研究者業績
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受賞
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2022年2月
論文
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Astroparticle Physics 102 77-88 2018年11月1日A search for tau neutrino induced showers with the MAGIC telescopes is presented. The MAGIC telescopes located at an altitude of 2200 m a.s.l. in the Canary Island of La Palma, can point towards the horizon or a few degrees below across an azimuthal range of about 80°. This provides a possibility to search for air showers induced by tau leptons arising from interactions of tau neutrinos in the Earth crust or the surrounding ocean. In this paper we show how such air showers can be discriminated from the background of very inclined hadronic showers by using Monte Carlo simulations. Taking into account the orography of the site, the point source acceptance and the event rates expected have been calculated for a sample of generic neutrino fluxes from photo-hadronic interactions in AGNs. The analysis of about 30 h of data taken towards the sea leads to a 90% C.L. point source limit for tau neutrinos in the energy range from 1.0 × 1015 eV to 3.0 × 1018 eV of about Eντ 2×ϕ(Eντ )< 2.0×10−4 GeV cm−2 s−1 for an assumed power-law neutrino spectrum with spectral index γ=−2. However, with 300 h and in case of an optimistic neutrino flare model, limits of the level down to Eντ 2×ϕ(Eντ )< 8.4×10−6 GeV cm−2 s−1 can be expected.
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481(2) 2479-2486 2018年9月4日Fast radio bursts (FRBs) are bright flashes observed typically at GHz<br /> frequencies with millisecond duration, whose origin is likely extragalactic.<br /> Their nature remains mysterious, motivating searches for counterparts at other<br /> wavelengths. FRB 121102 is so far the only source known to repeatedly emit FRBs<br /> and is associated with a host galaxy at redshift $z \simeq 0.193$. We conducted<br /> simultaneous observations of FRB 121102 with the Arecibo and MAGIC telescopes<br /> during several epochs in 2016--2017. This allowed searches for<br /> millisecond-timescale burst emission in very-high-energy (VHE) gamma rays as<br /> well as the optical band. While a total of five FRBs were detected during these<br /> observations, no VHE emission was detected, neither of a persistent nature nor<br /> burst-like associated with the FRBs. The average integral flux upper limits<br /> above 100 GeV at 95% confidence level are $6.6 \times 10^{-12}~\mathrm{photons\<br /> cm^{-2}\ s^{-1 } }$ (corresponding to luminosity $L_{\rm VHE} \lesssim<br /> 10^{45}~\mathrm{erg\ s^{-1 } }$) over the entire observation period, and $1.2<br /> \times 10^{-7}~ \mathrm{photons\ cm^{-2}\ s^{-1 } }$ ($L_{\rm VHE} \lesssim<br /> 10^{49}~\mathrm{erg\ s^{-1 } }$) over the total duration of the five FRBs. We<br /> constrain the optical U-band flux to be below 8.6 mJy at 5-$\sigma$ level for<br /> 1-ms intervals around the FRB arrival times. A bright burst with U-band flux<br /> $29~\mathrm{mJy}$ and duration $\sim 12$ ms was detected 4.3 s before the<br /> arrival of one FRB. However, the probability of spuriously detecting such a<br /> signal within the sampled time space is 1.5% (2.2 $\sigma$, post-trial), i.e.<br /> consistent with the expected background. We discuss the implications of the<br /> obtained upper limits for constraining FRB models.
