Theory

Astrophysics, Gravitational Physics, Gravitational Wave Phenomenology, Gravitational Wave Phenomenology

Neutron stars are laboratories for physics under extreme conditions, and may be detectable sources of gravitational waves. My particular interests center around and branch out from the r-modes, fluid oscillations which feed on gravitational waves while emitting them. The signals may carry information on gravitational and nuclear physics that can't be had in other ways.

What does an r-mode look like? You're watching one on the top right of this page. Imagine the dots as buoys floating on the surface and moved around by the r-mode, in addition to the counterclockwise rotation of the star. The lines indicate where chains of buoys would float. The red buoys would have a fixed latitude on an unperturbed star, so you can see that the star is rotating faster than the r-mode pattern speed.

(The fluid motion has no radial component, and is the same inside the star although smaller by a factor of the square of the distance from the center.)

Moving to a frame of reference corotating with the star, we see the picture at right. First you see that the fluid elements (red buoys) move in ellipses around their unperturbed locations. Second you see that the pattern speed is not keeping up with the rotation of the star, so in this frame the mode looks like it's moving backwards. This is why the mode is unstable to gravitational radiation through a 'two-stream' instability as described by Chandrasekhar, Friedman, and Schutz.

These images were made with Chad Hanna in 2003 and are available to anyone who wants to spice up their r-mode talk. More images are available on request.

You can download Mathematica notebooks that produce sequences of still GIFs used to produce these animated GIFs in the inertial and corotating frames. There is also an image and a notebook for an observer rotating around with the pattern speed of the mode.

This work was supported in part by NSF grant PHY-0245649; but any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

This research area provides opportunities for undergraduate research.

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J. Abadie, et al. (LIGO Scientific Collaboration), "A search for gravitational waves associated with the August 2006 timing glitch of the Vela pulsar," Phys. Rev. D **83**, 042001 (2011)

A. Corsi and B. J. Owen, "Maximum gravitational-wave energy emissible in magnetar flares," Phys. Rev. D **83**, 104014 (2011)

N. K. Johnson-McDaniel and B. J. Owen, "Shear modulus of the hadron-quark mixed phase", (2011) http://www.arxiv.org/abs/1110.4650

J. Abadie, et al. (LIGO Scientific Collaboration), "First search for gravitational waves from the youngest known neutron star," Astrophys. J. **722**, 1504 – 1513 (2010)

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N. Yunes, R. OShaughnessy, B. J. Owen and S. H. S. Alexander, "Testing gravitational parity violation with coincident gravitational waves and short gamma-ray bursts," Phys. Rev. D **82**, 064017 (2010)

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P. Kalmus, K. C. Cannon, S. Marka and B. J. Owen, "Stacking gravitational wave signals from soft gamma repeater bursts," Phys. Rev. D **80**, 042001 (2009)

B. Abbott, et al. (LIGO Scientific Collaboration), "Einstein@Home search for periodic gravitational waves in early S5 LIGO data," Phys. Rev. D **80**, 042003 (2009)

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J. S. Read, B. D. Lackey, B. J. Owen and J. L. Friedman, "Constraints on a phenomenologically parameterized neutron-star equation of state," Phys. Rev. D **79**, 124032 (2009)

B. Abbott, et al. (LIGO Scientific Collaboration), "Einstein@Home search for periodic gravitational waves in LIGO S4 data," Phys. Rev. D **79**, 022001 (2009)
Abstract/Comments

B. Abbott, et al. (LIGO Scientific Collaboration), "All-sky LIGO Search for Periodic Gravitational Waves in the Early S5 Data," Phys. Rev. Lett. **102**, 111102 (2009)

B. J. Owen, "How photon astronomy affects searches for continuous gravitational waves," Class. Quantum Gravity **26**, 204014 (2009)

B. J. Owen, "Probing neutron stars with gravitational waves", (2009) http://www.arxiv.org/abs/0903.2603

B. Krishnan, B. J. Owen, R. Prix and A. M. Sintes, "*Searching for isolated pulsars using Einstein@Home*", (2008)
Abstract/Comments

B. Abbott, et al. (LIGO Scientific Collaboration), "Implications for the Origin of GRB 070201 from LIGO Observations," Astrophys. J. **681**, 1419 – 1430 (2008)

B. Abbott, et al. (LIGO Scientific Collaboration), "Beating the spin-down limit on gravitational wave emission from the Crab pulsar," Astrophys. J. Lett. **683**, L45 – L49 (2008)

