156 research outputs found
Quark-nova remnants IV: Application to radio emitting AXP transients
(Abridged) XTE J1810-197 and 1E 1547.0-5408 are two transient AXPs exhibiting
radio emission with unusual properties. In addition, their spin down rates
during outburst show opposite trends, which so far has no explanation. Here, we
extend our quark-nova model for AXPs to include transient AXPs, in which the
outbursts are caused by transient accretion events from a Keplerian (iron-rich)
degenerate ring. For a ring with inner and outer radii of 23.5 km and 26.5 km,
respectively, our model gives a good fit to the observed X-ray outburst from
XTE J1810-197 and the behavior of temperature, luminosity, and area of the two
X-ray blackbodies with time. The two blackbodies in our model are related to a
heat front (i.e. Bohm diffusion front) propagating along the ring's surface and
an accretion hot spot on the quark star surface. Radio pulsations in our model
are caused by dissipation at the light cylinder of magnetic bubbles, produced
near the ring during the X-ray outburst. The delay between X-ray peak emission
and radio emission in our model is related to the propagation time of these
bubbles to the light cylinder. We predict a ~1 year and ~1 month delay for XTE
J1810-197 and 1E 1547.0-5408, respectively. The observed flat spectrum, erratic
pulse profile, and the pulse duration are all explained in our model as a
result of X-point reconnection events induced by the dissipation of the bubbles
at the light cylinder. The spin down rate of the central quark star can either
increase or decrease depending on how the radial drift velocity of the magnetic
islands changes with distance from the central star. We suggest an evolutionary
connection between transient AXPs and typical AXPs in our model.Comment: 16 journal pages, 4 figures and 1 table [Version accepted for
publication in A&A
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
Quark nova imprint in the extreme supernova explosion SN 2006gy
The extremely luminous supernova 2006gy (SN 2006gy) is among the most
energetic ever observed. The peak brightness was 100 times that of a typical
supernova and it spent an unheard of 250 days at magnitude -19 or brighter.
Efforts to describe SN 2006gy have pushed the boundaries of current supernova
theory. In this work we aspire to simultaneously reproduce the photometric and
spectroscopic observations of SN 2006gy using a quark nova model. This analysis
considers the supernova explosion of a massive star followed days later by the
quark nova detonation of a neutron star. We lay out a detailed model of the
interaction between the supernova envelope and the quark nova ejecta paying
special attention to a mixing region which forms at the inner edge of the
supernova envelope. This model is then fit to photometric and spectroscopic
observations of SN 2006gy. This QN model naturally describes several features
of SN 2006gy including the late stage light curve plateau, the broad H{\alpha}
line and the peculiar blue H{\alpha} absorption. We find that a progenitor mass
between 20Msun and 40Msun provides ample energy to power SN 2006gy in the
context of a QN.Comment: 15 pages, 9 figure
Planets orbiting Quark Nova compact remnants
We explore planet formation in the Quark Nova scenario. If a millisecond pulsar explodes as a Quark Nova, a protoplanetary disk can be formed out of the metal rich fall-back material. The propeller mechanism transfers angular momentum from the born quark star to the disk that will go through viscous evolution with later plausible grain condensation and planet formation. As a result, earth-size planets on circular orbits may form within short radii from the central quark star. The planets in the PSR1257+12 system can be explained by our model if the Quark Nova compact remnant is born with a period of ms following the explosion. We suggest that a good portion of the Quark Nova remnants may harbour planetary systems
r-Java 2.0: the nuclear physics
[Aims:] We present r-Java 2.0, a nucleosynthesis code for open use that
performs r-process calculations as well as a suite of other analysis tools.
