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1031. X-ray spectral analysis of Swift/BAT AGNs
ID:
ivo://CDS.VizieR/J/ApJ/763/111
Title:
X-ray spectral analysis of Swift/BAT AGNs
Short Name:
J/ApJ/763/111
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a detailed X-ray spectral analysis of the non-beamed, hard X-ray selected active galactic nuclei (AGNs) in the northern Galactic cap of the 58 month Swift Burst Alert Telescope (Swift/BAT) catalog, consisting of 100 AGNs with b>50{deg}. This sky area has excellent potential for further dedicated study due to a wide range of multi-wavelength data that are already available, and we propose it as a low-redshift analog to the "deep field" observations of AGNs at higher redshifts (e.g., CDFN/S, COSMOS, Lockman Hole). We present distributions of luminosity, absorbing column density, and other key quantities for the catalog. We use a consistent approach to fit new and archival X-ray data gathered from XMM-Newton, Swift/XRT, ASCA, and Swift/BAT. We probe to deeper redshifts than the 9 month BAT catalog (<z>=0.043 compared to <z>=0.03 for the 9 month catalog), and uncover a broader absorbing column density distribution. The fraction of obscured (logN_H_>=22) objects in the sample is ~60%, and 43%-56% of the sample exhibits "complex" 0.4-10keV spectra. We present the average 1-10keV spectrum for the sample, which reproduces the 1-10keV X-ray background slope as found for the brighter 9 month BAT AGN sample.
1032. X-ray stacking analysis of Chandra-COSMOS gal.
ID:
ivo://CDS.VizieR/J/ApJ/865/43
Title:
X-ray stacking analysis of Chandra-COSMOS gal.
Short Name:
J/ApJ/865/43
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an X-ray stacking analysis of ~75000 star-forming galaxies between 0.1<z<5.0 using the Chandra COSMOS-Legacy survey to study the X-ray emission of low-luminosity active galactic nuclei (AGN) and its connection to host galaxy properties. The stacks at z<0.9 have luminosity limits as low as 10^40^-10^41^erg/s, a regime in which X-ray binaries (XRBs) can dominate the X-ray emission. Comparing the measured luminosities to established XRB scaling relations, we find that the redshift evolution of the luminosity per star formation rate (SFR) of XRBs depends sensitively on the assumed obscuration and may be weaker than previously found. The XRB scaling relation based on stacks from the Chandra Deep Field South overestimates the XRB contribution to the COSMOS high specific SFR stacks, possibly due to a bias affecting the CDF-S stacks because of their small galaxy samples. After subtracting the estimated XRB contribution from the stacks, we find that most stacks at z>1.3 exhibit a significant X-ray excess indicating nuclear emission. The AGN emission is strongly correlated with stellar mass but does not exhibit an additional correlation with SFR. The hardness ratios of the high-redshift stacks indicate that the AGN are substantially obscured (N_H_~10^23^cm^-2^). These obscured AGN are not identified by IRAC color selection and have L_X_~10^41^-10^43^erg/s, consistent with accretion at an Eddington rate of ~10^-3^ onto 10^7^-10^8^M_{sun}_ black holes. Combining our results with other X-ray studies suggests that AGN obscuration depends on stellar mass and an additional variable, possibly the Eddington rate.
1033. X-ray survey of the NDWFS Bootes field
ID:
ivo://CDS.VizieR/J/ApJS/161/9
Title:
X-ray survey of the NDWFS Bootes field
Short Name:
J/ApJS/161/9
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from a Chandra survey of the 9deg^2^ Bootes field of the NOAO Deep Wide-Field Survey (NDWFS). This XBootes survey consists of 126 separate contiguous ACIS-I observations each of approximately 5000s in duration. These unique Chandra observations allow us to search for large-scale structure and to calculate X-ray source statistics over a wide, contiguous field of view with arcsecond angular resolution and uniform coverage. The full 0.5-7keV band n>=4 count list has 3293 point sources. In addition to the point sources, 43 extended sources have been detected, consistent with the depth of these observations and the number counts of clusters. We present here the X-ray catalog for the XBootes survey, including source positions, X-ray fluxes, hardness ratios, and their uncertainties.
