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Start Over Subject quasars Validation Level 2
1041. X- and gamma-ray fluxes of {gamma}-ray-loud blazars
ID:
ivo://CDS.VizieR/J/A+A/436/799
Title:
X- and gamma-ray fluxes of {gamma}-ray-loud blazars
Short Name:
J/A+A/436/799
Date:
21 Oct 2021
Publisher:
CDS
Description:
We determined the basic parameters, such as the central black hole mass (M), the boosting factor (or Doppler factor) ({delta}) the propagation angle ({Phi}) and the distance along the axis to the site of {gamma}-ray production (d) for 23 {gamma}-ray-loud blazars using their available variability timescales.
1042. X and {gamma} spectral indexes of Fermi blazars
ID:
ivo://CDS.VizieR/J/ApJ/761/125
Title:
X and {gamma} spectral indexes of Fermi blazars
Short Name:
J/ApJ/761/125
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, a sample of 451 blazars (193 flat spectrum radio quasars (FSRQs), 258 BL Lacertae objects) with corresponding X-ray and Fermi {gamma}-ray data is compiled to investigate the correlation both between the X-ray spectral index and the {gamma}-ray spectral index and between the spectral index and the luminosity, and to compare the spectral indexes {alpha}_X_, {alpha}_{gamma}_, {alpha}_X{gamma}_, and {alpha}_{gamma}X{gamma}_ for different subclasses. We also investigated the correlation between the X-ray and the {gamma}-ray luminosity.
1043. Xinglong spectra of two changing-look SDSS AGNs
ID:
ivo://CDS.VizieR/J/ApJ/887/15
Title:
Xinglong spectra of two changing-look SDSS AGNs
Short Name:
J/ApJ/887/15
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report a spectroscopic identification of two new changing-look active galactic nuclei (CL-AGNs): SDSSJ104705.16+544405.8 and SDSSJ120447.91+170256.8, both with a "turn-off" type transition from type-1 to type-1.8/1.9. The identification is arrived at through a follow-up spectroscopic observation of the five CL-AGNs candidates that are extracted from the sample recently released in MacLeod+ (2019, J/ApJ/874/8). The candidates are extracted by the authors from the Sloan Digit Sky Survey Data Release 7, and are spectroscopically confirmed quasars with large amplitude variability. By compiling a sample of 26 previously identified CL-AGNs, we confirm the claim by MacLeod+ that CL-AGNs tend to be biased against a low Eddington ratio, and identify an overlap between the CL-AGNs at their dim state and the so-called intermediate-type AGNs. The overlap implies that there two populations of the intermediate-type AGNs with different origins. One is due to the torus orientation effect, and the other to the intrinsic change of the accretion rate of the central supermassive black holes.
1044. XMDS/VVDS 4{sigma} catalogue
ID:
ivo://CDS.VizieR/J/A+A/439/413
Title:
XMDS/VVDS 4{sigma} catalogue
Short Name:
J/A+A/439/413
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalogue of 286 X-ray sources with their optical identification taken from the XMDS survey (using the XMM-Newton EPIC instrument). This first version is limited to sources detected at 4{sigma} at least in one energy band, AND falling in the area covered by the optical VVDS survey.
1045. XMM-COSMOS Type 1 AGNs
ID:
ivo://CDS.VizieR/J/A+A/512/A34
Title:
XMM-COSMOS Type 1 AGNs
Short Name:
J/A+A/512/A34
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of the X-ray to optical properties of a sample of 545 X-ray selected Type 1 AGN, from the XMM-COSMOS survey, over a wide range of redshifts (0.04<z<4.25) and X-ray luminosities (40.6<=LogL[2-10]keV<=45.3). About 60% of them are spectroscopically identified Type 1 AGN, while the others have a reliable photometric redshift and are classified as Type 1 AGN on the basis of their multi-band Spectral Energy Distributions. We discuss the relationship between UV and X-ray luminosity, as parameterized by the alpha_ox_ spectral slope, and its dependence on redshift and luminosity.
1046. 3XMM-DR4 QSO candidates at 3<z<5.5
ID:
ivo://CDS.VizieR/J/PAZh/42/313
Title:
3XMM-DR4 QSO candidates at 3<z<5.5
Short Name:
J/PAZh/42/313
Date:
21 Oct 2021
Publisher:
CDS
Description:
A catalog of quasar candidates at redshifts 3<z<5.5 is presented. These candidates have been selected among X-ray sources in the XMM-Newton Serendipitous Source Catalog (3XMM-DR4) in the 0.5-2keV band, located at high galactic latitudes |b|>20deg in the Sloan Digital Sky Survey (SDSS) area. The total overlapping area is about 300 sq. deg. The SDSS, 2MASS and WISE photometric catalogs were used. Only SDSS point sources were considered. X-ray sources having an optical counterpart with magnitude error in SDSS z band of less than 0.2 and color i-z<0.6 were chosen. Their photometric redshifts were determined with the EAZY code using a library of spectral templates. A sample of quasar candidates with photometric redshifts in the range 2.75<z<5.5 has been composed. Objects whose spectral energy distributions are better described by stellar templates have been excluded. The selection completeness of known quasars is about 80%. The normalized median absolute deviation of the differences between the photometric and spectroscopic redshifts of known quasars is 0.07 (with 9% outliers). The sky density of quasar candidates in our sample is 1.5 times that of the spectroscopic SDSS sample in the same fields. Follow-up spectroscopy should clarify the purity of the sample.
