X-Ray Imaging of the Jet From the Supermassive Black Hole M87

Abstract

The elliptical galaxy M87 has long been a target of interest for the study of black hole physics and relativistic jets across the electromagnetic spectrum. In April 2017, the Event Horizon Telescope (EHT) undertook a campaign to study nearby supermassive black holes, including M87, at many wavelengths. As part of this campaign, we observed M87 with the Chandra X-ray Observatory to study both the supermassive black hole and relativistic jet at high energy. We created images of M87 with spectra of the inner jet, and a deconvolved image to explore the relative intensity of the core and the first knot, HST-1. The deconvolved image suggests that HST-1 was significantly fainter than the core. We found no evidence of strong variability in the X-ray brightness during our observation, but we discovered a photon index < 2.25, the previously recorded value. M87 was also fainter than recent observations (L_x ≈ 1.25 × 10⁴¹ erg s^-1, and we found hints of extra hydrogen in the core region. Given HST-1's history of variations and recent trends indicating a fading HST-1, we suggest that the lower photon index may be due to a fainter HST-1 knot.