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25201. X-ray sources <1 degree from Seyfert galaxies
ID:
ivo://CDS.VizieR/J/A+A/319/18
Title:
X-ray sources <1 degree from Seyfert galaxies
Short Name:
J/A+A/319/18
Date:
21 Oct 2021
Publisher:
CDS
Description:
Archived PSPC observations of 26 Seyfert galaxies have been analyzed for bright X-ray sources out to the full extent of the field (< about 50'). Of all Seyferts known this represents a sample 88% complete to B_T_=10mag, 74% complete to 11mag and 50% complete to 12mag. Using the same reduction algorithm, 14 fields centered on stars at high galactic latitudes have been used as control fields. Excluding the two brightest Seyferts, a subset of 24 Seyferts with corrected apparent magnitude between 8.04<B^o,i^_T_<12.90mag show a minimum excess of 46 bright X-ray sources generally distributed between 10 and 25' from the target galaxy. The significances of association of these sources with the Seyferts in the median brightness range are as high as 7.4-sigma.
25202. X-ray sources in A194 and A1060
ID:
ivo://CDS.VizieR/J/PASJ/58/931
Title:
X-ray sources in A194 and A1060
Short Name:
J/PASJ/58/931
Date:
21 Oct 2021
Publisher:
CDS
Description:
Two nearby clusters of galaxies, A194 (z=0.018) and A1060 (z=0.0114), have been analyzed for their X-ray point-source properties with XMM-Newton EPIC-PN data. A multi-band source detection technique was applied to both of the clusters, resulting in 46 sources from the A194 field and 32 sources from the A1060 field, respectively. The cumulative log(N)-log(S) for a flux limit of F_X_>=1x10^-14^erg/cm^2^/s was calculated and compared with that of the Lockman Hole. A ~3{sigma} excess of X-ray sources was found for the cluster regions.
25203. X-ray sources in CMa OB1
ID:
ivo://CDS.VizieR/J/A+A/609/A127
Title:
X-ray sources in CMa OB1
Short Name:
J/A+A/609/A127
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Canis Major OB1 association has an intriguing scenario of star formation, especially in the region called Canis Major R1 (CMa R1) traditionally assigned to a reflection nebula, but in reality an ionized region. This work is focussed on the young stellar population associated with CMa R1, for which our previous results from ROSAT, optical, and near-infrared data had revealed two stellar groups with different ages, suggesting a possible mixing of populations originated from distinct star formation episodes. The X-ray data allow the detected sources to be characterized according to hardness ratios, light curves, and spectra. Estimates of mass and age were obtained from the 2MASS catalogue and used to define a complete subsample of stellar counterparts for statistical purposes. A catalogue of 387 XMM-Newton sources is provided, of which 78% are confirmed as members or probable members of the CMa R1 association. Flares (or similar events) were observed for 13 sources and the spectra of 21 bright sources could be fitted by a thermal plasma model. Mean values of fits parameters were used to estimate X-ray luminosities. We found a minimum value of log(L_X_[erg/s])=29.43, indicating that our sample of low-mass stars (M*<=0.5 M_{sun}_), which are faint X-ray emitters, is incomplete. Among the 250 objects selected as our complete subsample (defining our "best sample"), 171 are found to the east of the cloud, near Z CMa and dense molecular gas, of which 50% of them are young (<5Myr) and 30% are older (>10Myr). The opposite happens to the west, near GU CMa, in areas lacking molecular gas: among 79 objects, 30% are young and 50% are older. These findings confirm that a first episode of distributed star formation occurred in the whole studied region ~10Myr ago and dispersed the molecular gas, while a second, localized episode (<5Myr) took place in the regions where molecular gas is still present.
25204. X-ray sources in Cyg OB2 region
ID:
ivo://CDS.VizieR/J/ApJS/184/84
Title:
X-ray sources in Cyg OB2 region
Short Name:
J/ApJS/184/84
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalogue of 1696 X-ray sources detected in the massive star forming region (SFR) Cygnus OB2 and extracted from two archival Chandra observations of the center of the region. A deep source extraction routine, exploiting the low background rates of Chandra observations was employed to maximize the number of sources extracted. Observations at other wavelengths were used to identify low count-rate sources and remove likely spurious sources. Monte Carlo simulations were also used to assess the authenticity of these sources. X-ray spectra were fitted with thermal plasma models to characterize the objects and X-ray light curves were analyzed to determine their variability. We used a Bayesian technique to identify optical or near-IR counterparts for 1501 (89%) of our sources, using deep observations from the INT Photometric H-alpha Survey, the Two Micron All Sky Survey, and the UKIRT Infrared Deep Sky Survey-Galactic plane Survey. 755 (45%) of these objects have six-band r', H-alpha, i', J, H, and K optical and near-IR photometry. From an analysis of the Poisson false-source probabilities for each source we estimate that our X-ray catalogue includes <1% of false sources, and an even lower fraction when only sources with optical or near-IR associations are considered. A Monte Carlo simulation of the Bayesian matching scheme allows this method to be compared to more simplified matching techniques and enables the various sources of error to be quantified. The catalogue of 1696 objects presented here includes X-ray broad band fluxes, model fits, and optical and near-IR photometry in what is one of the largest X-ray catalogue of a single SFR to date. The high number of stellar X-ray sources detected from relatively shallow observations confirms the status and importance of Cygnus OB2 as one of our Galaxy's most massive SFRs.
