• Journal of Astronomy and Space Sciences
• /
• v.29 no.1
• /
• pp.51-55
• /
• 2012

A few high-mass X-ray binaries-consisting of an OB star plus compact companion-have been observed by Fermi and ground-based Cerenkov telescopes like High Energy Stereoscopic System (HESS) to be sources of very high energy (VHE; up to 30 TeV) ${\gamma}$-rays. This paper focuses on the prominent ${\gamma}$-ray source, LS 5039, which consists of a massive O6.5V star in a 3.9-day-period, mildly elliptical ($e{\approx}0.24$) orbit with its companion, assumed here to be an unmagnetized compact object (e.g., black hole). Using three dimensional smoothed particle hydrodynamics simulations of the Bondi-Hoyle accretion of the O-star wind onto the companion, we find that the orbital phase variation of the accretion follows very closely the simple Bondi-Hoyle-Lyttleton (BHL) rate for the local radius and wind speed. Moreover, a simple model, wherein intrinsic emission of ${\gamma}$-rays is assumed to track this accretion rate, reproduces quite well Fermi observations of the phase variation of ${\gamma}$-rays in the energy range 0.1-10 GeV. However for the VHE (0.1-30 TeV) radiation observed by the HESS Cerenkov telescope, it is important to account also for photon-photon interactions between the ${\gamma}$-rays and the stellar optical/UV radiation, which effectively attenuates much of the strong emission near periastron. When this is included, we find that this simple BHL accretion model also quite naturally fits the HESS light curve, thus making it a strong alternative to the pulsar-wind-shock models commonly invoked to explain such VHE ${\gamma}$-ray emission in massive-star binaries.

• Journal of Astronomy and Space Sciences
• /
• v.4 no.1
• /
• pp.11-23
• /
• 1987

In dward nova we assume the primary star as a white dwarf and the secondary as the late type star which filled Roche lobe. Mass flow from the secondary star leads to the formation of thin accretion disk around the white dwarf. We use the $\alpha$ parameter as viscosity to maintain the disk form and propose that the outburst in dwarf nova cause the step increase of source term. With these assumptions we solve the basic equations of stellar structure using New-Raphson method. We show the physical parameters like temperature, density, pressure, opacity, surface density, height and flux to the radius of disk. Changing the value of $\alpha$, we compare several parameters when mass flow rate is constant with those of when luminosity of disk is brightest. At the same time, we obtain time-dependent variations of luminosity and mass of disk. We propose the suitable range of $\alpha$is 0.15-0.18 to the difference of luminosity. We compare several parameters of disk with those of the normal late type stars which have the same molecular weight of disk. These show the temperature and pressure of disk are similar to those of normal stars but the density of disk is lower. Maybe the outburst in dwarf nova is due to the variation of the $\alpha$ value instead of increment of mass flow from the secondary star.

• Bulletin of the Korean Mathematical Society
• /
• v.52 no.3
• /
• pp.1035-1046
• /
• 2015

In this work we present some geometric properties (like star-likeness and convexity of order ${\alpha}$ and also close-to-convexity of order ($1+{\alpha}$)/2) for normalized of Lommel functions of the first kind. In order to prove our main results, we use the technique of differential subordinations and some inequalities. Furthermore, we present some applications of convexity involving Lommel functions associated with the Hardy space of analytic functions, i.e., we obtain conditions for the function $h_{{\mu},{\upsilon}}(z)$ to belong to the Hardy space $H^p$.

• Bulletin of the Korean Mathematical Society
• /
• v.55 no.1
• /
• pp.149-163
• /
• 2018

In recent years, the study of slice Dirac operators has attracted more and more attention in the literature. In this paper, Almansitype decompositions for null solutions to the iterated slice Dirac operator and the generalized slice Dirac operator are obtained without a star-like domain centered at the origin. As applications, we investigate Riquier type problems and Dirichlet type problems in the theory of slice monogenic functions.

• Animal Systematics, Evolution and Diversity
• /
• v.26 no.3
• /
• pp.349-351
• /
• 2010

Some asteroid specimens were collected from the subtidal zone near Gapado, Jejudo Island with fishing net on June 2010. Among them, Anseropoda petaloides (Goto, 1914) which belongs to the family Asterinidae of the order Valvatida turned out to be a new record from Korea. Morphological characters of this species collected at 130 m deep are redescribed with photographs. This species is characterized by its very thin body composed of plates imbricated into each other like scales. Twenty four asteroids are currently known from Jejudo Island, Korea.

