Faculty Profiles - TAJIMA, Hiroyasu

Papers - TAJIMA, Hiroyasu

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Fine-Pitch Semiconductor Detector for the FOXSI Mission Reviewed

Ishikawa, S.; Saito, S.; Tajima, H.; Tanaka, T.; Watanabe, S.; Odaka, H.; Fukuyama, T.; Kokubun, M.; Takahashi, T.; Terada, Y.; Krucker, S.; Christe, S.; McBride, S.; Glesener, L.

IEEE Transactions on Nuclear Science Vol. 58 page： 2039-2046 2011.8

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The Focusing Optics X-ray Solar Imager (FOXSI) is a NASA sounding rocket mission which will study particle acceleration and coronal heating on the Sun through high sensitivity observations in the hard X-ray energy band (5-15 keV). Combining high-resolution focusing X-ray optics and fine-pitch imaging sensors, FOXSI will achieve superior sensitivity; two orders of magnitude better than that of the RHESSI satellite. As the focal plane detector, a Double-sided Si Strip Detector (DSSD) with a front-end ASIC (Application Specific Integrated Circuit) will fulfill the scientific requirements of spatial and energy resolution, low energy threshold and time resolution. We have designed and fabricated a DSSD with a thickness of 500 µm and a dimension of 9.6 mm x 9.6 mm, containing 128 strips with a pitch of 75 µm, which corresponds to 8 arcsec at the focal length of 2 m. We also developed a low-noise ASIC specified to FOXSI. The detector was successfully operated in the laboratory at a temperature of -20 C and with an applied bias voltage of 300 V, and the energy resolution of 430 eV at a 14 keV line was achieved. We also demonstrated fine-pitch imaging successfully by obtaining a shadow image, hence the implementation of scientific requirements was confirmed.

DOI： 10.1109/TNS.2011.2154342

Gamma-Ray Emission from the Shell of Supernova Remnant W44 Revealed by the Fermi LAT Reviewed International coauthorship

Fermi LAT collaboration

Science Vol. 327 page： 1103 2010.2

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)

Recent observations of supernova remnants (SNRs) hint that they accelerate cosmic rays to energies close to ~1015 electron volts. However, the nature of the particles that produce the emission remains ambiguous. We report observations of SNR W44 with the Fermi Large Area Telescope at energies between 2 × 10^8 electron volts and 3 ×10^q11 electron volts. The detection of a source with a morphology corresponding to the SNR shell implies that the emission is produced by particles accelerated there. The gamma-ray spectrum is well modeled with emission from protons and nuclei. Its steepening above ~10^9 electron volts provides a probe with which to study how particle acceleration responds to environmental effects such as shock propagation in dense clouds and how accelerated particles are released into interstellar space.

DOI： 10.1126/science.1182787

A limit on the variation of the speed of light arising from quantum gravity effects Reviewed International coauthorship

Fermi LAT/GBM collaborations

Nature Vol. 462 page： 331-334 2009.11

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

A cornerstone of Einstein's special relativity is Lorentz invariance - the postulate that all observers measure exactly the same speed of light in vacuum, independent of photon-energy. While special relativity assumes that there is no fundamental length-scale associated with such invariance, there is a fundamental scale (the Planck scale, lPlanck~1.62×10^-33cm or EPlanck = MPlanck~1.22×10^19GeV/c2), at which quantum effects are expected to strongly affect the nature of space-time. There is great interest in the (not yet validated) idea that Lorentz invariance might break near the Planck scale. A key test of such violation of Lorentz invariance is a possible variation of photon speed with energy. Even a tiny variation in photon speed, when accumulated over cosmological light-travel times, may be revealed by observing sharp features in γ-ray burst (GRB) light-curves. Here we report the detection of emission up to ~31GeV from the distant and short GRB090510. We find no evidence for the violation of Lorentz invariance, and place a lower limit of 1.2EPlanck on the scale of a linear energy dependence (or an inverse wavelength dependence), subject to reasonable assumptions about the emission (equivalently we have an upper limit of lPlanck/1.2 on the length scale of the effect). Our results disfavour quantum-gravity theories in which the quantum nature of space-time on a very small scale linearly alters the speed of light.

