Publications by authors named "A Ghez"
Article Synopsis
- Sgr A* is a supermassive black hole at the center of the Milky Way that varies in its emissions of X-ray, near-infrared, and submillimeter radiation, making it a key subject for studying black hole accretion processes.
- Recent observations revealed two flares that challenge existing models of how these emissions are correlated over time, suggesting that the timing and mechanisms behind these emissions are more complex than previously thought.
- The findings highlight the need for ongoing, detailed multiwavelength studies to deepen our understanding of the fluctuations in emissions from Sgr A* and the processes at play.
Searching for space-time variations of the constants of Nature is a promising way to search for new physics beyond general relativity and the standard model motivated by unification theories and models of dark matter and dark energy. We propose a new way to search for a variation of the fine-structure constant using measurements of late-type evolved giant stars from the S star cluster orbiting the supermassive black hole in our Galactic Center. A measurement of the difference between distinct absorption lines (with different sensitivity to the fine structure constant) from a star leads to a direct estimate of a variation of the fine structure constant between the star's location and Earth.
View Article and Find Full Text PDFThe central 0.1 parsecs of the Milky Way host a supermassive black hole identified with the position of the radio and infrared source Sagittarius A* (refs. ), a cluster of young, massive stars (the S stars) and various gaseous features.
View Article and Find Full Text PDFThe general theory of relativity predicts that a star passing close to a supermassive black hole should exhibit a relativistic redshift. In this study, we used observations of the Galactic Center star S0-2 to test this prediction. We combined existing spectroscopic and astrometric measurements from 1995-2017, which cover S0-2's 16-year orbit, with measurements from March to September 2018, which cover three events during S0-2's closest approach to the black hole.
View Article and Find Full Text PDFSagittarius A* (Sgr A*) is the variable radio, near-infrared (NIR), and X-ray source associated with accretion onto the Galactic center black hole. We present an analysis of the most comprehensive NIR variability data set of Sgr A* to date: eight 24 hr epochs of continuous monitoring of Sgr A* at 4.5 m with the IRAC instrument on the , 93 epochs of 2.
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