Detection of Absorption Features in the X-Ray Spectrum of the Narrow-Line Quasar PG 1404+226: Possible Evidence of Accretion Disk Winds (original) (raw)
Related papers
2004
We present the results of an analysis of data from XMM-Newton and CHANDRA observations of the high luminosity narrow-line quasar PG 1404+226. We confirm a strong soft X-ray excess in the X-ray spectrum and we find rapid variability (a factor of two in about 5000 s). When the X-ray spectrum is fit with a two component model which includes a power-law and a blackbody component, we find that low energy absorption lines are required to fit the data. If we interpret these lines as due to highly ionized species of heavy elements in an outflowing accretion disk wind, an outflow velocity of ∼ 26000 km s −1 could be derived. One interesting feature of the present observation is the possible detection of variability in the absorption features: the absorption lines are visible only when the source is bright. From the upper limits of the equivalent widths (EW) of the absorption lines during the low flux states and also from the model independent pulse height ratios, we argue that the strength o...
The XMM-Newton Bright Survey sample of absorbed quasars: X-ray and accretion properties
Monthly Notices of the Royal Astronomical Society, 2014
Although absorbed quasars are extremely important for our understanding of the energetics of the Universe, the main physical parameters of their central engines are still poorly known. In this work, we present and study a complete sample of 14 quasars (QSOs) that are absorbed in the X-rays (column density N H > 4 × 10 21 cm −2 and X-ray luminosity L 2−10 keV > 10 44 ergs −1 ; XQSO2) belonging to the XMM-Newton Bright Serendipitous Survey (XBS). From the analysis of their ultraviolet-to-mid-infrared spectral energy distribution, we can separate the nuclear emission from the host galaxy contribution, obtaining a measurement of the fundamental nuclear parameters, like the mass of the central supermassive black hole and the value of Eddington ratio, λ Edd. Comparing the properties of XQSO2s with those previously obtained for the X-ray unabsorbed QSOs in the XBS, we do not find any evidence that the two samples are drawn from different populations. In particular, the two samples span the same range in Eddington ratios, up to λ Edd ∼ 0.5; this implies that our XQSO2s populate the 'forbidden region' in the so-called 'effective Eddington limit paradigm'. A combination of low grain abundance, presence of stars inwards of the absorber, and/or anisotropy of the disc emission can explain this result.
On the absorption of X-ray bright broad absorption line quasars
Arxiv preprint arXiv:0809.0832, 2008
Abstract: Most X-ray studies of BALQSOs found significant (N_H~ 10^{22-24} cm^{-2}) intrinsic column densities of gas absorbing an underlying typical power-law continuum emission, in agreement with expectations from radiatively driven accretion disk wind ...
Context. We have re-analyzed the X-ray spectra of the gravitational lensed high-redshift BAL QSO APM 08279+5255, observed with the XMM-Newton and Chandra observatories. Previous studies ) detected unusual, highly-ionized iron absorption features, but differed in their interpretation of these features, regarding the kinematical and ionization structure. Aims. We seek one physical model that can be successfully applied to both observations. Methods. For the first time we have performed detailed photoionization modeling on the X-ray spectrum of APM 08279+5255. Results. The absorbing gas in APM 08279+5255 can be represented by a two-absorbers model with column densities N H (1) ≈ 7×10 22 cm −2 , N H (2) ≈ 6 × 10 22 cm −2 , and ionization parameters log ξ(1) ≈ 1.5 and log ξ(2) ≈ 3, with one of them (the high-ionization component) outflowing at v ≈ 0.18(±0.01)c, carrying large amount of gas out of the system. We find that the Chandra spectrum of APM 08279+5255 requires the same Fe/O ratio overabundance (previously) indicated by the XMM-Newton observation, showing that both absorber components underwent similar chemical evolution and/or have similar origin.
XMM-Newton Observations of Broad Absorption Line Quasars with Polar Outflows
We have selected a sample of broad absorption line (BAL) quasars which show significant radio variations, indicating the presence of polar BAL outflows. We obtained snapshot XMM observations of four polar BAL QSOs, to check whether strong X-ray absorption, one of the most prominent characteristics of most BAL QSOs, also exists in polar outflows. Two of the sources are detected in the X-ray. Spectral fittings show that they are X-ray normal with no intrinsic X-ray absorption, suggesting the X-ray shielding gas might be absent in polar BAL outflows. Comparing to non-BAL QSOs, one of two X-ray-nondetected sources remains consistent with X-ray normal, while the other one, which is an iron low-ionization BAL (FeLoBAL), shows an X-ray weakness factor of 119, suggesting strong intrinsic X-ray absorption. Alternative explanations for the nondetection of strong X-ray absorption in the two X-ray-detected sources are that (1) the absorption is more complex than a simple neutral absorber, such as partial covering absorption or ionized absorption; (2) there might be significant jet contribution to the detected X-ray emission. Current data are insufficient to test these possibilities, and further observations are required to understand the X-ray nature of polar BAL outflows.
