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1.
The accretion of hot slowly rotating gas onto a supermassive black hole is considered. The important case where the velocities of turbulent pulsations at the Bondi radius r B are low, compared to the speed of sound c s, is studied. Turbulence is probably responsible for the appearance of random average rotation. Although the angular momentum at r B is low, it gives rise to the centrifugal barrier at a depth r c = l 2 /GM BH ≪ r B, that hinders supersonic accretion. The numerical solution of the problem of hot gas accretion with finite angular momentum is found taking into account electron thermal conductivity and bremsstrahlung energy losses of two temperature plasma for density and temperature near Bondi radius similar to observed in M87 galaxy. The saturation of the Spitzer thermal conductivity was also taken into account. The parameters of the saturated electron thermal conductivity were chosen similar to the parameters used in the numerical simulations of interaction of the strong laser beam radiation with plasma targets. These parameters are confirmed in the experiments. It is shown that joint action of electron thermal conductivity and free-free radiation leads to the effective cooling of accreting plasma and formation of the subsonic settling of accreting gas above the zone of a centrifugal barrier. A toroidal condensation and a hollow funnel that separates the torus from the black hole emerge near the barrier. The barrier divides the flow into two regions: (1) the settling zone with slow subKeplerian rotation and (2) the zone with rapid supersonic nearly Keplerian rotation. Existence of the centrifugal barrier leads to significant decrease of the accretion rate Ṁ in comparison with the critical Bondi solution for γ = 5/3 for the same values of density and temperature of the hot gas near Bondi radius. Shear instabilities in the torus and related friction cause the gas to spread slowly along spirals in the equatorial plane in two directions.As a result, outer (r > r c) and inner (r < r c) disks are formed. The gas enters the immediate neighborhood of the black hole or the zone of the internal ADAF flow along the accretion disk (r < r c). Since the angular momentum is conserved, the outer disk removes outward an excess of angular momentum along with part of the matter falling into the torus. It is possible, that such outer Keplerian disk was observed by Hubble Space Telescope around the nucleus of the M87 galaxy in the optical emission lines. We discuss shortly the characteristic times during which the accretion of the gas with developed turbulence should lead to the changes in the orientation of the torus, accretion disk and, possibly, of the jet.  相似文献   

2.
Our goal is to study the regime of disk accretion in which almost all of the angular momentum and energy is carried away by the wind outflowing from the disk in numerical experiments. For this type of accretion the kinetic energy flux in the outflowing wind can exceed considerably the bolometric luminosity of the accretion disk, what is observed in the plasma flow from galactic nuclei in a number of cases. In this paper we consider the nonrelativistic case of an outflow from a cold Keplerian disk. All of the conclusions derived previously for such a system in the self-similar approximation are shown to be correct. The numerical results agree well with the analytical predictions. The inclination angle of the magnetic field lines in the disk is less than 60°, which ensures a free wind outflow from the disk, while the energy flux per wind particle is greater than the particle rotation energy in its Keplerian orbit by several orders of magnitude, provided that the ratio r A/r ? 1, where r A is the Alfvénic radius and r is the radius of the Keplerian orbit. In this case, the particle kinetic energy reaches half the maximum possible energy in the simulation region. The magnetic field collimates the outflowing wind near the rotation axis and decollimates appreciably the wind outflowing from the outer disk periphery.  相似文献   

3.
We consider the relationship between the total HI mass in late-type galaxies and the kinematic properties of their disks. The mass MHI for galaxies with a wide variety of properties, from dwarf dIrr galaxies with active star formation to giant low-brightness galaxies, is shown to correlate with the product VcR0 (Vc is the rotational velocity, and R0 is the radial photometric disks cale length), which characterizes the specific angular momentum of the disk. This correlation, along with the decrease in the relative mass of the gas in a galaxy with increasing Vc, can be explained in terms of the previous assumption that the gas density in the disks of most galaxies is maintained at a level close to the threshold (marginal) stability of a gaseous layer to local gravitational perturbations. In this case, the regulation mechanism of the star formation rate associated with the growth of local gravitational instability in the gaseous layer must play a crucial role in the evolution of the gas content in the galactic disk.  相似文献   

