Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA*

We report the detection of continuous positional and polarization changes of the compact source SgrA* in high states (“flares”) of its variable near-infrared emission with the near-infrared GRAVITY-Very Large Telescope Interferometer (VLTI) beam-combining instrument. In three prominent bright flares, the position centroids exhibit clockwise looped motion on the sky, on scales of typically 150 μas over a few tens of minutes, corresponding to about 30% the speed of light. At the same time, the flares exhibit continuous rotation of the polarization angle, with about the same 45(±15) min period as that of the centroid motions. Modelling with relativistic ray tracing shows that these findings are all consistent with a near face-on, circular orbit of a compact polarized “hot spot” of infrared synchrotron emission at approximately six to ten times the gravitational radius of a black hole of 4 million solar masses. This corresponds to the region just outside the innermost, stable, prograde circular orbit (ISCO) of a Schwarzschild–Kerr black hole, or near the retrograde ISCO of a highly spun-up Kerr hole. The polarization signature is consistent with orbital motion in a strong poloidal magnetic field.

S. Rabien | T. Paumard | L. Jocou | K. Perraut | G. Duvert | A. Amorim | A. Eckart | G. Rousset | M. Habibi | R. Genzel | E. Wieprecht | H. Bonnet | P. Kervella | S. Gillessen | S. von Fellenberg | A. Huber | J. Panduro | G. Perrin | C. Straubmeier | X. Haubois | Th. Henning | J. Woillez | S. Yazici | F. Eisenhauer | J. Dexter | F. Widmann | E. Wiezorrek | E. Gendron | C. Deen | W. Brandner | O. Pfuhl | M. Lippa | T. Ott | E. Sturm | V. Lapeyrere | O. Straub | I. Waisberg | S. Lacour | B. Lazareff | G. Perrin | G. Rousset | R. Abuter | T. Henning | W. Brandner | S. Lacour | S. Hippler | J. Woillez | H. Bonnet | A. Sternberg | J. Berger | G. Duvert | A. Eckart | E. Gendron | R. Genzel | J. Dexter | S. Hippler | F. Eisenhauer | N. Schreiber | T. Paumard | P. Kervella | A. Huber | J. Panduro | K. Perraut | J. Bouquin | L. Tacconi | S. Gillessen | T. Ott | S. Rabien | P. Garcia | E. Sturm | O. Pfuhl | F. Gao | M. Horrobin | P. Plewa | M. Habibi | E. Wieprecht | E. Wiezorrek | L. J. Tacconi | A. Sternberg | B. Lazareff | J. P. Berger | V. Coud'e du Foresto | J.-B. Le Bouquin | N. M. Forster Schreiber | S. Hippler | P. T. de Zeeuw | GRAVITY Collaboration R. Abuter | M. Baubock | Y. Cl'enet | P. Garcia | F. Gao | P. Guajardo | M. Horrobin | A. Jim'enez-Rosales | P. L'ena | P. M. Plewa | G. Rodr'iguez-Coira | F. Vincent | V. C. D. Foresto | L. Jocou | A. Amorim | M. Bauböck | P. Garcia | X. Haubois | A. Jiménez-Rosales | V. Lapeyrère | O. Straub | C. Straubmeier | F. Vincent | I. Waisberg | F. Widmann | S. Yazici | G. C. R. Abuter | M. Baubock | Y. Cl'enet | C. Deen | P. L'ena | M. Lippa | G. Rodr'iguez-Coira | S. Fellenberg | W. Brandner | P. Guajardo | A. Jim'enez-Rosales | S. V. Fellenberg | P. Zeeuw | J. L. Bouquin | N. F. Schreiber | Y. Clénet | T. Ott

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