@prefix dcat: <http://www.w3.org/ns/dcat#> .
@prefix dct: <http://purl.org/dc/terms/> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix org: <http://www.w3.org/ns/org#> .
@prefix skos: <http://www.w3.org/2004/02/skos/core#> .
@prefix vcard: <http://www.w3.org/2006/vcard/ns#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

<https://data.nasa.gov/dataset/d042b3fb-eba5-415c-93d0-90832e81c346> a dcat:Dataset ;
    dct:description "The Serendipitous Extragalactic X-ray Source Identification (SEXSI) Program is designed to expand significantly the sample of identified extragalactic hard X-ray sources at intermediate fluxes, 10&lt;sup&gt;-15&lt;/sup&gt; ergs/cm&lt;sup&gt;2&lt;/sup&gt;/s &lt; 2-10 keV Flux &lt;~ 10&lt;sup&gt;-13&lt;/sup&gt; ergs/cm&lt;sup&gt;2&lt;/sup&gt;/s. SEXSI, which includes sources derived from more than 2 square degrees of Chandra images, provides the largest hard X-ray-selected sample yet studied, offering an essential complement to the Chandra Deep Fields (total area of 0.2 square degrees). In Eckart et al. (2005, Paper II) R-band optical imaging of the SEXSI fields from the Palomar P60 and P200, the MDM 2.4m and 1.3m, and the Keck I telescopes is described. The authors have identified counterparts or derived flux limits for nearly 1000 hard X-ray sources. Using the optical images, they have derived accurate source positions. They have investigated correlations between optical and X-ray flux, and optical flux and X-ray hardness ratio. They have also studied the density of optical sources surrounding X-ray counterparts, as well as the properties of optically faint, hard X-ray sources. In Eckart et al. (2006, Paper III) optical spectra of 477 counterparts are presented. These spectra reach to R-band magnitudes of &lt;~24 and have produced identifications and redshifts for 438 hard X-ray sources. Typical completeness levels in the 27 Chandra fields studied are 40-70%. The vast majority of the 2-10 keV selected sample are AGNs with redshifts between 0.1 and 3; the highest redshift source lies at z = 4.33. This table which combines data presented in Eckart et al. (2005, 2006) has links to the list of SEXSI X-ray sources (the HEASARC Browse table CHANSEXSI: see Paper I = Harrison et al. 2003, ApJ, 596, 944). This table was originally created by the HEASARC in June 2005 based on the CDS version of Table 3 from Eckart et al. (2005: CDS table J/ApJS/156/35/table3.dat). It was updated in August 2006 to include information from Table 2 of Eckart et al. (2006: the electronic version available at the electronic ApJ web site). This is a service provided by NASA HEASARC ." ;
    dct:identifier "ivo://nasa.heasarc/chansexoid" ;
    dct:issued "2025-04-01T13:31:58.023305"^^xsd:dateTime ;
    dct:modified "2026-10-26T22:16:12+00:00"^^xsd:dateTime ;
    dct:publisher <https://data.nasa.gov/organization/dbb294e4-8597-44f5-aaf4-c0baac12cdbc> ;
    dct:title "Chandra Serendipitous Extragalactic X-Ray Source ID (SEXSI) Optical Follow-Up" ;
    dcat:contactPoint [ a vcard:Organization ;
            vcard:fn "HEASARC Help Desk" ;
            vcard:hasEmail <mailto:andrew.ptak@nasa.gov> ] ;
    dcat:distribution <https://data.nasa.gov/dataset/d042b3fb-eba5-415c-93d0-90832e81c346/resource/1e7df5ac-21a4-4f59-9c2a-3954363f586e>,
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    dcat:keyword "__" ;
    dcat:theme <%7BAstrophysics%7D> .

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    dct:format "HTML" ;
    dct:identifier "1e7df5ac-21a4-4f59-9c2a-3954363f586e" ;
    dct:issued "2025-08-21T15:34:51.763012"^^xsd:dateTime ;
    dct:modified "2026-03-09T19:48:20.024864"^^xsd:dateTime ;
    dcat:accessURL <https://heasarc.gsfc.nasa.gov/W3Browse/all/chansexoid.html> ;
    dcat:mediaType "text/html" .

<https://data.nasa.gov/dataset/d042b3fb-eba5-415c-93d0-90832e81c346/resource/96880550-483a-4805-addc-faf0bd506895> a dcat:Distribution ;
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    dct:identifier "96880550-483a-4805-addc-faf0bd506895" ;
    dct:issued "2025-08-21T15:34:51.763018"^^xsd:dateTime ;
    dct:modified "2026-03-09T19:48:20.024967"^^xsd:dateTime ;
    dcat:accessURL <https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=chansexoid&> ;
    dcat:mediaType "application/octet-stream" .

<https://data.nasa.gov/organization/dbb294e4-8597-44f5-aaf4-c0baac12cdbc> a org:Organization ;
    skos:prefLabel "NASA" ;
    foaf:name "NASA" .