B. Abbott, et al. (LIGO Scientific Collaboration), "Search of S3 LIGO data for gravitational wave signals from spinning black hole and neutron star binary inspirals," Phys. Rev. D **78**, 042002 (2008)

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B. Abbott, et al. (LIGO Scientific Collaboration), "Search for gravitational waves from binary inspirals in S3 and S4 LIGO data," Phys. Rev. D **77**, 062002 (2008)

B. Abbott, et al. (LIGO Scientific Collaboration), "Search for Gravitational Waves Associated with 39 Gamma-Ray Bursts Using Data from the Second, Third, and Fourth LIGO Runs," Phys. Rev. D **77**, 062004 (2008)

B. Abbott, et al. (LIGO Scientific Collaboration), "Search for Gravitational Wave Bursts from Soft Gamma Repeaters," Phys. Rev. Lett. **101**, 211102 (2008)

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B. Abbott, et al. (LIGO Scientific Collaboration), "Upper limits on gravitational wave emission from 78 radio pulsars," Phys. Rev. D **76**, 042001 (2007)

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B. Abbott, et al. (LIGO Scientific Collaboration), "Coherent searches for periodic gravitational waves from unknown isolated sources and Scorpius X-1: results from the second LIGO science run," Phys. Rev. D **76**, 082001 (2007)

M. Nayyar and B. J. Owen, "R-modes of accreting neutron stars as persistent sources of gravitational waves," Phys. Rev. D **73**, 084001 (2006)

B. D. Lackey, M. Nayyar and B. J. Owen, "Observational constraints on hyperons in neutron stars," Phys. Rev. D **73**, 024021 (2006)

B. Abbott, et al. (LIGO Scientific Collaboration), "Joint LIGO and TAMA300 search for gravitational waves from inspiralling neutron star binaries," Phys. Rev. D **73**, 102002 (2006)

B. J. Owen, "Detectability of periodic gravitational waves by intial interferometers," Class. Quantum Gravity **23**, S1 – S7 (2006)

B. Abbott, et al. (LIGO Scientific Collaboration), "Search for gravitational waves from galactic and extra-galactic binary neutron stars," Phys. Rev. D **72**, 082001 (2005)

B. Abbott, et al. (LIGO Scientific Collaboration), "First all-sky upper limits from LIGO on the strength of periodic gravitational waves using the Hough transform," Phys. Rev. D **72**, 102004 (2005)

B. J. Owen, "Maximum elastic deformations of compact stars with exotic equations of state," Phys. Rev. Lett. **95**, 211101 (2005)

B. J. Owen and I. Jones, "*When do the pulsar upper limits become interesting?*", (2004) , LIGO-T040192-00-Z

L. Lindblom and B. J. Owen, "Effect of hyperon bulk viscosity on neutron-star r-modes," Phys. Rev. D **65**, 063006 (2002)

B. J. Owen and L. Lindblom, "Gravitational radiation from the r-mode instability," Class. Quantum Gravity **19**, 1247 – 1254 (2002)

B. J. Owen, "Gravitational waves from the r-modes of rapidly rotating neutron stars", in *Gravitational Waves*, Ed.: S Meshkov (AIP, 2000) **523**, p. 55-64

B. J. Owen, "Gravitational waves from neutron-star r-modes", in *Gravitational waves and experimental gravity*, Ed.: J Tran Thanh Van et al (Unspecified Publisher, 2000) p. 131-136

L. Lindblom, B. J. Owen and G. Ushomirsky, "Effect of a neutron-star crust on the r-mode instability," Phys. Rev. D **62**, 084030 (2000)

L. Lindblom, G. Mendell and B. J. Owen, "Second-order rotational effects on the r-modes of neutron stars," Phys. Rev. D **60**, 064006 (1999)

B. J. Owen, L. Lindblom, C. Cutler, B. F. Schutz, A. Vecchio and N. Andersson, "Gravitational waves from hot young rapidly rotating neutron stars," Phys. Rev. D **58**, 084020 (1998)

L. Lindblom, B. J. Owen and S. M. Morsink, "Gravitational radiation instability in hot young neutron stars," Phys. Rev. Lett. **80**, 4843 – 4846 (1998)

*Gravitational waves from compact objects*, National Science Foundation PHY-0245649*Gravitational waves from compact objects*, National Science Foundation Gravity Theory-PHY-0555628*Gravitational waves from compact objects*, National Science Foundation PHY-0855589

Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.