DOI： 10.1038/nature08574

The on-orbit calibration of the Fermi Large Area Telescope Reviewed International coauthorship

Fermi LAT collaboration

Astroparticle Physics Vol. 32 page： 193-219 2009.10

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

The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope began its on-orbit operations on June 23, 2008. Calibrations, defined in a generic sense, correspond to synchronization of trigger signals, optimization of delays for latching data, determination of detector thresholds, gains and responses, evaluation of the perimeter of the South Atlantic Anomaly (SAA), measurements of live time, of absolute time, and internal and spacecraft boresight alignments. Here we describe on-orbit calibration results obtained using known astrophysical sources, galactic cosmic rays, and charge injection into the front-end electronics of each detector. Instrument response functions will be described in a separate publication. This paper demonstrates the stability of calibrations and describes minor changes observed since launch. These results have been used to calibrate the LAT datasets to be publicly released in August 2009.

DOI： 10.1016/j.astropartphys.2009.08.002

Fermi Observations of High-Energy Gamma-Ray Emission from GRB 080916C Reviewed International coauthorship

Fermi LAT/GBM collaborations

Science Vol. 323 page： 1688-1693 2009.3

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)

Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades of gamma-ray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass.

DOI： 10.1126/science.1169101

The variability patterns of the TeV blazar PG 1553 + 113 from a decade of MAGIC and multiband observations Reviewed

Abe H., Abe S., Abhir J., Acciari V.A., Agudo I., Aniello T., Ansoldi S., Antonelli L.A., Arbet Engels A., Arcaro C., Artero M., Asano K., Baack D., Babić A., Baquero A., Barres de Almeida U., Batković I., Baxter J., Becerra González J., Bernardini E., Bernete J., Berti A., Besenrieder J., Bigongiari C., Biland A., Blanch O., Bonnoli G., Bošnjak , Burelli I., Busetto G., Campoy-Ordaz A., Carosi A., Carosi R., Carretero-Castrillo M., Castro-Tirado A.J., Chai Y., Cifuentes A., Cikota S., Colombo E., Contreras J.L., Cortina J., Covino S., D’Amico G., D’Elia V., Da Vela P., Dazzi F., De Angelis A., De Lotto B., Del Popolo A., Delfino M., Delgado J., Delgado Mendez C., Depaoli D., Di Pierro F., Di Venere L., Dominis Prester D., Donini A., Dorner D., Doro M., Elsaesser D., Emery G., Escudero J., Fariña L., Fattorini A., Foffano L., Font L., Fukami S., Fukazawa Y., García López R.J., Gasparyan S., Gaug M., Giesbrecht Paiva J.G., Giglietto N., Giordano F., Gliwny P., Grau R., Green J.G., Hadasch D., Hahn A., Heckmann L., Herrera J., Hovatta T., Hrupec D., Hütten M., Imazawa R., Inada T., Iotov R., Ishio K., Jimenez Martínez I., Jormanainen J., Kerszberg D., Kluge G.W., Kobayashi Y., Kouch P.M., Kubo H., Kushida J., Láinez Lezáun M., Lamastra A., Leone F., Lindfors E.

