Polarimetry and Astrometry of NIR Flares as Event Horizon Scale, Dynamical Probes for the Mass of Sgr A*. (arXiv:2307.11821v1 [astro-ph.GA])

Polarimetry and Astrometry of NIR Flares as Event Horizon Scale, Dynamical Probes for the Mass of Sgr A*. (arXiv:2307.11821v1 [astro-ph.GA])
The <a href="http://arxiv.org/find/astro-ph/1/au:+Collaboration_GRAVITY/0/1/0/all/0/1">GRAVITY Collaboration</a>: <a href="http://arxiv.org/find/astro-ph/1/au:+Abuter_R/0/1/0/all/0/1">R. Abuter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aimar_N/0/1/0/all/0/1">N. Aimar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Seoane_P/0/1/0/all/0/1">P. Amaro Seoane</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Amorim_A/0/1/0/all/0/1">A. Amorim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Baubock_M/0/1/0/all/0/1">M. Bauböck</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Berger_J/0/1/0/all/0/1">J.P. Berger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bonnet_H/0/1/0/all/0/1">H. Bonnet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bourdarot_G/0/1/0/all/0/1">G. Bourdarot</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brandner_W/0/1/0/all/0/1">W. Brandner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cardoso_V/0/1/0/all/0/1">V. Cardoso</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Clenet_Y/0/1/0/all/0/1">Y. Clénet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Davies_R/0/1/0/all/0/1">R. Davies</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zeeuw_P/0/1/0/all/0/1">P.T. de Zeeuw</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dexter_J/0/1/0/all/0/1">J. Dexter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Drescher_A/0/1/0/all/0/1">A. Drescher</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Eckart_A/0/1/0/all/0/1">A. Eckart</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Eisenhauer_F/0/1/0/all/0/1">F. Eisenhauer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Feuchtgruber_H/0/1/0/all/0/1">H. Feuchtgruber</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Finger_G/0/1/0/all/0/1">G. Finger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schreiber_N/0/1/0/all/0/1">N.M. Förster Schreiber</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Foschi_A/0/1/0/all/0/1">A. Foschi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Garcia_P/0/1/0/all/0/1">P. Garcia</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gao_F/0/1/0/all/0/1">F. Gao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gelles_Z/0/1/0/all/0/1">Z. Gelles</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gendron_E/0/1/0/all/0/1">E. Gendron</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Genzel_R/0/1/0/all/0/1">R. Genzel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gillessen_S/0/1/0/all/0/1">S. Gillessen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hartl_M/0/1/0/all/0/1">M. Hartl</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Haubois_X/0/1/0/all/0/1">X. Haubois</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Haussmann_F/0/1/0/all/0/1">F. Haussmann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Heissel_G/0/1/0/all/0/1">G. Heißel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Henning_T/0/1/0/all/0/1">T. Henning</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hippler_S/0/1/0/all/0/1">S. Hippler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Horrobin_M/0/1/0/all/0/1">M. Horrobin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jochum_L/0/1/0/all/0/1">L. Jochum</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jocou_L/0/1/0/all/0/1">L. Jocou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kaufer_A/0/1/0/all/0/1">A. Kaufer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kervella_P/0/1/0/all/0/1">P. Kervella</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lacour_S/0/1/0/all/0/1">S. Lacour</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lapeyrere_V/0/1/0/all/0/1">V. Lapeyrère</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bouquin_J/0/1/0/all/0/1">J.-B. Le Bouquin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lena_P/0/1/0/all/0/1">P. Léna</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lutz_D/0/1/0/all/0/1">D. Lutz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mang_F/0/1/0/all/0/1">F. Mang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+More_N/0/1/0/all/0/1">N. More</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ott_T/0/1/0/all/0/1">T. Ott</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Paumard_T/0/1/0/all/0/1">T. Paumard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Perraut_K/0/1/0/all/0/1">K. Perraut</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Perrin_G/0/1/0/all/0/1">G. Perrin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pfuhl_O/0/1/0/all/0/1">O. Pfuhl</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rabien_S/0/1/0/all/0/1">S. Rabien</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ribeiro_D/0/1/0/all/0/1">D. C. Ribeiro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bordoni_M/0/1/0/all/0/1">M. Sadun Bordoni</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Scheithauer_S/0/1/0/all/0/1">S. Scheithauer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shangguan_J/0/1/0/all/0/1">J. Shangguan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shimizu_T/0/1/0/all/0/1">T. Shimizu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stadler_J/0/1/0/all/0/1">J. Stadler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Straub_O/0/1/0/all/0/1">O. Straub</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Straubmeier_C/0/1/0/all/0/1">C. Straubmeier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sturm_E/0/1/0/all/0/1">E. Sturm</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tacconi_L/0/1/0/all/0/1">L.J. Tacconi</a>, et al. (7 additional authors not shown)

We present new astrometric and polarimetric observations of flares from Sgr
A* obtained with GRAVITY, the near-infrared interferometer at ESO’s Very Large
Telescope Interferometer (VLTI), bringing the total sample of well-covered
astrometric flares to four and polarimetric ones to six, where we have for two
flares good coverage in both domains. All astrometric flares show clockwise
motion in the plane of the sky with a period of around an hour, and the
polarization vector rotates by one full loop in the same time. Given the
apparent similarities of the flares, we present a common fit, taking into
account the absence of strong Doppler boosting peaks in the light curves and
the EHT-measured geometry. Our results are consistent with and significantly
strengthen our model from 2018: We find that a) the combination of polarization
period and measured flare radius of around nine gravitational radii ($9 R_g
approx 1.5 R_{ISCO}$, innermost stable circular orbit) is consistent with
Keplerian orbital motion of hot spots in the innermost accretion zone. The mass
inside the flares’ radius is consistent with the $4.297 times 10^6 ;
text{M}_odot$ measured from stellar orbits at several thousand $R_g$. This
finding and the diameter of the millimeter shadow of Sgr A* thus support a
single black hole model. Further, b) the magnetic field configuration is
predominantly poloidal (vertical), and the flares’ orbital plane has a moderate
inclination with respect to the plane of the sky, as shown by the non-detection
of Doppler-boosting and the fact that we observe one polarization loop per
astrometric loop. Moreover, c) both the position angle on sky and the required
magnetic field strength suggest that the accretion flow is fueled and
controlled by the winds of the massive, young stars of the clockwise stellar
disk 1-5 arcsec from Sgr A*, in agreement with recent simulations.

http://arxiv.org/icons/sfx.gif