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2018年8月14日A multiwavelength campaign was organized to take place between March and July<br /> of 2012. Excellent temporal coverage was obtained with more than 25<br /> instruments, including the MAGIC, FACT and VERITAS Cherenkov telescopes, the<br /> instruments on board the Swift and Fermi spacecraft, and the telescopes<br /> operated by the GASP-WEBT collaboration.<br /> Mrk 501 showed a very high energy (VHE) gamma-ray flux above 0.2 TeV of<br /> $\sim$0.5 times the Crab Nebula flux (CU) for most of the campaign. The highest<br /> activity occurred on 2012 June 9, when the VHE flux was $\sim$3 CU, and the<br /> peak of the high-energy spectral component was found to be at $\sim$2 TeV. This<br /> study reports very hard X-ray spectra, and the hardest VHE spectra measured to<br /> date for Mrk 501. The fractional variability was found to increase with energy,<br /> with the highest variability occurring at VHE, and a significant correlation<br /> between the X-ray and VHE bands.<br /> The unprecedentedly hard X-ray and VHE spectra measured imply that their low-<br /> and high-energy components peaked above 5 keV and 0.5 TeV, respectively, during<br /> a large fraction of the observing campaign, and hence that Mrk 501 behaved like<br /> an extreme high-frequency- peaked blazar (EHBL) throughout the 2012 observing<br /> season. This suggests that being an EHBL may not be a permanent characteristic<br /> of a blazar, but rather a state which may change over time. The one-zone<br /> synchrotron self-Compton (SSC) scenario can successfully describe the segments<br /> of the SED where most energy is emitted, with a significant correlation between<br /> the electron energy density and the VHE gamma-ray activity, suggesting that<br /> most of the variability may be explained by the injection of high-energy<br /> electrons. The one-zone SSC scenario used reproduces the behaviour seen between<br /> the measured X-ray and VHE gamma-ray fluxes, and predicts that the correlation<br /> becomes stronger with increasing energy of the X-rays.
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Science 361, eaat1378 (2018) 361(6398) eaat1378-eaat1378 2018年7月24日Individual astrophysical sources previously detected in neutrinos are limited<br /> to the Sun and the supernova 1987A, whereas the origins of the diffuse flux of<br /> high-energy cosmic neutrinos remain unidentified. On 22 September 2017 we<br /> detected a high-energy neutrino, IceCube-170922A, with an energy of<br /> approximately 290 TeV. Its arrival direction was consistent with the location<br /> of a known gamma-ray blazar TXS 0506+056, observed to be in a flaring state. An<br /> extensive multi-wavelength campaign followed, ranging from radio frequencies to<br /> gamma-rays. These observations characterize the variability and energetics of<br /> the blazar and include the first detection of TXS 0506+056 in very-high-energy<br /> gamma-rays. This observation of a neutrino in spatial coincidence with a<br /> gamma-ray emitting blazar during an active phase suggests that blazars may be a<br /> source of high-energy neutrinos.
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The Astrophysical Journal Letters, 863 (2018) L10 863(1) L10-L10 2018年7月12日A neutrino with energy of $\sim$290 TeV, IceCube-170922A, was detected in<br /> coincidence with the BL Lac object TXS~0506+056 during enhanced gamma-ray<br /> activity, with chance coincidence being rejected at $\sim 3\sigma$ level. We<br /> monitored the object in the very-high-energy (VHE) band with the MAGIC<br /> telescopes for $\sim$41 hours from 1.3 to 40.4 days after the neutrino<br /> detection. Day-timescale variability is clearly resolved. We interpret the<br /> quasi-simultaneous neutrino and broadband electromagnetic observations with a<br /> novel one-zone lepto-hadronic model, based on interactions of electrons and<br /> protons co-accelerated in the jet with external photons originating from a<br /> slow-moving plasma sheath surrounding the faster jet spine. We can reproduce<br /> the multiwavelength spectra of TXS 0506+056 with neutrino rate and energy<br /> compatible with IceCube-170922A, and with plausible values for the jet power of<br /> $\sim 10^{45} - 4 \times 10^{46} {\rm erg \ s^{-1 } }$. The steep spectrum<br /> observed by MAGIC is concordant with internal $\gamma\gamma$ absorption above a<br /> few tens of GeV entailed by photohadronic production of a $\sim$290 TeV<br /> neutrino, corroborating a genuine connection between the multi-messenger<br /> signals. In contrast to previous predictions of predominantly hadronic emission<br /> from neutrino sources, the gamma-rays can be mostly ascribed to inverse Compton<br /> up-scattering of external photons by accelerated electrons. The X-ray and VHE<br /> bands provide crucial constraints on the emission from both accelerated<br /> electrons and protons. We infer that the maximum energy of protons in the jet<br /> co-moving frame can be in the range $\sim 10^{14}$ to $10^{18}$ eV.
