13,187 research outputs found
An assessment of the newest magnetar-SNR associations
Anomalous X-ray Pulsars and Soft-Gamma Repeaters groups are magnetar
candidates featuring low characteristic ages ().
At least some of them they should still be associated with the remnants of the
explosive events in which they were born, giving clues to the type of events
leading to their birth and the physics behind the apparent high value of the
magnetar magnetic fields. To explain the high values of , a self-consistent
picture of field growth also suggests that energy injection into the SNR is
large and unavoidable, in contrast with the evolution of {\it conventional}
SNR. This modified dynamics, in turn, has important implications for the
proposed associations. We show that this scenario yields low ages for the new
candidates CXOU J171405.7-381031/CTB 37B and XMMU J173203.3-344518/G353.6-0.7,
and predicted values agree with recently found , giving support to
the overall picture.Comment: Contributed talk to the ASTRONS 2010 Conference, Cesme, Turkey, Aug.
2-6 201
Pion mass effects on axion emission from neutron stars through NN bremsstrahlung processes
The rates of axion emission by nucleon-nucleon bremsstrahlung are calculated
with the inclusion of the full momentum contribution from a nuclear one pion
exchange (OPE) potential. The contributions of the neutron-neutron (nn),
proton-proton (pp) and neutron-proton (np) processes in both the nondegenerate
and degenerate limits are explicitly given. We find that the finite momentum
corrections to the emissivities are quantitatively significant for the
non-degenerate regime and temperature-dependent, and should affect the existing
axion mass bounds. The trend of these nuclear effects is to diminish the
emissivities
Color-flavor locked strange matter and strangelets at finite temperature
It is possible that a system composed of up, down and strange quarks consists
the true ground state of nuclear matter at high densities and low temperatures.
This exotic plasma, called strange quark matter (SQM), seems to be even more
favorable energetically if quarks are in a superconducting state, the so-called
color-flavor locked state. Here are presented calculations made on the basis of
the MIT bag model considering the influence of finite temperature on the
allowed parameters characterizing the system for stability of bulk SQM (the
so-called stability windows) and also for strangelets, small lumps of SQM, both
in the color-flavor locking scenario. We compare these results with the
unpaired SQM and also briefly discuss some astrophysical implications of them.
Also, the issue of strangelet's electric charge is discussed. The effects of
dynamical screening, though important for non-paired SQM strangelets, are not
relevant when considering pairing among all three flavor and colors of quarks.Comment: 17 pp. 15 figs., to appear in Phys. Rev.
The influence of magazines on men: normalizing and challenging young menâs prejudice with âladsâ magsâ
Social psychologists have argued that popular UK and USA menâs magazines known as ladsâ mags have normalized hostile sexism among young men. Three studies develop this argument. First, a survey of 423 young UK men found that ambivalent sexism predicted attitudes toward the consumption of ladsâ mags, but not other forms of direct sexual consumption (paying for sex or patronizing strip clubs). Second, Study 2 (N = 81) found that young men low in sexism rated sexist jokes as less hostile towards women, but not as either funnier nor more ironic, when those jokes were presented within a ladsâ mags context. These findings refute the idea that young men readily read ladsâ magsâ sexism as ironic or âharmless fun.â They show instead that placing sexist jokes in ladsâ mags contexts makes them appear less hostile. The third study (N = 275) demonstrated that young men perceived ladsâ mags as less legitimate after attempting to distinguish the contents of ladsâ mags from rapistsâ legitimations of their crimes. Implications for contemporary studies of masculinities and consumption are discussed
LASR-Guided Stellar Photometric Variability Subtraction: The Linear Algorithm For Significance Reduction
We develop a technique for removing stellar variability in the light curves
of -Scuti and similar stars. Our technique, which we name the Linear
Algorithm for Significance Reduction (LASR), subtracts oscillations from a time
series by minimizing their statistical significance in frequency space. We
demonstrate that LASR can subtract variable signals of near-arbitrary
complexity and can robustly handle close frequency pairs and overtone
frequencies. We demonstrate that our algorithm performs an equivalent fit as
prewhitening to the straightforward variable signal of KIC 9700322. We also
show that LASR provides a better fit to seismic activity than prewhitening in
the case of the complex -Scuti KOI-976.Comment: 9 pages, 5 figures, accepted for publication in Astronomy &
Astrophysics. Pseudocode and github link to code included in manuscrip
Influence of an Internal Magnetar on Supernova Remnant Expansion
Most of the proposed associations between magnetars and supernova remnant
suffer from age problems. Usually, supernova remnants ages are determined from
an approximation of the Sedov-Taylor phase relation between radius and age, for
a fixed energy of the explosion ~ 10^{51} erg. Those ages do not generally
agree with the characteristic ages of the (proposed) associated magnetars. We
show quantitatively that, by taking into account the energy injected on the
supernova remnant by magnetar spin-down, a faster expansion results, improving
matches between characteristic ages and supernova remnants ages. However, the
magnetar velocities inferred from observations would inviabilize some
associations. Since characteristic ages may not be good age estimators, their
influence on the likelihood of the association may not be as important.
In this work we present simple numerical simulations of supernova remnants
expansion with internal magnetars, and apply it to the observed objects. A
short initial spin period, thought to be important for the very generation of
the magnetic field, is also relevant for the modified expansion of the remnant.
We next analyze all proposed associations case-by-case, addressing the
likelyhood of each one, according to this perspective. We consider a larger
explosion energy and reasses the characteristic age issue, and conclude that
about 50% of the associations can be true ones, provided SGRs and AXPs are
magnetars.Comment: 30 pages, AAStex, 5 figures, format fixe
Strange stars in low-mass binary pulsar systems
Based on observational facts and a variety of theoretical arguments we
discuss in this work the possibility that pulsars in Low-Mass Binary Pulsar
systems could be strange stars rather than neutron stars. It is shown that,
although subject to reasonable uncertainties, the consideration of the physics
of the SQM core and thin normal crusts leads to the prediction of several
observed features of the magnetic field history of these systems whitin this
working hypothesis.Comment: 6 pages, no figures, PlainTex file submitted to IJMP
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