4.
We examine the dependence of the total hydrogen mass M HI in late-type star-forming galaxies on rotation velocity V rot and optical size D 25 or radial scale length R 0 of the disk for two samples of galaxies: (i) isolated galaxies (AMIGA) and (ii) galaxies with edge-on disks (flat galaxies according to Karachentsev et al.). M HI given in the HYPERLEDA database for flat galaxies have turned out to be, on average, overestimated by ~0.2 dex compared to isolated galaxies with similar V rot or D 25, which is apparently due to an overestimation of the self-absorption in the HI line. The hydrogen mass in the galaxies of both samples closely correlates with the total specific angular momentum of the galactic disk J, which is proportional to V rot D 25 or V rot R 0, with the low-surface-brightness galaxies lying along the common V rot R 0 sequence. We discuss the possibility of explaining the relationship between M HI and V rot D 25 by assuming that the gas mass in the disk is regulated by the marginal gravitational stability condition for the gas layer. Comparison of the observed and theoretically expected dependences leads us to conclude that either the gravitational stability corresponds to higher values of the Toomre parameter than is usually assumed, or the threshold stability condition formost galaxies was fulfilled only in the past, when the gasmass in the disks was a factor of 2–4 higher than that at present (except for the galaxies with an anomalously high observed HI content). The latter condition requires that for most galaxies the conversion of gas into stars be not compensated by the external accretion of gas onto the disk.  相似文献   

5.
We consider the problem of dust grain survival in the disk winds from T Tauri and Herbig Ae stars. For our analysis, we have chosen a disk wind model in which the gas component of the wind is heated through ambipolar diffusion to a temperature of ～104 K. We show that the heating of dust grains through their collisions with gas atoms is inefficient compared to their heating by stellar radiation and, hence, the grains survive even in the hot wind component. As a result, the disk wind can be opaque to the ultraviolet and optical stellar radiation and is capable of absorbing an appreciable fraction of it. Calculations show that the fraction of the wind-absorbed radiation for T Tauri stars can be from 20 to 40% of the total stellar luminosity at an accretion rate ? a = 10?8-10?6 M ⊙yr?1. This means that the disk winds from T Tauri stars can play the same role as the puffed-up inner rim in current accretion disk models. In Herbig Ae stars, the inner layers of the disk wind (r ≤ 0.5 AU) are dust-free, since the dust in this region sublimates under the effect of stellar radiation. Therefore, the fraction of the radiation absorbed by the disk wind in this case is considerably smaller and can be comparable to the effect from the puffed-up inner rim only at an accretion rate of the order of or higher than 10?6 M ⊙yr?1. Since the disk wind is structurally inhomogeneous, its optical depth toward the observer can be variable, which should be reflected in the photometric activity of young stars. For the same reason, moving shadows from gas and dust streams with a spiral-like shape can be observed in high-angular-resolution circumstellar disk images.  相似文献   

6.
We investigate the properties of an axisymmetric gas flow without angular momentum onto a small compact object, in particular, on a Schwarzschild black hole in the supersonic region; the velocity of the object itself is assumed to be low compared to the speed of sound at infinity. First of all, we show that the streamlines intersect (i.e., a caustic is formed) on the symmetry axis at a certain distance r x from the center on the front side if the pressure is ignored. The characteristic radial size of the region in which the streamlines emerging from the sonic surface at an angle no larger than θ0 to the axis intersect is Δr = r x θ 0 2 /3. To refine the flow structure in this region, we have numerically computed the system without ignoring the pressure in the adiabatic approximation. We have estimated the parameters of the inferred region with anomalously high matter temperature and density accompanied by anomalously high energy release.  相似文献   

7.
The dependence of the spin frequency derivative \(\dot \nu \) of accreting neutron stars with a strongmagnetic field (X-ray pulsars) on the mass accretion rate (bolometric luminosity, Lbol) has been investigated for eight transient pulsars in binary systems with Be stars. Using data from the Fermi/GBM and Swift/BAT telescopes, we have shown that for seven of the eight systems the dependence \(\dot \nu \) (Lbol) can be fitted by the model of angular momentum transfer through an accretion disk, which predicts the relation \(\dot \nu \) ～ L6/7bol. Hysteresis in the dependence \(\dot \nu \) (Lbol) has been confirmed in the system V 0332+53 and has been detected for the first time in the systems KS 1947+300, GRO J1008-57, and 1A 0535+26. Estimates for the radius of the neutron star magnetosphere in all of the investigated systems have been obtained. We show that this quantity varies from pulsar to pulsar and depends strongly on the analytical model and the estimates for the neutron star and binary system parameters.  相似文献   

