- ID:
- ivo://CDS.VizieR/J/ApJ/591/138
- Title:
- Chandra X-ray sources of NGC 1068
- Short Name:
- J/ApJ/591/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the compact X-ray source population in the Seyfert 2 galaxy NGC 1068, imaged with a 50ks Chandra observation. We find a total of 84 compact sources on the S3 chip, of which 66 are located within the 25.0B-mag/arcsec^2^ isophote of the galactic disk of NGC 1068. Spectra have been obtained for the 21 sources with at least 50 counts and modeled with both multicolor disk blackbody and power-law models.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/736/90
- Title:
- Chandra X-ray sources of NGC 1399
- Short Name:
- J/ApJ/736/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a wide-field study of the globular cluster (GC)/low-mass X-ray binary (LMXB) connection in the giant elliptical NGC 1399. The large field of view of the Advanced Camera for Surveys/WFC, combined with Hubble Space Telescope and Chandra high resolution, allow us to constrain the LMXB formation scenarios in elliptical galaxies. We confirm that NGC 1399 has the highest LMXB fraction in GCs of all nearby elliptical galaxies studied so far, even though the exact value depends on galactocentric distance due to the interplay of a differential GC versus galaxy light distribution and the GC color dependence. In fact, LMXBs are preferentially hosted by bright, red GCs out to >5R_eff_ of the galaxy light. The finding that GCs hosting LMXBs follow the radial distribution of their parent GC population argues against the hypothesis that the external dynamical influence of the galaxy affects the LMXB formation in GCs. On the other hand, field-LMXBs closely match the host galaxy light, thus indicating that they are originally formed in situ and not inside GCs. We measure GC structural parameters, finding that the LMXB formation likelihood is influenced independently by mass, metallicity, and GC structural parameters. In particular, the GC central density plays a major role in predicting which GCs host accreting binaries. Finally, our analysis shows that LMXBs in GCs are marginally brighter than those in the field, and in particular the only color-confirmed GC with L_X_>10^39^erg/s shows no variability, which may indicate a superposition of multiple LMXBs in these systems.
- ID:
- ivo://CDS.VizieR/J/ApJ/589/225
- Title:
- Chandra X-ray sources toward Galactic Center
- Short Name:
- J/ApJ/589/225
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 2357 point sources detected during 590ks of Chandra observations of the 17x17' field around Sgr A*. This field encompasses a physical area of 40x40pc at a distance of 8kpc. The completeness limit of the sample at the Galactic center is 10^31^erg/s (2.0-8.0keV), while the detection limit is an order of magnitude lower. The 281 sources detected below 1.5keV are mainly in the foreground of the Galactic center, while comparisons to the Chandra deep fields at high Galactic latitudes suggest that only about 100 of the observed sources are background AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJ/709/241
- Title:
- Characterisation of X-rays sources in NGC 6397
- Short Name:
- J/ApJ/709/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep Chandra X-ray Observatory study of the peculiar binary radio millisecond pulsar (MSP) PSR J1740-5340 and candidate millisecond pulsars in the globular cluster NGC 6397. The X-rays from PSR J1740-5340 appear to be non-thermal and exhibit variability at the binary period. These properties suggest the presence of a relativistic intrabinary shock formed due to interaction of a relativistic rotation-powered pulsar wind and outflow from the unusual "red-straggler/sub-subgiant" companion. We find the X-ray source U18 to show similar X-ray and optical properties to those of PSR J1740-5340, making it a strong MSP candidate. It exhibits variability on timescales from hours to years, also consistent with an intrabinary shock origin of its X-ray emission. The unprecedented depth of the X-ray data allows us to conduct a complete census of MSPs in NGC 6397. Based on the properties of the present sample of X-ray-detected MSPs in the Galaxy, we find that NGC 6397 probably hosts no more than six MSPs.
