The flux distribution of Sgr A*

Abuter, R.; Amorim, A.; Bauböck, M.; Berger, J. B.; Bonnet, H.; Brandner, W.; Cardoso, V.; Clénet, Y.; de Zeeuw, P. T.; Dallilar, Y.; Dexter, J.; Eckart, A.; Eisenhauer, F.; Förster Schreiber, N. M.; Garcia, P.; Gao, F.; Gendron, E.; Genzel, R.; Gillessen, S.; Habibi, M.; Haubois, X.; Henning, T.; Hippler, S.; Horrobin, M.; Jiménez-Rosales, A.; Jochum, L.; Jocou, L.; Kaufer, A.; Kervella, P.; Lacour, S.; Lapeyrère, V.; Le Bouquin, J.-B.; Léna, P.; Nowak, M.; Ott, T.; Paumard, T.; Perraut, K.; Perrin, G.; Pfuhl, O.; Ponti, G.; Coira, G. Rodriguez; Shangguan, J.; Scheithauer, S.; Stadler, J.; Straub, O.; Straubmeier, C.; Sturm, E.; Tacconi, L. J.; Vincent, F.; Fellenberg, S. D. von; Waisberg, I.; Widmann, F.; Wieprecht, E.; Wiezorrek, E.; Woillez, J.; Yazici, S.; Zins, G.

doi:10.1051/0004-6361/202037717

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The flux distribution of Sgr A*

MPG-Autoren

/persons/resource/persons216131

Bauböck, M.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons225865

de Zeeuw, P. T.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons250315

Dallilar, Y.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons146381

Dexter, J.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons4766

Eisenhauer, F.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons4923

Förster Schreiber, N. M.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons214427

Gao, F.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons4590

Genzel, R.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons4768

Gillessen, S.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons181377

Habibi, M.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons216133

Jiménez-Rosales, A.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons16190

Ott, T.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons4782

Pfuhl, O.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons82450

Ponti, G.
High Energy Astrophysics, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons232571

Shangguan, J.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons248280

Stadler, J.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons232635

Straub, O.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons4650

Sturm, E.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons4582

Tacconi, L. J.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons206120

Fellenberg, S. D. von
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons214431

Widmann, F.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons16329

Wieprecht, E.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons16335

Wiezorrek, E.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons203013

Yazici, S.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

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Zitation

Abuter, R., Amorim, A., Bauböck, M., Berger, J. B., Bonnet, H., Brandner, W., et al. (2020). The flux distribution of Sgr A*. Astronomy and Astrophysics, 638: A2. doi:10.1051/0004-6361/202037717.

Zitierlink: https://hdl.handle.net/21.11116/0000-0006-EE1B-1

Zusammenfassung

The Galactic center black hole Sagittarius A* is a variable near-infrared (NIR) source that exhibits bright flux excursions called flares. When flux from Sgr A* is detected, the light curve has been shown to exhibit red noise characteristics and the distribution of flux densities is non-linear, non-Gaussian, and skewed to higher flux densities. However, the low-flux density turnover of the flux distribution is below the sensitivity of current single-aperture telescopes. For this reason, the median NIR flux has only been inferred indirectly from model fitting, but it has not been directly measured. In order to explore the lowest flux ranges, to measure the median flux density, and to test if the previously proposed flux distributions fit the data, we use the unprecedented resolution of the GRAVITY instrument at the VLTI. We obtain light curves using interferometric model fitting and coherent flux measurements. 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 Sgr A* turns over at a median flux density of (1.1 ± 0.3) mJy. We measure the percentiles of the flux distribution and use them to constrain the NIR K-band spectral energy distribution. Furthermore, we find that the flux distribution is intrinsically right-skewed to higher flux density in log space. Flux densities below 0.1 mJy 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.