum of runaway electrons, which has been calibrated using a blackbody furnace. The synchrotron radiation spectrum contains valuable information about runaway electrons and can be one of the important parameters for inferring their accurate distribution function in the future.

Shear Particle Acceleration in Structured Gamma-Ray Burst Jets. I. Physical Origin of the Band Function and Application to GRBs 090926A, 131108A, and 160509A

The radiation physics of gamma-ray bursts (GRBs) remains an open question. Based on the simulation analysis and recent observations, it was proposed that GRB jets are composed of a narrow ultrarelativistic core surrounded by a wide subrelativistic cocoon. We show that emission from the synchrotron radiations and the synchrotron self-Compton (SSC) process of shear-accelerated electrons in the mixed jet-cocoon (MJC) region and internal-shock-accelerated electrons in the jet core is potentially explained the spectral characteristics of the prompt gamma rays. Assuming an exponential-decay velocity profile, the shear flow in the MJC region can accelerate electrons up to γe,max∼104 for injected electrons with γ e,inject = 3 × 102 if its magnetic field strength ( Bcn ) is 100 G and its inner-edge velocity ( βcn,0 ) is 0.9 c. The cooling of these electrons is dominated by the SSC process, and the emission flux peaks at the keV band. In addition, the energy flux of synchrotron radiations of internal-shock-accelerated electrons (γ e = 104 ∼ 105) peaks at around the keV−MeV band, assuming a bulk Lorentz factor of 300, a magnetic field strength of ∼106 G for the jet core. Adding the flux from both the jet core and the MJC region, the total spectral energy distribution illustrates similar characteristics as the broadband observations of GRBs. The bimodal and Band cut spectra observed in GRBs 090926A, 131108A, and 160509A can be well fit with our model. The derived Bcn varies from 54 G to 450 G and βcn,0=0.83∼0.91 c.

Acceleration of Energetic Electrons in Jovian Middle Magnetosphere by Whistler‐Mode Waves

AbstractAn abundant multi‐MeV electron population beyond the orbit of Io is required to explain the intense inner radiation belt (electrons MeV) at Jupiter and its synchrotron radiation. In order to better understand the synergistic effect of radial transport and local wave‐particle interactions driven by whistler‐mode waves on the formation of Jupiter's radiation belt, we perform 3‐D Fokker‐Planck simulations for Jovian energetic electrons with the Versatile Electron Radiation Belt code. An empirical model of Jovian whistler‐mode waves updated with measurements from the Juno extended mission is used to quantify the local acceleration and pitch angle scattering. Resonant cyclotron acceleration by whistler‐mode waves leads to significant enhancement in the intensity of electrons above 1 MeV in the middle magnetosphere. Radial diffusion is capable of transporting MeV electrons accelerated by outer‐belt whistler‐mode waves into the region, where they are further accelerated adiabatically to energies of about 10 MeV.

The Peak Frequency and Luminosity of Synchrotron Emitting Shocks: From Nonrelativistic to Ultrarelativistic Explosions

Synchrotron emission is ubiquitous in explosive astrophysical events—it is a natural byproduct of shocks formed when matter expelled by the explosion collides with ambient material. This emission is well observed in various classes of transients, and is often interpreted within a canonical “equipartition” framework that allows physical properties of the shock to be inferred from the frequency and luminosity at which the observed spectral energy distribution (SED) peaks. This framework has been remarkably successful in explaining observations of radio supernovae. It has also been used for transrelativistic explosions, where the shock velocities approach the speed of light. However, the conventional framework does not incorporate relativistic effects. Neither does it account for thermal electrons, which have been shown to be important for high-velocity shocks. In this paper we describe a revised framework that accounts for these two effects, and is applicable to nonrelativistic, transrelativistic, and ultrarelativistic explosions. We show that accounting for these effects can dramatically change the inferred parameters of high-velocity shocks, and, in particular, that the shock velocity, ambient density, and total energy are overestimated by the conventional nonrelativistic framework. We delineate the phase-space where such modifications are important in terms of observationally measurable parameters. We also find a novel upper limit on the peak synchrotron luminosity of shock-powered transients, which is remarkably consistent with existing observations. Finally, we discuss a prediction of the model—that the SED will qualitatively change as a function of shock velocity—and show that this is broadly consistent with data for representative events (e.g., SN1998bw, AT2018cow, CSS161010, AT2020xnd).

Insights into the Long-term Flaring Events of Blazar PKS 0805-07: A Multiwavelength Analysis Over the Period of 2009–2023

We conducted a comprehensive temporal and spectral study of the FSRQ PKS 0805-07 by using broadband observations from the Fermi-LAT and Swift-XRT/UVOT instruments over the period of MJD 54684-60264. The 3 day binned γ-ray light curve during the active state revealed 11 distinct peak structures with the maximum integral flux (E > 100 MeV) reached (1.56 ± 0.16) × 10−6 photons cm−2 s−1 on MJD 59904.5. The shortest observed γ-ray variability was 2.80 ± 0.77 days. A correlation analysis between the γ-ray spectral index and flux indicated the typical trend of hardening when the source is brighter, commonly observed in blazars. We identified a lag of 121 (+27.21, −3.51) days in the spectral index relative to the flux, within the time interval MJD 59582 to 60112. The Anderson–Darling test and histogram fit rejected the normality of the γ-ray flux distribution and instead suggested a log-normal distribution. To gain insight into the underlying physical processes, we extracted broadband spectra from different time periods in the light curve. The spectral energy distribution during various flux states was well-reproduced using synchrotron, synchrotron-self-Compton, and external-Compton emissions from a broken power-law electron distribution. The seed photons required for the external Compton process are from the IR region. A comparison of the best-fit physical parameters indicated that the variations in different flux states were primarily associated with an increase in the bulk Lorentz factor and magnetic field from low to high flux states.

