• 천문학회보
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• 제46권2호
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• pp.52.1-52.1
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• 2021

Low mass X-ray binary(LMXB) 중 accretion disk가 존재하지 않으며 매우 작은 질량 (1 ≪ M_⊙)의 동반성을 가지는 pulsar binary system에서 중성자별과 동반성의 항성풍은 상호작용하여 intrabinary shock(IBS)을 형성한다. 이곳에서 입자들은 상대론적으로 가속되어 싱크로트론 복사를 방출한다고 생각된다. 이 복사는 X-선 영역으로 관측되며 이때 관측된 X-선 궤도 광도곡선은 IBS의 모양에 따라 달라진다. 우리는 IBS의 X-선 복사 과정을 모델화하여 shock의 모양과 내부의 전자 특성을 파악하고, 광학 관측을 통해 얻은 orbital parameter와 비교하며 binary의 geometry를 보다 정확히 이해하고자 한다. 이 발표에서는 다양한 pulsar binary system의 Chandra, XMM 그리고 NuSTAR의 X-선 관측 데이터에 IBS 모델을 적용해보고 IBS와 binary의 geomerty를 분석한 결과를 제시한다.

• 천문학회보
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• 제46권2호
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• pp.45.2-45.2
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• 2021

Merging of two supermassive black holes would generate gravitational waves that can be detected by the Pulsar Timing Array (PTA) in the nHz band. In order to assess the plausibility of GW detection with PTA and to develop the data analysis scheme, it is important to understand the underlying properties of black holes and black hole binaries. In this work, we present mass and redshift distributions of black hole mergers using the Horizon Run 5 (HR5) data and discuss their implications for GW detection. We find a general conjecture about the black hole merger tree is true with the Horizon Run 5. For example, a) relatively lighter black holes merge at higher redshifts and b) binary mergers do contribute to the formation of more massive black holes toward low redshifts. We also present our plan to use the black hole properties extracted from the HR5 data in order to generate simulated GW signals to be injected into actual PTA data analysis pipelines. Mass and distance obtained from the HR5 would be key ingredients to generate a more realistic PTA source data set.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1998년도 IUMRS-ICEM ABSTRACT BOOK
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• pp.79.3-79
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• 1998

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 1994년도 한국우주과학회보 제3권2호
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• pp.23-23
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• 1994

No Abstract. See Full-text

• 천문학논총
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• 제15권1호
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• pp.1-13
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• 2000

Since Goldreich and Julian's pioneering work in 1969, the pulsar magnetosphere theory has been dramatically developed for theorists to possess an elegant axisymmetric, stationary model. Based on this development the black hole magnetosphere theory has also been established in the last 30 years. Such theoretical developments will be reviewd equation by equation in this paper.

• 천문학회보
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• 제43권2호
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• pp.43.1-43.1
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• 2018

Young pulsar wind nebulae, powered by energetic central pulsars, are often observed as bright extended sources in the X-ray band. They are believed to accelerate electrons and positrons to very high energy and can possibly explain the positron excess observed by Fermi and AMS. The electron distribution in these PWNe can be best studied by X-ray satellites because emission in the X-ray band is produced by direct synchrotron radiation of the electrons and positrons. We present NuSTAR studies of PWNe and discuss the implication. Future studies to help further our understanding of particle acceleration will be briefly discussed.

• 천문학회보
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• 제45권1호
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• pp.53.1-53.1
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• 2020

We present Herschel Space Observatory far-IR observations of the supernova remnant(SNR) G21.5-0.9. We search PACS-IFU data for 63um [O I], 88um [O III], 157um [C II] emission lines and detect the [O II] and the [C II]. We then produce emission line maps to check the spatial distribution of the elements. We compare the maps to Radio, IR-photometrics, and X-ray images in order to understand interaction of the ejecta with the Pulsar Wind Nebula(PWN) and physical environment in the SNR.

• 천문학회보
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• 제46권2호
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• pp.52.3-52.3
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• 2021

Timing analysis에서 pulsar 또는 magnetar의 pulsation 측정은 background 또는 주변의 다른 source의 영향으로 매우 세밀하게 측정을 진행해야 할 수 있다. 하지만 gamma-ray 영역에서는 instrument의 낮은 imaging resolution으로 인해 likeihood 분석법을 사용하며, pulsation측정의 sensitivity를 향상시키기 위해 weighted H-test를 적용하고 있다. weighted H-test는 Instrument의 responses와 source, background의 radiational properties를 이용하여 각 photon의 probability를 계산하고 이를 weight하여 pulsation detection의 sensitivity를 향상시키는 방법으로 이번 연구를 통해 이를 X-ray에서 적용할 수 있도록 확장하였다. 이번 발표에서는 X-ray 데이터 중 상대적으로 낮은 imaging resolution을 갖는 XMM-Newton data에 weighted H-test를 적용하여 기존의 H-test와의 차이를 비교해보고, weighted H-test가 갖는 이점에 대하여 논의하고자 한다.

• Journal of Astronomy and Space Sciences
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• 제30권2호
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• pp.91-94
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• 2013

We use the outer gap model to explain the spectrum and the energy dependent light curves of the X-ray and soft ${\gamma}$-ray radiations of the spin-down powered pulsar PSR B1509-58. In the outer gap model, most pairs inside the gap are created around the null charge surface and the gap's electric field separates the opposite charges to move in opposite directions. Consequently, the region from the null charge surface to the light cylinder is dominated by the outflow current and that from the null charge surface to the star is dominated by the inflow current. We suggest that the viewing angle of PSR B1509-58 only receives the inflow radiation. The incoming curvature photons are converted to pairs by the strong magnetic field of the star. The X-rays and soft ${\gamma}$-rays of PSR B1509-58 result from the synchrotron radiation of these pairs. The magnetic pair creation requires a large pitch angle, which makes the pulse profile of the synchrotron radiation distinct from that of the curvature radiation. We carefully trace the pulse profiles of the synchrotron radiation with different pitch angles. We find that the differences between the light curves of different energy bands are due to the different pitch angles of the secondary pairs, and the second peak appearing at E > 10 MeV comes from the region near the star, where the stronger magnetic field allows the pair creation to happen with a smaller pitch angle.

• 천문학회지
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• 제29권spc1호
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• pp.151-154
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• 1996

We examine the observations of large-scale magnetic fields in the Universe. We begin at the largest scale with clusters of galaxies and work our way down through galaxies and finally to the Milky Way. on which we concentrate in detail. We examine the observations of the Galactic magnetic field, and their interpretation, under the philosophy that the Galactic magnetic field is like that in other spiral galaxies. We use pulsar data. diffuse Galactic synchrotron emission, and starlight polarization data to discuss the Galaxy's global magnetic configuration and the uniform ($B_u$), random ($B_r$), and total ($B_t$) components of the field strength. We find disagreement among conclusions derived from the various data sets and argue that the pulsar data are not the best indicator for large-scale Galactic field. Near the Solar circle, we find that the azimuthal average of $B_t$ is 4.2$\mu$G and we adopt $B_u\~$2.2 and $B_r\~3.6{\mu}G$. $B_t$ is higher in spiral arms, reaching $\~5.9{\mu}G$. $B_t$ is higher for smaller $R_{Gal}$, reaching $\~8.0{\mu}G$ for $R_{Gal}$ = 4.0 kpc. The pattern of field lines is not concentric circles but spirals. The inclination of the magnetic spiral may be smaller than that of the Galaxy's spiral arms if our sample, which refers primarily to the interarm region near the Sun, is representative. However, it is not inconceivable that the local field lines follow the Galaxy's spiral pattern, as is observed in external galaxies.