- ID:
- ivo://CDS.VizieR/IX/45
- Title:
- The Chandra Source Catalog, Release 1.1
- Short Name:
- IX/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Chandra Source Catalog (CSC) is a general purpose virtual X-ray astrophysics facility that provides access to a carefully selected set of generally useful quantities for individual X-ray sources, and is designed to satisfy the needs of a broad-based group of scientists, including those who may be less familiar with astronomical data analysis in the X-ray regime. The first release of the CSC includes information about 94,676 distinct X-ray sources detected in a subset of public Advanced CCD Imaging Spectrometer imaging observations from roughly the first eight years of the Chandra mission. This release of the catalog includes point and compact sources with observed spatial extents <~30''. The catalog (1) provides access to the best estimates of the X-ray source properties for detected sources, with good scientific fidelity, and directly supports scientific analysis using the individual source data; (2) facilitates analysis of a wide range of statistical properties for classes of X-ray sources; and (3) provides efficient access to calibrated observational data and ancillary data products for individual X-ray sources, so that users can perform detailed further analysis using existing tools. The catalog includes real X-ray sources detected with flux estimates that are at least 3 times their estimated 1-{sigma} uncertainties in at least one energy band, while maintaining the number of spurious sources at a level of <~1 false source per field for a 100ks observation. For each detected source, the CSC provides commonly tabulated quantities, including source position, extent, multi-band fluxes, hardness ratios, and variability statistics, derived from the observations in which the source is detected. In addition to these traditional catalog elements, for each X-ray source the CSC includes an extensive set of file-based data products that can be manipulated interactively, including source images, event lists, light curves, and spectra from each observation in which a source is detected.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/697/1695
- Title:
- The Chandra survey of the SMC "Bar". II.
- Short Name:
- J/ApJ/697/1695
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the most likely optical counterparts of 113 X-ray sources detected in our Chandra survey of the central region of the Small Magellanic Cloud (SMC) based on the OGLE-II and Magellanic Clouds Photometric Survey catalogs. We estimate that the foreground contamination and chance coincidence probability are minimal for the bright optical counterparts (corresponding to OB type stars; 35 in total). We propose here for the first time 13 high-mass X-ray binaries, of which four are Be/X-ray binaries (Be-XRBs), and we confirm the previous classification of 18 Be-XRBs. We estimate that the new candidate Be-XRBs have an age of ~15-85Myr, consistent with the age of Be stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/236/48
- Title:
- The Chandra UDS survey (X-UDS)
- Short Name:
- J/ApJS/236/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the X-UDS survey, a set of wide and deep Chandra observations of the Subaru-XMM Deep/UKIDSS Ultra Deep Survey (SXDS/UDS) field. The survey consists of 25 observations that cover a total area of 0.33deg^2^. The observations are combined to provide a nominal depth of ~600ks in the central 100arcmin^2^ region of the field that has been imaged with Hubble/WFC3 by the CANDELS survey and ~200ks in the remainder of the field. In this paper, we outline the survey's scientific goals, describe our observing strategy, and detail our data reduction and point source detection algorithms. Our analysis has resulted in a total of 868 band-merged point sources detected with a false-positive Poisson probability of <1x10^-4^. In addition, we present the results of an X-ray spectral analysis and provide best-fitting neutral hydrogen column densities, N_H_, as well as a sample of 51 Compton-thick active galactic nucleus candidates. Using this sample, we find the intrinsic Compton-thick fraction to be 30%-35% over a wide range in redshift (z=0.1-3), suggesting the obscured fraction does not evolve very strongly with epoch. However, if we assume that the Compton-thick fraction is dependent on luminosity, as is seen for Compton-thin sources, then our results are consistent with a rise in the obscured fraction out to z~3. Finally, an examination of the host morphologies of our Compton-thick candidates shows a high fraction of morphological disturbances, in agreement with our previous results.
- ID:
- ivo://CDS.VizieR/J/A+A/561/A63
- Title:
- The chemically peculiar binary HD 161701
- Short Name:
- J/A+A/561/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform a complete study of the HgMn binary HD 161701, including the determination of physical parameters and photospheric chemical abundances. We analyzed time series of high-resolution FEROS and HARPS spectroscopic observations in addition to a near-IR spectrum obtained with CRIRES. Radial velocity curves were combined with additional spectroscopic information to estimate absolute stellar parameters. A spectral separation technique was applied, which enabled us to conduct a detailed spectral analysis of both components. The primary is a HgMn star with overabundances of P, Mn, Ga, Y, Xe, and Hg. The secondary is an Ap star showing strong (2-5dex) overabundances of Sr, Y, and rare-earth elements. We detected line profile variations in both stellar companions, indicating a non uniform surface distribution of chemical composition. The secondary presents a remarkable chemical pattern with Ti and rare-earths pemanently facing the binary companion, and Fe concentrated on the far side. The primary star shows weak profile variations in Mn and Cr spectral lines. The coincidence of chemical spots with the position of the binary companion suggests a possible connection between the presence of the companion and the origin of chemical anomalies.
- ID:
- ivo://cvo.naoc/cvo
- Title:
- The China Virtual Observatory
- Short Name:
- China-VO
- Date:
- 27 Apr 2007 03:56:24
- Publisher:
- Chenzhou CUI
- Description:
- Virtual Observatory of China (China-VO) is a consortium initiated by National Astronomical Observatory of China (NAOC) and Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) project.
