研究者業績
基本情報
受賞
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2022年2月
論文
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22 38-47 2018年6月29日Clusters of galaxies are the largest known gravitationally bound structures<br /> in the Universe, with masses around $10^{15}\ M_\odot$, most of it in the form<br /> of dark matter. The ground-based Imaging Atmospheric Cherenkov Telescope MAGIC<br /> made a deep survey of the Perseus cluster of galaxies using almost 400 h of<br /> data recorded between 2009 and 2017. This is the deepest observational campaign<br /> so far on a cluster of galaxies in the very high energy range. We search for<br /> gamma-ray signals from dark matter particles in the mass range between 200 GeV<br /> and 200 TeV decaying into standard model pairs. We apply an analysis optimized<br /> for the spectral and morphological features expected from dark matter decays<br /> and find no evidence of decaying dark matter. From this, we conclude that dark<br /> matter particles have a decay lifetime longer than $\sim10^{26}$~s in all<br /> considered channels. Our results improve previous lower limits found by MAGIC<br /> and represent the strongest limits on decaying dark matter particles from<br /> ground-based gamma-ray instruments.
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2018年6月14日PKS 1510-089 is a flat spectrum radio quasar strongly variable in the optical<br /> and GeV range. We search for low-state VHE gamma-ray emission from PKS<br /> 1510-089. We aim to characterize and model the source in a broad-band context,<br /> which would provide a baseline over which high states and flares could be<br /> better understood. We use daily binned Fermi-LAT flux measurements of PKS<br /> 1510-089 to characterize the GeV emission and select the observation periods of<br /> MAGIC during low state of activity. For the selected times we compute the<br /> average radio, IR, optical, UV, X-ray and gamma-ray emission to construct a<br /> low-state spectral energy distribution of the source. The broadband emission is<br /> modelled within an External Compton scenario with a stationary emission region<br /> through which plasma and magnetic field are flowing. We perform also the<br /> emission-model-independent calculations of the maximum absorption in the broad<br /> line region (BLR) using two different models. Results. The MAGIC telescopes<br /> collected 75 hrs of data during times when the Fermi-LAT flux measured above 1<br /> GeV was below 3x10-8cm-2s-1, which is the threshold adopted for the definition<br /> of a low gamma-ray activity state. The data show a strongly significant<br /> (9.5{\sigma}) VHE gamma-ray emission at the level of<br /> (4.27+-0.61stat)x10-12cm-2s-1 above 150GeV, a factor 80 smaller than the<br /> highest flare observed so far from this object. Despite the lower flux, the<br /> spectral shape is consistent with earlier detections in the VHE band. The<br /> broad-band emission is compatible with the EC scenario assuming a large<br /> emission region located beyond the BLR. For the first time the gamma-ray data<br /> allow us to place a limit on the location of the emission region during a low<br /> gamma-ray state of a FSRQ. For the used model of the BLR, the 95% C.L. on the<br /> location of the emission region allows us to place it at the distance >74% of<br /> the outer radius of the BLR.
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2018年6月5日We report on the detection of flaring activity from the Fanaroff-Riley I<br /> radio galaxy NGC 1275 in very-high-energy (VHE, E $>$ 100 GeV) gamma rays with<br /> the MAGIC telescopes. Observations were performed between 2016 September and<br /> 2017 February as part of a monitoring program. The brightest outburst with<br /> $\sim1.5$ times the Crab Nebula flux above 100 GeV (C.U.) was observed during<br /> the night between 2016 December 31 and 2017 January 1 (fifty times higher than<br /> the mean previously measured in two observational campaigns between 2009 and<br /> 2011). Significant variability of the day-by-day light curve was measured, the<br /> shortest flux-doubling time-scales was found to be of $(611\pm101)$ min. The<br /> combined spectrum of the MAGIC data during the strongest flare state and<br /> simultaneous data from the Fermi-LAT around 2017 January 1 follows a power-law<br /> with an exponential cutoff at the energy $(492\pm35)$ GeV. Simultaneous optical<br /> flux density measurements in the R-band obtained with the KVA telescope are<br /> also presented and the correlation between the optical and gamma-ray emission<br /> is investigated. Due to possible internal pair-production, the fast flux<br /> variability constrains the Doppler factor to values which are inconsistent with<br /> a large viewing angle as observed in the radio band. We investigate different<br /> scenarios for the explanation of fast gamma-ray variability, namely emission<br /> from: magnetospheric gaps, relativistic blobs propagating in the jet<br /> (mini-jets) or external cloud (or star) entering the jet. We find that the only<br /> plausible model to account for the luminosities here observed would be the<br /> production of gamma rays in a magnetospheric gap around the central black hole<br /> only in the eventuality of an enhancement of the magnetic field threading the<br /> hole from its equipartition value with the gas pressure in the accretion flow.
