We observe the S-cluster star S62 on its Keplerian orbit around the supermassive black hole in the center of our galaxy, SgrA*. The orbital time period of S62 around SgrA* is 9.9 years. We derive its mass to be around 2 M_solar which is consistent with other members of the S-cluster. From the Lucy-Richardson deconvolved images, we determine a K-band magnitude of 16.1 mag. We observe almost two complete orbits of the star with two different and independent telescopes and three different instruments. The close distance of S62 to SgrA* at its periapse of around 2 mas results in a gravitational periapse shift of almost 10%/orbit.
The spin of the massive black hole (BH) at the center of the Milky Way, SgrA$^*$, has been poorly constrained so far. We place an upper limit on the spin of SgrA$^*$ based on the spatial distribution of the S-stars, which are arranged in two almost edge-on disks that are located at a position angle approximately $\pm 45^\circ$ with respect to the Galactic plane, on a milliparsec scale around the Galactic Center. Requiring that the frame-dragging precession has not had enough time to make the S-star orbital angular momentum precess, the spin of the massive BH at the center of the Milky Way can …
The center of the Milky Way hosts the closest supermassive black hole, SgrA$^*$. Decades of near-infrared observations of our Galactic Center have shown the presence of a small population of stars (the so called S-star cluster) orbiting SgrA$^*$, which were recently reported to be arranged in two orthogonal disks. In this case, the timescale for Lense-Thirring precession of S-stars should be longer than their age, implying a low spin for SgrA$^*$. In contrast, the recent results by the Event Horizon Telescope favor a highly-spinning SgrA$^*$, which seem to suggest that the S-stars could not be…
We report the detection of continuous positional and polarization changes of the compact source SgrA* in high states ('flares') of its variable near- infrared emission with the near-infrared GRAVITY-Very Large Telescope Interferometer (VLTI) beam-combining instrument. In three prominent bright flares, the position centroids exhibit clockwise looped motion on the sky, on scales of typically 150 micro-arcseconds over a few tens of minutes, corresponding to about 30% the speed of light. At the same time, the flares exhibit continuous rotation of the polarization angle, with about the same 45(+/-1…
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 of and distance to SgrA*. Our progress is not only due to the eight year increase in time base, but also due to the improved definition of the coordinate system. The star S2 continues to yield the best constraints on the mass of and distance to SgrA*; the statistical errors of 0.13 x 10^6 M_sun and 0.12 kpc have halved compared to the previous study. The S2 orbit fit is robust and does not need any prior informa…
The spin of the supermassive black hole that resides at the Galactic Centre can in principle be measured by accurate measurements of the orbits of stars that are much closer to SgrA* than S2, the orbit of which recently provided the measurement of the gravitational redshift and the Schwarzschild precession. The GRAVITY near-infrared interferometric instrument combining the four 8m telescopes of the VLT provides a spatial resolution of 2-4 mas, breaking the confusion barrier for adaptive-optics-assisted imaging with a single 8-10m telescope. We used GRAVITY to observe SgrA* over a period of six…
The effects of the spin and quadrupole moment of SgrA* on the orbits of S stars
LIRA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité（巴黎天文台，巴黎文理研究大学，法国国家科学研究中心，索邦大学，巴黎西岱大学）；Advanced Concepts Team, European Space Agency（欧洲空间局先进概念团队）
We present 1"-resolution ALMA observations of the circumnuclear disk (CND) and the environment around SgrA*. The images unveil the presence of small spatial scale CO (J=3-2) molecular "cloudlets" within the central pc of the Milky Way, moving at high speeds, up to 300 km/s along the line-of-sight. The CO-emitting structures show intricate morphologies: extended and filamentary at high negative-velocities (v_LSR < -150 km/s), more localized and clumpy at extreme positive-velocities (v_LSR > +200 km/s). Based on the pencil-beam CO absorption spectrum toward SgrA* synchrotron emission, we also pr…
We trace several dusty infrared sources on their orbit around the supermassive black hole (SMBH) SgrA* in the center of our galaxy. We give an overview of known and unknown sources in the direct vicinity of our SMBH in a radius of around 0.04pc. For that, we are using NACO (K- and L'-band) and SINFONI (H+K-band) data (VLT, Chile/Paranal) between 2002 and 2018. Our spectroscopic analysis reveals a Doppler-shifted line emission of Br_gamma and HeI. Additionally, we report the detection of [FeIII] lines that are found exclusively in the investigated dusty sources west of SgrA*. We speculate, that…
Despite the huge improvements guaranteed by future GRAVITY observations of the S0-2 star, these will not be able to unveil the fundamental nature, whether black hole or wormhole, of the central supermassive object. Nevertheless, observing stars orbiting closer to the central gravitational source could allow to distinguish between the black hole and wormhole nature of this object at more than 5$σ$. Firstly, we have used publicly available astrometric and spectroscopic measurements of the S0-2 star to constrain the metric around the supermassive object without finding any evidence either favouri…
