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1.
There are many rotating spheroids in the universe, and many astronomers and physicists have used theoretical methods to study the characteristics of stellar gravity since Newton's time. This paper derives the solutions of eight scattering states ( ϕ ( 0 ) , χ ( 0 ) , ϕ ( 1 ) , χ ( 1 ) , ϕ ( 2 ) $$ \Big({\phi}^{(0)},{\chi}^{(0)},{\phi}^{(1)},{\chi}^{(1)},{\phi}^{(2)} $$ , χ ( 2 ) , ϕ ( 3 ) $$ {\chi}^{(2)},{\phi}^{(3)} $$ , and χ ( 3 ) ) $$ {\chi}^{(3)}\Big) $$ for the Dirac equation with positive-energy E = im $$ E= im $$ , and establishes the relationship between the differential scattering cross section σ i ( p , θ , φ ) $$ {\sigma}_i\left(p,\theta, \varphi \right) $$ and the stellar density μ $$ \mu $$ . It is found that: (1) For the eight scattering states, their average scattering cross-sections σ i ‾ $$ \overline{\sigma_i} $$ are proportional to μ 2 $$ {\mu}^2 $$ , and depend on the star's radius, and the higher the stellar density μ $$ \mu $$ , the greater the sensitivity of σ i ‾ $$ \overline{\sigma i} $$ to the change of μ $$ \mu $$ ; (2) For the four scattering states χ ( i ) , i = 0 , 1 , 2 , 3 $$ {\chi}^{(i)},i=0,1,2,3 $$ , their average scattering amplitudes f ‾ ( p , θ ) $$ \overline{f}\left(p,\theta \right) $$ and σ ‾ ( p , θ ) $$ \overline{\sigma}\left(p,\theta \right) $$ depend on the mass m $$ m $$ of the particles; while for the other four scattering states ϕ ( i ) $$ {\phi}^{(i)} $$ , i = 0 , 1 , 2 , 3 $$ i=0,1,2,3 $$ , then f ‾ $$ \overline{f} $$ and σ ‾ $$ \overline{\sigma} $$ are independent of m $$ m $$ . This study links the gravitational characteristics of stars with the scattering cross section, creating a new method for studying the gravitational characteristics, which helps to reveal the mystery of the gravity of rotating ellipsoidal stars.  相似文献   

2.
This article focuses on the implications of the recently developed commutative formulation based on branch-cutting cosmology, the Wheeler–DeWitt equation, and Hořava–Lifshitz quantum gravity. Assuming a mini-superspace of variables, we explore the impact of an inflaton-type scalar field ϕ ( t ) $$ \phi (t) $$ on the dynamical equations that describe the trajectories evolution of the scale factor of the Universe, characterized by the dimensionless helix-like function ln − 1 [ β ( t ) ] $$ {\ln}^{-1}\left[\beta (t)\right] $$ . This scale factor characterizes a Riemannian foliated spacetime that topologically overcomes the big bang and big crunch singularities. Taking the Hořava–Lifshitz action as our starting point, which depends on the scalar curvature of the branched Universe and its derivatives, with running coupling constants denoted as g i $$ {g}_i $$ , the commutative quantum gravity approach preserves the diffeomorphism property of General Relativity, maintaining compatibility with the Arnowitt–Deser–Misner formalism. We investigate both chaotic and nonchaotic inflationary scenarios, demonstrating the sensitivity of the branch-cut Universe's dynamics to initial conditions and parameterizations of primordial matter content. The results suggest a continuous connection of Riemann surfaces, overcoming primordial singularities and exhibiting diverse evolutionary behaviors, from big crunch to moderate acceleration.  相似文献   

3.
Circumstellar disk (CD) around the first generation of stars have been numerically investigated here to see if the cooling regimes also play a role in the formation and evolution of the disk associated with the most massive protostars (MMPS). Also, an emphasis is given to exploring the effect of the initial turbulent motion of the metal-free gas on the resulting morphology of the CD. For this, a systematic range of Mach number ℳ = 0 . 1 − 1 . 0 $$ \mathcal{M}=0.1-1.0 $$ has been examined. It has been found that the disk-to-star mass ratio M disk $$ {M}_{\mathrm{disk}} $$ / M star $$ {M}_{\mathrm{star}} $$ is larger when the model evolution is based on the first H 2 $$ {}_2 $$ line cooling followed by subsequent cooling via collision-induced emission than in the model where only H 2 $$ {}_2 $$ line cooling remains operative. Also, irrespective of the initial turbulence in the cloud, the former type of model yields a CD as massive as 7.66 M ⊙ $$ {}_{\odot } $$ while the latter type produces a disk as massive as 1.29 M ⊙ $$ {}_{\odot } $$ . Moreover, the inner part of the CD is found dominated by higher subsonic turbulent motions in the case of the former type of models than in the latter type. CDs around MMPS in both types of models show stable disk structures.  相似文献   

