Mass distribution in the Galactic Center based on interferometric astrometry of multiple stellar orbits

Abstract

Stars orbiting the compact radio source Sgr A* in the Galactic Center serve as precision probes of the gravitational field around the closest massive black hole. In addition to adaptive optics-assisted astrometry (with NACO/VLT) and spectroscopy (with SINFONI/VLT, NIRC2/Keck and GNIRS/Gemini) over three decades, we have obtained 30–100 μas astrometry since 2017 with the four-telescope interferometric beam combiner GRAVITY/VLTI, capable of reaching a sensitivity of mK = 20 when combining data from one night. We present the simultaneous detection of several stars within the diffraction limit of a single telescope, illustrating the power of interferometry in the field. The new data for the stars S2, S29, S38, and S55 yield significant accelerations between March and July 2021, as these stars pass the pericenters of their orbits between 2018 and 2023. This allows for a high-precision determination of the gravitational potential around Sgr A*. Our data are in excellent agreement with general relativity orbits around a single central point mass, M• = 4.30 × 106 M⊙, with a precision of about ±0.25%. We improve the significance of our detection of the Schwarzschild precession in the S2 orbit to 7σ. Assuming plausible density profiles, the extended mass component inside the S2 apocenter (≈0.23″ or 2.4 × 104 RS) must be ≲3000 M⊙ (1σ), or ≲0.1% of M•. Adding the enclosed mass determinations from 13 stars orbiting Sgr A* at larger radii, the innermost radius at which the excess mass beyond Sgr A* is tentatively seen is r ≈ 2.5″ ≥ 10× the apocenter of S2. This is in full harmony with the stellar mass distribution (including stellar-mass black holes) obtained from the spatially resolved luminosity function.

Deflection and Gravitational lensing of null and timelike signals in the Kiselev black hole spacetime in the weak field limit

“…4 we plot θ ± by assuming that the lens has a mass M = 4.30 × 10 6 M of Sgr A* supermassive BH and r s = r d = 8.28 [kpc] equals its distance to us. We assume that α = 0.25%M 1+3ω which is within the uncertainty of the Sgr A* mass when ω = 0 [48]. From the top panel we see that as β deviates from zero, the θ + and θ − separate from each other with the former increases while the latter decreases.…”

Effect of electric interaction on the deflection and gravitational lensing in the strong field limit

“…6 we plot them for the SgrA* SMBH by assuming it is a RN BH and the shadow is formed by cosmic protons. We take the proton energy to be 10 19 [eV] and the SgrA* SMBH mass M = 4.30 × 10 6 M and source/detector distance r s = r d = 8.28 [kpc] to be the distance to us [50]. For the BH charge, we use the magnetically induced charge…”

Observing GW190521-like binary black holes and their environment with LISA

“…For this particular system, we can determine the mass of SMBH to about 8% level and the orbital inclination within a few degrees, together with the separation of the outer orbit within 3%. Comparably precise SMBH mass measurements are currently possible only for SgrA * [74], M87 [75], and an handful of galaxies with detected nuclear megamaser emission [76]. GW190521-like binaries detected by LISA would therefore provide a competitive, complementary opportunity to measure SMBH masses through GW observations.…”