[Methods:] Equipped with a straightforward graphical user interface, r-Java 2.0
is capable of; simulating nuclear statistical equilibrium (NSE), calculating
r-process abundances for a wide range of input parameters and astrophysical
environments, computing the mass fragmentation from neutron-induced fission as
well as the study of individual nucleosynthesis processes. [Results:] In this
paper we discuss enhancements made to this version of r-Java, paramount of
which is the ability to solve the full reaction network. The sophisticated
fission methodology incorporated into r-Java 2.0 which includes three fission
channels (beta-delayed, neutron-induced and spontaneous fission) as well as
computation of the mass fragmentation is compared to the upper limit on mass
fission approximation. The effects of including beta-delayed neutron emission
on r-process yield is studied. The role of coulomb interactions in NSE
abundances is shown to be significant, supporting previous findings. A
comparative analysis was undertaken during the development of r-Java 2.0
whereby we reproduced the results found in literature from three other
r-process codes. This code is capable of simulating the physical environment
of; the high-entropy wind around a proto-neutron star, the ejecta from a
neutron star merger or the relativistic ejecta from a quark nova. As well the
users of r-Java 2.0 are given the freedom to define a custom environment. This
software provides an even platform for comparison of different proposed
r-process sites and is available for download from the website of the
Quark-Nova Project: http://quarknova.ucalgary.ca/Comment: 26 pages, 18 figures, 1 tabl
3-d resistive MHD simulations of magnetic reconnection and the tearing mode instability in current sheets
Magnetic reconnection plays a critical role in many astrophysical processes
where high energy emission is observed, e.g. particle acceleration,
relativistic accretion powered outflows, pulsar winds and probably in
dissipation of Poynting flux in GRBs. The magnetic field acts as a reservoir of
energy and can dissipate its energy to thermal and kinetic energy via the
tearing mode instability. We have performed 3d nonlinear MHD simulations of the
tearing mode instability in a current sheet. Results from a temporal stability
analysis in both the linear regime and weakly nonlinear (Rutherford) regime are
compared to the numerical simulations. We observe magnetic island formation,
island merging and oscillation once the instability has saturated. The growth
in the linear regime is exponential in agreement with linear theory. In the
second, Rutherford regime the island width grows linearly with time. We find
that thermal energy produced in the current sheet strongly dominates the
kinetic energy. Finally preliminary analysis indicates a P(k) 4.8 power law for
the power spectral density which suggests that the tearing mode vortices play a
role in setting up an energy cascade.Comment: 4 pages, 8 figures, accepted for publication in the International
Journal of Modern Physics D, proceedings of HEPRO meeting, held in Dublin, in
September 200
Fireballs from Quark Stars in the CFL Phase: Application to Gamma Ray Bursters
Recent studies of photon-generation mechanisms in the color-superconducting
Color-Flavor Locked (CFL) phase of dense quark matter have found gamma-ray
emissivities in excess of ~ 10^{50} erg cm^{-3} s^{-1} for temperatures in the
10-30 MeV range. We suggest that this property can trigger gamma-ray bursts
(GRBs) and associated fireballs at the surface of hypothetical hot (newly born)
quark stars with an energy release of up to 10^{48}-10^{50} erg within a
fraction of a millisecond. If surrounded by an accretion disk following its
formation, the star's bursting activity can last from tens of milliseconds to
hundreds of seconds releasing up to 10^{52} erg in total energy. We discuss
typical features of observed GRBs within our model and explain how quark stars
in the CFL phase might constitute natural candidates for corresponding inner
engines.Comment: 8 journal pages, 6 figures. Accepted for publication in the
Astrophysical Journa
Fall-back crust around a quark-nova compact remnant I: The degenerate shell case with applications to SGRs, AXPs and XDINs
We explore the formation and evolution of debris ejected around quark stars
in the Quark Nova scenario, and the application to Soft Gamma-ray Repeaters
(SGRs) and Anomolous X-ray Pulsars (AXPs). If an isolated neutron star explodes
as a Quark Nova, an Iron-rich shell of degenerate matter forms out of the
fall-back (crust) material. Our model can account for many of the observed
features of SGRs and AXPs such as: (i) the two types of bursts (giant and
regular); (ii) the spin-up and spin-down episodes during and following the
bursts with associated persistant increases in ; (iii) the energetics
of the boxing day burst, SGR180620; (iv) the presence of an Iron line as
observed in SGR190014; (v) the correlation between the far-Infrared and the
X-ray fluxes during the bursting episode and the quiescent phase; (vi) the hard
X-ray component observed in SGRs during the giant bursts, and (vii) the
discrepancy between the ages of SGRs/AXPs and their supernova remnants. We also
find a natural evolutionary relationship between SGRs and AXPs in our model
which predicts that only the youngest SGRs/AXPs are most likely to exhibit
strong bursting. Many features of X-ray Dim Isolated Neutron stars (XDINs) are
also accounted for in our model such as, (i) the two-component blackbody
spectra; (ii) the absorption lines around 300 eV; and (iii) the excess optical
emission.Comment: submitted to Ap
Quark Stars as inner engines for Gamma Ray Bursts?
A model for Gamma ray bursts inner engine based on quark stars (speculated to
exist in nature) is presented. We describe how and why these objects might
constitute new candidates for GRB inner engines. At the heart of the model is
the onset of exotic phases of quark matter at the surface of such stars, in
particular the 2-flavor color superconductivity. A novel feature of such a
phase is the generation of particles which are unstable to photon decay
providing a natural mechanism for a fireball generation; an approach which is
fundamentally different from models where the fireball is generated during
collapse or conversion of neutron star to quark star processes. The model is
capable of reproducing crucial features of Gamma ray bursts, such as the
episodic activity of the engine (multiple and random shell emission) and the
two distinct categories of the bursts (two regimes are isolated in the model
with \sim 2 s and \sim 81 s burst total duration).Comment: 8 pages, 3 figures, new and more appropriate title. Major changes in
the text (aspects of the models discussed in more details), better quality
Figure 1 and Figure 2 and added Figure 3, version to appear in
Astronomy&Astrophysic
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