8.
The paper argues in favor of the assumption that magnetic and non-magnetic protostars, from which CP stars were formed, are the objects that had rotation velocities of the parent cloud V smaller than a critical value V c . At V greater than the critical value, differential rotation emerges in the collapsing protostellar cloud, which twists magnetic lines of force into an’ invisible’ toroidal shape and disturbs the stability of the atmosphere. In magnetic protostars, the loss of angular momentum is due to magnetic braking, while in metallic protostars, the loss of rotation momentum occurs due to tidal interactions with a close component. HgMn stars are most likely not affected by some braking mechanism, but originated from the slowest protostellar rotators. The boundary of V c where the differential rotation occurs is not sharp. The slower the protostar rotates, the greater the probability of suppressing the differential rotation and the more likely the possibility of CP star birth.  相似文献   

9.
We analyze the spectra of DR Tau in the wavelength range 1200 to 3100 Å obtained with the GHRS and STIS spectrographs from the Hubble Space Telescope. The profiles for the C IV 1550 and He II 1640 emission lines and for the absorption features of some lines indicate that matter falls to the star at a velocity ～300 km s?1. At the same time, absorption features were detected in the blue wings of the N I, Mg I, Fe II, Mg II, C II, and Si II lines, suggesting mass outflow at a velocity up to 400 km s?1. The C II, Si II, and Al II intercombination lines exhibit symmetric profiles whose peaks have the same radial velocity as the star. This is also true for the emission features of the Fe II and H2 lines. We believe that stellar activity is attributable to disk accretion of circumstellar matter, with matter reaching the star mainly through the disk and the boundary layer. At the time of observations, the accretion luminosity was Lac ? 2L⊙ at an accretion rate ?10?7M⊙ yr?1. Concurrently, a small (<10%) fraction of matter falls to the star along magnetospheric magnetic field lines from a height ～R*. Within a region of size ?3.5R*, the disk atmosphere has a thickness ～0.1R* and a temperature ?1.5 × 104 K. We assume that disk rotation in this region significantly differs from Keplerian rotation. The molecular hydrogen lines are formed in the disk at a distance <1.4 AU from the star. Accretion is accompanied by mass outflow from the accretion-disk surface. In a region of size <10R*, the wind gas has a temperature ～7000 K, but at the same time, almost all iron is singly ionized by H I L α photons from inner disk regions. Where the warm-wind velocity reaches ?400 km s?1, the gas moves at an angle of no less than 30° to the disk plane. We found no evidence of regions with a temperature above 104 K in the wind and leave open the question of whether there is outflow in the H2 line formation region. According to our estimate, the star has the following set of parameters: M* ? 0.9M⊙, R* ? 1.8R⊙, L* ? 0.9L⊙, and \(A_V \simeq 0\mathop .\limits^m 9\). The inclination i of the disk axis to the line of sight cannot be very small; however, i≤60°.  相似文献   

10.
We calculate the parameters of the two-point correlation function of quasars w(r) = (r c /r) γ on the basis of the SDSS DR3 data. The correlation functions are first determined from projected distances with the use of a special technique for compiling randomized catalogs. Next the parameters of the spatial correlation function are obtained with the assumption of local isotropy. For the quasars with redshifts z = 0.8–2.1, we obtained the estimates γ = 1.76 ± 0.14, r c = 6.60 ± 0.85 h ?1 Mpc in the comoving distance range 2–30 Mpc and γ = 1.90 ± 0.11, r c = 6.95±0.57 h ?1 Mpc in the range 2–50 Mpc. These estimates agree, within the limits of errors, with the estimates obtained for the redshifts 0.4 < z < 2.1. The original catalog shows some deficit of pairs with separations less than 1 Mpc.  相似文献   

