Post-flare formation of the accretion stream and a dip in pulse profiles of LMC X–4

Beri, Aru; Paul, Biswajit

doi:10.1016/j.newast.2017.05.001

Cited by 13 publications

(14 citation statements)

References 32 publications

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“…The pulse profiles of both Observation 02 and Observation 08 show a 0.25 cycle phase shift between intervals that contain flares and intervals that do not. Similar phase shifts have previously been seen during LMC X-4's flares by Beri & Paul (2017). The phase shift visible in the pulse profiles could be caused by a number of effects.…”

Section: Fractional Rms Amplitudesupporting

confidence: 78%

Discovery of Pulsation Dropout and Turn-on during the High State of the Accreting X-Ray Pulsar LMC X-4

Brumback

Hickox

Bachetti

et al. 2018

ApJL

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Two NuSTAR observations of the luminous X-ray pulsar LMC X-4 in October and November 2015 captured several bright accretion flares from this source, which has a long history of stable pulse and superorbital behavior. We present a timing analysis of these data in which we detect a rapid pulse "turn-on" in association with the accretion flares, during which the source reaches super-Eddington luminosities. Pulsations, which are normally seen from this source, are found to only occur for approximately one hour before and during the bright flares. Beyond one hour before and after the flares, we find pulsations to be weak or nonexistent, with fractional RMS amplitudes of less than 0.05. At the onset of the flare, the pulse profiles exhibit a phase shift of 0.25 cycles that could be associated with a change in the emission geometry. This increase in pulse strength occurring well before the flare cannot be explained by the propeller effect, and potentially offers a connection between the magnetic properties of pulsars that accrete close to their Eddington limits and ULX pulsars.

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Section: Fractional Rms Amplitudesupporting

confidence: 78%

Discovery of Pulsation Dropout and Turn-on during the High State of the Accreting X-Ray Pulsar LMC X-4

Brumback

Hickox

Bachetti

et al. 2018

ApJL

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Section: Introductionsupporting

confidence: 70%

“…LMC X-4 shows short super-Eddington bursts, during which the pulse profile of the pulsar changes both in phase and shape. Same has been observed with RXTE-PCA (Levine, Rappaport & Zojcheski 2000), XMM-Newton (Beri & Paul 2017) and NuStar (Shtykovsky et al 2018). SMC X-1 is a wind and disk fed binary pulsar located in the Small Magellanic Cloud (SMC), which has been observed with both at sub-Eddington and super-Eddington luminosities and shows short and intense bursts like LMC X-4 (Price et al 1971;Ulmer et al 1973;Coe et al 1981).…”

Section: Introductionmentioning

confidence: 77%

“…The source was found to show pe- List of basic parameters of the eclipsing HMXBs analyzed in this work, where P orb : Orbital Period (days), M C : Mass of the companion (M ⊙ ), R C : Radius of the companion star (R ⊙ ), S C : Spectral type of the companion, e: Eccentricity of the HMXB orbit, a: Length of the semi major axis of the system (axsini [light-sec]) , Ṁw : Mass loss of the companion star (10 (Becker et al 1977), e3 (Reynolds, Bell & Hilditch 1992), e4 (Parkes, Murdin & Mason 1978), (Falanga et al 2015), e5 (Mukherjee et al 2006) , z2 Derived from total mass of the binary and the orbital period, taken from Coley, Corbet & Krimm (2015) riodicity longer than the orbital period known as superorbital period of 30.5 days (Lang et al 1981). The pulsation of the soft spectral component and the powerlaw component showed significant phase differences with the ROSAT, GINGA, ASCA, BeppoSAX and XMM-Newton and Suzaku observatories (Woo et al 1996;Paul & Kitamoto 2002;Naik & Paul 2004b;Beri & Paul 2017;Hung et al 2010). These indicate different origin of the soft and hard X-rays.…”

Section: Introductionmentioning

confidence: 99%

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X-Ray Reprocessing: Through the Eclipse Spectra of High-mass X-Ray Binaries with XMM-Newton

