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Title: MAGNETIC INTERACTIONS IN COALESCING NEUTRON STAR BINARIES

Abstract

It is expected on both evolutionary and empirical grounds that many merging neutron star (NS) binaries are composed of a highly magnetized NS in orbit with a relatively low magnetic field NS. I study the magnetic interactions of these binaries using the framework of a unipolar inductor model. The electromotive force generated across the non-magnetic NS as it moves through the magnetosphere sets up a circuit connecting the two stars. The exact features of this circuit depend on the uncertain resistance in the space between the stars R{sub space}. Nevertheless, I show that there are interesting observational and/or dynamical effects irrespective of its exact value. When R{sub space} is large, electric dissipation as great as {approx}10{sup 46} erg s{sup -1} (for magnetar-strength fields) occurs in the magnetosphere, which would exhibit itself as a hard X-ray precursor in the seconds leading up to merger. With less certainty, there may also be an associated radio transient. When R{sub space} is small, electric dissipation largely occurs in the surface layers of the magnetic NS. This can reach {approx}10{sup 49} erg s{sup -1} during the final {approx}1 s before merger, similar to the energetics and timescales of short gamma-ray bursts. In addition, for dipolemore » fields greater than Almost-Equal-To 10{sup 12} G and a small R{sub space}, magnetic torques spin up the magnetized NS. This drains angular momentum from the binary and accelerates the inspiral. A faster coalescence results in less orbits occurring before merger, which would impact matched-filtering gravitational-wave searches by ground-based laser interferometers and could create difficulties for studying alternative theories of gravity with compact inspirals.« less

Authors:
 [1]
  1. Theoretical Astrophysics, California Institute of Technology, 1200 E California Blvd., M/C 350-17, Pasadena, CA 91125 (United States)
Publication Date:
OSTI Identifier:
22039121
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 755; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; BINARY STARS; COALESCENCE; COSMIC GAMMA BURSTS; DIPOLES; ELECTROMOTIVE FORCE; GAMMA ASTRONOMY; GRAVITATION; GRAVITATIONAL WAVES; HARD X RADIATION; INTERFEROMETERS; LASERS; LAYERS; MAGNETIC FIELDS; NEUTRON STARS; ORBITS; SPIN

Citation Formats

Piro, Anthony L., E-mail: piro@caltech.edu. MAGNETIC INTERACTIONS IN COALESCING NEUTRON STAR BINARIES. United States: N. p., 2012. Web. doi:10.1088/0004-637X/755/1/80.
Piro, Anthony L., E-mail: piro@caltech.edu. MAGNETIC INTERACTIONS IN COALESCING NEUTRON STAR BINARIES. United States. doi:10.1088/0004-637X/755/1/80.
Piro, Anthony L., E-mail: piro@caltech.edu. Fri . "MAGNETIC INTERACTIONS IN COALESCING NEUTRON STAR BINARIES". United States. doi:10.1088/0004-637X/755/1/80.
@article{osti_22039121,
title = {MAGNETIC INTERACTIONS IN COALESCING NEUTRON STAR BINARIES},
author = {Piro, Anthony L., E-mail: piro@caltech.edu},
abstractNote = {It is expected on both evolutionary and empirical grounds that many merging neutron star (NS) binaries are composed of a highly magnetized NS in orbit with a relatively low magnetic field NS. I study the magnetic interactions of these binaries using the framework of a unipolar inductor model. The electromotive force generated across the non-magnetic NS as it moves through the magnetosphere sets up a circuit connecting the two stars. The exact features of this circuit depend on the uncertain resistance in the space between the stars R{sub space}. Nevertheless, I show that there are interesting observational and/or dynamical effects irrespective of its exact value. When R{sub space} is large, electric dissipation as great as {approx}10{sup 46} erg s{sup -1} (for magnetar-strength fields) occurs in the magnetosphere, which would exhibit itself as a hard X-ray precursor in the seconds leading up to merger. With less certainty, there may also be an associated radio transient. When R{sub space} is small, electric dissipation largely occurs in the surface layers of the magnetic NS. This can reach {approx}10{sup 49} erg s{sup -1} during the final {approx}1 s before merger, similar to the energetics and timescales of short gamma-ray bursts. In addition, for dipole fields greater than Almost-Equal-To 10{sup 12} G and a small R{sub space}, magnetic torques spin up the magnetized NS. This drains angular momentum from the binary and accelerates the inspiral. A faster coalescence results in less orbits occurring before merger, which would impact matched-filtering gravitational-wave searches by ground-based laser interferometers and could create difficulties for studying alternative theories of gravity with compact inspirals.},
doi = {10.1088/0004-637X/755/1/80},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 755,
place = {United States},
year = {2012},
month = {8}
}