The delay time of gravitational wave – gamma-ray burst associations

The first gravitational wave (GW) – gamma-ray burst (GRB) association, GW170817/GRB 170817A, had an offset in time, with the GRB trigger time delayed by ~1.7 s with respect to the merger time of the GW signal. We generally discuss the astrophysical origin of the delay time, Δt, of GW-GRB associations within the context of compact binary coalescence (CBC) – short GRB (sGRB) associations and GW burst – long GRB (lGRB) associations. In general, the delay time should include three terms, the time to launch a clean (relativistic) jet, Δt_jet; the time for the jet to break out from the surrounding medium, Δt_bo; and the time for the jet to reach the energy dissipation and GRB emission site, Δt_GRB. For CBC-sGRB associations, Δtjet and Δt_bo are correlated, and the final delay can be from 10 ms to a few seconds. For GWB-lGRB associations, Δt_jet and Δt_bo are independent. The latter is at least ~10 s, so that Δt of these associations is at least this long. For certain jet launching mechanisms of lGRBs, Δt can be minutes or even hours long due to the extended engine waiting time to launch a jet. We discuss the cases of GW170817/GRB 170817A and GW150914/GW150914-GBM within this theoretical framework and suggest that the delay times of future GW/GRB associations will shed light into the jet launching mechanisms of GRBs.     

Analysis of excited quark propagator effects on neutron charge form factor

The European Physical Journal A - The first neutron star (NS) merger observed by advanced LIGO and Virgo, GW170817, and its fireworks of electromagnetic counterparts across the entire...     

Comprehension of Jet Physics from the Analysis of the Gamma-Ray Burst Afterglow Parameter Distributions

The discovery of a short gamma-ray burst (GRB), GRB170817A, in association with a gravitational wave (GW) and a bright kilonova started a new era in the high-energy astrophysics. The observation of GRB170817A and more recently, GRB200826A and GRB211211A, a short and a long burst, respectively, with a possible kilonova, reinforce the concern about new ways of classification. For this reason, a new machine learning technique is applied to Swift-BAT data, searching for morphological similarities in the light curves. The resulting map is characterized by two distinct groups, although still correlated with standard T90 duration. Since a jet viewed off-axis could explain the emission from GRB170817A, the modeling of this kind of sources is of great importance. A public code called JetFit, based on the “boosted fireball” model, is applied to fit Swift-XRT afterglow light curves of short and long GRBs, with known red-shift, from 2005 to 2021. JetFit does not model the flaring activity. For this purpose, a new technique to remove the time flaring phases, is developed. This analysis provides a comprehensive study of the prompt and of the afterglow phase, trough the study of the best-fit parameters.     

Overview to the Hard X-ray Modulation Telescope (Insight-HXMT) Satellite

As China's first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band(1-250 ke V) slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 Me V. It was designed to perform pointing, scanning and gamma-ray burst(GRB)observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed.Here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and some preliminary results.     

Search for Electron Neutrinos from Gravitational Wave Events at the Baksan Underground Scintillation Telescope

In the data obtained at the Baksan underground scintillation telescope (BUST), electron neutrinos and antineutrinos with energies above 21 MeV have been sought in coincidence with the GW150914, GW151226, GW170104, GW170608, GW170814, and GW170817 gravitational wave events. No neutrino signals from gravitational wave events have been detected in the interval of ±500 s at the Baksan underground scintillation telescope. Bounds on the fluxes of low-energy electron neutrinos and antineutrinos from astrophysical sources of gravitational bursts have been obtained.     

Cosmology with Gravitational Waves: A Review

Standard sirens have been the central paradigm in gravitational-wave cosmology so far. From the gravitational wave signature of compact star binaries, it is possible to measure the luminosity distance of the source directly, and if additional information on the source redshift is provided, a measurement of the cosmological expansion can be performed. This review article discusses several methodologies that have been proposed to use gravitational waves for cosmological studies. Methods that use only gravitational-wave signals and methods that use gravitational waves in conjunction with additional observations such as electromagnetic counterparts and galaxy catalogs will be discussed. The review also discusses the most recent results on gravitational-wave cosmology, starting from the binary neutron star merger GW170817 and its electromagnetic counterpart and finishing with the population of binary black holes, observed with the third Gravitational-wave Transient Catalog GWTC–3.     