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Astronomy and Astrophysics 612 2018年4月1日Context. The large jet kinetic power and non-thermal processes occurring in the microquasar SS 433 make this source a good candidate for a very high-energy (VHE) gamma-ray emitter. Gamma-ray fluxes above the sensitivity limits of current Cherenkov telescopes have been predicted for both the central X-ray binary system and the interaction regions of SS 433 jets with the surrounding W50 nebula. Non-thermal emission at lower energies has been previously reported, indicating that efficient particle acceleration is taking place in the system. Aims. We explore the capability of SS 433 to emit VHE gamma rays during periods in which the expected flux attenuation due to periodic eclipses (Porb ∼ 13:1 days) and precession of the circumstellar disk (Ppre ∼ 162 days) periodically covering the central binary system is expected to be at its minimum. The eastern and western SS 433/W50 interaction regions are also examined using the whole data set available. We aim to constrain some theoretical models previously developed for this system with our observations. Methods.We made use of dedicated observations from the Major Atmospheric Gamma Imaging Cherenkov telescopes (MAGIC) and High Energy Spectroscopic System (H.E.S.S.) of SS 433 taken from 2006 to 2011. These observation were combined for the first time and accounted for a total effective observation time of 16.5 h, which were scheduled considering the expected phases of minimum absorption of the putative VHE emission. Gamma-ray attenuation does not affect the jet/medium interaction regions. In this case, the analysis of a larger data set amounting to ∼40-80 h, depending on the region, was employed. Results. No evidence of VHE gamma-ray emission either from the central binary system or from the eastern/western interaction regions was found. Upper limits were computed for the combined data set. Differential fluxes from the central system are found to be ≤10-12-10-13 TeV-1 cm-2 s-1 in an energy interval ranging from ∼few ×100 GeV to ∼few TeV. Integral flux limits down to ∼10-12-10-13 ph cm-2 s-1 and ∼10-13-10-14 ph cm-2 s-1 are obtained at 300 and 800 GeV, respectively. Our results are used to place constraints on the particle acceleration fraction at the inner jet regions and on the physics of the jet/medium interactions. Conclusions. Our findings suggest that the fraction of the jet kinetic power that is transferred to relativistic protons must be relatively small in SS 433, qp ≤ 2.5 × 10-5, to explain the lack of TeV and neutrino emission from the central system. At the SS 433/W50 interface, the presence of magnetic fields ≥10 μG is derived assuming a synchrotron origin for the observed X-ray emission. This also implies the presence of high-energy electrons with Ee- up to 50 TeV, preventing an efficient production of gamma-ray fluxes in these interaction regions.
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Journal of Cosmology and Astroparticle Physics 2018(3) 2018年3月7日The dwarf spheroidal galaxy Ursa Major II (UMaII) is believed to be one of the most dark-matter dominated systems among the Milky Way satellites and represents a suitable target for indirect dark matter (DM) searches. The MAGIC telescopes carried out a deep observation campaign on UMaII between 2014 and 2016, collecting almost one hundred hours of good-quality data. This campaign enlarges the pool of DM targets observed at very high energy (E ≳ 50 GeV) in search for signatures of DM annihilation in the wide mass range between ∼100 GeV and ∼100 TeV. To this end, the data are analyzed with the full likelihood analysis, a method based on the exploitation of the spectral information of the recorded events for an optimal sensitivity to the explored DM models. We obtain constraints on the annihilation cross-section for different channels that are among the most robust and stringent achieved so far at the TeV mass scale from observations of dwarf satellite galaxies.
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A&A 617, A30 (2018) 2018年1月12日The very-high-energy (VHE, $\gtrsim 100$ GeV) $\gamma$-ray MAGIC observations<br /> of the blazar S4 0954+65, were triggered by an exceptionally high flux state of<br /> emission in the optical. This blazar has a disputed redshift of z=0.368 or<br /> z$\geqslant$0.45 and an uncertain classification among blazar subclasses. The<br /> exceptional source state described here makes for an excellent opportunity to<br /> understand physical processes in the jet of S4 0954+65 and thus contribute to<br /> its classification. We investigate the multiwavelength (MWL) light curve and<br /> spectral energy distribution (SED) of the S4 0954+65 blazar during an enhanced<br /> state in February 2015 and put it in context with possible emission scenarios.<br /> We collect photometric data in radio, optical, X-ray, and $\gamma$ ray. We<br /> study both the optical polarization and the inner parsec-scale jet behavior<br /> with 43 GHz data. Observations with the MAGIC telescopes led to the first<br /> detection of S4 0954+65 at VHE. Simultaneous data with Fermi-LAT at high energy<br /> $\gamma$ ray\ (HE, 100 MeV < E < 100 GeV) also show a period of increased<br /> activity. Imaging at 43 GHz reveals the emergence of a new feature in the radio<br /> jet in coincidence with the VHE flare. Simultaneous monitoring of the optical<br /> polarization angle reveals a rotation of approximately 100$^\circ$. (...) The<br /> broadband spectrum can be modeled with an emission mechanism commonly invoked<br /> for flat spectrum radio quasars, i.e. inverse Compton scattering on an external<br /> soft photon field from the dust torus, also known as external Compton. The<br /> light curve and SED phenomenology is consistent with an interpretation of a<br /> blob propagating through a helical structured magnetic field and eventually<br /> crossing a standing shock in the jet, a scenario typically applied to flat<br /> spectrum radio quasars (FSRQs) and low-frequency peaked BL Lac objects (LBL).
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MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 472(3) 3474-3485 2017年12月The microquasar Cygnus X-1 displays the two typical soft and hard X-ray states of a black hole transient. During the latter, Cygnus X-1 shows a one-sided relativistic radio-jet. Recent detection of the system in the high energy (HE; E greater than or similar to 60 MeV) gamma-ray range with FermiLAT associates this emission with the outflow. Former MAGIC observations revealed a hint of flaring activity in the very high-energy (VHE; E greater than or similar to 100 GeV) regime during this X-ray state. We analyse similar to 97 h of Cygnus X-1 data taken with the MAGIC telescopes between July 2007 and October 2014. To shed light on the correlation between hard X-ray and VHE gamma rays as previously suggested, we study each main X-ray state separately. We perform an orbital phase-folded analysis to look for variability in the VHE band. Additionally, to place this variability behaviour in a multiwavelength context, we compare our results with Fermi-LAT, AGILE, Swift-BAT, MAXI, RXTE-ASM, AMI and RATAN-600 data. We do not detect Cygnus X-1 in the VHE regime. We establish upper limits for each X-ray state, assuming a power-law distribution with photon index Gamma = 3.2. For steady emission in the hard and soft X-ray states, we set integral upper limits at 95 per cent confidence level for energies above 200 GeV at 2.6 x 10(-12) photons cm(-2) s(-1) and 1.0 x 10(-11) photons cm(-2) s(-1), respectively. We rule out steady VHE gamma-ray emission above this energy range, at the level of theMAGIC sensitivity, originating in the interaction between the relativistic jet and the surrounding medium, while the emission above this flux level produced inside the binary still remains a valid possibility.
