Variable X-ray absorption in the mini-BAL QSO PG 1126-041

Giustini, M.; Cappi, M.; Chartas, G.; Dadina, M.; Eracleous, Michael; Ponti, G.; Proga, Daniel; Tombesi, Francesco; Vignali, C.; Palumbo, G. G. C.

doi:10.1051/0004-6361/201117732

Cited by 52 publications

(60 citation statements)

References 85 publications

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“…However, it is possible that the flux illuminating the absorber can change by large factors as a result of variable transmission through a porous or patchy "screen" between the absorber and the continuum source. This possibility was suggested by Misawa et al (2007) and it is supported by observations of rapid, high-amplitude X-ray variability in mini-BAL quasars (e.g., Giustini et al 2011). Such a scenario is also compatible with the observation that multiple absorption systems (A, B, and C) at different velocities and with different trough shapes vary in concert.…”

Section: Possible Causes Of the Observed Variabilitysupporting

confidence: 68%

Discovery of the Transition of a Mini-Broad Absorption Line Into a Broad Absorption Line in the SDSS Quasar J115122.14+020426.3

Hidalgo

Eracleous

Charlton

et al. 2013

ApJ

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We present the detection of a rare case of dramatic strengthening in the UV absorption profiles in the spectrum of the quasar J115122.14+020426.3 between observations ∼2.86 yr apart in the quasar rest frame. A spectrum obtained in 2001 by the Sloan Digital Sky Survey shows a C iv "mini-broad" absorption line (FWHM = 1220 km s −1 ) with a maximum blueshift velocity of ∼9520 km s −1 , while a later spectrum from the Very Large Telescope shows a significantly broader and stronger absorption line, with a maximum blueshift velocity of ∼12,240 km s −1 that qualifies as a broad absorption line. A similar variability pattern is observed in two additional systems at lower blueshifted velocities and in the Lyα and N v transitions as well. One of the absorption systems appears to be resolved and shows evidence for partial covering of the quasar continuum source (C f ∼ 0.65), indicating a transverse absorber size of, at least, ∼6 × 10 16 cm. In contrast, a cluster of narrower C iv lines appears to originate in gas that fully covers the continuum and broad emission line sources. There is no evidence for changes in the centroid velocity of the absorption troughs. This case suggests that at least some of the absorbers that produce "mini-broad" and broad absorption lines in quasar spectra do not belong to intrinsically separate classes. Here, the "mini-broad" absorption line is most likely interpreted as an intermediate phase before the appearance of a broad absorption line due to their similar velocities. While the current observations do not provide enough constraints to discern among the possible causes for this variability, future monitoring of multiple transitions at high resolution will help achieve this goal.

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Section: Possible Causes Of the Observed Variabilitysupporting

confidence: 68%

Discovery of the Transition of a Mini-Broad Absorption Line Into a Broad Absorption Line in the SDSS Quasar J115122.14+020426.3

Hidalgo

Eracleous

Charlton

et al. 2013

ApJ

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“…Short time variability for both flux and absorption column density (Elvis et al 2004;Risaliti et al 2007;Giustini et al 2011) implies obscuration material at smaller radii than the dusty torus inner radius, which is set by the sublimation radius (R sub , e.g., Suganuma et al 2006;Nenkova et al 2008). These dust-free gas clouds will only absorb X-ray emission and will not re-emit a continuum spectrum in the IR as dust does.…”

Section: Discussion On Agn Ir-selection Completenessmentioning

confidence: 99%

The dependency of AGN infrared colour-selection on source luminosity and obscuration

