Faculty Profiles - TAJIMA, Hiroyasu

Papers - TAJIMA, Hiroyasu

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The Gamma-ray Cherenkov Telescope for the Cherenkov Telescope Array Reviewed

Tibaldo L., Abchiche A., Allan D., Amans J. -P., Armstrong T. P., Balzer A., Bergey D., Boisson C., Bousquet J. -J., Brown A. M., Bryan M., Buchholtz G., Chadwick P. M., Costantini H., Cotter G., Daniels M. K., De Franco A., De Frondat F., Dournaux J. -L., Dumas D., Ernenwein J. -P., Fasola G., Funk S., Gironnet J., Graham J. A., Greenshaws T., Hervet O., Hidaka N., Hintoni J. A., Huet J. -M., Jankowsky D., Jegouzo I., Jogler T., Kraus M., Lapington J. S., Laporte P., Lefaucheur J., Markoff S., Melse T., Mohrmann L., Molyneux P., Nolan S. J., Okumura A., Osborne J. P., Parsons R. D., Rosen S., Ross D., Rowell G., Rulten C. B., Sato Y., Sayede F., Schmoll J., Schoorlemmer H., Servillat M., Sol H., Stamatescu V., Stephan M., Stuik R., Sykes J., Tajima H., Thornhill J., Trichard C., Vink J., Watson J. J., White R., Yamane N., Zech A., Zink A., Zorn J.

HIGH ENERGY GAMMA-RAY ASTRONOMY Vol. 1792 2017

Study of the polarimetric performance of a Si/CdTe semiconductor Compton camera for the Hitomi satellite Reviewed

J. Katsuta et al.

Vol. 840 page： 51-58 2016.12

The quiescent intracluster medium in the core of the Perseus cluster Reviewed

Hitomi collaboration

Nature Vol. 535 ( 7610 ) page： 117-121 2016.7

The First Fermi LAT Supernova Remnant Catalog Reviewed

Fermi LAT collaboration

The Astrophysical Journal Supplement Series Vol. 224 ( 1 ) page： article id. 8 2016.5

Fermi-LAT Observations of High-Energy Gamma-Ray Emission toward the Galactic Center Reviewed

Fermi LAT collaboration

Vol. 819 ( 1 ) page： article id. 44 2016.3

The first demonstration of the concept of "narrow-FOV Si/CdTe semiconductor Compton camera" Reviewed

Y. Ichinohe, et al.

Nuclear Inst. and Methods in Physics Research, A Vol. 806 page： 5-13 2016.1

Searching for Dark Matter Annihilation from Milky Way Dwarf Spheroidal Galaxies with Six Years of Fermi Large Area Telescope Data Reviewed

Fermi LAT collaboration

Physical Review Letters Vol. 115 page： 231301 2015.11

Language：English Publishing type：Research paper (scientific journal)

The dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are some of the most dark matter (DM) dominated objects known. We report on gamma-ray observations of Milky Way dSphs based on six years of Fermi Large Area Telescope data processed with the new Pass8 event-level analysis. None of the dSphs are significantly detected in gamma rays, and we present upper limits on the DM annihilation cross section from a combined analysis of 15 dSphs. These constraints are among the strongest and most robust to date and lie below the canonical thermal relic cross section for DM of mass <100 GeV annihilating via quark and tau-lepton channels.

DOI： 10.1103/PhysRevLett.115.231301

First Images from the Focusing Optics X-Ray Solar Imager Reviewed

FOXSI collaboration

The Astrophysical Journal Letters Vol. 793 page： L32 2014.9

Language：English Publishing type：Research paper (scientific journal)

The Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket payload flew for the first time on 2012 November 2, producing the first focused images of the Sun above 5 keV. To enable hard X-ray (HXR) imaging spectroscopy via direct focusing, FOXSI makes use of grazing-incidence replicated optics combined with fine-pitch solid-state detectors. On its first flight, FOXSI observed several targets that included active regions, the quiet Sun, and a GOES-class B2.7 microflare. This Letter provides an introduction to the FOXSI instrument and presents its first solar image. These data demonstrate the superiority in sensitivity and dynamic range that is achievable with a direct HXR imager with respect to previous, indirect imaging methods, and illustrate the technological readiness for a spaceborne mission to observe HXRs from solar flares via direct focusing optics.

DOI： 10.1088/2041-8205/793/2/L32

Introducing the CTA concept Reviewed

CTA consortium

Astroparticle Physics Vol. 43 page： 3-18 2013.3

Language：English Publishing type：Research paper (scientific journal)

The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project.

