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Jackson, Miranda
Publikationer (2 of 2) Visa alla publikationer
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
Öppna denna publikation i ny flik eller fönster >>PoGO + polarimetric constraint on the synchrotron jet emission of Cygnus X-1
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2019 (Engelska)Ingår i: Monthly Notices of the Royal Astronomical Society: Letters, ISSN 1745-3925, Vol. 483, nr 1, s. L138-L143Artikel i tidskrift (Refereegranskat) 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.

Ort, förlag, år, upplaga, sidor
Oxford University Press, 2019
Nyckelord
accretion, accretion discs, techniques: polarimetric, X-rays: binaries, X-rays: individual (Cygnus X-1)
Nationell ämneskategori
Fysik
Identifikatorer
urn:nbn:se:kth:diva-248187 (URN)10.1093/mnrasl/sly233 (DOI)000482178200028 ()2-s2.0-85062384117 (Scopus ID)
Anmärkning

QC 20190412

Tillgänglig från: 2019-04-12 Skapad: 2019-04-12 Senast uppdaterad: 2019-09-05Bibliografiskt granskad
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
Öppna denna publikation i ny flik eller fönster >>The PoGO plus view on Crab off-pulse hard X-ray polarization
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2018 (Engelska)Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 477, nr 1, s. L45-L49Artikel i tidskrift (Refereegranskat) 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.

Ort, förlag, år, upplaga, sidor
Oxford University Press, 2018
Nyckelord
instrumentation: polarimeters, methods: statistical
Nationell ämneskategori
Astronomi, astrofysik och kosmologi
Identifikatorer
urn:nbn:se:kth:diva-241233 (URN)10.1093/mnrasl/sly027 (DOI)000454420400010 ()
Anmärkning

QC 20190117

Tillgänglig från: 2019-01-17 Skapad: 2019-01-17 Senast uppdaterad: 2019-01-18Bibliografiskt granskad
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