Fitting Pulsar Wind Tori

By C. Ng, R. Romani. 2003

185 citations recorded by the source corpus.

Chandra X-Ray Observatory imaging has shown that equatorial tori, often with polar jets, are very common in young pulsar wind nebulae (PWNe). These structures are interesting both for what they reveal about the relativistic wind itself and for the (nearly) model-independent measurement of the neutron star spin orientation they provide. The latter is a particularly valuable probe of pulsar emission models and neutron star physics. We describe here a procedure for fitting simple three-dimensional torus models to the X-ray data, which provides robust estimates of the geometric parameters. An application to six PWN tori gives orientations, PWN shock scales, and postshock wind speeds, along with statistical errors. We illustrate the use of these data by commenting on the implications for kick physics and high-energy beaming models.

Subfields: Astronomy and Astrophysics, Geophysics

View Paper: https://www.semanticscholar.org/paper/23f9fed1a92be8a25416d7917a72b8b38c5035e0

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In Astronomy and Astrophysics

1. Simon Johnston
2. G. Hobbs
3. Michael Kramer
4. J. Arons
5. Andrew G. Lyne
6. J. Weisberg
7. J. Hester
8. B. Gaensler

In Geophysics

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2. Michael Kramer
3. J. Arons
4. J. Hester

Citations in the corpus

• The evolution and structure of pulsar wind nebulae (2006, background): “In addition, for pulsars whose proper motion is known, constraints on mechanisms for producing this population’s high-velocity birth kicks can be derived based on the degree of alignment between the pulsar spin axis and the direction of motion (Lai, Chernoff & Cordes 2001; Ng & Romani 2004).”
• Pulsar Wind Nebulae as Cosmic Pevatrons: A Current Sheet’s Tale (2012, background): “…special about the angular sector of the nebula around the plane of the rotational equator of the underlying star—the X-ray torus and the Chandra ring in the Crab and the partial X-ray tori in other PWNe (Ng and Romani 2004; Kargeltsev and Pavlov 2008) indicate the significance of this region.”
• Three-dimensional magnetohydrodynamic simulations of the Crab nebula (2013, unknown): “These measured EVPAs are very close to the PA of the Crab torus symmetry axis, χ ' 126o (Ng & Romani 2004) and presumably reflect the orientation of the magnetic loops injected into the nebula by the pulsar wind.”
• The Crab Nebula: An Astrophysical Chimera (2008, background): “The most careful fitting to the structure of the Crab torus is that of Ng & Romani (2004), who match the Crab torus with PA = 126◦.31 ± 0.03, an axis tilted into the plane of the sky by PA = 26.97◦ ±0.03, and a flow velocity through the torus of 0.550c ± .001c .”
• Evidence for alignment of the rotation and velocity vectors in pulsars. II. Further data and emission heights (2005, methodology): “Although the claimed association has been disputed (Nicastro, Johnston & Koribalski 1996; Frail & Scharringhausen 1997), Ng & Romani (2004) derived a position angle vector of 175◦ for the rotation axis based on observations of an X-ray torus around the pulsar. c© 2005 RAS, MNRAS 000, 1–17 Table 1…”
• Polarization of the Crab Pulsar and Nebula as Observed by the INTEGRAL/IBIS Telescope (2008, background): “The off-pulse-and-bridge emission is polarized at an angle of 122.0◦± 7.7◦ which is fully consistent with the north-to-east angle ψ = 124◦ ± 0.1◦ of the pulsar rotation axis projected on the skyplane (Ng & Romani 2004).”