146 research outputs found
Cooling of Hybrid Neutron Stars and Hypothetical Self-bound Objects with Superconducting Quark Cores
We study the consequences of superconducting quark cores (with
color-flavor-locked phase as representative example) for evolution of
temperature profiles and the cooling curves in quark-hadron hybrid stars and in
hypothetical self-bounded objects having no a hadron shell (quark core neutron
stars). The quark gaps are varied from 0 to MeV. For hybrid
stars we find time scales of , and years for the
formation of a quasistationary temperature distribution in the cases , 0.1 MeV and \gsim 1 MeV, respectively. These time scales are governed by
the heat transport within quark cores for large diquark gaps (\Delta \gsim 1
MeV) and within the hadron shell for small diquark gaps (\Delta \lsim 0.1
MeV). For quark core neutron stars we find a time scale years for
the formation of a quasistationary temperature distribution in the case \Delta
\gsim 10 MeV and a very short one for \Delta \lsim 1 MeV. If hot young
compact objects will be observed they can be interpreted as manifestation of
large gap color superconductivity. Depending on the size of the pairing gaps,
the compact star takes different paths in the vs. diagram
where is the surface temperature. Compared to the corresponding hadronic
model which well fits existing data the model for the hybrid neutron star (with
a large diquark gap) shows too fast cooling. The same conclusion can be drawn
for the corresponding self-bound objects.Comment: 8 pages, 4 figures, uses aa-package (included), accepted for A&
On the Cooling of the Neutron Star in Cassiopeia A
We demonstrate that the high-quality cooling data observed for the young
neutron star in the supernova remnant Cassiopeia A over the past 10 years--as
well as all other reliably known temperature data of neutron stars--can be
comfortably explained within the "nuclear medium cooling" scenario. The cooling
rates of this scenario account for medium-modified one-pion exchange in dense
matter and polarization effects in the pair-breaking formations of superfluid
neutrons and protons. Crucial for the successful description of the observed
data is a substantial reduction of the thermal conductivity, resulting from a
suppression of both the electron and nucleon contributions to it by medium
effects. We also find that possibly in as little as about ten years of
continued observation, the data may tell whether or not fast cooling processes
are active in this neutron star.Comment: 4 pages, 3 figure
Thermal Evolution of Neutron Stars in 2 Dimensions
There are many factors that contribute to the breaking of the spherical
symmetry of a neutron star. Most notably is rotation, magnetic fields, and/or
accretion of matter from companion stars. All these phenomena influence the
macroscopic structures of neutron stars, but also impact their microscopic
compositions. The purpose of this paper is to investigate the cooling of
rotationally deformed, two-dimensional (2D) neutron stars in the framework of
general relativity theory, with the ultimate goal of better understand the
impact of 2D effects on the thermal evolution of such objects. The equations
that govern the thermal evolution of rotating neutron stars are presented in
this paper. The cooling of neutron stars with different frequencies is computed
self-consistently by combining a fully general relativistic 2D rotation code
with a general relativistic 2D cooling code. We show that rotation can
significantly influence the thermal evolution of rotating neutron stars. Among
the major new aspects are the appearances of hot spots on the poles, and an
increase of the thermal coupling times between the core and the crust of
rotating neutron stars. We show that this increase is independent of the
microscopic properties of the stellar core, but depends only on the frequency
of the star.Comment: 8 pages, 6 figures, revised versio
Differences in the Cooling Behavior of Strange Quark Matter Stars and Neutron Stars
The general statement that hypothetical strange (quark matter) stars cool
more rapidly than neutron stars is investigated in greater detail. It is found
that the direct Urca process could be forbidden not only in neutron stars but
also in strange stars. In this case, strange stars are slowly cooling, and
their surface temperatures are more or less indistinguishable from those of
slowly cooling neutron stars. Furthermore the case of enhanced cooling is
reinvestigated. It shows that strange stars cool significantly more rapidly
than neutron stars within the first years after birth. This feature
could become particularly interesting if continued observation of SN 1987A
would reveal the temperature of the possibly existing pulsar at its center.Comment: 9 pages, LaTeX (aas-style file), 2 ps-figures. To be published in ApJ
Letter
Timing evolution of accreting strange stars
It has been suggested that the QPO phenomenon in LMXB's could be explained
when the central compact object is a strange star. In this work we investigate
within a standard model for disk accretion whether the observed clustering of
spin frequencies in a narrow band is in accordance with this hypothesis. We
show that frequency clustering occurs for accreting strange stars when typical
values of the parameters of magnetic field initial strength and decay time,
accretion rate are chosen. In contrast to hybrid star accretion no mass
