Performance of astrometric detection of a hotspot orbiting on the innermost stable circular orbit of the galactic centre black hole

Abstract

The galactic central black hole Sgr A* exhibits outbursts of radiation in the near infrared (so-called IR flares). One model of these events consists in a hotspot orbiting on the innermost stable circular orbit (ISCO) of the hole. These outbursts can be used as a probe of the central gravitational potential. One main scientific goal of the second generation VLTI instrument GRAVITY is to observe these flares astrometrically. Here, the astrometric precision of GRAVITY is investigated in imaging mode, which consists in analysing the image computed from the interferometric data. The capability of the instrument to put in light the motion of a hotspot orbiting on the ISCO of our central black hole is then discussed. We find that GRAVITY's astrometric precision for a single star in imaging mode is smaller than the Schwarzschild radius of Sgr A*. The instrument can also demonstrate that a body orbiting on the last stable orbit of the black hole is indeed moving. It yields a typical size of the orbit, if the source is as bright as m_K=14. These results show that GRAVITY allows one to study the close environment of Sgr A*. Having access to the ISCO of the central massive black hole probably allows constraining general relativity in its strong regime. Moreover, if the hotspot model is appropriate, the black hole spin can be constrained.

13 pages, 11 figures ; accepted by MNRAS

References in corpus (6)

• The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics and Formation
• Testing the general relativistic ''no-hair'' theorems using the galactic center black hole SgrA*
• Flaring Activity of Sgr A* at 43 and 22 GHz: Evidence for Expanding Hot Plasma
• Imaging the spotty surface of Betelgeuse in the H band
• Modeling mm- to X-ray flare emission from SgrA*
• A self-calibration approach for optical long baseline interferometry imaging

Cited by in corpus (17)

• Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA*
• A Quantitative Test of the No-Hair Theorem with Sgr A* using stars, pulsars, and the Event Horizon Telescope
• Sgr A* and General Relativity
• The Milky Way's Supermassive Black Hole: How good a case is it? A Challenge for Astrophysics & Philosophy of Science
• Testing the No-Hair Theorem with Observations of Black Holes in the Electromagnetic Spectrum
• Perturbed stellar motions around the rotating black hole in Sgr A* for a generic orientation of its spin axis
• Distinguishing black holes and wormholes with orbiting hot spots
• What stellar orbit is needed to measure the spin of the Galactic center black hole from astrometric data?
• Testing the nature of the supermassive black hole candidate in SgrA* with light curves and images of hot spots
• Relative Astrometry of Compact Flaring Structures in Sgr A* with Polarimetric VLBI
• Distinguishing an ejected blob from alternative flare models at the Galactic centre with GRAVITY
• Exploiting spatial sparsity for multi-wavelength imaging in optical interferometry
• Constraining the Cardoso-Pani-Rico metric with future observations of SgrA${}^{\ast }$
• Assessing the quality of restored images in optical long-baseline interferometry
• The nearby eclipsing stellar system delta Velorum - IV. Differential astrometry with VLT/NACO at the 100 microarcsecond level
• Disentangling Confused Stars at the Galactic Center with Long Baseline Infrared Interferometry
• Measuring the Direction and Angular Velocity of a Black Hole Accretion Disk via Lagged Interferometric Covariance