Aftab¹,

Paul²,

Kretschmar³

2019

ApJS

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The study of X-ray reprocessing is one of the key diagnostic tools to probe the environment in X-ray binary systems. One difficult aspect of studying X-ray reprocessing is the presence of much brighter primary radiation from the compact star together with the reprocessed radiation. In contrast for eclipsing systems, the X-rays we receive during eclipse are only those produced by reprocessing of the emission from the compact star by the surrounding medium. We report results from a spectral study of the X-ray emission during eclipse and outside eclipse (when available) in 9 high mass X-ray binaries (HMXBs) with XMM-Newton EPIC pn to investigate different aspects of the stellar wind in these HMXBs. During eclipse the continuum component of the spectrum is reduced by a factor of ∼8-237, but the count-rate for 6.4 keV Iron emission line or complex of Iron emission lines in HMXBs are reduced by a smaller factor leading to large equivalent widths of the Iron emission lines. This indicates a large size for the line emission region, comparable to or larger than the companion star in these HMXB systems. However there are significant system to system differences. 4U 1538−52, in spite of having a large absorption column density, shows a soft emission component with comparable flux during the eclipse and out-of-eclipse phases. Emission from Hydrogen-like Iron has been observed in LMC X-4 for the first time, in the out-of-eclipse phase in one of the observations. Overall, we find significant differences in the eclipse spectrum of different HMXBs and also in their eclipse spectra against out-of-eclipse spectra.

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“…where µ 30 ≡ µ/(10 30 G cm 3 ) andṀ 16 ≡Ṁ/(10 16 g s −1 ), v 8 ≡ v rel /(1000 km s −1 ). The stellar wind velocity in 4U 0114+65 is about v 8 ∼ 0.5−0.7 ( Ferrigno et al 2008;Beri & Paul 2017;Barnstedt et al 2008;Evangelista et al 2010;Hemphill et al 2016;Doroshenko et al 2017;Şahiner et al 2012), and accreting magnetar candidates (green squares; this work; Wang 2013). The values ofṖ/P(s −1 ) are represented in absolute values.…”

Section: Discussionmentioning

confidence: 77%

XMM-Newtonspectroscopy of the accreting magnetar candidate 4U0114+65

Sanjurjo-Ferrrín

Torrejón

Постнов

et al. 2017

A&A

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Aims. 4U0114+65 is one of the slowest known X-ray pulsars. We present an analysis of a pointed observation by the XMM-Newton X-ray telescope in order to study the nature of the X-ray pulsations and the accretion process, and to diagnose the physical properties of the donor's stellar wind. Methods. We analysed the energy-resolved light curve and the time-resolved X-ray spectra provided by the EPIC cameras on board XMM-Newton. We also analysed the first high-resolution spectrum of this source provided by the Reflection Grating Spectrometer. Results. An X-ray pulse of 9350 ± 160 s was measured. Comparison with previous measurements confirms the secular spin up of this source. We successfully fit the pulse-phase-resolved spectra with Comptonisation models. These models imply a very small (r ∼ 3 km) and hot (kT ∼ 2−3 keV) emitting region and therefore point to a hot spot over the neutron star (NS) surface as the most reliable explanation for the X-ray pulse. The long NS spin period, the spin-up rate, and persistent X-ray emission can be explained within the theory of quasi-spherical settling accretion, which may indicate that the magnetic field is in the magnetar range. Thus, 4U 0114+65 could be a wind-accreting magnetar. We also observed two episodes of low luminosity. The first was only observed in the low-energy light curve and can be explained as an absorption by a large over-dense structure in the wind of the B1 supergiant donor. The second episode, which was deeper and affected all energies, may be due to temporal cessation of accretion onto one magnetic pole caused by non-spherical matter capture from the structured stellar wind. The light curve displays two types of dips that are clearly seen during the high-flux intervals. The short dips, with durations of tens of seconds, are produced through absorption by wind clumps. The long dips, in turn, seem to be associated with the rarefied interclump medium. From the analysis of the X-ray spectra, we found evidence of emission lines in the X-ray photoionised wind of the B1Ia donor. The Fe Kα line was found to be highly variable and much weaker than in other X-ray binaries with supergiant donors. The degree of wind clumping, measured through the covering fraction, was found to be much lower than in supergiant donor stars with earlier spectral types. Conclusions. The XMM-Newton spectroscopy provided further support for the magnetar nature of the neutron star in 4U0114+65. The light curve presents dips that can be associated with clumps and the interclump medium in the stellar wind of the mass donor.

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Post-flare formation of the accretion stream and a dip in pulse profiles of LMC X–4

Cited by 13 publications

References 32 publications

Discovery of Pulsation Dropout and Turn-on during the High State of the Accreting X-Ray Pulsar LMC X-4

Discovery of Pulsation Dropout and Turn-on during the High State of the Accreting X-Ray Pulsar LMC X-4

X-Ray Reprocessing: Through the Eclipse Spectra of High-mass X-Ray Binaries with XMM-Newton

XMM-Newtonspectroscopy of the accreting magnetar candidate 4U0114+65

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