The High Energy X-ray telescope (HE) onboard the Insight-HXMT astronomy satellite

The Insight-Hard X-ray Modulation Telescope(Insight-HXMT) is a broadband X-ray and γ-ray(1-3000 ke V) astronomy satellite. One of its three main telescopes is the High Energy X-ray telescope(HE). The main detector plane of HE comprises 18 Na I(Tl)/Cs I(Na) phoswich detectors, where Na I(Tl) is used as the primary detector to measure ~ 20-250 ke V photons incident from the field of view(FOV) defined by collimators, and Cs I(Na) is used as the active shielding detector to Na I(Tl) by pulse shape discrimination. Additionally, Cs I(Na) is used as an omnidirectional γ-ray monitor. The HE collimators have a diverse FOV,i.e. 1.1°×5.7°(15 units), 5.7°×5.7°(2 units), and blocked(1 unit). Therefore, the combined FOV of HE is approximately5.7°×5.7°. Each HE detector has a diameter of 190 mm resulting in a total geometrical area of approximately 5100 cm2, and the energy resolution is ~15% at 60 ke V. For each recorded X-ray event by HE, the timing accuracy is less than 10 μs and the deadtime is less than 10 μs. HE is used for observing spectra and temporal variability of X-ray sources in the 20-250 ke V band either by pointing observations for known sources or scanning observations to unveil new sources. Additionally, HE is used for monitoring the γ-ray burst in 0.2-3 Me V band. This paper not only presents the design and performance of HE instruments but also reports results of the on-ground calibration experiments.     

The possible electromagnetic counterparts of the first high-probability NSBH merger LIGO/Virgo S190814bv

LIGO/Virgo S190814 bv is the first high-probability neutron star–black hole(NSBH) merger candidate, whose gravitational waves(GWs) triggered LIGO/Virgo detectors at21:10:39.012957 UT, 14 August 2019. It has a probability 99% of being an NSBH merger,with a low false alarm rate(FAR) of one per 1.559 e+25 years. For an NSBH merger,electromagnetic counterparts(especially short gamma-ray bursts(GRBs)) are generally expected. However, no electromagnetic counterpart has been found in the extensive follow-up observing campaign. In the present work, we propose a novel explanation for this null result. In our scenario, LIGO/Virgo S190814 bv is just a GW mirror image of the real NSBH merger which should have been detected before 14 September 2015, but at that time we had no ability to detect its GW signals. The electromagnetic counterparts associated with the real NSBH merger should be found in the archive data before 14 September 2015. In this work, we indeed find nine short GRBs that are possibly electromagnetic counterparts.     

Implication of GW170817 for Cosmological Bounces

The detection of GW170817 and its electromagnetic counterpart has revealed the speed of gravitational waves coincides with the speed of light, $c_{T}=1$. Inspired by the possibility that the physics implied by GW170817 might be related with that for the primordial universe, we construct the spatially flat stable (throughout the whole evolution) nonsingular bounce models in the beyond Horndeski theory with $c_{T}=1$ and in the degenerate higher-order scalar-tensor (DHOST) theory with $c_{T}=1$, respectively. Though it constricts the space of viable models, the constraint of $c_{T}=1$ makes the procedure of building models simpler.     

Low-energy gamma-ray sources observed by the MISO telescope

Summary The MISO telescope is a gamma-ray detector operating in the (0.1÷20) MeV energy range. This instrument was flown success-fully from Palestine, Texas (U.S.A.) in May 1977, October 1978, September 1979 and May 1980. During the four flights, the telescope observed a number of galactic and extragalactic sources. The Crab Nebula was detected in 1980 and its spectrum was measured up to 2 MeV. Cygnus X-1 was observed in 1979 and 1980 and was found to be in different hard X-ray states on each occasion: in a superlow state in 1979 and in a low state in 1980. The COS-B high-energy (E>50 MeV) gamma-ray sources CG 135+1 (1978) and CG 195+4 (1978) were also observed by the same instrument. From the region containing CG 135+1 a 5σ excess was measured in the counting rate of the telescope above 120 keV. No statistically significant low-energy gamma-ray flux was detected from CG 195+4. The Seyfert galaxies NCG 4151 (1977, 1979, 1980), and MCG 8-11-11 (1979), the BL LAC object MK 501 (1979) and the ?peculiar? galaxy NGC 1275 (1979) were also searched for gamma-ray emission. The data on NGC 4151 and MCG 8-11-11 are consistent with power law spectra having photon indices α∼1 in the (0.1÷3) MeV energy range. Above this energy, the MISO and SAS-2/COS-B measurements require spectral breaks to α≥3. Upper limits were obtained on the emission from both MK 501 and NGC 1275. Paper presented at the 2° Convegno Nazionale di Fisica Cosmica, held at L'Aquila, 29 May–2 June 1984.     