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MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 472(3) 2956-2962 2017年12月It is widely believed that the bulk of the Galactic cosmic rays is accelerated in supernova remnants (SNRs). However, no observational evidence of the presence of particles of PeV energies in SNRs has yet been found. The young historical SNR Cassiopeia A (Cas A) appears as one of the best candidates to study acceleration processes. Between 2014 December and 2016 October, we observed Cas A with the MAGIC telescopes, accumulating 158 h of good quality data. We derived the spectrum of the source from 100 GeV to 10 TeV. We also analysed similar to 8 yr of Fermi-LAT to obtain the spectral shape between 60 MeV and 500 GeV. The spectra measured by the LAT andMAGIC telescopes are compatible within the errors and show a clear turn-off (4.6 sigma) at the highest energies, which can be described with an exponential cut-off at E-c = 3.5((+1.6)(-1.0))(stat)((+0.8)(-0.9))(sys) TeV. The gamma-ray emission from 60 MeV to 10 TeV can be attributed to a population of high-energy protons with a spectral index of similar to 2.2 and an energy cut-off at similar to 10 TeV. This result indicates that Cas A is not contributing to the high energy (similar to PeV) cosmic ray sea in a significant manner at the present moment. A one-zone leptonic model fails to reproduce by itself the multiwavelength spectral energy distribution. Besides, if a non-negligible fraction of the flux seen by MAGIC is produced by leptons, the radiation should be emitted in a region with a low magnetic field (B less than or similar to 180 mu G) like in the reverse shock.
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JOURNAL OF INSTRUMENTATION 12 2017年12月We have developed a prototype hexagonal light concentrator for the Large-Sized Telescopes of the Cherenkov Telescope Array. To maximize the photodetection efficiency of the focal-plane camera pixels for atmospheric Cherenkov photons and to lower the energy threshold, a specular film with a very high reflectance of 92-99% has been developed to cover the inner surfaces of the light concentrators. The prototype has a relative anode sensitivity (which can be roughly regarded as collection efficiency) of about 95 to 105% at the most important angles of incidence. The design, simulation, production procedure, and performance measurements of the light-concentrator prototype are reported.
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MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 470(4) 4608-4617 2017年10月B1957+20 is a millisecond pulsar located in a black-widow-type compact binary system with a low-mass stellar companion. The interaction of the pulsar wind with the companion star wind and/or the interstellar plasma is expected to create plausible conditions for acceleration of electrons to TeV energies and subsequent production of very high-energy gamma-rays in the inverse Compton process. We performed extensive observations with the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) telescopes of B1957+20. We interpret results in the framework of a few different models, namely emission from the vicinity of the millisecond pulsar, the interaction of the pulsar and stellar companion wind region or bow shock nebula. No significant steady very high-energy gamma-ray emission was found. We derived a 95 per cent confidence level upper limit of 3.0 x 10(-12) cm(-2) s(-1) on the average gamma-ray emission from the binary system above 200 GeV. The upper limits obtained with the MAGIC constrain, for the first time, different models of the high-energy emission in B1957+20. In particular, in the inner mixed wind nebula model with mono-energetic injection of electrons, the acceleration efficiency of electrons is constrained to be below similar to 2-10 per cent of the pulsar spin-down power. For the pulsar emission, the obtained upper limits for each emission peak are well above the exponential cut-off fits to the Fermi-LAT data, extrapolated to energies above 50 GeV. The MAGIC upper limits can rule out a simple power-law tail extension through the sub-TeV energy range for the main peak seen at radio frequencies.
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MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 471(2) 1688-1693 2017年10月The microquasar V404 Cygni underwent a series of outbursts in 2015, June 15-31, during which its flux in hard X-rays (20-40 keV) reached about 40 times the Crab nebula flux. Because of the exceptional interest of the flaring activity from this source, observations at several wavelengths were conducted. The MAGIC telescopes, triggered by the INTEGRAL alerts, followed-up the flaring source for several nights during the period June 18-27, for more than 10 h. One hour of observation was simultaneously conducted on a giant 22 GHz radio flare and a hint of signal at GeV energies seen by Fermi-LAT. The MAGIC observations did not show significant emission in any of the analysed time intervals. The derived flux upper limit, in the energy range 200-1250 GeV, is 4.8 x 10(-12) photons cm(-2) s(-1). We estimate the gamma-ray opacity during the flaring period, which along with our non-detection points to an inefficient acceleration in the V404 Cyg jets if a very high energy emitter is located further than 1 x 10(10) cm from the compact object.