The Long-Term X-Ray Variability of Broad Absorption Line Quasars
The Astrophysical Journal, 2012
We analyze the long-term (rest-frame 3-30 yr) X-ray variability of eleven broad absorption line (BAL) quasars, mainly to constrain the variation properties of the X-ray absorbing shielding gas that is thought to play a critical role in BAL wind launching. Our BAL quasar sample has coverage with multiple X-ray observatories including Chandra, XMM-Newton, BeppoSAX , ASCA, ROSAT , and Einstein; 3-11 observations are available for each source. For seven of the eleven sources we have obtained and analyzed new Chandra observations suitable for searching for any strong X-ray variability. We find highly significant X-ray variability in three sources (PG 1001+054, PG 1004+130, and PG 2112+059). The maximum observed amplitude of the 2-8 keV variability is a factor of 3.8 ± 1.3, 1.5 ± 0.2, and 9.9 ± 2.3 for PG 1001+054, PG 1004+130, and PG 2112+059, respectively, and these sources show detectable variability on rest-frame timescales down to 5.8, 1.4, and 0.5 yr. For PG 1004+130 and PG 2112+059 we also find significant X-ray spectral variability associated with the flux variability. Considering our sample as a whole, we do not find that BAL quasars exhibit exceptional long-term X-ray variability when compared to the quasar population in general. We do not find evidence for common strong changes in the shielding gas owing to physical rearrangement or accretion-disk rotation, although some changes are found; this has implications for modeling observed ultraviolet BAL variability. Finally, we report for the first time an X-ray detection of the highly polarized and well-studied BAL quasar IRAS 14026+4341 in its new Chandra observation.
High velocity outflows in narrow absorption line quasars
The current paradigm for the AGN phenomenon is a central engine that consists of an inflow of material accreting in the form of a disk onto a supermassive black hole. Observations in the UV and optical find high velocity ionized material outflowing from the black hole. We present results from Suzaku and XMM-Newton observations of a sample of intrinsic NAL quasars with high velocity outflows. Our derived values of the intrinsic column densities of the X-ray absorbers are consistent with an outflow scenario in which NAL quasars are viewed at smaller inclination angles than BAL quasars. We find that the distributions of alpha_ox and D(alpha_ox) of the NAL quasars of our sample differ significantly from those of BAL quasars and SDSS radio-quiet quasars. The NAL quasars are not significantly absorbed in the X-ray band and the positive values of D(alpha_ox) suggest absorption in the UV band. The positive values of D(alpha_ox) of the intrinsic NAL quasars can be explained in a geometric scenario where our lines of sight towards the compact X-ray hot coronae of NAL quasars do not traverse the absorbing wind whereas lines of sight towards their UV emitting accretion disks do intercept the outflowing absorbers.
Thomson Thick X-Ray Absorption in a Broad Absorption Line Quasar, PG 0946+301
The Astrophysical Journal, 2000
We present a deep ASCA observation of a Broad Absorption Line Quasar (BALQSO) PG0946+301. The source was clearly detected in one of the gas imaging spectrometers, but not in any other detector. If BALQSOs have intrinsic X-ray spectra similar to normal radio-quiet quasars, our observations imply that there is Thomson thick X-ray absorption (N H > ∼ 10 24 cm −2 ) toward PG0946+301. This is the largest column density estimated so far toward a BALQSO. The absorber must be at least partially ionized and may be responsible for attenuation in the optical and UV. If the Thomson optical depth toward BALQSOs is close to one, as inferred here, then spectroscopy in hard X-rays with large telescopes like XMM would be feasible.
The X-ray emission from broad absorption line quasars
1999
PG 1411+442, and PG 0043+039. All three objects are found to be X-ray quiet, possibly due to substantial intrinsic absorption with N-H > 10(23) cm(-2) but might have intrinsically a more typical spectral energy distribution. This picture is supported by explicit spectral fits to the combined ROSAT/ASCA data of the nearby bright object PG 1411+442. An analysis of the large number of radio-quiet quasars not detected in the ROSAT All-Sky Survey indicates that perhaps only a small fraction of BAL quasars have not been recognized before and that the number of intrinsically X-ray quiet quasars must be small.
We present the results of the uniform analysis of 46 XMM-Newton observations of six BAL and seven mini-BAL QSOs belonging to the Palomar-Green Quasar catalogue. Moderate-quality X-ray spectroscopy was performed with the EPIC-pn, and allowed to characterise the general source spectral shape to be complex, significantly deviating from a power law emission. A simple power law analysis in different energy bands strongly suggests absorption to be more significant than reflection in shaping the spectra. If allowing for the absorbing gas to be either partially covering the continuum emission source or to be ionised, large column densities of the order of 1e(22−24) cm^{−2} are inferred. When the statistics was high enough, virtually every source was found to vary in spectral shape on various time scales, from years to hours. All in all these observational results are compatible with radiation driven accretion disk winds shaping the spectra of these intriguing cosmic sources.