Dynamical bar-mode instability in rotating and magnetized relativistic stars

Franci, Luca; Pietri, R. De; Dionysopoulou, Kyriaki; Rezzolla, Luciano

doi:10.1103/physrevd.88.104028

Cited by 25 publications

(28 citation statements)

References 62 publications

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“…This value is consistent with the amplitude evolution of the h ¼ 0.15 M ⊙ run, but somewhat smaller than what could be inferred from the h ¼ 0.1 M ⊙ data. However, other physical processes, such as neutrino cooling and angular momentum redistribution due to magnetoturbulence, will likely become dominant over such time scales [22] and might damp the one-armed spiral instability [65][66][67]. As a consequence, our estimate of the survival time of the m ¼ 1 mode should constitute a reasonable upper limit.…”

Section: Hybrid Waveformsmentioning

confidence: 91%

One-armed spiral instability in neutron star mergers and its detectability in gravitational waves

2016

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We study the development and saturation of the m ¼ 1 one-armed spiral instability in remnants of binary neutron star mergers by means of high-resolution long-term numerical relativity simulations. Our results suggest that this instability is a generic outcome of neutron star mergers in astrophysically relevant configurations, including both "stiff" and "soft" nuclear equations of state. We find that, once seeded at merger, the m ¼ 1 mode saturates within ∼10 ms and persists over secular time scales. Gravitational waves emitted by the m ¼ 1 instability have a peak frequency around 1-2 kHz and, if detected, they could be used to constrain the equation of state of neutron stars. We construct hybrid waveforms spanning the entire Advanced LIGO band by combining our high-resolution numerical data with state-of-the-art effective-onebody waveforms including tidal effects. We use the complete hybrid waveforms to study the detectability of the one-armed spiral instability for both Advanced LIGO and the Einstein Telescope. We conclude that the one-armed spiral instability is not an efficient gravitational wave emitter. Even under very optimistic assumptions, Advanced LIGO will only be able to detect the one-armed instability up to ∼3 Mpc, which corresponds to an event rate of 10 −7 yr −1 to 10 −4 yr −1 . Third-generation detectors or better will likely be required to observe the one-armed instability.

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Section: Hybrid Waveformsmentioning

confidence: 91%

One-armed spiral instability in neutron star mergers and its detectability in gravitational waves

2016

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“…They can only set in when the rotation period is very close to the mass-shedding limit (∼1-10 ms); therefore, they are expected to be suppressed before phase 2 sets in. (ii) Secular instabilities (e.g., r-mode, f-mode instabilities) act on time scales ranging from ∼1 s to several years; they become effective at temperatures T ≲ 10 10 K, typically reached after the first minute of life of the PNS [13][14][15]. In phase 2, the star is too hot (T ≳ 10 11 K) for secular instabilities to be effective (at least, excluding the case of quark stars or stars having exotic matter in the core).…”

Section: Introductionmentioning

confidence: 99%

Rotating protoneutron stars: Spin evolution, maximum mass, and I-Love-Q relations

et al. 2014

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Shortly after its birth in a gravitational collapse, a protoneutron star enters in a phase of quasistationary evolution characterized by large gradients of the thermodynamical variables and intense neutrino emission. In a few tens of seconds, the gradients smooth out while the star contracts and cools down, until it becomes a neutron star. In this paper we study this phase of the protoneutron star life including rotation, and employing finite-temperature equations of state. We model the evolution of the rotation rate, and determine the relevant quantities characterizing the star. Our results show that an isolated neutron star cannot reach, at the end of the evolution, the maximum values of mass and rotation rate allowed by the zero-temperature equation of state. Moreover, a mature neutron star evolved in isolation cannot rotate too rapidly, even if it is born from a protoneutron star rotating at the mass-shedding limit. We also show that the I-Love-Q relations are violated in the first second of life, but they are satisfied as soon as the entropy gradients smooth out.

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“…There is clear evidence that it may develop during stellar core-collapse (Ott et al 2005(Ott et al , 2007Scheidegger et al 2008;Kuroda & Umeda 2010) and it has been seen in numerical evolutions of rapidly rotating cold neutron stars (Saijo & Yoshida 2006;Cerdá-Durán et al 2007;Corvino et al 2010). Recently, with the development of magneto-hydrodynamical simulations, the impact of the magnetic field on the dynamical instabilities has been explored (Camarda et al 2009;Franci et al 2013;Muhlberger et al 2014). The results suggest that the bar-mode instability can be suppressed by a very strong magnetic field, B ∼ > 10 16 G. Analytical work, based on a rotating system with cylindrical geometry, has shown that the low T/W instability can be similarly suppressed by a strong toroidal magnetic field B > 10 16 G (Fu & Lai 2011).…”

Section: Introductionmentioning

confidence: 99%

The intimate relation between the low T/W instability and the corotation point

Passamonti

Andersson

2014

Monthly Notices of the Royal Astronomical Society

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We study the low T/W instability associated with the f-mode of differentially rotating stars. Our stellar models are described by a polytropic equation of state and the rotation profile is given by the standard j-constant law. The properties of the relevant oscillation modes, including the instability growth time, are determined from time evolutions of the linearised dynamical equations in Newtonian gravity. In order to analyse the instability we monitor also the canonical energy and angular momentum. Our results demonstrate that the l = m = 2 f-mode becomes unstable as soon as a co-rotation point develops inside the star (i.e. whenever there is a point where the mode's pattern speed matches the bulk angular velocity). Considering various degrees of differential rotation, we show that the instability grows faster deep inside the corotation region and deduce an empirical relation that correlates the mode frequency and the star's parameters, which captures the main features of the l = m = 2 f-mode growth time. This function is proportional to the product of the kinetic to gravitational energy ratio and the gradient of the star's spin, strengthening further the relationship between the co-rotation point and the low T/W instability. We briefly consider also the l = m = 2 r-mode and demonstrate that it never moves far inside the co-rotation region even for significant differential rotation.

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Dynamical bar-mode instability in rotating and magnetized relativistic stars

Cited by 25 publications

References 62 publications

One-armed spiral instability in neutron star mergers and its detectability in gravitational waves

One-armed spiral instability in neutron star mergers and its detectability in gravitational waves

Rotating protoneutron stars: Spin evolution, maximum mass, and I-Love-Q relations

The intimate relation between the low T/W instability and the corotation point

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