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17891. X-ray study of the young cluster NGC6231
ID:
ivo://CDS.VizieR/J/A+A/596/A82
Title:
X-ray study of the young cluster NGC6231
Short Name:
J/A+A/596/A82
Date:
21 Oct 2021
Publisher:
CDS
Description:
NGC 6231 is a massive young star cluster, near the center of the Sco OB1 association. While its OB members are well studied, its low-mass population has received little attention. We present high-spatial resolution Chandra ACIS-I X-ray data, where we detect 1613 point X-ray sources. Our main aim is to clarify global properties of NGC 6231 down to low masses through a detailed membership assessment, and to study the cluster stars' spatial distribution, the origin of their X-ray emission, the cluster age and formation history, and initial mass function. We use X-ray data, complemented by optical and IR data, to establish cluster membership. The spatial distribution of different stellar subgroups also provides highly significant constraints on cluster membership, as does the distribution of X-ray hardness. We perform spectral modelling of group-stacked X-ray source spectra.
17892. X-ray supernova remnants in LMC
ID:
ivo://CDS.VizieR/J/A+A/585/A162
Title:
X-ray supernova remnants in LMC
Short Name:
J/A+A/585/A162
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a comprehensive X-ray study of the population of supernova remnants (SNRs) in the Large Magellanic Cloud (LMC). Using primarily XMM-Newton observations, we conduct a systematic spectral analysis of LMC SNRs to gain new insight into their evolution and the interplay with their host galaxy. We combined all the archival XMM-Newton observations of the LMC with those of our Very Large Programme LMC survey. We produced X-ray images and spectra of 51 SNRs, out of a list of 59 objects compiled from the literature and augmented with newly found objects. Using a careful modelling of the background, we consistently analysed all the X-ray spectra and measure temperatures, luminosities, and chemical compositions. The locations of SNRs are compared to the distributions of stars, cold gas, and warm gas in the LMC, and we investigated the connection between the SNRs and their local environment, characterised by various star formation histories. We tentatively typed all LMC SNRs, in order to constrain the ratio of core-collapse to type Ia SN rates in the LMC. We also compared the column densities derived from X-ray spectra to HI maps, thus probing the three-dimensional structure of the LMC. This work provides the first homogeneous catalogue of the X-ray spectral properties of SNRs in the LMC. It offers a complete census of LMC remnants whose X-ray emission exhibits Fe K lines (13% of the sample), or reveals the contribution from hot supernova ejecta (39%), which both give clues to the progenitor types. The abundances of O, Ne, Mg, Si, and Fe in the hot phase of the LMC interstellar medium are found to be between 0.2 and 0.5 times the solar values with a lower abundance ratio [{alpha}/Fe] than in the Milky Way. The current ratio of core-collapse to type Ia SN rates in the LMC is constrained to N_CC_/N_Ia_=1.35(_-0.24_^+0.11^), which is lower than in local SN surveys and galaxy clusters. Our comparison of the X-ray luminosity functions of SNRs in Local Group galaxies (LMC, SMC, M31, and M33) reveals an intriguing excess of bright objects in the LMC. Finally, we confirm that 30 Doradus and the LMC Bar are offset from the main disc of the LMC to the far and near sides, respectively.
17893. X-ray survey of NGC7000/IC5070
ID:
ivo://CDS.VizieR/J/A+A/602/A115
Title:
X-ray survey of NGC7000/IC5070
Short Name:
J/A+A/602/A115
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first extensive X-ray study of the North-America and Pelican star-forming region (NGC7000/IC5070), with the aim of finding and characterizing the young population of this cloud. X-ray data from Chandra (four pointings) and XMM-Newton (seven pointings) were reduced and source detection algorithm applied to each image. We complement the X-ray data with optical and near-IR data from the IPHAS, UKIDSS, and 2MASS catalogs, and with other published optical and Spitzer IR data. More than 700 X-ray sources are detected, the majority of which have an optical or NIR counterpart. This allowed us to identify young stars in different stages of formation. Less than 30% of X-ray sources are identified with a previously known young star. We argue that most X-ray sources with an optical or NIR counterpart, except perhaps for a few tens at near-zero reddening, are likely candidate members of the star-forming region, on the basis of both their optical and NIR magnitudes and colors, and of X-ray properties such as spectrum hardness or flux variations. They are characterized by a wide range of extinction, and sometimes near-IR excesses, both of which prevent derivation of accurate stellar parameters. The optical color-magnitude diagram suggests ages between 1-10Myrs. The X-ray members have a very complex spatial distribution with some degree of subclustering, qualitatively similar to that of previously known members. The detailed distribution of X-ray sources relative to the objects with IR excesses identified with Spitzer is sometimes suggestive of sequential star formation, especially near the 'Gulf of Mexico' region, probably triggered by the O5 star which illuminates the whole region. We confirm that around the O5 star no enhancement in the young star density is found, in agreement with previous results. Thanks to the precision and depth of the IPHAS and UKIDSS data used, we also determine the local optical-IR reddening law, and compute an updated reddening map of the entire region.