快重离子辐照引起Ni/SiO2界面原子混合及相变研究

在室温下用308 MeV的Xe离子和853 MeV的Pb离子辐照Ni/SiO2样品, 用卢瑟福背散射和X射线衍射技术对样品进行了分析。 通过分析Ni/SiO2样品中元素成分分布和结构随离子辐照剂量和电子能损的变化, 探索了离子辐照在Ni/SiO2样品中引起的界面原子混合与结构相变现象。 实验结果显示, Xe和Pb离子辐照均能引起明显的Ni原子向SiO2基体的扩散并导致界面附近Ni, Si和O原子的混合。 实验观测到低剂量Xe离子辐照可产生NiSi2相, 而高剂量Xe离子辐照则导致了Ni3Si和NiO相的形成。 根据热峰模型, Ni原子的扩散和新相的形成可能由沿离子入射路径强电子激发引起的瞬间热峰过程驱动。Ni/SiO2 interface were irradiated at room temperature with 308 MeV Xe ions to 1×1012, 5×1012 Xe/cm2 and 853 MeV Pb ions to 5×1011 Pb/cm2, respectively. These samples were analyzed using Rutherford Backscattering Spectrometry (RBS) and X ray diffraction spectroscopy (XRD), from which the intermixing and phase change were investigated. The obtained results show that both Xe and Pb ions could induce diffusion of Ni atoms to SiO2 substrates and result in intermixing of Ni with SiO2. Furthermore, 1.0×1012 Xe/cm2 irradiation induced the formation of NiSi2 and 5.0×1012 Xe/cm2 irradiation created Ni3Si and NiO phases. The diffusion of Ni atoms and the formation of new phase may be driven by a transient thermal spike process induced by the intense electronic energy loss along the incident ion path.     

Afterglow from GRB 070610/Swift J195509.6+261406: An explanation using the fireball model

GRB 070610, which is also named Swift J195509.6+261406, is a peculiar Galactic transient with significant variability on short timescales in both X-ray and optical light curves. One possible explanation is that GRB 070610/Swift J195509.6 + 261406 is a soft gamma-ray repeater (SGR) in our Galaxy. Here, we use the fireball model, which is usually recognized as the standard model of gamma-ray burst (GRB) afterglows, and the energy injection hypothesis to interpret the X-ray and optical afterglow light curves of GRB 070610/Swift J195509.6 + 261406. It is found that the model is generally consistent with observations.

     

A black hole preying on the star for a gamma-ray burst of GRB080503: Evidence for the second event in this new class

In this paper, we critically assess GRB080503, a short gamma-ray burst with very bright extended emission (about 30 times the gamma-ray fluence of the initial spike). The light curve of the prompt γ-ray emission of GRB080503 resembles that of GRB 060614 which has been suggested to be due to an event from an intermediate mass black hole (IMBH) preying on a star. We therefore propose that GRB080503 is also due to a similar event; the mass of the IMBH is estimated to be about 4.6×10⁴ solar masses, and the engulfed star had about the same mass and size as the Sun. We also estimate that the total burst energy is about 7.67 × 10⁵⁰ ergs.

     

Gamma-ray bursts at high and very high energies

Gamma-Ray Bursts (GRBs) are extra-galactic and extremely energetic transient emissions of gamma rays, which are thought to be associated with the death of massive stars or the merger of compact objects in binary systems. Their huge luminosities involve the presence of a newborn stellar-mass black hole emitting a relativistic collimated outflow, which accelerates particles and produces non-thermal emissions from the radio domain to the highest energies. In this article, I review recent progresses in the understanding of GRB jet physics above 100 MeV, based on Fermi observations of bright GRBs. I discuss the physical implications of these observations and their impact on GRB modeling, and I present some prospects for GRB observation at very high energies in the near future.     

Search for electron-antineutrinos associated with gravitational-wave events GW150914, GW151012, GW151226, GW170104, GW170608, GW170814, and GW170817 at Daya Bay

The establishment of a possible connection between neutrino emission and gravitational-wave (GW) bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge. In the Daya Bay experiment, using the data collected from December 2011 to August 2017, a search was performed for electron-antineutrino signals that coincided with detected GW events, including GW150914, GW151012, GW151226, GW170104, GW170608, GW170814, and GW170817. We used three time windows of ±10, ±500, and ±1000 s relative to the occurrence of the GW events and a neutrino energy range of 1.8 to 100 MeV to search for correlated neutrino candidates. The detected electron-antineutrino candidates were consistent with the expected background rates for all the three time windows. Assuming monochromatic spectra, we found upper limits (90% confidence level) of the electron-antineutrino fluence of (1.13 ? 2.44)×10¹¹ cm^?2 at 5 MeV to 8.0×10⁷ cm^?2 at 100 MeV for the three time windows. Under the assumption of a Fermi-Dirac spectrum, the upper limits were found to be (5.4 ? 7.0)×10⁹ cm^?2 for the three time windows.     