11.
In the UV spectra of BP Tau, GW Ori, T Tau, and RY Tau obtained with the Hubble Space Telescope, we detected an inflection near 2000 Å in the F λ c (λ) curve that describes the continuum energy distribution. The inflection probably stems from the fact that the UV continuum in these stars consists of two components: the emission from an optically thick gas with T<8000 K and the emission from a gas with a much higher temperature. The total luminosity of the hot component is much lower than that of the cool component, but the hot-gas radiation dominates at λ<1800 Å. Previously, other authors have drawn a similar conclusion for several young stars from low-resolution IUE spectra. However, we show that the short-wavelength continuum is determined from these spectra with large errors. We also show that, for three of the stars studied (BP Tau, GW Ori, and T Tau), the accretion-shock radiation cannot account for the observed dependence F λ c (λ) in the ultraviolet. We argue that more than 90% of the emission continuum in BP Tau at λ>2000 Å originates not in the accretion shock but in the inner accretion disk. Previously, a similar conclusion was reached for six more classical T Tau stars. Therefore, we believe that the high-temperature continuum can be associated with the radiation from the disk chromosphere. However, it may well be that the stellar chromosphere is its source.  相似文献   

12.
We consider an equation of state that leads to a first-order phase transition from the nucleon state to the quark state with a transition parameter λ>3/2 (λ=ρQ/(ρN+P0/c2)) in superdense nuclear matter. Our calculations of integrated parameters for superdense stars using this equation of state show that on the stable branch of the dependence of stellar mass on central pressure dM/dPc>0) in the range of low masses, a new local maximum with Mmax=0.082⊙ and R=1251 km appears after the formation of a toothlike kink (M=0.08M⊙, R=205 km) attributable to quark production. For such a star, the mass and radius of the quark core are Mcore=0.005M⊙ and Rcore=1.73 km, respectively. In the model under consideration, mass accretion can result in two successive transitions to a quark-core neutron star with energy release similar to a supernova explosion: initially, a low-mass star with a quark core is formed; the subsequent accretion leads to configurations with a radius of ～1000 km; and, finally, the second catastrophic restructuring gives rise to a star with a radius of ～100 km.  相似文献   

13.
The following conclusions about the kinematics and parameters of the gas in the vicinity of TW Hya have been drawn from an analysis of optical and ultraviolet line profiles and intensities. The accreting matter rises in the magnetosphere to a distance z>R* above the disk plane and falls to the star near its equator almost perpendicular to its plane. The matter outflows from a disk region with an outer radius of ≤0.5 AU. The [OI], [SII], and H2 lines originate in the disk atmosphere outside the outflow region, where the turbulent gas velocity is close to the local speed of sound. In the formation region of the forbidden lines, T?8500 K and Ne?5×106 cm?3, and the hydrogen is almost neutral: xe<0.03. The absorption features observed in the blue wings of some of the ultraviolet lines originate in the part of the wind that moves almost perpendicular to the disk plane, i.e., in the jet of TW Hya. The V z gas velocity component in the jet decreases with increasing distance from the jet axis from 200 to 30 km s?1. The matter outflowing from the inner disk boundary, moves perpendicular to the disk plane in the formation region of blue absorption line components, at a distance of ～0.5 AU from the axis of symmetry of the disk. This region of the wind is collimated into the jet at a distance of <3 AU from the disk plane. The gas temperature in the formation region of absorption components is ?2×104 K, and the gas density is <3×106 cm?3. This region of the jet is on the order of several AU away from the disk plane, while free recombination in the jet begins even farther from the disk. The mass-loss rate for TW Hya is \(\dot M_w < 7 \times 10^{ - 10} M_ \odot yr^{ - 1}\), which is a factor of 3lower than the mean accretion rate. The relative abundance of silicon and aluminum in the jet gas is at least an order of magnitude lower than its standard value.  相似文献   