17894. X-ray survey of the Galactic Bulge (CXOGBS)
ID:
ivo://CDS.VizieR/J/ApJS/210/18
Title:
X-ray survey of the Galactic Bulge (CXOGBS)
Short Name:
J/ApJS/210/18
Date:
21 Oct 2021
Publisher:
CDS
Description:
We provide the Chandra source list for the last ~quarter of the area covered by the Galactic Bulge Survey (GBS). The GBS targets two strips of 6x1{deg} (12sq.deg. in total), one above (1<{deg}b<2{deg}) and one below (-2{deg}<b<-1{deg}) the Galactic plane in the direction of the Galactic Center at X-ray, optical and near-infrared wavelengths. For the X-ray part of the survey we use 2ks per Chandra pointing. We find 424 X-ray sources in the 63 Chandra observations we report on here. These sources are in addition to the 1216 X-ray sources discovered in the first part of the GBS survey described before. We discuss the characteristics and the X-ray variability of the brightest of the sources as well as the radio properties from existing radio surveys. We point out an interesting asymmetry in the number of X-ray sources as a function of their Galactic l and b coordinates which is probably caused by differences in average extinction towards the different parts of the GBS survey area.
17895. X-ray survey of the 2Jy sample. I.
ID:
ivo://CDS.VizieR/J/MNRAS/440/269
Title:
X-ray survey of the 2Jy sample. I.
Short Name:
J/MNRAS/440/269
Date:
21 Oct 2021
Publisher:
CDS
Description:
We carry out a systematic study of the X-ray emission from the active nuclei of the 0.02<z<0.7 2Jy sample, using Chandra and XMM-Newton observations. We combine our results with those from mid-infrared, optical emission-line and radio observations, and add them to those of the 3CRR sources. We show that the low-excitation objects in our samples show signs of radiatively inefficient accretion. We study the effect of the jet-related emission on the various luminosities, confirming that it is the main source of soft X-ray emission for our sources. We also find strong correlations between the accretion-related luminosities, and identify several sources whose optical classification is incompatible with their accretion properties. We derive the bolometric and jet kinetic luminosities for the samples and find a difference in the total Eddington rate between the low- and high-excitation populations, with the former peaking at ~1% and the latter at ~20% Eddington. Our results are consistent with a simple Eddington switch when the effects of environment on radio luminosity and black hole mass calculations are considered. The apparent independence of jet kinetic power and radiative luminosity in the high-excitation population in our plots supports a model in which jet production and radiatively efficient accretion are not strongly correlated in high-excitation objects, though they have a common underlying mechanism.
17896. 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.
17897. X-ray survey of YSOs in Orion A
ID:
ivo://CDS.VizieR/J/ApJ/768/99
Title:
X-ray survey of YSOs in Orion A
Short Name:
J/ApJ/768/99
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an XMM-Newton survey of the part of the Orion A cloud south of the Orion Nebula. This survey includes the Lynds 1641 (L1641) dark cloud, a region of the Orion A cloud with very few massive stars and hence a relatively low ambient UV flux, and the region around the O9III star {iota} Orionis. In addition to proprietary data, we used archival XMM data of the Orion Nebula Cluster (ONC) to extend our analysis to a major fraction of the Orion A cloud. We have detected 1060 X-ray sources in L1641 and the {iota} Ori region. About 94% of the sources have Two Micron All Sky Survey and Spitzer counterparts, 204 and 23 being Class II and Class I or protostar objects, respectively. In addition, we have identified 489 X-ray sources as counterparts to Class III candidates, given they are bright in X-rays and appear as normal photospheres at mid-IR wavelengths. The remaining 205 X-ray sources are likely distant active galactic nuclei or other galactic sources not related to Orion A. We find that Class III candidates appear more concentrated in two main clusters in L1641. The first cluster of Class III stars is found toward the northern part of L1641, concentrated around {iota} Ori. The stars in this cluster are more evolved than those in the Orion Nebula. We estimate a distance of 300-320 pc for this cluster showing that it is in the foreground of the Orion A cloud. Another cluster rich in Class III stars is located in L1641 South and appears to be a slightly older cluster embedded in the Orion A cloud. Furthermore, other evolved Class III stars are found north of the ONC toward NGC 1977.
17898. 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.
17899. 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.
17900. 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.

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