• Title/Summary/Keyword: astronomy-X-ray

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An Application of Hilbert-Huang Transform on the Non-Stationary Astronomical Time Series: The Superorbital Modulation of SMC X-1

  • Hu, Chin-Ping;Chou, Yi;Wu, Ming-Chya;Yang, Ting-Chang;Su, Yi-Hao
    • Journal of Astronomy and Space Sciences
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    • v.30 no.2
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    • pp.79-82
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    • 2013
  • We present the Hilbert-Huang transform (HHT) analysis on the quasi-periodic modulation of SMC X-1. SMC X-1, consisting of a neutron star and a massive companion, exhibits superorbital modulation with a period varying between ~40 d and ~65 d. We applied the HHT on the light curve observed by the All-Sky Monitor onboard Rossi X-ray Timing Explorer (RXTE) to obtain the instantaneous frequency of the superorbital modulation of SMC X-1. The resultant Hilbert spectrum is consistent with the dynamic power spectrum while it shows more detailed information in both the time and frequency domains. According to the instantaneous frequency, we found a correlation between the superorbital period and the modulation amplitude. Combining the spectral observation made by the Proportional Counter Array onboard RXTE and the superorbital phase derived in the HHT, we performed a superorbital phase-resolved spectral analysis of SMC X-1. An analysis of the spectral parameters versus the orbital phase for different superorbital states revealed that the diversity of $n_H$ has an orbital dependence. Furthermore, we obtained the variation in the eclipse profiles by folding the All Sky Monitor light curve with orbital period for different superorbital states. A dip feature, similar to the pre-eclipse dip of Her X-1, can be observed only in the superorbital ascending and descending states, while the width is anti-correlated with the X-ray flux.

FUV Spectral Images of the Vela Supernova Remnant: Comparisons with X-ray and $H{\alpha}$ images

  • Kim, Il-Joong;Seon, Kwang-Il;Min, Kyoung-Wook;Han, Wonyong;Edelstein, Jerry
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.2
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    • pp.99.2-99.2
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    • 2012
  • We updated the far-ultraviolet (FUV) spectral images of the entire Vela supernova remnant (SNR) using newly processed FIMS/SPEAR data. In the present study, we compare the newly produced FUV images with the X-ray and $H{\alpha}$ images, and examine how the Vela SNR evolves and interacts with the ambient medium on a global scale. The comparison with X-ray images has revealed a FUV filamentary feature corresponding with the boundary of the northeast-southwest asymmetry of the X-ray shell. The relatively low O IV] ${\lambda}1404$ to O III] ${\lambda}{\lambda}1661$, 1666 ratio estimated on the FUV filament is compatible with the previous proposal that the observed asymmetry of the Vela SNR could be due to the ${\gamma}2$ Velorum stellar wind bubble (SWB). The southwest FUV features surrounding a faint extended X-ray region are characterized as the region where the Vela SNR is interacting slightly stronger with ambient mediums within the dim X-ray southwest section. From a comparison with the $H{\alpha}$ image, we identify a ring-like $H{\alpha}$ feature overlapped with an extended hot X-ray feature of similar size and two local peaks of C IV ${\lambda}{\lambda}1548$, 1551 emission. Their morphologies are consistent with the expected shape when the $H{\alpha}$ ring is in direct contact with the near or far side of the Vela SNR. We suggest that the B3V-type star HD 76161 found at the center of the $H{\alpha}$ ring would be the exciting source of the H II region.

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A NEAR REAL-TIME FLARE ALERTING SYSTEM BASED ON GOES SOFT X-RAY FLUX

  • MOON Y.-J.;PARK Y. D.;SEONG H.-C.;LEE C.-W.;SIM K. J.;YUN H. S.
    • Journal of The Korean Astronomical Society
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    • v.33 no.2
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    • pp.123-126
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    • 2000
  • We have developed a near real-time flare alerting system which (1) downloads the latest GOES-l0 1-8 ${\AA}$ X-ray flux 1-min data by an automated ftp program and shell scripts, (2) produces a beep sound in a simple IDL widget program when the flux is larger than a critical value, and (3) makes it possible to do a wireless alerting by a set of portable transceivers. Thanks to the system, we have made successful Ha flare observations by the Solar Flare Telescope in Bohyunsan Optical Astronomy Observatory. This system is expected to be helpful for ground-based flare observers.

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Hydrodynamics Simulation of the Off-Axis Cluster Merger Abell 115

  • Lee, Wonki;Kim, Mincheol;Jee, M. James
    • The Bulletin of The Korean Astronomical Society
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    • v.43 no.1
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    • pp.60.3-61
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    • 2018
  • Abell 115 is a renowned cluster merger at z=0.197. It exhibits an asymmetric X-ray distribution with cometary tails and a megaparsec-sized radio relic stretching in the northeastern direction from the core of the northern cluster. Many observations have concluded that this cluster merger has a large impact parameter, but there has been no numerical analysis on the structure of Abell 115. In this study, we simulate Abell 115 with Gadget2 N-body/SPH code to reproduce the X-ray and weak lensing features of Abell 115. We find a new plausible merger scenario of Abell 115, wherein the northern cluster is currently in an outgoing phase. The predicted X-ray emission has a similar morphology to the observed tail of the northern cluster. However, in order to reproduce the observed line-of-sight velocity and projected distance while maintaining the two systems gravitationally bound, the system should possess a large projection angle, which makes the shock look considerably more diffused than the observed radio relic.