Monthly Notices of the Royal Astronomical Society Vol. 529 ( 4 ) page： 3894 - 3911 2024.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Monthly Notices of the Royal Astronomical Society

PG 1553 + 113 is one of the few blazars with a convincing quasi-periodic emission in the gamma-ray band. The source is also a very high energy (VHE; >100 GeV) gamma-ray emitter. To better understand its properties and identify the underlying physical processes driving its variability, the MAGIC Collaboration initiated a multiyear, multiwavelength monitoring campaign in 2015 involving the OVRO 40-m and Medicina radio telescopes, REM, KVA, and the MAGIC telescopes, Swift and Fermi satellites, and the WEBT network. The analysis presented in this paper uses data until 2017 and focuses on the characterization of the variability. The gamma-ray data show a (hint of a) periodic signal compatible with literature, but the X-ray and VHE gamma-ray data do not show statistical evidence for a periodic signal. In other bands, the data are compatible with the gamma-ray period, but with a relatively high p-value. The complex connection between the low- and high-energy emission and the non-monochromatic modulation and changes in flux suggests that a simple one-zone model is unable to explain all the variability. Instead, a model including a periodic component along with multiple emission zones is required.

DOI： 10.1093/mnras/stae649

Scopus

AstroPix4 — a novel HV-CMOS sensor developed for space based experiments Reviewed

Striebig N., Leys R., Peric I., Caputo R., Steinhebel A.L., Suda Y., Fukazawa Y., Jadhav M., Violette D., Kierans C., Tajima H., Metcalfe J., Perkins J.S.

Journal of Instrumentation Vol. 19 ( 4 ) 2024.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Instrumentation

For the proposed space based gamma-ray observatory All-sky Medium-Energy Gamma-ray Observatory eXplorer (AMEGO-X), a silicon tracker based on a novel High Voltage-CMOS (HV-CMOS) sensor called AstroPix, is currently being developed. Preliminary measurements with the first full reticle prototype AstroPix3 show that the power target of 1.5 mW/cm2 can currently not be reached due to the digital consumption of 3.08 mW/cm2, while the analog power consumption of 1.04 mW/cm2 and a break down voltage of over 350 V look promising. Based on these results, the design changes in AstroPix4, submitted in May 2023, are presented, containing changes to the time stamp generation and readout architecture. A digital power consumption below 0.25 mW/cm2 is expected by removing the fast 200 MHz clock used to measure the time-over-threshold (ToT) and an LVDS receiver. A maximum resolution of 3.125 ns for time-of-arrival (ToA) and ToT is reached by adding per-pixel Flash-Time-to-Digital Converter (TDCs) controlled by a global delay-locked loop (DLL).

DOI： 10.1088/1748-0221/19/04/C04010

Scopus

Silicon photomultipliers for the SST camera of the Cherenkov Telescope Array Reviewed

Depaoli D., Lapington J., Leach S., Okumura A., Sofia I., Tajima H.

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Vol. 1060 2024.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

The Cherenkov Telescope Array Observatory (CTAO) will be the major global observatory for gamma-ray astronomy over the next decade and beyond. It will consist of two arrays of telescopes of different sizes, one for each hemisphere, and will be sensitive to gamma rays in the energy range from a few tens of GeV to hundreds of TeV. The Small-Sized Telescopes (SSTs) are a crucial component of the southern array, as they will extend the sensitivity of the observatory to the highest energies. Their focal plane will be equipped with 2048 Silicon Photomultiplier (SiPM) pixels, each one read independently by a state-of-the-art full waveform sampling readout. These solid-state sensors offer advantages over the traditional photomultiplier tubes, such as lower operating voltage, higher photon detection efficiency, and tolerance to bright illumination. In particular, they are the best choice for a small and compact camera such as the SST one. After a detailed comparative study, LVR3-type SiPMs from Hamamatsu Photonics were selected, with an active area of 6 mm × 6 mm, a microcell of 50 μm and without a protective coating, for optimum performance. The sensors demonstrated to have a higher photon detection efficiency and a lower crosstalk compared to the competitors, alongside a low dark count rate. In this contribution, we present the selection process and the latest measurements performed on the SiPMs mounted on the SST Camera module.

DOI： 10.1016/j.nima.2023.169047

Scopus

Multi-year characterisation of the broad-band emission from the intermittent extreme BL Lac 1ES 2344+514 Invited International coauthorship

Abe, H. et al.