25205. X-ray sources in Galactic Center
ID:
ivo://CDS.VizieR/J/ApJ/613/1179
Title:
X-ray sources in Galactic Center
Short Name:
J/ApJ/613/1179
Date:
21 Oct 2021
Publisher:
CDS
Description:
We examine the X-ray spectra and variability of the sample of X-ray sources with L_X_~10^31^-10^33^ergs/s identified within the inner 9' of the Galaxy by Muno et al. Very few of the sources exhibit intraday or intermonth variations.
25206. X-ray sources in galaxy pairs
ID:
ivo://CDS.VizieR/J/AJ/133/220
Title:
X-ray sources in galaxy pairs
Short Name:
J/AJ/133/220
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a comprehensive study of the local environments of four elliptical+spiral (E+S) galaxy pairs with the main goal of investigating their formation/evolution histories. We obtained new XMM-Newton data for two pairs (RR 143 and RR 242) that complement existing ROSAT data for the other two (RR 210 and RR 216).
25207. X-ray sources in Hickson Compact Groups
ID:
ivo://CDS.VizieR/J/ApJS/212/9
Title:
X-ray sources in Hickson Compact Groups
Short Name:
J/ApJS/212/9
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Chandra X-ray point source catalogs for 9 Hickson Compact Groups (HCGs, 37 galaxies) at distances of 34-89Mpc. We perform detailed X-ray point source detection and photometry and interpret the point source population by means of simulated hardness ratios. We thus estimate X-ray luminosities (L_X_) for all sources, most of which are too weak for reliable spectral fitting. For all sources, we provide catalogs with counts, count rates, power-law indices ({Gamma}), hardness ratios, and L_X_, in the full (0.5-8.0keV), soft (0.5-2.0keV), and hard (2.0-8.0keV) bands. We use optical emission-line ratios from the literature to re-classify 24 galaxies as star-forming, accreting onto a supermassive black hole (AGNs), transition objects, or low-ionization nuclear emission regions. Two-thirds of our galaxies have nuclear X-ray sources with Swift/UVOT counterparts. Two nuclei have L_X,0.5-8.0keV_>10^42^erg/s, are strong multi-wavelength active galactic nuclei (AGNs), and follow the known {alpha}_OX_-{nu}L_{nu}(nearUV)_ correlation for strong AGNs. Otherwise, most nuclei are X-ray faint, consistent with either a low-luminosity AGN or a nuclear X-ray binary population, and fall in the "non-AGN locus" in {alpha}_OX_-{nu}L_{nu}(nearUV)_ space, which also hosts other normal galaxies. Our results suggest that HCG X-ray nuclei in high specific star formation rate spiral galaxies are likely dominated by star formation, while those with low specific star formation rates in earlier types likely harbor a weak AGN. The AGN fraction in HCG galaxies with M_R_<=-20 and L_X,0.5-8.0keV_>=10^41^erg/s is 0.08_-0.01_^+0.35^, somewhat higher than the ~5% fraction in galaxy clusters.
25208. X-ray sources in IC 348 from Chandra
ID:
ivo://CDS.VizieR/J/AJ/122/866
Title:
X-ray sources in IC 348 from Chandra
Short Name:
J/AJ/122/866
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained a deep (53 ks) X-ray image of the very young stellar cluster IC 348 with the Advanced CCD Imaging Spectrometer on board the Chandra X-Ray Observatory. In our image with a sensitivity limit of ~1x10^28^ergs/s (more than 10 times deeper than our ROSAT images of IC 348), 215 X-ray sources are detected. While 115 of these sources can be identified with known cluster members, 58 X-ray sources are most likely new, still unidentified cluster members. About 80% of all known cluster members with masses between ~0.15 and 2M_{sun}_ are visible as X-ray sources in our image. We discover X-ray emission at levels of ~10^28^ergs/s from four of 13 known brown dwarfs and from three of 12 brown dwarf candidates in IC 348. We also detect X-ray emission from two deeply embedded objects, presumably class I protostars, south of the cluster center. Description:
25209. X-ray sources in IC 1396N
ID:
ivo://CDS.VizieR/J/ApJ/654/316
Title:
X-ray sources in IC 1396N
Short Name:
J/ApJ/654/316
Date:
21 Oct 2021
Publisher:
CDS
Description:
The IC 1396N cometary globule (CG) within the large nearby HII region IC 1396 has been observed with the ACIS detector on board the Chandra X-Ray Observatory. We detect 117 X-ray sources, of which ~50-60 are likely members of the young open cluster Trumpler 37 dispersed throughout the HII region, and 25 are associated with young stars formed within the globule. Infrared photometry (2MASS and Spitzer) shows that the X-ray population is very young: 3 older Class III stars, 16 classical T Tauri stars, and 6 protostars including a Class 0/I system.
25210. X-ray sources in M104
ID:
ivo://CDS.VizieR/J/ApJ/599/1067
Title:
X-ray sources in M104
Short Name:
J/ApJ/599/1067
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the population of point sources discovered during an 18.5ks Chandra ACIS-S observation of the Sombrero galaxy. We present the luminosity function and the spectra of the six brightest sources, consider correlations with globular clusters (GCs) and with planetary nebulae, and study the galaxy's population of very soft sources. We detected 122 sources. Twenty-two sources are identified as very soft; of these, five appear to be classical luminous supersoft X-ray sources (SSSs), while 17 may belong to the slightly harder class referred to as quasi-soft (QSSs). There is an overdensity of very soft sources within 2kpc of the nucleus, which is itself the brightest X-ray source. Very soft sources are also found in the disk and halo, with one QSS in a globular cluster (GC).

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