Linear Polarization in Gamma-Ray Bursts: The Case for an Ordered Magnetic Field

Granot, Jonathan; Königl, Arieh

doi:10.1086/378733

Cited by 167 publications

(302 citation statements)

References 23 publications

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“…Similar polarization fractions were observed at every point in the light curve with signal-to-noise in flux greater than one ( Figure 6). This is consistent with emission from a small-volume synchrotron source, such as a GRB or other small jet produced in an extremely homogeneous magnetic field (Granot & Königl 2003). It is not clear, however, how this very high polarization fraction corresponds to the non-detection in the 95 GHz data, which suggests an optically thick source.…”

Section: Candidate Objectsupporting

confidence: 75%

“…Although it is not clear how to reconcile the 95 GHz non-detection with the 150 GHz polarization data, a plausible explanation for the 150 GHz data alone would be a nearly on-axis GRB afterglow. This would be consistent with the timescale of emission, the high degree of linear polarization, and the 90°polarization rotation coincident with the beginning of the candidate's decay (Granot & Königl 2003). The gamma-ray component of such a GRB could have been missed due to the limited observing efficiency of satellites, a small misalignment of the jet, or obscuration of the prompt high-energy component.…”

Section: Candidate Objectmentioning

confidence: 52%

“…After the shift, the mean angle rotated to 36°±14°. Such a ∼90°polarization angle rotation at this point in the lightcurve would be typical of a GRB afterglow jet break (Granot & Königl 2003;Wiersema et al 2014), in which the beaming angle expands beyond the geometric opening angle of the jet and the viewable polarization field becomes truncated.…”

Section: Candidate Objectmentioning

confidence: 87%

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MILLIMETER TRANSIENT POINT SOURCES IN THE SPTpol 100 SQUARE DEGREE SURVEY

Whitehorn

Natoli

Ade

et al. 2016

ApJ

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The millimeter transient sky is largely unexplored, with measurements limited to follow-up of objects detected at other wavelengths. High-angular-resolution telescopes, designed for measurement of the cosmic microwave background (CMB), offer the possibility to discover new, unknown transient sources in this band-particularly the afterglows of unobserved gamma-ray bursts (GRBs). Here, we use the 10 m millimeter-wave South Pole Telescope, designed for the primary purpose of observing the CMB at arcminute and larger angular scales, to conduct a search for such objects. During the 2012-2013 season, the telescope was used to continuously observe a 100 deg 2 patch of sky centered at R.A. 23 h 30 m and decl. −55°using the polarization-sensitive SPTpol camera in two bands centered at 95 and 150 GHz. These 6000 hr of observations provided continuous monitoring for day-to month-scale millimeter-wave transient sources at the 10 mJy level. One candidate object was observed with properties broadly consistent with a GRB afterglow, but at a statistical significance too low (p = 0.01) to confirm detection.

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Section: Candidate Objectsupporting

confidence: 75%

Section: Candidate Objectmentioning

confidence: 52%

Section: Candidate Objectmentioning

confidence: 87%

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MILLIMETER TRANSIENT POINT SOURCES IN THE SPTpol 100 SQUARE DEGREE SURVEY

Whitehorn

Natoli

Ade

et al. 2016

ApJ

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“…Typical values of p = 2−3 correspond to a polarisation of 70-75%. An ordered magnetic field of this type would not be produced in shocks but could be advected from the central engine (Granot & Königl 2003;Granot 2003;Lyutikov et al 2003).…”

Section: Discussionmentioning

confidence: 99%

Polarisation studies of the prompt gamma-ray emission from GRB 041219a using the spectrometer aboard INTEGRAL

