The Stochastic X-Ray Variability of the Accreting Millisecond Pulsar MAXI J0911–655

Bult, Peter

doi:10.3847/1538-4357/aa607f

Cited by 11 publications

(15 citation statements)

References 47 publications

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“…XTE J1701-462; Bu et al 2015). The rms spectra of broad-band noise components of NS increase with energy in some cases (Bu et al 2015;Bult 2017, studying XTE J1701-462 and MAXI J0911-655, respectively), as MAXI J1727-203 did during most of the outburst. Unfortunately, neither of those works present the evolution of the rms spectra during a whole outburst, so at the moment we cannot compare the evolution of these sources and that of MAXI J1727-203.…”

Section: Nature Of the Compact Object In Maxi J1727-203mentioning

confidence: 93%

X-ray spectral and timing evolution of MAXI J1727–203 with NICER

Alabarta

Altamirano

Méndez

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present a detailed X-ray spectral and variability study of the full 2018 outburst of MAXI J1727–203 using NICER observations. The outburst lasted approximately four months. Spectral modelling in the 0.3–10 keV band shows the presence of both a soft thermal and a hard Comptonised component. The analysis of these components shows that MAXI J1727–203 evolved through the soft, intermediate and hard spectral states during the outburst. We find that the soft (disc) component was detected throughout almost the entire outburst, with temperatures ranging from ∼0.4 keV, at the moment of maximum luminosity, to ∼0.1 keV near the end of the outburst. The power spectrum in the hard and intermediate states shows broadband noise up to 20 Hz, with no evidence of quasi-periodic oscillations. We also study the rms spectra of the broadband noise at 0.3 − 10 keV of this source. We find that the fractional rms increases with energy in most of the outburst except during the hard state, where the fractional rms remains approximately constant with energy. We also find that, below 3 keV, the fractional rms follows the same trend generally observed at energies >3 keV, a behaviour known from previous studies of black holes and neutron stars. The spectral and timing evolution of MAXI J1727–203, as parametrised by the hardness-intensity, hardness-rms, and rms-intensity diagrams, suggest that the system hosts a black hole, although we could not rule out a neutron star.

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Section: Nature Of the Compact Object In Maxi J1727-203mentioning

confidence: 93%

X-ray spectral and timing evolution of MAXI J1727–203 with NICER

Alabarta

Altamirano

Méndez

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…In the current work we are only interested in the broad picture and to estimate the Poisson level, but we found no significant effect on the resulting PDS. we defer detailed analyses of our PDS to future work (but see already Ferrigno et al (2017) and Bult (2017) for such detailed studies for IGR J00291+5934 and Swift J0911.9-6452, respectively). To determine the strength of the noise components we observed in the PDS, we calculated the integrated noise strengths between 9.765625 × 10 −4 and 128 Hz (2 −10 -2 7 Hz).…”

Section: X-ray Timing Analysismentioning

confidence: 99%

“…Recently Bult (2017) suggested that the PDS obtained (using XMM-Newton data) during the 2016 outburst of another AMXP, Swift J0911.9-6452, resembled that of IGR J00291+5934. Therefore, we also included this source in our analysis and we confirm the noise properties reported for this source by Bult (2017).…”

Section: Igr J00291+5934 and Swift J09119-6452mentioning

confidence: 99%

“…Since this source was also observed using XMM-Newton during its most recent outburst (in 2015; Ferrigno et al 2017) we included this source in our sample as well. Very recently, Bult (2017) suggested that the variability properties (studied using XMM-Newton and NuSTAR observations) of the transient AMXP Swift J0911.9-6452 (during its 2016/2017 outburst 5 ; Sanna et al 2017a) resembled that of IGR J00291+5934. Therefore, we also included Swift J0911.9-6452 in our analysis.…”

Section: Parikhmentioning

confidence: 99%

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Rapid X-ray variability properties during the unusual very hard state in neutron-star low-mass X-ray binaries

Wijnands

Parikh

Altamirano

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Here we study the rapid X-ray variability (using XMM-Newton observations) of three neutron-star low-mass X-ray binaries (1RXS J180408.9-342058, EXO 1745-248, and IGR J18245-2452) during their recently proposed very hard spectral state (Parikh et al. 2017). All our systems exhibit a strong to very strong noise component in their power density spectra (rms amplitudes ranging from 34% to 102%) with very low characteristic frequencies (as low as 0.01 Hz). These properties are more extreme than what is commonly observed in the canonical hard state of neutron-star low-mass X-ray binaries observed at X-ray luminosities similar to those we observe from our sources. This suggests that indeed the very hard state is a distinct spectral-timing state from the hard state, although we argue that the variability behaviour of IGR J18245-2452 is very extreme and possibly this source was in a very unusual state. We also compare our results with the rapid X-ray variability of the accreting millisecond X-ray pulsars IGR J00291+5934 and Swift J0911.9-6452 (also using XMM-Newton data) for which previously similar variability phenomena were observed. Although their energy spectra (as observed using the Swift X-ray telescope) were not necessarily as hard (i.e., for Swift J0911.9-6452) as for our other three sources, we conclude that likely both sources were also in very similar state during their XMM-Newton observations. This suggest that different sources that are found in this new state might exhibit different spectral hardness and one has to study both the spectral as well as rapid variability to identify this unusual state.

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“…However, more recently the AMXP MAXI J0911-655 has been shown to exhibit a similar broad noise structure, but with LF QPOs that fall along the expected frequency relation (Bult 2017), casting doubt on this interpretation.…”

Section: The 20 Mhz Qpomentioning

confidence: 99%

Quasi-periodic Pulse Amplitude Modulation in the Accreting Millisecond Pulsar IGR J00291+5934

Bult

Doesburgh

Klis

2017

ApJ

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We introduce a new method for analysing the aperiodic variability of coherent pulsations in accreting millisecond X-ray pulsars. Our method involves applying a complex frequency correction to the time-domain light curve, allowing for the aperiodic modulation of the pulse amplitude to be robustly extracted in the frequency domain. We discuss the statistical properties of the resulting modulation spectrum and show how it can be correlated with the non-pulsed emission to determine if the periodic and aperiodic variability are coupled processes. Using this method, we study the 598.88 Hz coherent pulsations of the accreting millisecond X-ray pulsar IGR J00291+5934 as observed with the Rossi X-ray Timing Explorer and XMM-Newton. We demonstrate that our method easily confirms the known coupling between the pulsations and a strong 8 mHz QPO in XMM-Newton observations. Applying our method to the RXTE observations, we further show, for the first time, that the much weaker 20 mHz QPO and its harmonic are also coupled the pulsations. We discuss the implications of this coupling and indicate how it may be used to extract new information on the underlying accretion process.

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The Stochastic X-Ray Variability of the Accreting Millisecond Pulsar MAXI J0911–655

Cited by 11 publications

References 47 publications

X-ray spectral and timing evolution of MAXI J1727–203 with NICER

X-ray spectral and timing evolution of MAXI J1727–203 with NICER

Rapid X-ray variability properties during the unusual very hard state in neutron-star low-mass X-ray binaries

Quasi-periodic Pulse Amplitude Modulation in the Accreting Millisecond Pulsar IGR J00291+5934

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