12,651 research outputs found
An ALMA Dynamical Mass Estimate of the Proposed Planetary-mass Companion FW Tau C
Dynamical mass estimates down to the planet-mass regime can help to
understand planet formation. We present Atacama Large Millimeter/submillimeter
Array (ALMA) 1.3 mm observations of FW Tau C, a proposed ~10
planet-mass companion at ~330 au from the host binary FW Tau AB. We spatially
and spectrally resolve the accretion disk of FW Tau C in CO (2-1). By
modeling the Keplerian rotation of gas, we derive a dynamical mass of ~0.1
. Therefore, FW Tau C is unlikely a planet, but rather a low-mass star
with a highly inclined disk. This also suggests that FW Tau is a triple system
consisting of three ~0.1 stars.Comment: Accepted for publication in ApJ
Quantum Phase Liquids-Fermionic Superfluid without Phase Coherence
We investigate the two dimensional generalized attractive Hubbard model in a
bipartite lattice, and and a "quantum phase liquid" phase, in which the
fermions are paired but don't have phase coherence at zero temperature, in
analogy to quantum spin liquid phase. Then, two types of topological quantum
phase liquids with a small external magnetic field-Z2 quantum phase liquids and
chiral quantum phase liquids-are discussed.Comment: 7 pages, 2 figure
Bulk Viscosity of dual Fluid at Finite Cutoff Surface via Gravity/Fluid correspondence in Einstein-Maxwell Gravity
Based on the previous paper arXiv:1207.5309, we investigate the possibility
to find out the bulk viscosity of dual fluid at the finite cutoff surface via
gravity/fluid correspondence in Einstein-Maxwell gravity. We find that if we
adopt new conditions to fix the undetermined parameters contained in the stress
tensor and charged current of the dual fluid, two new terms appear in the
stress tensor of the dual fluid. One new term is related to the bulk viscosity
term, while the other can be related to the perturbation of energy density. In
addition, since the parameters contained in the charged current are the same,
the charged current is not changed.Comment: 15 pages, no figure, typos corrected, new references and comments
added, version accepted by PL
Submillimeter Array CO(2-1) Imaging of the NGC 6946 Giant Molecular Clouds
We present a CO(2-1) mosaic map of the spiral galaxy NGC 6946 by combining
data from the Submillimeter Array and the IRAM 30 m telescope. We identify 390
giant molecular clouds (GMCs) from the nucleus to 4.5 kpc in the disk. GMCs in
the inner 1 kpc are generally more luminous and turbulent, some of which have
luminosities >10^6 K km/s pc^2 and velocity dispersions >10 km/s. Large-scale
bar-driven dynamics likely regulate GMC properties in the nuclear region.
Similar to the Milky Way and other disk galaxies, GMC mass function of NGC 6946
has a shallower slope (index>-2) in the inner region, and a steeper slope
(index<-2) in the outer region. This difference in mass spectra may be
indicative of different cloud formation pathways: gravitational instabilities
might play a major role in the nuclear region, while cloud coalescence might be
dominant in the outer disk. Finally, the NGC 6946 clouds are similar to those
in M33 in terms of statistical properties, but they are generally less luminous
and turbulent than the M51 clouds.Comment: Published in Ap
The effects of massive graviton on the equilibrium between the black hole and radiation gas in an isolated box
It is well known that the black hole can has temperature and radiate the
particles with black body spectrum, i.e. Hawking radiation. Therefore, if the
black hole is surrounded by an isolated box, there is a thermal equilibrium
between the black hole and radiation gas. A simple case considering the thermal
equilibrium between the Schwarzschild black hole and radiation gas in an
isolated box has been well investigated previously in detail, i.e. taking the
conservation of energy and principle of maximal entropy for the isolated system
into account. In this paper, following the above spirit, the effects of massive
graviton on the thermal equilibrium will be investigated. For the gravity with
massive graviton, we will use the de Rham-Gabadadze-Tolley (dRGT) massive
gravity which has been proven to be ghost free. Because the graviton mass
depends on two parameters in the dRGT massive gravity, here we just investigate
two simple cases related to the two parameters, respectively. Our results show
that in the first case the massive graviton can suppress or increase the
condensation of black hole in the radiation gas although the diagram is
similar like the Schwarzschild black hole case. For the second case, a new
diagram has been obtained. Moreover, an interesting and important
prediction is that the condensation of black hole just increases from the zero
radius of horizon in this case, which is very different from the Schwarzschild
black hole case.Comment: 9 pages, 4 figure
Generalized Vaidya Solutions and Misner-Sharp mass for -dimensional massive gravity
Dynamical solutions are always of interest to people in gravity theories. We
derive a series of generalized Vaidya solutions in the -dimensional de
Rham-Gabadadze-Tolley (dRGT) massive gravity with a singular reference metric.
Similar to the case of the Einstein gravity, the generalized Vaidya solution
can describe shining/absorbing stars. Moreover, we also find a more general
Vaidya-like solution by introducing a more generic matter field than the pure
radiation in the original Vaidya spacetime. As a result, the above generalized
Vaidya solution is naturally included in this Vaidya-like solution as a special
case. We investigate the thermodynamics for this Vaidya-like spacetime by using
the unified first law, and present the generalized Misner-Sharp mass. Our
results show that the generalized Minser-Sharp mass does exist in this
spacetime. In addition, the usual Clausius relation holds on
the apparent horizon, which implicates that the massive gravity is in a
thermodynamic equilibrium state. We find that the work density vanishes for the
generalized Vaidya solution, while it appears in the more general Vaidya-like
solution. Furthermore, the covariant generalized Minser-Sharp mass in the
-dimensional de Rham-Gabadadze-Tolley massive gravity is also derived by
taking a general metric ansatz into account.Comment: 10 pages, no figure, version published in PR
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