Erratum: X-ray coherent pulsations during a sub-luminous accretion disc state of the transitional millisecond pulsar XSS J12270–4859

ABSTRACT A millisecond pulsar having an ellipticity, which is an asymmetric mass distribution around its spin-axis, could emit continuous gravitational waves, which have not been detected so far. An indirect way to infer such waves is to estimate the contribution of the waves to the spin-down rate of the pulsar. The transitional pulsar PSR J1023+0038 is ideal and unique for this purpose because this is the only millisecond pulsar for which the spin-down rate has been measured in both accreting and non-accreting states. Here, we infer, from our formalism based on the complete torque budget equations and the pulsar magnetospheric origin of observed γ-rays in the two states, that PSR J1023+0038 should emit gravitational waves due to a permanent ellipticity of the pulsar. The formalism also explains some other main observational aspects of this source in a self-consistent way. As an example, our formalism naturally infers the accretion disc penetration into the pulsar magnetosphere, and explains the observed X-ray pulsations in the accreting state using the standard and well-accepted scenario. This, in turn, infers the larger pulsar spin-down power in the accreting state, which, in our formalism, explains the observed larger γ-ray emission in this state. Exploring wide ranges of parameter values of PSR J1023+0038, and not assuming an additional source of stellar ellipticity in the accreting state, we find the misaligned mass quadrupole moment of the pulsar in the range of (0.92–1.88) × 1036 g cm2, implying an ellipticity range of (0.48–0.93) × 10−9.

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X-ray iron line variability for the model of an orbiting flare above a black hole accretion disc

10.1063/1.1434772 ◽

2001 ◽

Author(s):

Mateusz Ruszkowski

Keyword(s):

Black Hole ◽

Accretion Disc ◽

Iron Line ◽

X Ray ◽

Black Hole Accretion ◽

Hole Accretion

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Simultaneous X-ray and radio observations of the transitional millisecond pulsar candidate CXOU J110926.4–650224

Astronomy and Astrophysics ◽

10.1051/0004-6361/202141431 ◽

2021 ◽

Vol 655 ◽

pp. A52

Author(s):

F. Coti Zelati ◽

B. Hugo ◽

D. F. Torres ◽

D. de Martino ◽

A. Papitto ◽

...

Keyword(s):

Radio Emission ◽

Flux Density ◽

Millisecond Pulsar ◽

Radio Emissions ◽

X Ray ◽

Link Type ◽

Upper Limit ◽

Variability Pattern ◽

Average Flux ◽

Compact Array

We present the results of simultaneous observations of the transitional millisecond pulsar (tMSP) candidate CXOU J110926.4–650224 with the XMM-Newton satellite and the MeerKAT telescope. The source was found at an average X-ray luminosity of LX ≃ 7 × 1033 erg s−1 over the 0.3−10 keV band (assuming a distance of 4 kpc) and displayed a peculiar variability pattern in the X-ray emission, switching between high, low and flaring modes on timescales of tens of seconds. A radio counterpart was detected at a significance of 7.9σ with an average flux density of ≃33 μJy at 1.28 GHz. It showed variability over the course of hours and emitted a ≃10-min long flare just a few minutes after a brief sequence of multiple X-ray flares. No clear evidence for a significant correlated or anticorrelated variability pattern was found between the X-ray and radio emissions over timescales of tens of minutes and longer. CXOU J110926.4–650224 was undetected at higher radio frequencies in subsequent observations performed with the Australia Telescope Compact Array, when the source was still in the same X-ray sub-luminous state observed before, down to a flux density upper limit of 15 μJy at 7.25 GHz (at 3σ). We compare the radio emission properties of CXOU J110926.4–650224 with those observed in known and candidate tMSPs and discuss physical scenarios that may account for its persistent and flaring radio emissions.