- ID:
- ivo://CDS.VizieR/J/A+AS/114/109
- Title:
- Cha X-ray sources & optical identifications
- Short Name:
- J/A+AS/114/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the observations of the ROSAT all-sky survey (RASS) in the direction of the Chamaeleon cloud complex, as well as the spectroscopic identifications of the detected X-ray sources. The main purpose of this identification program was the search for low mass pre-main sequence stars. Sixteen previously known PMS stars were detected with high confidence by ROSAT. Eight are classical T Tauri stars and eight are weak-line T Tauri stars. Seventy-seven new weak-line T Tauri stars were identified on the basis of the presence of strong Li {lambda}6707 absorption, spectral type later than F0 and chromospheric emission. We give coordinates and count rates of the X-ray sources, and present optical spectra and finding charts for the sources identified optically as new pre-main sequence stars. Optical UBV(RI)c and near-infrared JHKLM photometry for this sample of stars is also provided. In addition, 6 new dKe-dMe candidates are found among the RASS sources.
- ID:
- ivo://CDS.VizieR/J/A+A/637/A58
- Title:
- Chemical evolution of galaxy clusters
- Short Name:
- J/A+A/637/A58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the chemical evolution of galaxy clusters by measuring the iron mass in the ICM after dissecting the abundance profiles into different components. We used Chandra archival observations of 186 morphologically regular clusters in the redshift range of [0.04, 1.07]. For each cluster, we computed the azimuthally averaged iron abundance and gas density profiles. In particular, our aim is to identify a central peak in the iron distribution, which is associated with the central galaxy, and an approximately constant plateau reaching the largest observed radii, which is possibly associated with early enrichment that occurred before or shortly after achieving virialization within the cluster. We were able to firmly identify two components in the iron distribution in a significant fraction of the sample simply by relying on the fit of the iron abundance profile. From the abundance and ICM density profiles, we computed the iron mass included in the iron peak and iron plateau, and the gas mass-weighted iron abundance of the ICM out to an extraction radius of 0.4r_500_ and to r_500_ by extending the abundance profile as a constant. We find that the iron plateau shows no evolution with redshift. On the other hand, we find a marginal (<2{sigma} c.l.) decrease with redshift in the iron mass included in the iron peak rescaled by the gas mass. We measure that the fraction of iron peak mass is typically a few percent (~1%) of the total iron mass within r_500_. Therefore, since the total iron mass budget is dominated by the plateau, we find consistently that the global gas mass-weighted iron abundance does not evolve significantly across our sample. We were also able to reproduce past claims of evolution in the global iron abundance, which turn out to be due to the use of cluster samples with different selection methods combined with the use of emission-weighted, instead of gas mass-weighted, abundance values. Finally, while the intrinsic scatter in the iron plateau mass is consistent with zero, the iron peak mass exhibits a large scatter, in line with the fact that the peak is produced after the virialization of the halo and depends on the formation history of the hosting cool core and the strength of the associated feedback processes. We conclude that only a spatially resolved approach can resolve the issue of iron abundance evolution in the ICM, reconciling the contradictory results obtained in the last ten years. Evolutionary effects below z~1 are marginally measurable with present-day data, while at z>1 the constraints are severely limited by poor knowledge of the high-z cluster population. The path towards a full and comprehensive chemical history of the ICM requires the application of high angular resolution X-ray bolometers and a dramatic increase in the number of faint, extended X-ray sources.
