117346945
Population study for gamma-ray pulsars: (III) Radiation characteristics and viewing geometry
We have performed a Monte-Calro simulation for Galactic population of pulsars and for the $\gamma$-ray observations. We apply outer gap model for the $\gamma$-ray emission process, and study the radiation characteristics as a function of the magnetic inclination angle $(\alpha)$ and the Earth viewing angle ($\zeta$). In our model, the $\gamma$-ray flux and the spectral cut-off energy tend to decrease as the inclination and viewing angles deviate from $90^{\circ}$. The emerging spectrum above 100 MeV becomes soft with a photon index $p\sim 1.8-2$ for $\zeta \rightarrow 90^{\circ}$ and $p\sim 1.2-1.3$ for $\zeta \ll 90^{\circ}$. Our simulation predicts that the pulsars with larger inclination angles ($\alpha=70-90^{\circ}$) and larger viewing angles ($\zeta=70-90^{\circ}$) have been preferentially detected by the $Fermi$ $\gamma$-ray telescope, and hence the observed pulse profiles of the $\gamma$-ray pulsars have the double peak structure rather than single peak. In the simulation, most $\gamma$-ray millisecond pulsars are categorized as the radio-quiet $\gamma$-ray pulsars, because its radio fluxes are under the sensitivities of the major radio surveys. Even we drastically increase the radio sensitivity by a factor of ten, the number of radio-selected millisecond pulsars detected by the $Fermi$ ten years observations is still much less than the expected $\gamma$-ray-selected millisecond pulsars, indicating the radio-quiet millisecond pulsars must contribute to the $Fermi$ unidentified sources and/or the $\gamma$-ray background radiations. The Unique radiation properties of the low-efficient $\gamma$-ray pulsar, PSR J0659+1414, can be explained by the present our gap model with a viewing geometry of $\alpha\sim \zeta=40^{\circ}-50^{\circ}$.
5742840
Crystallization in the Thin and Ultrathin Films of Poly(ethylene-vinyl acetate) and Linear Low-Density Polyethylene
The crystallization of poly(ethylene−vinyl acetate) and linear low-density polyethylene (LLDPE) films spun-cast from the polymer/toluene solutions with as-cast thickness from 460 to 10 nm was studied. The lamellar thickness was measured using small-angle X-ray scattering (SAXS) and found to increase from 14 to 21 nm for films thinner than 100 nm. The morphology of LLDPE measured by scanning probe microscopy (SPM) showed an edge-on lamellae for the films thicker than 30 nm and flat-on lamellae for the films thinner than 15 nm. A pseudo-“shish-kebab” tiny crystal structure was observed in between the larger lamellae. Crystallinity was confirmed using attenuated total reflectance−Fourier transformed infrared spectroscopy (ATR-FTIR) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The shear modulation force microscopy technique (SMFM) was used to measure the melting point, Tm, which was found to decrease for films thinner than 100 nm. The rate of decrease was a function of the annealing pr...
10177650
Clarification of the three-body decay of 12C (12.71 MeV).
Using beta decays of a clean source of 12N produced at the IGISOL facility, we have measured the breakup of the 12C (12.71 MeV) state into three alpha particles with a segmented particle detector setup. The high quality of the data permits solving the question of the breakup mechanism of the 12.71 MeV state, a longstanding problem in few-body nuclear physics. Among existing models, a modified sequential model fits the data best, but systematic deviations indicate that a three-body description is needed.
22794424
Dipole and spin-dipole resonances in charge-exchange reactions on 12C.
The [sup 12]C([ital n],[ital p])[sup 12]B reaction was studied using the white neutron source at the Los Alamos Meson Physics Facility/Weapon Neutron Research Center with a continuous incident neutron energy from 60 to 260 MeV. Double differential cross sections were measured in the angular range 11[degree][le][theta][sub lab][le]37[degree]. Using the neutron time-of-flight facility at the Indiana University Cyclotron Facility, we also studied the [sup 12]C([ital p],[ital n])[sup 12]N reaction at [ital E][sub [ital p]]=186 MeV and the [sup 12]C([ital [rvec p]],[ital [rvec n]])[sup 12]N reaction at [ital E][sub [ital [rvec p]]]=160 and 186 MeV. Double differential cross sections were measured between [theta][sub lab]=0[degree] and [theta][sub lab]=50[degree] in 5[degree] steps. Spin observables [ital D][sub [ital N][ital N]], [ital A][sub [ital Y]], and [ital P] were measured at [theta][sub lab]=5[degree],9[degree],13[degree] with [ital E][sub [ital [rvec p]]]=160 MeV and [theta][sub lab]=15[degree],20[degree] with [ital E][sub [ital [rvec p]]]=186 MeV. Angular distributions of differential cross section and spin observables for low-lying transitions in the residual nuclei are compared with disorted-wave impulse approximation (DWIA) calculations. A multipole decomposition analysis was performed to study the giant dipole and giant spin-dipole resonances. The contributions of the quasifree reaction in the giant resonance region was subtracted. The empirical results ofmore » energy distributions for dipole ([Delta][ital L]=1) transition are compared with DWIA calculations using nuclear structure information obtained with a conventional shell model and also with a random phase approximation.« less
1289258
Energetic electrons associated with magnetic reconnection in the magnetic cloud boundary layer.
