BASS-XL: X-ray variability properties of unobscured Active Galactic Nuclei
Alessia Tortosa, Claudio Ricci, Patricia Arévalo, Michael J. Koss, Franz E. Bauer, Benny Trakhtenbrot, Richard Mushotzky, Matthew J. Temple, Federica Ricci, Ale… 展开作者
Alessia Tortosa, Claudio Ricci, Patricia Arévalo, Michael J. Koss, Franz E. Bauer, Benny Trakhtenbrot, Richard Mushotzky, Matthew J. Temple, Federica Ricci, Alejandra Rojas Lilayu, Taiki Kawamuro, Turgay Caglar, Tingting Liu, Fiona Harrison, Kyuseok Oh, Meredith Clark Powell, Daniel Stern, Claudia Megan Urry
备注：
Monthly Notices of the Royal Astronomical Society, Volume 526, Issue 2, pp.1687-1698
我们研究了属于BAT AGN光谱巡天（BASS）的塞弗特1型星系的X射线变异性性质。该样本包括151个未被遮蔽（N$_{\ m H}<10^{22}$ cm$^{-2}$）的活动星系核（AGN），它们由XMM-Newton观测，总曝光时间约为27 Ms，代表了迄今为止使用高信噪比XMM-Newton观测所做的最深入的变异性研究，几乎使先前工作中分析的观测数量翻倍。我们约束了归一化超额方差与2-10 keV AGN光度、黑洞质量和爱丁顿比率之间的关系。我们发现$σ^{2}_{NXS}$与$M_{\ m BH}$之间存在高度显著的相关性，其离散度约为0.85 dex。对于具有高$L_{2-10}$的源，这种相关性的归一化较低，证实了更明亮（更大质量）的AGN表现出较少的变异性。我们探讨了对于通过“反响映射”技术估计$M_{\ m BH}$的源子样本的$σ^{2}_{NXS}$与$M_{\ m BH}$关系，发现更紧密的反相关，离散度约为0.65 dex。我们通过研究硬（3-10 keV）和软（0.2-1 keV）/中（1-3 keV）能带中的变异性关系来检查$σ^{2}_{NXS}$如何随能量变化，发现在短于10 ks的时间尺度上，主导硬能带的谱成分比主导较软能带的谱成分更具变异性。
英文摘要：
We investigate the X-ray variability properties of Seyfert1 Galaxies belonging to the BAT AGN Spectroscopic Survey (BASS). The sample includes 151 unobscured (N$_{\rm H}<10^{22}$ cm$^{-2}$) AGNs observed with XMM-Newton for a total exposure time of ~27 Ms, representing the deepest variability study done so far with high signal-to-noise XMM-Newton observations, almost doubling the number of observations analysed in previous works. We constrain the relation between the normalised excess variance and the 2-10 keV AGN luminosities, black hole masses and Eddington ratios. We find a highly significant correlation between $σ^{2}_{NXS}$ and $M_{\rm BH}$, with a scatter of ~0.85 dex. For sources with high $L_{2-10}$ this correlation has a lower normalization, confirming that more luminous (higher mass) AGNs show less variability. We explored the $σ^{2}_{NXS}$ vs $M_{\rm BH}$ relation for the sub-sample of sources with $M_{\rm BH}$ estimated via the "reverberation mapping" technique, finding a tighter anti-correlation, with a scatter of ~ 0.65 dex. We examine how the $σ^{2}_{NXS}$ changes with energy by studying the relation between the variability in the hard (3-10 keV) and the soft (0.2-1 keV)/medium (1-3 keV) energy bands, finding that the spectral components dominating the hard energy band are more variable than the spectral components dominating in softer energy bands, on timescales shorter than 10 ks.
