Radiation Spectral Analysis of 3D Dust Molecular Clusters(PAHs)and Peptoids under Ionization and Electric Field in ISM

Polycyclic aromatic hydrocarbons(PAHs),PANHs,and peptoids dust spectral calculations from the interstellar medium(ISM)are important for dust observations and theory.Our goal is to calculate the radiation spectrum of spherical PAHs dust clusters in a vacuum containing ionized and applied in the presence of an electric field.We propose a new simple computational model to calculate the size of three-dimensional spherical dust clusters formed by different initial dust structures.By the Vienna Ab-initio Simulation Package code,the density functional theory with the generalized approximation was used to calculate the electron density gradient and obtain the radiation spectrum of dust.When the radius of spherical dust clusters is~[0.009-0.042]μm,the dust radiation spectrum agrees well with the Z=0.02 mMMP stellar spectra,and the PAHs radiation spectrum of NGC 4676 at wavelengths of(0-5]μm and(5-10]μm,respectively.In the ionized state,the N-PAH,C_(10)H_(9)N,2(C_(4)H_(4))^(1+),and peptoids 4(CHON),(C_(8)H_(10)N_(2)O_(5))^(1+)dust clusters at 3.3μm,while the 2(C_(22)H_(21)N_(3)O_(2))^(1+),4(CHON)dust clusters at 5.2μm have obvious peaks.There is a characteristic of part of PAHs and peptoids clusters radiation at the nearinfrared wavelength of 2μm.However,especially after applying an electric field to the dust,the emission spectrum of the dust increases significantly in the radiation wavelength range[3-10]μm.Consequently,the dust clusters of PAHs,PANHs,and peptoids of the radius size~[0.009-0.042]μm are likely to exist in the ISM.

Temporal and Spectral Characteristics of Persistent Emission and Special Bursts of Magnetar SGR J1935+2154 Based on Insight-HXMT

In October 2022,the magnetar SGR J1935+2154 entered the active outburst state.During the episode,the InsightHXMT satellite carried out a long observation that lasted for 20 days.More than 300 bursts were detected,and a certain amount of persistent radiation signals were also accumulated.This paper mainly introduces the results of persistent radiation profile folding and period search based on Insight-HXMT data.At the same time,the burst phase distribution characteristics,spectral lag results of burst,the spectral characteristics of zero-lag bursts and the time-resolved spectral evolution characteristics of high-flux bursts are reported.We found that there is no significant delay feature during different energy bands for the bursts of SGR J1935+2154.The observed zero-lag burst does not have a unique spectrum.The time-resolved spectrum of the individual burst has consistent spectral types and spectral parameters at different time periods of the burst.We also find that the burst number phase distribution and the burst photon phase distribution have the same tendency to concentrate in specific regions of the persistent emission profile.

A Possible X-ray Quasi-periodic Oscillation in the Narrow-line Seyfert 1 Galaxy Mrk 142

A possible quasi-periodic oscillation(QPO) at frequency 7.045 × 10^(-5) Hz is found in the narrow-line Seyfert 1galaxy Mrk 142 in the data of XMM-Newton collected on 2020 April 11.We find that the QPO signal is statistically significantly larger than the 5σ level and highly coherent with quality factor Q > 5 at the 0.3–10 keV band by using the method of the Lomb–Scargle Periodogram,the Weighted Wavelet Z-transform and the REDFIT.We analyze the data in 0.3–0.6 keV,0.6–1 keV,1–3 keV and 3–10 keV energy bands,and find obvious QPO signals at 0.3–0.6 keV and 1–3 keV bands.We then analyze the time-average spectra and time variability at the QPO frequency of 7.045 × 10^(-5) Hz,and use a model to fit them.We find that the QPO signal mainly comes from the X-ray hot corona.