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2017年9月23日The Cherenkov Telescope Array, CTA, will be the major global observatory for<br /> very high energy gamma-ray astronomy over the next decade and beyond. The<br /> scientific potential of CTA is extremely broad: from understanding the role of<br /> relativistic cosmic particles to the search for dark matter. CTA is an explorer<br /> of the extreme universe, probing environments from the immediate neighbourhood<br /> of black holes to cosmic voids on the largest scales. Covering a huge range in<br /> photon energy from 20 GeV to 300 TeV, CTA will improve on all aspects of<br /> performance with respect to current instruments.<br /> The observatory will operate arrays on sites in both hemispheres to provide<br /> full sky coverage and will hence maximize the potential for the rarest<br /> phenomena such as very nearby supernovae, gamma-ray bursts or gravitational<br /> wave transients. With 99 telescopes on the southern site and 19 telescopes on<br /> the northern site, flexible operation will be possible, with sub-arrays<br /> available for specific tasks. CTA will have important synergies with many of<br /> the new generation of major astronomical and astroparticle observatories.<br /> Multi-wavelength and multi-messenger approaches combining CTA data with those<br /> from other instruments will lead to a deeper understanding of the broad-band<br /> non-thermal properties of target sources.<br /> The CTA Observatory will be operated as an open, proposal-driven observatory,<br /> with all data available on a public archive after a pre-defined proprietary<br /> period. Scientists from institutions worldwide have combined together to form<br /> the CTA Consortium. This Consortium has prepared a proposal for a Core<br /> Programme of highly motivated observations. The programme, encompassing<br /> approximately 40% of the available observing time over the first ten years of<br /> CTA operation, is made up of individual Key Science Projects (KSPs), which are<br /> presented in this document.
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ASTRONOMY & ASTROPHYSICS 602 2017年6月 査読有りContext. In this work we present data from observations with the MAGIC telescopes of SN 2014J detected on January 21 2014, the closest Type Ia supernova since Imaging Air Cherenkov Telescopes started to operate. Aims. We aim to probe the possibility of very-high-energy (VHE; E >= 100 GeV) gamma rays produced in the early stages of Type Ia supernova explosions. Methods. We performed follow-up observations after this supernova (SN) explosion for five days, between January 27 and February 2 2014. We searched for gamma-ray signals in the energy range between 100 GeV and several TeV from the location of SN 2014J using data from a total of similar to 5.5 h of observations. Prospects for observing gamma rays of hadronic origin from SN 2014J in the near future are also being addressed. Results. No significant excess was detected from the direction of SN 2014J. Upper limits at 95% confidence level on the integral flux, assuming a power-law spectrum, dF/dE proportional to E-Gamma, with a spectral index of Gamma = 2.6, for energies higher than 300 GeV and 700 GeV, are established at 1.3 x 10(-12) and 4.1 x 10-(13) photons cm(-2) s(-1), respectively. Conclusions. For the first time, upper limits on the VHE emission of a Type Ia supernova are established. The energy fraction isotropically emitted into TeV gamma rays during the first similar to 10 days after the supernova explosion for energies greater than 300 GeV is limited to 10(-6) of the total available energy budget (similar to 10(51) erg). Within the assumed theoretical scenario, the MAGIC upper limits on the VHE emission suggest that SN 2014J will not be detectable in the future by any current or planned generation of Imaging Atmospheric Cherenkov Telescopes.
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Proceedings of Science 2017年There are several types of Galactic sources that can potentially accelerate charged particles up to GeV and TeV energies. We present here the results of our observations of the source class of γ-ray binaries and the subclass of binary systems known as novae with the MAGIC telescopes. Up to now novae were only detected in the GeV range. This emission can be interpreted in terms of an inverse Compton process of electrons accelerated in a shock. In this case it is expected that protons in the same conditions can be accelerated to much higher energies. Consequently they may produce a second component in the γ-ray spectrum at TeV energies. The focus here lies on the four sources: nova V339 Del, SS 433, LS I +61°303 and V404 Cygni. The binary system LS I+61°303 was observed in a long-term monitoring campaign for 8 years. We show the newest results on our search for superorbital variability, also in context with contemporaneous optical observations. Furthermore, we present the observations of the only super-critical accretion system known in our galaxy: SS 433. Finally, the results of the follow-up observations of the microquasar V404 Cygni during a series of outbursts in the X-ray band and the ones of the nova V339 Del will be discussed in these proceedings.
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Proceedings of Science 2017年The extragalactic background light (EBL) is the radiation accumulated through the history of the Universe in the wavelength range from the ultraviolet to the far infrared. Local foregrounds make the direct measurement of the diffuse EBL notoriously difficult, while robust lower limits have been obtained by adding up the contributions of all the discrete sources resolved in deep infrared and optical galaxy observations. Gamma-ray astronomy has emerged in the past few years as a powerful tool for the study of the EBL: very-high-energy (VHE) photons traversing cosmological distances can interact with EBL photons to produce e+e- pairs, resulting in an energy-dependent depletion of the gamma-ray flux of distant sources that can be used to set constraints on the EBL density. The study of the EBL is one of the key scientific programs currently carried out by the MAGIC collaboration. We present here the results of the analysis of 32 VHE spectra of 12 blazars in the redshift range 0.03-0.94, obtained with over 300 hours of observations with the MAGIC telescopes between 2010 and 2016. A combined likelihood maximization approach is used to evaluate the density and spectrum of the EBL most consistent with the MAGIC observations. The results are compatible with state-of-the-art EBL models, and constrain the EBL density to be within ≈ 20% the nominal value in such models. The study reveals no anomalies in gamma-ray propagation in the large optical depth regime - contrary to some claims based on meta-analyses of published VHE spectra.