McGlynn

Clark

Dean

et al. 2007

A&A

154

138

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Context. Linear polarisation in gamma-ray burst prompt emission is an important diagnostic with the potential to significantly constrain models. The spectrometer aboard INTEGRAL, SPI, has the capability to detect the signature of polarised emission from a bright γ-ray source. GRB 041219a is the most intense burst localised by INTEGRAL with a fluence of 5.7 ×10 −4 erg cm −2 over the energy range 20 keV-8 MeV and is an ideal candidate for such a study. Aims. Polarisation can be measured using multiple events scattered into adjacent detectors because the Compton scatter angle depends on the polarisation of the incoming photon. A search for linear polarisation in the most intense pulse of duration 66 seconds and in the brightest 12 seconds of GRB 041219a was performed in the 100-350 keV, 100-500 keV and 100 keV-1 MeV energy ranges. It was possible to divide the events into six directions in the energy ranges of 100-350 keV and 100-500 keV using the kinematics of the Compton scatter interactions. Methods. The multiple event data from the spectrometer was analysed and compared with the predicted instrument response obtained from Monte-Carlo simulations using the GEANT 4 INTEGRAL mass model. The χ 2 distribution between the real and simulated data as a function of the percentage polarisation and polarisation angle was calculated for all three energy ranges. The degree and angle of polarisation were obtained from the best-fit value of χ 2 . Results. A weak signal consistent with polarisation was found throughout the analyses. The degree of linear polarisation in the brightest pulse of duration 66 s was found to be 63 +31 −30 % at an angle of 70 +14 −11 degrees in the 100-350 keV energy range. The degree of polarisation was also constrained in the brightest 12 s of the GRB and a polarisation fraction of 96 +39 −40 % at an angle of 60 +12 −14 degrees was determined over the same energy range. However, despite extensive analysis and simulations, a systematic effect that could mimic the weak polarisation signal could not be definitively excluded. Conclusions. Our results over several energy ranges and time intervals are consistent with a polarisation signal of about 60% but at a low level of significance (∼2σ). The polarisation results are compared with predictions from the synchrotron and Compton drag processes. The spectrum of this GRB can also be well fit by a combined black body and power law model which could arise from a combination of the Compton and synchrotron processes, with different degrees of polarisation. We therefore conclude that the procedure described here demonstrates the effectiveness of using SPI as a polarimeter, and is a viable method of measuring polarisation levels in intense gamma-ray bursts.

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“…This effect cannot be observed in terrestrial laboratories and would provide a test of QED in extreme conditions. X-ray polarization may reveal the inner structure of the jets from gamma-ray bursts (GRBs) [22][23] [24] [25]. For high polarization fractions, the observations could establish the magnetically dominated character of the jet flow, and would constrain the process of jet formation as well as the central engine.…”

Section: Hard X-ray Polarimetry With Exist -Science Topicsmentioning

confidence: 99%

Polarimetry with EXIST

Krawczynski¹,

Garson²,

Martin³

et al. 2009

Proceedings of Polarimetry Days in Rome: Crab Status, Theory and Prospects — PoS(CRAB2008)

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EXIST (Hard X-ray Imaging Survey Mission) is a proposed space borne observatory that combines a wide-field-of-view X-ray telescope (5-600 keV) with a pointed optical/infrared telescope, and possibly with a soft X-ray telescope contributed by Italian collaborators. The primary science drivers of EXIST are the study of the high-redshift Universe and the epoch of re-ionization through the detection and follow-up observations of high-redshift Gamma-Ray Bursts (GRBs) at z ~ 10, the study of supermassive black holes in galaxies (including heavily obscured and dormant black holes), and the study of stellar mass and intermediate mass black hole populations in the Milky Way galaxy and in the Local Group. In this contribution, we discuss the polarimetric capabilities of the EXIST hard X-ray telescope. Based on a pointed 5-day observation (or based on 4 months all-sky survey observations), EXIST can detect the hard X-ray polarization of 100 mCrab sources for polarization degrees down to 6%. The wide field of view of EXIST will make it possible to measure the polarization of transient events like GRBs and flaring galactic and extragalactic sources. We discuss the scientific potential of the hard Xray polarimetric measurements. The EXIST observations would allow us to (i) obtain qualitatively new constraints on the locale of particle acceleration in the vicinity of compact objects, (ii) gain key-insights into the structure of jets from GRBs and Active Galactic Nuclei, (iii) test high-order QED predictions in the extreme magnetic fields of neutron stars, and (iv) to search for quantum gravity signatures (the helicity-dependence of the speed of light) with unprecedented sensitivity. Rome: Crab status, theory and prospects, Polarimetry days in

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Linear Polarization in Gamma-Ray Bursts: The Case for an Ordered Magnetic Field

Cited by 167 publications

References 23 publications

MILLIMETER TRANSIENT POINT SOURCES IN THE SPTpol 100 SQUARE DEGREE SURVEY

MILLIMETER TRANSIENT POINT SOURCES IN THE SPTpol 100 SQUARE DEGREE SURVEY

Polarisation studies of the prompt gamma-ray emission from GRB 041219a using the spectrometer aboard INTEGRAL

Polarimetry with EXIST

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