The “Bi-drifting” subpulses of PSR J0815+0939 observed with the Five-hundred-meter Aperture Spherical radio Telescope

We report the “Bi-drifting” subpulses observed in PSR J0815+0939 using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The observation at band from 1050-1450MHz is evenly divided into two bands, i.e., the bands at center frequencies 1150MHz and 1350 MHz. The mean pulse profiles and the “Bi-drifting” subpulses at this two bands are investigated. It is found that the pulse profiles at this two frequencies show four emission components, and the peak separations between four emission components decrease with the increase of frequency. In addition, the ratio of peak intensity of each component to the intensity of component IV at 1150MHz is larger than that at 1350 MHz. We carry out an analysis of the longitude-resolved fluctuation spectrum and two-dimensional fluctuation spectrum for each emission component, and find that the P3 of components I, II and III are about 10.56, 10.57 and 10.59 s at 1150MHz and 1350 MHz. However, the reliable measurements of P3 of component IV and P2 for these four components were not obtained due to the low signal-to-noise ratio of observation data. The pulse energy distributions at frequencies 1150 and 1350MHz are presented, and it is found that no nulling phenomenon have been found in this pulsar. With our observation from the FAST, the “Bi-drifting” subpulse phenomenon of PSR J0815+0939 is expanded from 400MHz to 1350 MHz, which is helpful for the relevant researchers to test and constrain the pulsar emission model, especially the model of “Bi-drifting” subpulse.

Enhanced terahertz emission from mushroom-shaped InAs nanowire network induced by linear and nonlinear optical effects

The development of powerful terahertz (THz) emitters is the cornerstone for future THz applications, such as communication, medical biology, non-destructive inspection, and scientific research. Here, we report the THz emission properties and mechanisms of mushroom-shaped InAs nanowire (NW) network using linearly polarized laser excitation. By investigating the dependence of THz signal to the incidence pump light properties (e.g., incident angle, direction, fluence, and polarization angle), we conclude that the THz wave emission from the InAs NW network is induced by the combination of linear and nonlinear optical effects. The former is a transient photocurrent accelerated by the photo-Dember field, while the latter is related to the resonant optical rectification effect. Moreover, the p-polarized THz wave emission component is governed by the linear optical effect with a proportion of ~85% and the nonlinear optical effect of ~15%. In comparison, the s-polarized THz wave emission component is mainly decided by the nonlinear optical effect. The THz emission is speculated to be enhanced by the localized surface plasmon resonance absorption of the In droplets on top of the NWs. This work verifies the nonlinear optical mechanism in the THz generation of semiconductor NWs and provides an enlightening reference for the structural design of powerful and flexible THz surface and interface emitters in transmission geometry.

A Cosmological Fireball with Thirty-Percent Gamma-Ray Radiative Efficiency

Gamma-ray bursts (GRBs) are the most powerful explosions in the universe. The composition of the jets is, however, subject to debate\cite{Peer2015,Zhang2018}. Whereas the traditional model invokes a relativistic matter-dominated fireball with a bright photosphere emission component\cite{Meszaros2000}, the lack of the detection of such a component in some GRBs\cite{Abdo2009} has led to the conclusion that GRB jets may be Poynting-flux-dominated\cite{Zhang2009}. Furthermore, how efficiently the jet converts its energy to radiation is poorly constrained. A definitive diagnosis of the GRB jet composition and measurement of GRB radiative efficiency requires high-quality prompt emission and afterglow data, which has not been possible with the sparse observations in the past. Here we report a comprehensive temporal and spectral analysis of the TeV-emitting bright GRB 190114C. Its fluence is one of the highest of all GRBs detected so far, which allows us to perform a high-significance study on the prompt emission spectral properties and their variations down to a very short timescale of about 0.1 s. We identify a clear thermal component during the first two prompt emission episodes, which is fully consistent with the prediction of the fireball photosphere model. The third episode of the prompt emission is consistent with synchrotron radiation from the deceleration of the fireball. This allows us to directly dissect the fireball energy budget in a parameter-independent manner\cite{Zhang2021} and robustly measure a nearly $30\%$ radiative efficiency for this GRB. The afterglow microphysics parameters can be also well constrained from the data. GRB 190114C, therefore, exhibits the evolution of a textbook-version relativistic fireball, suggesting that fireballs can indeed power at least some GRBs with high efficiency.