1034. X-ray through NIR photometry of NGC 2617
ID:
ivo://CDS.VizieR/J/ApJ/788/48
Title:
X-ray through NIR photometry of NGC 2617
Short Name:
J/ApJ/788/48
Date:
21 Oct 2021
Publisher:
CDS
Description:
After the All-Sky Automated Survey for SuperNovae discovered a significant brightening of the inner region of NGC 2617, we began a ~70 day photometric and spectroscopic monitoring campaign from the X-ray through near-infrared (NIR) wavelengths. We report that NGC 2617 went through a dramatic outburst, during which its X-ray flux increased by over an order of magnitude followed by an increase of its optical/ultraviolet (UV) continuum flux by almost an order of magnitude. NGC 2617, classified as a Seyfert 1.8 galaxy in 2003, is now a Seyfert 1 due to the appearance of broad optical emission lines and a continuum blue bump. Such "changing look active galactic nuclei (AGNs)" are rare and provide us with important insights about AGN physics. Based on the H{beta} line width and the radius-luminosity relation, we estimate the mass of central black hole (BH) to be (4+/-1)x10^7^ M_{sun}_. When we cross-correlate the light curves, we find that the disk emission lags the X-rays, with the lag becoming longer as we move from the UV (2-3 days) to the NIR (6-9 days). Also, the NIR is more heavily temporally smoothed than the UV. This can largely be explained by a simple model of a thermally emitting thin disk around a BH of the estimated mass that is illuminated by the observed, variable X-ray fluxes.
1035. X-ray to MIR luminosities relation of AGNs
ID:
ivo://CDS.VizieR/J/ApJ/807/129
Title:
X-ray to MIR luminosities relation of AGNs
Short Name:
J/ApJ/807/129
Date:
21 Oct 2021
Publisher:
CDS
Description:
The X-ray and mid-IR emission from active galactic nuclei (AGNs) are strongly correlated. However, while various published parameterizations of this correlation are consistent with the low-redshift, local Seyfert galaxy population, extrapolations of these relations to high luminosity differ by an order of magnitude at {nu}L_{nu}_(6{mu}m)~10^47^erg/s. Using data from the Wide-field Infrared Survey Explorer, we determine the mid-IR luminosities of the most luminous quasars from the Sloan Digital Sky Survey and present a revised formulation of the X-ray to mid-IR relation of AGNs which is appropriate from the Seyfert regime to the powerful quasar regime.
1036. X-ray/UV ratio of AGN
ID:
ivo://CDS.VizieR/J/A+A/619/A95
Title:
X-ray/UV ratio of AGN
Short Name:
J/A+A/619/A95
Date:
21 Oct 2021
Publisher:
CDS
Description:
The well established negative correlation between the {alpha}_OX_ spectral slope and the optical/UV luminosity, a by product of the relation between X-rays and optical/UV luminosity, is affected by a relatively large dispersion. The main contributions can be variability in the X-ray/UV ratio and/or changes in fundamental physical parameters. We want to quantify the contribution of variability within single sources (intra-source dispersion) and that due to variations of other quantities different from source to source (inter-source dispersion). We use archival data from the XMM-Newton Serendipitous Source Catalog (XMMSSC, Cat. IX/50) and from the XMM-OM Serendipitous Ultra-violet Source Survey (XMMOM-SUSS3, Cat. II/340). We select a sub-sample in order to decrease the dispersion of the relation due to the presence of Radio-Loud and Broad Absorption Line objects, and to absorptions in both X-ray and optical/UV bands. We use the Structure Function (SF) to estimate the contribution of variability to the dispersion. We analyse the dependence of the residuals of the relation on various physical parameters in order to characterise the inter-source dispersion. We find a total dispersion of {sigma}~0.12 and we find that intrinsic variability contributes for 56 percent of the variance of the {alpha}_OX_-L_UV_ relation. If we select only sources with a larger number of observational epochs (>2) the dispersion of the relation decreases by approximately 15 percent. We find weak but significant dependences of the residuals of the relation on black-hole mass and on Eddington ratio, which are also confirmed by a multivariate regression analysis of {alpha}_OX_ as a function of UV luminosity and black-hole mass and/or Eddington ratio. We find a weak positive correlation of both the {alpha}_OX_ index and the residuals of the {alpha}_OX_-LUV relation with inclination indicators, such as the FWHM(H{beta}) and the EW[OIII], suggesting a weak increase of X-ray/UV ratio with the viewing angle. This suggests the development of new viewing angle indicators possibly applicable at higher redshifts. Moreover, our results suggest the possibility of selecting a sample of objects, based on their viewing angle and/or black-hole mass and Eddington ratio, for which the {alpha}_OX_-LUV relation is as tight as possible, in light of the use of the optical/UV-X-ray luminosity relation to build a distance modulus (DM)-z plane and estimate cosmological parameters.