- ID:
- ivo://CDS.VizieR/J/ApJS/212/13
- Title:
- ChIcAGO. I. Sample and initial results
- Short Name:
- J/ApJS/212/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Chasing the Identification of ASCA Galactic Objects (ChIcAGO) survey, which is designed to identify the unknown X-ray sources discovered during the ASCA Galactic Plane Survey (AGPS). Little is known about most of the AGPS sources, especially those that emit primarily in hard X-rays (2-10keV) within the F_x_~10^-13^ to 10^-11^erg/cm2/s X-ray flux range. In ChIcAGO, the subarcsecond localization capabilities of Chandra have been combined with a detailed multiwavelength follow-up program, with the ultimate goal of classifying the >100 unidentified sources in the AGPS. Overall to date, 93 unidentified AGPS sources have been observed with Chandra as part of the ChIcAGO survey. A total of 253 X-ray point sources have been detected in these Chandra observations within 3' of the original ASCA positions. We have identified infrared and optical counterparts to the majority of these sources, using both new observations and catalogs from existing Galactic plane surveys. X-ray and infrared population statistics for the X-ray point sources detected in the Chandra observations reveal that the primary populations of Galactic plane X-ray sources that emit in the F_x_~10^-13^ to 10^-11^ erg/cm2/s flux range are active stellar coronae, massive stars with strong stellar winds that are possibly in colliding wind binaries, X-ray binaries, and magnetars. There is also another primary population that is still unidentified but, on the basis of its X-ray and infrared properties, likely comprises partly Galactic sources and partly active galactic nuclei.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A122
- Title:
- CIELO-RGS, soft X-ray ionized emission lines catalog
- Short Name:
- J/A+A/625/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution X-ray spectroscopy has advanced our understanding of the hot Universe by revealing physical properties like kinematics, temperature, and abundances of the astrophysical plasmas. Despite technical and scientific achievements, the lack of scientific products at a level higher than count spectra is hampering complete scientific exploitation of high-quality data. This paper introduces the Catalog of Ionized Emission Lines Observed by the Reflection Grating Spectrometer (CIELO-RGS) onboard the XMM-Newton space observatory. The CIELO-RGS catalog aims to facilitate the exploitation of emission features in the public RGS spectra archive. In particular, we aim to analyze the relationship between X-ray spectral diagnostics parameters and measurements at other wavelengths. This paper focuses on the methodology of catalog generation, describing the automated line-detection algorithm. A moderate sample (~2400 observations) of high-quality RGS spectra available at XMM-Newton Science Archive is used as our starting point. A list of potential emission lines is selected based on a multi-scale peak-detection algorithm in a uniform and automated way without prior assumption on the underlying astrophysical model. The candidate line list is validated via spectral fitting with simple continuum and line profile models. We also compare the catalog content with published literature results on a small number of exemplary sources. We generate a catalog of emission lines (1.2x10^4^) detected in ~1600 observations toward stars, X-ray binaries, supernovae remnants, active galactic nuclei, and groups and clusters of galaxies. For each line, we report the observed wavelength, broadening, energy and photon flux, equivalent width, and so on.
- ID:
- ivo://CDS.VizieR/J/ApJ/702/767
- Title:
- CIV and FeK{alpha} Baldwin effects in AGNs
- Short Name:
- J/ApJ/702/767
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use UV/optical and X-ray observations of 272 radio-quiet Type 1 active galactic nuclei and quasars to investigate the CIV Baldwin Effect (BEff). The UV/optical spectra are drawn from the Hubble Space Telescope, International Ultraviolet Explorer and Sloan Digital Sky Survey archives. The X-ray spectra are from the Chandra and XMM-Newton archives. We apply correlation and partial-correlation analyses to the equivalent widths (EWs), continuum monochromatic luminosities, and {alpha}_ox_, which characterizes the relative X-ray to UV brightness. The EW of the CIV{lambda}1549 emission line is correlated with both {alpha}_ox_ and luminosity. In our sample, narrow Fe K{alpha} 6.4keV emission lines are detected in 50 objects.
- ID:
- ivo://CDS.VizieR/J/ApJS/194/4
- Title:
- Classification of CCCP X-ray sources
- Short Name:
- J/ApJS/194/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Chandra Carina Complex Project (CCCP) provides a sensitive X-ray survey of a nearby starburst region over >1deg^2^ in extent. Thousands of faint X-ray sources are found, many concentrated into rich young stellar clusters. However, significant contamination from unrelated Galactic and extragalactic sources is present in the X-ray catalog. We describe the use of a Naive Bayes classifier to assign membership probabilities to individual sources, based on source location, X-ray properties, and visual/infrared properties. For the particular membership decision rule adopted, 75% of CCCP sources are classified as members, 11% are classified as contaminants, and 14% remain unclassified. The resulting sample of stars likely to be Carina members is used in several other studies, which appear in this special issue devoted to the CCCP.
