Optical and X-ray emission from stable millisecond magnetars formed from the merger of binary neutron stars

摘要: The coalescence of binary neutron stars (NSs) may in some cases produce a stable massive NS remnant rather than black hole. Due to the substantial angular momentum from binary, such is born rapidly rotating and likely acquires strong magnetic field (a ‘millisecond magnetar’). Magnetic spin-down deposits large fraction rotational energy magnetar behind small quantity mass ejected during merger. If outflow indeed trapped ejecta (instead placing most its into collimated jet), this has potential for creating bright transient that could be useful determining whether an or hole was formed We investigate expected signature event, including first time important impact e^± pairs injected by millisecond surrounding nebula. These cool via synchrotron inverse Compton emission, producing pair cascade hard X-ray spectrum. A these X-rays are absorbed walls re-emitted as thermal radiation, leading optical/UV peaking at luminosity ∼10^(43)–10^(44) erg s^(−1) on time-scale several hours days. This dimmer predicted simpler analytic models because optical depth across nebula suppresses efficiency with which thermalized. Nevertheless, emission more two orders magnitude brighter radioactively powered ‘kilonova’. In cases, nebular sufficiently luminous re-ionize ejecta, case non-thermal escape unattenuated similar peak radiation. discuss implications our results temporally extended observed follow short gamma-ray bursts (GRBs), kilonova candidates GRB 080503 130603B.