1037. X-ray/UV ratio of 2XMM AGN
ID:
ivo://CDS.VizieR/J/A+A/519/A17
Title:
X-ray/UV ratio of 2XMM AGN
Short Name:
J/A+A/519/A17
Date:
21 Oct 2021
Publisher:
CDS
Description:
The observed relation between the X-ray radiation from active galactic nuclei, originating in the corona, and the optical/UV radiation from the disk is usually described by the anticorrelation between the UV to X-ray slope {alpha}_ox_ and the UV luminosity. Many factors can affect this relation, including: i) enhanced X-ray emission associated with the jets of radio-loud AGNs, ii) X-ray absorption associated with the UV broad absorption line (BAL) outflows, iii) other X-ray absorption not associated with BALs, iv) intrinsic X-ray weakness, v) UV and X-ray variability, and non-simultaneity of UV and X-ray observations. The separation of these effects provides information about the intrinsic {alpha}_ox_-L_UV_ relation and its dispersion, constraining models of disk-corona coupling. We use simultaneous UV/X-ray observations to remove the influence of non-simultaneous measurements from the {alpha}_ox_-L_UV_ relation.
1038. X-ray/UV Swift monitoring of NGC 4151
ID:
ivo://CDS.VizieR/J/ApJ/840/41
Title:
X-ray/UV Swift monitoring of NGC 4151
Short Name:
J/ApJ/840/41
Date:
21 Oct 2021
Publisher:
CDS
Description:
Swift monitoring of NGC 4151 with an ~6hr sampling over a total of 69days in early 2016 is used to construct light curves covering five bands in the X-rays (0.3-50keV) and six in the ultraviolet (UV)/optical (1900-5500{AA}). The three hardest X-ray bands (>2.5keV) are all strongly correlated with no measurable interband lag, while the two softer bands show lower variability and weaker correlations. The UV/optical bands are significantly correlated with the X-rays, lagging ~3-4days behind the hard X-rays. The variability within the UV/optical bands is also strongly correlated, with the UV appearing to lead the optical by ~0.5-1days. This combination of >~3day lags between the X-rays and UV and <~1day lags within the UV/optical appears to rule out the "lamp-post" reprocessing model in which a hot, X-ray emitting corona directly illuminates the accretion disk, which then reprocesses the energy in the UV/optical. Instead, these results appear consistent with the Gardner & Done (2017MNRAS.470.3591G) picture in which two separate reprocessings occur: first, emission from the corona illuminates an extreme-UV-emitting toroidal component that shields the disk from the corona; this then heats the extreme-UV component, which illuminates the disk and drives its variability.
1039. X-ray variability of AGN
ID:
ivo://CDS.VizieR/J/A+A/536/A84
Title:
X-ray variability of AGN
Short Name:
J/A+A/536/A84
Date:
21 Oct 2021
Publisher:
CDS
Description:
The X-ray variability of the active galactic nuclei (AGN) has been most often investigated with studies of individual, nearby sources, and only a few ensemble analyses have been applied to large samples in wide ranges of luminosity and redshift. We aim to determine the ensemble variability properties of two serendipitously selected AGN samples extracted from the catalogues of XMM-Newton and Swift, with redshift between ~0.2 and ~4.5, and X-ray luminosities, in the 0.5-4.5keV band, between ~10^43^erg/s and ~10^46^erg/s. We used the structure function (SF), which operates in the time domain, and allows for an ensemble analysis even when only a few observations are available for individual sources and the power spectral density (PSD) cannot be derived. The SF is also more appropriate than fractional variability and excess variance, because these parameters are biased by the duration of the monitoring time interval in the rest-frame, and therefore by cosmological time dilation.
1040. X-ray variability of AGNs in Lockman Hole
ID:
ivo://CDS.VizieR/J/A+A/487/475
Title:
X-ray variability of AGNs in Lockman Hole
Short Name:
J/A+A/487/475
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results from a detailed X-ray variability analysis of 66 AGN in the Lockman Hole, which have optical spectroscopic identifications. We compare, quantitatively, their variability properties with the properties of local AGN, and we study the "variability - luminosity" relation as a function of redshift, and the "variability - redshift" relation in two luminosity bins. We use archival data from the last 10 XMM-Newton observations of the Lockman Hole field to extract light curves in the rest frame, 2-10keV band. We use the "normalized excess variance" to quantify the variability amplitude. Using the latest results regarding the AGN power spectral shape and its dependence on black hole mass and accretion rate, we are able to compute model "variability - luminosity" curves, which we compare with the relations we observe. When we consider all the sources in our sample, we find that their variability amplitude decreases with increasing redshift and luminosity.