14.
The superfine structure of the quasar 3C 273 has been investigated at wavelengths λ = 2 and 6 cm with angular resolutions up to φ = 20 μas for epochs 2005–2014. We have identified a nozzle and a bipolar outflow: a jet and a counterjet consisting of coaxial high- and low-velocity components. The separation between the nozzles in the plane of the sky is Δρ = 0.84 ± 0.16 pc; the flow ejection velocity is v ≤ 0.1c. The nozzle brightness temperature reaches T b ≈ 45 × 1012 K, φ = 20 μas, λ = 2 cm. The ejected electrons radiatively cool at a distance up to ≤4 pc. However, the jet afterglow is observed at a 8% level at a distance up to ρ ≈ 16 pc; the acceleration compensates for the radiative losses. The reduction in the emission level of the central flow at large distances determines the jet bifurcation. The counterjet shape is a mirror reflection of the initial part of the jet, suggesting a symmetry and identity of the ejected flows. The counterjet and jet nozzles are in the near and remote parts of the active region, respectively. The emission from the nozzles is absorbed by a factor of 2 and 15, respectively. The absorption decreases with increasing distance and the brightness of the jet fragments rises to its maximum at 0.5 pc from the nozzle. Arclike structures, arm fragments, are observed in the region of the nozzles. The relativistic plasma comes to the nozzles and is ejected. The brightness temperature of the arclike structures reaches 10% of the peak value, which is determined by the a smaller optical depth, the visibility in the transverse direction. The central high-velocity flow is surrounded by low-velocity components, hollow tubes being ejected as an excess angular momentum is accumulated. The remainder of the material flows along the arms toward the disk center until the next accumulation of an excess angular momentum and the process is repeated. The diameter of the outer nozzle is Ø = 25 pc and, further out, decreases exponentially; Ø n ≈ 80 exp(?1.15n) pc. The flow kinematics, collimation, and acceleration have a vortical nature. Ring currents producing magnetic fields, which accelerate and stabilize the processes, are generated in the rotating flows (tubes). The tangential directions of the currents are observed as parallel chains of components.  相似文献   

15.
Available velocity dispersion estimates for the old stellar population of galactic disks at galactocentric distances r?2L (where L is the photometric radial scale length of the disk) are used to determine the threshold local surface density of disks that are stable against gravitational perturbations. The mass of the disk Md calculated under the assumption of its marginal stability is compared with the total mass Mt and luminosity L B of the galaxy within r=4L. We corroborate the conclusion that a substantial fraction of the mass in galaxies is probably located in their dark halos. The ratio of the radial velocity dispersion to the circular velocity increases along the sequence of galactic color indices and decreases from the early to late morphological types. For most of the galaxies with large color indices (B–V)0>0.75, which mainly belong to the S0 type, the velocity dispersion exceeds significantly the threshold value required for the disk to be stable. The reverse situation is true for spiral galaxies: the ratios Md/LB for these agree well with those expected for evolving stellar systems with the observed color indices. This suggests that the disks of spiral galaxies underwent no significant dynamical heating after they reached a quasi-equilibrium stable state.  相似文献   

16.
We consider a spherically symmetric general relativistic perfect fluid in its comoving frame. It is found that, by integrating the local energy momentum conservation equation, a general form of g 00 can be obtained. During this study, we get a cue that an adiabatically evolving uniform density isolated sphere having ρ(r,t)=ρ 0(t), should comprise “dust” having p 0(t)=0; as recently suggested by Durgapal and Fuloria (J. Mod. Phys. 1:143, 2010) In fact, we offer here an independent proof to this effect. But much more importantly, we find that for the homogeneous and isotropic Friedmann-Robertson-Walker (FRW) metric having p(r,t)=p 0(t) and ρ(r,t)=ρ 0(t), \(g_{00} = e^{-2p_{0}/(p_{0} +\rho_{0})}\). But in general relativity (GR), one can choose an arbitrary t→t ?=f(t) without any loss of generality, and thus set g 00(t ?)=1. And since pressure is a scalar, this implies that p 0(t ?)=p 0(t)=0 in the Big-Bang model based on the FRW metric. This result gets confirmed by the fact the homogeneous dust metric having p(r,t)=p 0(t)=0 and ρ(r,t)=ρ 0(t) and the FRW metric are exactly identical. In other words, both the cases correspond to the same Einstein tensor \(G^{a}_{b}\) because they intrinsically have the same energy momentum tensor \(T^{a}_{b}=\operatorname {diag}[\rho_{0}(t), 0,0, 0]\).  相似文献   

17.
We have analyzed the Hubble Space Telescope spectrum of the young star FU Ori in the range 2300–3100 Å. The long-wavelength part of the spectrum is similar to the spectrum of a supergiant with T eff ? 5000–6000 K, but the range of wavelengths shorter than ?2600 Å is dominated by radiation from a region with T eff ? 9000 K. We discuss the possibility of explaining these peculiarities of the spectrum, the Al II] 2669.2 emission line profile, and the results of X-ray observations for FU Ori in terms of an accretion disk model whose thickness increases as the star is approached starting from distances ?1012 cm. Near the star, the disk has the shape of a cone in which only the part of its surface on the far (from the observer) side is visible. The suggested model is a kind of a compromise between the models of a thin α-disk and a supergiant: basically, this is an accretion model, but it resembles a supergiant in observational manifestations. Numerous absorption lines originating in the disk wind are superimposed on the disk spectrum. The wind is a cold (T ? 5000 K), dense (N e ? 1011 cm?3) gas. The number of wind absorption lines in the ultraviolet spectrum of FU Ori increases with decreasing wavelength. This causes a rapid decline in intensity in the short-wavelength part of the spectrum. As a result, the maximum temperature in the disk estimated from low-resolution IUE spectra has been underestimated.  相似文献   

