Abstract
We present detailed timing and spectral analyses of the transient X-ray pulsar RX J0209.6−7427 in the Small Magellanic Cloud during its 2019 giant outburst. With a better known distance than ...most galactic X-ray pulsars, its peak luminosity is determined to be (1.11 ± 0.06) × 10
39
erg s
−1
; it is thus a bona fide pulsating ultraluminous X-ray source (PULX). Owing to the broad energy band of Insight-HXMT, its pulsed X-ray emission was detected from 1 keV up to the 130–180 keV band, which is the highest energy emission detected from any PULXs outside the Milky Way. This allows us to conclude that its main pulsed X-ray emission is from the
fan beam
of the accretion column, and its luminosity is thus intrinsic. We also estimate its magnetic field of (4.8–8.6) × 10
12
or (1.7–2.2) × 10
13
G, from its spin evolution or transition in the accretion column structure during the outburst; we suggest that the two values of the magnetic field strength correspond to the dipole and multipole magnetic fields of the neutron star, similar to the recent discovery in the Galactic PULX Swift J0243.6+6124. Therefore, the nature of the neutron star and its ULX emission can be understood within the current theoretical frame of accreting neutron stars. This may have implications for understanding the nature of those farther away extragalactic PULXs.
ABSTRACT
This study was conducted to investigate the effect of nano-selenium (nano-Se) on performance, meat quality, immune function, oxidation resistance, and tissue selenium content in broilers. A ...total of five hundred forty 1-d-old male Arbor Acres broilers were randomly allotted to 1 of 5 treatments with each treatment being applied to 6 replicates of 18 chicks. The 5 treatments consisted of corn-soybean meal-based diets supplemented with 0.0, 0.3, 0.5, 1.0, or 2.0 mg/kg of nano-Se. The selenium content of the unsupplemented control diet was 0.09 mg/kg for the starter phase (0 to 21 d) and 0.08 mg/kg for the grower phase (22 to 42 d). There were no significant differences (P > 0.05) in performance, meat color, or immune organ index (thymus, bursa, and spleen) due to supplementation with nano-Se. On d 42, a significant quadratic effect of nano-Se was observed on glutathione peroxidase activity, free radical inhibition, contents of IgM, glutathione, and malondialdehyde in serum, on glutathione peroxidase activity, free radical inhibition in liver, and on glutathione peroxidase activity in muscle, with birds fed 0.30 mg/kg of nano-Se exhibiting the best effect and birds fed 2.0 mg/kg of nano-Se showing the worst effect on these parameters. Liver and muscle selenium content increased linearly and quadratically as the dietary nano-Se level increased (P < 0.01), and reached the highest value when 2.0 mg/kg of nano-Se was fed. Based on a consideration of all experiment indexes, 0.3 to 0.5 mg/kg is suggested to be the optimum level of supplementation of nano-Se, and the maximum supplementation of nano-Se could not be more than 1.0 mg/kg in broilers.
ABSTRACT
In 2011 December, PSR B054−69 experienced a spin-down rate transition (SRT), after which the spin-down power of the pulsar increased by $\sim 36{{\ \rm per\ cent}}$. About 1000 d after the ...SRT, the X-ray luminosity of the associated pulsar wind nebula (PWN) was found to brighten by $32\pm 8{{\ \rm per\ cent}}$. After the SRT, the braking index n of PSR B0540−69 changes from n = 2.12 to 0.03 and then keeps this value for about five years before rising to n = 0.9 in the following years. We find that most of the current models have difficulties in explaining the measured braking index. One exceptive model of the braking index evolution is the increasing dipole magnetic field of PSR B0540−69. We suggest that the field increase may result from some instabilities within the pulsar core that enhance the poloidal component at the price of toroidal component of the magnetic field. The increasing dipole magnetic field will result in the X-ray brightening of the PWN. We fit the PWN X-ray light curve by two models: one assumes a constant magnetic field within the PWN during the brightening and the other assumes an enhanced magnetic field proportional to the energy density of the PWN. It appears that the two models fit the data well, though the later model seems to fit the data a bit better. This provides marginal observational evidence that magnetic field in the PWN is generated by the termination shock. Future high-quality and high-cadence data are required to draw a solid conclusion.