Conceptual design of TUPI (Timepix4-based Ultra-fast Photon Imaging) detector's hardware

TUPI (Timepix4-based Ultra-fast Photon Imaging) is the new family of direct conversion and vacuum-compatible hybrid detectors under design at Sirius, the Brazilian 4th generation light source. Based on the Timepix4 Application Specific Integrated Circuit (ASIC), it targets different kinds of experiments, such as tomography and spectrometry, and will be used in multiple bioimaging beamlines of Orion, Brazil's Biosafety Level 4 (BSL4) Laboratory project. Also, it will cover a wide energy range (5 to 45 keV) by using different sensors materials (Si, GaAs, CdTe, etc.). Designed in a modular approach to ensure scalability for constructing larger active areas in a compact form, each TUPI module will be composed by a set of 3x side-by-side Timepix4 ASICs to provide a sensitive area of approximately 74×28 mm2 (1344×512 pixels of 55 μm pitch), streaming up to 44 kfps through up to 48×10.24 Gbps optical links directly connected to a Data Acquisition (DAQ) system.

Development of Methods for Controlling the Stability of an Electron Beam on Synchrotron Radiation Sources

Development of Methods for Controlling the Stability of an Electron Beam on Synchrotron Radiation Sources

Temporal and Spectral Analysis of the Unique and Second-brightest Gamma-Ray Burst GRB 230307A: Insights from GECAM and Fermi/GBM Observations

In this study, we present the pulse profile of the unique and the second-brightest gamma-ray burst GRB 230307A, and analyze its temporal behavior using a joint GECAM–Fermi Gamma-ray Burst Monitor (GBM) time-resolved spectral analysis. The utilization of GECAM data is advantageous as it successfully captured significant data during the pileup period of the Fermi/GBM. We investigate the evolution of its flux, photon fluence, photon flux, peak energy, and the corresponding hardness–intensity and hardness–flux correlations. The findings within the first 27 s exhibit consistent patterns reported previously, providing valuable insights for comparing observations with predictions from the synchrotron radiation model invoking an expanding shell. Beyond the initial 27 s, we observe a notable transition in the emitted radiation, attributed to high-latitude emission, influenced by the geometric properties of the shells and the relativistic Doppler effects. By modeling the data within the framework of the large-radius internal shock model, we discuss the required parameters as well as the limitations of the model. We conclude that a more complicated synchrotron emission model is needed to fully describe the observational data of GRB 230307A.

Commissioning and first result of undulator based atomic, molecular, and optical sciences (AMOS) beamline at Indus-2 synchrotron radiation source.

We present a comprehensive overview of the commissioning process and initial results of a synchrotron beamline dedicated to atomic, molecular, and optical sciences at the BL-5 undulator port of the Indus-2 synchrotron facility, Raja Ramanna Center for Advanced Technology, Indore, India. The beamline delivers a photon flux of ∼1012 photons/s with high resolving power (∼10 000) over an energy range of 6-800eV, making it suitable for high-resolution spectroscopy in atomic, molecular, and optical science. The energy tunability from vacuum ultraviolet to soft x-ray (6-800eV) is achieved through a varied line spacing plane grating monochromator with four gratings: very low energy (VLEG), low energy (LEG), medium energy (MEG), and high energy (HEG). These gratings cover ranges of 6-18, 15-45, 42-126, and 90-800eV, respectively. A differential pumping system allows windowless transmission of VUV and soft x-ray photons for gas-phase spectroscopic experiments. The beamline also includes an x-ray absorption spectroscopy (XAS) station for solid samples. To demonstrate efficiency, a spectrum was recorded using all four gratings in the 6-300eV energy range. Standard spectra of Xe and O2 verified the resolution, achieving a resolving power of 7740 with the VLEG, consistent with design specifications. XAS spectra of Cu M, C, and O K-edges were also obtained using MEG and HEG. Details on vacuum level, grating operation, and the first commissioning experiments are presented.

Simulations of the Collision between a Debris Stream and an Outer Dusty Torus: A Possible Channel for Forming a Fast-rise and Long-delay Radio Outburst in Tidal Disruption Events

A geometrically thick dusty torus structure is believed to exist in the nuclear regions of galaxies (especially in active galactic nuclei). The debris stream from a tidal disruption event (TDE) will possibly collide with the dusty torus and produce a transient flare. We perform three-dimensional hydrodynamic simulations to model the dynamical evolution of the interaction between unbound debris and a dusty torus. During the continuous interaction, shocked material will be spilled out from the interaction region and form an outflow. We calculate the temporal evolution of synchrotron emission by assuming that the shock accelerates a fraction of electrons in the outflow into a nonthermal distribution. We find that radio emission from the debris–torus collision generates a steep-rise and slow-decline radio light curve due to the sharp edge and dense gas of the dusty torus, where the radio outburst is delayed relative to the main optical/X-ray outburst by several years or even several tens of years. We apply our model to a TDE that happened in a narrow-line Seyfert I galaxy (PS16dtm), where both the radio spectrum and the light curve can be roughly reproduced. Future high-sensitivity, wide-field-of-view radio surveys have the opportunity to detect more such radio flares.