We study the relation between obscuration and supermassive black hole (SMBH) growth using a large sample of hard X-ray selected Active Galactic Nuclei (AGN). We find a strong decrease in the fraction of obscured sources above the Eddington limit for dusty gas ($\log λ_{\rm Edd}\gtrsim -2$) confirming earlier results, and consistent with the radiation-regulated unification model. This also explains the difference in the Eddington ratio distribution functions (ERDFs) of type 1 and type 2 AGN obtained by a recent study. The break in the ERDF of nearby AGN is at $\log λ_{\rm Edd}^{*}=-1.34\pm0.07$…
We determine the low-redshift X-ray luminosity function (XLF), active black hole mass function (BHMF), and Eddington-ratio distribution function (ERDF) for both unobscured (Type 1) and obscured (Type 2) active galactic nuclei (AGN) using the unprecedented spectroscopic completeness of the BAT AGN Spectroscopic Survey (BASS) data release 2. In addition to a straightforward 1/Vmax approach, we also compute the intrinsic distributions, accounting for sample truncation by employing a forward modeling approach to recover the observed BHMF and ERDF. As previous BHMFs and ERDFs have been robustly det…
BASS LV. Connecting X-ray variability with AGN physical properties and a new path to Cosmological distances
Università degli Studi Roma Tre（罗马第三大学）；INAF – Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切里天文台）；European Space Agency (ESA), European Space Research and Technology Centre (ESTEC)（欧洲空间局欧洲空间研究与技术中心）；INAF – Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（意大利国家天体物理研究所博洛尼亚天文与空间科学台）；Pontificia Universidad Católica de Chile, Instituto de Astrofísica（智利天主教大学天体物理研究所）；Cahill Center for Astronomy and Astrophysics, California Institute of Technology（加州理工学院凯尔天文学与天体物理学中心）；Frontier Research Institute for Interdisciplinary Sciences, Tohoku University（东北大学跨学科前沿研究院）
Changing-look (CL) AGN are unique probes of accretion onto supermassive black holes (SMBHs), especially when simultaneous observations in complementary wavebands allow investigations into the properties of their accretion flows. We present the results of a search for CL behaviour in 412 Swift-BAT detected AGN with multiple epochs of optical spectroscopy from the BAT AGN Spectroscopic Survey (BASS). 125 of these AGN also have 14-195 keV ultra-hard X-ray light-curves from Swift-BAT which are contemporaneous with the epochs of optical spectroscopy. Eight CL events are presented for the first time…
We report on the discovery of a dramatic X-ray spectral variability event observed in a $z\sim 1$ broad line type-1 QSO. The XMM-Newton spectrum from the year 2000 is characterized by an unobscured power-law spectrum with photon index of $Γ\sim 2$, a column density of $N_{\mathrm{H}}\sim 5\times 10^{20}\,\mathrm{cm^{-2}}$, and no prominent reflection component. Five years later, Chandra captured the source in a heavily-obscured, reflection-dominated state. The observed X-ray spectral variability could be caused by a Compton-thick cloud with $N_{\mathrm{H}}\sim 2\times 10^{24}\,\mathrm{cm^{-2}}…
Fooled by mass? Recovering the $Γ-λ_{Edd}$ relation of quasars from their X-ray variability
European Space Agency (ESA), European Space Research and Technology Centre (ESTEC)（欧洲空间局（ESA），欧洲空间研究与技术中心（ESTEC））；INAF - Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所 - 阿切特里天文台）；INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano（意大利国家天体物理研究所 - 米兰空间天体物理学与宇宙物理学研究所）；Scuola Normale Superiore（比萨高等师范学院）；Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze（佛罗伦萨大学物理与天文系）；Scuola Superiore Meridionale（南方高等学院）；Istituto Nazionale di Fisica Nucleare, sez. di Napoli（意大利国家核物理研究所，那不勒斯分部）
Scaling relations are the most powerful astrophysical tools to set constraints to the physical mechanisms of astro- nomical sources and to infer properties that cannot be accessed directly. We re-investigate here one of these scaling relations in active galactic nuclei (AGN); the so-called X-ray variability plane (or mass-luminosity-timescale relation, McHardy et al. 2006). This relation links the power-spectral density (PSD) break frequency with the super-massive black hole (SMBH) mass and the bolometric luminosity. We used available XMM -Newton observations of a sample of 22 AGN to study the…
We perform long-term ($\approx 15$ yr, observed-frame) X-ray variability analyses of the 68 brightest radio-quiet active galactic nuclei (AGNs) in the 6 Ms $Chandra$ Deep Field-South (CDF-S) survey; the majority are in the redshift range of $0.6-3.1$, providing access to penetrating rest-frame X-rays up to $\approx 10-30$ keV. Twenty-four of the 68 sources are optical spectral type I AGNs, and the rest (44) are type II AGNs. The time scales probed in this work are among the longest for X-ray variability studies of distant AGNs. Photometric analyses reveal widespread photon-flux variability: $9…
