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17881. X-ray spectra in 13^H^ XMM/Chandra deep field
ID:
ivo://CDS.VizieR/J/MNRAS/369/156
Title:
X-ray spectra in 13^H^ XMM/Chandra deep field
Short Name:
J/MNRAS/369/156
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the X-ray spectra of 86 optically identified sources in the 13^H^ XMM-Newton/Chandra deep field which have >70 X-ray counts. The majority of these sources have 2-10keV fluxes between 10-15 and 5x10^-14^erg/cm^2^/s. The sample consists of 50 broad-line active galactic nuclei (BLAGN), 25 narrow emission-line galaxies (NELGs), six absorption-line galaxies and five Galactic stars. The majority (42/50) of the BLAGN have X-ray spectra which are consistent with a power-law shape.
17882. X-ray spectral analysis of AGNs
ID:
ivo://CDS.VizieR/J/MNRAS/443/1999
Title:
X-ray spectral analysis of AGNs
Short Name:
J/MNRAS/443/1999
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results from an X-ray spectral analysis of active galactic nuclei (AGN) in the Chandra Deep Field-South, All-wavelength Extended Groth-strip International Survey (AEGIS)-Deep X-ray survey (XD) and Chandra-Cosmic Evolution Surveys (COSMOS), focusing on the identification and characterization of the most heavily obscured, Compton thick (CT, NH>10^24^cm^-2^) sources. Our sample is comprised of 3184 X-ray selected extragalactic sources, which has a high rate of redshift completeness (96.6 per cent), and includes additional spectroscopic redshifts and improved photometric redshifts over previous studies. We use spectral models designed for heavily obscured AGN which self-consistently include all major spectral signatures of heavy absorption. We validate our spectral fitting method through simulations, identify CT sources not selected through this method using X-ray colours and take considerations for the constraints on NH given the low count nature of many of our sources. After these considerations, we identify a total of 100 CT AGN with best-fitting NH >10^24^cm^-2^ and NH constrained to be above 10^23.5^cm^-2^ at 90 per cent confidence. These sources cover an intrinsic 2-10keV X-ray luminosity range of 10^42^-3x10^45^erg/s and a redshift range of z=0.1-4. This sample will enable characterization of these heavily obscured AGN across cosmic time and to ascertain their cosmological significance. These survey fields are sites of extensive multiwavelength coverage, including near-infrared Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) data and far-infrared Herschel data, enabling forthcoming investigations into the host properties of CT AGN. Furthermore, by using the torus models to test different covering factor scenarios, and by investigating the inclusion of the soft scattered emission, we find evidence that the covering factor of the obscuring material decreases with LX for all redshifts, consistent with the receding torus model, and that this factor increases with redshift, consistent with an increase in the obscured fraction towards higher redshifts. The strong relationship between the parameters of obscuration and LX points towards an origin intrinsic to the AGN; however, the increase of the covering factor with redshift may point towards contributions to the obscuration by the host galaxy. We make NH, {GAMMA} (with uncertainties), observed X-ray fluxes and intrinsic 2-10keV luminosities for all sources analysed in this work publicly available in an online catalogue.
17883. X-ray spectral analysis of 107 MW sight lines
ID:
ivo://CDS.VizieR/J/ApJ/862/34
Title:
X-ray spectral analysis of 107 MW sight lines
Short Name:
J/ApJ/862/34
Date:
21 Oct 2021
Publisher:
CDS
Description:
The formation mechanism of the hot gaseous halo associated with the Milky Way is still under debate. We report new observational constraints on the gaseous halo using 107 lines of sight of the Suzaku X-ray observations at 75{deg}<l<285{deg} and |b|>15{deg} with a total exposure of 6.4Ms. The gaseous halo spectra are represented by a single-temperature plasma model in collisional ionization equilibrium. The median temperature of the observed fields is 0.26keV (3.0x10^6^K) with a typical fluctuation of ~30%. The emission measure varies by an order of magnitude and marginally correlates with the Galactic latitude. Despite the large scatter of the data, the emission measure distribution is roughly reproduced by a disk-like density distribution with a scale length of ~7kpc, a scale height of ~2kpc, and a total mass of ~5x10^7^M_{sun}_. In addition, we found that a spherical hot gas with the {beta}-model profile hardly contributes to the observed X-rays but that its total mass might reach >~10^9^M_{sun}_. Combined with indirect evidence of an extended gaseous halo from other observations, the hot gaseous halo likely consists of a dense disk-like component and a rarefied spherical component; the X-ray emissions primarily come from the former, but the mass is dominated by the latter. The disk-like component likely originates from stellar feedback in the Galactic disk due to the low scale height and the large scatter of the emission measures. The median [O/Fe] of ~0.25 shows the contribution of the core-collapse supernovae and supports the stellar feedback origin.
17884. 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.
17885. 126 X-rays sources around the cepheid {eta} Aql
ID:
ivo://CDS.VizieR/J/AJ/162/92
Title:
126 X-rays sources around the cepheid {eta} Aql
Short Name:
J/AJ/162/92
Date:
14 Mar 2022 07:02:20
Publisher:
CDS
Description:
X-ray bursts have recently been discovered in the Cepheids {delta}Cep and {beta}Dor modulated by the pulsation cycle. We have obtained an observation of the Cepheid {eta}Aql with the XMM-Newton satellite at the phase of maximum radius; the phase at which there is a burst of X-rays in {delta}Cep. No X-rays were seen from the Cepheid {eta}Aql at this phase, and the implications for Cepheid upper atmospheres are discussed. We have also used the combination of X-ray sources, as well as Gaia and 2MASS data, to search for a possible grouping around the young intermediate mass Cepheid. No indication of such a group was found.
