AN IMPROVED DISTANCE AND MASS ESTIMATE FOR SGR A* FROM A MULTISTAR ORBIT ANALYSIS

By A. Boehle, A. Ghez, R. Schödel, L. Meyer, S. Yelda, Saundra M Albers, G. Martinez, E. Becklin, T. Do, Jessica R. Lu and 4 more. 2016

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We present new, more precise measurements of the mass and distance of our Galaxy’s central supermassive black hole, Sgr A*. These results stem from a new analysis that more than doubles the time baseline for astrometry of faint stars orbiting Sgr A*, combining 2 decades of speckle imaging and adaptive optics data. Specifically, we improve our analysis of the speckle images by using information about a star’s orbit from the deep adaptive optics data (2005–2013) to inform the search for the star in the speckle years (1995–2005). When this new analysis technique is combined with the first complete re-reduction of Keck Galactic Center speckle images using speckle holography, we are able to track the short-period star S0-38 (K-band magnitude = 17, orbital period = 19 yr) through the speckle years. We use the kinematic measurements from speckle holography and adaptive optics to estimate the orbits of S0-38 and S0-2 and thereby improve our constraints of the mass (Mbh) and distance (Ro) of Sgr A*: Mbh = (4.02 ± 0.16 ± 0.04) × 106 M⊙ and 7.86 ± 0.14 ± 0.04 kpc. The uncertainties in Mbh and Ro as determined by the combined orbital fit of S0-2 and S0-38 are improved by a factor of 2 and 2.5, respectively, compared to an orbital fit of S0-2 alone and a factor of ∼2.5 compared to previous results from stellar orbits. This analysis also limits the extended dark mass within 0.01 pc to less than 0.13 × 106 M⊙ at 99.7% confidence, a factor of 3 lower compared to prior work.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/3fd394a07ee7a951f1b3445b8f99b4316fd97f40

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Citations in the corpus

Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole (2020, background): “They determined increasingly precise motions for more than 104 stars, and orbits for ≈ 50 (Schödel et al. 2002; Ghez et al. 2003, 2008; Eisenhauer et al. 2005; Gillessen et al. 2009b; Schödel et al. 2009; Meyer et al. 2012; Boehle et al. 2016; Fritz et al. 2016; Gillessen et al. 2017).”
Phenomenological aspects of black holes beyond general relativity (2018, background): “On the other hand, this region has been extensively studied during more than two decades [99–104], with the result that the trajectories of a large number of orbiting stars are known with excellent precision [105, 106].”
Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole (2018, methodology): “We do not use the ’combined’ data set in the sense of Gillessen et al. (2009a), that is, we do not include the astrometric data set presented in Boehle et al. (2016), but use NTT and VLT astrometry only.”
An Update on Monitoring Stellar Orbits in the Galactic Center (2016, methodology): “We also repeat the fit from Gillessen et al. (2009a) in row 3 of table 1, which includes into our data set the publicly available S2 data from Boehle et al. (2016).”
A geometric distance measurement to the Galactic center black hole with 0.3% uncertainty (2019, unknown): “The value from Boehle et al. (2016), R0 = 7.86 ± 0.14 ± 0.04 kpc, disagrees with our result.”
The mass distribution and gravitational potential of the Milky Way (2016, background): “…interest, however, that a more recent analysis of the astrometry of faint stars orbiting Sgr A*, combining two different types of imaging over a time baseline of two decades finds a lower value ofR0 = (7.86±0.14±0.04) kpc (statistical and systematic uncertainties respectively,Boehle et al. 2016).”
On the charge of the Galactic centre black hole (2018, background): “Based on these and follow-up observations (Boehle et al. 2016; Parsa et al. 2017; Gillessen et al. 2009, 2017; Gravity Collaboration et al. 2018), the large mass of the dark object has been confirmed and a more precise value has been ?”
THE SHAPE OF THE INNER MILKY WAY HALO FROM OBSERVATIONS OF THE PAL 5 AND GD–1 STELLAR STREAMS (2016, methodology): “Based on recent measurements of R0 (Chatzopoulos et al. 2015; Bland-Hawthorn & Gerhard 2016; Boehle et al. 2016), we use the constraint R0 = 8.1 ± 0.1 kpc.”
Stellar Dynamics and Stellar Phenomena Near a Massive Black Hole (2017, background): “Sgr A?, the M• ' 4 × 106 M MBH at the center of the Milky Way, R0 ' 8 kpc from the Solar system (Gillessen et al. 2009; Boehle et al. 2016), is the nearest MBH to us.”