Bright "Merger-nova" Emission Powered by Magnetic wind from a New-Born Black Hole

Abstract

Mergers of neutron star-neutron star (NS-NS) or neutron star-black hole (NS-BH) binaries are candidate sources of gravitational waves (GWs). At least a fraction of the merger remnant should be a stellar mass BH with a sub-relativistic ejecta. A collimated jet is launched via Blandford-Znajek mechanism from the central BH to trigger a short gamma-ray burst (SGRB). At the same time, a near-isotropic wind can be driven by the Blandford-Payne mechanism (BP). In previous work, additional energy injection to the ejecta from the BP mechanism was ignored, and radioactive decay has long been thought as the main source of energy for "kilonova" in the BH scenario. In this letter, we propose that the wind driven by BP mechanism from the new-born BH-disk can heat up and push the ejecta during the prompt emission phase or even at late time when there is mass fall-back. Such a BP-powered merger-nova could be bright at optical band even for a low-luminosity SGRB. The detection of a GW event with a merger product of BH, and accompanied by a bright merger-nova, would be a robust test of our model.

6 pages, 4 figures. Accepted for publication in ApJL

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• The Gravitational-Wave Physics II: Progress
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• Population Properties of Gravitational-Wave Neutron Star--Black Hole Mergers
• A Channel to Form Fast-spinning Black Hole--Neutron Star Binary Mergers as Multi-messenger Sources
• Eighteen Years of Kilonova Discoveries with Swift
• Constraining Properties of GRB Central Engines with X-ray flares
• GRB 111209A/SN 2011kl: Collapse of a supramassive magnetar with r-mode oscillation and fall-back accretion onto a newborn black hole
• The mass, spin and rotational energy of the remnant black holes from compact binary mergers