- ID:
- ivo://cvo.naoc
- Title:
- The China Virtual Observatory Naming Authority
- Short Name:
- China-VO
- Date:
- 17 Sep 2007 11:47:00
- Publisher:
- The China Virtual Observatory
- Description:
- Virtual Observatory of China (China-VO) is a consortium initiated by National Astronomical Observatory of China (NAOC) and Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) project.
- ID:
- ivo://CDS.VizieR/J/AJ/157/85
- Title:
- The CIDA Variability Survey of Orion OB1. II.
- Short Name:
- J/AJ/157/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of our large-scale, optical, multi-epoch photometric survey across ~180 square degrees in the Orion OB1 association, complemented with extensive follow-up spectroscopy. Our focus is mapping and characterizing the off-cloud, low-mass, pre-main-sequence (PMS) populations. We report 2062 K- and M-type confirmed T Tauri members; 59% are located in the OB1a subassociation, 27% in the OB1b subassociation, and the remaining 14% in the A and B molecular clouds. We characterize two new clusterings of T Tauri stars, the HD 35762 and HR 1833 groups, both located in OB1a not far from the 25 Ori cluster. We also identify two stellar overdensities in OB1b, containing 231 PMS stars, and find that the OB1b region is composed of two populations at different distances, possibly due to the OB1a subassociation overlapping with the front of OB1b. A ~2 deg wide halo of young stars surrounds the Orion Nebula Cluster, corresponding in part to the low-mass populations of NGC 1977 and NGC 1980. We use the strength of H{alpha} in emission, combined with the IR excess and optical variability, to define a new type of T Tauri star, the C/W class, stars we propose may be nearing the end of their accretion phase, in an evolutionary state between classical and weak-lined T Tauri stars. The evolution of the ensemble-wide equivalent width of Li I{lambda}6707 indicates a Li depletion timescale of ~8.5 Myr. Disk accretion declines with an e-folding timescale of ~2 Myr, consistent with previous studies.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A127
- Title:
- The C^+^ ion photofragment spectra
- Short Name:
- J/A+A/647/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon monoxide (CO) is one of the most abundant molecular species in comets. Its photodissociation by the solar radiation in the vacuum ultraviolet (VUV) region produces excited atomic fragments C(^1^D), C(^1^S), and O(^1^D), which radiate at characteristic wavelengths when they decay to lower states. The fractional rate constants for generating these fragments from CO photodissociation under the entire range of the solar radiation field are key input values in modelling the observed atomic emission intensities from comets. In this study, the branching ratios of the four lowest dissociation channels C(^3^P)+O(^3^P), C(^1^D)+O(^3^P), C(^3^P)+O(^1^D), and C(^1^S)+O(^3^P) of the ^12^C^16^O photodissociation are measured in the VUV energy range between the threshold of producing the C(^1^S)+O(^3^P) channel (~110500cm^-1^) and the ionisation energy (IE) of ^12^C^16^O (~113045cm^-1^). We measured these ratios using the VUV time-slice velocity-map ion imaging apparatus. We observe a number of high Rydberg states in the aforementioned energy range, with most of them mainly producing ground C(^3^P) and O(^3^P) atomic fragments, and only a few of them producing a significant amount of excited C(^1^D) or O(^1^D) fragments. We also observe the excited C(^1^S) fragment from CO photodissociation and measured its branching ratio for the first time. Based on the photodissociation branching ratios measured in the current and previous studies, we are able to estimate the relative percentages of the excited atomic fragments C(^1^D), C(^1^S), and O(^1^D) from the solar photolysis of ^12^C^16^O below its IE. We discuss the implications for the photochemical modelling of the CO-dominated comet C/2016 R2 (Pan-STARRS).
21589. The CLASS blazar survey. I.
- ID:
- ivo://CDS.VizieR/J/MNRAS/326/1455
- Title:
- The CLASS blazar survey. I.
- Short Name:
- J/MNRAS/326/1455
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents a new complete and well-defined sample of flat-spectrum radio sources (FSRS) selected from the Cosmic Lens All-Sky Survey (CLASS), with the further constraint of a bright (mag<=17.5) optical counterpart. The sample has been designed to produce a large number of low-luminosity blazars in order to test the current unifying models in the low-luminosity regime. In this first paper the new sample is presented and the radio properties of the 325 sources contained therein are discussed.
21590. The CLASS blazar survey. II.
- ID:
- ivo://CDS.VizieR/J/MNRAS/329/877
- Title:
- The CLASS blazar survey. II.
- Short Name:
- J/MNRAS/329/877
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the optical properties of the objects selected in the CLASS blazar survey. Because an optical spectrum is now available for 70 per cent of the 325 sources present in the sample, a spectral classification, based on the appearance of the emission/absorption lines, is possible. A wide variety of optical spectral types is found. Besides `classical' BL Lacs (42), BL Lac candidates (5) and high-power (P_5GHz_>10^26^W/Hz) flat spectrum radio quasars (67), a significant number of `passive' elliptical galaxies (41) is also found. Moreover, 33 broad emission line objects with a low radio power (P(5GHz)>10^26^W/Hz) are discovered, suggesting that at least a fraction (~24-30 per cent) of low-power blazars have a broad line region. Finally, 34 objects showing only narrow emission lines, either as a result of some starburst activity in the host galaxy or as a result of the presence of an active galactic nucleus, appear in the sample.
