Polarization of high-energy emissions from the Crab pulsar

We investigate polarization of high-energy emissions from the Crab pulsar in the frame work of the outer gap accelerator, following previous works of Cheng and coworkers. The recent version of the outer gap, which extends from inside the null charge surface to the light cylinder, is used for examining the synchrotron radiations from the secondary and the tertiary pairs, which are produced outside the gap. We calculate the light curve, the spectrum and the polarization characteristics, simultaneously, by taking into account gyration motion of the particles. The polarization position angle curve and the polarization degree are calculated to compare with the Crab optical data. We demonstrate that the radiations from inside the null charge surface make outer-wing and off-pulse emissions in the light curve, and the tertiary pairs contribute to bridge emissions. The emissions from the secondary pairs explain the main features of the observed light curve and spectrum. On the other hand, both emissions from inside the null charge surface and from the tertiary pairs are required to explain the optical polarization behavior of the Crab pulsar. The energy dependence of the polarization features is expected by the present model. For the Crab pulsar, the polarization position angle curve indicates that the viewing angle of the observer measured from the rotational axis is greater than $90^{\circ}$.Comment: 32pages, 8 figures. Accepted for publication in Ap

GeV detection of HESS J0632+057

HESS J0632+057 is the only gamma-ray binary that has been detected at TeV energies, but not at GeV energies yet. Based on nearly nine years of Fermi Large Area Telescope (LAT) Pass 8 data, we report here on a deep search for the gamma-ray emission from HESS J0632+057 in the 0.1-300 GeV energy range. We find a previously unknown gamma-ray source, Fermi J0632.6+0548, spatially coincident with HESS J0632+057. The measured flux of Fermi J0632.6+0548 is consistent with the previous flux upper limit on HESS J0632+057 and shows variability that can be related to the HESS J0632+057 orbital phase. We propose that Fermi J0632.6+0548 is the GeV counterpart of HESS J0632+057. Considering the Very High Energy (VHE) spectrum of HESS J0632+057, a possible spectral turnover above 10 GeV may exist in Fermi J0632.6+0548, as appears to be common in other established gamma-ray binaries.Comment: 17 pages, 4 figures, 1 table; Accepted for publication in Ap

Monte Carlo direct simulation technique user's manual

User manual for Monte Carlo direct simulation techniqu

Modelling the light curves of PSR B1259-63/LS 2883-II.The effects of anisotropic pulsar wind and Doppler-boosting

PSR B1259-63/LS 2883 is a binary system in which a 48-ms pulsar orbits around a Be star in a high eccentric orbit with a long orbital period of about 3.4 yr. It is special for having asymmetric two-peak profiles in both the X-ray and the TeV light curves. Recently, an unexpected GeV flare was detected by $Fermi$ gamma-ray observatory several weeks after the last periastron passage. In this paper, we show that this observed GeV flare could be produced by the Doppler-boosted synchrotron emission in the bow shock tail. An anisotropic pulsar wind model, which mainly affects the energy flux injection to the termination shock in different orbital phase, is also used in this paper, and we find that the anisotropy in the pulsar wind can play a significant role in producing the asymmetric two-peak profiles in both X-ray and TeV light curves. The X-ray and TeV photons before periastron are mainly produced by the shocked electrons around the shock apex and the light curves after periastron are contributed by the emission from the shock apex and the shock tail together, which result in the asymmetric two-peak light curves.Comment: 5 Fig, accepted by Ap

Comparison of crystal structures and effects of Co substitution in a new member of Fe-1111 superconductor family AeFeAsF(Ae = Ca and Sr): a possible candidate for higher Tc superconductor

We refined crystal structures of newly found members of the Fe-1111 superconductor family, CaFe\_{1-x}Co\_{x}AsF and SrFe\_{1-x}Co\_{x}AsF (x = 0, 0.06, 0.12) by powder synchrotron X-ray diffraction analysis. The tetragonal to orthorhombic phase transitions were observed at ~120 K for unsubstituted CaFeAsF and at ~180 K for unsubstituted SrFeAsF, the transition temperatures agreeing with kinks observed in temperature-dependent resistivity curves. Although the transition temperature decreases, the structural phase transitions were observed below 100 K in both samples of x = 0.06, and finally they were suppressed in the doping level of x = 0.12. The refined structures reveal that distortions of the FeAs4 tetrahedron from the regular tetrahedron likely originate from mismatches in atomic radii among the constituent elements. In this system, the enlarged FeAs4 tetrahedron resulting from larger radius of Sr than that of Ca is flattened along a-b plane, whereas the smaller radius of Ca makes the tetrahedron closer to regular one, and their characteristic shapes are further enhanced by Co substitution. These results suggest that the CaFeAsF compound is a promising candidate for higher-Tc superconductor.Comment: 17 pages, 8 figures, 2 tables, Supplementary information is included at the end of the documen

