{"corpus_id":49211658,"paper_sha":"bfb8ba4c744b7d63464a0623359d12dbdac52bb1","doi":"10.1051/0004-6361/201833051","arxiv_id":"1804.09365","pmid":null,"pmcid":null,"mag_id":2951500999,"dblp_id":null,"acl_id":null,"title":"Gaia Data Release 2. Summary of the contents and survey properties","year":2018,"publication_date":"2018-04-25","venue":"","journal":{"name":"arXiv: Astrophysics of Galaxies","pages":null,"volume":""},"journal_issn":null,"journal_title":null,"publication_types":["Review"],"pubmed_pub_types":null,"s2_fields_of_study":["Physics"],"reference_count":49,"citation_count":5422,"influential_citation_count":155,"is_open_access":true,"arxiv_categories":["astro-ph.GA","astro-ph.IM"],"arxiv_license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","arxiv_journal_ref":null,"mesh_headings":null,"chemicals":null,"comments_corrections":null,"source_flags":1,"s2_open_access_pdf_url":"https://www.aanda.org/articles/aa/pdf/2018/08/aa33051-18.pdf","s2_open_access_landing_url":"https://www.semanticscholar.org/paper/bfb8ba4c744b7d63464a0623359d12dbdac52bb1","s2_open_access_license":null,"s2_open_access_status":"BRONZE","pmc_open_access_pdf_url":null,"pmc_open_access_landing_url":null,"pmc_open_access_license":null,"pmc_open_access_status":null,"unpaywall_open_access_pdf_url":null,"unpaywall_open_access_landing_url":null,"unpaywall_open_access_license":null,"unpaywall_open_access_status":null,"abstract":"We present the second Gaia data release, Gaia DR2, consisting of astrometry, photometry, radial velocities, and information on astrophysical parameters and variability, for sources brighter than magnitude 21. In addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system. \nA summary of the contents of Gaia DR2 is presented, accompanied by a discussion on the differences with respect to Gaia DR1 and an overview of the main limitations which are still present in the survey. Recommendations are made on the responsible use of Gaia DR2 results. \nGaia DR2 contains celestial positions and the apparent brightness in G for approximately 1.7 billion sources. For 1.3 billion of those sources, parallaxes and proper motions are in addition available. The sample of sources for which variability information is provided is expanded to 0.5 million stars. This data release contains four new elements: broad-band colour information in the form of the apparent brightness in the $G_\\mathrm{BP}$ (330--680 nm) and $G_\\mathrm{RP}$ (630--1050 nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14000 minor planets in the solar system epoch astrometry and photometry are presented. Finally, Gaia DR2 also represents a new materialisation of the celestial reference frame in the optical, the Gaia-CRF2, which is the first optical reference frame based solely on extragalactic sources. There are notable changes in the photometric system and the catalogue source list with respect to Gaia DR1, and we stress the need to consider the two data releases as independent.","claims":[{"public_id":"cl_ecb36f7d71228ed2039d890c761c5bb0","status":"active","text":"Gaia DR2 contains celestial positions and G-band apparent brightness for approximately 1.7 billion sources, with parallaxes and proper motions available for 1.3 billion of those sources.","confidence":0.99,"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/claims/cl_ecb36f7d71228ed2039d890c761c5bb0"},{"public_id":"cl_e2eb12bad7d6c2dd358e127a0873ddbd","status":"active","text":"Gaia DR2 expands variability information to 0.5 million stars and adds broad-band colour information for 1.4 billion sources.","confidence":0.98,"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/claims/cl_e2eb12bad7d6c2dd358e127a0873ddbd"},{"public_id":"cl_f5425a99670d1214863066c785d6cda7","status":"active","text":"Gaia DR2 includes median radial velocities for about 7 million sources and stellar effective temperature, extinction, reddening, radius, and luminosity estimates for between 77 and 161 million sources.","confidence":0.98,"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/claims/cl_f5425a99670d1214863066c785d6cda7"},{"public_id":"cl_4fdfa5fa1ea38616b24c0447d377b2d9","status":"active","text":"Gaia DR2 provides astrometry, photometry, radial velocities, astrophysical parameters, variability information, and minor-planet epoch data for sources brighter than magnitude 21.","confidence":0.97,"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/claims/cl_4fdfa5fa1ea38616b24c0447d377b2d9"},{"public_id":"cl_35434e11d6665e7f2212570886464562","status":"active","text":"Gaia-CRF2 is a new optical celestial reference frame based solely on extragalactic sources.","confidence":0.96,"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/claims/cl_35434e11d6665e7f2212570886464562"}],"concepts":[{"public_id":"co_0b2bb3d1e17efc75b6cc70a11fb43a24","status":"active","name":"Gaia-CRF2","description":"The Gaia DR2 optical materialisation of the celestial reference frame.","types":["reference frame"],"aliases":[],"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/concepts/co_0b2bb3d1e17efc75b6cc70a11fb43a24"},{"public_id":"co_14173a2750e280c6d2eb6909c1b673c9","status":"active","name":"astrometry","description":"Measurements of source positions and motions included in the Gaia DR2 catalogue.","types":["measurement type"],"aliases":[],"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/concepts/co_14173a2750e280c6d2eb6909c1b673c9"},{"public_id":"co_19ee54f5c4a6b617557e997284a5770f","status":"active","name":"G-band apparent brightness","description":"The apparent brightness in the Gaia G band reported for Gaia DR2 sources.","types":["photometric measurement"],"aliases":["apparent brightness in