Spatial dependence of high energy electrons and their radiations in pulsar wind nebulae

We investigate the spatial dependence of high energy electrons and their radiations in pulsar wind nebulae （PWNe）. By assuming a time-dependent broken power-law injection and spatial dependence of convection velocity, magnetic field strength and diffusion coefficient on the radial distance of an expand- ing system, we numerically solve the Fokker-Planck transport equation including convection, diffusion, adiabatic loss and radiative loss in spherical coordinates, and investigate the effects of magnetic field, PWN age, maximum energy of electrons, and diffusion coefficient on electron spectra and non-thermal photon emissions. Our results indicate that （1） electron spectra and the corresponding photon spectra are a function of radial distance r of the expanding system; （2） for a given expansion velocity, the increase of the PWN age causes a slower decrease of the convection velocity （V ∝ r-β） and a more rapid decrease of the magnetic field strength （B ∝ r-1＋β）, but a more rapid increase of the diffusion coefficient （k∝ r1-β） because the index β decreases with the PWN age; and （3） the lower energy part of the electron spectra is dominated by convection and adiabatic loss, but the higher energy part is dominated by the competition between syn- chrotron loss and diffusion, and such a competition is a function of radial distance. Therefore the diffusion effect has an important role in the evolution of electron spectra as well as non-thermal photon spectra in a PWN.

New Features of the Pulsar B0950+08 Radiation at the Frequency of 111 MHz

Results of long time observations of the pulsar B0950+08 are given.These observations were carried out at the LPA radio telescope at the frequency of 111 MHz from January of 2016 to May of 2019(450 days).A strong variability in emission of this pulsar has been detected with changes in signal to noise ratios hundreds of times.Part of the long-time flux density variability can be explained by refractive scintillations in the interstellar medium.The existence of radiation between the interpulse(IP)and main pulse(MP)was confirmed.It was more powerful than at high frequencies.We detected the unusual IP and precursor(Pr)radiation on 2017 August 1.On the basis of 65 strong IPs we found the correlations between energies of IP and Pr and between the phase of IP and the distance Pr–IP.It is shown that the observed peculiarities of this pulsar can be explained in the frame of the aligned rotator model.We estimated distances of radiation levels from the center of the neutron star.The calculated value of the initial period of 0.2 s means that not all pulsars are born with millisecond periods.The large age of the pulsar(6.8 million years)and the small angle between its magnetic moment and the rotation axis(less than 20°)confirm the suggestion related to pulsar evolution with respect to alignment.

New Continuum Observations of the Andromeda galaxy M31 with FAST

We present a new total intensity image of M31 at 1.248 GHz,observed with the Five-hundred-meter Aperture Spherical radio telescope(FAST)with an angular resolution of 4'and a sensitivity of about 16 mK.The new FAST image clearly reveals weak emission outside the ring due to its high sensitivity on large-scale structures.We derive a scale length of 2.7 kpc for the cosmic ray electrons and find that the cosmic ray electrons propagate mainly through diffusion by comparing the scale length at 4.8 GHz.The spectral index of the total intensity varies along the ring,which can be attributed to the variation of the spectra of synchrotron emission.This variation is likely caused by the change of star formation rates along the ring.We find that the azimuthal profile of the non-thermal emission can be interpreted by an axisymmetric large-scale magnetic field with varying pitch angle along the ring,indicating a complicated magnetic field configuration in M31.

The Doppler Effect and Spectral Energy Distribution of Blazars

The relativistic beaming model is adopted to discuss quantitatively the observational differences between radio-selected BL Lac objects (RBLs) and X-ray- selected BL Lac objects (XBLs), and between BL Lac objects and flat spectrum radio quasars (FSRQs). The main results are the following: (1) In the Doppler corrected color-color ( ) diagram, XBLs and FSRQs occupy separated regions, while RBLs bridge the gap between them. These properties suggest that similar intrinsic physical processes operate in all the objects under a range of intrinsic physical conditions. (2) Our results are consistent with the results of Sambruna, Maraschi and Urry (1996) from other methods. We show the ■xox introduced by Sambruna to be a good index for describing the energy distribution because it represents the intrinsic energy distribution and includes the Doppler correction. (3) The Doppler effect of relativistic beaming is the main mechanism, and the physical differences (such as magnetic fields, electron energies) are also important complementary factors for understanding the relation between XBLs and RBLs;