4.
In this work, the entanglement entropy is examined within the context of deep inelastic scattering in e p $$ ep $$ collisions. The calculation is based on a formalism where the partonic state at small- x $$ x $$ is maximally entangled, consisting of a large number of micro-states occurring with equal probabilities. Analytical expressions for the number of gluons, N gluon $$ {N}_{\mathrm{gluon}} $$ , are considered, derived from gluon saturation models for dipole-target amplitudes within the framework of the Quantum Chromodynamics (QCD) color dipole picture. A comparison of the entanglement entropy with thermodynamic entropy measured in p p $$ pp $$ and e p $$ ep $$ collisions at high energies is done.  相似文献   

5.
The Seyfert 2 galaxy NGC 2273 is a prime target to explore how active nuclei can be fed. It has a star-forming innermost nuclear ring with a radius of 0.33kpc from where material may be funneled to the supermassive black hole in its center. In this article, we discuss high-resolution adaptive optics aided JHKs images of NGC 2273 taken with the Large Binocular Telescope. Using Galfit we decomposed the innermost part of NGC 2273 into a core, a disk, and a ring using 58 parameters, 44 of them were used to describe the ring. The stellar mass of the ring was found to be 12 × 1 0 8 M ⊙ $$ \times 1{0}^8{\mathrm{M}}_{\odot } $$ , a factor of 10 higher than its molecular gas mass. A continuous gas flow via the main stellar bar of NGC 2273 during the lifetime of the bar of up to 10 M ⊙ yr − 1 $$ {\mathrm{M}}_{\odot }{\mathrm{yr}}^{-1} $$ is required to provide the fuel for the formation of the stars unless the star formation efficiency is on the order of 10%. This does not affect the fueling of the nuclear source as the amount of molecular gas required for this low-luminosity active galaxy to achieve this is on the order of 1 0 4 M ⊙ $$ 1{0}^4{\mathrm{M}}_{\odot } $$ only.  相似文献   

6.
We present relative astrometric and photometric measurements of visual double stars made in 2013–2015, with PISCO2 installed at the 76-cm refractor of Côte d'Azur Observatory in Nice (France). Our observing list contains orbital couples as well as double stars whose motion is still uncertain. Most of the observations were done in 2015, but some other observations of wide couples were done in 2013–2014 (0.3% of the total of the observations). Three different techniques were used for obtaining measurements: lucky imaging, speckle interferometry and the direct vector autocorrelation method. From our observations of 2837 multiple stars, we obtained 5182 new measurements with angular separations in the range of 0 ″ $$ {}^{{\prime\prime} } $$ .1–32 ″ $$ {}^{{\prime\prime} } $$ and an average accuracy of 0 ″ . 018 $$ {0}^{{\prime\prime} }.018 $$ . The mean error on the position angles is 0°.8. Most of the position angles were determined without the usual 180° ambiguity with the application of the direct vector autocorrelation technique and/or by inspection of the Lucky images or the long integration files. We managed to routinely monitor faint systems ( m V ≈ 9 − 11 $$ {m}_V\approx 9-11 $$ ) with large magnitude difference (up to Δ m V ≈ 4 . 5 $$ \Delta {m}_V\approx 4.5 $$ ). We have thus been able to measure 21 systems containing red dwarf stars that had been poorly monitored since their discovery, from which we estimated the stellar masses thanks to Gaia measurements. We also measured the magnitude difference of the two components of 1079 double stars with an estimated error of 0.2 mag. Except for a few objects that are discussed, our measurements are in good agreement with the ephemerides computed with published orbital elements, even for the double stars whose separation is smaller than the diffraction limit. Thanks to good seeing images and with the use of high-contrast numerical filters, we have also been able to obtain 196 measurements with an angular separation smaller than the diffraction limit of our instrumentation, and consistent with those obtained with larger telescopes. We also report measurements of the 164 new double stars that we found in the files obtained during the observations. Finally, from a study of the DR3 Gaia release, it is shown that all the objects of the Tycho Double Star Catalog that we did not resolve in 2015 are probably false detections by Tycho.  相似文献   

