Applicability of Relativistic Point-Coupling Models to Neutron Star Physics

Comparing with a wide range of covariant energy density functional models based on the finite-range meson-exchange representation, the relativistic mean-field models with the zero-range contact interaction, namely the relativistic point-coupling models, are still infrequent to be utilized in establishing nuclear equation of state (EoS) and investigating neutron star properties, although comprehensive applications and achievements of them in describing many nuclear properties both in ground and exited states are mature. In this work, the EoS of neutron star matter is established constructively in the framework of the relativistic point-coupling models to study neutron star physics. Taking two selected functionals DD-PC1 and PC-PK1 as examples, nuclear symmetry energies and several neutron star properties including proton fractions, mass-radius relations, the core-crust transition density, the fraction of crustal moment of inertia and dimensionless tidal deformabilities are discussed. A suppression of pressure of neutron star matter found in the functional PC-PK1 at high densities results in the difficulty of its prediction when approaching to the maximum mass of neutron stars. In addition, the divergences between two selected functionals in describing neutron star quantities mentioned above are still large, ascribing to the less constrained behavior of these functionals at high densities. Then it is expected that the constraints on the dense matter EoS from precise and massive modern astronomical observations, such as the tidal-deformabilities taken from gravitational-wave events, would be essential to improve the parameterizing of the relativistic point-coupling models.Comment: To appear in the AIP Proceedings of the Xiamen-CUSTIPEN Workshop on the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave Astronomy, Jan. 3-7, Xiamen, Chin

The hidden strange BcB_{c}-like molecular states

With the chiral unitary approach, we evaluate the hidden strange $B_{c}$-like molecular states of $b\bar{c}s\bar{s}$ systems $\bar{B}_{s}\bar{D}_{s}$, $\bar{B}_{s}^{*}\bar{D}_{s}$, $\bar{B}_{s}\bar{D}_{s}^{*}$, and $\bar{B}_{s}^{*}\bar{D}_{s}^{*}$ coupled to the non-strange channels. The $S$-wave scattering amplitudes are calculated based on the vector meson exchange, four pseudoscalar mesons contact interactions, and four vector mesons contact interactions obtained from the extended local hidden gauge approach. We find six states below the threshold of the most relevant channel. The binding energies of these states are around $1-10$ MeV and the widths are around $0.2-0.7$ MeV. Our research is a supplement to the mass spectra of $B_{c}$-like states, which may be useful for the experimental search in the future.Comment: 15 pages, 8 figure

The energy distribution of relativistic electrons in the kilo-parsec scale jet of M87 with Chandra

The X-ray emission from the jets in Active Galactic Nuclei (AGN) carries important information on the distributions of relativistic electrons and magnetic fields on large scales. We reanalyze archival Chandra observations on the jet of M87 from 2000 to 2016 with a total exposure of 1460 kiloseconds to explore the X-ray emission characteristics along the jet. We investigate the variability behaviours of the nucleus and the inner jet component HST-1, and confirm indications for day-scale X-ray variability in the nucleus contemporaneous to the 2010 high TeV gamma-ray state. HST-1 shows a general decline in X-ray flux over the last few years consistent with its synchrotron interpretation. We extract the X-ray spectra for the nucleus and all knots in the jet, showing that they are compatible with a single power-law within the X-ray band. There are indications of the resultant X-ray photon index to exhibit a trend, with slight but significant index variations ranging from $\simeq 2.2$ (e.g. in knot D) to $\simeq 2.4-2.6$ (in the outer knots F, A, and B). When viewed in a multi-wavelength context, a more complex situation is arising. Fitting the radio to X-ray spectral energy distributions (SEDs) assuming a synchrotron origin, we show that a broken power-law electron spectrum with break energy $E_b$ around $1~(300\mu G/B)^{1/2}$ TeV allows a satisfactorily description of the multi-band SEDs for most of the knots. However, in the case of knots B, C and D we find indications that an additional high energy component is needed to adequately reproduce the broadband SEDs. We discuss the implications and suggest that a stratified jet model may account for the differences.Comment: accepted for publication in A&

Tentative evidence of spatially extended GeV emission from SS433/W50

We analyze 10 years of Fermi-LAT data towards the SS433/W50 region. With the latest source catalog and diffuse background models, the gamma-ray excess from SS433/W50 is detected with a significance of 6{\sigma} in the photon energy range of 500 MeV - 10 GeV. Our analysis indicates that an extended flat disk morphology is preferred over a point-source description, suggesting that the GeV emission region is much larger than that of the TeV emission detected by HAWC. The size of the GeV emission is instead consistent with the extent of the radio nebula W50, a supernova remnant being distorted by the jets, so we suggest that the GeV emission may originate from this supernova remnant. The spectral result of the GeV emission is also consistent with an supernova remnant origin. We also derive the GeV flux upper limits on the TeV emission region, which put moderate constrains on the leptonic models to explain the multiwavelength data.Comment: 7 pages, 4 figures, accepted for publication in A&

Assessment of Resident Physicians in Professionalism, Interpersonal and Communication Skills: a Multisource Feedback

Objective: To assess the internal validity and reliability of a multisource feedback (MSF) program by China Medical Board for resident physicians in China

Categorizing resonances X(1835), X(2120) and X(2370) in the pseudoscalar meson family

Inspired by the newly observed three resonances X(1835), X(2120) and X(2370), in this work we systematically study the two-body strong decays and double pion decays of $\eta(1295)/\eta(1475)$, $\eta(1760)/X(1835)$ and $X(2120)/X(2370)$ by categorizing $\eta(1295)/\eta(1475)$, $\eta(1760)/X(1835)$, X(2120) and X(2370) as the radial excitations of $\eta(548)/\eta^\prime(958)$. Our numerical results indicate the followings: (1) The obtained theoretical strong decay widths of three pseudoscalar states $\eta(1295)$, $\eta(1475)$ and $\eta(1760)$ are consistent with the experimental measurements; (2) X(1835) could be the second radial excitation of $\eta^\prime(958)$; (3) X(2120) and X(2370) can be explained as the third and fourth radial excitations of $\eta(548)/\eta^\prime(958)$, respectively.Comment: 16 pages, 15 figures, 3 tables. Accepted for publication in Phys. Rev.