Magnetar as Central Engine of Gamma-Ray Bursts: Central Engine-Jet Connection, Wind-Jet Energy Partition, and Origin of Some Ultra-Long Bursts. (arXiv:1904.04984v1 [astro-ph.HE])

Magnetar as Central Engine of Gamma-Ray Bursts: Central Engine-Jet Connection, Wind-Jet Energy Partition, and Origin of Some Ultra-Long Bursts. (arXiv:1904.04984v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Zou_L/0/1/0/all/0/1">Le Zou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhou_Z/0/1/0/all/0/1">Zi-Min Zhou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Xie_L/0/1/0/all/0/1">Lang Xie</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_L/0/1/0/all/0/1">Lu-Lu Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+LV_H/0/1/0/all/0/1">Hou-Jun LV</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhong_S/0/1/0/all/0/1">Shu-Qing Zhong</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_Z/0/1/0/all/0/1">Zhen-Jie Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liang_E/0/1/0/all/0/1">En-Wei Liang</a>

Gamma-ray burst (GRB) central engines and jet production mechanisms are still
open questions. Assuming that the shallow decay segments of canonical X-ray
afterglow lightcurves of {em Swift} GRBs are attributed to the magnetic dipole
(MD) radiations of newly-born magnetars, we derive the parameters of the
magnetars and explore their possible relations to jet and MD wind emission. We
show that the magnetar initial spin period ($P_0$) are tightly correlated with
the jet energy ($E_{rm jet}$), which is almost proportional to the wind energy
($E_{rm wind}$). Our least square fits yield $P_0propto E^{-0.36pm
0.03}_{rm jet}$ and $E_{rm wind}propto E^{0.91pm 0.07}_{rm jet}$. These
relations may imply that a magnetar with faster rotating speed can power a more
energetic GRB, and energy partition between the jet and wind may be
quasi-universal. Although the $P_0-E_{rm jet}$ relation is driven by a few
sub-energetic GRBs in our sample, our Monte Carlo simulation analysis shows
that sample selection biases from instrumental flux limits and contaminations
of the bright jet afterglows cannot make this correlation. Within this jet-wind
paradigm, we propose that GRB 101225A-like ultra-long GRBs, whose prompt
gamma-ray/X-ray lightcurves are featured as a long-lasting plateau with a sharp
drop, may be the orphan MD wind emission being due to misalignment of their jet
axis to the light of sight. Brief discussion on the orphan MD wind emission and
its association with the gravitational wave radiation of newly-born magnetars
is presented.

Gamma-ray burst (GRB) central engines and jet production mechanisms are still
open questions. Assuming that the shallow decay segments of canonical X-ray
afterglow lightcurves of {em Swift} GRBs are attributed to the magnetic dipole
(MD) radiations of newly-born magnetars, we derive the parameters of the
magnetars and explore their possible relations to jet and MD wind emission. We
show that the magnetar initial spin period ($P_0$) are tightly correlated with
the jet energy ($E_{rm jet}$), which is almost proportional to the wind energy
($E_{rm wind}$). Our least square fits yield $P_0propto E^{-0.36pm
0.03}_{rm jet}$ and $E_{rm wind}propto E^{0.91pm 0.07}_{rm jet}$. These
relations may imply that a magnetar with faster rotating speed can power a more
energetic GRB, and energy partition between the jet and wind may be
quasi-universal. Although the $P_0-E_{rm jet}$ relation is driven by a few
sub-energetic GRBs in our sample, our Monte Carlo simulation analysis shows
that sample selection biases from instrumental flux limits and contaminations
of the bright jet afterglows cannot make this correlation. Within this jet-wind
paradigm, we propose that GRB 101225A-like ultra-long GRBs, whose prompt
gamma-ray/X-ray lightcurves are featured as a long-lasting plateau with a sharp
drop, may be the orphan MD wind emission being due to misalignment of their jet
axis to the light of sight. Brief discussion on the orphan MD wind emission and
its association with the gravitational wave radiation of newly-born magnetars
is presented.

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