{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,13]],"date-time":"2026-02-13T20:42:04Z","timestamp":1771015324126,"version":"3.50.1"},"reference-count":57,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2019,11,27]],"date-time":"2019-11-27T00:00:00Z","timestamp":1574812800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["PD\/BD\/114071\/2015"],"award-info":[{"award-number":["PD\/BD\/114071\/2015"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["UID\/MAT\/04106\/2019 (CIDMA)"],"award-info":[{"award-number":["UID\/MAT\/04106\/2019 (CIDMA)"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["UID\/FIS\/00099\/2013 (CENTRA)"],"award-info":[{"award-number":["UID\/FIS\/00099\/2013 (CENTRA)"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["PTDC\/FIS-OUT\/28407\/2017"],"award-info":[{"award-number":["PTDC\/FIS-OUT\/28407\/2017"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100010661","name":"Horizon 2020","doi-asserted-by":"publisher","award":["H2020-MSCA-RISE-2015 Grant No. StronGrHEP-690904"],"award-info":[{"award-number":["H2020-MSCA-RISE-2015 Grant No. StronGrHEP-690904"]}],"id":[{"id":"10.13039\/100010661","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100010661","name":"Horizon 2020","doi-asserted-by":"publisher","award":["H2020-MSCA-RISE-2017 Grant No. FunFiCO-777740"],"award-info":[{"award-number":["H2020-MSCA-RISE-2017 Grant No. FunFiCO-777740"]}],"id":[{"id":"10.13039\/100010661","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000921","name":"European Cooperation in Science and Technology","doi-asserted-by":"publisher","award":["CA16104"],"award-info":[{"award-number":["CA16104"]}],"id":[{"id":"10.13039\/501100000921","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Universe"],"abstract":"<jats:p>Hypothetical ultralight bosonic fields will spontaneously form macroscopic bosonic halos around Kerr black holes, via superradiance, transferring part of the mass and angular momentum of the black hole into the halo. Such a process, however, is only efficient if resonant\u2014when the Compton wavelength of the field approximately matches the gravitational scale of the black hole. For a complex-valued field, the process can form a stationary, bosonic field black hole equilibrium state\u2014a black hole with synchronised hair. For sufficiently massive black holes, such as the one at the centre of the M87 supergiant elliptic galaxy, the hairy black hole can be robust against its own superradiant instabilities, within a Hubble time. Studying the shadows of such scalar hairy black holes, we constrain the amount of hair which is compatible with the Event Horizon Telescope (EHT) observations of the M87 supermassive black hole, assuming the hair is a condensate of ultralight scalar particles of mass     \u03bc \u223c  10  \u2212 20       eV, as to be dynamically viable. We show the EHT observations set a weak constraint, in the sense that typical hairy black holes that could develop their hair dynamically, are compatible with the observations, when taking into account the EHT error bars and the black hole mass\/distance uncertainty.<\/jats:p>","DOI":"10.3390\/universe5120220","type":"journal-article","created":{"date-parts":[[2019,11,27]],"date-time":"2019-11-27T11:07:00Z","timestamp":1574852820000},"page":"220","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":113,"title":["EHT Constraint on the Ultralight Scalar Hair of the M87 Supermassive Black Hole"],"prefix":"10.3390","volume":"5","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8375-6943","authenticated-orcid":false,"given":"Pedro","family":"Cunha","sequence":"first","affiliation":[{"name":"Departamento de Matem\u00e1tica da, Universidade de Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal"},{"name":"Centre for Research and Development in Mathematics and Applications (CIDMA), Campus de Santiago, 3810-183 Aveiro, Portugal"},{"name":"Centro de Astrof\u00edsica e Gravita\u00e7\u00e3o\u2014CENTRA, Departamento de F\u00edsica, Instituto Superior T\u00e9cnico\u2014IST, Universidade de Lisboa\u2014UL, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9619-2013","authenticated-orcid":false,"given":"Carlos","family":"Herdeiro","sequence":"additional","affiliation":[{"name":"Departamento de Matem\u00e1tica da, Universidade de Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal"},{"name":"Centre for Research and Development in Mathematics and Applications (CIDMA), Campus de Santiago, 3810-183 Aveiro, Portugal"},{"name":"Centro de Astrof\u00edsica e Gravita\u00e7\u00e3o\u2014CENTRA, Departamento de F\u00edsica, Instituto Superior T\u00e9cnico\u2014IST, Universidade de Lisboa\u2014UL, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal"}]},{"given":"Eugen","family":"Radu","sequence":"additional","affiliation":[{"name":"Departamento de Matem\u00e1tica da, Universidade de Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal"},{"name":"Centre for Research and Development in Mathematics and Applications (CIDMA), Campus de Santiago, 3810-183 Aveiro, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2019,11,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"237","DOI":"10.1103\/PhysRevLett.11.237","article-title":"Gravitational field of a spinning mass as an example of algebraically special metrics","volume":"11","author":"Kerr","year":"1963","journal-title":"Phys. Rev. Lett."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1007\/978-3-319-02063-1_9","article-title":"A Review on the Scalar Field\/Bose-Einstein Condensate Dark Matter Model","volume":"38","author":"Robles","year":"2014","journal-title":"Astrophys. 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