Astronomy & Astrophysics, Volume Vol. 682 page： A114 2024.2

MAGIC detection of GRB 201216C at z = 1.1 Reviewed

Abe H., Abe S., Acciari V.A., Agudo I., Aniello T., Ansoldi S., Antonelli L.A., Arbet Engels A., Arcaro C., Artero M., Asano K., Baack D., Babić A., Baquero A., Barres de Almeida U., Barrio J.A., Batković I., Baxter J., Becerra González J., Bednarek W., Bernardini E., Bernete J., Berti A., Besenrieder J., Bigongiari C., Biland A., Blanch O., Bonnoli G., Bošnjak , Burelli I., Busetto G., Campoy-Ordaz A., Carosi A., Carosi R., Carretero-Castrillo M., Castro-Tirado A.J., Ceribella G., Chai Y., Cifuentes A., Cikota S., Colombo E., Contreras J.L., Cortina J., Covino S., D’Amico G., D’Elia V., Da Vela P., Dazzi F., De Angelis A., De Lotto B., Del Popolo A., Delfino M., Delgado J., Delgado Mendez C., Depaoli D., Di Pierro F., Di Venere L., Dominis Prester D., Donini A., Dorner D., Doro M., Elsaesser D., Emery G., Escudero J., Fariña L., Fattorini A., Foffano L., Font L., Fukami S., Fukazawa Y., García López R.J., Garczarczyk M., Gasparyan S., Gaug M., Giesbrecht Paiva J.G., Giglietto N., Giordano F., Gliwny P., Godinović N., Grau R., Green D., Green J.G., Hadasch D., Hahn A., Hassan T., Heckmann L., Herrera J., Hrupec D., Hütten M., Imazawa R., Inada T., Iotov R., Ishio K., Jiménez Martínez I., Jormanainen J., Kerszberg D., Kluge G.W., Kobayashi Y., Kouch P.M., Kubo H.

Monthly Notices of the Royal Astronomical Society Vol. 527 ( 3 ) page： 5856 - 5867 2024.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Monthly Notices of the Royal Astronomical Society

Gamma-ray bursts (GRBs) are explosive transient events occurring at cosmological distances, releasing a large amount of energy as electromagnetic radiation over several energy bands. We report the detection of the long GRB 201216C by the MAGIC telescopes. The source is located at z = 1.1 and thus it is the farthest one detected at very high energies. The emission above 70 GeV of GRB 201216C is modelled together with multiwavelength data within a synchrotron and synchrotron self-Compton (SSC) scenario. We find that SSC can explain the broad-band data well from the optical to the very-high-energy band. For the late-time radio data, a different component is needed to account for the observed emission. Differently from previous GRBs detected in the very-high-energy range, the model for GRB 201216C strongly favours a wind-like medium. The model parameters have values similar to those found in past studies of the afterglows of GRBs detected up to GeV energies.

DOI： 10.1093/mnras/stad2958

Scopus

Performance of the joint LST-1 and MAGIC observations evaluated with Crab Nebula data Reviewed

