http://arxiv.org/abs/1702.04339
Long duration gamma-ray bursts (GRBs) mark the birth of a compact object, a neutron star or black hole. At low-redshift ($z<0.2$) these events are extremely rare and most are poorly known. Four nearby GRBs have been associated with Type Ic supernovae (SNe Ic), . GRB/SNe lack hydrogen and helium, and are classified as SNe Ic, but have extremely broad features, which indicate the presence of material at very high velocities ($>0.3c$). They have a kinetic energy ($E_{k}$) of $\sim10^{52}$erg, and are thought to be the explosion of bare carbon-oxygen cores of stars with initial mass 35-50M$_\odot$. Here we report observations of the nearby GRB 161219B ($z=0.1475$) and the associated SN 2016jca. We obtained a high-cadence time-series of spectra and photometry starting 2 days after explosion. The GRB afterglow had a late monochromatic break 12 days after outburst which indicates that the relativistic material was ejected in an outflow with a large opening angle. We first identified the SN 5 days after the GRB.
Such an early detection gives us the opportunity to explore the outermost layers of the ejecta.
We find the outer most ejecta are dominated by heavy elements, while lighter elements are present in high abundance at low velocities.
Geometrically this suggests that we are view a high velocity nuclearly processed outflow down its axis.
This and the wide opening angle suggests a highly magnetized millisecond pulsar may power the explosion.
C. Ashall, E. Pian, P. Mazzali, et. al.
Wed, 15 Feb 17
36/47
Comments: submitted to nature astronomy
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