56 research outputs found
Quark-nova explosion inside a collapsar: application to Gamma Ray Bursts
If a quark-nova occurs inside a collapsar, the interaction between the
quark-nova ejecta (relativistic iron-rich chunks) and the collapsar envelope,
leads to features indicative of those observed in Gamma Ray Bursts. The
quark-nova ejecta collides with the stellar envelope creating an outward moving
cap
(Gamma ~ 1-10) above the polar funnel. Prompt gamma-ray burst emission from
internal shocks in relativistic jets (following accretion onto the quark star)
become visible after the cap becomes optically thin. Model features include:
(i) precursor activity (optical, X-ray, gamma-ray), (ii) prompt gamma-ray
emission, and (iii) afterglow emission. We discuss SN-less long duration GRBs,
short hard GRBs (including association and non-association with star forming
regions), dark GRBs, the energetic X-ray flares detected in Swift GRBs, and the
near-simultaneous optical and gamma-ray prompt emission observed in GRBs in the
context of our model.Comment: 10 journal pages and 5 figures (updated references and extended
discussions; accepted for publication in Advances in Astronomy
SGR 0418+5729 as an evolved Quark-Nova compact remnant
Soft gamma repeaters and anomalous X-ray pulsars are believed to be
magnetars, i.e. neutron stars powered by extreme magnetic fields,
B~10^(14)-10^(15) Gauss. The recent discovery of a soft gamma repeater with low
magnetic field (< 7.5x10^(12) Gauss), SGR 0418+5729, which shows bursts similar
to those of SGRs, implies that a high surface dipolar magnetic field might not
be necessary for magnetar-like activity. We show that the quiescent and
bursting properties of SGR 0418+5729 find natural explanations in the context
of low-magnetic field Quark-Nova (detonative transition from a neutron star to
a quark star) remnants, i.e. an old quark star surrounded by degenerate
(iron-rich) Keplerian ring/debris ejected during the Quark-Nova explosion. We
find that a 16 Myr old quark star surrounded by a ~ 10^(-10)xM_sun ring,
extending in radius from ~ 30 km to 60 km, reproduces many observed properties
of SGR 0418+5729. The SGR-like burst is caused by magnetic penetration of the
inner part of the ring and subsequent accretion. Radiation feedback results in
months-long accretion from the ring's non-degenerate atmosphere which matches
well the observed decay phase. We make specific predictions (such as an
accretion glitch of Delta P/P ~ - 2x10^(-11) during burst and a sub-keV proton
cyclotron line from the ring) that can be tested by sensitive observations.Comment: Version to appear on MNRAS (7 journals pages. 3 figures). Extended
discussion and conclusions. Elaboration on predictions of the mode
SGRs and AXPs proposed as ancestors of the Magnificent seven
The recently suggested correlation between the surface temperature and the
magnetic field in isolated neutron stars does not seem to work well for SGRs,
AXPs and X-ray dim isolated neutron stars (XDINs; specifically the Magnificent
Seven or M7). Instead by appealing to a Color-Flavor Locked Quark Star (CFLQS)
we find a more natural explanation. In this picture, the heating is provided by
magnetic flux expulsion from a crust-less superconducting quark star. Combined
with our previous studies concerning the possibility of SGRs, AXPs, and XDINs
as CFLQSs, this provides another piece of evidence that these objects are all
related. Specifically, we propose that XDINs are the descendants of SGRs and
AXPs.Comment: submitted to A&A letters to the edito
Gamma Ray Burst engine activity within the quark nova scenario: Prompt emission, X-ray Plateau, and sharp drop-off
We present a three-stage model for a long GRB inner engine to explain the
prompt gamma ray emission, and interpret recent Swift satellite observations of
early X-ray afterglow plateaus followed by a sharp drop off or a shallow power
law decay. The three stages involves a neutron star phase, a quark star (QS)
and a black hole phase as described in Staff et al. (2007). We find that the QS
stage allows for more energy to be extracted from neutron star to QS conversion
as well as from ensuing accretion onto the QS. The QS accretion phase naturally
extends the engine activity and can account for both the prompt emission and
irregular early X-ray afterglow activity. Following the accretion phase, the QS
can spin-down by emission of a baryon-free outflow. The magnetar-like magnetic
field strengths resulting from the NS to QS transition provide enough spin-down
energy, for the correct amount of time, to account for the plateau in the X-ray
afterglow. In our model, a sharp drop-off following the plateau occurs when the
QS collapses to a BH during the spin-down, thus shutting-off the secondary
outflow. We applied our model to GRB 070110 and GRB 060607A and found that we
can consistently account for the energetics and duration during the prompt and
plateau phases.Comment: 4 pages, submitted to ApJ
Numerical Simulation of the Hydrodynamical Combustion to Strange Quark Matter
We present results from a numerical solution to the burning of neutron matter
inside a cold neutron star into stable (u,d,s) quark matter. Our method solves
hydrodynamical flow equations in 1D with neutrino emission from weak
equilibrating reactions, and strange quark diffusion across the burning front.
We also include entropy change due to heat released in forming the stable quark
phase. Our numerical results suggest burning front laminar speeds of 0.002-0.04
times the speed of light, much faster than previous estimates derived using
only a reactive-diffusive description. Analytic solutions to hydrodynamical
jump conditions with a temperature dependent equation of state agree very well
with our numerical findings for fluid velocities. The most important effect of
neutrino cooling is that the conversion front stalls at lower density (below
approximately 2 times saturation density). In a 2-dimensional setting, such
rapid speeds and neutrino cooling may allow for a flame wrinkle instability to
develop, possibly leading to detonation.Comment: 5 pages, 3 figures (animations online at
http://www.capca.ucalgary.ca/~bniebergal/webPHP/research.php
A three stage model for the inner engine of GRBs: Prompt emission and early afterglow
We describe a model within the ``Quark-nova'' scenario to interpret the
recent observations of early X-ray afterglows of long Gamma-Ray Bursts (GRB)
with the Swift satellite. This is a three-stage model within the context of a
core-collapse supernova. STAGE 1 is an accreting (proto-) neutron star leading
to a possible delay between the core collapse and the GRB. STAGE 2 is accretion
onto a quark-star, launching an ultrarelativistic jet generating the prompt
GRB. This jet also creates the afterglow as the jet interacts with the
surrounding medium creating an external shock. Slower shells ejected from the
quark star (during accretion), can re-energize the external shock leading to a
flatter segment in the X-ray afterglow. STAGE 3, which occurs only if the
quark-star collapses to form a black-hole, consists of an accreting black-hole.
The jet launched in this accretion process interacts with the preceding quark
star jet, and could generate the flaring activity frequently seen in early
X-ray afterglows. Alternatively, a STAGE 2b can occur in our model if the quark
star does not collapse to a black hole. The quark star in this case can then
spin down due to magnetic braking, and the spin down energy may lead to
flattening in the X-ray afterglow as well. This model seems to account for both
the energies and the timescales of GRBs, in addition to the newly discovered
early X-ray afterglow features.Comment: 4 pages, to appear in the proceedings of the HEPRO conference,
September 24-28, 2007, Dublin, Irelan
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