Abe H., Abe K., Abe S., Acciari V.A., Aguasca-Cabot A., Agudo I., Alvarez Crespo N., Aniello T., Ansoldi S., Antonelli L.A., Aramo C., Arbet-Engels A., Arcaro C., Artero M., Asano K., Aubert P., Baack D., Babić A., Baktash A., Bamba A., Baquero Larriva A., Baroncelli L., Barres De Almeida U., Barrio J.A., Batković I., Baxter J., Becerra González J., Bednarek W., Bernardini E., Bernardos M.I., Bernete Medrano J., Berti A., Besenrieder J., Bhattacharjee P., Biederbeck N., Bigongiari C., Biland A., Bissaldi E., Blanch O., Bonnoli G., Bordas P., Bošnjak , Bulgarelli A., Burelli I., Burmistrov L., Buscemi M., Busetto G., Campoy Ordaz A., Cardillo M., Caroff S., Carosi A., Carosi R., Carrasco M.S., Carretero-Castrillo M., Cassol F., Castro-Tirado A.J., Cauz D., Cerasole D., Ceribella G., Chai Y., Cheng K., Chiavassa A., Chikawa M., Chytka L., Cifuentes A., Cikota S., Colombo E., Contreras J.L., Cornelia A., Cortina J., Costantini H., Covino S., D'Amico G., D'Elia V., Da Vela P., Dalchenko M., Dazzi F., De Angelis A., De Bony De Lavergne M., De Lotto B., De Lucia M., De Menezes R., Del Peral L., Del Popolo A., Deleglise G., Delfino M., Delgado Mendez C., Delgado Mengual J., Della Volpe D., Dellaiera M., Depaoli D., De Angelis A., Di Piano A., Di Pierro F., Di Pilato A., Di Tria R., Di Venere L., Dominik R.M., Dominis Prester D., Donini A.

Astronomy and Astrophysics Vol. 680 2023.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Astronomy and Astrophysics

Aims. Large-Sized Telescope 1 (LST-1), the prototype for the Large-Sized Telescope at the upcoming Cherenkov Telescope Array Observatory, is concluding its commissioning phase at the Observatorio del Roque de los Muchachos on the island of La Palma. The proximity of LST-1 to the two MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescopes makes it possible to carry out observations of the same gamma-ray events with both systems. Methods. We describe the joint LST-1+MAGIC analysis pipeline and used simultaneous Crab Nebula observations and Monte Carlo simulations to assess the performance of the three-telescope system. The addition of the LST-1 telescope allows for the recovery of events in which one of the MAGIC images is too dim to survive analysis quality cuts. Results. Thanks to the resulting increase in the collection area and stronger background rejection, we found a significant improvement in sensitivity, allowing for the detection of 30% weaker fluxes in the energy range between 200 GeV and 3 TeV. The spectrum of the Crab Nebula, reconstructed in the energy range between ∼60 GeV and ∼10 TeV, is in agreement with previous measurements.

DOI： 10.1051/0004-6361/202346927

Scopus

The Third Fermi Large Area Telescope Catalog of Gamma-Ray Pulsars Reviewed

Smith, D. A. et al.

Astrophysical Journal Vol. 958 ( 2 ) page： 191 2023.12

Star tracking for pointing determination of Imaging Atmospheric Cherenkov Telescopes: Application to the Large-Sized Telescope of the Cherenkov Telescope Array Reviewed

Abe K., Abe S., Aguasca-Cabot A., Agudo I., Alvarez Crespo N., Antonelli L.A., Aramo C., Arbet-Engels A., Cornelia A., Artero M., Asano K., Aubert P., Baktash A., Bamba A., Baquero Larriva A., Baroncelli L., Barres De Almeida U., Barrio J.A., Batkovic I., Baxter J., Becerra González J., Bernardini E., Bernardos M.I., Bernete Medrano J., Berti A., Bhattacharjee P., Biederbeck N., Bigongiari C., Bissaldi E., Blanch O., Bonnoli G., Bordas P., Bulgarelli A., Burelli I., Burmistrov L., Buscemi M., Cardillo M., Caroff S., Carosi A., Cassol F., Cauz D., Ceribella G., Chai Y., Cheng K., Chiavassa A., Chikawa M., Chytka L., Cifuentes A., Contreras J.L., Cortina J., Costantini H., Dalchenko M., De Angelis A., De Bony De Lavergne M., De Lotto B., De Menezes R., Deleglise G., Delgado C., Delgado Mengual J., Della Volpe D., Dellaiera M., Di Piano A., Di Pierro F., Di Tria R., Di Venere L., Díaz C., Dominik R.M., Dominis Prester D., Donini A., Dorner D., Doro M., Elsässer D., Emery G., Escudero J., Fallah Ramazani V., Ferrara G., Ferrarotto F., Fiasson A., Freixas Coromina L., Fröse S., Fukami S., Fukazawa Y., Garcia E., Garcia López R., Gasbarra C., Gasparrini D., Geyer D., Giesbrecht Paiva J., Giglietto N., Giordano F., Giro E., Gliwny P., Godinovic N., Grau R., Green D., Green J., Gunji S., Günther P., Hackfeld J., Hadasch D.