Messias

Afonso

Salvato

et al. 2014

A&A

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Aims. This work addresses the AGN IR-selection dependency on intrinsic source luminosity and obscuration, in order to identify and characterise biases that could affect conclusions in studies. Methods. We study IR-selected AGN in the Chandra Deep Field South (CDFS) survey and in the Cosmological Survey (COSMOS). The AGN sample is divided into low and high X-ray luminosity classes and into unobscured (type-1) and obscured (type-2) classes by means of X-ray and optical spectroscopy data. Specifically in the X-ray regime, we adopt the intrinsic luminosity taking the estimated column density (N H ) into account. We also take the opportunity to highlight important differences resulting from adopting different methods of assessing AGN obscuration. Results. In agreement with previous studies, we also find that AGN IR-selection efficiency shows a decrease with decreasing source AGN X-ray luminosity. For the intermediate-luminosity AGN population (43.3 < ∼ log(L X [erg s −1 ]) < ∼ 44), the efficiency also worsens with increasing obscuration (N H ). The same sample also shows an evolution with cosmic time of the obscured fraction at the highest X-ray luminosities, independently of the adopted type-1/type-2 classification method. Conclusions. We confirm that AGN IR-selection is genuinely biased towards unobscured AGNe, but only at intermediate luminosities.At the highest luminosities, where AGN IR-selection is more efficient, there is no obscuration bias. We show that type-1 AGNe are intrinsically more luminous than type-2 AGNe only at z < ∼ 1.6, thus resulting in more type-1 AGN being selected when the IR survey is shallower. Based on this and other studies, we conclude that deep hard-X-ray coverages, high-resolution IR imaging, or a combination of IR and radio data are required to recover the lower luminosity obscured AGN population. In addition, wide IR surveys are needed to recover the rare powerful, obscured AGN population. Finally, when the James Webb Space Telescope comes online, the broad-band filters 2.0 µm, 4.4 µm, 7.7 µm, and 18 µm will be essential for disentangling AGN from non-AGN dominated SEDs at depths where spectroscopy becomes impractical.

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“…Variability of Fe K absorption features between observations separated by days to years has been often found in well-studied objects, for instance, Chartas et al (2009) and Tombesi et al (2011). Faster variability within a single observation was reported for BAL QSO PG 1126-041 by Giustini et al (2011). The variability seen in IRAS 18325-5926 is one of the rapid extremes.…”

Section: Ionized Disc and Transient High-velocity Outflowsmentioning

confidence: 94%

Highly ionized disc and transient outflows in the Seyfert galaxy IRAS 18325–5926

Iwasawa

Fabian

Kara

et al. 2016

A&A

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We report on strong X-ray variability and the Fe K-band spectrum of the Seyfert galaxy IRAS 18325-5926 obtained from the 2001 XMM-Newton EPIC pn observation with a duration of ∼120 ks. While the X-ray source is highly variable, the 8-10 keV band shows larger variability than that of the lower energies. Amplified 8-10 keV flux variations are associated with two prominent flares of the X-ray source during the observation. The Fe K emission is peaked at 6.6 keV with moderate broadening. It is likely to originate from a highly ionized disc with an ionization parameter of log ξ 3. The Fe K line flux responds to the main flare, which supports its disc origin. A short burst of the Fe line flux has no relation to the continuum brightness, for which we have no clear explanation. We also find transient, blueshifted Fe K absorption features that can be identified with high-velocity (∼0.2 c) outflows of highly ionized gas, as found in other active galaxies. The deepest absorption feature appears only briefly (∼1 h) at the onset of the main flare and disappears when the flare declines. The rapid evolution of the absorption spectrum makes this source peculiar among the active galaxies with high-velocity outflows. Another detection of the absorption feature also precedes the other flare. The variability of the absorption feature partly accounts for the excess variability in the 8-10 keV band where the absorption feature appears. Although no reverberation measurement is available, the black hole mass of ∼2 × 10 6 M is inferred from the X-ray variability. When this mass is assumed, the black hole is accreting at around the Eddington limit, which may fit the highly ionized disc and strong outflows observed in this galaxy.

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Variable X-ray absorption in the mini-BAL QSO PG 1126-041

Cited by 52 publications

References 85 publications

Discovery of the Transition of a Mini-Broad Absorption Line Into a Broad Absorption Line in the SDSS Quasar J115122.14+020426.3

Discovery of the Transition of a Mini-Broad Absorption Line Into a Broad Absorption Line in the SDSS Quasar J115122.14+020426.3

The dependency of AGN infrared colour-selection on source luminosity and obscuration

Highly ionized disc and transient outflows in the Seyfert galaxy IRAS 18325–5926

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