On The Recently Discovered Pulsations From RX J1856.5-3754

An explanation of the recently discovered 7 s pulsations from the isolated neutron star RX J1856.5-3754 is presented. It is assumed that the real spin period of this source is $\approx1$ s, whereas the observed spin-modulation is caused by the presence of a nearly transverse, very low frequency drift waves in the pulsar magnetosphere. It is supposed that the period of the drift wave is equal to a recently observed one. The simulated lightcurve is plotted, the angular parameters are defined and the value of the pulsed fraction of only $\sim 1.2$ is explained.Comment: 7 pages, 2 figure

Nonthermal emission model of isolated X-ray pulsar RX J0420.0-5022

In this paper, an alternative theoretical interpretation to the generally assumed thermal emission models of the observed X-ray spectrum of isolated pulsar RX J0420.0-5022 is presented. It is well-known that at a pulsar surface, the distribution function of relativistic particles is one-dimensional. However, cyclotron instability causes an appearance of transverse momenta of relativistic electrons, which as a result start to radiate in the synchrotron regime. On the basis of the Vlasov kinetic equation we study the process of quasi-linear difusion (QLD) developed by means of the cyclotron instability. This mechanism enables the generation optical and X-ray emissions on the light cylinder lengthscales. An analysis of the three archival XMM-Newton observations of RX J0420.0-5022, is performed. Considering a different approach to synchrotron emission theory, a spectral energy distribution was obtained, which was in a good agreement with the observational data. A fit to the X-ray spectrum was conducted using both the present synchrotron emission model spectrum absorbed by cold interstellar matter, as well as the generally assumed black-body absorption model

On the very high energy spectrum of the Crab pulsar

In the present paper we construct a self-consistent theory, interpreting the observations of the MAGIC Cherenkov Telescope of the very high energy (VHE) pulsed emission from the Crab pulsar. In particular, on the basis of the Vlasov's kinetic equation we study the process of the quasi-linear diffusion(QLD) developed by means of the cyclotron instability. This mechanism provides simultaneous generation of low (radio) and VHE (0.01-25GeV) emission on the light cylinder scales, in one location of the pulsar magnetosphere. A different approach of the synchrotron theory is considered, giving the spectral index of VHE emission ($\beta=2$) and the exponential cutoff energy (23 GeV) in a good agreement with the observational data.Comment: 8 pages, 0 figure

Contribution of the first K-homology domain of poly(C)-binding protein 1 to its affinity and specificity for C-rich oligonucleotides

Poly-C-binding proteins are triple KH (hnRNP K homology) domain proteins with specificity for single stranded C-rich RNA and DNA. They play diverse roles in the regulation of protein expression at both transcriptional and translational levels. Here, we analyse the contributions of individual αCP1 KH domains to binding C-rich oligonucleotides using biophysical and structural methods. Using surface plasmon resonance (SPR), we demonstrate that KH1 makes the most stable interactions with both RNA and DNA, KH3 binds with intermediate affinity and KH2 only interacts detectibly with DNA. The crystal structure of KH1 bound to a 5′-CCCTCCCT-3′ DNA sequence shows a 2:1 protein:DNA stoichiometry and demonstrates a molecular arrangement of KH domains bound to immediately adjacent oligonucleotide target sites. SPR experiments, with a series of poly-C-sequences reveals that cytosine is preferred at all four positions in the oligonucleotide binding cleft and that a C-tetrad binds KH1 with 10 times higher affinity than a C-triplet. The basis for this high affinity interaction is finally detailed with the structure determination of a KH1.W.C54S mutant bound to 5′-ACCCCA-3′ DNA sequence. Together, these data establish the lead role of KH1 in oligonucleotide binding by αCP1 and reveal the molecular basis of its specificity for a C-rich tetrad

The plasma emission model of RBS1774

In the present paper we construct a self-consistent theory, interpreting the observational properties of RBS1774. It is well known that the distribution function of relativistic particles is one-dimensional at the pulsar surface. However, cyclotron instability causes an appearance of transverse momenta of relativistic electrons, which as a result, start to radiate in the synchrotron regime. We study the process of the quasi-linear diffusion developed by means of the cyclotron instability on the basis of the Vlasov’s kinetic equation. This mechanism provides generation of measured optical and X-ray emission on the light cylinder lengthscales. A different approach of the synchrotron theory is considered, giving the spectral energy distribution that is in a good agreement with the XMM-Newton observational data. We also provide the possible explanation of the spectral feature at 0.7 keV, in the framework of the model

The emission polarization of RX J1856.5-3754

The polarization properties of RX J1856.5-3754 are investigated, based on the plasma emission model presented in previous works. It is shown that if the emission of this source is generated by the synchrotron mechanism, then the X-ray and the optical emission should be linearly polarized and the corresponding degrees of linear polarization are calculated. The change of the position angle through the observable period is investigated. According to the model, the position angle should undergo a full-circle rotation more than once within this period. This unusual behaviour of the position angle is a prediction of the model and its detection would be a strong argument in favour of it. The measurement of the polarization patterns of this source appears to be the most reliable way to make clear its real emission nature

The plasma emission model of RX J1856.5-3754

A spectral analysis of the nearby, isolated neutron star RX J1856.5-3754 is presented. Applying the kinetic approach, the distribution functions of emitting electrons are derived and the entire spectra is fitted. It is found that waves excited by the cyclotron mechanism occur in the radio domain. We confirm that the cyclotron instability is quite efficient, since the estimations show that the time of wave-particle interaction is long enough for particles to acquire perpendicular momentum and generate observed radiation. The lack of rotational modulation is discussed and the pulsar spin period estimate

A Novel Set of Nuclear Localization Signals Determine Distributions of the αCP RNA-Binding Proteins

αCPs comprise a subfamily of KH-domain-containing RNA-binding proteins with specificity for C-rich pyrimidine tracts. These proteins play pivotal roles in a broad spectrum of posttranscriptional events. The five major αCP isoforms are encoded by four dispersed loci. Each isoform contains three repeats of the RNA-binding KH domain (KH1, KH2, and KH3) but lacks other identifiable motifs. To explore the complexity of their respective functions, we examined the subcellular localization of each αCP isoform. Immunofluorescence studies revealed three distinct distributions: αCP1 and αCP2 are predominantly nuclear with specific enrichment of αCP1 in nuclear speckles, αCP3 and αCP4 are restricted to the cytoplasm, and αCP2-KL, an αCP2 splice variant, is present at significant levels in both the nucleus and the cytoplasm. We mapped nuclear localization signals (NLSs) for αCP isoforms. αCP2 contains two functionally independent NLS. Both NLSs appear to be novel and were mapped to a 9-amino-acid segment between KH2 and KH3 (NLS I) and to a 12-amino-acid segment within KH3 (NLS II). NLS I is conserved in αCP1, whereas NLS II is inactivated by two amino acid substitutions. Neither NLS is present in αCP3 or αCP4. Consistent with mapping studies, deletion of NLS I from αCP1 blocks its nuclear accumulation, whereas NLS I and NLS II must both be inactivated to block nuclear accumulation of αCP2. These data demonstrate an unexpected complexity in the compartmentalization of αCP isoforms and identify two novel NLS that play roles in their respective distributions. This complexity of αCP distribution is likely to contribute to the diverse functions mediated by this group of abundant RNA-binding proteins