A. Boehle

The Shortest-Known–Period Star Orbiting Our Galaxy’s Supermassive Black Hole

Close to a Black Hole At the center of our Galaxy, there is a black hole that is 4 million times as massive as the Sun. Using data from the Keck Observatory, Meyer et al. (p. 84) detected a star orbiting this black hole with a period of 11.5 years, the shortest period among the stars orbiting it. The star is the second well-sampled star with an orbital period under 20 years. Having detailed knowledge about two stars with short periods and full orbit coverage will be crucial in testing Einsteins theory of general relativity in the gravitational field close to a massive black hole. A star can help probe Einstein’s general relativity theory close to a black hole that is 4 million times as massive as the Sun. Stars with short orbital periods at the center of our Galaxy offer a powerful probe of a supermassive black hole. Over the past 17 years, the W. M. Keck Observatory has been used to image the galactic center at the highest angular resolution possible today. By adding to this data set and advancing methodologies, we have detected S0-102, a star orbiting our Galaxy’s supermassive black hole with a period of just 11.5 years. S0-102 doubles the number of known stars with full phase coverage and periods of less than 20 years. It thereby provides the opportunity, with future measurements, to resolve degeneracies in the parameters describing the central gravitational potential and to test Einstein’s theory of general relativity in an unexplored regime.

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

We present new, more precise measurements of the mass and distance of our Galaxys 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 two decades of speckle imaging and adaptive optics data. Specifically, we improve our analysis of the speckle images by using information about a stars 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 years) 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 (

Detection of Galactic Center source G2 at 3.8 μm during periapse passage

M_{bh}

The Post-periapsis Evolution of Galactic Center Source G1: The Second Case of a Resolved Tidal Interaction with a Supermassive Black Hole

) and distance (

New orbital analysis of stars at the Galactic center using speckle holography and orbital priors

R_o

Widespread Shocks in the Nucleus of NGC 404 Revealed by Near-infrared Integral Field Spectroscopy

) of Sgr A*:

Upgrade of the detector in the integral field spectrograph OSIRIS at the W. M. Keck Observatory

M_{bh} = 4.02\pm0.16\pm0.04\times10^6~M_{\odot}

Keck Observations of the Galactic Center Source G2: Gas Cloud or Star?

and

Testing General Relativity with Stellar Orbits around the Supermassive Black Hole in Our Galactic Center

7.86\pm0.14\pm0.04

The Keplerian orbit of G2

kpc. The uncertainties in