G"],"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/concepts/co_19ee54f5c4a6b617557e997284a5770f"},{"public_id":"co_36ae1928ad40535b7d941f7088afb993","status":"active","name":"variability information","description":"Data identifying and characterizing brightness variability for stars in Gaia DR2.","types":["data product"],"aliases":[],"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/concepts/co_36ae1928ad40535b7d941f7088afb993"},{"public_id":"co_3b3e530480203463efc50c78b9a7e06b","status":"active","name":"broad-band colour information","description":"Photometric colour data in Gaia DR2 based on apparent brightness in the G_BP and G_RP bands.","types":["photometric data product"],"aliases":[],"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/concepts/co_3b3e530480203463efc50c78b9a7e06b"},{"public_id":"co_3bbabf55fc8ed6479310f2b3622a65c7","status":"active","name":"photometry","description":"Measurements of apparent brightness included for Gaia DR2 sources and minor planets.","types":["measurement type"],"aliases":[],"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/concepts/co_3bbabf55fc8ed6479310f2b3622a65c7"},{"public_id":"co_43f0c776b10e089957dce4aac192c59f","status":"active","name":"celestial reference frame","description":"An astronomical coordinate reference system represented in Gaia DR2 through Gaia-CRF2.","types":["astronomical standard"],"aliases":[],"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/concepts/co_43f0c776b10e089957dce4aac192c59f"},{"public_id":"co_4acd12423ab729a4a13746147c7da6c4","status":"active","name":"parallaxes and proper motions","description":"Astrometric quantities in Gaia DR2 used to characterize source distances and motions across the sky.","types":["astrometric measurement"],"aliases":[],"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/concepts/co_4acd12423ab729a4a13746147c7da6c4"},{"public_id":"co_5195cba624637c9f527f9ba5f8b615ed","status":"active","name":"astrophysical parameters","description":"Estimated stellar quantities in Gaia DR2 including effective temperature, extinction, reddening, radius, and luminosity.","types":["stellar parameter set"],"aliases":[],"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/concepts/co_5195cba624637c9f527f9ba5f8b615ed"},{"public_id":"co_60faa20fc610d57e1b027d1cb1223bf0","status":"active","name":"Gaia DR2","description":"The second Gaia data release described as a catalogue of astrometric, photometric, radial-velocity, astrophysical, and variability data.","types":["dataset"],"aliases":["Gaia Data Release 2"],"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/concepts/co_60faa20fc610d57e1b027d1cb1223bf0"},{"public_id":"co_a6230442d0958f8e895778222fe55bb0","status":"active","name":"extragalactic sources","description":"Objects outside the Galaxy used as the basis for the Gaia-CRF2 optical reference frame.","types":["astronomical source class"],"aliases":[],"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/concepts/co_a6230442d0958f8e895778222fe55bb0"},{"public_id":"co_cdc4fc4a45901e1e48a5ffb91e0b2734","status":"active","name":"median radial velocities","description":"Line-of-sight velocity measurements reported as median values for a subset of Gaia DR2 sources.","types":["kinematic measurement"],"aliases":[],"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/concepts/co_cdc4fc4a45901e1e48a5ffb91e0b2734"},{"public_id":"co_f3e15dbce97f754468ab7b85e653c33b","status":"active","name":"celestial positions","description":"Sky-position measurements reported for approximately 1.7 billion Gaia DR2 sources.","types":["astronomical measurement"],"aliases":[],"contributors":[{"id":136,"public_id":"3c2apqe3ut","public_label":"Anonymous (3c2apqe3ut)","roles":["extraction"],"url":"https://sah.borca.ai/u/3c2apqe3ut"},{"id":17,"public_id":"322360f1c1","public_label":"Killer Whale (322360f1c1)","roles":["review"],"url":"https://sah.borca.ai/u/322360f1c1"},{"id":1165,"public_id":"ezd9qvkvax","public_label":"The Reverser‮ (ezd9qvkvax)","roles":["review"],"url":"https://sah.borca.ai/u/ezd9qvkvax"}],"url":"https://sah.borca.ai/concepts/co_f3e15dbce97f754468ab7b85e653c33b"}],"external_ids":{"DOI":"10.1051/0004-6361/201833051","ArXiv":"1804.09365","PubMed":null,"PubMedCentral":null,"MAG":2951500999,"DBLP":null,"ACL":null},"open_access":{"is_open_access":true,"pdf_url":"https://www.aanda.org/articles/aa/pdf/2018/08/aa33051-18.pdf","landing_url":"https://www.semanticscholar.org/paper/bfb8ba4c744b7d63464a0623359d12dbdac52bb1","source":"semantic_scholar","pdf_url_source":"semantic_scholar_open_access_pdf","license":null,"status":"BRONZE","reason":null},"reference_availability":{"status":"available","references_indexed":true,"full_text_available":true,"full_text_source":"arxiv","count_basis":"semantic_scholar_metadata","extraction_status":"not_applicable","reason":null},"source":{"provider":"episteme2","base_corpus":"semantic_scholar_dump","freshness_mode":"unknown","basis":["semantic_scholar_metadata","postgres_metadata"],"limits":["paper metadata is based on indexed upstream scholarly datasets","claims and concepts are available only for extracted papers","absence of claims or concepts means no extracted graph data is available in this response"],"status":"available","degraded":false,"degraded_reasons":[],"diagnostics":{"status":"available","degraded":false,"degraded_reasons":[],"metadata_status":"available","graph_status":"available","abstract_status":"available"},"source_flags":1},"paper_id":630976,"paper_uid":"3fc8ba53-3044-436c-af9b-9f7bed006f00","canonical_identity":{"paper_id":630976,"paper_uid":"3fc8ba53-3044-436c-af9b-9f7bed006f00","identity_status":"available","lookup_basis":"semantic_scholar_external_id","compatibility_path":"corpus_id"},"url":"https://sah.borca.ai/papers/49211658"}