What determines the observational differences of blazars？

We examine the scenario that the Doppler factor determines the observational differences of blazars. Significantly negative correlations are found between the observational synchrotron peak frequency and the Doppler factor. After correcting the Doppler boosting, the intrinsic peak frequency has a tight linear relation with the Doppler factor. It is interesting that this relation is consistent with the scenario that the black hole mass governs both the bulk Lorentz factor and the synchrotron peak frequency. In addition, the distinction between the kinetic jet powers of BL Lac objects and fiat spectrum radio quasars disappears after the boosting factor δ2 is considered. The negative correlation between the peak frequency and the observational isotropic luminosity, known as the blazar sequence, also disappears after the Doppler boosting is corrected. We also find that the correlation between the Compton dominance and the Doppler factor exists for all types of blazars. Therefore, this correlation is unsuitable for examining the external Compton emission dominance.

Quark nova model for fast radio bursts

Fast radio bursts （FRBs） are puzzling, millisecond, energetic radio transients with no discernible source; observations show no counterparts in other frequency bands. The birth of a quark star from a parent neutron star experiencing a quark nova - previously thought undetectable when born in isolation - provides a natural explanation for the emission characteristics of FRBs. The generation of unstable r-process elements in the quark nova ejecta provides millisecond exponential injection of electrons into the surrounding strong magnetic field at the parent neutron star＇s light cylinder via β-decay. This radio synchrotron emission has a total duration of hundreds of milliseconds and matches the observed spectrum while reducing the inferred dispersion measure by approximately 200 cm-3 pc. The model allows indirect measurement of neutron star magnetic fields and periods in addition to providing astronomical measurements of β-decay chains of unstable neutron rich nuclei. Using this model, we can calculate expected FRB average energies （- 1041 erg） and spectral shapes, and provide a theoretical framework for determining distances.

Properties of BL Lac Objects with Redshift ≤ 0.2

We present a large sample which includes 82 BL Lac objects with red- shifts below 0.2 from recent literature. We find strong correlations in both flux and luminosity between the radio (5 GHz) and optical bands (5500 A). The correlations in other bands are very weak. Five TeV BL Lacs and two suspect sources are found to have similar properties as high- frequency- peaked BL Lacs (HBLs). Our results suggest that both the radio and optical emissions are from the same radiation mech- anism in the SSC model. The TeV BL Lac candidates should be HBLs or HBL-like objects with small redshifts.

Ionization state of cosmic hydrogen by early stars and quasars

Cosmic hydrogen is reionized and maintained in its highly ionized state by the ultraviolet emission attributed to an early generation of stars and quasars. The Lyα opacity observed in absorption spectra of high-redshift quasars permits more stringent constraints on the ionization state of cosmic hydrogen. Based on density perturbation and structure formation theory, we develop an analytic model to trace the evolution of the ionization state in the post-overlap epoch of reionization, in which the bias factor is taken into account. For quasars, we represent an improved luminosity function by utilizing a hybrid approach for the halo formation rate that is in reasonable agreement with the published measurements at 2 ≤ z ≤ 6. Comparison with the classic Press-Schechter mass function of dark matter halos, we demonstrate that the biased mass distribution indeed enhances star formation efficiency in the overdense environment by more than 25 per cent following the overlap of ionized bubbles. In addition, an alternative way is introduced to derive robust estimates of the mean free path for ionizing photons. In our model, star-forming galaxies are likely to dominate the ionizing background radiation beyond z = 3, and quasars contribute equally above a redshift of z ～ 2.5. From 5 ≤ z ≤ 6, the lack of evolution in photoionization rate can thus be explained by the relatively flat evolution in star formation efficiency, although the mean free path of ionizing photons increases rapidly. Moreover, in the redshift interval z ～ 2 - 6, the expected mean free path and Gunn-Peterson optical depth obviously evolve by a factor of ～ 500 and ～50 respectively. We find that the relative values of critical overdensities for hydrogen ionization and collapse could be 430% at z ≈2 and 2% at z ≈6, suggesting a rapid overlap process in the overdense regions around instant quasars following reionization. We further illustrate that the absolute estimates of the fraction of neutral hydrogen computed from theoretical models may not be important because of comparable uncertainties in the computation.

