High-Altitude Emission from Pulsar Slot Gaps: The Crab Pulsar

By A. Harding, J. Stern, J. Dyks, M. Frąckowiak. 2008

153 citations recorded by the source corpus.

We present results of a 3D model of optical-to-γ-ray emission from the slot gap accelerator of a rotation-powered pulsar. Primary electrons accelerating to high altitudes in the unscreened electric field of the slot gap reach radiation reaction limited Lorentz factors of ~2 × 107, while electron-positron pairs from lower altitude cascades flow along field lines interior to the slot gap. The curvature, synchrotron, and inverse Compton radiation of both primary electrons and pairs produce a broad spectrum of emission from infrared to GeV energies. Both primaries and pairs undergo cyclotron resonant absorption of radio photons, allowing them to maintain significant pitch angles. Synchrotron radiation from pairs with a power-law energy spectrum from γ = 102 to 105, dominate the spectrum up to ~10 MeV. Synchrotron and curvature radiation of primaries dominates from 10 MeV up to a few GeV. We examine the energy-dependent pulse profiles and phase-resolved spectra for parameters of the Crab pulsar as a function of magnetic inclination α and viewing angle ζ, comparing to broadband data. In most cases, the pulse profiles are dominated by caustics on trailing field lines. We also explore the relation of the high-energy and the radio profiles, as well as the possibility of caustic formation in the radio cone emission. We find that the Crab pulsar profiles and spectrum can be reasonably well reproduced by a model with α = 45° and ζ ∼ 100° or 80°. This model predicts that the slot gap emission below 200 MeV will exhibit correlations in time and phase with the radio emission.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/ddb43d41df439865dd9b6dbed444ef8c5dc02b40

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In Astronomy and Astrophysics

1. A. Spitkovsky
2. J. Arons
3. L. Sironi
4. Michael Kramer
5. Bing Zhang
6. Xue-Ning Bai
7. E. Orlando
8. A. Strong

In Nuclear and High Energy Physics

1. A. Spitkovsky
2. J. Arons
3. L. Sironi
4. A. Strong
5. E. Orlando
6. I. Grenier
7. Xue-Ning Bai
8. Igor V. Moskalenko

Citations in the corpus

• MODELING OF GAMMA-RAY PULSAR LIGHT CURVES USING THE FORCE-FREE MAGNETIC FIELD (2009, background): “Such pitch angle is expected from both conventional SG and OG models, e.g., acquired during the pair creation process (Tang et al. 2008), or via the cyclotron resonant absorption (Harding et al. 2008).”
• THE FIRST FERMI LARGE AREA TELESCOPE CATALOG OF GAMMA-RAY PULSARS (2009, background): “…steepen the spectrum for the more energetic pulsars, either by steepening the spectrum of the curvature radiation-generating primary electrons (Romani 1996) or by inclusion of an additional soft spectral component associated with robust pair formation (Takata & Chang 2007; Harding et al. 2008).”
• TOWARD A REALISTIC PULSAR MAGNETOSPHERE (2011, background): “Slot gap models (Muslimov & Harding 2004; Harding et al. 2008), with acceleration and emission in a narrow layer along the last open field line from the neutron star surface to near the LC, and outer gap models (Romani & Yadigaroglu 1995; Romani 1996; Takata et al. 2007) produce light curves and…”
• THE MAXIMUM ENERGY OF ACCELERATED PARTICLES IN RELATIVISTIC COLLISIONLESS SHOCKS (2013, background): “…the rotational and magnetic axis of 18 the Crab pulsar, inferred from fitting the spectrum and pulse profile of the high-energy pulsar emission (Harding et al. 2008), and if λζ is the latitude angle measured from the midplane, the residual wind magnetization near the equatorial plane will…”
• Three-dimensional magnetohydrodynamic simulations of the Crab nebula (2013, background): “However, c© 0000 RAS, MNRAS 000, 000–000 in the case of the Crab pulsar, Harding et al. (2008) found α ' 45◦ by fitting the high energy spectrum and the pulse profile.”
• Galactic electrons and positrons at the Earth: new estimate of the primary and secondary fluxes (2010, background): “…of the specific pulsar model, such as for instance the polar gap (Ruderman & Sutherland 1975), the outer gap (Cheng et al. 1976, 1986), or the slot gap (Harding et al. 2008) models, we may summarize the physics relevant to the production of cosmic-ray electrons and positrons as follows.”