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X-ray Dips in AGN and Microquasars – Collapse Timescales of Inner Accretion Disc

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3838 ◽

2020 ◽

Author(s):

Mayur B Shende ◽

Prashali Chauhan ◽

Prasad Subramanian

Keyword(s):

Collisionless Plasma ◽

Cosmic Ray ◽

Outer Radius ◽

Accretion Disc ◽

Accretion Discs ◽

X Rays ◽

Temporal Behaviour ◽

X Ray ◽

Ray Diffusion ◽

3C 120

Abstract The temporal behaviour of X-rays from some AGN and microquasars is thought to arise from the rapid collapse of the hot, inner parts of their accretion discs. The collapse can occur over the radial infall timescale of the inner accretion disc. However, estimates of this timescale are hindered by a lack of knowledge of the operative viscosity in the collisionless plasma comprising the inner disc. We use published simulation results for cosmic ray diffusion through turbulent magnetic fields to arrive at a viscosity prescription appropriate to hot accretion discs. We construct simplified disc models using this viscosity prescription and estimate disc collapse timescales for 3C 120, 3C 111, and GRS 1915+105. The Shakura-Sunyaev α parameter resulting from our model ranges from 0.02 to 0.08. Our inner disc collapse timescale estimates agree well with those of the observed X-ray dips. We find that the collapse timescale is most sensitive to the outer radius of the hot accretion disc.

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The most luminous blue quasars at 3.0

Astronomy and Astrophysics ◽

10.1051/0004-6361/202141356 ◽

2021 ◽

Author(s):

E. Lusso ◽

E. Nardini ◽

S. Bisogni ◽

G. Risaliti ◽

R. Gilli ◽

...

Keyword(s):

Accretion Disc ◽

X Ray

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Quasi-simultaneous Radio/X-Ray Observations of the Candidate Transitional Millisecond Pulsar 3FGL J1544.6−1125 during its Low-luminosity Accretion-disk State

The Astrophysical Journal ◽

10.3847/1538-4357/ac1ff7 ◽

2021 ◽

Vol 923 (1) ◽

pp. 3

Author(s):

Amruta D. Jaodand ◽

Adam T. Deller ◽

Nina Gusinskaia ◽

Jason W. T. Hessels ◽

James C. A. Miller-Jones ◽

...

Keyword(s):

Accretion Disk ◽

Radio Continuum ◽

Continuum Emission ◽

Large Array ◽

Millisecond Pulsar ◽

Very Large Array ◽

X Ray ◽

Upper Limit ◽

5 Ghz ◽

Variable Radio

Abstract 3FGL J1544.6−1125 is a candidate transitional millisecond pulsar (tMSP). Similar to the well-established tMSPs—PSR J1023+0038, IGR J18245−2452, and XSS J12270−4859—3FGL J1544.6−1125 shows γ-ray emission and discrete X-ray “low” and “high” modes during its low-luminosity accretion-disk state. Coordinated radio/X-ray observations of PSR J1023+0038 in its current low-luminosity accretion-disk state showed rapidly variable radio continuum emission—possibly originating from a compact, self-absorbed jet, the “propellering” of accretion material, and/or pulsar moding. 3FGL J1544.6−1125 is currently the only other (candidate) tMSP system in this state, and can be studied to see whether tMSPs are typically radio-loud compared to other neutron star binaries. In this work, we present a quasi-simultaneous Very Large Array and Swift radio/X-ray campaign on 3FGL J1544.6−1125. We detect 10 GHz radio emission varying in flux density from 47.7 ± 6.0 μJy down to ≲15 μJy (3σ upper limit) at four epochs spanning three weeks. At the brightest epoch, the radio luminosity is L 5 GHz = (2.17 ± 0.17) × 1027 erg s−1 for a quasi-simultaneous X-ray luminosity L 2–10 keV = (4.32 ± 0.23) × 1033 erg s−1 (for an assumed distance of 3.8 kpc). These luminosities are close to those of PSR J1023+0038, and the results strengthen the case that 3FGL J1544.6−1125 is a tMSP showing similar phenomenology to PSR J1023+0038.

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