Resolving the X-Ray Obscuration in a Low-flux Observation of the Quasar PDS 456

Reeves, J. N.; Braito, V.; Nardini, E.; Hamann, Fred; Chartas, G.; Lobban, A.; O’Brien, P. T.; Turner, T. J.

doi:10.3847/1538-4357/aae30c

Cited by 19 publications

(14 citation statements)

References 79 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Depending on the ionisation state, column density and covering factor of the outflowing gas, these absorption features can greatly modify the observed emission from the AGN (e.g. Nardini et al 2015;Reeves et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Incoherent fast variability of X-ray obscurers

Marco

Adhikari

Ponti

et al. 2020

A&A

View full text Add to dashboard Cite

Context. Obscuration events caused by outflowing clumps or streams of high column density and low ionised gas, shown to absorb the X-ray continuum heavily, have been witnessed across a number of Seyfert galaxies. Aims. We report on the X-ray spectral-timing analysis of the December 2016 obscuration event in NGC 3783, which was aimed at probing variability of the X-ray obscurer on the shortest possible timescales. The main goals of this study are to obtain independent constraints on the density and, ultimately on the distance of the obscuring gas, as well as to characterise the impact of variable obscuration on the observed X-ray spectral-timing characteristics of Seyfert galaxies. Methods. We carried out a comparative analysis of NGC 3783 during unobscured (using archival 2000–2001 XMM-Newton data) and obscured states (using XMM-Newton and NuSTAR data from the 2016 observational campaign). The analysed timescales range between ten hours and about one hour. This study was then generalised to discuss the signatures of variable obscuration in the X-ray spectral-timing characteristics of Seyfert galaxies as a function of the physical properties of the obscuring gas. Results. The X-ray obscurer in NGC 3783 is found to vary on timescales between about one hour to ten hours. This variability is incoherent with respect to the variations of the X-ray continuum. A fast response (on timescales shorter than about 1.5 ks) of the ionisation state of the obscuring gas to the short timescale variability of the primary X-ray continuum provides a satisfactory interpretation of all the observed X-ray spectral-timing properties. This study enabled us to put independent constraints on the density and location of the obscuring gas. We found the gas to have a density of ne > 7.1 × 107 cm−3, which is consistent with a location in the broad line region.

show abstract

Section: Introductionmentioning

confidence: 99%

Incoherent fast variability of X-ray obscurers

Marco

Adhikari

Ponti

et al. 2020

A&A

View full text Add to dashboard Cite

show abstract

“…Monitoring was also performed in 2017 over a longer 200 day baseline from 2017/03/23 to 2017/10/09, consisting of 45 individual exposures, on an approximate daily sampling during the first 18 days and the remainder of the monitoring with a roughly weekly sampling. Note the very start of the 2017 Swift campaign also coincided with a joint XMM-Newton and NuSTAR observation; the observations have been presented in Reeves et al (2018b) and were at a low flux level. Monitoring was resumed for about a month from 2019/08/31 to 2019/09/26, consisting of 22 pointings, in order to coincide with the two 2019 XMM-Newton observations published in paper I.…”

Section: Swift Monitoringmentioning

confidence: 73%

The flaring X-ray corona in the quasar PDS 456

Reeves,

Braito,

Porquet

et al. 2020

Preprint

View full text Add to dashboard Cite

New Swift monitoring observations of the variable, radio-quiet quasar, PDS 456, are presented. A bright X-ray flare was captured in September 2018, the flux increasing by a factor of 4 and with a doubling time-scale of 2 days. From the light crossing argument, the coronal size is inferred to be ∼ < 30 gravitational radii for a black hole mass of 10 9 M ⊙ and the total flare energy exceeds 10 51 erg. A hardening of the X-ray emission accompanied the flare, with the photon index decreasing from Γ = 2.2 to Γ = 1.7 and back again. The flare is produced in the X-ray corona, the lack of any optical or UV variability being consistent with a constant accretion rate. Simultaneous XMM-Newton and NuSTAR observations were performed, 1 − 3 days after the flare peak and during the decline phase. These caught PDS 456 in a bright, bare state, where no disc wind absorption features are apparent. The hard X-ray spectrum shows a high energy roll-over, with an e-folding energy of E fold = 51 +11 −8 keV. The deduced coronal temperature, of kT = 13 keV, is one of the coolest measured in any AGN and PDS 456 lies well below the predicted pair annihilation line in X-ray corona. The spectral variability, becoming softer when fainter following the flare, is consistent with models of cooling X-ray coronae. Alternatively, an increase in a non-thermal component could contribute towards the hard X-ray flare spectrum.

show abstract

“…Ionized outflowing winds have been connected to absorbing partial covering by, e.g. Reeves et al (2018) and references therein. The authors argue that the outflowing wind is inhomogeneous and complex rather than a simple homogeneous outflow, which is capable of partially covering the X‐ray source.…”

Section: Erosita Calpv Observations Of 1h 0707‐495mentioning

confidence: 99%

1H 0707‐495: An AGN is dimming its X‐ray light

Böller

2021

Astron Nachr

View full text Add to dashboard Cite

We report on one of the first science observations obtained during the Calibration and Verification phase of extended ROentgen Survey with an Imaging Telescope Array (eROSITA) aboard the Spectrum-Roentgen-Gamma (SRG) mission on the famous Narrow-Line Seyfert 1 Galaxy 1H 0707-495. 1H 0707-495 is a highly variable AGN, with a complex, steep X-ray spectrum, which has been the subject of intense studies with XMM-Newton in the past. During the eROSITA observations, 1H 0707-495 showed a dramatic flux drop in about 1 day.The source is brightest at the beginning of the observations, with rapid fluctuations in count rate, followed by a subsequent decline in count rate going down close to the background level. The mean amplitude variability is a factor of 58, with a 1 error confidence interval with factors between 31 and 235. Similar, large-amplitude count-rate changes are deduced from the XMM-Newton EPIC-pn and MOS2 light curves. The energy band up to only 0.8 keV is dominating the amplitude variability, followed by a sudden drop in variability above 0.8 keV. Such extreme ultrasoft and large-amplitude flux variability in active galactic nuclei has not been detected with other X-ray observations so far. A physical explanation for the timing and spectral properties is a combination of strong relativistic effects close to the black hole and absorption by an ionized partial coverer. From the high-to the low-flux state, the partial coverer is obscuring an increasing part of the emitted X-ray radiation. Ionized outflowing absorbers are more transparent in the soft X-rays than neutral absorbers and thus show leakage effects in the soft X-rays, explaining the ultrasoft light curve.

show abstract

Resolving the X-Ray Obscuration in a Low-flux Observation of the Quasar PDS 456

Cited by 19 publications

References 79 publications

Incoherent fast variability of X-ray obscurers

Incoherent fast variability of X-ray obscurers

The flaring X-ray corona in the quasar PDS 456

1H 0707‐495: An AGN is dimming its X‐ray light

Contact Info

Product

Resources

About