ASCA observations of OAO 1657-415 and its dust-scattered X-ray halo

Audley, M. D.; Nagase, F.; Mitsuda, Kazuhisa; Angelini, L.; Kelley, R. L.

doi:10.1111/j.1365-2966.2006.10003.x

Cited by 36 publications

(60 citation statements)

References 23 publications

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“…OAO 1657-415 was subsequently found to exist in an eclipsing ∼10.4 day binary orbit (Chakrabarty et al 1993). Limitations imposed by the uncertain spectral classification of the mass donor complicate estimates of the distance and hence bolometric X-ray luminosity, although Audley et al (2006) report a distance of 7.1 ± 1.3 kpc based on observations of the dust-scattered X-ray halo. Nevertheless, the X-ray properties OAO1657-415 mark it as highly atypical.…”

Section: Oao 1657-415mentioning

confidence: 99%

Spectral classification of the mass donors in the high-mass X-ray binaries EXO 1722-363 and OAO 1657-415

Mason

Clark

Norton

et al. 2009

A&A

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Aims. We report near-infrared (NIR) observations of the mass donors of the eclipsing high-mass X-ray binary (HMXB) systems EXO 1722-363 and OAO 1657-415 in order to derive their accurate spectral classifications. Methods. ESO/VLT observations of the targets with the NIR spectrometer ISAAC were compared with several published NIR spectral atlases of O and B supergiants, an identification of each object's spectral characteristics was made, enabling the refinement of spectral classification of the mass donors. Results. We determined that EXO 1722-363 was of spectral type B0-B1Ia, positioned at a distance 8.0 +2.5 −2.0 kpc with a progenitor mass in the range 30-40 M . Luminosity calculations imply that L X ∼ 10 35 -10 37 erg s −1 for this distance range. We conclude that EXO 1722-363 shares many of the properties associated with other X-ray binary B-type supergiant donors. We found that OAO 1657-415 correlates closely with the spectra of a class of transitional objects, the Ofpe/WNL stars, an intermediate evolutionary stage between massive O type stars leaving the main sequence and evolving into Wolf-Rayets. Due to the wide range in luminosity displayed by Ofpe/WNL stars, (log(L/L ) ∼ 5.3-6.2) distance determinations are problematic. For OAO 1657-415 we report a distance of 4.4 ≤ d ≤ 12 kpc, implying an X-ray luminosity of 1.5 × 10 36 ≤ L X ≤ 10 37 erg s −1 . We have used our new classification of OAO 1657-415 to explain the physical processes responsible for its unique position within the Corbet diagram.Ofpe/WNL stars demonstrate a high rate of mass-loss through a dense stellar wind combined with a low terminal velocity. This combination of wind properties leads to a high accretion rate and transfer of angular momentum to the neutron star in this system. We believe this in turn leads to a smaller instantaneous equilibrium spin period with respect to normal OB supergiants.

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Section: Oao 1657-415mentioning

confidence: 99%

Spectral classification of the mass donors in the high-mass X-ray binaries EXO 1722-363 and OAO 1657-415

Mason

Clark

Norton

et al. 2009

A&A

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“…Given a dust distribution, variability in the X-ray halo can be used to geometrically derive estimates of the distances to X-ray sources based on the time delays of the photons scattered along the line of sight (Trümper & Schönfelder 1973). This method has been applied in a number of cases (e.g., Predehl et al 2000; Thompson et al 2006;Audley et al 2006;Xiang et al 2007). The goal of this paper is to estimate the dust distribution and distance to the eclipsing high-mass X-ray binary (HMXB) Cen X-3 using measurements of its dust-scattered halo with the Chandra X-Ray Observatory.…”

Section: Introductionmentioning

confidence: 99%

The X-Ray Halo of Cen X-3

Thompson

Rothschild

2009

ApJ

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Using two Chandra observations, we have derived estimates of the dust distribution and distance to the eclipsing high-mass X-ray binary Cen X-3 using the energy-resolved dust-scattered X-ray halo. By comparing the observed X-ray halos in 200 eV bands from 2-5 keV to the halo profiles predicted by the Weingartner & Draine interstellar grain model, we find that the vast majority (≈ 70%) of the dust along the line of sight to the system is located within about 300 pc of the Sun, although the halo measurements are insensitive to dust very close to the source. One of the Chandra observations occurred during an egress from eclipse as the pulsar emerged from behind the mass-donating primary. By comparing model halo light curves during this transition to the halo measurements, a source distance of 5.7 ± 1.5 kpc (68% confidence level) is estimated, although we find this result depends on the distribution of dust on very small scales. Nevertheless, this value is marginally inconsistent with the commonly accepted distance to Cen X-3 of 8 kpc. We also find that the energy scaling of the scattering optical depth predicted by the Weingartner & Draine interstellar grain model does not accurately represent the results determined by X-ray halo studies of Cen X-3. Relative to the model, there appears to be less scattering at low energies or more scattering at high energies in Cen X-3.

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“…ASCA (Audley et al 2006), Chandra/HETGS , RXTE (Baykal 2000), BeppoSAX (Orlandini et al 1999) and Ginga (Kamata et al 1990). …”

Section: Introductionmentioning

confidence: 99%

INTEGRAL observations of the variability of OAO 1657-415

Barnstedt¹,

Staubert²,

Santangelo³

et al. 2008

A&A

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Context. The Galactic Plane Scan (GPS) was one of the core observation programmes of the INTEGRAL satellite. The highly variable accreting pulsar OAO 1657−415 was frequently observed within the GPS. Aims. We investigate the spectral and timing properties of OAO 1657−415 and their variability on short and long time scales in the energy range 6−160 keV. Methods. Using standard extraction tools and custom software for extracting INTEGRAL data we analysed energy-resolved light curves with a time resolution of one second -mainly data of the ISGRI instrument. We also analysed phase-averaged broad band spectra -including JEM-X spectra -and pulse-phase resolved spectra of ISGRI. Results. During the time covered by the INTEGRAL observations, the pulse period evolution shows an initial spin-down, which is followed by an equally strong spin-up. In combining our results with historical pulse period measurements (correcting them for orbital variation) and with stretches of continuous observations by BATSE, we find that the long-term period evolution is characterised by a long-term spin-up overlayed by sets of relative spin-down/spin-up episodes, which appear to repeat quasi-periodically on a 4.8 yr time scale. We measure an updated local ephemeris and confirm the previously determined orbital period with an improved accuracy. The spectra clearly change with pulse phase. The spectrum measured during the main peak of the pulse profile is particularly hard. We do not find any evidence of a cyclotron line, wether in the phase-averaged spectrum or in phase-resolved spectra.

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ASCA observations of OAO 1657-415 and its dust-scattered X-ray halo

Cited by 36 publications

References 23 publications

Spectral classification of the mass donors in the high-mass X-ray binaries EXO 1722-363 and OAO 1657-415

Spectral classification of the mass donors in the high-mass X-ray binaries EXO 1722-363 and OAO 1657-415

The X-Ray Halo of Cen X-3

INTEGRAL observations of the variability of OAO 1657-415

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