Gamma-Ray Bursts and Fast Transients: Multi-wavelength Observations and Multi-messenger Signals

The current status of observations and theoretical models of gamma-ray bursts and some other related transients, including ultra-long bursts and tidal disruption events, is reviewed. We consider the impact of multi-wavelength data on the formulation and development of theoretical models for the prompt and afterglow emission including the standard fireball model utilizing internal shocks and external shocks, photospheric emission, the role of the magnetic field and hadronic processes. In addition, we discuss some of the prospects for non-photonic multi-messenger detection and for future instrumentation, and comment on some of the outstanding issues in the field

Exploring the Dynamic X-ray Universe: Scientific Opportunities for the Einstein Probe Mission

Time-domain astrophysics will enter a golden era towards the end of this decade with the advent of major facilities across the electromagnetic spectrum and in the multi-messenger realms of gravitational wave and neutrino. In the soft X-ray regime, the novel micro-pore lobster-eye optics provides a promising technology to realise, for the first time, focusing X-ray optics for wide-angle monitors to achieve a good combination of sensitivity and wide field of view. In this context Einstein Probe, a soft X-ray all-sky monitor mission, was proposed and selected as a candidate mission of priority in the space science programme of the Chinese Academy of Sciences. This paper reviews the most important science developments and key questions in this field towards 2020 and beyond, and how to achieve them technologically. It also introduces the Einstein Probe mission, including its key science goals and mission definition, as well as some of the key technological issues

Geant4 simulations of a wide-angle x-ray focusing telescope

The rapid development of X-ray astronomy has been made possible by widely deploying X-ray focusing telescopes on board many X-ray satellites. Geant4 is a very powerful toolkit for Monte Carlo simulations and has remarkable abilities to model complex geometrical configurations. However, the library of physical processes available in Geant4 lacks a description of the reflection of X-ray photons at a grazing incident angle which is the core physical process in the simulation of X-ray focusing telescopes. The scattering of low-energy charged particles from the mirror surfaces is another noteworthy process which is not yet incorporated into Geant4. Here we describe a Monte Carlo model of a simplified wide-angle X-ray focusing telescope adopting lobster-eye optics and a silicon detector using the Geant4 toolkit. With this model, we simulate the X-ray tracing, proton scattering and background detection. We find that: (1) the effective area obtained using Geant4 is in agreement with that obtained using Q software with an average difference of less than 3%; (2) X-rays are the dominant background source below 10 keV; (3) the sensitivity of the telescope is better by at least one order of magnitude than that of a coded mask telescope with the same physical dimensions; (4) the number of protons passing through the optics and reaching the detector by Firsov scattering is about 2.5 times that of multiple scattering for the lobster-eye telescope

Luminosity-time and luminosity-luminosity correlations for GRB prompt and afterglow plateau emissions

We present an analysis of 123 gamma-ray bursts (GRBs) with known redshifts possessing an afterglow plateau phase. We reveal that La-T∗a correlation between the X-ray luminosity La at the end of the plateau phase and the plateau duration, T∗a, in the GRB rest frame has a power-law slope different, within more than 2σ, from the slope of the prompt Lf-T∗f correlation between the isotropic pulse peak luminosity, Lf, and the pulse duration, T∗f, from the time since the GRB ejection. Analogously, we show differences between the prompt and plateau phases in the energy duration distributions with the afterglow emitted energy being on average 10 per cent of the prompt emission. Moreover, the distribution of prompt pulse versus afterglow spectral indexes does not show any correlation. In the further analysis we demonstrate that the Lpeak–La distribution, where Lpeak is the peak luminosity from the start of the burst, is characterized with a considerably higher Spearman correlation coefficient, ρ = 0.79, than the one involving the averaged prompt luminosity, Lprompt–La, for the same GRB sample, yielding ρ = 0.60. Since some of this correlation could result from the redshift dependences of the luminosities, namely from their cosmological evolution we use the Efron–Petrosian method to reveal the intrinsic nature of this correlation. We find that a substantial part of the correlation is intrinsic. We apply a partial correlation coefficient to the new de-evolved luminosities showing that the intrinsic correlation exists

Qualitative and quantitative characterization of plasma proteins when incorporating traveling wave ion mobility into a liquid chromatography−mass spectrometry workflow for biomarker discovery : use of product ion quantitation as an alternative data analysis tool for label free quantitation

