Detection of polarized gamma-ray emission from the Crab nebula with the Hitomi Soft Gamma-ray Detector

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https://academic.oup.com/pasj/article/70/6/113/5168156

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https://doi.org/10.1093/pasj/psy118
 http://hdl.handle.net/11603/29423

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UMBC Center for Space Sciences and Technology (CSST) / Center for Research and Exploration in Space Sciences & Technology II (CRSST II)
UMBC Faculty Collection
UMBC Physics Department

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Author/Creator ORCID

https://orcid.org/0000-0001-7515-2779
 https://orcid.org/0000-0002-3331-7595
 https://orcid.org/0000-0002-8286-8094
 https://orcid.org/0000-0002-4656-6881
 https://orcid.org/0000-0002-6562-8654

Date

2018-11-09

Type of Work

journal articles
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Citation of Original Publication

Hitomi Collaboration and others, Detection of polarized gamma-ray emission from the Crab nebula with the Hitomi Soft Gamma-ray Detector, Publications of the Astronomical Society of Japan, Volume 70, Issue 6, December 2018, 113, https://doi.org/10.1093/pasj/psy118

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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Abstract

We present the results from the Hitomi Soft Gamma-ray Detector (SGD) observation of the Crab nebula. The main part of SGD is a Compton camera, which in addition to being a spectrometer, is capable of measuring polarization of gamma-ray photons. The Crab nebula is one of the brightest X-ray/gamma-ray sources on the sky, and the only source from which polarized X-ray photons have been detected. SGD observed the Crab nebula during the initial test observation phase of Hitomi. We performed data analysis of the SGD observation, SGD background estimation, and SGD Monte Carlo simulations, and successfully detected polarized gamma-ray emission from the Crab nebula with only about 5 ks exposure time. The obtained polarization fraction of the phase-integrated Crab emission (sum of pulsar and nebula emissions) is (22.1% ± 10.6%), and the polarization angle is 110°.7 +13°.2 /−13°.0 in the energy range of 60–160 keV (the errors correspond to the 1 σ deviation). The confidence level of the polarization detection was 99.3%. The polarization angle measured by SGD is about one sigma deviation with the projected spin axis of the pulsar, 124°.0  ± 0°.1 ⁠.