Variability of the X-ray sources in the Magellanic clouds

Tuohy, I.; Rapley, C. G.

doi:10.1086/181814

Cited by 14 publications

(4 citation statements)

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“…Extended periods of very low X-ray flux of the uneclipsed source have been reported in observations with Uhuru (Schreier et al 1972), Copernicus (Tuohy & Rapley 1975), Ariel V (Cooke 1978), andCOS-B (Bonnet-Bidaud &van der Klis 1981). An extended period of exceptionally high flux, beginning in 1970 September and lasting ∼ 100 days, was reported from a three-year record of observations by the Vela 5B monitor (Whitlock & Lochner 1994).…”

Section: Introductionmentioning

confidence: 73%

Quasi‐periodic Occultation by a Precessing Accretion Disk and Other Variabilities of SMC X‐1

Wojdowski

Clark

Levine

et al. 1998

ApJ

154

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We have investigated the variability of the binary X-ray pulsar, SMC X-1, in data from several X-ray observatories. We confirm the ∼ 60-day cyclic variation of the X-ray flux in the long-term monitoring data from the RXTE and CGRO observatories. X-ray light curves and spectra from the ROSAT , Ginga, and ASCA observatories show that the uneclipsed flux varies by as much as a factor of twenty between a high-flux state when 0.71 second pulses are present and a low-flux state when pulses are absent. In contrast, during eclipses when the X-rays consist of radiation scattered from circumsource matter, the fluxes and spectra in the high and low states are approximately the same. These observations prove that the low state of SMC X-1 is not caused by a reduction in the intrinsic luminosity of the source, or a spectral redistribution thereof, but rather by a quasi-periodic blockage of the line of sight, most likely by a precessing tilted accretion disk. In each of two observations in the midst of low states a brief increase in the X-ray flux and reappearance of 0.71 second pulses occurred near orbital phase 0.2. A similar brief flux increase near orbital phase 0.2 was observed during a low-state observation that did not have sufficient time resolution to detect 0.71 second pulses. These brief increases result from an opening of the line of sight to the pulsar that may be caused by wobble in the precessing accretion disk. The records of spin up of the neutron star and decay of the binary orbit are extended during 1991-1996 by pulse-timing analysis of ROSAT , ASCA, and RXTE PCA data. The pulse profiles in various energy ranges from 0.1 to > 21 keV are well represented as a combination of a pencil beam and a fan beam. Finally, there is a marked difference between the power spectra of random fluctuations in the high-state data from the RXTE PCA below and above 3.4 keV. In the higher energy range the spectrum has a sharp break at 3.3 Hz, with fitted power law indices of 0.45 and 1.76 below and above the break. No break is evident in the power spectrum below 3.4 keV, and the fitted power law index is 0.51. In both spectra there is a positive deviation from the fitted power law around 0.06 Hz that may be QPO.

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Section: Introductionmentioning

confidence: 73%

Quasi‐periodic Occultation by a Precessing Accretion Disk and Other Variabilities of SMC X‐1

Wojdowski

Clark

Levine

et al. 1998

ApJ

154

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“… References: (1) Wojdowski et al (1998); (2) Schreier et al (1972); (3) Tuohy & Rapley (1975); (4) Primini (1977); (5) Davison (1977); (6) Bonnet‐Bidaud & van der Klis (1981); (7) Levine et al (1993); (8) this work. …”

Section: Timing Analysismentioning

confidence: 99%

Analysis ofRXTE-PCA Observations of SMC X-1

İnam

Baykal

Beklen

2010

Monthly Notices of the Royal Astronomical Society

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We present timing and spectral analysis of Rossi X‐ray Timing Explorer‐Proportional Counter Array observations of SMC X‐1 between 1996 January and 2003 December. From observations around 1996 August 30 with a time‐span of ∼6 d, we obtain a precise timing solution for the source and resolve the eccentricity as 0.00089(6). We find an orbital decay rate of which is close to the previous results. Using our timing analysis and the previous studies, we construct a ∼30 yr long pulse period history of the source. We show that frequency derivative shows long‐ (i.e. more than a few years) and short‐term (i.e. order of days) fluctuations. From the spectral analysis, we found that all spectral parameters except Hydrogen column density showed no significant variation with time and X‐ray flux. Hydrogen column density is found to be higher as X‐ray flux gets lower. This may be due to the increase in soft absorption when the pulsar is partially obscured as in Her X‐1 or may just be an artefact of the tail of a soft excess in energy spectrum.

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“…Out of these systems only one is a sgXRB, source SMC X-1 (Webster et al 1972), which is the only persistent accreting X-ray pulsar (Pspin ∼ 0.71 s; Lucke et al 1976) in the SMC fed through RLOF. This system has a B0 supergiant companion (Webster et al 1972) with an orbital period of 3.89 days (Tuohy & Rapley 1975) and an X-ray luminosity of ∼ 9.5 × 10 37 erg s −1 in the 0.2-12.0 keV energy band (e.g. XMMSL1; Saxton et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Optical spectra of five new Be/X-ray binaries in the Small Magellanic Cloud and the link of the supergiant B[e] star LHA 115-S 18 with an X-ray source

Maravelias¹,

Zezas²,

Antoniou³

et al. 2014

Monthly Notices of the Royal Astronomical Society

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The Small Magellanic Cloud (SMC) is well known to harbor a large number of High-Mass X-ray Binaries (HMXBs). The identification of their optical counterparts provides information on the nature of the donor stars and can help to constrain the parameters of these systems and their evolution. We obtained optical spectra for a number of HMXBs identified in previous Chandra and XMM-Newton surveys of the SMC using the AAOmega/2dF fiber-fed spectrograph at the Anglo-Australian Telescope. We find 5 new Be/X-ray binaries (BeXRBs; including a tentative one), by identifying the spectral type of their optical counterparts, and we confirm the spectral classification of an additional 15 known BeXRBs. We compared the spectral types, orbital periods, and eccentricities of the BeXRB populations in the SMC and the Milky Way and we find marginal evidence for difference between the spectral type distributions, but no statistically significant differences for the orbital periods and the eccentricities. Moreover, our search revealed that the well known supergiant B[e] star LHA 115-S 18 (or AzV 154) is associated with the weak X-ray source CXOU J005409.57-724143.5. We provide evidence that the supergiant star LHA 115-S 18 is the optical counterpart of the X-ray source, and we discuss different possibilities of the origin of its low X-ray luminosity (Lx ∼ 4 × 10 33 erg s −1 ).

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Variability of the X-ray sources in the Magellanic clouds

Cited by 14 publications

References 0 publications

Quasi‐periodic Occultation by a Precessing Accretion Disk and Other Variabilities of SMC X‐1

Quasi‐periodic Occultation by a Precessing Accretion Disk and Other Variabilities of SMC X‐1

Analysis ofRXTE-PCA Observations of SMC X-1

Optical spectra of five new Be/X-ray binaries in the Small Magellanic Cloud and the link of the supergiant B[e] star LHA 115-S 18 with an X-ray source

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