J/A+A/682/A97ivo://CDS.VizieR/J/A+A/682/A97doi:10.26093/cds/vizier.36820097CDSWielgus M.Issaoun S.Marti-Vidal I.Emami R.Moscibrodzka M.,Brinkerink Ch.D.Goddi C.Fomalont E.2024-11-29T20:00:57Z2024-02-09T09:00:07ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frgalactic-centerblack-holesmillimeter-astronomysubmillimeter-astronomypolarimetryWe report on 85-101 GHz light curves of the Galactic Center supermassive black hole, Sagittarius A* (Sgr A*), observed in April 2017 with the Atacama Large Millimeter/submillimeter Array (ALMA). This study of high-cadence full-Stokes data provides new measurements of the fractional linear polarization at a 1-2% level resolved in 4 s time segments, and stringent upper limits on the fractional circular polarization at 0.3%. We compare these findings to ALMA light curves of Sgr A* at 212-230GHz observed three days later, characterizing a steep depolarization of the source at frequencies below about 150GHz. We obtain time-dependent rotation measure (RM) values, with the mean RM at 85-101GHz being a factor of two lower than that at 212-230GHz. Together with the rapid temporal variability of the RM and its different statistical characteristics in both frequency bands, these results indicate that the Faraday screen in Sgr A* is largely internal, with about half of the Faraday rotation taking place inside the inner 10 gravitational radii, contrary to the common external Faraday screen assumption. We then demonstrate how this observation can be reconciled with theoretical models of radiatively inefficient accretion flows for a reasonable set of physical parameters. Comparisons with numerical general relativistic magnetohydrodynamic simulations suggest that the innermost part of the accretion flow in Sgr A* is much less variable than these models predict; in particular, the observed magnetic field structure appears to be coherent and persistent.2024A&A...682A..97Whttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/682/A97CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/549/A57 : Young, massive star candidates in Sgr A* (Nishiyama+, 2013)J/ApJ/793/120 : Spitzer/IRAC Sgr A* light curve data (Hora+, 2014)J/MNRAS/454/1525 : XMM-Newton and Chandra monitoring of Sgr A* (Ponti+, 2015)J/A+A/589/A116 : Multiwavelength study of Sgr A* (Mossoux+, 2016)J/A+A/601/A80 : LABOCA 345GHz observations of Sgr A* (Subroweit+, 2017)J/A+A/603/A68 : Images of molecular and ionized gas around Sgr A*J/ApJ/859/60 : Sgr A* 1.3mm VLBI observations with the EHT in 2013J/ApJ/931/7 : Variability of Sgr A* in 2019 July (Boyce+, 2022)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/682/A97https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/682/A97http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/682/A97https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/682/A97https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/682/A97http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/682/A97GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapMillimeterdefaultJ/A+A/682/A97/tableb0Light curve observed at 86.3GHzrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeUTC time on 2017 April 3 in hourshtime.epochfloatIStokes I flux density in the 86.3GHz bandJyphot.flux.density;em.mm.50-100GHzfloatQStokes Q flux density in the 86.3GHz bandJyphot.flux.density;em.mm.50-100GHzfloatUStokes U flux density in the 86.3GHz bandJyphot.flux.density;em.mm.50-100GHzfloatVStokes V flux density in the 86.3GHz bandJyphot.flux.density;em.mm.50-100GHzfloatJ/A+A/682/A97/tableb1Light curve observed at 88.3GHzrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeUTC time on 2017 April 3 in hourshtime.epochfloatIStokes I flux density in the 88.3GHz bandJyphot.flux.density;em.mm.50-100GHzfloatQStokes Q flux density in the 88.3GHz bandJyphot.flux.density;em.mm.50-100GHzfloatUStokes U flux density in the 88.3GHz bandJyphot.flux.density;em.mm.50-100GHzfloatVStokes V flux density in the 88.3GHz bandJyphot.flux.density;em.mm.50-100GHzfloatJ/A+A/682/A97/tableb2Light curve observed at 98.3GHzrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeUTC time on 2017 April 3 in hourshtime.epochfloatIStokes I flux density in the 98.3GHz bandJyphot.flux.density;em.mm.50-100GHzfloatQStokes Q flux density in the 98.3GHz bandJyphot.flux.density;em.mm.50-100GHzfloatUStokes U flux density in the 98.3GHz bandJyphot.flux.density;em.mm.50-100GHzfloatVStokes V flux density in the 98.3GHz bandJyphot.flux.density;em.mm.50-100GHzfloatJ/A+A/682/A97/tableb3Light curve observed at 100.3GHzrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeUTC time on 2017 April 3 in hourshtime.epochfloatIStokes I flux density in the 100.3GHz bandJyphot.flux.density;em.mm.100-200GHzfloatQStokes Q flux density in the 100.3GHz bandJyphot.flux.density;em.mm.100-200GHzfloatUStokes U flux density in the 100.3GHz bandJyphot.flux.density;em.mm.100-200GHzfloatVStokes V flux density in the 100.3GHz bandJyphot.flux.density;em.mm.100-200GHzfloat