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We study the circumstellar interaction around SN 1993J by its intermediate-band light curves obtained by the 60/90 cm Schmidt telescope at Xinglong station. The optical emission showed a slow decay of 0.05±0.02 mag/100 d in the period from 1995 to 2003, invoking a main energy contribution from SN-circumstellar interaction at late times. The relatively flat power law SN density model fits better with the observations. In particular, the line ratio of [O III]λλ4959, 5007 and Na I D relative to Hα are well reproduced by the model. Moreover, the Hα light curve displayed obvious bump structures at some epochs, which is probably attributed to the density fluctuations in the ambient material that surrounds the reverse shockwave.

Recently, the distances to type Ia supernova (SN Ia) at z~0.5 have been measured with the motivation of estimating cosmological parameters. However, different sleuthing techniques tend to give inconsistent measurements for SN Ia distances (~0.3 mag), which significantly affects the determination of cosmological parameters. A Bayesian ``hyper-parameter'' procedure is used to analyse jointly the current SN Ia data, which considers the relative weights of different datasets. For a flat Universe, the combining analysis yields ΩM = 0.20±0.07.

We present here some observed data on 11 mildly metal-poor stars with − 1.3 ≤ [Fe/H] ≤ −0.6. The model parameters and the abundances of 14 elements are determined. We also discuss the relation between the abundance ratio and the metallicity. The α elements (Mg, Si, Ca, Ti) are overabundant relative to Fe with a varying scatter at each given metallicity. Most of the iron-peak elements (V, Cr, Ni, Cu) are also overabundant relative to Fe by amounts that are independent of [Fe/H], while [Mn/Fe] increases with increasing metallicity. [Na/Al] is overabundant in the sample with [Fe/H]> −1.1 and definitely overdeficient in the sample with [Fe/H]

We modify Walecka's mean field method by regarding the nucleons as point sources when considering the vector meson field and obtain a new softer equation of state. Applying the latter to the structural equations of neutron stars gives a maximum mass of 1.7 M⊙ amd a rotational inertia of 1.62 × 1045gcm2. in good agreement with observations. The use of our improved mean field method reduces considerably the differences in the mass and rotational inertia given by relativistic and non-relativistic calculations.

We consider the effect on the adiabatic gravitational collapse of stellar cores of large mass due to (1) the use of different equations of state and (2) the inclusion of energy loss of shock. We find that different equations of state give very different central densities at rebounce and amplitudes of rebounce. When shock energy loss is not considered, all the equations discussed here will lead to explosions, but when it is considered, small amplitude rebounces will not do so.

We further discussed the Modified Mean Field Theory proposed in [1,2]. We found that this model has a new solution ml = 2; adding ϱ-meson, we calculated the symmetric energy of nuclear matter a4; with the new parameters we calculated the equations of state with and without the addition of ϱ-meson; we compared the two; we also compared with the results for ml = 4.3; we made a preliminary theoretical investigation of the form of the vector meson mean field using the two-body correlation function; lastly, using the structural equation of neutron star we calculated the maximum mass for the various equations of state. The results are: MMFT-2 (ml = 2): Mmax = 2.22M⊙ (without ϱ-meson) Mmax = 2.27M⊙ (with ϱ-meson) MMFT-1 (ml = 4.3): Mmax = 1.69M⊙ (without ϱ-meson) Mmax = 1.89M⊙ (with ϱ-meson)

To determine the accurate value of the Hubble constant Ho Is one of the most Important things of cosmology. Since 1929 the value has been revised from 550 km/s. Mpc to 50–100 km/s. Mpc.