Observation of polarised hard X-ray emission from the Crab by the PoGOLite Pathfinder

Abstract

We have measured the linear polarisation of hard X-ray emission from the Crab in a previously unexplored energy interval, 20-120 keV. The introduction of two new observational parameters, the polarisation fraction and angle stands to disentangle geometrical and physical effects, thereby providing information on the pulsar wind geometry and magnetic field environment. Measurements are conducted using the PoGOLite Pathfinder - a balloon-borne polarimeter. Polarisation is determined by measuring the azimuthal Compton scattering angle of incident X-rays in an array of plastic scintillators housed in an anticoincidence well. The polarimetric response has been characterised prior to flight using both polarised and unpolarised calibration sources. We address possible systematic effects through observations of a background field. The measured polarisation fraction for the integrated Crab light-curve is ($18.4_{-10.6}^{+9.8}$)%, corresponding to an upper limit (99% credibility) of 42.4%, for a polarisation angle of ($149.2\pm 16.0{)}^{\circ }$.

arXiv comment6 pages, 5 figures. Accepted for publication in MNRAS Letters (In this revision the polarisation angle is correctly stated as 149.2$\pm$16.0 degrees and not 142.2$\pm$16.0 degrees (typo corrected in abstract and on page 4)

References in corpus (20)

• Hard X-ray Detector (HXD) on Board Suzaku
• The Swift/BAT Hard X-ray Transient Monitor
• In-Orbit Performance of the Hard X-ray Detector on board Suzaku
• Gamma Ray Pulsars: Emission from Extended Polar Cap Cascades
• Fermi Large Area Telescope Observations of the Crab Pulsar and Nebula
• Polarization of prompt GRB emission: evidence for electromagnetically-dominated outflow
• Fitting Pulsar Wind Tori
• The Crab pulsar in the 0.75-30 MeV range as seen by CGRO COMPTEL
• Analyzing the Data from X-ray Polarimeters with Stokes Parameters
• Particle Acceleration Zones Above Pulsar Polar Caps: Electron and Positron Pair Formation Fronts
• Polarization of the Crab pulsar and nebula as observed by the Integral/IBIS telescope
• On understanding the figures of merit for detection and measurement of x-ray polarization
• XIPE: the X-ray Imaging Polarimetry Explorer
• Optical polarisation of the Crab pulsar: precision measurements and comparison to the radio emission
• Scientific Prospects for Hard X-ray Polarimetry
• Bayesian analysis of polarization measurements
• Polarimetry in the hard X-ray domain with INTEGRAL SPI
• Point and Interval Estimation on the Degree and the Angle of Polarization. A Bayesian approach
• The design and flight performance of the PoGOLite Pathfinder balloon-borne hard X-ray polarimeter
• Preflight performance studies of the PoGOLite hard X-ray polarimeter

Cited by in corpus (15)

• Theory of pulsar magnetosphere and wind
• Detection of polarized gamma-ray emission from the Crab nebula with Hitomi Soft Gamma-ray Detector
• Predicting the X-ray polarization of type-2 Seyfert galaxies
• The PoGO+ Balloon-Borne Hard X-ray Polarimetry Mission
• Calibration and performance studies of the balloon-borne hard X-ray polarimeter PoGO+
• Probing magnetar emission mechanisms with spectropolarimetry
• Optimising a balloon-borne polarimeter in the hard X-ray domain: from the PoGOLite Pathfinder to PoGO+
• Turbulent model of Crab nebula radiation
• Pitfalls of statistics-limited X-ray polarization analysis
• Vacuum non-linear electrodynamic polarization effects in hard emission of pulsars and magnetars
• Gamma Ray polarimetry; a new window for the non-thermal Universe
• XL-Calibur measurements of polarised hard X-ray emission from the Crab
• Shedding new light on the Crab with polarized X-rays
• Data Analysis for a Balloon Borne Compton Polarimeter
• Future X-ray Polarimetry of Relativistic Accelerators: PWNe and SNRs