1047. 3XMM-DR4 QSO candidates optical spectroscopy
ID:
ivo://CDS.VizieR/J/PAZh/45/464
Title:
3XMM-DR4 QSO candidates optical spectroscopy
Short Name:
J/PAZh/45/464
Date:
22 Feb 2022
Publisher:
CDS
Description:
We present the results of optical spectroscopy for 58 quasar candidates at photometric redshifts z>~3, 57 of which enter into the Khorunzhev et al. (2016, Cat. J/PAZh/42/313) catalog (K16). This is a catalog of quasar candidates and known type 1 quasars selected among the X-ray sources of the 3XMM-DR4 catalog of the XMM-Newton serendipitous survey. At first we have performed spectroscopy for a quasi-random sample of 19 candidates at the 1.6-m AZT-33IK telescope of the Sayan Solar Observatory and the 6-m BTA telescope of the Special Astrophysical Observatory (SAO RAS). Then we have continued the observation for 39 X-ray bright candidates that could be used for the X-ray luminosity function construction (see Khorunzhev et al. 2018AstL...44..500K). The spectra at AZT-33IK were taken with the new low- and medium-resolution ADAM spectrograph that was produced and installed on the telescope in 2015. One of the most distant (z=5.08) optically bright (i=21) quasars ever detected in X-ray surveys has been discovered.
1048. XMM-LSS field X-ray sources classification
ID:
ivo://CDS.VizieR/J/A+A/557/A81
Title:
XMM-LSS field X-ray sources classification
Short Name:
J/A+A/557/A81
Date:
21 Oct 2021
Publisher:
CDS
Description:
The XMM-Large Scale Structure survey (XMM-LSS), covering an area of 11.1 sq. deg., contains more than 6000 X-ray point-like sources detected with XMM-Newton to a flux of 3x10^-15^erg/s/cm^2^ in the [0.5-2]keV band. The vast majority of these sources have optical (CFHTLS), infrared (SWIRE IRAC and MIPS), near-infrared (UKIDSS) and/or ultraviolet (GALEX) counterparts. We wish to investigate the environmental properties of the different types of the XMM-LSS X-ray sources by defining their environment using the i'-band CFHTLS W1 catalog of optical galaxies to a magnitude limit of 23.5mag. We have classified 4435 X-ray selected sources on the basis of their spectra, SEDs, and X-ray luminosity, and estimated their photometric redshifts, which have a 4-11 band photometry with an accuracy of sigma_dz_/(1+z_sp_)=0.076 with 22.6% outliers for i'<26mag. We estimated the local overdensities of 777 X-ray sources that have spectro-z or photo-z calculated by using more than seven bands (accuracy of sigma_dz_/(1+z_sp_)=0.061 with 13.8% outliers) within the volume-limited region defined by 0.1<z<0.85 and -23.5<M_i'_<-20. Although X-ray sources may be found in variety of environments, a high fraction (~55-60%), as verified by comparing with the random expectations, reside in overdense regions. The galaxy overdensities within which X-ray sources reside show a positive recent redshift evolution (at least for the range studied; z<0.85). We also find that X-ray selected galaxies, when compared to AGN, inhabit significantly higher galaxy overdensities, although their spatial extent appear to be smaller than that of AGN. Hard AGN (HR>-0.2) are located in more overdense regions than soft AGN (HR<-0.2), which is clearly seen in both redshift ranges, although it appears to be stronger in the higher redshift range (0.55<z<0.85). Furthermore, the galaxy overdensities (with {delta}>1.5) within which soft AGN are embedded appear to evolve more rapidly compared to the corresponding overdensities around hard AGN.
1049. XMM-LSS survey: AGN classifications
ID:
ivo://CDS.VizieR/J/A+A/474/473
Title:
XMM-LSS survey: AGN classifications
Short Name:
J/A+A/474/473
Date:
21 Oct 2021
Publisher:
CDS
Description:
Our goal is to characterize AGN populations by comparing their X-ray and optical classifications within the framework of the standard orientation-based unified scheme. We present a sample of 99 spectroscopically identified (R<=22mag) X-ray selected point sources in the XMM-LSS survey which are significantly detected (>=3{sigma}) in the [2-10]keV band with fluxes between 8x10^-15^ and 8x10^-14^erg/s/cm^2^, and which have more than 80 counts. We have compared their X-ray and optical classifications. To this end, we performed an X-ray spectral analysis for all of these 99 X-ray sources in order to assess whether they are intrinsically absorbed or not. The X-ray classification is based on the measured intrinsic column density. The optical classification is based on the measured FWHM of the permitted emission lines, the absence of broad lines being due to obscuration within the framework of the standard AGN unified scheme.
1050. XMM-Newton/2dF survey. IV.
ID:
ivo://CDS.VizieR/J/MNRAS/352/91
Title:
XMM-Newton/2dF survey. IV.
Short Name:
J/MNRAS/352/91
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of the X-ray spectral properties of 61 hard X-ray (2-8keV) selected sources from the bright XMM-Newton/2dF (f(2-8keV)>10^-14^erg/cm^2^/s) survey. This comprises nine XMMNewton pointings in the North Galactic Pole region (~1.6deg^2^) and overlaps with the SDSS, 2QZ and 2dFGRS surveys. Our sources contribute about 50 per cent of the 2-10keV X-ray background down to the flux limit of 10^-14^erg/cm^2^/s. The hardness ratio distribution of the sample suggests a deficit of heavily absorbed sources. Spectroscopic identifications exist for 34 sources.