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HIGH ENERGY GAMMA-RAY ASTRONOMY 1792 2017年 査読有りThe MAGIC telescopes are strongly involved in several multimessenger programs. One of them are follow-up observations of astrophysical neutrino events, to search for hadronic gamma-ray emission from the neutrino direction and identify potential neutrino sources. In 2013 the IceCube collaboration reported the first detection of astrophysical neutrinos and up to now 55 events, which interact inside the IceCube detector active volume, dubbed High Energy Starting Events (HESE), have been reported. These include 13 track-like events, caused usually by muon neutrino charge current interactions. The track-like events ( as opposed to cascade-like neutral current interactions) are characterised by a very good angular resolution of < 1 deg, which facilitates follow-up observations and potential source identification. The MAGIC telescopes performed follow-up observations of 4 HESE track-like events from the Northern hemisphere: HESE-37, HESE-38, HET (ATel #7856) and the GCN HESE alert from 27/04/2016 (GCN #19363). No signal was detected. Here we present the results of those observations and discuss the implications for the constraints on the density of the astrophysical neutrino sources.
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日本物理学会講演概要集 71 343-343 2016年<p>CTA大口径望遠鏡には約47kgの球面分割鏡がおよそ200枚取り付けられる。主に自重により望遠鏡全体の向きに依存して構造体に歪みが発生し、分割鏡の方向が変化して信号光は正しく集光されない。そのため、各分割鏡に設置したカメラで光軸レーザーのスポットを常にモニターしてずれを検知し、分割鏡を支えるアクチュエータの長さを制御し方向を微調整する、Active Mirror Control (AMC) と呼ばれる手法が採用された。望遠鏡サイトに近い環境での試験を通じて、すでにこの手法による分割鏡の高精度補正の成功を確認している。本講演ではAMCシステムを外部PCからの動作を可能にするためにソフトウェアを改善し、実際の望遠鏡の運用時に向けて開発したシステムの現状を報告する。</p>
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SOFTWARE AND CYBERINFRASTRUCTURE FOR ASTRONOMY IV 9913 2016年 査読有りToday the scientific community is facing an increasing complexity of the scientific projects, from both a technological and a management point of view. The reason for this is in the advance of science itself, where new experiments with unprecedented levels of accuracy, precision and coverage (time and spatial) are realised. Astronomy is one of the fields of the physical sciences where a strong interaction between the scientists, the instrument and software developers is necessary to achieve the goals of any Big Science Project. The Cherenkov Telescope Array (CTA) will be the largest ground-based very high-energy gamma-ray observatory of the next decades. To achieve the full potential of the CTA Observatory, the system must be put into place to enable users to operate the telescopes productively. The software will cover all stages of the CTA system, from the preparation of the observing proposals to the final data reduction, and must also fit into the overall system. Scientists, engineers, operators and others will use the system to operate the Observatory, hence they should be involved in the design process from the beginning. We have organised a workgroup and a workflow for the definition of the CTA Top Level Use Cases in the context of the Requirement Management activities of the CTA Observatory. Scientists, instrument and software developers are collaborating and sharing information to provide a common and general understanding of the Observatory from a functional point of view. Scientists that will use the CTA Observatory will provide mainly Science Driven Use Cases, whereas software engineers will subsequently provide more detailed Use Cases, comments and feedbacks. The main purposes are to define observing modes and strategies, and to provide a framework for the flow down of the Use Cases and requirements to check missing requirements and the already developed Use-Case models at CTA sub-system level. Use Cases will also provide the basis for the definition of the Acceptance Test Plan for the validation of the overall CTA system. In this contribution we present the organisation and the workflow of the Top Level Use Cases workgroup.
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Astronomy & Astrophysics Volume 576(id.A 126) A126-A126 2015年1月16日
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日本物理学会講演概要集 70 376-376 2015年
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MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 446(1) 217-225 2015年1月 査読有りThe number of known very high energy (VHE) blazars is similar to 50, which is very small in comparison to the number of blazars detected in other frequencies. This situation is a handicap for population studies of blazars, which emit about half of their luminosity in the gamma-ray domain. Moreover, VHE blazars, if distant, allow for the study of the environment that the high-energy gamma-rays traverse in their path towards the Earth, like the extragalactic background light (EBL) and the intergalactic magnetic field (IGMF), and hence they have a special interest for the astrophysics community. We present the first VHE detection of 1ES 0033+595 with a statistical significance of 5.5 sigma. The VHE emission of this object is constant throughout the MAGIC observations (2009 August and October), and can be parametrized with a power law with an integral flux above 150 GeV of (7.1 +/- 1.3) x 10(-12) photons cm(-2) s(-1) and a photon index of (3.8 +/- 0.7). We model its spectral energy distribution (SED) as the result of inverse Compton scattering of synchrotron photons. For the study of the SED, we used simultaneous opticalR-band data from the KVA telescope, archival X-ray data by Swift as well as INTEGRAL, and simultaneous high-energy (HE, 300 MeV-10 GeV) gamma-ray data from the Fermi Large Area Telescope (LAT) observatory. Using the empirical approach of Prandini et al. (2010) and the Fermi LAT and MAGIC spectra for this object, we estimate the redshift of this source to be 0.34 +/- 0.08 +/- 0.05. This is a relevant result because this source is possibly one of the 10 most distant VHE blazars known to date, and with further (simultaneous) observations could play an important role in blazar population studies, as well as future constraints on the EBL and IGMF.
