Implications of X-Ray Line Variations for 4u1822–371

Ji, Li; Schulz, Norbert S.; Nowak, Michael A.; Canizares, C. R.

doi:10.1088/0004-637x/729/2/102

Cited by 13 publications

(34 citation statements)

References 20 publications

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“…The best-fit value of the equivalent hydrogen column associated with neutral interstellar matter, N H ∼ 0.16 × 10 22 cm −2 , is similar to that obtained by Iaria et al (2001) (i.e. 0.11 +0.3 −0.5 × 10 22 cm −2 ) and to the value of ∼0.16 × 10 22 cm −2 obtained by Ji et al (2011), who fitted the HETGS spectrum of X1822-371 with a power-law component absorbed by local neutral matter. The values of equivalent hydrogen column associated with local neutral matter, N H pc , obtained by fitting the XMM and Chandra averaged spectra are compatible with each other and consistent with the value reported by Iaria et al (2001) (about 4.4 × 10 22 cm −2 ) and by Ji et al (2011) (between 5.4 and 6.3 × 10 22 cm −2 ).…”

Section: Discussionsupporting

confidence: 89%

“…0.11 +0.3 −0.5 × 10 22 cm −2 ) and to the value of ∼0.16 × 10 22 cm −2 obtained by Ji et al (2011), who fitted the HETGS spectrum of X1822-371 with a power-law component absorbed by local neutral matter. The values of equivalent hydrogen column associated with local neutral matter, N H pc , obtained by fitting the XMM and Chandra averaged spectra are compatible with each other and consistent with the value reported by Iaria et al (2001) (about 4.4 × 10 22 cm −2 ) and by Ji et al (2011) (between 5.4 and 6.3 × 10 22 cm −2 ). Finally, we found that the covered X-ray emitting surface is about 60-65%.…”

Section: Discussionsupporting

confidence: 62%

“…The photo-ionised plasma where the lines originate was consistent with ionisation parameters ξ > 100. Ji et al (2011), combining the disc size and reasonable assumptions for the plasma density (between 10 12 and 10 14 cm −3 ), suggested that the illuminating disc luminosities are more than an order of magnitude higher than what is actually observed and concluded that the central emitting X-ray source is not directly observed.…”

Section: Introductionmentioning

confidence: 98%

“…Recently Ji et al (2011), analysing Chandra data sets also used for this paper, measured the Doppler velocities of several lines. They divided the observation into 40 intervals and moved a phase window with a width of 0.16 in phase across the 40 intervals, so that each interval had a phase shift of 0.025 from the previous, and therefore the intervals partially overlap in phase.…”

Section: Introductionmentioning

confidence: 99%

“…They divided the observation into 40 intervals and moved a phase window with a width of 0.16 in phase across the 40 intervals, so that each interval had a phase shift of 0.025 from the previous, and therefore the intervals partially overlap in phase. Ji et al (2011), measuring the Doppler velocity modulation of several ionised lines, inferred that the observed photo-ionised emission lines originate from a confined region in the outer edge of the accretion disc near the hot spot. The photo-ionised plasma where the lines originate was consistent with ionisation parameters ξ > 100.…”

Section: Introductionmentioning

confidence: 99%

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X-ray spectroscopy of the ADC source X1822-371 withChandraandXMM-Newton

Iaria

Salvo

D’Aí

et al. 2012

A&A

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Context. The eclipsing low-mass X-ray binary X1822-371 is the prototype of the accretion disc corona (ADC) sources. Its inclination angle ( 82.5 • ) is high enough that flux from the neutron star is blocked by the edge-on accretion disc. Because the neutron star's direct emission is hidden, its ADC emission is visible. The physical properties of the ADC in X1822-371 have been widely studied, but are still debated in literature. In light of the recent literature and of the results reported in this work we show that the ADC is optically thin. Aims. We analyse two Chandra observations and one XMM-Newton observation to study the discrete features in this source and their variation as a function of the orbital phase, deriving constraints on the temperature, density, and location of the plasma responsible for emission lines. Methods. The HETGS and XMM/Epic-pn observed X1822-371 for 140 and 50 ks, respectively. We extracted an averaged spectrum and five spectra from five selected orbital-phase intervals that are 0.04-0.25, 0.25-0.50, 0.50-0.75, 0.75-0.95, and, finally, 0.95-1.04; the orbital phase zero corresponds to the eclipse time. All spectra cover the energy band between 0.35 and 12 keV. Results. We confirm the presence of local neutral matter that partially covers the X-ray emitting region; the equivalent hydrogen column is 5 × 10 22 cm −2 and the covered fraction is about 60-65%. We identify several emission lines of He-like and H-like ions, and a prominent fluorescence iron line associated with a blending of Fe i-Fe xv resonant transitions. The transitions of He-like ions show that the intercombination dominates over the forbidden and resonance lines. The line fluxes are the highest during the orbital phases between 0.04 and 0.75. Conclusions. We discuss the presence of an extended, optically thin corona with optical depth of about 0.01 that scatters the X-ray photons from the innermost region into the line of sight. The photoionised plasma producing the O viii, Ne ix, Ne x, Mg xi, Mg xii, Si xiii, and Si xiv lines is placed in the bulge at the outer radius of the disc distant from the central source of 6 × 10 10 cm. The O vii and the fluorescence iron line are probably produced in the photoionised surface of the disc at inner radii. Finally, we suggest that the observed local neutral matter is the matter transferred by the companion star that was expelled from the system by the X-ray radiation pressure, which in turn originated in the accretion process onto the neutron star.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionsupporting

confidence: 62%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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X-ray spectroscopy of the ADC source X1822-371 withChandraandXMM-Newton

