J/ApJ/863/15ivo://CDS.VizieR/J/ApJ/863/15doi:10.26093/cds/vizier.18630015CDSWitzel G.Martinez G.Hora J.Willner S.P.Morris M.R.Gammie C.,Becklin E.E.Ashby M.L.N.Baganoff F.Carey S.Do T.Fazio G.G.,Ghez A.Glaccum W.J.Haggard D.Herrero-Illana R.Ingalls J.,Narayan R.Smith H.A.2019-09-02T11:52:23Z2019-08-29T14:58:31ZCDS support team

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

cds-question@unistra.frgalactic-centerinfrared-photometrySagittarius A* (Sgr A*) is the variable radio, near-infrared (NIR), and X-ray source associated with accretion onto the Galactic center black hole. We present an analysis of the most comprehensive NIR variability data set of Sgr A* to date: eight 24 hr epochs of continuous monitoring of Sgr A* at 4.5{mu}m with the IRAC instrument on the Spitzer Space Telescope, 93 epochs of 2.18{mu}m data from Naos Conica at the Very Large Telescope, and 30 epochs of 2.12{mu}m data from the NIRC2 camera at the Keck Observatory, in total 94929 measurements. A new approximate Bayesian computation method for fitting the first-order structure function extracts information beyond current fast Fourier transformation (FFT) methods of power spectral density (PSD) estimation. With a combined fit of the data of all three observatories, the characteristic coherence timescale of Sgr A* is {tau}_b_=243_-57_^+82^min (90% credible interval). The PSD has no detectable features on timescales down to 8.5min (95% credible level), which is the ISCO orbital frequency for a dimensionless spin parameter a=0.92. One light curve measured simultaneously at 2.12 and 4.5{mu}m during a low flux-density phase gave a spectral index {alpha}_s_=1.6+/-0.1 (F_{nu}_{propto}{nu}^-{alpha}_s_^). This value implies that the Sgr A* NIR color becomes bluer during higher flux-density phases. The probability densities of flux densities of the combined data sets are best fit by log-normal distributions. Based on these distributions, the Sgr A* spectral energy distribution is consistent with synchrotron radiation from a non-thermal electron population from below 20GHz through the NIR.2018ApJ...863...15Whttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/863/15CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/AJ/127/3399 : Sgr A* variability at cm wavelengths (Herrnstein+, 2004)J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)J/A+A/511/A18 : NIR observations of stars near SgrA* (Schoedel+, 2010)J/ApJ/725/331 : Astrometry in the Galactic Center (Yelda+, 2010)J/A+A/534/A117 : NIR polarimetry of sources near SgrA* (Buchholz+, 2011)J/ApJ/727/L36 : 1.3mm VLBI observations of Sagittarius A* (Fish+, 2011)J/ApJ/764/154 : Stellar populations in the central 0.5pc. I. (Do+, 2013)J/MNRAS/428/2731 : SgrA* emission at 7mm (Beaklini+, 2013)J/A+A/557/A82 : NIR polarimetry of Galactic center sources (Buchholz+, 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/ApJ/802/69 : VLA, ALMA and SMA monitoring of Sgr A* (Bower+, 2015)J/ApJ/820/90 : 4yr 1.3mm VLBI observations of SgrA* with EHT (Fish+, 2016)J/ApJ/830/17 : Gal. Center secondary IR astrometric standards (Boehle+, 2016)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/ApJ/859/60 : Sgr A* 1.3mm VLBI obs. with the EHT in 2013 (Lu+, 2018)J/A+A/618/A35 : ALMA images of the CND and SgrA* (Goicoechea+, 2018)J/A+A/618/L10 : SgrA* orbital motions with GRAVITY (GRAVITY Col., 2018)J/A+A/621/A119 : SgrA* and NRAS530 86GHz images (Brinkerink+, 2019)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/863/15https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/863/15http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/863/15https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/863/15https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/863/15http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/863/15GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapInfrareddefaultJ/ApJ/863/15/table3Sgr A* light curve datarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObsObservatory/Instrument used in the observation (1)meta.id;instrcharHMJD[52803.1/57961] Heliocentric modified Julian Datedtime.epochdoubleFlux[-0.004/0.01] Excess flux density at position of Sgr A* (2)Jyphot.flux.density;em.IRdoubleRefFlux[-0.005/0.02]? Excess flux density of reference pixel (2)Jyphot.flux.density;em.IRdoublenullable