Detection of faint stars near SgrA* with GRAVITY

Abstract

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 months in 2019 and employed interferometric reconstruction methods developed in radio astronomy to search for faint objects near SgrA*. This revealed a slowly moving star of magnitude 18.9 in K band within 30mas of SgrA*. The position and proper motion of the star are consistent with the previously known star S62, which is at a substantially larger physical distance, but in projection passes close to SgrA*. Observations in August and September 2019 easily detected S29, with K-magnitude of 16.6, at approximately 130 mas from SgrA*. The planned upgrades of GRAVITY, and further improvements in the calibration, hold the promise of finding stars fainter than magnitude 19 at K.

arXiv comment12 pages, 11 figures, published in A&A. Here we updated Fig. 1 with the latest motions laws of the S-stars as obtained from VLT/NACO observations until end 2019

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• First Sagittarius A* Event Horizon Telescope Results. VI: Testing the Black Hole Metric
• Tests of Loop Quantum Gravity from the Event Horizon Telescope Results of Sgr A${}^{\ast }$
• Polarimetry and Astrometry of NIR Flares as Event Horizon Scale, Dynamical Probes for the Mass of Sgr A*
• An Upper Limit on the Charge of the Black Hole Sgr A* from EHT Observations
• Probing the Lorentz Symmetry Violation Using the First Image of Sagittarius A*: Constraints on Standard-Model Extension Coefficients
• The dark mass signature in the orbit of S2
• Investigating effects of dark matter on photon orbits and black hole shadows
• Exploring dark matter spike distribution around the Galactic centre with stellar orbits
• Observation of S4716 -- a Star with a 4 yr Orbit around Sgr A*
• Reconnection-driven flares in 3D black hole magnetospheres -- A scenario for hot spots around Sagittarius A*
• Unveiling the nature of SgrA* with the geodesic motion of S-stars
• Deep Images of the Galactic Center with GRAVITY
• Testing EGB gravity coupled to bumblebee field and black hole parameter estimation with EHT observations
• The Galactic Center as a laboratory for theories of gravity and dark matter
• Multi-wavelength Variability of Sagittarius A* in July 2019
• Mapping the Galactic centre's dark cluster via Resonant Relaxation
• Observation of the apoapsis of S62 in 2019 with NIRC2 and SINFONI
• Orbital alignment and mass segregation in galactic nuclei via vector resonant relaxation
• Central X-ray point-sources found to be abundant in low-mass, late-type galaxies predicted to contain an intermediate-mass black hole
• The impact of gravitational lensing in the reconstruction of stellar orbits around Sgr A*
• Revisiting Stellar Orbits and the Sgr A${}^{\ast }$ Quadrupole Moment
• Determination of the angular momentum of the Kerr black hole from equatorial geodesic motion
• Shadows of generalised Hayward spacetimes : in vacuum and with plasma