Astronomy and Astrophysics Vol. 679 2023.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Astronomy and Astrophysics

We present a novel approach to the determination of the pointing of Imaging Atmospheric Cherenkov Telescopes (IACTs) using the trajectories of the stars in their camera s field of view. The method starts with the reconstruction of the star positions from the Cherenkov camera data, taking into account the point spread function of the telescope, to achieve a satisfying reconstruction accuracy of the pointing position. A simultaneous fit of all reconstructed star trajectories is then performed with the orthogonal distance regression (ODR) method. ODR allows us to correctly include the star position uncertainties and use the time as an independent variable. Having the time as an independent variable in the fit makes it better suitable for various star trajectories. This method can be applied to any IACT and requires neither specific hardware nor interface or special data-taking mode. In this paper, we use the Large-Sized Telescope (LST) data to validate it as a useful tool to improve the determination of the pointing direction during regular data taking. The simulation studies show that the accuracy and precision of the method are comparable with the design requirements on the pointing accuracy of the LST (=14''). With the typical LST event acquisition rate of 10 kHz, the method can achieve up to 50 Hz pointing monitoring rate, compared to O(1) Hz achievable with standard techniques. The application of the method to the LST prototype (LST-1) commissioning data shows the stable pointing performance of the telescope.

DOI： 10.1051/0004-6361/202347128

Scopus

Observations of the Crab Nebula and Pulsar with the Large-sized Telescope Prototype of the Cherenkov Telescope Array Invited International coauthorship

The Astrophysical Journal Vol. 956 ( 2 ) page： 80 2023.10

Fermi-GBM Discovery of GRB 221009A: An Extraordinarily Bright GRB from Onset to Afterglow Reviewed International coauthorship

Lesage, S. et al.

The Astrophysical Journal Letters Vol. 952 ( 2 ) page： L42 2023.8

Sensitivity of the Cherenkov Telescope Array to spectral signatures of hadronic PeVatrons with application to Galactic Supernova Remnants Reviewed

Acero F., Acharyya A., Adam R., Aguasca-Cabot A., Agudo I., Aguirre-Santaella A., Alfaro J., Aloisio R., Crespo N.Á., Batista R.A., Amati L., Amato E., Ambrosi G., Angüner E.O., Aramo C., Arcaro C., Armstrong T., Asano K., Ascasibar Y., Aschersleben J., Backes M., Baktash A., Balazs C., Balbo M., Ballet J., Larriva A.B., Martins V.B., de Almeida U.B., Barrio J.A., Bastieri D., Baxter J.R., Tjus J.B., Benbow W., Bernardos-Martín M.I., Bernete J., Berti A., Bertucci B., Beshley V., Bhattacharjee P., Bhattacharyya S., Biland A., Bissaldi E., Biteau J., Blanch O., Bordas P., Bottacini E., Bregeon J., Brose R., Bucciantini N., Bulgarelli A., Capasso M., Dolcetta R.A.C., Caraveo P., Cardillo M., Carosi R., Casanova S., Cascone E., Cassol F., Catalani F., Cerruti M., Chadwick P., Chaty S., Chen A., Chernyakova M., Chiavassa A., Chudoba J., Coimbra-Araujo C., Conforti V., Contreras J.L., Costa A., Costantini H., Cristofari P., Crocker R., D'Amico G., D'Ammando F., De Angelis A., De Caprio V., de Gouveia Dal Pino E.M., de Ona Wilhelmi E., de Souza V., Delgado C., della Volpe D., Depaoli D., Di Girolamo T., Di Pierro F., Di Tria R., Di Venere L., Diebold S., Djuvsland J.I., Donini A., Doro M., Dos Anjos R.D.C., Dwarkadas V.V., Einecke S., Elsässer D., Emery G., Evoli C., Falceta-Goncalves D., Fedorova E., Fegan S.