7.
In this work, we study how to improve well-known techniques for detecting progenitors/descendants of galaxies, such as the NDpredict program, when applied to galaxies in clusters. The improvement of this particular method is based on the use of the red sequence of galaxies in those environments. Objects close to the red sequence in the color and magnitude diagram are more likely to belong to the cluster. This defines a probability scale which is then combined with the one generated by NDpredict. This procedure is optimized for the study of galaxies in clusters over different epochs. Our main result is that, for a sample composed of 120 $$ 120 $$ clusters, with masses greater than 10 13.25 M ⊙ $$ {10}^{13.25}{M}_{\odot } $$ , selected from the IllustrisTNG simulations (namely, the TNG100 runs). In 99 % $$ 99\% $$ of the cases (i.e., 119 $$ 119 $$ systems), we obtain better performance with the red sequence method in comparison to the original NDpredict, and the average gain obtained is 28 % $$ 28\% $$ in the identification of descendants for this sample of cluster galaxies.  相似文献   

8.
We extend our two previous studies on the existence of stable orbits in the Solar System by examining the domain between Jupiter and Saturn. We place (1) a massless object, (2) a Moon-mass object, (3) a Mars-mass object, (4) an Earth-mass object, and (5) a Uranus-mass object in the said region. Note that these objects are considered separately in the framework of our simulations. Our goal is to explore the orbital stability of those objects. We employ the Lie-integration method, which is fast and well established, allowing us to solve the respective differential equations for the N $$ N $$ -body system. Hence, we consider the celestial bodies spanning from Jupiter to Neptune, including the aforementioned test object, the main focus for our model simulations. The integrations indicate that in some models the test objects placed in the region between Jupiter and Saturn reside in that region for more than 600 Myr. Between 5 and 10 au, mean-motion resonances (MMRs) take place acting upon the test objects akin to simulations of Paper I and II. Our models indicate relatively small differences for the long-term stability of the five test objects notwithstanding their vastly different masses. Generally, it is found that between a ini = 7 . 04 $$ {a}_{\mathrm{ini}}=7.04 $$  and 7.13 au the orbits become unstable mostly within 5 million years and further out, that is, up to a ini = 7 . 29 $$ {a}_{\mathrm{ini}}=7.29 $$  au, the duration of stability lengthens to up to hundreds of millions of years.  相似文献   

9.
The first JWST observations of hot Jupiters showed an unexpected detection of SO 2 $$ {}_2 $$ in their hydrogen-rich atmospheres. We investigate how much sulfur can be expected in the atmospheres of rocky exoplanets and which sulfur molecules can be expected to be most abundant and detectable by transmission spectroscopy. We run thermochemical equilibrium models at the crust–atmosphere interface, considering surface temperatures 500–5000 K, surface pressures 1–100 bar, and various sets of element abundances based on common rock compositions. Between 1000 and 2000 K, we find gaseous sulfur concentrations of up to 25% above the rock in our models. SO 2 $$ {}_2 $$ , SO, H 2 $$ {}_2 $$ S, and S 2 $$ {}_2 $$ are by far the most abundant sulfur molecules. SO 2 $$ {}_2 $$ shows potentially detectable features in transmission spectra at about 4 μ $$ \mu $$ m, between 7 and 8 μ $$ \mu $$ m, and beyond 15 μ $$ \mu $$ m. In contrast, the sometimes abundant H 2 $$ {}_2 $$ S molecule is difficult to detect in these spectra, which are mostly dominated by H 2 $$ {}_2 $$ O and CO 2 $$ {}_2 $$ . Although the molecule PS only occurs with concentrations < 300 $$ <300 $$ ppm, it can cause a strong absorption feature between 0.3 and 0.65 μ $$ \mu $$ m in some of our models for high surface pressures. The detection of sulfur molecules would enable a better characterization of the planetary surface.  相似文献   

