6,704 research outputs found
Study of the neutron star structure in strong magnetic fields including the anomalous magnetic moments
We study the effects of strong magnetic fields on the neutron star structure.
If the interior field of a star is on the same order of the surface field
currently observed, the influences of the magnetic field on the star mass and
radius are negligible. If one assumes that the internal magnetic field can be
as large as that estimated from the scalar virial theorem, considerable effects
can be induced. The maximum mass of stars is arisen substantially while the
central density is largely suppressed. For two equal-mass stars the radius of
the magnetic star can be larger by about 10% 20% than the nonmagnetic
star.Comment: 26 pages, 5 postscript figures; replaced by the revised version,
Chin. J. Astron. Astrophys., accepte
Cold ideal equation of state for strongly magnetized neutron-star matter: effects on muon production and pion condensationn
Neutron stars with very strong surface magnetic fields have been suggested as
the site for the origin of observed soft gamma repeaters (SGRs). In this paper
we investigate the influence of such strong magnetic fields on the properties
and internal structure of these magnetized neutron stars (magnetars). We study
properties of a degenerate equilibrium ideal neutron-proton-electron (npe) gas
with and without the effects of the anomalous nucleon magnetic moments in a
magnetic field. The presence of a sufficiently strong magnetic field changes
the ratio of protons to neutrons as well as the neutron drip density. We also
study the appearance of muons as well as pion condensation in strong magnetic
fields. We discuss the possibility that boson condensation in the interior of
magnetars might be a source of SGRs.Comment: 10 pages included 9 figures, ApJ in pres
The DEIMOS 10k spectroscopic survey catalog of the COSMOS field
We present a catalog of 10718 objects in the COSMOS field observed through
multi-slit spectroscopy with the Deep Imaging Multi-Object Spectrograph
(DEIMOS) on the Keck II telescope in the wavelength range ~5500-9800A. The
catalog contains 6617 objects with high-quality spectra (two or more spectral
features), and 1798 objects with a single spectroscopic feature confirmed by
the photometric redshift. For 2024 typically faint objects we could not obtain
reliable redshifts. The objects have been selected from a variety of input
catalogs based on multi-wavelength observations in the field, and thus have a
diverse selection function, which enables the study of the diversity in the
galaxy population. The magnitude distribution of our objects is peaked at
I_AB~23 and K_AB~21, with a secondary peak at K_AB~24. We sample a broad
redshift distribution in the range 0<z<6, with one peak at z~1, and another one
around z~4. We have identified 13 redshift spikes at z>0.65 with chance
probabilities <4xE-4$, some of which are clearly related to protocluster
structures of sizes >10 Mpc. An object-to-object comparison with a multitude of
other spectroscopic samples in the same field shows that our DEIMOS sample is
among the best in terms of fraction of spectroscopic failures and relative
redshift accuracy. We have determined the fraction of spectroscopic blends to
about 0.8% in our sample. This is likely a lower limit and at any rate well
below the most pessimistic expectations. Interestingly, we find evidence for
strong lensing of Ly-alpha background emitters within the slits of 12 of our
target galaxies, increasing their apparent density by about a factor of 4.Comment: 28 pages, 11 figures and 5 tables. The full catalogue table is
available on http://cosmos.astro.caltech.edu. Accepted for publication in the
Astrophysical Journa
A Large Scale Structure at Redshift 1.71 in the Lockman Hole
We previously identified LH146, a diffuse X-ray source in the Lockman Hole,
as a galaxy cluster at redshift 1.753. The redshift was based on one
spectroscopic value, buttressed by seven additional photometric redshifts. We
here confirm the previous spectroscopic redshift and present concordant
spectroscopic redshifts for an additional eight galaxies. The average of these
nine redshifts is 1.714 +/- 0.012 (error on mean). Scrutiny of the galaxy
distribution in redshift and the plane of the sky shows that there are two
concentrations of galaxies near the X-ray source. In addition there are three
diffuse X-ray sources spread along the axis connecting the galaxy
concentrations. LH146 is one of these three and lies approximately at the
center of the two galaxy concentrations and the outer two diffuse X-ray
sources. We thus conclude that LH146 is at the redshift initially reported but
it is not a single virialized galaxy cluster as previously assumed. Rather it
appears to mark the approximate center of a larger region containing more
objects. For brevity we term all these objects and their alignments as large
scale structure. The exact nature of LH146 itself remains unclear.Comment: 22 pages, 15 figures, accepted for publication in the Astrophysical
Journa
Searching for Exoplanets Using a Microresonator Astrocomb
Detection of weak radial velocity shifts of host stars induced by orbiting
planets is an important technique for discovering and characterizing planets
beyond our solar system. Optical frequency combs enable calibration of stellar
radial velocity shifts at levels required for detection of Earth analogs. A new
chip-based device, the Kerr soliton microcomb, has properties ideal for
ubiquitous application outside the lab and even in future space-borne
instruments. Moreover, microcomb spectra are ideally suited for astronomical
spectrograph calibration and eliminate filtering steps required by conventional
mode-locked-laser frequency combs. Here, for the calibration of astronomical
spectrographs, we demonstrate an atomic/molecular line-referenced,
near-infrared soliton microcomb. Efforts to search for the known exoplanet HD
187123b were conducted at the Keck-II telescope as a first in-the-field
demonstration of microcombs
Nyquist method for Wigner-Poisson quantum plasmas
By means of the Nyquist method, we investigate the linear stability of
electrostatic waves in homogeneous equilibria of quantum plasmas described by
the Wigner-Poisson system. We show that, unlike the classical Vlasov-Poisson
system, the Wigner-Poisson case does not necessarily possess a Penrose
functional determining its linear stability properties. The Nyquist method is
then applied to a two-stream distribution, for which we obtain an exact,
necessary and sufficient condition for linear stability, as well as to a
bump-in-tail equilibrium.Comment: 6 figure
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