<i>SUZAKU</i>X-RAY SPECTRA AND PULSE PROFILE VARIATIONS DURING THE SUPERORBITAL CYCLE OF LMC X-4

Hung, Li‐Wei; Hickox, Ryan C.; Boroson, Bram; Vrtilek, S. D.

doi:10.1088/0004-637x/720/2/1202

Cited by 23 publications

(45 citation statements)

References 48 publications

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“…The dip feature is seen only at energies above 2 keV. These pulse profile shapes are quite similar to the previously reported profiles created using observations made with Ginga, RXTE, ASCA, BeppoSAX and Suzaku (Levine et al, 1991(Levine et al, , 2000Naik & Paul, 2004;Hung et al, 2010). Similar dips were also observed in the pulse profiles during the persistent emission, created using data from the other two PCA observations.…”

Section: Energy-resolved Profilessupporting

confidence: 86%

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

Beri

Paul

2017

New Astronomy

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We report here a pulse profile evolution study of an accreting X-ray pulsar LMC X-4 during and after the large X-ray flares using data from the two observatories XMM-Newton and RXTE. During the flares, the pulse profiles were found to have a significant phase offset in the range of 0.2-0.5 compared to the pulse profiles immediately before or after the flare. Investigating the pulse profiles for about 10 5 seconds after the flares, it was found that it takes about 2000-4000 seconds for the modified accretion column to return to its normal structure and formation of an accretion stream that causes a dip in the pulse profile of LMC X-4. We have also carried out pulse phase resolved spectroscopy of LMC X-4 in narrow phase bins using data from EPIC-pn and spectroscopically confirmed the pulsating nature of the soft spectral component, having a pulse fraction and phase different from that of the power-law component.

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Section: Energy-resolved Profilessupporting

confidence: 86%

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

Beri

Paul

2017

New Astronomy

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“…The X-ray broadband (0.5-50 keV) spectral properties, i.e., the hard spectrum ( 1 G~) at lower energies with a cutoff around 15-20 keV, are more consistent with Galactic X-ray pulsars (e.g., Hung et al 2010;Camero-Arranz et al 2012;Fürst et al 2013) than with BH binaries and neutron star binaries with weak magnetic fields (Z-sources and atoll sources). Our observations suggest that there is a soft X-ray excess in this system, and the soft excess has also been seen in several accreting pulsars (e.g., Nagase 2002; Hickox et al 2004).…”

Section: Discussionmentioning

confidence: 83%

“…Assuming that this object is located within M31, the corresponding luminosity is 4.0×10 38 erg s −1 in the 0.5-50 keV band. The brightest known accreting X-ray pulsars typically achieve similar luminosities (e.g., LMC X-4, Hung et al 2010; SMC X-1, Neilsen et al 2004; RX J0059.2-7138, Hughes 1994; M82 X-2, NGC7793 P13, and NGC 5907 ULX1 for exceptionally bright examples; Bachetti et al 2014;Fürst et al 2016;Israel et al 2016Israel et al , 2017.…”

Section: Nustar and Swift Spectral Analysismentioning

confidence: 99%

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

Yukita

Ptak

Hornschemeier

et al. 2017

ApJ

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We report the identification of a bright hard X-ray source dominating the M31 bulge above 25 keV from a simultaneous NuSTAR-Swift observation. We find that this source is the counterpart to Swift J0042.6+4112, which was previously detected in the Swift BAT All-sky Hard X-ray Survey. This Swift BAT source had been suggested to be the combined emission from a number of point sources; our new observations have identified a single X-ray source from 0.5 to 50 keV as the counterpart for the first time. In the 0.5-10 keV band, the source had been classified as an X-ray Binary candidate in various Chandra and XMM-Newton studies; however, since it was not clearly associated with Swift J0042.6+4112, the previous E<10 keV observations did not generate much attention. This source has a spectrum with a soft X-ray excess (kT ∼ 0.2 keV) plus a hard spectrum with a power law of 1 G~and a cutoff around 15-20 keV, typical of the spectral characteristics of accreting pulsars. Unfortunately, any potential pulsation was undetected in the NuSTAR data, possibly due to insufficient photon statistics. The existing deep HST images exclude high-mass (>3 M  ) donors at the location of this source. The best interpretation for the nature of this source is an X-ray pulsar with an intermediate-mass (<3 M  ) companion or a symbiotic X-ray binary. We discuss other possibilities in more detail.

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“…Bouret et al 2003). We tested three LMC and SMC binaries, LMC X-1, LMC X-4, and SMC X-1, with parameters taken from literature (Orosz et al 2009;Hung et al 2010;Rawls et al 2011;Li & Li 2014). In all these cases, the corresponding stellar parameters lie in a forbidden zone, indicating that the wind of these stars is inhibited in the direction toward the companion and the X-rays most likely originate in the Roche lobe overflow.…”

Section: X-ray Binaries In the Magellanic Cloudsmentioning

confidence: 99%

X-ray irradiation of the winds in binaries with massive components

Krtička

Kubát

Krtičková

2015

A&A

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Context. Binaries with hot massive components are strong X-ray sources. Besides the intrinsic X-ray emission of individual binary members originating in their winds, X-ray emission stems from the accretion on the compact companion or from wind collision. Since hot star winds are driven by the light absorption in the lines of heavier elements, wind acceleration is sensitive to the ionization state. Therefore, the over-ionization induced by external X-ray source strongly influences the winds of individual components. Aims. We studied the effect of external X-ray irradiation on hot star winds. Methods. We used our kinetic equilibrium (NLTE) wind models to estimate the influence of external X-ray ionization for different X-ray luminosities and source distances. The models are calculated for parameters typical of O stars.Results. The influence of X-rays is given by the X-ray luminosity, by the optical depth between a given point and the X-ray source, and by a distance to the X-ray source. Therefore, the results can be interpreted in the diagrams of X-ray luminosity vs. the optical depth parameter. X-rays are negligible in binaries with low X-ray luminosities or at large distances from the X-ray source. The influence of X-rays is stronger for higher X-ray luminosities and in closer proximity of the X-ray source. There is a forbidden area with high X-ray luminosities and low optical depth parameters, where the X-ray ionization leads to wind inhibition. There is excellent agreement between the positions of observed stars in these diagrams and our predictions. All wind-powered high-mass X-ray binary primaries lie outside the forbidden area. Many of them lie close to the border of the forbidden area, indicating that their X-ray luminosities are self-regulated. We discuss the implications of our work for other binary types. Conclusions. X-rays have a strong effect on the winds in binaries with hot components. The magnitude of the influence of X-rays can be estimated from the position of a star in the diagram of X-ray luminosity vs. the optical depth parameter.

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SUZAKUX-RAY SPECTRA AND PULSE PROFILE VARIATIONS DURING THE SUPERORBITAL CYCLE OF LMC X-4

Cited by 23 publications

References 48 publications

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

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

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

X-ray irradiation of the winds in binaries with massive components

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