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Astronomy and Astrophysics 572 2014年12月1日© ESO, 2014. Aims. We aim to characterize the broadband emission from 2FGL J2001.1+4352, which has been associated with the unknown-redshift blazar MG4 J200112+4352. Based on its gamma-ray spectral properties, it was identified as a potential very high energy (VHE; E> 100 GeV) gamma-ray emitter. We investigate whether this object is aVHE emitter, characterize its gamma-ray spectrum, and study the broadband emission within the one-zone synchrotron self-Compton (SSC) scenario, which is commonly used to describe the emission in blazars. Moreover, we also intend to determine the redshift of this object, which is a crucial parameter for its scientific interpretation. Methods. The source was observed with MAGIC first in 2009 and later in 2010 within a multi-instrument observation campaign. The MAGIC observations yielded 14.8 h of good quality stereoscopic data. Besides MAGIC, the campaign involved, observations with Fermi-LAT, Swift-XRT/UVOT, the optical telescopes KVA, Goddard Robotic Telescope, Galaxy View observatory, Crimean Astrophysical observatory, St. Petersburg observatory, and the Owens Valley Radio Observatory. The object was monitored at radio, optical and gamma-ray energies during the years 2010 and 2011. We characterize the radio to VHE spectral energy distribution and quantify the multiband variability and correlations over short (few days) and long (many months) timescales. We also organized deep imaging optical observations with the Nordic Optical Telescope in 2013 to determine the source redshift. Results. The source, named MAGIC J2001+439, is detected for the first time at VHE with MAGIC at a statistical significance of 6.3σ (E > 70 GeV) during a 1.3 h long observation on 2010 July 16. The multi-instrument observations show variability in all energy bands with the highest amplitude of variability in the X-ray and VHE bands. Besides the variability on few-day timescales, the long-term monitoring of MAGIC J2001+439 shows that, the gamma-ray, optical, and radio emissions gradually decreased on few-month timescales from 2010 through 2011, indicating that at least some of the radio, optical and gamma-ray emission is produced in a single region by the same population of particles. We also determine for the first time the redshift of this BL Lac object through the measurement of its host galaxy during low blazar activity. Using the observational evidence that the luminosities of BL Lac host galaxies are confined to a relatively narrow range, we obtain z = 0.18 ± 0.04. Additionally, we use the Fermi-LAT and MAGIC gamma-ray spectra to provide an independent redshift estimation, z = 0.17 ± 0.10. Using the former (more accurate) redshift value, we adequately describe the broadband emission with a one-zone SSC model for different activity states and interpret the few-day timescale variability as produced by changes in the high-energy component of the electron energy distribution.
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Astronomy and Astrophysics 573(A50) 12 2014年10月24日 査読有りMrk 501 is one of the brightest blazars at TeV energies and has been<br /> extensively studied since its first VHE detection in 1996. Our goal is to<br /> characterize in detail the source gamma-ray emission, together with the<br /> radio-to-X-ray emission, during the non-flaring (low) activity, which is less<br /> often studied than the occasional flaring (high) activity. We organized a<br /> multiwavelength (MW) campaign on Mrk 501 between March and May 2008. This<br /> multi-instrument effort included the most sensitive VHE gamma-ray instruments<br /> in the northern hemisphere, namely the imaging atmospheric Cherenkov telescopes<br /> MAGIC and VERITAS, as well as Swift, RXTE, the F-GAMMA, GASP-WEBT, and other<br /> collaborations and instruments. Mrk 501 was found to be in a low state of<br /> activity during the campaign, with a VHE flux in the range of 10%-20% of the<br /> Crab nebula flux. Nevertheless, significant flux variations were detected with<br /> various instruments, with a trend of increasing variability with energy. The<br /> broadband spectral energy distribution during the two different emission states<br /> of the campaign can be adequately described within the homogeneous one-zone<br /> synchrotron self-Compton model, with the (slightly) higher state described by<br /> an increase in the electron number density. This agrees with previous studies<br /> of the broadband emission of this source during flaring and non-flaring states.<br /> We report for the first time a tentative X-ray-to-VHE correlation during a low<br /> VHE activity. Although marginally significant, this positive correlation<br /> between X-ray and VHE, which has been reported many times during flaring<br /> activity, suggests that the mechanisms that dominate the X-ray/VHE emission<br /> during non-flaring-activity are not substantially different from those that are<br /> responsible for the emission during flaring activity.
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564 2013年10月31日 査読有りThe radio galaxy NGC 1275, recently identified as a very high energy (VHE,<br /> >100 GeV) gamma-ray emitter by MAGIC, is one of the few non-blazar AGN detected<br /> in the VHE regime. In order to better understand the origin of the gamma-ray<br /> emission and locate it within the galaxy, we studied contemporaneous<br /> multi-frequency observations of NGC 1275 and modeled the overall spectral<br /> energy distribution (SED). We analyzed unpublished MAGIC observations carried<br /> out between Oct. 2009 and Feb. 2010, and the previously published ones taken<br /> between Aug. 2010 and Feb. 2011. We studied the multi-band variability and<br /> correlations by analyzing data of Fermi-LAT (0.1-100 GeV), as well as Chandra<br /> (X-ray), KVA (optical) and MOJAVE (radio) data taken during the same period.<br /> Using customized Monte Carlo simulations corresponding to early MAGIC stereo<br /> data, we detect NGC 1275 also in the earlier campaign. The flux level and<br /> energy spectra are similar to the results of the second campaign. The monthly<br /> light curve >100 GeV shows a hint of variability at the 3.6 sigma level. In the<br /> Fermi-LAT band, both flux and spectral shape variabilities are reported. The<br /> optical light curve is variable and shows a clear correlation with the<br /> gamma-ray flux >100 MeV. In radio, 3 compact components are resolved in the<br /> innermost part of the jet. One of them shows a similar trend as the LAT and KVA<br /> light curves. The 0.1-650 GeV spectra measured simultaneously with MAGIC and<br /> Fermi-LAT can be well fitted either by a log-parabola or by a power-law with a<br /> sub-exponential cutoff for both campaigns. A single-zone<br /> synchrotron-self-Compton model, with an electron spectrum following a power-law<br /> with an exponential cutoff, can explain the broadband SED and the multi-band<br /> behavior of the source. However, this model suggests an untypical low<br /> bulk-Lorentz factor or a velocity alignment closer to the line of sight than<br /> the pc-scale radio jet.