RX J1301.9+2747 is an ultrasoft active galactic nucleus (AGN) with unusual X-ray variability that is characterized by a long quiescent state and a short-lived flare state. The X-ray flares are found ...to recur quasi-periodically on a timescale of 13−20 ks. Here, we report the analysis of the light curve in the quiescent state from two
XMM-Newton
observations spanning 18.5 years, along with the discovery of a possible quasi-periodic X-ray oscillation (QPO) with a period of ∼1500 s. The QPO is detected at the same frequency in the two independent observations, with a combined significance of > 99.89%. The QPO is in agreement with the relation between frequency and black hole mass (
M
BH
) that has been reported in previous works for AGNs and Galactic black hole X-ray binaries (XRBs). The QPO frequency is stable over almost two decades, suggesting that it may correspond to the high-frequency type found in XRBs and originates, perhaps, from a certain disk resonance mode. In the 3:2 twin-frequency resonance model, our best estimate on the
M
BH
range implies that a maximal black hole spin can be ruled out. We find that all ultrasoft AGNs reported so far display quasi-periodicities in the X-ray emission, suggesting a possible link on the part of the extreme variability phenomenon to the ultrasoft X-ray component. This indicates that ultrasoft AGNs could be the most promising candidates in future searches for X-ray periodicities.
ABSTRACT
It is well known that ordinary supernovae (SNe) are powered by 56Ni cascade decay. Broad-lined type Ic SNe (SNe Ic-BL) are a subclass of SNe that are not all exclusively powered by 56Ni ...decay. It was suggested that some SNe Ic-BL are powered by magnetar spin-down. iPTF16asu is a peculiar broad-lined type Ic supernova discovered by the intermediate Palomar Transient Factory. With a rest-frame rise time of only 4 d, iPTF16asu challenges the existing popular models, for example, the radioactive heating (56Ni-only) and the magnetar +56Ni models. Here we show that this rapid rise could be attributed to interaction between the SN ejecta and a pre-existing circumstellar medium ejected by the progenitor during its final stages of evolution, while the late-time light curve can be better explained by energy input from a rapidly spinning magnetar. This model is a natural extension to the previous magnetar model. The mass-loss rate of the progenitor and ejecta mass are consistent with a progenitor that experienced a common envelope evolution in a binary. An alternative model for the early rapid rise of the light curve is the cooling of a shock propagating into an extended envelope of the progenitor. It is difficult at this stage to tell which model (interaction+magnetar + 56Ni or cooling+magnetar + 56Ni) is better for iPTF16asu. However, it is worth noting that the inferred envelope mass in the cooling+magnetar + 56Ni is very high.
We infer the emission positions of twin kilohertz quasi-periodic oscillations (kHz QPOs) in neutron star low-mass X-ray binaries (NS-LMXBs) based on the Alfvén wave oscillation model (AWOM). For most ...sources, the emission radii of kHz QPOs cluster around a region of 16–19 km with the assumed NS radii of 15 km. Cir X-1 has the larger emission radii of 23 ∼ 38 km than those of the other sources, which may be ascribed to its large magnetosphere-disc radius or strong NS surface magnetic field. SAX J1808.4−3658 is also a particular source with the relative large emission radii of kHz QPOs of 20 ∼ 23 km, which may be due to its large inferred NS radius of 18 ∼ 19 km. The emission radii of kHz QPOs for all the sources are larger than the NS radii, and the possible explanations of which are presented. The similarity of the emission radii of kHz QPOs (∼16–19 km) for both the low/high luminosity Atoll/Z sources is found, which indicates that both sources share the similar magnetosphere-disc radii.