We present results of recurrence analysis of 46 active galactic nuclei (AGN) using light curves from the 157-month catalog of the Swift Burst Alert Telescope (BAT) in the 14-150 keV band. We generate recurrence plots and compute recurrence plot metrics for each object. We use the surrogate data method to compare all derived recurrence-based quantities to three sets of stochastic light curves with identical power spectrum, flux distribution, or both, in order to determine the presence of determinism, non-linearity, entropy, and non-stationarity. We compare these quantities with known physical c…
Fairall 51 is a polar-scattered Seyfert 1 galaxy, a type of active galaxies believed to represent a bridge between unobscured type-1 and obscured type-2 objects. Fairall 51 has shown complex and variable X-ray absorption but only little is known about its origin. In our research, we observed Fairall 51 with the X-ray satellite Suzaku in order to constrain a characteristic time-scale of its variability. We performed timing and spectral analysis of four observations separated by 1.5, 2 and 5.5 day intervals. We found that the 0.5-50 keV broadband X-ray spectra are dominated by a primary power-la…
Context. Obscuration events caused by outflowing clumps or streams of high column density, low ionisation gas, heavily absorbing the X-ray continuum, have been witnessed in a number of Seyfert galaxies. Aims. We report on the X-ray spectral-timing analysis of the December 2016 obscuration event in NGC 3783, 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 th…
We report on the X-ray time resolved spectral analysis of XMM-Newton observations of NGC 3783. The main goal is to detect transient features in the Fe K line complex, in order to study the dynamics of the innermost accretion flow. We reanalize archival observations of NGC 3783, a bright local AGN, for which a transient Fe line was reported, complementing this data set with new available observations. This results in a long set of observations which can allow us to better assess the significance of transient features and possibly test their recurrence time. Moreover, since the new data catch th…
The Circinus galaxy is one of the nearest obscured AGN, making it an ideal target for detailed study. Combining archival Chandra and XMM-Newton data with new NuSTAR observations, we model the 2-79 keV spectrum to constrain the primary AGN continuum and to derive physical parameters for the obscuring material. Chandra's high angular resolution allows a separation of nuclear and off-nuclear galactic emission. In the off-nuclear diffuse emission we find signatures of strong cold reflection, including high equivalent-width neutral Fe lines. This Compton-scattered off-nuclear emission amounts to 18…
We analysed the archival XMM-Newton data of the radio loud narrow line Seyfert1 galaxy PMN J0948+0022 in the energy range 0.3--10.0 keV. The X-ray data reveal that the spectrum in the 0.3--10.0 keV energy band is not a simple power-law as previously described in the literature. Instead it consists of a power-law with soft excess below 2.5 keV. The X-ray spectrum was fitted with four different models and it was shown the soft excess component of the spectrum in the 0.3--2.5 keV energy range could be described reasonably well within the framework of the thermal Comptonization model as well as re…
We use the 4Ms CDF-S survey to place direct X-ray constraints on the ubiquity of z~2 heavily obscured AGNs in K<22 BzK galaxies. Forty seven of the 222 BzK galaxies in the central region of the CDF-S are detected at X-ray energies, 11 of which have hard X-ray spectral slopes (Gamma<1) indicating the presence of heavily obscured AGN activity. The other 36 X-ray detected BzK galaxies appear to be relatively unobscured AGNs and starburst galaxies; we use X-ray variability analyses over a rest-frame baseline of ~3 years to further confirm the presence of AGN activity in many of these systems. The …
MAGIC, a stereoscopic cherenkov telescope array, sensitive to gamma-rays between 50 GeV and several tens of TeV, is ideally suited to observe promising Fermi LAT sources with a hard γ-ray spectrum. Here we discuss the discovery of very high energy gamma-ray (VHE, E > 100 GeV) emission from the Fermi LAT sources 1FGL J2001.1+4351 and B3-2247+381 with MAGIC. 1FGL J2001.1+4351, recently identified as MG4 J200112+4352 (Bassani et al. 2010), is most likely a high peaked BL Lacertae object. The red shift of this source is still unknown, though the identification of the optical host galaxy suggests z…
