The 2019 super-Eddington outburst of RX J0209.6−7427: detection of pulsations and constraints on the magnetic field strength

Vasilopoulos, Georgios; Ray, Paul S.; Gendreau, Keith C.; Jenke, P.; Jaisawal, Gaurava K.; Wilson-Hodge, C.; Strohmayer, Tod E.; Altamirano, D.; Iwakiri, W.; Wolff, M. T.; Guillot, Sebastien; Malacaria, C.; Stevens, Abigail

doi:10.1093/mnras/staa991

Cited by 56 publications

(47 citation statements)

References 85 publications

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“…Nevertheless, a large opening angle is consistent with the large truncation radius of the disk in M51 ULX-7, which was derived from its temporal properties and is consistent with the NS rotating near equilibrium (e.g., Erkut et al 2020;Vasilopoulos et al 2020a). Similar findings that suggest low or no beaming at all have been discussed based on spectrotemporal properties of ULXPs (e.g., NGC 300 ULX-1 Vasilopoulos et al 2018Vasilopoulos et al , 2019, or a pulse profile evolution of X-ray pulsars during super-Eddington outbursts (e.g., Koliopanos & Vasilopoulos 2018;Vasilopoulos et al 2020b). This would mean that the proposed relation between mass accretion rate and beaming factor b, i.e.…”

Section: Constraints On Orbit Inclination and Ulx Beamingsupporting

confidence: 76%

Chandra Probes the X-Ray Variability of M51 ULX-7: Evidence of Propeller Transition and X-Ray Dips on Orbital Periods

Vasilopoulos

Koliopanos

Haberl

et al. 2021

ApJ

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We report on the temporal properties of the ultraluminous X-ray (ULX) pulsar M51 ULX-7 inferred from the analysis of the 2018-2020 Swift/X-ray Telescope monitoring data and archival Chandra data obtained over a period of 33 days in 2012. We find an extended low flux state, which might be indicative of propeller transition, lending further support to the interpretation that the neutron star is rotating near equilibrium. Alternatively, this offstate could be related to a variable superorbital period. Moreover, we report the discovery of periodic dips in the X-ray light curve that are associated with the binary orbital period. The presence of the dips implies a configuration where the orbital plane of the binary is closer to an edge-on orientation, and thus demonstrates that favorable geometries are not necessary in order to observe ULX pulsars. These characteristics are similar to those seen in prototypical X-ray pulsars such as Her X-1 and SMC X-1 or other ULX pulsars such as NGC 5907 ULX1.

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Section: Constraints On Orbit Inclination and Ulx Beamingsupporting

confidence: 76%

Chandra Probes the X-Ray Variability of M51 ULX-7: Evidence of Propeller Transition and X-Ray Dips on Orbital Periods

Vasilopoulos

Koliopanos

Haberl

et al. 2021

ApJ

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“…Giant flares with peak X-ray luminosities sometimes in excess of 10 39 erg s −1 are a feature of NSs in Be X-ray binaries (Martin et al 2014), which are associated with moderately young stellar populations. Even in those cases, though, a smooth, gradual decline from peak luminosity is observed over several weeks, consistent with the viscous timescale of the (transient) accretion disk (Vasilopoulos et al 2020;Wilson-Hodge et al 2018;Tsygankov et al 2017;Lutovinov et al 2017).…”

Section: Nature Of the Compact Objectsupporting

confidence: 61%

Quasi periodic whispers from a transient ULX in M\,101: signatures of a fast-spinning neutron star?

Urquhart,

Soria,

Di Stefano

et al. 2022

Preprint

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We have studied the unusual time variability of an ultraluminous X-ray source in M 101, 4XMM J140314.2+541806 (henceforth, J1403), using Chandra and XMM-Newton data. Over the last two decades, J1403 has shown short-duration outbursts with an X-ray luminosity ∼1-3 ×10 39 erg s −1 , and longer intervals at luminosities ∼0.5-1 ×10 38 erg s −1 . The bimodal behaviour and fast outburst evolution (sometimes only a few days) are more consistent with an accretor/propeller scenario for a neutron star than with the canonical outburst cycles of stellar-mass black holes. If this scenario is correct, the luminosities in the accretor and propeller states suggest a fast spin (𝑃 ≈ 5 ms) and a low surface magnetic field (𝐵 ∼ 10 10 G), despite our identification of J1403 as a high-mass X-ray binary. The most striking property of J1403 is the presence of strong ∼600-s quasi periodic oscillations (QPOs), mostly around frequencies of ≈1.3-1.8 mHz, found at several epochs during the ultraluminous regime. We illustrate the properties of such QPOs, in particular their frequency and amplitude changes between and within observations, with a variety of techniques (Fast Fourier Transforms, Lomb-Scargle periodograms, weighted wavelet Z-transform analysis). The QPO frequency range <10 mHz is an almost unexplored regime in X-ray binaries and ultraluminous X-ray sources. We compare our findings with the (few) examples of very low frequency variability found in other accreting sources, and discuss possible explanations (Lense-Thirring precession of the inner flow or outflow; radiation pressure limit-cycle instability; marginally stable He burning on the neutron star surface).

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“…Pulsation periods and the associated uncertainties were also calculated by fitting the pulse times of arrival (TOA) with a timing model. We followed the methodology described by Ray et al (2011), that has been applied to other HMXB pulsars (Ray et al 2019b;Vasilopoulos et al 2019Vasilopoulos et al , 2020. We subdivided the data into 10-20 intervals and generated TOAs by comparing the pulse profile of each interval with a template profile.…”

Section: Timing Analysismentioning

confidence: 99%

Revisiting the spectral and timing properties of 4U 1909+07 with NuSTAR and Astrosat

Jaisawal

Naik

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present the results obtained from the analysis of high mass X-ray binary pulsar 4U 1909+07 using NuSTAR and Astrosat observations in 2015 and 2017 July, respectively. X-ray pulsations at ≈604 s are clearly detected in our study. Based on the long term spin-frequency evolution, the source is found to spun up in the last 17 years. We observed a strongly energy-dependent pulse profile that evolved from a complex broad structure in soft X-rays into a profile with a narrow emission peak followed by a plateau in energy ranges above 20 keV. This behaviour ensured a positive correlation between the energy and pulse fraction. The pulse profile morphology and its energy-evolution are almost similar during both the observations, suggesting a persistent emission geometry of the pulsar over time. The broadband energy spectrum of the pulsar is approximated by an absorbed high energy exponential cutoff power law model with iron emission lines. In contrast to the previous report, we found no statistical evidence for the presence of cyclotron absorption features in the X-ray spectra. We performed phase-resolved spectroscopy by using data from the NuSTAR observation. Our results showed a clear signature of absorbing material at certain pulse-phases of the pulsar. These findings are discussed in terms of stellar wind distribution and its effect on the beam geometry of this wind-fed accreting neutron star. We also reviewed the subsonic quasi-spherical accretion theory and its implication on the magnetic field of 4U 1909+07 depending on the global spin-up rate.

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The 2019 super-Eddington outburst of RX J0209.6−7427: detection of pulsations and constraints on the magnetic field strength

Cited by 56 publications

References 85 publications

Chandra Probes the X-Ray Variability of M51 ULX-7: Evidence of Propeller Transition and X-Ray Dips on Orbital Periods

Chandra Probes the X-Ray Variability of M51 ULX-7: Evidence of Propeller Transition and X-Ray Dips on Orbital Periods

Quasi periodic whispers from a transient ULX in M\,101: signatures of a fast-spinning neutron star?

Revisiting the spectral and timing properties of 4U 1909+07 with NuSTAR and Astrosat

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