• International Journal of Contents
• /
• v.1 no.2
• /
• pp.44-47
• /
• 2005

One of the most important characteristics in Hollywood movies is that Hollywood movies have created heroes. But, the meaning of heroes in Hollywood movies is different from proto- typical heroes. America has such a short history, so it doesn't have the mythology. It is also consist of multi-race, culture. Thus, America people, especially governor need something that tie up governed people spiritually. Hollywood film industry has responded about this expectation since 1920's. Hollywood film producers have created mythology and hero like the western genre and Rambo. Now days, America, as only super power, wants to spread it's mythology and heroes over the world. That is cultural Imperialism.

• Communications of the Korean Mathematical Society
• /
• v.37 no.1
• /
• pp.113-123
• /
• 2022

In the present paper, we introduce the subclasses 𝔅_1Σ(𝜇), B_1Σ(𝜇, 𝛾) and U_Σ(𝜇, 𝛾) of bi-univalent Bazilevič functions which are defined in the open unit disk 𝔻. Further, we obtain sharp estimates on initial coefficients a₂, a₃, a₄ and also sharp estimate on the Fekete-Szegö functional a₃ - ka²₂ for the functions belong to these subclasses.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.1
• /
• pp.33.3-34
• /
• 2021

In LCDM universe, large, massive structures, like galaxy clusters, grow through the successive accretion/mergers of smaller structures. Therefore, at high redshift, unlike local, it is expected that there would be plenty of galaxy clusters which are still growing. Here, we report the discovery of a high-redshift (z~1) galaxy cluster which is in its active formation stage. This cluster is well connected to the large scale overdense environment and contains high fraction of star-forming galaxies, providing a good example supporting our previously suggested 'Web-feeding model'.

• The Bulletin of The Korean Astronomical Society
• /
• v.43 no.1
• /
• pp.55.1-55.1
• /
• 2018

Studies on rotation-powered pulsars with strong surface magnetic field may help us clarify the unclear link between magnetars and canonical radio pulsars because the magnetar-like emission is expected to be observed. PSR J1119-6127 associated with SNR G292.2-0.5 has a high magnetic field of $4.1{\times}1013$ gauss, and a young characteristic age of ~1700 years can be served as the good candidate to compare with magnetars and rotation-powered pulsars. The glitch accompanied by the radiative changes detected in 2007 is the first case we observed for a rotationally powered radio pulsar. This pulsar experienced magnetar-like outbursts in mid. 2016, similar to the 2006 transition occurred on the other radio-quiet rotation-powered pulsar with strong surface magnetic field, PSR J1846-0258. In this talk, I'll report the investigation with X-ray and gamma-ray data of this magnetar-like pulsar. A sudden decrease in the gamma-ray emission at the GeV band was detected immediately after the X-ray outburst. Accompanying with the disappearance of the radio pulsation, the gamma-ray pulsation cannot be resolved as well after the outburst. We tried to derive the timing behavior and some intriguing features of this pulsar in this work corresponding to the outburst using the Swift data, NuSTAR and XMM observations.

• Korean Journal of Food Science and Technology
• /
• v.32 no.3
• /
• pp.706-712
• /
• 2000

The superoxide dismutase(SOD)-like activities for 26 kinds of herbs and spices and 10 kinds of instant curry products were determined by measuring their abilites to reduce nitroblue tetrazolium. All samples showed the SOD-like activities. Rosemary, cassia, tarragon, allspice, oregano, bay leaves, basil, marjoram, thyme and star anise had higher activities than $10^5\;unit/g$ and clove had highest activity of $232,143{\pm}19.989\;unit/g$. The SOD-like activities for 10 kinds of instant curry products were in the range of $400{\sim}700\;unit/g$ when measured after heat treatment at $100^{\circ}C$ for 10 min. The water extracts of spices, herbs and curries were obtained by heat treatments of $25^{\circ}C$ for 60 min or $100^{\circ}C$ for 10 min, and their nitrite scavenging activity was measured at different pH conditions(1.2, 4.2 or 6.0). The nitrite scavenging activities were higher at acidic pH. However, the effects were not different from two heat treatments. The water extracts from cassia, bay leaves, allspices, oregano, staranise, rosemary, clove and tarragan had high nitrite scavenging activity(>90%) when they were measured at pH 1.2, and those from clove was highest $(97.58{\pm}0.88%)$. The pure curry used as raw materials for instant curry products had the nitrite scavenging activity in the range of $50{\sim}60%$ at pH 1.2 and the activity was not changed during the aging period$(0{\sim}12weeks)$. The ten brands of instant curry products had the nitrite scavenging activities of $12{\sim}28%$ at pH 1.2