[OII]3727 Emission from the Companion to the Quasar BR 1202-0725 at z=4.7

Results of a narrow-band imaging for the redshifted [OII]3727 emission around a quasar at z=4.7 obtained with the Subaru telescope and CISCO (a Cassegrain near infrared camera) are presented. A significant emission line is detected in the narrow-band H_2 (v=1-0 S(1)) filter at a location 2.4" northwest from the quasar, where the presence of a companion has been reported in Lyman alpha emission and the rest-frame UV continuum. We identify this line as [OII]3727 emission and confirm that the source really is a companion at z=4.7. The [OII]3727 flux from the companion is estimated to be 2.5 x 10^{-17} erg s^{-1} cm^{-2}. If the companion is a star forming object, the inferred star formation rate is as high as 45-230 M_{solar} yr^{-1} even without assuming the extinction correction. This value is higher than those derived from the Lyman alpha emission or from the UV continuum. Thus, provided that the difference is caused by dust extinction, the extinction corrected star formation rate is calculated to be 45 to 2300 M_{solar} yr^{-1} depending on the assuming extinction curves.Comment: 15 pages including 3 figures. Accepted for publication in PAS

Theory of Stellar Oscillations

In recent years, astronomers have witnessed major progresses in the field of stellar physics. This was made possible thanks to the combination of a solid theoretical understanding of the phenomena of stellar pulsations and the availability of a tremendous amount of exquisite space-based asteroseismic data. In this context, this chapter reviews the basic theory of stellar pulsations, considering small, adiabatic perturbations to a static, spherically symmetric equilibrium. It starts with a brief discussion of the solar oscillation spectrum, followed by the setting of the theoretical problem, including the presentation of the equations of hydrodynamics, their perturbation, and a discussion of the functional form of the solutions. Emphasis is put on the physical properties of the different types of modes, in particular acoustic (p-) and gravity (g-) modes and their propagation cavities. The surface (f-) mode solutions are also discussed. While not attempting to be comprehensive, it is hoped that the summary presented in this chapter addresses the most important theoretical aspects that are required for a solid start in stellar pulsations research.Comment: Lecture presented at the IVth Azores International Advanced School in Space Sciences on "Asteroseismology and Exoplanets: Listening to the Stars and Searching for New Worlds" (arXiv:1709.00645), which took place in Horta, Azores Islands, Portugal in July 201

Nature of a Strongly-Lensed Submillimeter Galaxy SMM J14011+0252

We have carried out near-infrared JHK spectroscopy of a gravitationally lensed submillimeter galaxy SMM J14011+0252 at z=2.565, using OHS and CISCO on the Subaru telescope. This object consists of two optical components, J1 and J2, which are lensed by the cluster Abell 1835. J1 suffers additional strong lensing by a foreground galaxy at z=0.25 in the cluster. The rest-optical H-alpha, H-beta, and [O II]3727 lines are detected in both J1 and J2, and [N II]6548,6583 lines are also detected in J1. A diagnosis of emission-line ratios shows that the excitation source of J1 is stellar origin, consistent with previous X-ray observations. The continua of J1 and J2 show breaks at rest 4000A, indicating relatively young age. Combined with optical photometry, we have carried out model spectrum fitting of J2 and find that it is a very young (~50 Myr) galaxy of rather small mass (~10e8 M_sol) which suffers some amount of dust extinction. A new gravitational lensing model is constructed to assess both magnification factor and contamination from the lensing galaxy of the component J1, using HST-F702W image. We have found that J1 suffers strong lensing with magnification of ~30, and its stellar mass is estimated to be < 10e9 M_sol. These results suggest that SMM J14011+0252 is a major merger system at high redshift that undergoes intense star formation, but not a formation site of a giant elliptical. Still having plenty of gas, it will transform most of the gas into stars and will evolve into a galaxy of < 10e10 M_sol. Therefore, this system is possibly an ancestor of a less massive galaxy such as a mid-sized elliptical or a spiral at the present.Comment: 21 pages, 11 figures. Accepted for publication in Astronomical Journa