2017년 10월에 출간된 송유근 논문.
제목: Enhanced gamma radiation towards the rotation axis from the immediate vicinity of extremely rotating black holes
저자: Song, Yoogeun; Pu, Hung-Yi; Hirotani, Kouichi; Matsushita, Satoki; Kong, Albert K. H.; Chang, Hsiang-Kuang
저널: Monthly Notices of the Royal Astronomical Society: Letters (IF 4.893)
레터급으로 5페이지이며 짧은 결과를 보고하였음
PDF파일: https://arxiv.org/pdf/1707.07916.pdf
Abstract:
We investigate the acceleration of electrons and positrons by magnetic-field-aligned electric fields in the polar funnel of an accreting black hole (BH). Applying the pulsar outer-gap theory to BH magnetospheres, we find that such a lepton accelerator arises in the immediate vicinity of the event horizon due to frame-dragging, and that their gamma-ray luminosity increases with decreasing accretion rate. Furthermore, we demonstrate that the gamma-ray flux is enhanced along the rotation axis by more than an order of magnitude if the BH spin increases from a = 0.90M to a = 0.9999M. As a result, if a ten-solar-mass, almost-maximally rotating BH is located within 3 kpc, when its accretion rate is between 0.005 and 0.01 per cent of the Eddington rate, its high-energy flare becomes detectable with the Fermi/Large Area Telescope, provided that the flare lasts longer than 1.2 months and that we view the source nearly along the rotation axis. In addition, its very high energy flux is marginally detectable with the Cherenkov Telescope Array, provided that the flare lasts longer than a night and that our viewing angle is about 45 deg with respect to the rotation axis.
여기서 교신저자는 Kouichi Hirotani 인데 이사람의 최근 3개의 논문을 소개한다.
2017년 8월 논문
제목: Lepton Acceleration in the Vicinity of the Event Horizon: Very High Energy Emissions from Supermassive Black Holes
저자: Hirotani, Kouichi; Pu, Hung-Yi; Lin, Lupin Chun-Che; Kong, Albert K. H.; Matsushita, Satoki; Asada, Keiichi; Chang, Hsiang-Kuang; Tam, Pak-Hin T.
저널: Astrophysical Journal (IF 5.551)
PDF 파일: https://arxiv.org/pdf/1706.03766.pdf
Abstract:
Around a rapidly rotating black hole (BH), when the plasma accretion rate is much less than the Eddington rate, the radiatively inefficient accretion flow (RIAF) cannot supply enough MeV photons that are capable of materializing as pairs. In such a charge-starved BH magnetosphere, the force-free condition breaks down in the polar funnels. Applying the pulsar outer-magnetospheric lepton accelerator theory to supermassive BHs, we demonstrate that a strong electric field arises along the magnetic field lines in the direct vicinity of the event horizon in the funnels, that the electrons and positrons are accelerated up to 100 TeV in this vacuum gap, and that these leptons emit copious photons via inverse-Compton (IC) processes between 0.1 and 30 TeV for a distant observer. It is found that these IC fluxes will be detectable with Imaging Atmospheric Cherenkov Telescopes, provided that a low-luminosity active galactic nucleus is located within 1 Mpc for a million-solar-mass central BH or within 30 Mpc for a billion-solar-mass central BH. These very high energy fluxes are beamed in a relatively small solid angle around the rotation axis because of the inhomogeneous and anisotropic distribution of the RIAF photon field and show an anticorrelation with the RIAF submillimeter fluxes. The gap luminosity depends little on the 3D magnetic field configuration, because the Goldreich-Julian charge density, and hence the exerted electric field, is essentially governed by the frame-dragging effect, not by the magnetic field configuration.
전체적인 내용은 송유근의 논문의 기반이 된 것으로 보이며 송유근의 논문 보다 2개월 정도 빨리 나왔다.
송유근 논문의 초록과 비교해보자
송유근 논문의 초록
Applying the pulsar outer-gap theory to BH magnetospheres, we find that such a lepton accelerator arises in the immediate vicinity of the event horizon due to frame-dragging, and that their gamma-ray luminosity increases with decreasing accretion rate.
히로타니 논문의 초록
Applying the pulsar outer-magnetospheric lepton accelerator theory to super-massive BHs, we demonstrate that a strong electric field arises along the magnetic field lines in the direct vicinity of the event horizon in the funnels, that the electrons and positrons are accelerated up to 100 TeV in this vacuum gap, and that these leptons emit copious photons via inverse-Compton (IC) process between 0.1 TeV and 30 TeV for a distant observer.