Search for Zeeman-splitting of OH 6.035 GHz line in the young planetary nebula K 3-35

ABSTRACT Magnetic field could play a role in the formation and early evolution of non-spherical planetary nebulae (PNe). The predominant source of information of the magnetic fields in PNe is the polarization observations of maser emission. To date, distinct and/or possible Zeeman pairs have only been reported towards four PNe by measuring the OH ground-state transitions at 1.6–1.7 GHz. With the C-band (4–8 GHz) receiving system of the Shanghai TianMa 65-m radio telescope, we aim to search for possible Zeeman pairs of the PNe towards which the OH excited-state 6.035 GHz maser lines have been detected. For the young PN K 3-35, a new emission component near VLSR = 20.5 km s−1, which is currently the strongest (Ipeak ∼ 0.3 Jy) among the four components towards K 3-35 is detected. A clear S-shaped feature corresponding to this new emission component is observed in the Stokes V spectrum. Frequency shifts are seen between the fitted left-hand circular polarization and right-hand circular polarization emission peaks for the two emission components near VLSR = 19.7 and 20.5 km s−1. If the S-shaped profile and the frequency shifts are the results of Zeeman-splitting, the line-of-sight magnetic field strengths of +2.9 ± 0.6 and +4.5 ± 0.4 mG can be inferred for these two emission components, respectively.

Joint XMM-Newton and NuSTAR observations of the reflection spectrum of III Zw 2

Detecting and modeling the reprocessed hard X-ray emission component in the accretion flow, the so-called reflection spectrum, is a main tool used to estimate black hole spins in a wide range of astrophysical black holes, regardless of their mass or distance. In this work, we study the X-ray spectra of the Seyfert I galaxy III Zw 2 by using multiepoch XMM-Newton, NuSTAR, and Suzaku observations. The X-ray spectra exhibit a soft-excess below 1 keV and a prominent excess at the location of the broad Fe Kα line at 6.4 keV. To account for these spectral features, we fit the spectra with multiple models including an ionized partially covering absorber and an accretion disk reflection model. To fully resolve the reflection component, we analyzed jointly the XMM-Newton and NuSTAR observations taken in 2017 and archival XMM-Newton data from 2000. Assuming the reflection scenario, the resulting model fits support for a rapidly spinning black hole (a ≥ 0.98) in this radio-intermediate source. The X-ray spectra in 2000 and 2017 are remarkably similar; the only difference pertains to the reflection fraction, which is possibly due to a change in the geometry of the accretion flow. However, the Suzaku observation is markedly different, and we suggest this could be an effect of a jet contribution in the X-ray band, which is supported by the elevated radio flux during this observation.

Spectral index in the radio continuum 140 MHz – 1.4 GHz emission for compact star-forming galaxies

The sample of compact star-forming galaxies (CSFGs) has been identified with sources in the catalogues of radio sources. It includes only galaxies with active star formation without objects with spectral signs of active galactic nuclei. For CSFGs with known flux densities in radiocontinuum at frequencies of 1.4 GHz from the FIRST or the NVSS and in the range of 120–168 MHz from the LOFAR, as well as in hydrogen emission lines from the SDSS, the spectral index and the spectral index of non-thermal emission component for these frequencies have been estimated. Note that obtaining the spectral index of nonthermal emission component is a much more difficult task than determining the spectral index of total emission. It is shown that the approximation by the model dependence using the least squares method can lead to unreliable estimates of the fraction of thermal (free-free) emission. Therefore, the flux densities of the thermal component are derived from the extinction- and aperture corrected fluxes of the Hα emission line. This method of estimation without using a fitting is more reliable. It is shown that the fact that derived spectra in radio range are quite flat is due, in particular, to the influence of selection effects caused by limited sensitivity of radio telescopes. For the same reason, only galaxies with a small fraction of thermal emission were included in the sample. Therefore, the spectral index is not much different from the spectral index of non-thermal emission.

On the ultra-compact nature of the neutron star system 1RXS J170854.4−321857: insights from X-ray spectroscopy

ABSTRACT The relatively small family of ultra-compact X-ray binary systems is of great interest for many areas of astrophysics. We report on a detailed X-ray spectral study of the persistent neutron star low-mass X-ray binary 1RXS J170854.4−321857. We analysed two XMM–Newton observations obtained in late 2004 and early 2005 when, in agreement with previous studies, the system displayed an X-ray luminosity (0.5–10 keV) of ${\sim} 1\times 10^{36}\, \mathrm{erg~s}^{-1}$. The spectrum can be described by a Comptonized emission component with Γ ∼ 1.9 and a distribution of seed photons with a temperature of ∼0.23 keV. A prominent residual feature is present at soft energies, which is reproduced by the absorption model if overabundances of Ne and Fe are allowed. We discuss how similar observables, which might be attributed to the peculiar (non-solar) composition of the plasma donated by the companion star, are a common feature in confirmed and candidate ultra-compact systems. Although this interpretation is still under debate, we conclude that the detection of these features along with the persistent nature of the source at such low luminosity and the intermediate–long burst that it displayed in the past confirms 1RXS J170854.4−321857 as a solid ultra-compact X-ray binary candidate.

