First Observation of the MeV Gamma-Ray Universe with Bijective Imaging Spectroscopy Using the Electron-tracking Compton Telescope on Board SMILE-2+

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dc.contributor.authorTakada, Atsushi
dc.contributor.authorTakemura, Taito
dc.contributor.authorYoshikawa, Kei
dc.contributor.authorMizumura, Yoshitaka
dc.contributor.authorIkeda, Tomonori
dc.contributor.authorNakamura, Yuta
dc.contributor.authorOnozaka, Ken
dc.contributor.authorAbe, Mitsuru
dc.contributor.authorHamaguchi, Kenji
dc.contributor.authorKubo, Hidetoshi
dc.contributor.authorKurosawa, Shunsuke
dc.contributor.authorMiuchi, Kentaro
dc.contributor.authorSaito, Kaname
dc.contributor.authorSawano, Tatsuya
dc.contributor.authorTanimori, Toru
dc.date.accessioned2022-06-22T00:27:28Z
dc.date.available2022-06-22T00:27:28Z
dc.date.issued2022-04-28
dc.description.abstractMeV gamma-rays provide a unique window for the direct measurement of line emissions from radioisotopes, but observations have made little significant progress since COMPTEL on board the Compton Gamma-ray Observatory (CGRO). To observe celestial objects in this band, we are developing an electron-tracking Compton camera (ETCC) that realizes both bijective imaging spectroscopy and efficient background reduction gleaned from the recoil-electron track information. The energy spectrum of the observation target can then be obtained by a simple ON–OFF method using a correctly defined point-spread function on the celestial sphere. The performance of celestial object observations was validated on the second balloon SMILE-2+ , on which an ETCC with a gaseous electron tracker was installed that had a volume of 30 × 30 × 30 cm3. Gamma-rays from the Crab Nebula were detected with a significance of 4.0σ in the energy range 0.15–2.1 MeV with a live time of 5.1 hr, as expected before launch. Additionally, the light curve clarified an enhancement of gamma-ray events generated in the Galactic center region, indicating that a significant proportion of the final remaining events are cosmic gamma-rays. Independently, the observed intensity and time variation were consistent with the prelaunch estimates except in the Galactic center region. The estimates were based on the total background of extragalactic diffuse, atmospheric, and instrumental gamma-rays after accounting for the variations in the atmospheric depth and rigidity during the level flight. The Crab results and light curve strongly support our understanding of both the detection sensitivity and the background in real observations. This work promises significant advances in MeV gamma-ray astronomy.en_US
dc.description.sponsorshipThe balloon-borne experiment was conducted by Scientific Ballooning (DAIKIKYU) Research and Operation Group, ISAS, JAXA. This study was supported by the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research (S) (21224005), (A) (20244026, 16H02185), Grant-in-Aid for Young Scientists(B) (15K17608), JSPS Grant-in-Aid for Challenging Exploratory Research (23654067, 25610042, 16K13785, 20K20428), a Grant-in-Aid from the Global COE program "Next Generation Physics, Spun from Universality and Emergence" from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, and Grant-in-Aid for JSPS Fellows (16J08498, 18J20107, 19J11323). Some of the electronics development was supported by KEK-DTP and Open-It Consortium. And we thank Enago (www.enago.jp) for the English language review.en_US
dc.description.urihttps://iopscience.iop.org/article/10.3847/1538-4357/ac6103en_US
dc.format.extent13 pagesen_US
dc.genrejournal articlesen_US
dc.identifierdoi:10.13016/m2nb6s-d9xe
dc.identifier.citationTakada, Atsushi et al. First Observation of the MeV Gamma-Ray Universe with Bijective Imaging Spectroscopy Using the Electron-tracking Compton Telescope on Board SMILE-2+. The Astrophysical Journal 930 (Apr. 28, 2022, no. 1. https://doi.org/10.3847/1538-4357/ac6103en_US
dc.identifier.urihttps://doi.org/10.3847/1538-4357/ac6103
dc.identifier.urihttp://hdl.handle.net/11603/25015
dc.language.isoen_USen_US
dc.publisherAASen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Center for Space Sciences and Technology
dc.relation.ispartofUMBC Faculty Collection
dc.rightsThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.en_US
dc.rightsAttribution 4.0 International (CC BY 4.0)*
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/*
dc.titleFirst Observation of the MeV Gamma-Ray Universe with Bijective Imaging Spectroscopy Using the Electron-tracking Compton Telescope on Board SMILE-2+en_US
dc.typeTexten_US
dcterms.creatorhttps://orcid.org/0000-0001-7515-2779en_US

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