Very high-frequency gravitational waves from magnetars and gamma-ray bursts

Extremely powerful astrophysical electromagnetic(EM) systems could be possible sources of highfrequency gravitational waves(HFGWs). Here, based on properties of magnetars and gamma-ray bursts(GRBs), we address "Gamma-HFGWs"(with very high-frequency around 10~(20) Hz) caused by ultra-strong EM radiation(in the radiation-dominated phase of GRB fireballs) interacting with super-high magnetar surface magnetic fields(～10~(11) T).By certain parameters of distance and power, the Gamma-HFGWs would have far field energy density ?gw around10~(-6), and they would cause perturbed signal EM waves of～10~(-20) W/m~2 in a proposed HFGW detection system based on the EM response to GWs. Specially, Gamma-HFGWs would possess distinctive envelopes with characteristic shapes depending on the particular structures of surface magnetic fields of magnetars, which could be exclusive features helpful to distinguish them from background noise. Results obtained suggest that magnetars could be involved in possible astrophysical EM sources of GWs in the very high-frequency band, and Gamma-HFGWs could be potential targets for observations in the future.     

紧凑型单能伽马射线源

基于高亮度电子束与超短强激光相互作用的逆康普顿散射X/γ射线源具有单色性好、能量可调、偏振可控等特点,在核安全及核安保领域具有广泛的应用前景。清华大学将研制国际上首套能量达MeV的紧凑准单能伽马源装置并开展包括先进辐射成像、基于核共振荧光的物质分析检测等应用工作。给出该光源设计方案,以及针对其关键性能指标进行的优化及光源最终性能指标。目前已完成光源的设计,正在进行部件的加工采购,预计将于2023年启动装置的安装调试工作,于2025年完成项目的调试和验收。     

Fe/Nb多层膜中离子辐照效应研究(英文)

〗采用磁控溅射技术在Si衬底上沉积Si/\[Fe(10 nm)/Nb(4 nm)/Fe(4 nm)/Nb(4 nm)\]2/ \[Fe(4 nm)/Nb(4 nm)\]4多层膜。 用2 MeV的 Xe离子在室温下辐照多层膜。采用俄歇深度剖析、X射线衍射和振动样品磁强计分析辐照引起的多层膜元素分布、 结构及磁性变化。AES深度剖析谱显示当辐照注量达到1.0×1014 ions/cm2时, 多层膜界面两侧元素开始混合; 当辐照注量达到2.0×1016ions/cm2时, 多层膜层状结构消失, Fe层与Nb层几乎完全混合。XRD谱显示, 当辐照注量达到1.0×1014ions/cm2时, Nb的衍射峰和Fe的各衍射峰的峰位相对于标准卡片向小角方向偏移, 这说明辐照引起Nb基和Fe基FeNb固溶体相的形成;当辐照注量大于1.0×1015 ions/cm2时, 辐照引起非晶相的出现。 VSM测试显示,多层膜的磁性随着结构的变化而变化。 在此实验基础上, 对离子辐照引起界面混合现象的机理进行了探讨。The behavior of the metallic multilayers of Si/\[Fe(10 nm)/Nb(4 nm)/Fe(4 nm)/ Nb(4 nm)\]2/\[Fe(4 nm)/Nb(4 nm)\]4 under 2 MeV Xe ion irradiation has been investigated by depth profile analysis of Auger electron spectroscopy,X ray diffraction and vibrating sample magnetometer. The obtained experimental results show that the inter mixing between Fe and Nb layers occurs in the 1.0×1014 ions/cm2 irradiated multilayer sample which results in the formation of Nb based and Fe based FeNb solid solution. For the samples irradiated to fluence larger than 1.0×1014 ions/cm2, amorphisation is observed, and moreover, the layered structure of the multilayer samples is broken up completely for the samples under 1.0×1016 or 2.0×1016 ions/cm2 irradiation. Vibrating sample magnetometer measurement also reveals that the magnetization of the samples changes with the evolution of the structure of multilayers. Possible mechanism of the modification in Fe/Nb multilayers induced by Xe ion irradiation is briefly discussed.     

SVOM gamma ray monitor

The space-based multi-band astronomical Variable Object Monitor (SVOM) mission is dedicated to the detection, localization and broad-band study of gamma-ray bursts (GRBs) and other high-energy transient phenomena. The gamma ray monitor (GRM) onboard is designed to observe GRBs up to 5 MeV. With this instrument, one of the key GRB parameters, E _peak, can be easily measured in the hard X-ray band. It can achieve a detection rate of 100 GRBs per year which ensures the scientific output of SVOM.