Representativeness of emissions of toxic substances in bench tests reflecting the road traffic conditions of a vehicle

The results of measurements of exhaust emissions in real road traffic differ significantly from the results of stationary homologation tests. One of the solutions, helpful in determining the actual emission, is the creation of stationary exhaust emission tests simulating the use of the vehicle on the road. The article presents the method of reconstructing the synthetic driving test obtained on the basis of road tests and presents the obtained profile of the speed course. The authors discussed the reasonableness of selecting the emission component determining the correctness of the representativity of the stationary test obtained, which determines the amount of work done by the engine.

Photoionized emission and absorption features in the high-resolution X-ray spectra of NGC 3783

Our Swift monitoring program triggered two joint XMM-Newton, NuSTAR, and HST observations on 11 and 21 December 2016 targeting NGC 3783 because its soft X-ray continuum was heavily obscured. Consequently, emission features, including the O VII radiative recombination continuum, stand out above the diminished continuum. We focus on the photoionized emission features in the December 2016 Reflection Grating Spectrometer (RGS) spectra, and compare them to the time-averaged RGS spectrum obtained in 2000–2001 when the continuum was unobscured. A two-phase photoionized plasma is required to account for the narrow emission features. These narrow emission features are weakly varying between 2000–2001 and December 2016. We also find a statistically significant broad emission component in the time-averaged RGS spectrum in 2000–2001. This broad emission component is significantly weaker in December 2016, suggesting that the obscurer is farther away than the X-ray broad-line region. In addition, by analyzing the archival high-resolution X-ray spectra, we find that nine photoionized absorption components with different ionization parameters and kinematics are required for the warm absorber in X-rays.

High cadence, linear, and circular polarization monitoring of OJ 287

Aims. We present a multifrequency, dense radio monitoring program of the blazar OJ 287 using the 100-m Effelsberg radio telescope. The program aims to test different binary supermassive black hole (SMBH) scenarios and studying the physical conditions in the central region of this bright blazar. Here, we analyze the evolution in total flux density, linear and circular polarization as a means to study the OJ 287 jet structure and its magnetic field geometry. Methods. We used a recently developed, high-precision data analysis methodology to recover all four Stokes parameters. We measured the total flux density of OJ 287 at nine bands from 2.64 GHz to 43 GHz, the linear polarization parameters at four bands between 2.64 GHz and 10.45 GHz, and the circular polarization at two bands, 4.85 GHz and 8.35 GHz. The mean cadence of our measurements is ten days. Results. Between December 2015 and January 2017 (MJD 57370–57785), OJ 287 showed flaring activity and complex linear and circular polarization behavior. The radio electric vector position angle (EVPA) showed a large clockwise (CW) rotation by ∼340° with a mean rate of −1.04°/day. Based on concurrent very long baseline interferometric (VLBI) polarization data at 15 GHz and 43 GHz, the rotation seems to originate within the jet core at 43 GHz (projected angular size ≤0.15 mas or 0.67 pc at the redshift of the source). Moreover, optical polarization data show a similar monotonic CW rotation with a rate of about −1.1°/day which is superposed with shorter and faster rotations that exhibit rates of about 7.8°/day, mainly in the CW sense. Conclusions. The flux density and polarization variability of the single dish, VLBI and optical data is consistent with a polarized emission component propagating on a helical trajectory within a bent jet. We constrained the helix arc length to 0.26 pc and radius to ≤0.04 pc as well as the jet bending arc length projected on the plane of the sky to ≤1.9–7.6 pc. A similar bending has been observed also in high angular resolution VLBI images of the OJ 287 jet at its innermost regions. The helical trajectory covers only a part of the jet width, possibly its spine. In addition, our results indicate the presence of a stable polarized emission component. Its EVPA (−10°) is oriented perpendicular to the large scale jet, suggesting dominance of the poloidal magnetic field component. Finally, the EVPA rotation begins simultaneously with an optical flare and hence the two might be physically connected. That optical flare has been suggested to be linked to the interaction of a secondary SMBH with the inner accretion disk or originating in the jet of the primary.