The polarimetric performance of the Compton spectrometer and imager (COSI)

Yang, Chao Yao; Lowell, A.; Zoglauer, Andreas; Tomsick, John A.; Chiu, Jeng Jiann; Kierans, Carolyn; Sleator, Clio; Boggs, Steven E.; Chang, Hsiang-Kuang; Jean, P.; McBride, Steve; Mochizuki, Brent; Amman, M.; Ballmoos, P. von; Chang, Yeong‐Chan; Chu, Che-Yen; Liang, Hung-Hsiang; Lin, Chih-Hsun

doi:10.1117/12.2312556

Cited by 16 publications

(31 citation statements)

References 21 publications

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“…The Imaging X-ray Polarimetry Explorer (IXPE, [56]) to be launched in early 2021 will provide highly significant X-ray polarization measurements of a large number of astrophysical objects and one can expect that a similar analysis with those data will significantly improve on the results presented here. Future Compton gamma-ray telescopes, such as the proposed All-sky Medium-Energy Gamma-ray Observatory (AMEGO [57]) or the Compton Spectrometer and Imager (COSI [58]) will be sensitive to gamma-ray polarization up to MeV energies. These future instruments will significantly enhance our capability to search for Lorentz invariance violation in the photon sector.…”

Section: Discussionmentioning

confidence: 99%

Constraints on Lorentz Invariance Violation from Optical Polarimetry of Astrophysical Objects

Kislat

2018

Symmetry

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Theories of quantum gravity suggest that Lorentz invariance, the fundamental symmetry of the Theory of Relativity, may be broken at the Planck energy scale. While any deviation from conventional Physics must be minuscule in particular at attainable energies, this hypothesis motivates ever more sensitive tests of Lorentz symmetry. In the photon sector, astrophysical observations, in particular polarization measurements, are a very powerful tool because tiny deviations from Lorentz invariance will accumulate as photons propagate over cosmological distances. The Standard-Model Extension (SME) provides a theoretical framework in the form of an effective field theory that describes low-energy effects due to a more fundamental quantum gravity theory by adding additional terms to the Standard Model Lagrangian. These terms can be ordered by the mass dimension d of the corresponding operator and lead to a wavelength, polarization, and direction dependent phase velocity of light. Lorentz invariance violation leads to an energy-dependent change of the Stokes vector as photons propagate, which manifests itself as a rotation of the polarization angle in measurements of linear polarization. In this paper, we analyze optical polarization measurements from 63 Active Galactic Nuclei (AGN) and Gamma-ray Bursts (GRBs) to search for Lorentz violating signals. We use both spectropolarimetric measurements, which directly constrain the change of linear polarization angle, as well as broadband spectrally integrated measurements. In the latter, Lorentz invariance violation manifests itself by reducing the observed net polarization fraction. Any observation of non-vanishing linear polarization thus leads to constraints on the magnitude of Lorentz violating effects. We derive the first set limits on each of the 10 individual birefringent coefficients of the minimal SME with d = 4 , with 95% confidence limits on the order of 10−34 on the dimensionless coefficients.

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Section: Discussionmentioning

confidence: 99%

Constraints on Lorentz Invariance Violation from Optical Polarimetry of Astrophysical Objects

Kislat

2018

Symmetry

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“…Thus, by considering the energy resolution of planned flux-measuring observatories in the HE range [48,49], we expect a polarimeter energy resolution of 8 − 10 energy bins per decade. Therefore, observatories like COSI [47], e-ASTROGAM [48,49] and AMEGO [50] are expected to be able to detect the ALP-induced modifications to photon polarization.…”

Section: B High-energy Bandmentioning

confidence: 99%

“…in [39][40][41][42][43][44]. In addition, new attention on this topics has been recently paid because of some existing or proposed experiments that measure the polarization of cosmic photons in the X-ray band like IXPE [45] and Polstar [46] and in the high-energy (HE) band such as COSI [47], e-ASTROGAM [48,49] and AMEGO [50].…”

Section: Introductionmentioning

confidence: 99%

Photon-ALP oscillations inducing modifications to photon polarization

Galanti¹

2022

Preprint

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Axion-like particles (ALPs) are very light, neutral, spin zero bosons predicted by many theories which try to extend and complete the standard model of elementary particles. ALPs interact primarily with two photons and can generate photon-ALP oscillations in the presence of an external magnetic field. They are attracting increasing interest since photon-ALP oscillations produce deep consequences in astrophysics particularly in the very-high-energy (VHE) band, where they increase the transparency of the Universe to VHE photons by partially preventing absorption caused by the extragalactic background light. Furthermore, ALPs explain why photons coming from flat spectrum radio quasars (a particular class of active galactic nuclei, AGN) have been observed for energies above 20 GeV -which represents a first hint for the existence of an ALP. In addition, ALPs solve an anomalous redshift dependence of blazar (an AGN class) spectra -which represents a second hint for the existence of an ALP. In this paper, we study another effect of the photon-ALP interaction: the change of the polarization state of photons. In particular, we study the propagation of the photon-ALP beam starting where photons are produced -we consider photons generated in a galaxy cluster or in the jet of a blazar -crossing several magnetized media (blazar jet, host galaxy, galaxy cluster, extragalactic space, Milky Way) up to their arrival at the Earth, where photons can be detected. In the presence of photon-ALP interaction, we analyze the photon survival probability Pγ→γ and the corresponding photon degree of linear polarization ΠL for observed energies in the range (1 − 10 15 ) eV dividing it into three energy bands: (i) X-ray band (10 −3 keV − 10 2 keV), (ii) high-energy (HE) band (10 −1 MeV − 10 4 MeV), (iii) VHE band (10 −2 TeV − 10 3 TeV). We observe that photons, which are expected as unpolarized in the absence of ALPs, are made partially polarized by photon-ALP interaction, which generally modifies the initial photon degree of linear polarization ΠL,0 in a sizable and measurable way. Our findings about the X-ray and HE bands can be tested by current and planned observatories like IXPE, Polstar, COSI, e-ASTROGAM and AMEGO. A possible detection of a departure of the photon polarization from the standard expectations would represent an additional hint for the existence of an ALP. We also discover a peculiar feature in the VHE band, where photons at energies above ∼ 1 TeV are fully polarized because of photon-ALP interaction. A possible detection of this feature would represent a proof for the existence of an ALP, but, unfortunately, current technologies do not allow yet to detect photon polarization up to so high energies.

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“…An early summary of the results from the full flight (detection of the Crab, Cyg X-1, Cen A, the GRB, and the 511 keV emission from the Galactic Center) is reported in Kierans et al (2017). An analysis of the GRB 160530A data resulted in an upper limit on the polarization of <46% (Lowell et al, 2017a), and new techniques were developed for polarization studies (Lowell et al, 2017b) and also for calibrating the instrument (Lowell, 2017;Yang et al, 2018). The detection of the 511 keV emission and information about the line shape and spatial extent is reported in Kierans (2018).…”

Section: Technical Overviewmentioning

confidence: 99%