Discovery of protein biomarkers in clinical samples necessitates significant prefractionation prior to liquid chromatography−mass spectrometry (LC−MS) analysis. Integrating traveling wave ion mobility spectrometry (TWIMS) enables in-line gas phase separation which when coupled with nanoflow liquid chromatography and data independent acquisition tandem mass spectrometry, confers significant advantages to the discovery of protein biomarkers by improving separation and inherent sensitivity. Incorporation of TWIMS leads to a packet of concentrated ions which ultimately provides a significant improvement in sensitivity. As a consequence of ion packeting, when present at high concentrations, accurate quantitation of proteins can be affected due to detector saturation effects. Human plasma was analyzed in triplicate using liquid-chromatography data independent acquisition mass spectrometry (LC-DIA-MS) and using liquid-chromatography ion-mobility data independent acquisition mass spectrometry (LC-IM-DIA-MS). The inclusion of TWIMS was assessed for the effect on sample throughput, data integrity, confidence of protein and peptide identification, and dynamic range. The number of identified proteins is significantly increased by an average of 84% while both the precursor and product mass accuracies are maintained between the modalities. Sample dynamic range is also maintained while quantitation is achieved for all but the most abundant proteins by incorporating a novel data interpretation method that allows accurate quantitation to occur. This additional separation is all achieved within a workflow with no discernible deleterious effect on throughput. Consequently, TWIMS greatly enhances proteome coverage and can be reliably used for quantification when using an alternative product ion quantification strategy. Using TWIMS in biomarker discovery in human plasma is thus recommended

THESEUS and Gamma-Ray Bursts: a valuable contribution to the understanding of prompt emission

Recent advances in fitting prompt emission spectra in gamma-ray bursts (GRBs) are boosting our understanding of the still elusive origin of this radiation. These progresses have been possible thanks to a more detailed analysis of the low-energy part ($<$\,100\,keV) of the prompt spectrum, where the spectral shape is sometimes found to deviate from a simple power-law shape. This deviation is well described by a spectral break or, alternatively by the addition of a thermal component. Spectral data extending down to less than 1\,keV are extremely relevant for these studies, but presently they are available only for a small subsample of {\it Swift} GRBs observed by XRT (the X-ray telescope, 0.3-10\,keV) during the prompt emission. The space mission \th\ will allow a systematic study of prompt spectra from 0.3\,keV to several MeV. We show that observations performed by \th\ will allow us to discriminate between different models presently considered for GRB prompt studies, solving the long-standing open issue about the nature of the prompt radiation, with relevant consequences on the location of the emitting region, magnetic field strength and presence of thermal components

The discovery of an evolving dust scattering X-ray halo around GRB 031203

We report the first detection of a time-dependent dust-scattered X-ray halo around a gamma-ray burst (GRB). GRB 031203 was observed by XMM-Newton starting 6 hr after the burst. The halo appeared as concentric ringlike structures centered on the GRB location. The radii of these structures increased with time as t1/2, consistent with small-angle X-ray scattering caused by a large column of dust along the line of sight to a cosmologically distant GRB. The rings are due to dust concentrated in two distinct slabs in the Galaxy located at distances of 880 and 1390 pc, consistent with known Galactic features. The halo brightness implies an initial soft X-ray pulse consistent with the observed GRB

SVOM-MXT optic and telescope testing at PANTER

The Microchannel X-ray Telescope (MXT) for the Space-based multi-band astronomical Variable Objects Monitor (SVOM), a Franco-Chinese mission (CNES/CNSA), is designed for the soft X-ray range (0.2-10 KeV) to observe gamma-ray bursts (GRBs) from the beginning to the afterglow emission. In the past years, the PANTER test facility has been testing the different MXT optics models. Each optic is made up of an array of 5 x 5 Micro Pore Optic (MPO) plates. We characterized the performance of the SVOM optic at different phases: Bread-Board (BB), Qualification Model (QM), Flight Model (FM), and Flight Spare (FS) for the optic followed by the Performance Model (PM) and Flight Model (FM) for the complete telescope fully integrated with the optic, detector, radiator and electronics. For the FM end-to-end test, in October 2021, the goal was to determine the half-energy width (HEW) on-axis and off-axis, and to characterize the flight telescope's energy-dependent efficiency (effective area) under different thermal loads, i.e. different detector and optics temperatures. The final numbers will be presented in a paper in preparation. This paper provides the overview of various activities: setup, metrology and measurement, carried out at the PANTER facility during the development of the SVOM-MXT towards the end-to-end test

A Wide Field Auroral Imager (WFAI) for Low Earth Orbit Missions

A Wide Field Auroral Imager (WFAI) for Low Earth Orbit Mission

Testing and modelling of the SVOM MXT narrow field lobster-eye telescope

The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a French-Chinese space mission to be launched in 2021 with the goal of studying gamma-ray bursts, the most powerful stellar explosions in the Universe. The Microchannel X-ray Telescope (MXT) on-board SVOM, is an X-ray focusing telescope with a detector-limited field of view of ∼1 square° , working in the 0.2-10 keV energy band. The MXT is a narrow-field-optimised lobster eye telescope, designed to promptly detect and accurately locate gamma-ray bursts afterglows. The breadboard MXT optic comprises of an array of square pore micro pore optics (MPOs) which are slumped to a spherical radius of 2 m giving a focal length of 1 m and an intrinsic field of view of ∼6° . We present details of the baseline design and results from the ongoing X-ray tests of the breadboard and structural thermal model MPOs performed at the University of Leicester and at Panter. In addition, we present details of modelling and analysis which reveals the factors that limit the angular resolution, characteristics of the point spread function and the efficiency and collecting area of the currently available MPOs