Here is reported in situ observation of energetic electrons (∼100-500 keV) associated with magnetic reconnection in the solar wind by the ACE and Wind spacecraft. The properties of this magnetic cloud driving reconnection and the associated energetic electron acceleration problem are discussed. Further analyses indicate that the electric field acceleration and Fermi-type mechanism are two fundamental elements in the electron acceleration processes and the trapping effect of the specific magnetic field configuration maintains the acceleration status that increases the totally gained energy.
120316681
Experimental results of the betatron sum resonance
The experimental observations of motion near the betatron sum resonance, /spl nusub x/+2/spl nusub z/=13, are presented. A fast quadrupole (Panofsky-style ferrite picture-frame magnet with 8 pulsed power supplies) producing a betatron tune shift of the order of 0.03 at rise time of 1 /spl mu/s was used. This quadrupole was used to produce betatron tunes which jumped past and then crossed back through a betatron sum resonance line. The beam response as function of initial betatron amplitudes were recorded turn by turn. The correlated growth of the action variables, J/sub x/ and J/sub z/, was observed. The phase space plots in the resonance frame reveal the features of particle motion near the nonlinear sum resonance region.<<ETX>>
120804729
Gravitational lensing effects on parameter estimation in gravitational wave detection with advanced detectors
The gravitational lensing effect is important to the detection of electromagnetic signals in astrophysics. The gravitational wave lensing effect has also been found significant to gravitational wave detection in the past decade. Recent analysis shows that the lensing events for advanced detectors could be quite plausible. The black holes in our Milky Way Galaxy may play the role of lens objects. These facts motivate us to study the lensing effects on gravitational wave signals for advanced detectors. Taking advanced LIGO and Einstein Telescope for examples, we investigate the lensing effects on the parameter extraction of gravitational wave signals. Using the Markov chain Monte Carlo simulation together with matched filtering methods, we find that the lensing effect for a lens object with small mass is negligible. But when the mass of the lens object increases to larger than 1000M(circle dot) the lensing effect becomes important. Using the template without lensing corrections would result in loss of signal detections. In contrast if we consider templates with lensing effects, the lensed signal may provide much information about the lens black hole. These facts may give us a new way to determine the parameters of the lensing object. For example, this kind of signal may also help us estimate the mass and the distance of the supermassive black hole hosted at the center of our Galaxy.
119206435
Search for the weak decays $J/\psi \to D^{(*)}_{s}e\nu_{e}$
Using a sample of $2.25\times 10^8$ $J/\psi$ events collected with the BESIII detector at the BEPCII collider, we search for the $J/\psi$ semi-leptonic weak decay $J/\psi \to D^{-}_{s} e^{+}\nu_{e}+c.c.$ with a much higher sensitivity than previous searches. We also perform the first search for $J/\psi \to D^{*-}_{s} e^{+}\nu_{e}+c.c.$ No significant excess of a signal above background is observed in either channel. At the $90\%$ confidence level, the upper limits are determined to be $\mathcal{B}(J/\psi \to D^{-}_{s}e^{+}\nu_{e}+c.c.)<1.3\times10^{-6}$ and $\mathcal{B}(J/\psi \to {D^{*}_{s}}^{-}e^{+}\nu_{e}+c.c.)<1.8\times10^{-6}$, respectively. Both are consistent with Standard Model predictions.