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INTERNATIONAL JOURNAL OF MODERN PHYSICS A 28(25) 1330036 2013年10月 査読有り招待有りLarge Hadron Collider forward (LHCf) has successfully completed the operation during the LHC 2009-2010 period and the detectors were removed in July 2010. The event trigger, data analysis and background have been intensively studied in order to derive inclusive single photon and pi(0) spectra. In this paper, the details of these intensive studies are described.
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Nuovo Cimento della Societa Italiana di Fisica C 36(1) 120-123 2013年 査読有りLHCf is an experiment designed to study the very forward emission of neutral particles produced in collisions at the LHC. Its results can be used to calibrate the hadron interaction models of the Monte Carlo codes which allow the interpretation of energy spectrum and composition of high-energy cosmic rays as measured by air shower ground detectors. The experiment has already completed taking data in proton-proton collisions at √s = 900 GeV and at √s = 7TeV during 2009 and 2010. The detectors are now being upgraded and they will be installed again in the LHC tunnel for proton-ion collisions and for operation with protons at √s = 14TeV. In this paper results and comparisons with the predictions obtained from Monte Carlo simulations will be reported. © Società Italiana di Fisica.
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UHECR 2012 - INTERNATIONAL SYMPOSIUM ON FUTURE DIRECTIONS IN UHECR PHYSICS 53 2013年 査読有りThe Large Hadron Collider forward (= LHCf) experiment has successfully finished the first phase of data taking at LHC root s = 0.9 and 7 TeV proton- proton collisions in 2010. As current status, we concentrate on analyzing the obtained data. As the first result, the energy spectra of photon measured by LHCf during = 7 TeV p-p collision has been published recently. Also the study of the upgraded version of LHCf detector for future = 14 TeV run scenario is developed with the GSO scintillator. Another possible plan of p-A(nuclear) collision in LHC is also studied. In this paper, as the current status of the experiment, analyses, and works for foreseen detector upgrade are summarized.
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UHECR 2012 - INTERNATIONAL SYMPOSIUM ON FUTURE DIRECTIONS IN UHECR PHYSICS 53 2013年 査読有りLHCf is planning to measure very forward particle emission in the LHC p-Pb collisions foreseen at the end of 2012. The measurement is expected to constrain the nuclear effect in the forward particle emission relevant to the CR-Air interaction. Model discrimination power of this measurement is presented together with some detail in technical feasibility.
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PHYSICAL REVIEW D 86(9) 2012年11月The inclusive production rate of neutral pions in the rapidity range greater than y = 8.9 has been measured by the Large Hadron Collider forward (LHCf) experiment during root s = 7 TeV proton-proton collision operation in early 2010. This paper presents the transverse momentum spectra of the neutral pions. The spectra from two independent LHCf detectors are consistent with each other and serve as a cross-check of the data. The transverse momentum spectra are also compared with the predictions of several hadronic interaction models that are often used for high-energy particle physics and for modeling ultrahigh-energy cosmic ray showers.
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PHYSICS LETTERS B 715(4-5) 298-303 2012年9月The inclusive photon energy spectra measured by the Large Hadron Collider forward (LHCf) experiment in the very forward region of LHC proton-proton collisions at root s = 900 GeV are reported. The results from the analysis of 0.30 nb(-1) of data collected in May 2010 in the two pseudorapidity regions of eta > 10.15 and 8.77 < eta <9.46 are compared with the predictions of the hadronic interaction models DPMJET 3.04, EPOS 1.99, PYTHIA 8.145, QGSJET II-03 and SIBYLL 2.1, which are widely used in ultra-high energy cosmic ray experiments. EPOS 1.99 and SIBYLL 2.1 show a reasonable agreement with the spectral shape of the experimental data, whereas they predict lower cross-sections than the data. The other models. DPMJET 3.04, QGSJET II-03 and PYTHIA 8.145, are in good agreement with the data below 300 GeV but predict harder energy spectra than the data above 300 GeV. The results of these comparisons exhibited features similar to those for the previously reported data for root s = 7 TeV collisions. (c) 2012 Elsevier B.V. All rights reserved.
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AIP Conference Proceedings 1505 578-581 2012年The Perseus cluster of galaxies is a nearby cool-core cluster with an intra-clustermedium (ICM) characterized by very high central densities. The observation of the Perseus cluster with the MAGIC telescopes, during 85 h from 2009 to 2011, resulted in the discovery of 2 point-like sources at very high energy (>100 GeV, VHE) coinciding with the central radio galaxy NGC1275 and the radio galaxy IC310. The γ-ray properties of these 2 sources are presented, taking into account contemporaneous Fermi-LAT as well as multi-wavelength data. Flux variability and spectral energy distribution shapes indicate that the VHE γ-rays do not originate from large-scale interaction of the radio galaxies with ICM but more likely from the active nuclei of these two galaxies. They could be both misaligned version of BL Lac objects, the most common TeV AGN. Our results provide vital clues to understand emission mechanisms of such misaligned objects, and how they may be related to the beamed emission seen in BL Lacs. No evidence of large-scale VHE γ-ray emission from hadronic cosmic ray (CR) interactions with the ICM has been found. The flux upper limit above 1 TeV reaches the signal expected by some theoretical models, constraining the cluster CR physics. In the framework of the hadronicmodel of the radiomini-halos, this limit implies aminimal magnetic field ranging from 4-9μG for the central cluster region. © 2012 American Institute of Physics.
