Deep Images of the Galactic Center with GRAVITY

Abstract

Stellar orbits at the Galactic Center provide a very clean probe of the gravitational potential of the supermassive black hole. They can be studied with unique precision, beyond the confusion limit of a single telescope, with the near-infrared interferometer GRAVITY. Imaging is essential to search the field for faint, unknown stars on short orbits which potentially could constrain the black hole spin. Furthermore, it provides the starting point for astrometric fitting to derive highly accurate stellar positions. Here, we present ${\mathrm{G}}^{\mathrm{R}}$, a new imaging tool specifically designed for Galactic Center observations with GRAVITY. The algorithm is based on a Bayesian interpretation of the imaging problem, formulated in the framework of information field theory and building upon existing works in radio-interferometric imaging. Its application to GRAVITY observations from 2021 yields the deepest images to date of the Galactic Center on scales of a few milliarcseconds. The images reveal the complicated source structure within the central $100\mathrm{mas}$ around Sgr A*, where we detected the stars S29 and S55 and confirm S62 on its trajectory, slowly approaching Sgr A*. Furthermore, we were able to detect S38, S42, S60, and S63 in a series of exposures for which we offset the fiber from Sgr A*. We provide an update on the orbits of all aforementioned stars. In addition to these known sources, the images also reveal a faint star moving to the west at a high angular velocity. We cannot find any coincidence with any known source and, thus, we refer to the new star as S300. From the flux ratio with S29, we estimate its K-band magnitude as $m_{\mathrm{K}}\left(S300\right)\simeq 19.0-19.3$. Images obtained with CLEAN confirm the detection.

arXiv comment24 pages, 14 figures

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Cited by in corpus (12)

• Polarimetry and Astrometry of NIR Flares as Event Horizon Scale, Dynamical Probes for the Mass of Sgr A*
• The Extremely Large Telescope
• Observation of S4716 -- a Star with a 4 yr Orbit around Sgr A*
• First Light for GRAVITY Wide: Large Separation Fringe Tracking for the Very Large Telescope Interferometer
• Performance and first measurements of the MAGIC Stellar Intensity Interferometer
• Shadow of Kottler black hole in the presence of plasma for a co-moving observer
• Future prospects for measuring 1PPN parameters using observations of S2 and S62 at the Galactic Center
• The impact of gravitational lensing in the reconstruction of stellar orbits around Sgr A*
• fast-resolve: Fast Bayesian Radio Interferometric Imaging
• Analytic Post-Newtonian Astrometric and Spectroscopic Models of Orbits around Black Holes
• Testing General Relativity with Binary Lens Microlensing Events
• Binary Dynamics and Mergers in a Stellar Disk and the Formation of Dusty Objects in the Galactic Center