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THE X-RAY EMISSION FROM EARLY TYPE GALAXIES

  • Kim, Dong-Woo
    • Publications of The Korean Astronomical Society
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    • v.7 no.1
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    • pp.63-69
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    • 1992
  • We have systematically investigated the X-ray spectra of normal galaxies, by using the Imaging Proportional Counter (IPC) data in the Einstein data base. We employed the X-ray color-color plot as well as the standard model fitting method which requires higher signal to noise ratio. We discuss X-ray emission mechanisms in terms of their spectral properties and the signature of cooling flows which are most likely present in X-ray bright early type galaxies. On the average, fits to absorbed thermal spectra show that the X-ray emission temperature of spirals is higher than that of ellipticals. This is consistent with our understanding that accreting binaries are a major X-ray source in spirals, while extended gaseous halos are present in ellipticals. The emission temperature becomes lower with increasing X-ray to optical luminosity ratio in E and S0 galaxies. This result is what we would expect if the emission of X-ray faint early type galaxies consists of a large evolved stellar component, while the gaseous emission becomes dominant in X-ray brighter galaxies. We also find a cool, self-absorbed core in some early type galaxies, which directly indicates the presence of cooling flows in such galaxies.

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Infrared Supernova Remnants and Their Infrared to X-ray Flux Ratios

  • Koo, Bon-Chul;Lee, Jae-Joon;Seok, Ji-Yeon;Jeong, Il-Gyo;Kim, Hyun-Jeong
    • The Bulletin of The Korean Astronomical Society
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    • v.40 no.2
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    • pp.34.3-35
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    • 2015
  • Recent high-resolution infrared space missions have revealed supernova remnants (SNRs) of diverse morphology in far infrared (FIR), often very different from their X-ray appearance. This suggests that the FIR emission from SNRs could be of different origins. For a sample of 20 Galactic SNRs, we examine the correlation between their FIR and X-ray properties and explore the origin of the FIR emission. We find that the SNRs with very different FIR and X-ray morphology have relatively large infrared-to-X-ray (IRX) flux ratios. We argue that the FIR emission in these SNRs is likely mainly from dust grains radiatively-heated by shock radiation. For SNRs with similar IR and X-ray morphology, the FIR emission of which is probably mostly from dust grains collisionally heated by hot plasma, we compare their IRX flux ratios with theoretical ratios from a model incorporating time-dependent dust destruction and non-equilibrium ionization cooling behind SNR shock, and discuss the implications of our result.

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A correlation analysis about properties of quiescence magnetar

  • Seo, Jiwoo;Lee, Jaewon;An, Hongjun
    • The Bulletin of The Korean Astronomical Society
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    • v.46 no.2
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    • pp.52.2-52.2
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    • 2021
  • 우리는 quiescent state magnetar의 물리적 특성을 연구하기 위해 복사특성이 잘 알려진 24개의 대상을 선정하였고 가장 어두운 시기(quiescent state)의 Chandra와 XMM-Newton의 X-ray 관측 데이터를 분석하여 복사특성과 시간 특성을 측정하였다. 이 측정을 이용하여 복사특성과 시간 특성 사이의 여러 경우에 대해 상관관계를 분석하였다. 그 결과 기존에 높은 상관관계를 갖는 것으로 알려진 표면 자기장(Bs)과 흑체복사 광도(LBB), Bs와 X-ray photon index (ΓX) 관계를 더 많은 magnetar에 대하여 재확인하였으며, spin-down rate (Ṗ)와 LBB, characteristic age (𝜏c)와 LBB의 새로운 유의미한 관계를 찾았다. 또한 magnetar의 pulsed fraction (PF)과 흑체복사 반경(RBB), PF와 ΓX, 그리고 Ṗ과 ΓX가 서로 상관되어 있다는 단서를 확인하였다.

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High Mass X-ray Binary and IGOS with IGRINS

  • Chun, Moo-Young;Moon, Dae-Sik;Jeong, Ueejeong;Yu, Young Sam
    • The Bulletin of The Korean Astronomical Society
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    • v.39 no.2
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    • pp.95-95
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    • 2014
  • The mass measurement of neutron stars or black holes is of fundamental importance in our understanding of the evolution of massive stars and core-collapse supernova explosions as well as some exotic physics of the extreme conditions. Despite the importance, however, it's very difficult to measure mass of these objects directly. One way to do this, if they are in binary systems, to measure their binary motions (i.e., Doppler shifts) which can give us direct information on their mass. Recently many new highly-obscured massive X-ray binaries have been discovered by new hard X-ray satellites such as INTEGRAL and NuSTAR. The new highly-obscured massive X-ray binaries are faint in the optical, but bright in the infrared with many emission lines. Based on the near-infrared spectroscopy, one can first understand the nature of stellar companions to the compact objects, determining its spectral types and luminosity classes as well as mass losses and conditions of (potential) circumstellar material. Next, spectroscopic monitoring of these objects can be used to estimate the mass of compact objects via measuring the Doppler shifts of the lines. For the former, broad-band spectroscopy is essential; for the latter, high-resolution spectroscopy is critical. Therefore, IGRINS appears to be an ideal instrument to study them. An IGRINS survey of these new highly-obscured massive X-ray binaries can give us a rare opportunity to carry out population analyses for understanding the evolution of massive binary systems and formation of compact objects and their mass ranges. In this talk, we will present a sample near-infrared high resolution spectra of HMXB, IGR J19140+0951 and discuss about its spectral feature. These spectra are obtained on 13th July, 2014 from IGRINS commissioning run at McDonald 2.7m telescope. And at final, we will introduce the upgrade plan of IGRINS Operation Software (IGOS), to gather the input from IGRINS observer.

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