A low-latency pipeline for GRB light curve and spectrum using Fermi/GBM near real-time data

Rapid response and short time latency are very important for Time Domain Astronomy, such as the observations of Gamma-ray Bursts（GRBs） and electromagnetic（EM） counterparts of gravitational waves（GWs）. Based on near real-time Fermi/GBM data, we developed a low-latency pipeline to automatically calculate the temporal and spectral properties of GRBs. With this pipeline, some important parameters can be obtained, such as T_（90） and fluence, within ～ 20 min after the GRB trigger.For ～ 90% of GRBs, T90 and fluence are consistent with the GBM catalog results within 2σ errors.This pipeline has been used by the Gamma-ray Bursts Polarimeter（POLAR） and the Insight Hard Xray Modulation Telescope（Insight-HXMT） to follow up the bursts of interest. For GRB 170817 A, the first EM counterpart of GW events detected by Fermi/GBM and INTEGRAL/SPI-ACS, the pipeline gave T90 and spectral information 21 min after the GBM trigger, providing important information for POLAR and Insight-HXMT observations.

BL Lacertae objects and the extragalactic γ-ray background

A tight correlation between γ-ray and radio emission is found for a sample of BL Lacertae （BL Lac） objects detected by the Fermi Gamma-ray Space Telescope （Fermi） and the Energetic Gamma-Ray Experiment Telescope （EGRET）. The γ-ray emission of BL Lac objects exhibits strong variability, and the detection rate of γ-ray BL Lac objects is low, which may be related to the γ-ray duty cycle of BL Lac objects. We estimate the γ-ray duty cycle, δγ ≌ 0.11, for BL Lac objects detected by EGRET and Fermi. Using the empirical relation of γ-ray emission with radio emission and the estimated γ-ray duty cycle δγ, we derive the γ-ray luminosity function （LF） of BL Lac objects from their radio LE Our derived γ-ray LF of BL Lac objects can almost reproduce that calculated with the recently released Fermi bright active galactic nuclei （AGN） sample. Comparison of the derived LF of the γ-ray BL Lac objects in this work with that derived by Abdo et al. （2009a） requires the γ-ray duty cycle of BL Lac objects to be almost luminosity-independent. We find that - 45% of the extragalactic diffuse γ-ray background （EGRB） is contributed by BL Lac objects. Combining the estimate of the quasar contribution to the EGRB in the previous work, we find that 77% of the EGRB is contributed by BL Lac objects and radio quasars.

Spectral indices for radio emission of 228 pulsars

We determine spectral indices of 228 pulsars by using Parkes pulsar data observed at 1.4 GHz, among which 200 spectra are newly determined. The indices are distributed in the range from -4.84 to -0.46. Together with known pulsar spectra from literature, we tried to find clues to the pulsar emission process. The wealCcorrelations between the spectral index, the spin-down energy loss rate E and the poten- tial drop in the polar gap Aψ hint that emission properties are related to the particle acceleration process in a pulsar＇s magnetosphere.

Spindown of magnetars:quantum vacuum friction?

