@article{12079,
  author = {R. Abuter and A. Amorim and M. Bauboeck and H. Bonnet and W. Brandner and V. Cardoso and Y. Clenet and P. de Zeeuw and Jason Dexter and A. Eckart and Frank Eisenhauer and N. Schreiber and P. Garcia and F. Gao and E. Gendron and R. Genzel and S. Gillessen and M. Habibi and X. Haubois and T. Henning and S. Hippler and M. Horrobin and L. Jocou and Alejandra Jimenez-Rosales and L. Jochum and L. Jocou and A. Kaufer and P. Kervella and S. Lacour and V. Lapeyrère and J. Le Bouquin and P. Léna and M. Nowak and T. Ott and T. Paumard and K. Perraut and G. Perrin and Oliver Pfuhl and G. Ponti and Rodriguez Coira and J. Shangguan and S. Scheithauer and J. Stadler and O. Straub and C. Straubmeier and E. Sturm and L. Tacconi and K. Tristram and F. Vincent and S. von Fellenberg and I. Waisberg and F. Widmann and E. Wieprecht and E. Wiezorrek and J. Woillez and S. Yazici and G. Zins},
  title = {The Flux Distribution of Sgr A*},
  abstract = {The Galactic Center black hole Sagittarius A* is a variable NIR source that exhibits bright flux excursions called flares. The low-flux density turnover of the flux distribution is below the sensitivity of current single-aperture telescopes. We use the unprecedented resolution of the GRAVITY instrument at the VLTI. Our light curves are unconfused, overcoming the confusion limit of previous photometric studies. We analyze the light curves using standard statistical methods and obtain the flux distribution. We find that the flux distribution of SgrA* turns over at a median flux density of (1.1\pm0.3)mJy. We measure the percentiles of the flux distribution and use them to constrain the NIR K-band SED. Furthermore, we find that the flux distribution is intrinsically right-skewed to higher flux density in log space. Flux densities below 0.1mJy are hardly ever observed. In consequence, a single powerlaw or lognormal distribution does not suffice to describe the observed flux distribution in its entirety. However, if one takes into account a power law component at high flux densities, a lognormal distribution can describe the lower end of the observed flux distribution. We confirm the RMS-flux relation for Sgr~A* and find it to be linear for all flux densities in our observation. We conclude that Sgr~A* has two states: the bulk of the emission is generated in a lognormal process with a well-defined median flux density and this quiescent emission is supplemented by sporadic flares that create the observed power law extension of the flux distribution.},
  year = {2020},
  journal = {Astronomy & Astrophysics},
  volume = {638},
  pages = {A2},
  month = {2020-06},
  url = {https://www.aanda.org/articles/aa/full_html/2020/06/aa37717-20/aa37717-20.html},
  doi = {10.1051/0004-6361/202037717},
}