10.
The pulsar magnetic inclination angle is a key parameter for pulsar physics. It influences the observable properties of pulsars, such as the pulse beam width, braking index, polarization, and emission geometry. In this study, we give a brief overview of the current state of knowledge and research on this parameter and its implications for the internal physics of pulsars. We use the observed pulsar data of magnetic inclination angle and braking index to constrain the star's number of precession cycles, ξ $$ \xi $$ , which reflects the interaction between superfluid neutrons and other particles inside a neutron star (NS). We apply the method proposed by Cheng et al. (Cheng, Q., Zhang, S. N., Zheng, X. P., & Fan, X. L., 2019, Phys. Rev. D, 99, 083011) to analyze the data of PSR J2013 + 3845 and obtain the constraints for ξ $$ \xi $$ ranging from 2 . 393 × 1 0 5 $$ 2.393\times 1{0}^5 $$ to 1 . 268 × 1 0 6 $$ 1.268\times 1{0}^6 $$ . And further analysis suggests that the internal magnetic field structure of PSR J2013 + 3845 is likely dominated by toroidal components. This study may help us understand the process of internal viscous dissipation and the related evolution of the inclination angles of pulsars, and may have important implications for the study of continuous gravitational wave emissions from NS.  相似文献   

11.
Located at less than two pc away, Luhman 16 AB (WISE J104915.57-531906.1) is the closest pair of brown dwarfs and the third closest “stellar” system to Earth. An exoplanet candidate in the Luhman 16 binary system was reported in 2017 based on a weak astrometric signature in the analysis of 12 HST epochs. An additional epoch collected in 2018 and re-analysis of the data with more advanced methods further increased the significance level of the candidate, consistent with a Neptune-mass exoplanet orbiting one of the Luhman 16 brown dwarf components. We report the joint analysis of these previous data together with two new astrometric HST epochs we obtained to confirm or disprove this astrometric signature. Our new analysis rules out the presence of a planet orbiting one component of the Luhman 16 AB system for masses ℳ $$ \mathrm{\mathcal{M}} $$ ≳ $$ \gtrsim $$ 1.5 M♆ (Neptune masses) and periods between 400 and 5000 days. However, the presence of third bodies with masses ℳ $$ \mathrm{\mathcal{M}} $$ ≲ $$ \lesssim $$ 3 M♆ and periods between 2 and 400 days ( ∼ $$ \sim $$ 1.1 years) cannot be excluded. Our measurements make significant improvements to the characterization of this sub-stellar binary, including its mass-ratio 0.8305 ± 0.0006 $$ \pm 0.0006 $$ , individual component masses 35.4 ± $$ \pm $$ 0.2 MꝜ and 29.4 ± $$ \pm $$ 0.2 MꝜ (Jupiter masses), and parallax distance 1.9960 pc ± $$ \pm $$ 50 AU. Comparison of the masses and luminosities of Luhman 16 AB to several evolutionary models shows persistent discrepancies in the ages of the two components, but strengthens the case that this system is a member of the 510 ± $$ \pm $$ 95 Myr Oceanus Moving Group.  相似文献   

12.
We evaluate the feasibility of Bose–Einstein condensate stars (BECS) as models for the interior of neutron stars (NSs). BECS are compact objects composed of bosons, formed through the spin-parallel pairing of neutrons. Here, we utilize the astronomical data from GW170817, XMMU J173203.3-344518 (the lightest NS known), and a novel lower limit on NS core heat capacity to scrutinize the compatibility of BECS with these recent observations of NSs. Our specific focus is to constrain the values of the scattering length a $$ a $$ , parameter determining the strength of particle interactions in the model. Our analysis suggests that if the stars involved in GW170817 were BECSs, the scattering length of their constituent bosons should fall within the 4 $$ 4 $$ to 10 $$ 10 $$ fm range. Additionally, at a scattering length of a ∼ 3.1 − 4 $$ a\sim 3.1-4 $$ fm, stars with mass and radius characteristics akin to XMMU J173203.3-344518 are identified. Moreover, we find that the heat capacity depends on the mass and temperature of BECS, and surpasses the established lower bound for NS cores when a > 2 − 5 $$ a>2-5 $$ fm. In summary, our results endorse BECS models with a ∼ 4 $$ a\sim 4 $$ fm, providing NS observables in agreement with diverse observations and contributing to the understanding of NS interiors.  相似文献   