Magnetars are proposed to be peculiar neutron stars which could power their X-ray radiation by super-strong magnetic fields as high as 〉 10^（14） G.However,no direct evidence for such strong fields has been obtained till now,and the recent discovery of low magnetic field magnetars even indicates that some more efficient radiation mechanism than magnetic dipole radiation should be included.In this paper,quantum vacuum friction（QVF） is suggested to be a direct consequence of super-strong surface fields,therefore the magnetar model could then be tested further through QVF braking.The high surface magnetic field of a pulsar interacting with the quantum vacuum results in a significantly high spindown rate（P）.It is found that a QVF dominates the energy loss of pulsars when the pulsar＇s rotation period and its first derivative satisfy the relationship P^3P 〉 0.63 ×10^（-16）ξ^（-4） s^2,whereξ is the ratio of the surface magnetic field over the dipole magnetic field.In the ＂QVF ＋ magnetodipole＂ joint braking scenario,the spindown behavior of magnetars should be quite different from that in the pure magnetodipole model.We are expecting these results could be tested by magnetar candidates,especially low magnetic field cases,in the future.

More Emission Cones: Multi-frequency Simulation of the Pulse Profiles of PSR J0437-4715

Pulsar radio emission beams have been studied observationally for a long time, and the suggestion is that they consist of the so-called core and conal components. To reproduce these components is a challenge for any emission model, and that the pulse profile of pulsars changes with frequency presents even a greater challenge. Assuming a local surface magnetic structure (to produce the core or central beam) and a global dipole magnetic field (to produce the conal beams), Gil & Krawczyk (1997) applied curvature radiation to the pulse profile simulation of PSR J0437-4715 (hereafter the GK model). Here we present an alternative multi-frequency simulation of the same profiles within the framework of the Inverse Compton Scattering (ICS) model. It is obtained from our simulation (1) that besides the core, the inner cone and the outer cone, there is an outer-outer cone; (2) that the emission components of the core and cones evolve strongly with frequency. Some important differences between the ICS model and the GK model are discussed, which need to be tested by further observations.

Modeling the rail surface unevenness of a high-precision radio telescope

This study proposed a coarse-fine mixed model for describing the rail surface unevenness of an ultra-large fully steerable radio telescope （Qi Tai Telescope） with a diameter of 110 meters. The rail surface unevenness includes information on error arising from two different scales, i.e., the long-period- short-change and the short-period-long-change. Consequently, in this study an idea of a mixed model was proposed, in which trigonometric and fractal functions were, respectively, used to describe infor- mation on error from two scales. Key parameters were determined by using the least squares method and the wavelet transform method, and finally, a specific mathematical expression of the model was obtained by optimization. To validate the effectiveness of the new modeling method, the mixed model was then used to describe the rails of the Green Bank Telescope, the Large Millimeter Telescope, and a radio telescope in Miyun, Beijing. A comparative study revealed that the maximum error was less than 15 %, thus the result was superior to those of existing modeling methods.

An Annular Gap Acceleration Model for γ-ray Emission of Pulsars

If the binding energy of the pulsar＇s surface is not so high （the case of a neutron star）, both negative and positive charges will flow out freely from the surface of the star. An annular free flow model for 7-ray emission of pulsars is suggested. It is emphasized that： （1） Two kinds of acceleration regions （annular and core） need to be taken into account. The annular acceleration region is defined by the magnetic field lines that cross the null charge surface within the light cylinder. （2） If the potential drop in the annular region of a pulsar is high enough （normally the case for young pulsars）, charges in both the annular and the core regions could be accelerated and produce primary gamma-rays. Secondary pairs are generated in both regions and stream outwards to power the broadband radiations. （3） The potential drop grows more rapidly in the annular region than in the core region. The annular acceleration process is a key process for producing the observed wide emission beams. （4） The advantages of both the polar cap and outer gap models are retained in this model. The geometric properties of the 7-ray emission from the annular flow are analogous to that pre-sented in a previous work by Qiao et al., which match the observations well. （5） Since charges with different signs leave the pulsar through the annular and the core regions respectively, the current closure problem can be partially solved.