Iaria

Salvo

D’Aí

et al. 2012

A&A

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Detailed study of the X-ray and optical/UV orbital ephemeris of X1822–371

Iaria

Salvo

Burderi

et al. 2011

A&A

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Aims. Recent studies of the optical/UV and X-ray ephemerides of X1822-371 have found some discrepancies in the value of the orbital period derivative. Because of the importance of this value in constraining the system evolution, we comprehensively analyse all the available optical/UV/X eclipse times of this source to investigate the origin of these discrepancies. Methods. We collected all previously published X-ray eclipse times from 1977 to 2008, to which we added the eclipse time observed by Suzaku in 2006. This point is very important to cover the time gap between the last RXTE eclipse time (taken in 2003) and the most recent Chandra eclipse time (taken in 2008). Similarly we collected the optical/UV eclipse arrival times covering the period from 1979 to 2006, adding a further eclipse time taken on 1978 and updating previous optical/UV ephemeris. We compared the X-ray and the optical/UV ephemeris, and finally derived a new ephemeris of the source by combining the eclipse arrival times in the X-ray and optical/UV bands. Results. The X-ray eclipse time delays calculated with respect to a constant orbital period model display a clear parabolic trend, confirming that the orbital period of this source constantly increases at a rate ofṖ orb = 1.51(7) × 10 −10 s/s. Combining the X-ray and the optical/UV data sets, we find thatṖ orb = 1.59(9) × 10 −10 s/s, which is compatible with the X-ray orbital solution. We also investigate the possible presence of a delay of the optical/UV eclipse with respect to the X-ray eclipse, finding that this delay may not be constant in time. In particular, this variation is compatible with a sinusoidal modulation of the optical/UV eclipse arrival times with respect to the long-term parabolic trend. In this case, the optical/UV eclipse should lag the X-ray eclipse and the time-lag oscillate about an average value. Conclusions. We confirm that the orbital period derivative is three orders of magnitude larger than expected from conservative mass transfer driven by magnetic braking and gravitational radiation.

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Phase-resolved optical and X-ray spectroscopy of low-mass X-ray binary X1822–371

Somero

Hakala

Muhli

et al. 2012

A&A

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Context. X1822-371 is the prototypical accretion disc corona X-ray source, a low-mass X-ray binary viewed at very high inclination, thereby allowing the disc structure and extended disc coronal regions to be visible. As the brightest (closest) such source, X1822-371 is ideal for studying the shape and edge structure of an accretion disc, and comparing with detailed models. Aims. We study the structure of the accretion disc in X1822-371 by modelling the phase-resolved spectra both in optical and X-ray regime. Methods. We analyse high time resolution optical ESO/VLT spectra of X1822-371 to study the variability in the emission line profiles. In addition, we use data from XMM-Newton space observatory to study phase-resolved as well as high resolution X-ray spectra. We apply the Doppler tomography technique to reconstruct a map of the optical emission distribution in the system. We fit multi-component models to the X-ray spectra. Results. We find that our results from both the optical and X-ray analysis can be explained with a model where the accretion disc has a thick rim in the region where the accretion stream impacts the disc. The behaviour of the Hβ line complex implies that some of the accreting matter creates an outburst around the accretion stream impact location and that the resulting outflow of matter moves both away from the accretion disc and towards the centre of the disc. Such behaviour can be explained by an almost isotropic outflow of matter from the accretion stream impact region. The optical emission lines of He ii λ4686 and 5411 show double peaked profiles, typical for an accretion disc at high inclination. However, their velocities are slower than expected for an accretion disc in a system like X1822-371. This, combined with the fact that the He ii emission lines do not get eclipsed during the partial eclipse in the continuum, suggests that the line emission does not originate in the orbital plane and is more likely to come from above the accretion disc, for example the accretion disc wind.

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Implications of X-Ray Line Variations for 4u1822–371

Cited by 13 publications

References 20 publications

X-ray spectroscopy of the ADC source X1822-371 withChandraandXMM-Newton

X-ray spectroscopy of the ADC source X1822-371 withChandraandXMM-Newton

Detailed study of the X-ray and optical/UV orbital ephemeris of X1822–371

Phase-resolved optical and X-ray spectroscopy of low-mass X-ray binary X1822–371

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