17886. X-rays sources in Trumpler 37
ID:
ivo://CDS.VizieR/J/MNRAS/426/2917
Title:
X-rays sources in Trumpler 37
Short Name:
J/MNRAS/426/2917
Date:
21 Oct 2021
Publisher:
CDS
Description:
Rich young stellar clusters produce HII regions whose expansion into the nearby molecular cloud is thought to trigger the formation of new stars. However, the importance of this mode of star formation is uncertain. This investigation seeks to quantify triggered star formation (TSF) in IC 1396A (aka the Elephant Trunk Nebula), a bright-rimmed cloud (BRC) on the periphery of the nearby giant HII region IC 1396 produced by the Trumpler 37 cluster. X-ray selection of young stars from Chandra X-ray Observatory data is combined with existing optical and infrared surveys to give a more complete census of the TSF population. Over 250 young stars in and around IC 1396A are identified; this doubles the previously known population. A spatio-temporal gradient of stars from the IC 1396A cloud towards the primary ionizing star HD 206267 is found.
17887. X-ray star clusters in the Carina complex
ID:
ivo://CDS.VizieR/J/ApJS/194/9
Title:
X-ray star clusters in the Carina complex
Short Name:
J/ApJS/194/9
Date:
21 Oct 2021
Publisher:
CDS
Description:
The distribution of young stars found in the Chandra Carina Complex Project (CCCP) is examined for clustering structure. X-ray surveys are advantageous for identifying young stellar populations compared to optical and infrared surveys in suffering less contamination from nebular emission and Galactic field stars. The analysis is based on smoothed maps of a spatially complete subsample of ~3000 brighter X-ray sources classified as Carina members and ~10000 stars from the full CCCP sample. The principal known clusters are recovered, and some additional smaller groups are identified. No rich embedded clusters are present, although a number of sparse groups are found. The CCCP reveals considerable complexity in clustering properties.
17888. X-ray studies of stars in the Pleiades
ID:
ivo://CDS.VizieR/J/ApJ/348/557
Title:
X-ray studies of stars in the Pleiades
Short Name:
J/ApJ/348/557
Date:
21 Oct 2021
Publisher:
CDS
Description:
Coronal X-ray emission of the Pleiades stars is investigated, and maximum likelihood, integral X-ray luminosity functions are computed for Pleiades members in selected color-index ranges. A detailed search is conducted for long-term variability in the X-ray emission of those stars observed more than once. An overall comparison of the survey results with those of previous surveys confirms the ubiquity of X-ray emission in the Pleiades cluster stars and its higher rate of emission with respect to older stars. It is found that the X-ray emission from dA and early dF stars cannot be proven to be dissimilar to that of Hyades and field stars of the same spectral type. The Pleiades cluster members show a real rise of the X-ray luminosity from dA stars to early dF stars. X-ray emission for the young, solar-like Pleiades stars is about two orders of magnitude more intense than for the nearby solar-like stars.
17889. X-ray study of NGC 2451 A and B.
ID:
ivo://CDS.VizieR/J/A+A/402/571
Title:
X-ray study of NGC 2451 A and B.
Short Name:
J/A+A/402/571
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have conducted a detailed study of the object NGC 2451, which actually consists of two different open clusters A and B along the same line of sight at 206pc and 370pc distance, respectively. Although belonging to the nearest clusters, they have not been much investigated until present due to strong contamination by field stars. ROSAT X-ray observations and optical UBVR photometry are used to identify cluster members by means of X-ray emission and colour-magnitude diagrams. The identified stars concentrate nicely around the expected main sequences in the colour-magnitude diagram at the distances derived from astrometric investigations. Altogether, 39 stars are identified as member candidates of the nearer cluster A, 49 stars as member candidates of the more distant cluster B, and 22 faint stars are probably members of either of the two clusters, but due to large errors it is not clear to which one they belong. Further 40 stars identified with X-ray sources are probably non-members. For the first time, the range of known probable cluster members of NGC 2451 A and B has been extended downwards the main sequence to stars of spectral class M. Isochrone fitting yields an age of 50 to 80Myrs for NGC 2451 A and =~50Myrs for NGC 2451 B, consistent with the X-ray luminosity distribution functions, which are comparable to other clusters in the same age range. Except from the occurence of four flares, the stars of both clusters do not show strong long-term X-ray variability exceeding a factor 5 over a time span of 1 to 3 years.
17890. X-ray study of star-forming region NGC 6357
ID:
ivo://CDS.VizieR/J/ApJS/168/100
Title:
X-ray study of star-forming region NGC 6357
Short Name:
J/ApJS/168/100
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first high spatial resolution X-ray study of the massive star-forming region NGC 6357, obtained in a 38ks Chandra/ACIS observation. Inside the brightest constituent of this large HII region complex is the massive open cluster Pismis 24. It contains two of the brightest and bluest stars known, yet remains poorly studied; only a handful of optically bright stellar members have been identified. We investigate the cluster extent and initial mass function and detect ~800 X-ray sources with a limiting sensitivity of ~10^30^ergs/s; this provides the first reliable probe of the rich intermediate-mass and low-mass population of this massive cluster, increasing the number of known members from optical study by a factor of ~50.

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