Parametrized Post-Newtonian (PPN) equations of motion for several S-stars nearest to the Galactic Center compact relativistic object SgrA* are considered. The effect of the orbital periods difference between Newtonian and Post-Newtonian cases is taken into account. The best fit PN orbit of S2 has a period which is 16 days longer than Newtonian one. The PPN parameters $β_\text{PPN}$ and $γ_\text{PPN}$ are measured. Bayesian sampling is used to fit the trajectories of the PPN laws of motion. Posterior estimates of $β_\text{PPN}$ and $γ_\text{PPN}$ are $0.97^{+0.42}_{-0.65}$ and $0.81^{+0.46}_{-0…
We simulate the star cluster, made of stars in the main sequence and different black hole (BH) remnants, around SgrA* at the center of the Milky Way galaxy. Tracking stellar evolution, we find the BH remnant masses and construct the BH mass function. We sample 4 BH species and consider the impact of the mass-function in the dynamical evolution of system. Starting from an initial 6 dimensional family of parameters and using an MCMC approach, we find the best fits to various parameters of model by directly comparing the results of the simulations after $t = 10.5$ Gyrs with current observations o…
It has been recently demonstrated that both, a classical Schwarzschild black hole (BH), and a dense concentration of self-gravitating fermionic dark matter (DM) placed at the Galaxy centre, can explain the precise astrometric data (positions and radial velocities) of the S-stars orbiting SgrA*. This result encompasses the 17 best resolved S-stars, and includes the test of general relativistic effects such as the gravitational redshift in the S2-star. In addition, the DM model features another remarkable result: the dense core of fermions is the central region of a continuous density distributi…
The ongoing monitoring of the Galactic center and Sgr A*, the central supermassive black hole, produces surprising and unexpected findings. This goes hand in hand with the technical evolution of ground- and space-based telescopes and instruments, but also with the progression of image filter techniques such as the Lucy Richardson algorithm. As we continue to trace the members of the S cluster close to Sgr A* on their expected trajectory around the supermassive black hole, we present the finding of a new stellar source, which we call S4716. The newly found star orbits SgrA* in about 4.0 yr and …
Recent spectroscopic analysis has set an upper limit to the age of the S-stars, the ~30 B-type stars in highly eccentric orbits around the supermassive black hole (SMBH) in the Galactic center. The inferred age (<15 Myr) is in tension with the binary break-up scenario proposed to explain their origin. However, the new estimate is compatible with the age of the disk of O-type stars that lies at a farther distance from the SMBH. Here we investigate a new formation scenario, assuming that both S-stars and the O-type stars were born in the same disk around SgrA*. We simulate encounters between bin…
We present new absolute proper motion measurements for the Arches and Quintuplet clusters, two young massive star clusters near the Galactic center. Using multi-epoch HST observations, we construct proper motion catalogs for the Arches ($\sim$35,000 stars) and Quintuplet ($\sim$40,000 stars) fields in ICRF coordinates established using stars in common with the Gaia EDR3 catalog. The bulk proper motions of the clusters are measured to be ($μ_{α*}$, $μ_δ$) = (-0.80 $\pm$ 0.032, -1.89 $\pm$ 0.021) mas/yr for the Arches and ($μ_{α*}$, $μ_δ$) = (-0.96 $\pm$ 0.032, -2.29 $\pm$ 0.023) mas/yr for the …
Supermassive black holes in the centre of galaxies dominate the gravitational potential of their surrounding stellar clusters. In these dense environments, stars follow nearly Keplerian orbits, which get slowly distorted as a result of the potential fluctuations generated by the stellar cluster itself as a whole. In particular, stars undergo a rapid relaxation of their eccentricities through both resonant and non-resonant processes. An efficient implementation of the resonant diffusion coefficients allows for detailed and systematic explorations of the parameter space describing the properties…
We present a detailed analysis of the kinematics of 112 stars that mostly comprise the high velocity S-cluster and orbit the super massive black hole SgrA* at the center of the Milky Way. For 39 of them orbital elements are known, for the remainder we know proper motions. The distribution of inclinations, and proper motion flight directions deviate significantly from a uniform distribution which one expects if the orientation of the orbits are random. Across the central arcseconds the S-cluster stars are arranged in two almost edge on disks that are located at a position angle approximately +-…
Precise measurements of the S-stars orbiting SgrA* have set strong constraints on the nature of the compact object at the centre of the Milky Way. The presence of a black hole in that region is well established, but its neighboring environment is still an open debate. In that respect, the existence of dark matter in that central region may be detectable due to its strong signatures on the orbits of stars: the main effect is a Newtonian precession which will affect the overall pericentre shift of S2, the latter being a target measurement of the GRAVITY instrument. The exact nature of this dark …
We study the phase space structure and the orbital diffusion from the vicinity of the vertical Lyapunov periodic orbits around the unstable Lagrangian points L1,2 in a 3D barred galaxy model. By perturbing the initial conditions of these periodic orbits, we detected the following five types of orbital structures in the 4D spaces of section: (i) Ring-like structures, sticky for large time intervals to the unstable invariant manifolds of the simple and double unstable vertical Lyapunov periodic orbits. (ii) 2D tori belonging to quasi-periodic orbits around stable periodic orbits existing in the …
