AR Scorpii and possible gravitational wave radiation from pulsar white dwarfs

Franzon, B.; Schramm, Stefan

doi:10.1093/mnras/stx397

Cited by 17 publications

(13 citation statements)

References 42 publications

(54 reference statements)

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“…1. It is worth mentioning that for the AR Sco system that has a WD in the mass range of 0.81M < M AR < 1.29M (Franzon & Schramm 2017), we adopted the mass value of 0.81M to maximize the GW amplitude. For AE Aqr and RX J0648 systems, although mass values are not well established, we use the mass values according to Choi & Yi (2000) and Mereghetti et al (2011), respectively. At this point it is interesting to see what kind of information we can obtain from these results.…”

Section: Systemsmentioning

confidence: 99%

“…Different possibilities of generation of continuous GWs have already been proposed (see e.g., Bonazzola & Gourgoulhon 1996;De Araujo et al 2016a,b;Mukhopadhyay et al 2017;De Araujo et al 2017;Gao et al 2017;Franzon & Schramm 2017;Pereira et al 2018;De Araujo et al 2019, and references therein). More recently, Kalita & Mukhopadhyay (2019) show that continuous GWs can be emitted from rotating magnetized WDs and will possibly be detected by the upcoming GW detectors such as LISA, DECIGO and BBO.…”

Section: Introductionmentioning

confidence: 99%

“…1979;De Jager et al 1994;Choi & Yi 2000;Franzon & Schramm 2017;Mereghetti et al 2011) GW amplitude as a function of accreted mass to AE Aqr, AR Sco and RX J0648…”

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confidence: 99%

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Gravitational waves from fast-spinning white dwarfs

Sousa

Coelho

2020

Monthly Notices of the Royal Astronomical Society

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Two mechanisms of gravitational waves (GWs) emission in fast-spinning white dwarfs (WDs) are investigated: accretion of matter and magnetic deformation. In both cases, the GW emission is generated by an asymmetry around the rotation axis of the star. However, in the first case, the asymmetry is due to the amount of accreted matter on the magnetic poles, while in the second case it is due to the intense magnetic field. We have estimated the GW amplitude and luminosity for three binary systems that have a fast-spinning magnetized WD, namely, AE Aquarii, AR Scorpii and RX J0648.0-4418. We find that, for the first mechanism, the systems AE Aquarii and RX J0648.0-4418 can be observed by the space detectors BBO and DECIGO if they have an amount of accreted mass of δm ≥ 10 −5 M . For the second mechanism, the three systems studied require that the WD have a magnetic field above ∼ 10 9 G to emit GWs that can be detected by BBO. We also verified that, in both mechanisms, the gravitational luminosity has an irrelevant contribution to the spindown luminosity of these three systems. Therefore, other mechanisms of energy emission are needed to explain the spindown of these objects.

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Section: Systemsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Gravitational waves from fast-spinning white dwarfs

Sousa

Coelho

2020

Monthly Notices of the Royal Astronomical Society

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“…In the non-relativistic regime, WDs are predicted to have a density structure like that of a polytrope with an index of 1.5, and we calculate a moment of inertia of I = 0.25M R 2 = 2 × 10 43 kg m 2 . However, the strong magnetic fields and the rapid spin rate of the WD may have an effect on the precise value of the moment of inertia (Franzon & Schramm 2017).…”

Section: Spin-down Luminositymentioning

confidence: 99%

High-time-resolution Photometry of AR Scorpii: Confirmation of the White Dwarf’s Spin-down

Stiller

Garnavich

Wood

et al. 2018

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The unique binary AR Scorpii consists of an asynchronously rotating, magnetized white dwarf (WD) that interacts with its red-dwarf companion to produce a large-amplitude, highly coherent pulsation every 1.97 minutes. Over the course of two years, we obtained thirty-nine hours of time-resolved, optical photometry of AR Sco at a typical cadence of 5 seconds to study this pulsation. We find that it undergoes significant changes across the binary orbital period and that its amplitude, phase, and waveform all vary as a function of orbital phase. We show that these variations can be explained by constructive and destructive interference between two periodic, double-peaked signals: the spin-orbit beat pulse, and a weaker WD spin pulse. Modelling of the light curve indicates that in the optical, the amplitude of the primary spin pulse is 50% of the primary beat amplitude, while the secondary maxima of the beat and spin pulses have similar amplitudes. Finally, we use our timings of the beat pulses to confirm the presence of the disputed spin-down of the WD. We measure a beat-frequency derivative ofν = (−5.14 ± 0.32) × 10 −17 Hz s −1 and show that this is attributable to the spin-down of the WD. This value is approximately twice as large as the estimate from Marsh et al. (2016) but is nevertheless consistent with the constraints established in Potter & Buckley (2018). Our precise measurement of the spin-down rate confirms that the decaying rotational energy of the magnetized white dwarf is sufficient to power the excess electromagnetic radiation emitted by the binary.

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“…Φ(t) is the signal phase function, Izz is the moment of inertial about z-axis, ǫ is the measure of ellipticity of the star and d is the distance of the star from the detector. As rotating B-WDs are ellipsoid and could rotate faster than their standard counter-parts, they also could be plausible candidates for continuous gravitational wave signal (see also Heyl 2000;Franzon & Schramm 2017). A B-WD with mass ∼ 2M⊙, polar radius ∼ 700 km, Ps ∼ 1 sec (Subramanian & Mukhopadhyay 2015), ǫ ∼ 5 × 10 −4 and at ∼ 100 pc away from us would produce h0 ∼ 10 −22 , which is within the sensitivity of the Einstein@Home search for early Laser Interferometer Gravitational Wave Observatory (LIGO) S5 data (Palomba et al 2013).…”

Section: Emission Of Gravitational Wave and Star-quakementioning

confidence: 99%

AR Sco as a possible seed of highly magnetized white dwarf

Mukhopadhyay

Rao

Bhatia

2017

Monthly Notices of the Royal Astronomical Society

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We explore the possibility that the recently discovered white dwarf pulsar AR Sco acquired its high spin and magnetic field due to repeated episodes of accretion and spindown. An accreting white dwarf can lead to a larger mass and consequently a smaller radius thus causing an enhanced rotation period and magnetic field. This spinning magnetic white dwarf temporarily can inhibit accretion, spin down, and, eventually, the accretion can start again due to the shrinking of the binary period by gravitational radiation. A repeat of the above cycle can eventually lead to a high magnetic field white dwarf, recently postulated to be the reason for over-luminous type Ia supernovae. We also point out that these high magnetic field spinning white dwarfs are attractive sites for gravitational radiation. MODERATELY MAGNETIZED WHITEDWARFS: PULSAR AR SCO AR Sco has been shown to be a rotating magnetised white dwarf (Marsh et al. 2016). This is argued based on various properties of it, e.g. increasing optical flux detected in radio, c 0000 RAS

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AR Scorpii and possible gravitational wave radiation from pulsar white dwarfs

Cited by 17 publications

References 42 publications

Gravitational waves from fast-spinning white dwarfs

Gravitational waves from fast-spinning white dwarfs

High-time-resolution Photometry of AR Scorpii: Confirmation of the White Dwarf’s Spin-down

AR Sco as a possible seed of highly magnetized white dwarf

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