clustering effect is found.Comment: 10 pages, 3 figures, version accepted for publication in New
Astronom
Time- and compartment-resolved proteome profiling of the extracellular niche in lung injury and repair
The extracellular matrix (ECM) is a key regulator of tissue morphogenesis and repair. However, its composition and architecture are not well characterized. Here, we monitor remodeling of the extracellular niche in tissue repair in the bleomycin-induced lung injury mouse model. Mass spectrometry quantified 8,366 proteins from total tissue and bronchoalveolar lavage fluid (BALF) over the course of 8 weeks, surveying tissue composition from the onset of inflammation and fibrosis to its full recovery. Combined analysis ofproteome, secretome, and transcriptome highlighted post-transcriptional events during tissue fibrogenesis and defined the composition of airway epithelial lining fluid. To comprehensively characterize the ECM, we developed a quantitative detergent solubility profiling (QDSP) method, which identified Emilin-2 and collagen-XXVIII as novel constituents of the provisional repair matrix. QDSP revealed which secreted proteins interact with the ECM, and showed drastically altered association of morphogens to the insoluble matrix upon injury. Thus, our proteomic systems biology study assigns proteins to tissue compartments and uncovers their dynamic regulation upon lung injury and repair, potentially contributing to the development of anti-fibrotic strategies
How to identify a Strange Star
Contrary to young neutron stars, young strange stars are not subject to the
r-mode instability which slows rapidly rotating, hot neutron stars to rotation
periods near 10 ms via gravitational wave emission. Young millisecond pulsars
are therefore likely to be strange stars rather than neutron stars, or at least
to contain significant quantities of quark matter in the interior.Comment: 4 pages, 1 figur
Intrinsic and extrinsic conduction contributions at nominally neutral domain walls in hexagonal manganites
Conductive and electrostatic atomic force microscopy (cAFM and EFM) are used
to investigate the electric conduction at nominally neutral domain walls in
hexagonal manganites. The EFM measurements reveal a propensity of mobile charge
carriers to accumulate at the nominally neutral domain walls in ErMnO3, which
is corroborated by cAFM scans showing locally enhanced d.c. conductance. Our
findings are explained based on established segregation enthalpy profiles for
oxygen vacancies and interstitials, providing a microscopic model for previous,
seemingly disconnected observations ranging from insulating to conducting
domain wall behavior. In addition, we observe variations in conductance between
different nominally neutral walls that we attribute to deviations from the
ideal charge-neutral structure within the bulk, leading to a superposition of
extrinsic and intrinsic contributions. Our study clarifies the complex
transport properties at nominally neutral domain walls in hexagonal manganites
and establishes new possibilities for tuning their electronic response based on
oxidation conditions, opening the door for domain-wall based sensor technology.Comment: 5 pages, 3 figure
Cooling of Neutron Stars: Two Types of Triplet Neutron Pairing
We consider cooling of neutron stars (NSs) with superfluid cores composed of
neutrons, protons, and electrons (assuming singlet-state pairing of protons,
and triplet-state pairing of neutrons). We mainly focus on (nonstandard)
triplet-state pairing of neutrons with the projection of the total
angular momentum of Cooper pairs onto quantization axis. The specific feature
of this pairing is that it leads to a power-law (nonexponential) reduction of
the emissivity of the main neutrino processes by neutron superfluidity. For a
wide range of neutron critical temperatures , the cooling of NSs with
the superfluidity is either the same as the cooling with the superfluidity, considered in the majority of papers, or much faster. The
cooling of NSs with density dependent critical temperatures and
can be imitated by the cooling of the NSs with some effective
critical temperatures and constant over NS cores. The
hypothesis of strong neutron superfluidity with is inconsistent
with current observations of thermal emission from NSs, but the hypothesis of
weak neutron superfluidity of any type does not contradict to observations.Comment: 10 pages, 6 figure
Are strange stars distinguishable from neutron stars by their cooling behaviour?
The general statement that strange stars cool more rapidly than neutron stars
is investigated in greater detail. It is found that the direct Urca process
could be forbidden not only in neutron stars but also in strange stars. If so,
strange stars would be slowly cooling and their surface temperatures would be
more or less indistinguishable from those of slowly cooling neutron stars. The
case of enhanced cooling is reinvestigated as well. It is found that strange
stars cool significantly more rapidly than neutron stars within the first years after birth. This feature could become particularly interesting if
continued observation of SN 1987A would reveal the temperature of the possibly
existing pulsar at its centre.Comment: 10 pages, 3 ps-figures, to appear in the proceedings of the
International Symposium on ''Strangeness in Quark Matter 1997``, April
14--18, Thera (Santorini), Hella
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