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Monthly Notices of the Royal Astronomical Society, Volume 480, Issue 1, 11 October 2018, Pages 879-892 480(1) 879-892 2018年7月6日The MAGIC telescopes observed S2 0109+22 in 2015 July during its flaring<br /> activity in high energy gamma rays observed by Fermi-LAT. We analyse the MAGIC<br /> data to characterise the very high energy (VHE) gamma-ray emission of S2<br /> 0109+22, which belongs to the subclass of intermediate synchrotron peak (ISP)<br /> BL Lac objects. We study the multi-frequency emission in order to investigate<br /> the source classification. Finally, we compare the source long-term behaviour<br /> to other VHE gamma-ray emitting (TeV) blazars. We performed a temporal and<br /> spectral analysis of the data centred around the MAGIC interval of observation<br /> (MJD 57225-57231). Long-term radio and optical data have also been investigated<br /> using the discrete correlation function. The redshift of the source is<br /> estimated through optical host-galaxy imaging and also using the amount of VHE<br /> gamma-ray absorption. The quasi-simultaneous multi-frequency spectral energy<br /> distribution (SED) is modelled with the conventional one-zone synchrotron<br /> self-Compton (SSC) model. MAGIC observations resulted in the detection of the<br /> source at a significance level of $5.3\,\sigma$. The VHE gamma-ray emission of<br /> S2 0109+22 is variable on a daily time scale. VHE gamma-ray luminosity of the<br /> source is lower than the average of TeV BL Lacs. The optical polarization, and<br /> long-term optical/radio behaviour of the source are different from the general<br /> population of TeV blazars. All these findings agree with the classification of<br /> the source as an ISP BL Lac object. We estimate the source redshift as $z =<br /> 0.36 \pm 0.07$. The SSC parameters describing the SED are rather typical for<br /> blazars.
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2018年7月2日The BL Lac object S5~0716+714, a highly variable blazar, underwent an<br /> impressive outburst in January 2015 (Phase A), followed by minor activity in<br /> February (Phase B). The MAGIC observations were triggered by the optical flux<br /> observed in Phase A, corresponding to the brightest ever reported state of the<br /> source in the R-band. The comprehensive dataset collected is investigated in<br /> order to shed light on the mechanism of the broadband emission.<br /> Multi-wavelength light curves have been studied together with the broadband<br /> Spectral Energy Distributions (SEDs). The data set collected spans from radio,<br /> optical photometry and polarimetry, X-ray, high-energy (HE, 0.1 GeV < E < 100<br /> GeV) with \textit{Fermi}-LAT to the very-high-energy (VHE, E>100 GeV) with<br /> MAGIC. The flaring state of Phase A was detected in all the energy bands,<br /> providing for the first time a multi-wavelength sample of simultaneous data<br /> from the radio band to the VHE. In the constructed SED the<br /> \textit{Swift}-XRT+\textit{NuSTAR} data constrain the transition between the<br /> synchrotron and inverse Compton components very accurately, while the second<br /> peak is constrained from 0.1~GeV to 600~GeV by \textit{Fermi}+MAGIC data. The<br /> broadband SED cannot be described with a one-zone synchrotron self-Compton<br /> model as it severely underestimates the optical flux in order to reproduce the<br /> X-ray to $\gamma$-ray data. Instead we use a two-zone model. The EVPA shows an<br /> unprecedented fast rotation. An estimation of the redshift of the source by<br /> combined HE and VHE data provides a value of $z = 0.31 \pm 0.02_{stats} \pm<br /> 0.05_{sys}$, confirming the literature value. The data show the VHE emission<br /> originating in the entrance and exit of a superluminal knot in and out a<br /> recollimation shock in the inner jet. A shock-shock interaction in the jet<br /> seems responsible for the observed flares and EVPA swing. This scenario is also<br /> consistent with the SED modelling.
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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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日本物理学会講演概要集 72.1 460-460 2017年宇宙線スペクトルのknee領域(<10^16^ eV)までは銀河系内の超新星残骸からの寄与が大きいと考えられ、その粒子加速現場では、レプトン起源の逆コンプトン散乱、制動放射や、ハドロン同士の相互作用により生じたパイオンの崩壊からの超高エネルギー(VHE)ガンマ線放射が期待される。現在までに約20の超新星残骸からVHEガンマ線が観測され、内5天体がMAGIC望遠鏡で検出されている。本講演ではMAGICで検出した超新星残骸を概観し、多波長の観測結果と合わせガンマ線放射起源を議論する。
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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.
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