89 research outputs found
First observation of MeV gamma-ray universe with bijective imaging spectroscopy using the Electron-Tracking Compton Telescope aboard SMILE-2+
MeV gamma-rays provide a unique window for the direct measurement of line
emissions from radioisotopes, but observations have made little significant
progress after COMPTEL/{\it CGRO}. To observe celestial objects in this band,
we are developing an electron-tracking Compton camera (ETCC), which 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+ installed with an ETCC having a gaseous electron tracker with
a volume of 303030 cm. Gamma-rays from the Crab nebula were
detected with a significance of 4.0 in the energy range 0.15--2.1 MeV
with a live time of 5.1 h, as expected before launching. 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 pre-launch 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
Sox2 induces tumorigenesis and angiogenesis of early stage esophagealsquamous cell carcinoma through secretion of Suprabasin.
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