13.
Neutron stars may experience differential rotation on short, dynamical timescales following extreme astrophysical events like binary neutron star mergers. In this work, the masses and radii of differentially rotating neutron star models are computed. We employ a set of equations of states for dense hypernuclear and Δ $$ \Delta $$ -admixed-hypernuclear matter obtained within the framework of CDF theory in the relativistic Hartree-Fock (RHF) approximation. Results are shown for varying meson- Δ $$ \Delta $$ couplings, or equivalently the Δ $$ \Delta $$ -potential in nuclear matter. A comparison of our results with those obtained for nonrotating stars shows that the maximum mass difference between differentially rotating and static stars is independent of the underlying particle composition of the star. We further find that the decrease in the radii and increase in the maximum masses of stellar models when Δ $$ \Delta $$ -isobars are added to hyperonuclear matter (as initially observed for static and uniformly rotating stars) persist also in the case of differentially rotating neutron stars.  相似文献   

14.
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15.
The effects of a minimal length on the Kerr metric are studied within the pseudo-complex General Relativity (pcGR), which has a minimal length parameter and also depends on a r $$ r $$ -dependent metric, allowing for the accumulation of dark energy around a star. The relevant parameters are the rotational Kerr parameter a $$ a $$ , the mass of a black hole, and a parameter measuring the amount of dark energy accumulated. It is found that the metric is modified by a factor, depending on r $$ r $$ , resulting in a maximal acceleration. This factor shows several singularities. For small black holes, the corresponding effective potentials exhibit potential barriers, avoiding the increase of the black hole's mass. It is found that the effects of a minimal length are only of importance for very small mass black holes and vanish for macroscopic black holes.  相似文献   

16.
This paper focuses on the implications of a commutative formulation that integrates branch-cutting cosmology, the Wheeler–DeWitt equation, and Hořava–Lifshitz quantum gravity. Building on a mini-superspace structure, we explore the impact of an inflaton-type scalar field on the wave function of the Universe. Specifically analyzing the dynamical solutions of branch-cut gravity within a mini-superspace framework, we emphasize the scalar field's influence on the evolution of the evolution of the wave function of the Universe. Our research unveils a helix-like function that characterizes a topologically foliated spacetime structure. The starting point is the Hořava–Lifshitz action, which depends on the scalar curvature of the branched Universe and its derivatives, with running coupling constants denoted as g i $$ {g}_i $$ . The corresponding wave equations are derived and are resolved. The commutative quantum gravity approach preserves the diffeomorphism property of General Relativity, maintaining compatibility with the Arnowitt–Deser–Misner formalism. Additionally, we delve into a mini-superspace of variables, incorporating scalar-inflaton fields and exploring inflationary models, particularly chaotic and nonchaotic scenarios. We obtained solutions for the wave equations without recurring to numerical approximations.  相似文献   

17.
There exist isolated elliptical galaxies, whose dynamics can be modeled without resorting to dark matter or MOND, for example, NGC 7507. Such objects lack understanding within the current framework of galaxy formation. The isolated elliptical NGC 5812 is another object to investigate a possible role of isolation. We use globular clusters (GCs) and the galaxy light itself as dynamical tracers to constrain its mass profile. We employ Gemini/GMOS mask spectroscopy, apply the GMOS reduction procedures provided within IRAF, measure GC velocities by cross correlation methods and extract the line-of-sight kinematics of galaxy spectra using the tool pPXF. We identify 28 GCs with an outermost galactocentric distance of 20 kpc, for which velocities could be obtained. Furthermore, 16 spectra of the integrated galaxy light out to 6 kpc have been used to model the central kinematics. These spectra provide evidence for a disturbed velocity field, which is plausible given the disturbed morphology of the galaxy. We construct spherical Jeans models for the galaxy light and apply tracer mass estimators for the globular clusters. With the assumptions inherent to the mass estimators, MOND is compatible with the mass out to 20 kpc. However, a dark matter free galaxy is not excluded, given the uncertainties related to a possible nonsphericity and a possible nonequilibrium state. We find one globular cluster with an estimated mass of 1 . 6 × 1 0 7 M ⊙ $$ 1.6\times 1{0}^7{M}_{\odot } $$ , the first Ultra Compact Dwarf in an isolated elliptical. We put NGC 5812 into the general context of dark matter or alternative ideas in elliptical galaxies. The case for a MONDian phenomenology also among early-type galaxies has become so strong that deviating cases appear astrophysically more interesting than agreements. The baryonic Tully Fisher relation (BTFR) as predicted by MOND is observed in some samples of early-type galaxies, in others not. However, in cases of galaxies that deviate from the MONDian prediction, data quality and data completeness are often problematic.  相似文献   

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