Discovery of 40.5 ks Hard X-Ray Pulse-phase Modulations from SGR 1900+14

X-ray timing properties of the magnetar SGR 1900+14 were studied, using the data taken with Suzaku in 2009 and NuSTAR in 2016, for a time lapse of 114 and 242 ks, respectively. On both occasions, the object exhibited the characteristic two-component spectrum. The soft component, dominant in energies below ∼5 keV, showed a regular pulsation, with a period of P = 5.21006 s as determined with the Suzaku XIS, and P = 5.22669 with NuSTAR. However, in ≳ 6 keV where the hard component dominates, the pulsation became detectable with the Suzaku HXD and NuSTAR only after the data were corrected for periodic pulse-phase modulation, with a period of T = 40 − 44 ks and an amplitude of ≈1 s. Further correcting the two data sets for complex energy dependences in the phase modulation parameters, the hard X-ray pulsation became fully detectable, in 12–50 keV with the HXD and 6–60 keV with NuSTAR, using a common value of T = 40.5 ± 0.8 ks. Thus, SGR 1900+14 becomes a third example, after 4U 0142+61 and 1E 1547−5408, to show the hard X-ray pulse-phase modulation, and a second case of energy dependences in the modulation parameters. The neutron star in this system is inferred to perform free precession, as it is axially deformed by ≈ P/T = 1.3 × 10−4, presumably due to ∼ 1016 G toroidal magnetic fields. As a counterexample, the Suzaku data of the binary pulsar 4U 1626−67 were analyzed, but no similar effect was found. These results altogether argue against the accretion scenario for magnetars.

Пики термодесорбции водорода: моделирование и интерпретация

Various models of hydrogen thermal desorption peaks are analyzed. The dynamics model of the volume-averaged concentration with a continuum parameter allows integrally taking into account the degree of dominance of the limiting factors (diffusion and recombination of atoms into molecules during desorption). An analytical criterion for peaks symmetry is proposed in the context of comparison with the method of decomposing the component spectrum into the sum of Gaussian. Modifications of the Kissinger method for estimating the activation energy of desorption in experiments with several heating rates and procedures for solving the inverse problem of parametric identification of a unimodal peak using only one heating rate are presented. A comparative with a diffusion model with dynamic boundary conditions is performed. It is shown that the cause of local peaks can be not only capture with different binding energies but also the dynamics of interaction of bulk and surface processes, change in the surface structure during heating.

Analysis of H/V Ratio Curve to Estimate Seismic Hazard Vulnerability in Lombok Island, West Nusa Tenggara, Indonesia

In 2018, Lombok Island was hit by a series of destructive earthquakes. According to Indonesian Meteo- rological, Climatological, and Geophysical Agency data, about 1,973 felt earthquakes (M > 3) which shaken Lombok were recorded during August 2018 with three earthquakes with the largest magnitude of 6.9 Mw, 6.8 Mw, and 6.2 Mw. National Board for Disaster Management reported about 555 deaths, 1,833 people injured, and 186,010 houses damaged as a result of Lombok earthquake on August 5th, 2018. A number of seismometers were placed on Lombok Island from August 3rd, 2018 to October 19th, 2018 to monitor the aftershock events. There are 17 stations that record seismicity in Lombok consisting of 10 broadband sensors and 7 short period sensors. In this study, we used the Horizontal-to-Vertical Spectral Ratio (HVSR) method to analyze the risk of earthquake in the Lombok region. The basic concept of this method is to do a comparison between the horizontal component spectrum and the vertical component spectrum of a wave, where theoretically the particle movement of the horizontal component is greater than the particle movement of the vertical component on soft ground, whereas on the hard ground both components (horizontal and vertical) will be similar. H/V curve obtained from earthquake record- ings (Earthquake Horizontal-to-Vertical Ratio/EHVR) and H/V curve obtained from microtremor recordings (Microtremor Horizontal-to-Vertical Ratio/MHVR) shows good agreement and high correlation. Empirical correction of EMR (Earthquake-to-Microtremor Ratio) managed to decrease the difference of estimation of predominant frequency and amplification factor between EHVR and MHVR. Predominant frequency, amplification, and seismic vulnerability map agree with the geological condition of Lombok Island, where high value of amplification and seismic vulnerability was found on soft and thick ground. This study conclude that the maximum ground acceleration and the construction of the building should also considered when one wants to investigate the effect of an earthquake to the damage occurred, beside the site effects.

Soft excess in the quiescent Be/X-ray pulsar RX J0812.4–3114

We report a 72 ks XMM–Newton observation of the Be/X-ray pulsar (BeXRP) RX J0812.4–3114 in quiescence ($L_X \approx 1.6\times 10^{33}\, \mathrm{erg\, s^{-1}}$). Intriguingly, we find a two-component spectrum, with a hard power-law (Γ ≈ 1.5) and a soft blackbody-like excess below ≈1 keV. The blackbody component is consistent in kT with a prior quiescent Chandra observation reported by Tsygankov et al. and has an inferred blackbody radius of ≈10 km, consistent with emission from the entire neutron star (NS) surface. There is also mild evidence for an absorption line at $\approx 1$ and/or $\approx 1.4\, \mathrm{keV}$. The hard component shows pulsations at P ≈ 31.908 s (pulsed fraction 0.84 ± 0.10), agreeing with the pulse period seen previously in outbursts, but no pulsations were found in the soft excess (pulsed fraction $\lesssim \!31\, {\rm per\, cent}$). We conclude that the pulsed hard component suggests low-level accretion on to the NS poles, while the soft excess seems to originate from the entire NS surface. We speculate that, in quiescence, the source switches between a soft thermal-dominated state (when the propeller effect is at work) and a relatively hard state with low-level accretion, and use the propeller cut-off to estimate the magnetic field of the system to be $\lesssim\! 8.4\times 10^{11}\, \mathrm{G}$. We compare the quiescent thermal LX predicted by the standard deep crustal heating model to our observations and find that RX J0812.4–3114 has a high thermal LX, at or above the prediction for minimum cooling mechanisms. This suggests that RX J0812.4–3114 either contains a relatively low-mass NS with minimum cooling, or that the system may be young enough that the NS has not fully cooled from the supernova explosion.

Pharmacokinetics of noopept and its active metabolite cycloprolyl glycine in rats

The study of the pharmacokinetics of new drugs and the identification of active metabolites is a necessary step for effective and safe use in the clinical practice. It is especially important for peptide drugs due to their enzymatic instability, low bioavailability and poor permeability through the blood-brain barrier (BBB). The role of endogenous neuropeptides containing cyclic amino acids, proline, pyroglutamic acid, and glycine, in the regulation of memory processes is known as terminal peptide fragments. The development of nootropic drugs based on natural neuropeptides with high pharmacological activity and improved pharmacokinetic properties (enzymatic stability, high bioavailability, and good permeability through the BBB) is an important problem of modern neuropsychopharmacology. Developed drugs – representing short (di- and tri-) peptides appear to meet these requirements. In the Zakusov Research Institute of Pharmacology a nootropic agent noopept (N-phenylacetyl-prolyl-L-glycine ethyl ester), was developed and introduced into medical practice, studies of its pharmacokinetics in ratsrevealed that the noopept metabolite found in the rat plasma and brain, cyclo-prolyl-L-glycine (CPG), differed significantly in its pharmacokinetic parameters from noopept, but at the same time it had similar noopept multi-component spectrum of pharmacological action, namely the influence on higher integrative functions of memory.