송유근 초록은 다음 문장으로 이어진다.
Furthermore, we demonstrate that the gamma-ray flux is enhanced along the rotation axis by more than an order of magnitude if the BH spin increases from a = 0.90M to a = 0.9999M.
히로타니의 논문을 훑어보면 한 단원에서 BH spin이 0.9인 경우에 대한 수치실험을 하였다.
송유근 논문에서는 BH spin을 0.90 에서 0.9999로 높였을 때의 결과를 분석하여 보여주었다.
이만 소개를 마친다.
시간 되는 사람들은 논문 한번 훑어보도록.
밑에 히로타니의 다른 논문도 소개 하니 참고.
2016년 12월 논문
제목: Lepton Acceleration in the Vicinity of the Event Horizon: High-energy and Very-high-energy Emissions from Rotating Black Holes with Various Masses
저자: Hirotani, Kouichi; Pu, Hung-Yi; Lin, Lupin Chun-Che; Chang, Hsiang-Kuang; Inoue, Makoto; Kong, Albert K. H.; Matsushita, Satoki; Tam, Pak-Hin T.
저널: Astrophysical Journal (IF 5.551)
PDF파일: https://arxiv.org/pdf/1610.07819.pdf
Abstract:
We investigate the electrostatic acceleration of electrons and positrons in the vicinity of the event horizon, applying the pulsar outer-gap model to black hole (BH) magnetospheres. During a low accretion phase, the radiatively inefficient accretion flow (RIAF) cannot emit enough MeV photons that are needed to sustain the force-free magnetosphere via two-photon collisions. In such a charge-starved region (or a gap), an electric field arises along the magnetic field lines to accelerate electrons and positrons into ultra-relativistic energies. These relativistic leptons emit copious gamma rays via curvature and inverse-Compton (IC) processes. Some of such gamma rays collide with the submillimeter-IR photons emitted from the RIAF to materialize as pairs, which polarize to partially screen the original acceleration electric field. It is found that the gap gamma-ray luminosity increases with decreasing accretion rate. However, if the accretion rate decreases too much, the diminished RIAF soft photon field can no longer sustain a stationary pair production within the gap. As long as a stationary gap is formed, the magnetosphere becomes force-free outside the gap by the cascaded pairs, irrespective of the BH mass. If a nearby stellar-mass BH is in quiescence, or if a galactic intermediate-mass BH is in a very low accretion state, its curvature and IC emissions are found to be detectable with Fermi/LAT and imaging atmospheric Cherenkov telescopes (IACT). If a low-luminosity active galactic nucleus is located within about 30 Mpc, the IC emission from its supermassive BH is marginally detectable with IACT.
그 외에 2016년 2월에
제목: Energetic Gamma Radiation from Rapidly Rotating Black Holes
저자: Hirotani, Kouichi; Pu, Hung-Yi
PDF파일: https://arxiv.org/pdf/1512.05026.pdf
Abstract:
Supermassive black holes (BHs) are believed to be the central powerhouse of active galactic nuclei. Applying the pulsar outer-magnetospheric particle accelerator theory to BH magnetospheres, we demonstrate that an electric field is exerted along the magnetic field lines near the event horizon of a rotating BH. In this particle accelerator (or a gap), electrons and positrons are created by photon-photon collisions and accelerated in the opposite directions by this electric field, efficiently emitting gamma-rays via curvature and inverse-Compton processes. It is shown that a gap arises around the null-charge surface formed by the frame-dragging effect, provided that there is no current injection across the gap boundaries. The gap is dissipating a part of the hole's rotational energy, and the resultant gamma-ray luminosity increases with decreasing plasma accretion from the surroundings. Considering an extremely rotating supermassive BH, we show that such a gap reproduces the significant very-high-energy (VHE) gamma-ray flux observed from the radio galaxy IC 310, provided that the accretion rate becomes much less than the Eddington rate particularly during its flare phase. It is found that the curvature process dominates the inverse-Compton process in the magnetosphere of IC 310, and that the observed power-law-like spectrum in VHE gamma-rays can be explained to some extent by a superposition of the curvature emissions with varying curvature radius. It is predicted that the VHE spectrum extends into higher energies with increasing VHE photon flux.
나는 아무말도 하지 않았다. 논문만 소개 했을 뿐. 시간 되는사람들은 읽어보도록.
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