J/A+A/710/L6ivo://CDS.VizieR/J/A+A/710/L6CDSKaur K.Rammala-Zitha I.Basu A.Witzel G.Wielgus M.Balakrishnan V.,Barr E.D.Brunthaler A.Buchner S.Champion D.J.Hoeft M.Khan S.,Kloeckner H.-R.Koenig C.Kramer M.Venkatraman Krishnan V.Ma Y.K.,Mao S.A.Padmanabh P.V.Ranchod S.Sridhar S.S.Wagenveld J.D.,Wharton R.S.Wucknitz O.2026-05-28T07:50:33Z2026-05-28T08:44:18ZCDS support team

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

cds-question@unistra.frblack-holesradio-sourcesinterferometryThe supermassive black hole Sagittarius A* (Sgr A*) exhibits temporal and spectral variability across the electromagnetic spectrum. However, variability at radio frequencies below ~5GHz for timescales shorter than a day remains largely unexplored. We investigate the variability of Sgr A* at 2.79GHz on short timescales (1-min), to probe an under-explored regime of its emission process. Through point-source model fitting in the uv-domain, we analyse the flux density variation of Sgr A* over an 8h observation. We detect flux variation on a few tens of minute timescale with a modulation index of 6.11%, a mean flux density of 827+/-0.1(stat)+/-33(sys)mJy, and a mean spectral slope of 0.08+/-0.03. Furthermore, we measure the slope of the structure function of the observed light curve as 0.81+/-0.05 with a characteristic timescale of about 120-min. Our study at low radio frequencies is a critical step toward constraining the physical mechanisms that drive Sgr A*'s variable emission and its spectral energy distribution. Our study suggests that variability at centimetre and millimetre wavelengths is likely more closely related than previously thought.2026A&A...710L...6Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/710/L6CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/AJ/127/3399 : Sgr A* variability at cm wavelengths (Herrnstein+, 2004)J/ApJ/793/120 : Spitzer/IRAC Sgr A* light curve data (Hora+, 2014)J/ApJ/802/69 : VLA, ALMA and SMA monitoring of Sgr A* (Bower+, 2015)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/599/A135 : NH_3_ Odin observations towards Sgr A (Sandqvist+, 2017)J/A+A/601/A80 : LABOCA 345GHz observations of Sgr A* (Subroweit+, 2017)J/ApJ/859/60 : Sgr A* 1.3mm VLBI observations with EHT in 2013 (Lu+, 2018)J/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/710/L6https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/710/L6http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/710/L6https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/710/L6https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/710/L6http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/710/L6GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapRadiodefaultJ/A+A/710/L6/sgralcFlux density and spectral index values of Sagittarius A* at 2.79GHz with MeerKATrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimestampObservational timestamp in UTC on 21 March 2024time.epochnullableFluxDensFlux density derived from point-source fitting performed in the uv-domain over a UV-range of 50000 lambda to 67403.3 lambda.Jyphot.flux;em.UVfloate_FluxDensFlux Total flux density uncertainty (1)Jystat.errorfloatSPIIn-band spectral indexspect.indexfloate_SPIIn-band spectral index uncertaintystat.errorfloat