145039581
Contribution of starburst mergers at z ∼ 1 to the strong evolution of infrared and submillimeter deep surveys
Recent far-infrared and submillimetre waveband observations revealed a large number of Ultraluminous Infrared Galaxies (ULIGs) with infrared luminosities >10 L . These sources are proposed to lie at redshifts above one, and in normally interacting systems with very dusty environments. We discussed in a previous paper that a population with a fast evolving infrared burst phase triggered by gas-rich mergers at z ∼ 1 predicted successfully the steep slope of faint IRAS 60 μm source counts within the flux range of 100 mJy ∼ 1 Jy, still leaving the infrared background level at this wavelength compatible with the upper limit from recent high energy TeV γ ray detection of Mrk 501. To extend the model to mid and far infrared wavelengths, we adopt a reasonable template spectral energy distribution typical for nearby-infrared-bright starburst galaxies (Lir <= 10 12 L ), such as Arp 220. We construct the SED for the dusty starburst mergers at z ∼ 1 by a simple dust extinction law and a thermal continuum assumption for the far-infrared emission. Since the radiation process at mid-infrared for these starburst merging systems is still uncertain, we assume it is similar to the MIR continuum of Arp 220, but modify it by the observed flux correlation of ULIGs from IRAS and ISOCAM deep surveys. We show in this paper that the strong evolution of the European Large Area ISO Survey (ELAIS) at 90μm, ISO 170μm and the Submillimeter deep survey at 850μm could be sufficiently accounted for by such an evolutionary scenario, especially the hump of the ISOCAM 15μm source count around 0.4 mJy. From current best fit results, we find that the dust temperature of those extremely bright starburst merging system at z ∼ 1 would be higher than that of Arp 220 for a reconciliation of the multi-wavelength infrared deep surveys. We thus propose that the infrared burst phase of dusty starburst galaxies or AGNs from gas-rich mergers at z ∼ 1 could contribute significantly to the strong evolution of the IRAS 60μm, the ISO 15μm, 90μm, 170μm, as well as the SCUBA 850μm number counts, while being compatible with the current observational limits of the cosmic infrared background and the redshift distributions. The major difference of our current model prediction is that we see a fast convergence of the differential number counts at 60μm below 50 mJy, which is about a factor of two brighter than other model predictions. Future infrared satellites like Astro-F or SIRTF would give strong constraints to the models.
117043476
Superfluidity of {Lambda} hyperons in neutron stars
We study the {sup 1}S{sub 0} superfluidity of {Lambda} hyperons in neutron star matter and neutron stars. We use the relativistic mean field (RMF) theory to calculate the properties of neutron star matter. In the RMF approach, the meson-hyperon couplings are constrained by reasonable hyperon potentials that include the updated information from recent developments in hypernuclear physics. To examine the {sup 1}S{sub 0} pairing gap of {Lambda} hyperons, we employ several {Lambda}{Lambda} interactions based on the Nijmegen models and used in double-{Lambda} hypernuclei studies. It is found that the maximal pairing gap obtained is a few tenths of a MeV. The magnitude and the density region of the pairing gap are dependent on the {Lambda}{Lambda} interaction and the treatment of neutron star matter. We calculate neutron star properties and find that whether the {sup 1}S{sub 0} superfluidity of {Lambda} hyperons exists in the core of neutron stars mainly depends on the {Lambda}{Lambda} interaction used.
8010206
CHANDRA STUDY OF X-RAY POINT SOURCES IN THE EARLY-TYPE GALAXY NGC 4552 (M89)
We present a Chandra ACIS study of the early-type galaxy NGC 4552. We detect 47 X-ray point sources, most of which are likely low-mass X-ray binaries (LMXBs), within four effective radii (Re). The brightest X-ray source coincides with the optical, UV, and radio center of the galaxy and shows variability on >1 hr timescales, indicating the possible existence of a low-luminosity active galactic nucleus (AGN). The 46 off-center sources and the unresolved point sources contribute about 29% and 20% to the total luminosity of the galaxy, respectively. We find that after correcting for the incompleteness at the low-luminosity end, the observed cumulative X-ray luminosity function (XLF) of the off-center sources is best fitted by a broken power-law model with a break at Lb = 4.4 × 1038 ergs s-1. We identified 210 globular cluster (GC) candidates in a HST WFPC2 optical image of the galaxy's central region. Of the 25 off-center LMXBs that fall within the WFPC2 field of view, 10 sources are coincident with a GC. Thus, the fraction of the GCs hosting bright LMXBs and the fraction of the LMXBs associated with GCs are 4.8% and 40%, respectively. In the V and I bands, the GCs hosting bright LMXBs are typically 1-2 mag brighter than the GCs with no detected LMXBs. There are about 1.9 ± 0.4 times as many LMXBs in the red, metal-rich GCs as there are in the blue, metal-poor ones. We find no obvious difference between the luminosity distributions of LMXBs in GCs and in the field, but the cumulative spectrum of the LMXBs in GCs tends to be softer than that of the LMXBs in field. We detected three X-ray sources that have isotropic luminosities larger than 1039 ergs s-1. Only one of these is located in the joint Chandra-HST field and is found to be associated with a GC. By studying its ACIS spectra we infer that the this may be a candidate black hole system with a mass of 15-135 M☉. One of the other sources with a luminosity brighter than 1039 ergs s-1 reveals temporal variations in brightness on timescales greater than 1 hr.