In biological nervous systems, the operation of interacting neurons depends largely on the regulation from astrocytes. Inspired by this biological phenomenon, spiking neural P systems, i.e. SN P ...systems, with astrocyte-like control were proposed and were proven to have “Turing completeness” as computing models. In this work, the application of such systems for creating logical operators is investigated. Specifically, it is obtained in a constructive way that SN P systems with astrocyte-like control can synthesize the operations of Boolean logic gates, i.e. AND, OR, NOT, NOR, XOR and NAND gates. The resulting systems are simple and homogeneous, which means only one type of neuron with a unique spiking rule is used. With these neural-like logic gates, more complex Boolean circuits with cascade connections can be constructed. As such, they can be used to implement finite computing devices, such as the finite transducers. These results demonstrate a novel method of constructing logic circuits that work in a neural-like manner, as well as shed some lights on potential directions of designing neural circuits theoretically.
Abstract
Male C57BL/6J mice treated with D-galactose (DG) were used to examine the effects of ergothioneine (EGT), melatonin (MEL), or their combination (EGT+MEL) on learning and memory abilities. ...The mice were divided into five groups and injected subcutaneously with DG (0.3 mL of 1% DG/mouse) except for group 1 (normal controls). Group 3 was orally supplemented with EGT 0.5 mg/kg body weight (bw), group 4 with MEL (10 mg/kg bw, p.o.), and group 5 with EGT+MEL. EGT and MEL were provided daily for 88 days, while DG was provided between days 7 to 56. Active avoidance task and Morris water-maze task were used to evaluate learning and memory abilities. DG treatment markedly increased escape latency and decreased the number of avoidance in the active avoidance test, whereas EGT and MEL alone significantly improved the performance. DG also impaired the learning and memory abilities in the water-maze task, and EGT and MEL alone also significantly improved the performance. EGT+MEL produced the strongest effects in both tasks. EGT and MEL alone markedly decreased β-amyloid protein accumulation in the hippocampus and significantly inhibited lipid peroxidation and maintained glutathione/glutathione disulfide ratio and superoxide dismutase activity in brain tissues of DG-treated mice. MEL alone completely prevented the rise in brain acetylcholine esterase activity induced by DG, whereas EGT and EGT+MEL were only partially effective. Overall, EGT, MEL, and, in particular, the combination of EGT and MEL effectively protect against learning and memory deficits in C57BL/6J mice treated with DG, possibly through attenuation of oxidative damage.
Nb-bearing nickel-based superalloys were fabricated by laser additive manufacturing using both continuous-wave (CW) and quasi-continuous-wave (QCW) laser modes. Effects of laser modes on Nb ...segregation and Laves phase morphology were investigated. The responses to aging treatments of two different fabricated samples were also investigated. CW mode tends to develop columnar dendrites, relative severe Nb segregation and continuous distributed Laves phase, while QCW mode tends to produce fine equiaxed dendrites, less Nb segregations and fine discrete Laves phase. In addition, the QCW sample responses better to aging treatment than the CW sample.
•A quasi-continuous-wave laser additive manufacturing is proposed to control Laves phase formation of Inconel 718.•Fine and discrete Lave phase particles with reduced Nb segregation are obtained.•The mechanism relies on high cooling rate, high dendrite growth rate and improved solute trapping.•Good aging response indicates the effective control of Nb segregation.
We present a catalog of galaxy cluster candidates, selected through their Sunyaev-Zel'dovich (SZ) effect signature in the first 720 deg2 of the South Pole Telescope (SPT) survey. This area was mapped ...with the SPT in the 2008 and 2009 austral winters to a depth of ~18 mu KCMB-arcmin at 150 GHz; 550 deg2 of it was also mapped to ~44 mu KCMB-arcmin at 95 GHz. We report photometrically derived redshifts for confirmed clusters and redshift lower limits for the remaining candidates. The catalog extends to high redshift with a median redshift of z = 0.55 and maximum confirmed redshift of z = 1.37. Forty-five of the clusters have counterparts in the ROSAT bright or faint source catalogs from which we estimate X-ray fluxes. A multi-wavelength observation program to improve the cluster mass calibration will make it possible to realize the full potential of the final 2500 deg2 SPT cluster catalog to constrain cosmology.
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