{"id":79,"date":"2019-07-16T10:19:40","date_gmt":"2019-07-16T10:19:40","guid":{"rendered":"http:\/\/www.issibern.ch\/teams\/studyultraviovar\/?page_id=2"},"modified":"2019-07-16T10:19:40","modified_gmt":"2019-07-16T10:19:40","slug":"sample-page","status":"publish","type":"page","link":"https:\/\/www.issibern.ch\/teams\/studyultraviovar\/","title":{"rendered":"Abstract"},"content":{"rendered":"\n<p>Much progress has been made in our understanding of active galactic \nnuclei (AGN) in the 85 years, since Karl Seyfert noted their distinctive\n broad emission lines. Mass accretion via a hot rotating disc onto a \nsuper-massive black hole, is now the well accepted picture. However, all\n is not well with important aspects of our understanding. This has been \nhighlighted by the increasing use of the time domain as a new tool to \ninvestigate the inner regions of AGN that we cannot spatially resolve. \nThis proposal will focus on a particular aspect of time domain \nastrophysics, namely the ultra-violet (henceforth, UV). &nbsp;This wavelength\n region is not accessible from the ground (except for bluest u-band, \nwhich we will make use of) due to atmospheric absorption. For low \nredshift AGN which often have the best quality data, this is the \nwavelength region dominated by the accretion disc, a key component in \nour understanding of the physics of AGN.&nbsp; The timescales of AGN UV \nvariability are inconsistent with basic ideas of the source of the \nobserved variations. &nbsp;In particular viscosity changes within the disc \noccur far too slowly compared with observations. &nbsp;This problem has been \ncalled \u201cThe Quasar Viscosity Crisis\u201d (Lawrence, 2018). Our project will \naim to address the UV variability as a symptom of this crisis, and to \npropose explanations based on a large body of unexplored observational \ndata, and modelling. &nbsp; Our proposed project will quantify the UV \nvariability on timescales from weeks to decades, for a very large sample\n of AGN. It will be the first such study to exploit the huge UV \ndata-bases that exists for observations from the <strong>ESA cornerstone mission XMM-Newton<\/strong> and the <strong>Neils Gehrels Swift Observatory<\/strong>&nbsp;\n (with Italian and UK involvement). This project will be very timely \ngiven the growing importance of Time Domain Astrophysics, and, as an \naside the 20<sup>th<\/sup> anniversary of the launch of XMM-Newton this \ncoming December! &nbsp;The results will be both statistically significant, as\n we will set the UV variability in the context of other basic properties\n of the AGN, and also we will be certain to discover some extreme cases \nof variability ie. example of a &nbsp;recently identified group of \u201cChanging \nLook\u201d AGN.  <\/p>\n","protected":false},"excerpt":{"rendered":"<p>Much progress has been made in our understanding of active galactic nuclei (AGN) in the 85 years, since Karl Seyfert noted their distinctive broad emission lines. Mass accretion via a hot rotating disc onto a super-massive black hole, is now &hellip; <a href=\"https:\/\/www.issibern.ch\/teams\/studyultraviovar\/\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"open","template":"","meta":{"footnotes":""},"class_list":["post-79","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.issibern.ch\/teams\/studyultraviovar\/wp-json\/wp\/v2\/pages\/79","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.issibern.ch\/teams\/studyultraviovar\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.issibern.ch\/teams\/studyultraviovar\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.issibern.ch\/teams\/studyultraviovar\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.issibern.ch\/teams\/studyultraviovar\/wp-json\/wp\/v2\/comments?post=79"}],"version-history":[{"count":0,"href":"https:\/\/www.issibern.ch\/teams\/studyultraviovar\/wp-json\/wp\/v2\/pages\/79\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.issibern.ch\/teams\/studyultraviovar\/wp-json\/wp\/v2\/media?parent=79"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}