DOI： 10.1016/j.astropartphys.2013.01.007

Detection of the Characteristic Pion-Decay Signature in Supernova Remnants Reviewed

Fermi LAT collaboration

Science Vol. 339 page： 807-811 2013.2

Language：English Publishing type：Research paper (scientific journal)

Cosmic rays are particles (mostly protons) accelerated to relativistic speeds. Despite wide agreement that supernova remnants (SNRs) are the sources of galactic cosmic rays, unequivocal evidence for the acceleration of protons in these objects is still lacking. When accelerated protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma rays. This offers a compelling way to detect the acceleration sites of protons. The identification of pion-decay gamma rays has been difficult because high-energy electrons also produce gamma rays via bremsstrahlung and inverse Compton scattering. We detected the characteristic pion-decay feature in the gamma-ray spectra of two SNRs, IC 443 and W44, with the Fermi Large Area Telescope. This detection provides direct evidence that cosmic-ray protons are accelerated in SNRs.

DOI： 10.1126/science.1231160

TARGET: A multi-channel digitizer chip for very-high-energy gamma-ray telescopes Reviewed

Bechtol, K.; Funk, S.; Okumura, A.; Ruckman, L. L.; Simons, A.; Tajima, H.; Vandenbroucke, J.; Varner, G. S.

Astroparticle Physics Vol. 36 page： 156-165 2012.8

Language：English Publishing type：Research paper (scientific journal)

The next-generation very-high-energy (VHE) gamma-ray observatory, the Cherenkov Telescope Array, will feature dozens of imaging atmospheric Cherenkov telescopes (IACTs), each with thousands of pixels of photo-sensors. To be affordable and reliable, reading out such an array of up to a million channels requires event recording technology that is highly integrated and modular, with a low cost per channel. We present the design and performance of a chip targeted to this application: the TeV Array Readout with GSa/s sampling and Event Trigger (TARGET). This application-specific integrated circuit (ASIC) has 16 parallel input channels, a 4096-sample buffer for each channel, adjustable input termination, self-trigger functionality, and tight window-selected readout. We report the performance of the first-generation version of this chip (TARGET 1) in terms of sampling frequency, power consumption, dynamic range, current-mode gain, analog bandwidth, and cross talk. The large number of channels per chip allows a low cost per channel (10 to 20 including front-end and back-end electronics but not including photosensors) to be achieved with a TARGET-based IACT readout system. In addition to basic performance parameters of the TARGET 1 chip, we present a camera module prototype as well as a second-generation chip (TARGET 2), both of which have now been produced.

DOI： 10.1016/j.astropartphys.2012.05.016

Fermi Large Area Telescope Discovery of GeV Gamma-Ray Emission from the Vicinity of SNR W44 Reviewed

Uchiyama, Yasunobu; Funk, Stefan; Katagiri, Hideaki; Katsuta, Junichiro; Lemoine-Goumard, Marianne; Tajima, Hiroyasu; Tanaka, Takaaki; Torres, Diego F.

The Astrophysical Journal Letters Vol. 749 page： L35 2012.4

Language：English Publishing type：Research paper (scientific journal)

We report the detection of GeV gamma-ray emission from the molecular cloud complex that surrounds the supernova remnant (SNR) W44 using the Large Area Telescope on board Fermi. While the previously reported gamma-ray emission from SNR W44 is likely to arise from the dense radio-emitting filaments within the remnant, the gamma-ray emission that appears to come from the surrounding molecular cloud complex can be ascribed to the cosmic rays (CRs) that have escaped from W44. The non-detection of synchrotron radio emission associated with the molecular cloud complex suggests the decay of pi0 mesons produced in hadronic collisions as the gamma-ray emission mechanism. The total kinetic energy channeled into the escaping CRs is estimated to be Wesc ~ (0.3-3) x 10^50 erg, in broad agreement with the conjecture that SNRs are the main sources of Galactic CRs.

DOI： 10.1088/2041-8205/749/2/L35

Gamma-Ray Observations of the Supernova Remnant RX J0852.0-4622 with the Fermi Large Area Telescope Reviewed

Tanaka, T.; Allafort, A.; Ballet, J.; Funk, S.; Giordano, F.; Hewitt, J.; Lemoine-Goumard, M.; Tajima, H.; Tibolla, O.; Uchiyama, Y.

The Astrophysical Journal Letters Vol. 740 page： L51 2011.10

Language：English Publishing type：Research paper (scientific journal)

We report on gamma-ray observations of the supernova remnant (SNR) RX J0852.0-4622 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. In the Fermi-LAT data, we find a spatially extended source at the location of the SNR. The extension is consistent with the SNR size seen in other wavelengths such as X-rays and TeV gamma rays, leading to the identification of the gamma-ray source with the SNR. The spectrum is well described as a power law with a photon index of 1.85±0.06 (stat)+0.18-0.19 (sys), which smoothly connects to the H.E.S.S. spectrum in the TeV energy band. We discuss the gamma-ray emission mechanism based on multiwavelength data. The broadband data can be fit well by a model in which the gamma rays are of hadronic origin. We also consider a scenario with inverse Compton scattering of electrons as the emission mechanism of the gamma rays. Although the leptonic model predicts a harder spectrum in the Fermi-LAT energy range, the model can fit the data considering the statistical and systematic errors.

DOI： 10.1088/2041-8205/740/2/L51

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