Browsing by Author "Baker, John G."
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Item Electromagnetic emission from a binary black hole merger remnant in plasma: Field alignment and plasma temperature(American Physical Society, 2021-03-26) Kelly, Bernard; Etienne, Zachariah B.; Golomb, Jacob; Schnittman, Jeremy D.; Baker, John G.; Noble, Scott C.; Ryan, Geoffrey; Center for Space Sciences and TechnologyComparable-mass black-hole mergers generically result in moderate to highly spinning holes, whose spacetime curvature will significantly affect nearby matter in observable ways. We investigate how the moderate spin of a postmerger Kerr black hole immersed in a plasma with initially uniform density and uniform magnetic field affects potentially observable accretion rates and energy fluxes. Varying the initial specific internal energy of the plasma over two decades, we find very little change in steady-state mass accretion rate or Poynting luminosity, except at the lowest internal energies, where fluxes do not exhibit steady-state behavior during the simulation timescale. Fixing the internal energy and varying the initial fixed magnetic-field amplitude and orientation, we find that the steady-state Poynting luminosity depends strongly on the initial field angle with respect to the black hole spin axis, while the matter accretion rate is more stable until the field angle exceeds ∼45°. The protojet formed along the black hole spin axis conforms to a thin, elongated cylinder near the hole, while aligning with the asymptotic magnetic field at large distances.Item Prompt Electromagnetic Transients from Binary Black Hole Mergers(American Physical Society, 2017-12-12) Kelly, Bernard; Baker, John G.; Etienne, Zachariah B.; Giacomazzo, Bruno; Schnittman, Jeremy D.; Center for Space Sciences and TechnologyBinary black hole (BBH) mergers provide a prime source for current and future interferometric gravitational wave observatories. Massive BBH mergers may often take place in plasma-rich environments, leading to the exciting possibility of a concurrent electromagnetic (EM) signal observable by traditional astronomical facilities. However, many critical questions about the generation of such counterparts remain unanswered. We explore mechanisms that may drive EM counterparts with magnetohydrodynamic simulations treating a range of scenarios involving equal-mass black-hole binaries immersed in an initially homogeneous fluid with uniform, orbitally aligned magnetic fields. We find that the time development of Poynting luminosity, which may drive jetlike emissions, is relatively insensitive to aspects of the initial configuration. In particular, over a significant range of initial values, the central magnetic field strength is effectively regulated by the gas flow to yield a Poynting luminosity of 10⁴⁵ − 10⁴⁶ρ₋₁₃M₈² erg s⁻¹, with BBH mass scaled to M₈ ≡ M/(10⁸ M⊙) and ambient density ρ₋₁₃ ≡ ρ/(10⁻¹³ g cm⁻³). We also calculate the direct plasma synchrotron emissions processed through geodesic ray-tracing. Despite lensing effects and dynamics, we find the observed synchrotron flux varies little leading up to merger.