An Update on Monitoring Stellar Orbits in the Galactic Center

By S. Gillessen, P. Plewa, F. Eisenhauer, R. Sari, I. Waisberg, M. Habibi, O. Pfuhl, E. George, J. Dexter, S. Fellenberg and 2 more. 2016

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Using 25 years of data from uninterrupted monitoring of stellar orbits in the Galactic Center, we present an update of the main results from this unique data set: a measurement of mass and distance to Sgr A*. Our progress is not only due to the eight-year increase in time base, but also to the improved definition of the coordinate system. The star S2 continues to yield the best constraints on the mass of and distance to Sgr A*; the statistical errors of 0.13 × 10 6 M ⊙ and 0.12 kpc have halved compared to the previous study. The S2 orbit fit is robust and does not need any prior information. Using coordinate system priors, the star S1 also yields tight constraints on mass and distance. For a combined orbit fit, we use 17 stars, which yields our current best estimates for mass and distance: M = 4.28 ± 0.10 ∣ stat . ± 0.21 ∣ sys × 10 6 M ⊙ and R 0 = 8.32 ± 0.07 ∣ stat . ± 0.14 ∣ sys kpc . These numbers are in agreement with the recent determination of R0 from the statistical cluster parallax. The positions of the mass, of the near-infrared flares from Sgr A*, and of the radio source Sgr A* agree to within 1 mas. In total, we have determined orbits for 40 stars so far, a sample which consists of 32 stars with randomly oriented orbits and a thermal eccentricity distribution, plus eight stars that we can explicitly show are members of the clockwise disk of young stars, and which have lower-eccentricity orbits.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/5c6995083d87356855e1836f423c26cf2c6d950e

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Citations in the corpus

First light for GRAVITY: Phase referencing optical interferometry for the Very Large Telescope Interferometer (2017, background): “It orbits Sgr A* with a period of 16 years (Schödel et al. 2002; Ghez et al. 2008; Gillessen et al. 2017) and reaches a velocity of up to 7600 km s − 1 , that is, 2.5% the speed of light, which makes it a prime candidate to study general relativistic orbit e ﬀ ects close to a supermassive black…”
Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole (2018, methodology): “Any extended mass within the S2 orbit is lower than about 1 % of the central mass (Hees et al. 2017; Gillessen et al. 2017).”
On the charge of the Galactic centre black hole (2018, background): “…for the density of the dark mass comes from the monitoring of Btype star S2 with the pericentre distance of rP ' 5.8 × 10−4 pc (Parsa et al. 2017; Schödel et al. 2002; Gillessen et al. 2009, 2017; Gravity Collaboration et al. 2018) ρS2 = 5.2×1015 ( M• 4.3× 106 M )( rP 5.8× 10−4 pc )−3 M pc −3 .”
Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole (2020, background): “The phases of the complex visibilities of each pointing then yield an accurate distance to the fringe-tracking star, IRS16C in our case.”
A geometric distance measurement to the Galactic center black hole with 0.3% uncertainty (2019, methodology): “…LESIA of Paris Observatory/CNRS/UPMC/Univ. Paris Diderot and IPAG of Université Grenoble Alpes/CNRS, the Max Planck Institute for Astronomy, the University of Cologne, the Centro de Astrofísica e Gravitaçâo, and the European Southern Observatory. and a few thousand years (Gillessen et al. 2017).”