10/29 12:30 Dr. Dhruv Desai (IoP, Academia Sinica) Millisecond proto-magnetars as gamma-ray burst central engines (R521, 5F, General Building II, Nat'l Tsing Hua Univ.)
******** CTCD/NTHU HEP Seminar ********
Speaker : Dr. Dhruv Desai (IoP, Academia Sinica)
Title : Millisecond proto-magnetars as gamma-ray burst central engines
Time ：12:30-13:30, Thursday, 2026/10/29
Place ：R521, 5F, General Building II, Nat'l Tsing Hua Univ.
Host ： Prof. Kingman Cheung (NTHU) & Prof. Norihiro Iizuka (NTHU)
Abstract:
Rapidly rotating, strongly magnetized neutron stars (``millisecond
proto-magnetars'') formed in stellar core-collapse, neutron star
mergers, and white dwarf accretion-induced collapse have long been
proposed as central engines of gamma-ray bursts (GRB) and accompanying
supernovae/kilonovae. However, during the first few seconds after
birth, neutrino heating drives baryon-rich winds from the neutron star
surface, potentially limiting the magnetization and achievable Lorentz
factors of the outflow and casting doubt on whether proto-magnetars
can launch ultra-relativistic jets at early times, as needed to power
short-duration GRB. I present the first three-dimensional
general-relativistic magnetohydrodynamic simulations of
neutrino-heated proto-magnetar winds. While the global wind properties
broadly agree with previous analytic estimates calibrated to
one-dimensional models, our simulations reveal essential
multidimensional effects. For rapidly rotating models with spin
periods P ~ 1 ms, centrifugal forces strongly enhance mass loss near
the rotational equator, producing a dense, sub-relativistic outflow (v
~ 0.1 c). This equatorial wind naturally confines and collimates less
baryon-loaded outflows emerging from higher latitudes, leading to the
formation of a structured bipolar jet with a peak magnetization along
the pole up to ~30-100, sufficient to reach bulk Lorentz factors ~ 100
on larger scales. The resulting angular stratification of the outflow
energy into ultra-relativistic polar and sub-relativistic equatorial
components is broadly consistent with the observed partition between
beaming-corrected GRB energies and supernova/kilonova ejecta. Our
results demonstrate that millisecond proto-magnetars can launch
relativistic jets within seconds of formation and highlight their
potential role in powering the diverse electromagnetic counterparts of
compact-object explosions.
Speaker : Dr. Dhruv Desai (IoP, Academia Sinica)
Title : Millisecond proto-magnetars as gamma-ray burst central engines
Time ：12:30-13:30, Thursday, 2026/10/29
Place ：R521, 5F, General Building II, Nat'l Tsing Hua Univ.
Host ： Prof. Kingman Cheung (NTHU) & Prof. Norihiro Iizuka (NTHU)
Abstract:
Rapidly rotating, strongly magnetized neutron stars (``millisecond
proto-magnetars'') formed in stellar core-collapse, neutron star
mergers, and white dwarf accretion-induced collapse have long been
proposed as central engines of gamma-ray bursts (GRB) and accompanying
supernovae/kilonovae. However, during the first few seconds after
birth, neutrino heating drives baryon-rich winds from the neutron star
surface, potentially limiting the magnetization and achievable Lorentz
factors of the outflow and casting doubt on whether proto-magnetars
can launch ultra-relativistic jets at early times, as needed to power
short-duration GRB. I present the first three-dimensional
general-relativistic magnetohydrodynamic simulations of
neutrino-heated proto-magnetar winds. While the global wind properties
broadly agree with previous analytic estimates calibrated to
one-dimensional models, our simulations reveal essential
multidimensional effects. For rapidly rotating models with spin
periods P ~ 1 ms, centrifugal forces strongly enhance mass loss near
the rotational equator, producing a dense, sub-relativistic outflow (v
~ 0.1 c). This equatorial wind naturally confines and collimates less
baryon-loaded outflows emerging from higher latitudes, leading to the
formation of a structured bipolar jet with a peak magnetization along
the pole up to ~30-100, sufficient to reach bulk Lorentz factors ~ 100
on larger scales. The resulting angular stratification of the outflow
energy into ultra-relativistic polar and sub-relativistic equatorial
components is broadly consistent with the observed partition between
beaming-corrected GRB energies and supernova/kilonova ejecta. Our
results demonstrate that millisecond proto-magnetars can launch
relativistic jets within seconds of formation and highlight their
potential role in powering the diverse electromagnetic counterparts of
compact-object explosions.