18.
We give arguments for a basically unified formation mechanism of slow (Lynden-Bell) and fast (common) galactic bars. This mechanism is based on an instability that is akin to the well-known instability of radial orbits and is produced by the mutual attraction and alignment of precessing stellar orbits (so far, only the formation of slow bars has been explained in this way). We present a general theory of the low-frequency modes in a disk that consists of orbits precessing at different angular velocities. The problem of determining these modes is reduced to integral equations of moderately complex structure. The characteristic pattern angular velocities Ωp of the low-frequency modes are of the order of the mean orbital precession angular velocity \(\bar \Omega _{pr}\). Bar modes are also among the low-frequency modes; while \(\Omega _p \approx \bar \Omega _{pr}\) for slow bars, Ωp for fast bars can appreciably exceed even the maximum orbital precession angular velocity in the disk Ω pr max (however, it remains of the order of these precession angular velocities). The possibility of such an excess of Ωp over Ω pr max is associated with the effect of “repelling” orbits. The latter tend to move in a direction opposite to the direction in which they are pushed. We analyze the pattern of orbital precession in potentials typical of galactic disks. We note that the maximum radius of an “attracting” circular orbit rc can serve as a reasonable estimate of the bar length lb. Such an estimate is in good agreement with the available results of N-body simulations.  相似文献   

19.
A family of well behaved perfect fluid balls has been derived starting with the metric potential g 44=B(1+Cr 2) n for all positive integral values of n. For n≥4, the members of this family are seen to satisfy the various physical conditions e.g. c 2 ρ≥p≥0,dp/dr<0,dρ/dr<0, along with the velocity of sound \((\sqrt{dp/c^{2}d\rho} )< 1\) and the adiabatic index ((p+c 2 ρ)/p)(dp/(c 2 dρ))>1. Also the pressure, energy density, velocity of sound and ratio of pressure and energy density are of monotonically decreasing towards the pressure free interface (r=a). The fluid balls join smoothly with the Schwarzschild exterior model at r=a. The well behaved perfect fluid balls so obtained are utilised to construct the superdense star models with their surface density 2×1014  gm/cm3. We have found that the maximum mass of the fluid balls corresponding to various values of n are decreasing with the increasing values of n. Over all maximum mass for the whole family turns out to be 4.1848M Θ and the corresponding radius as 19.4144 km while the red shift at the centre and red shift at surface as Z 0=1.6459 and Z a =0.6538 respectively this all happens for n=4. It is interesting to note that for higher values of n viz n≥170, the physical data start merging with that of Kuchowicz superdense star models and hence the family of fluid models tends to the Kuchowicz fluid models as n→∞. Consequently the maximum mass of the family of solution can not be less than 1.6096 M Θ which is the maximum mass occupied by the Kuchowicz superdense ball. Hence each member of the family for n≥4 provides the astrophysical objects like White dwarfs, Quark star, typical neutron star.  相似文献   

20.
We investigate the combined effect of neutron and proton superfluidities on the cooling of neutron stars whose cores consist of nucleons and electrons. We consider the singlet state paring of protons and the triplet pairing of neutrons in the cores of neutron stars. The critical superfluid temperatures T c are assumed to depend on the matter density. We study two types of neutron pairing with different components of the total angular momentum of a Cooper pair along the quantization axis (|m J |=0 or 2). Our calculations are compared with the observations of thermal emission from isolated neutron stars. We show that the observations can be interpreted by using two classes of superfluidity models: (1) strong proton superfluidity with a maximum critical temperature in the stellar core T c max ?4×109 K and weak neutron superfluidity of any type (T c max ?2×108 K); (2) strong neutron superfluidity (pairing with m J =0) and weak proton superfluidity. The two types of models reflect an approximate symmetry with respect to an interchange of the critical neutron and proton pairing temperatures.  相似文献   

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