The Nineteenth-Century Spiral Nebula Whodunit

The discovery of the first spiral nebula was a milestone in the history of astronomy, but the initial observations of it are shrouded in mystery. The discovery came within months of the commissioning of the Third Earl of Rosse’s very large 72-inch optical telescope at Birr Castle in the center of Ireland. Unfortunately, no observing records have survived, and while there is no doubt that the observations took place in the spring of 1845, there is some uncertainty as to whom was actually present when the discovery was made. The construction of the Earl’s telescope (the Leviathan) was a magnificent achievement, since it was entirely of his design, built with his own funds, and constructed by his own workers who were literally taken “from the plough” on his estate. The summer of 1845 saw the first appearance of the Irish Potato Famine of 1845–1848, which would seriously curtail astronomical activity when Lord Rosse’s 72-inch telescope was in prime condition.     

Technical Report: The Crab Synchrotron Nebula

Synchrotron X-ray powder diffraction speeds up the development of new energy-related materials and devices by enabling rapid, real-time data collection in sample environments that emulate true operating conditions.     

羊八井ARGO实验对Crab源灵敏度的研究

应用Monte-Carlo研究给出羊八井ARGO(AstrophysicalRadiationwithGround-basedObservatory)实验的角分辨能力.采用Whipple实验给出的蟹状星云(CrabNebula)TeV能区的微分流强参量,对3种统计显著性的方法进行了比较,研究表明:以信号和本底的似然比为权重的加权方法能够给出最优化的结果.在没有考虑γ/p鉴别能力的条件下,ARGO实验运行一年能够观测到来自Crab源累计超出平均可达18σ显著水平,以5σ为标准,实验可达到小于0.3I_crab的灵敏度.     

Leptonic Origin of TeV Gamma-Ray Emission from Crab Nebula

We study the nonthermal emission of the Crab nebula in the bands from radio to TeV γ-ray on a simplified timedependent injection model. In this model, relativistic electrons in the Crab nebula consists of two components and their injected spectrum is a broken power law with different indices and a break energy. The relativistic electrons emit nonthermal photons through synchrotron and inverse Compton scattering off soft photon fields inside the nebula. The resulting spectrum calculated with the model is well consistent with the observed data ranging from radio to very high energy γ-rays for the Crab nebula, where the emission from radio to medium γ-rays is from electron＇s synchrotron emission, whereas the emission above ～ 100 MeV primarily comes from the inverse Compton scattering of the relativistic electrons on synchrotron photons.     

Performance of LHAASO-WCDA and observation of the Crab Nebula as a standard candle

The first Water Cherenkov detector of the LHAASO experiment (WCDA-1) has been operating since April 2019. The data for the first year have been analyzed to test its performance by observing the Crab Nebula as a standard candle. The WCDA-1 achieves a sensitivity of 65 mCU per year, with a statistical threshold of 5 \begin{document}$\sigma$\end{document}. To accomplish this, a 97.7% cosmic-ray background rejection rate around 1 TeV and 99.8% around 6 TeV with an approximate photon acceptance of 50% is achieved after applying an algorithm to separate gamma-induced showers. The angular resolution is measured using the Crab Nebula as a point source to be approximately 0.45° at 1 TeV and better than 0.2° above 6 TeV, with a pointing accuracy better than 0.05°. These values all match the design specifications. The energy resolution is found to be 33% for gamma rays around 6 TeV. The spectral energy distribution of the Crab Nebula in the range from 500 GeV to 15.8 TeV is measured and found to be in agreement with the results from other TeV gamma ray observatories.     

On the burst activity of the Crab Nebula, as observed by air shower arrays

Recent experiments with the Fermi-LAT and AGILE satellite gamma-ray telescopes, in which bursts of gamma-rays from the Crab Nebula were detected in the energy range of ～100 MeV, have aroused keen interest, if not a sensation. However, data on a possible burst in the Crab Nebula at much higher energies of ～100 TeV were published more than 20 years ago. Characteristics of transient and stationary fluxes of gamma rays from the Crab Nebula in various energy ranges are discussed in this work, and it is shown that the old data obtained at ultra-high energies is reasonably consistent with the latest pattern of the source’s burst activity.     

关于"太阳在银河系中所受引力与到银心距离r的关系"的讨论

讨论了银道面内的引力场强分布和太阳在银河系中所受引力与到银心距离r的关系，指出引力场强g并不是与r的平方成反比，这是由于银河系的大小和形状不能忽略造成的．强调了万有引力定律的适用条件．     

On the calculation of the bremsstrahlung in the region of the plasma frequency

On the basis of the classical theory of radiation produced in incomplete Coulomb interaction, a formula is derived for the coefficient of the bremsstrahlung of fully ionized plasma. In the region of rectilinear approximation a comparison is made with the results of the quantum formula derived from the Born approximation. Furthermore, the influence of dispersion upon the emission coefficient is taken into account; some relations for the region of dispersion are given.     

Dependence of the Intensity of the Spectral Lines and the Composition of the Sample and the Plasma Parameters of the Unipolar Arc

The investigation was made of the dependence of the intensity of Tl, Ga, Mo, Mg, Mn, Sn, Bi, Ni, Zn, Pt and Au spectral lines and the plasma parameters (temperature T, electron concentration n_e, degree of 6 ionnization α) from concentration of lithium additive.     

On the predictability of the positions of the convergence zones in the ocean

The disagreement between the experimental and calculated positions of the first convergence zone are known from many publications. The most probable cause for such a disagreement, namely, the incorrect specification of the input data for the calculations, is considered. The lack of simultaneity between the hydrological surveys of the region and the acoustic experiments is emphasized. The experimental data obtained by the author in five ocean regions are presented. These data characterize the diurnal variability of the distance from the source to the nearest boundary of the convergence zone. The relations proposed by different researchers for calculating the sound speed from the temperature, salinity, and hydrostatic pressure are analyzed. It is shown that these relations lead to a substantial difference in the estimated depth dependence of the hydrostatic gradient of the sound speed. The position of the first convergence zone is calculated for the propagation conditions determined by vertical temperature and salinity profiles with the subsequent recalculation of these profiles into sound speed profiles by using eight different formulas known from the literature. It is shown that different formulas lead to different values of the distance to the first zone; this difference is substantially greater than that between the calculations and experiment. The necessity of improving the recalculation relations in view of the experimental data on sound propagation in natural oceanic waveguides, including the data on the actual positions of the convergence zones, is emphasized.     

Extracting the wavefunction of the LSP at the LHC

We consider associated production of squarks and gluinos with the lightest supersymmetric particle (LSP), or states nearly degenerate in mass with it. Though sub-dominant to pair production of color SU(3)-charged superpartners, these processes are directly sensitive to the wavefunction composition of the lightest neutralinos. Exploiting event-shape variables - including some introduced here for the first time - we are able to identify the composition of the LSP by selecting events involving a single high-pT jet recoiling against missing transverse energy. We illustrate the proposed technique on a set of benchmark cases and propose methods for applying these results in more realistic experimental environments.     

Set the controls for the heart of the Sun

In this paper we describe experiments conducted with high-power lasers that are attempting to replicate, for a very short time and in miniature, conditions found in the Sun. Experiments to date have reached conditions in the outer part of the Sun. To reach the Sun's centre requires compression of material to very much greater than solid density and heating to over ten million degrees. To achieve this, a new class of experiments and a new generation of high-power lasers are required.     

On the Question of the Source of the Apokamp

Technical Physics - The object of this work is the apokamp—a new type of plasma jet, which is formed from a bright offshoot emerging at the bending point of a channel of a high-voltage...