Millihertz oscillations near the innermost orbit of a supermassive black hole
Ingram, Adam; Fabian, Andrew C.; Remillard, Ronald A.; Cenko, S. Bradley; Ricci, Claudio; Laha, Sibasish; Trakhtenbrot, Benny; García, Javier A.; Meyer, Eileen T.; Miniutti, Giovanni; Kara, Erin; Alston, William N.; Wang, Jingyi; Giustini, Margherita; Loewenstein, Michael; Pinto, Ciro; Masterson, Megan; Burdge, Kevin; Arcavi, Iair; Kosec, Peter; Arcodia, Riccardo; Chakraborty, Joheen; Panagiotou, Christos; Shuvo, Onic I.; Sadaula, Dev R.
United States, United Kingdom, Chile, China, Israel, Spain, Italy
Abstract
Recent discoveries from time-domain surveys are defying our expectations for how matter accretes onto supermassive black holes (SMBHs). The increased rate of short-timescale, repetitive events around SMBHs, including the recently discovered quasi-periodic eruptions1, 2, 3, 4–5, are garnering further interest in stellar-mass companions around SMBHs and the progenitors to millihertz-frequency gravitational-wave events. Here we report the discovery of a highly significant millihertz quasi-periodic oscillation (QPO) in an actively accreting SMBH, 1ES 1927+654, which underwent a major optical, ultraviolet and X-ray outburst beginning in 20186,7. The QPO was detected in 2022 with a roughly 18-minute period, corresponding to coherent motion on a scale of less than 10 gravitational radii, much closer to the SMBH than typical quasi-periodic eruptions. The period decreased to 7.1 minutes over 2 years with a decelerating period evolution (