Polarimetry in the hard X-ray domain with INTEGRAL SPI

Abstract

We present recent improvements in polarization analysis with the INTEGRAL SPI data. The SPI detector plane consists of 19 independent Ge crystals and can operate as a polarimeter. The anisotropy characteristics of Compton diffusions can provide information on the polarization parameters of the incident flux. By including the physics of the polarized Compton process in the instrument simulation, we are able to determine the instrument response for a linearly polarized emission at any position angle. We compare the observed data with the simulation sets by a minimum χ^2 technique to determine the polarization parameters of the source (angle and fraction). We have tested our analysis procedure with Crab nebula observations and find a position angle similar to those previously reported in the literature, with a comfortable significance. Since the instrument response depends on the incident angle, each exposure in the SPI data requires its own set of simulations, calculated for 18 polarization angles (from 0° to 170° in steps of 10°) and unpolarized emission. The analysis of a large amount of observations for a given source, required to obtain statistically significant results, represents a large amount of computing time, but it is the only way to access this complementary information in the hard X-ray regime. Indeed, major scientific advances are expected from such studies since the observational results will help to discriminate between the different models proposed for the high energy emission of compact objects like X-ray binaries and active galactic nuclei or gamma-ray bursts.

8 pages, 8 figures, accepted in ApJ

References in corpus (2)

• Polarization of the Crab pulsar and nebula as observed by the Integral/IBIS telescope
• Polarisation studies of the prompt gamma-ray emission from GRB 041219a using the Spectrometer aboard INTEGRAL

Cited by in corpus (21)

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• Observation of polarised hard X-ray emission from the Crab by the PoGOLite Pathfinder
• Calibration and performance studies of the balloon-borne hard X-ray polarimeter PoGO+
• The design and flight performance of the PoGOLite Pathfinder balloon-borne hard X-ray polarimeter
• In-Orbit Instrument Performance Study and Calibration for POLAR Polarization Measurements
• 2003-2018 Monitoring of the Crab Nebula Polarization in hard X-rays with INTEGRAL SPI
• Pitfalls of statistics-limited X-ray polarization analysis
• Hard X-ray polarimetry with Caliste, a high performance CdTe based imaging spectrometer
• Preflight performance studies of the PoGOLite hard X-ray polarimeter
• Gamma Ray polarimetry; a new window for the non-thermal Universe
• Vacuum non-linear electrodynamic polarization effects in hard emission of pulsars and magnetars
• Gamma-Ray Polarimetry of the Crab Pulsar Observed by POLAR
• Gamma-Ray Polarimetry
• Compton polarimetry revisited
• Telescope Concepts in Gamma-Ray Astronomy
• Crab Pulsar: IXPE Observations Reveal Unified Polarization Properties Across Optical and Soft X-Ray Bands
• Hard X-ray Polarimetry -- An overview of the method, science drivers and recent findings
• Performance of the X-Calibur Hard X-Ray Polarimetry Mission during its 2018/19 Long-Duration Balloon Flight