Astroparticle Physics Vol. 150 2023.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Astroparticle Physics

The local Cosmic Ray (CR) energy spectrum exhibits a spectral softening at energies around 3 PeV. Sources which are capable of accelerating hadrons to such energies are called hadronic PeVatrons. However, hadronic PeVatrons have not yet been firmly identified within the Galaxy. Several source classes, including Galactic Supernova Remnants (SNRs), have been proposed as PeVatron candidates. The potential to search for hadronic PeVatrons with the Cherenkov Telescope Array (CTA) is assessed. The focus is on the usage of very high energy γ-ray spectral signatures for the identification of PeVatrons. Assuming that SNRs can accelerate CRs up to knee energies, the number of Galactic SNRs which can be identified as PeVatrons with CTA is estimated within a model for the evolution of SNRs. Additionally, the potential of a follow-up observation strategy under moonlight conditions for PeVatron searches is investigated. Statistical methods for the identification of PeVatrons are introduced, and realistic Monte-Carlo simulations of the response of the CTA observatory to the emission spectra from hadronic PeVatrons are performed. Based on simulations of a simplified model for the evolution for SNRs, the detection of a γ-ray signal from in average 9 Galactic PeVatron SNRs is expected to result from the scan of the Galactic plane with CTA after 10 h of exposure. CTA is also shown to have excellent potential to confirm these sources as PeVatrons in deep observations with O(100) hours of exposure per source.

DOI： 10.1016/j.astropartphys.2023.102850

Scopus

Multimessenger Characterization of Markarian 501 during Historically Low X-Ray and γ-Ray Activity Reviewed International coauthorship

Abe, H. et al.

Vol. 266 ( 2 ) page： 37 2023.6

AstroPix: CMOS pixels in space Reviewed

Steinhebel A.L., Caputo R., Fleischhack H., Striebig N., Jadhav M., Suda Y., Luz R., Violette D., Kierans C., Tajima H., Fukazawa Y., Leys R., Perić I., Metcalfe J., Negro M., Perkins J.S.

Proceedings of Science Vol. 420 2023.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Proceedings of Science

Space-based gamma-ray telescopes such as the Fermi Large Area Telescope have used single sided silicon strip detectors to measure the position of charged particles produced by incident gamma rays with high resolution. At energies in the Compton regime and below, two dimensional position information within a single detector is required. Double sided silicon strip detectors are one option; however, this technology is difficult to fabricate and large arrays are susceptible to noise. This work outlines the development and implementation of monolithic CMOS active pixel silicon sensors, AstroPix, for use in future gamma-ray telescopes. Based upon detectors designed using the HVCMOS process at the Karlsruhe Institute of Technology, AstroPix has the potential to maintain the high energy and angular resolution required of a medium-energy gamma-ray telescope while reducing noise with the dual detection-and-readout capabilities of a CMOS chip. The status of AstroPix development and testing as well as outlook for application in future telescopes is presented.

Scopus

Multiwavelength study of the galactic PeVatron candidate LHAASO J2108+5157 Reviewed International coauthorship

Abe, S. et al.

Astronomy & Astrophysics Vol. 673 page： A75 2023.5

The Fermi-LAT Lightcurve Repository Reviewed International coauthorship

Abdollahi, S. et al.

The Astrophysical Journal Supplement Series Vol. 265 ( 2 ) page： 31 2023.4

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Papers - TAJIMA, Hiroyasu