<i>Chandra</i>LETGS Spectroscopy of the Quasar MR 2251−178 and Its Warm Absorber

Ramírez, José Manuel Ricardo; Komossa, Stefanie; Burwitz, V.; Mathur, S.

doi:10.1086/587949

Cited by 14 publications

(7 citation statements)

References 35 publications

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“…In contrast there appears to be no change in the higher ionization components 2 and 3, within the errors. Note that this behavior is also consistent with a December 2002 (80 ks) Chandra LETG observation (not analyzed here), which was at about a 35% lower flux than the 2002 HETG observation, but observed the low ionization absorber to have an even lower ionization, of log(ξ/erg cm s −1 ) = 0.63 ± 0.06 (Ramírez et al 2008).…”

Section: Variability Of the X-ray Absorptionsupporting

confidence: 90%

A High Resolution View of the Warm Absorber in the Quasar MR 2251-178

Reeves

Porquet

Braito

et al. 2013

ApJ

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High resolution X-ray spectroscopy of the warm absorber in the nearby quasar, MR 2251-178 (z = 0.06398) is presented. The observations were carried out in 2011 using the Chandra High Energy Transmission Grating and the XMM-Newton Reflection Grating Spectrometer, with net exposure times of approximately 400 ks each. A multitude of absorption lines from C to Fe are detected, revealing at least 3 warm absorbing components ranging in ionization parameter from log(ξ/erg cm s −1 ) = 1 − 3 and with outflow velocities ∼ < 500 km s −1 . The lowest ionization absorber appears to vary between the Chandra and XMM-Newton observations, which implies a radial distance of between 9 − 17 pc from the black hole. The soft X-ray warm absorbers likely contribute a negligible < 0.01% of the bolometric output in terms of their kinetic power. Several broad soft X-ray emission lines are strongly detected, most notably from He-like Oxygen, with FWHM velocity widths of up to 10000 km s −1 , consistent with an origin from Broad Line Region (BLR) clouds. In addition to the warm absorber, gas partially covering the line of sight to the quasar appears to be present, of typical column density N H = 10 23 cm −2 . We suggest that the partial covering absorber may arise from the same BLR clouds responsible for the broad soft X-ray emission lines. Finally the presence of a highly ionised outflow in the iron K band from both 2002 and 2011 Chandra HETG observations appears to be confirmed, which has an outflow velocity of −15600 ± 2400 km s −1 . However a partial covering origin of the iron K band absorption cannot be excluded, resulting from low ionization material with little or no outflow velocity.

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Section: Variability Of the X-ray Absorptionsupporting

confidence: 90%

A High Resolution View of the Warm Absorber in the Quasar MR 2251-178

Reeves

Porquet

Braito

et al. 2013

ApJ

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“…For a solar sulphur/hydrogen abundance ratio of 2.14 × 10 −5 (Grevesse & Sauval 1998), this corresponds to a hydrogen column of N H = 8.9 +1.4 −3.7 × 10 21 cm −2 , which is similar to the column densities reported previously for this source (i.e. Orr et al 2001; Kaspi et al 2004; Gibson et al 2005, Ramìrez et al 2008). The net outflow velocity of this absorber is v out = 6300 +5100 −4200 km s −1 (0.021 +0.017 −0.014 c), which is consistent with that found when fitting simple Gaussians.…”

Section: Self‐consistent Modellingsupporting

confidence: 86%

“…= 1111.1/340). The power‐law component has a photon index of Γ= 1.67 ± 0.01 and is absorbed by N H = 1.1 × 10 21 cm −2 , which is similar to that found by Ramìrez et al (2008) for the lowly ionized absorber in the Chandra , Low Energy Transmission Grating (LETG) observation of this source. The accretion disc blackbody used to parametrize the soft excess has a temperature kT = 62 +1 −3 eV.…”

Section: Broad‐band X‐ray Spectral Analysissupporting

confidence: 79%

A broad-band X-ray view of the warm absorber in radio-quiet quasar MR 2251−178

Gofford¹,

Reeves²,

Turner³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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We present the analysis of a new broad-band X-ray spectrum (0.6-180.0 keV) of the radioquiet quasar MR 2251−178 which uses both Suzaku and Swift/Burst Alert Telescope data. In accordance with previous observations, we find that the general continuum can be well described by a power law with = 1.6 and an apparent soft excess below 1 keV. Warm absorption is clearly present, and absorption lines due to the Fe unresolved transition array, Fe L (Fe XXIII-XXIV), S XV and S XVI are detected below 3 keV. At higher energies, Fe K absorption from Fe XXV-XXVI is detected and a relatively weak (EW = 25 +12 −8 eV) narrow Fe Kα emission line is observed (E = 6.44 ± 0.04 keV) which is well modelled by the presence of a mildly ionized (ξ 30) reflection component with a low reflection fraction (R < 0.2). At least five ionized absorption components with 10 20 N H 10 23 cm −2 and 0 log ξ /erg cm s −1 4 are required to achieve an adequate spectral fit. Alternatively, we show that the continuum can also be fit if a ∼ 2.0 power law is absorbed by a column of N H ∼ 10 23 cm −2 which covers ∼30 per cent of the source flux. Independent of which continuum model is adopted, the Fe L and Fe XXV Heα lines are well fit by a single absorber outflowing with v out ∼ 0.14c. Such an outflow/disc-wind is likely to be substantially clumped (b ∼ 10 −3 ) in order to not vastly exceed the likely accretion rate of the source.

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“…Narrow absorption Kα and Kβ lines of N VI have been identified in the warm absorber of the MR 2251-178 quasar, which point to a complex velocity field with an outflow of ionized material (Ramírez et al 2008). K-shell absorption by Li-like N V, which has prominent UV lines, or by lower charge states at wavelengths λ > 29 Å is difficult to detect due to the reduced sensitivity of current X-ray instruments towards these longer wavelengths.…”

Section: Introductionmentioning

confidence: 99%

Nitrogen K-Shell Photoabsorption

Garcia

Kallman

Witthoeft

et al. 2009

ApJS

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Reliable atomic data have been computed for the spectral modeling of the nitrogen K lines, which may lead to useful astrophysical diagnostics. Data sets comprise valence and K-vacancy level energies, wavelengths, Einstein A-coefficients, radiative and Auger widths and K-edge photoionization cross sections. An important issue is the lack of measurements which are usually employed to fine-tune calculations so as to attain spectroscopic accuracy. In order to estimate data quality, several atomic structure codes are used and extensive comparisons with previous theoretical data have been carried out. In the calculation of K photoabsorption with the Breit-Pauli R-matrix method, both radiation and Auger damping, which cause the smearing of the K edge, are taken into account. This work is part of a wider project to compute atomic data in the X-ray regime to be included in the database of the popular xstar modeling code.

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ChandraLETGS Spectroscopy of the Quasar MR 2251−178 and Its Warm Absorber

Cited by 14 publications

References 35 publications

A High Resolution View of the Warm Absorber in the Quasar MR 2251-178

A High Resolution View of the Warm Absorber in the Quasar MR 2251-178

A broad-band X-ray view of the warm absorber in radio-quiet quasar MR 2251−178

Nitrogen K-Shell Photoabsorption

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