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PHYSICS LETTERS B 703(2) 128-134 2011年9月In early 2010. the Large Hadron Collider forward (LHCf) experiment measured very forward neutral particle spectra in LHC proton-proton collisions. From a limited data set taken under the best beam conditions (low beam-gas background and low occurrence of pile-up events), the single photon spectra at root s = 7 TeV and pseudo-rapidity (eta) ranges from 8.81 to 8.99 and from 10.94 to infinity were obtained for the first time and are reported in this Letter. The spectra from two independent LHCf detectors are consistent with one another and serve as a cross check of the data. The photon spectra are also compared with the predictions of several hadron interaction models that are used extensively for modeling ultra-high energy cosmic-ray showers. Despite conservative estimates for the systematic errors, none of the models agree perfectly with the measurements. A notable difference is found between the data and the DPMJET 3.04 and PYTHIA 8.145 hadron interaction models above 2 TeV where the models predict higher photon yield than the data. The QGSJET II-03 model predicts overall lower photon yield than the data, especially above 2 TeV in the rapidity range 8.81 < eta < 8.99. (C) 2011 CERN for the benefit of the LHCf collaboration
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ASTROPHYSICAL JOURNAL LETTERS 736(1) 2011年7月We report the first observational search for tau neutrinos (nu(tau)) from gamma-ray bursts (GRBs) using one of the Ashra light collectors. The Earth-skimming nu(tau) technique of imaging Cherenkov tau showers was applied as a detection method. We set stringent upper limits on the nu(tau) fluence in PeV-EeV region for 3780 s (between 2.83 and 1.78 hr before) and another 3780 s (between 21.2 and 22.2 hr after) surrounding GRB081203A triggered by the Swift satellite. This first search for PeV-EeV nu(tau) complements other experiments in energy range and methodology, and suggests the prologue of "multi-particle astronomy" with a precise determination of time and location.
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Astrophysical Journal Letters 730(1) 2011年3月20日Very high energy (VHE) γ-ray emission from the flat spectrum radio quasar (FSRQ) PKS1222+21 (4C21.35, z = 0.432) was detected with the MAGIC Cherenkov telescopes during a short observation (0.5hr) performed on 2010 June 17. The MAGIC detection coincides with high-energy MeV/GeV γ-ray activity measured by the Large Area Telescope (LAT) on board the Fermi satellite. The VHE spectrum measured by MAGIC extends from about 70GeV up to at least 400GeV and can be well described by a power-law dN/dE E -Γ with a photon index Γ = 3.75 0.27stat 0.2syst. The averaged integral flux above 100GeV is (4.6 0.5) × 10-10 cm-2 s-1 (1 Crab Nebula flux). The VHE flux measured by MAGIC varies significantly within the 30 minute exposure implying a flux doubling time of about 10 minutes. The VHE and MeV/GeV spectra, corrected for the absorption by the extragalactic background light (EBL), can be described by a single power law with photon index 2.72 0.34 between 3GeV and 400GeV, and is consistent with emission belonging to a single component in the jet. The absence of a spectral cutoff constrains the γ-ray emission region to lie outside the broad-line region, which would otherwise absorb the VHE γ-rays. Together with the detected fast variability, this challenges present emission models from jets in FSRQs. Moreover, the combined Fermi/LAT and MAGIC spectral data yield constraints on the density of the EBL in the UV-optical to near-infrared range that are compatible with recent models. © 2011. The American Astronomical Society. All rights reserved.
MISC
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Proceedings of Science 395 787 2022年3月 査読有り
講演・口頭発表等
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HIGH ENERGY GAMMA-RAY ASTRONOMY 2017年 AMER INST PHYSICSThe MAGIC telescopes are strongly involved in several multimessenger programs. One of them are follow-up observations of astrophysical neutrino events, to search for hadronic gamma-ray emission from the neutrino direction and identify potential neutrino sources. In 2013 the IceCube collaboration reported the first detection of astrophysical neutrinos and up to now 55 events, which interact inside the IceCube detector active volume, dubbed High Energy Starting Events (HESE), have been reported. These include 13 track-like events, caused usually by muon neutrino charge current interactions. The track-like events ( as opposed to cascade-like neutral current interactions) are characterised by a very good angular resolution of < 1 deg, which facilitates follow-up observations and potential source identification. The MAGIC telescopes performed follow-up observations of 4 HESE track-like events from the Northern hemisphere: HESE-37, HESE-38, HET (ATel #7856) and the GCN HESE alert from 27/04/2016 (GCN #19363). No signal was detected. Here we present the results of those observations and discuss the implications for the constraints on the density of the astrophysical neutrino sources.
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日本物理学会講演概要集 2014年8月22日 一般社団法人日本物理学会
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日本物理学会講演概要集 2014年8月22日 一般社団法人日本物理学会
共同研究・競争的資金等の研究課題
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日本学術振興会 科学研究費助成事業 2023年4月 - 2028年3月
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日本学術振興会 科学研究費助成事業 国際共同研究加速基金(国際共同研究強化(B)) 2020年10月 - 2025年3月
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日本学術振興会 科学研究費助成事業 研究活動スタート支援 2019年4月 - 2020年3月
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日本学術振興会 科学研究費助成事業 特別研究員奨励費 2006年 - 2008年