2021ApJ...906...48G

We use Chandra X-ray observations to look for evidence of a recoiling black hole from the brightest cluster galaxy in Abell 2261 (A2261-BCG). A2261-BCG is a strong candidate for a recoiling black hole because of its large, flat stellar core, revealed by Hubble Space Telescope imaging observations. We took 100 ks observations with Chandra and combined it with 35 ks of archival observations to look for low-level accretion onto a black hole of expected mass M∼10¹⁰M_☉ that could possibly be located in one of four off-center stellar knots near the galaxy's center or else in the optical center of the galaxy or in the location of radio emission. We found no X-ray emission arising from a point source in excess of the cluster gas and can place limits on the accretion of any black hole in the central region to a 2-7 keV flux below 4.3×10^–16 erg s^–1 cm^–2, corresponding to a bolometric Eddington fraction of about 10^–6. Thus there is either no 10¹⁰ M_☉ black hole in the core of A2261-BCG, or it is accreting at a low level. We also discuss the morphology of the X-ray emitting gas in the cluster and how its asymmetry is consistent with a large dynamic event.