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Jackson, Miranda
Publications (2 of 2) Show all publications
Chauvin, M., Florén, H.-G. -., Jackson, M., Kamae, T., Kataoka, J., Kiss, M., . . . Pearce, M. (2019). PoGO + polarimetric constraint on the synchrotron jet emission of Cygnus X-1. Monthly Notices of the Royal Astronomical Society: Letters, 483(1), L138-L143
Open this publication in new window or tab >>PoGO + polarimetric constraint on the synchrotron jet emission of Cygnus X-1
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2019 (English)In: Monthly Notices of the Royal Astronomical Society: Letters, ISSN 1745-3925, Vol. 483, no 1, p. L138-L143Article in journal (Refereed) Published
Abstract [en]

We report a polarimetric constraint on the hard X-ray synchrotron jet emission from the Cygnus X-1 black hole binary system. The observational data were obtained using the PoGO+ hard X-ray polarimeter in 2016 July, when Cygnus X-1 was in the hard state. We have previously reported that emission from an extended corona with a low polarization fraction is dominating, and that the polarization angle is perpendicular to the disc surface. In the soft gamma-ray regime, a highly polarized synchrotron jet is reported with INTEGRAL observations. To constrain the polarization fraction and flux of such a jet component in the hard X-ray regime, we now extend analyses through vector calculations in the Stokes QU plane, where the dominant corona emission and the jet component are considered simultaneously. The presence of another emission component with different polarization angle could partly cancel out the net polarization. The 90 per cent upper limit of the polarization fraction for the additional synchrotron jet component is estimated as <10 per cent, <5 per cent, and <5 per cent for polarization angle perpendicular to the disc surface, parallel to the surface, and aligned with the emission reported by INTEGRAL data, respectively. From the 20-180 keV total flux of 2.6 × 10 -8 erg s -1 cm -2, the upper limit of the polarized flux is estimated as < 3 × 10 -9 erg s -1 cm -2.

Place, publisher, year, edition, pages
Oxford University Press, 2019
Keywords
accretion, accretion discs, techniques: polarimetric, X-rays: binaries, X-rays: individual (Cygnus X-1)
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-248187 (URN)10.1093/mnrasl/sly233 (DOI)000482178200028 ()2-s2.0-85062384117 (Scopus ID)
Note

QC 20190412

Available from: 2019-04-12 Created: 2019-04-12 Last updated: 2019-09-05Bibliographically approved
Chauvin, M., Floren, H.-G. -., Friis, M., Jackson, M., Kamae, T., Kataoka, J., . . . Pearce, M. (2018). The PoGO plus view on Crab off-pulse hard X-ray polarization. Monthly notices of the Royal Astronomical Society, 477(1), L45-L49
Open this publication in new window or tab >>The PoGO plus view on Crab off-pulse hard X-ray polarization
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2018 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 477, no 1, p. L45-L49Article in journal (Refereed) Published
Abstract [en]

The linear polarization fraction (PF) and angle of the hard X-ray emission from the Crab provide unique insight into high-energy radiation mechanisms, complementing the usual imaging, timing, and spectroscopic approaches. Results have recently been presented by two missions operating in partially overlapping energy bands, PoGO+ (18-160 keV) and AstroSat CZTI (100-380 keV). We previously reported PoGO+ results on the polarization parameters integrated across the light curve and for the entire nebula-dominated off-pulse region. We now introduce finer phase binning, in light of the AstroSat CZTI claim that the PF varies across the off-pulse region. Since both missions are operating in a regime where errors on the reconstructed polarization parameters are non-Gaussian, we adopt a Bayesian approach to compare results from each mission. We find no statistically significant variation in off-pulse polarization parameters, neither when considering the mission data separately nor when they are combined. This supports expectations from standard high-energy emission models.

Place, publisher, year, edition, pages
Oxford University Press, 2018
Keywords
instrumentation: polarimeters, methods: statistical
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-241233 (URN)10.1093/mnrasl/sly027 (DOI)000454420400010 ()
Note

QC 20190117

Available from: 2019-01-17 Created: 2019-01-17 Last updated: 2019-01-18Bibliographically approved
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