Nuclear-Powered X-ray Millisecond Pulsars

Bhattacharyya, Sudip

doi:10.1007/978-3-030-85198-9_5

Cited by 8 publications

(7 citation statements)

References 130 publications

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“…After 12 s, the burst decays and the thermal cooling is observed (Figure 5). Thus, this is an example of a strong PRE burst (Galloway et al 2008;Degenaar et al 2018;Bhattacharyya 2022) with distinct expansion and contraction phases. Moreover, the bottom right panel of Figure 5 shows the presence of a variable persistent emission contribution during the burst and its evolution.…”

Section: Analysis Of the Thermonuclear Burstmentioning

confidence: 91%

“…The evolution of (bottom right panel of Figure 5) can be interpreted as the increase in the mass accretion rate onto the NS during the burst (Bhattacharyya et al 2018). This increase may indicate the effects of burst radiation-induced Poynting-Robertson (PR) drag on the disc material (Worpel et al 2013;Ji et al 2015;In't Zand & Weinberg 2010;Fragile et al 2020;Speicher et al 2021).…”

Section: The Burstmentioning

confidence: 98%

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Probing spectral and temporal evolution of the neutron star low-mass X-ray binary 4U 1724-30 with AstroSat

Kashyap,

Chakraborty,

Bhattacharyya

2022

Preprint

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We report the broadband spectro-temporal study of the poorly studied accreting neutron star (NS) low mass X-ray binary (LMXB) 4U 1724-30 using data from Soft X-ray Telescope (SXT) and Large Area X-ray Proportional Counters (LAXPC) instruments on board AstroSat. The dim persistent LMXB source was observed with AstroSat over 4 epochs in 2017, all of which corresponded to a low-luminosity non-thermal emission dominated (hard/island) emission state with modest spectral evolution. All the X-ray broadband spectra can be modelled by a combination of thermal emission from the NS boundary layer (BL) or NS surface and a non-thermal emission component possibly originating from the inverse Comptonization of the disc seed photons. We investigate the presence of frequency and energy-dependent variabilities to probe the origin of the disc/coronal fluctuations. We also report the detection of a Type-I X-ray burst displaying a photospheric radius expansion (PRE). During the burst, a hard Xray shortage in the 30-80 keV energy band and the enhancement of the persistent emission reveal the burst feedback on the overall accretion process. Using the touch-down burst flux ∼ 4.25 × 10 −8 erg s −1 cm −2 , the distance of the source is estimated as ∼ 8.4 kpc.

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Section: Analysis Of the Thermonuclear Burstmentioning

confidence: 91%

Section: The Burstmentioning

confidence: 98%

Probing spectral and temporal evolution of the neutron star low-mass X-ray binary 4U 1724-30 with AstroSat

Kashyap,

Chakraborty,

Bhattacharyya

2022

Preprint

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“…While most of these MSPs are in binary systems [1][2][3], they, with very few exceptions, do not accrete matter from the companion star [4]. These MSPs (RMSPs) are powered by neutron star spin or rotational kinetic energy [5]. Another kind of MSP accretes matter from a low-mass companion star (mass < ∼ 1 M ) in a neutron star low-mass X-ray binary (LMXB) system [6].…”

Section: Introductionmentioning

confidence: 99%

“…These are accretion-powered MSPs (AMSPs), also known as X-ray MSPs, and more than 20 such sources are known [2,4]. There is also another set of accreting X-ray MSPs in LMXB systems, which show nuclear-powered X-ray pulsations during thermonuclear X-ray bursts [5]. These bursts occur due to intermittent, unstable burning of accumulated matter on the accreting neutron star surface [7], and an asymmetric brightness pattern on this spinning star during such a burst causes these pulsations [5].…”

Section: Introductionmentioning

confidence: 99%

Spin Equilibrium of Rapidly Spinning Neutron Stars via Transient Accretion

Bhattacharyya

2023

Galaxies

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The concept of spin equilibrium due to an interaction between the stellar magnetosphere and a thin, Keplerian accretion disk, and a well-known formula of the corresponding equilibrium spin frequency, provide a key understanding of spin evolution and the distribution of rapidly spinning neutron stars, viz., millisecond pulsars. However, this concept and formula are for stable accretion, but the mass transfer to most accreting millisecond pulsars is transient and the accretion rate evolves by orders of magnitude during an outburst. In this short and focussed review, we briefly discuss a relatively new concept of the spin equilibrium condition and a new formula for the equilibrium spin frequency for transiently accreting millisecond pulsars. We also review a new method to estimate this equilibrium spin frequency for observed transiently accreting millisecond pulsars, even when a pulsar has not yet attained the spin equilibrium. These will be crucial to probe the spin evolution and distribution of millisecond pulsars, and should also be applicable to all magnetic stars transiently accreting via a thin, Keplerian accretion disk.

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“…During type-I X-ray bursts, NS may produce inhomogeneous thermal emissions on the surface, which manifests as burst oscillations (Strohmayer et al 1996). The type-I X-ray burst oscillations provide us an indirect method to measure the NS spin periods, due to the fact the the oscillation frequencies measured in accreting millisecond X-ray pulsars (AMXPs) are very close to their coherent spin frequencies within a few hertz during the persistent emissions (e.g., Chakrabarty et al 2003, see Watts 2012and Bhattacharyya 2022. Totally, five persistent AMXPs have been observed burst oscillations, and their oscillation frequencies usually showed negligible upward drifting during the cooling tails (Chakrabarty et al 2003;Galloway et al 2008;Bilous & Watts 2019).…”

Section: Introductionmentioning

confidence: 99%

Discovery of a 584.65 Hz Burst Oscillation in the Low Mass X-Ray Binary 4U 1730$-$22

Li¹,

Yu²,

Lu³

et al. 2022

Preprint

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Type-I X-ray burst oscillations are powered by thermonuclear released on the neutron star (NS) surface in low mass X-ray binaries (LMXBs), where the burst oscillation frequencies are close to the NS spin rates. In this work, we report the detection of oscillation at 584.65 Hz during the cooling tail of a type-I X-ray bursts observed from the accreting NS LMXB 4U 1730-22 in 2022 March 20, by the Neutron star Interior Composition Explorer (NICER) telescope. The oscillation signal showed a strong Leahy power, P m ∼ 54.04, around 584.65 Hz, which has single trial and multiple trials confidence levels of 7.05σ and 4.78σ, respectively. The folded pulse profile of the oscillation in the 0.2-10 keV band showed a sinusoidal shape with the fraction amplitude rms of (12.5 ± 1.8)%. We found the oscillation frequency showed insignificant upward drifting, i.e., less than 0.3 Hz, during the cooling tail, similar as the behavior appearing in accreting millisecond X-ray pulsars (AMXP), and indicate the source could be an AMXP spinning at 1.71 ms.

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Nuclear-Powered X-ray Millisecond Pulsars

Cited by 8 publications

References 130 publications

Probing spectral and temporal evolution of the neutron star low-mass X-ray binary 4U 1724-30 with AstroSat

Probing spectral and temporal evolution of the neutron star low-mass X-ray binary 4U 1724-30 with AstroSat

Spin Equilibrium of Rapidly Spinning Neutron Stars via Transient Accretion

Discovery of a 584.65 Hz Burst Oscillation in the Low Mass X-Ray Binary 4U 1730$-$22

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