Search

Correlation between the polarizations in the near-infrared and optical wavebands is studied with simultaneous observational data of blazars. It is found that the degree and angle of polarization in the near-infrared are correlated strongly with those in the optical. And so are the radiation fluxes at the two wavebands. It follows that the near-infrared radiation and polarization of blazars are mainly from synchrotron radiation of relativistic electrons, and come from the same region as the optical waveband. Correlations between the three near-infrared color indices J-H, H-K and J-K are also studied using the 2MASS data. It is found that both J-H and H-K are strongly correlated with J-K, while there is no correlation between J-H and H-K. Lastly, we studied the color index magnitude relationship and found that the near-infrared spectrum gets flatter as the source gets brighter.

We monitored by photographic photometry the BL Lac object OJ 287 continuously during the 4-year period 1980–1984 and obtained the following results: (1) We confirm a previously proposed light variation on a time scale of about 8 days with an amplitude of 0.37 mag in B. (2) During the period 1980–1982, OJ 287 was stable and faint B = 15.61 mag at its faintest; while in March 1983, we observed an outburst (B = 14.25 mag). (3) Comparison star No. 9 given in Crain's handbook is probably a variable star. (4) A light curve based on all the published photographic data over the period 1968–1984 shows evidence for variations of large amplitudes (ΔB = 1.25–4.00 mag) over time scales of 2–4 years, in addition to the short term variation mentioned above.

We discuss, on the basis of general relativity, the density distribution of stars around a black hole at the centre of a globular cluster. We show that the radial density profile depends on the ratio of specific heats γ and the results by Peebles and by Bahcall and Wolf are particular cases with γ ⩽ 4 3 . We give also the projected density profiles, obtained by numerical integration, for ready comparison with observations.

UV-X-ray radiation has been observed in some synchrotron radio sources and some authors have suggested that both may originate in the “synchrotron self-Compton” effect. A number of relations between the synchrotron and the Compton spectra so produced are given in this paper which will provide criteria for testing the correctness of this effect and may also be useful in the evaluation of the physical parameters of the sources.

We give the results of two color (B and V) photometry of 4 BL Lac objects, OI 090.4, OF 038, 0109+22, and PKS 0735+178, obtained on 5 successive nights using the CCD system on the Yunnan 1-m RCC telescope.

Results of our wide beam radio observations of M87 are given here. Combined with the infrared observations of Virgo (Ceccarelli et al. 1982), we show that in order to explain both the radio and infrared observations, it is convenient to postulate an extended tepid (∼(+5) K ) halo, in addition to a hot (∼(+8) K ) halo surrounding M87. This tepid halo would be able to close the system gravitationally.

Typical coma spectra of Comet Halley were obtained on 1985 December 25 and 1986 January 13 using the 1 metre telescope of the Yunnan Observatory. The nitrogen-baked Kodak plates showed a continuum with strong molecular bands in emission. The intensity ratios are found to be CN(4216A) C 3 (4052A) = 1.03 , CN(4216A) C2(4365A) = 1.00 .

We discuss the radiative spectrum of the dust heated by Population III (very massive objects before the formation of galaxies), for the two cases of no Lyman cutoff and with Lyman cutoff. By numerical integration we find: (1) in the case of no Lyman cutoff, (little neutral hydrogen), the radiation from dust will be very strong, it will cause a distortion of 0.1–0.3 K around the peak of the cosmic background radiation and it will certainly be observed in the wavelength range between 100μ and 1000μm. (2) In the case of large neutral hydrogen abundance (hence Lyman cutoff), the radiation will be negligibly small compared to the cosmic background radiation. We suggest a search by balloon or satellite in the wavelength range between 200 μm and 1000μ to decide which case is the correct one.

We discuss the spectrum of dust heated by accretion disks of SMOs and the effect of the re-radiation on the cosmic muwave background. The main results are: (1) Whether or not there is Lymanalpha cutoff, the dust radiation in the case of SMOs is very strong and will appreciatively distort the muwave background. (2) In spite of (1), the dust radiation spectrum is different when Lyman-α cutoff is present and when it is absent (see Fig.2), and the two cases can be distinguished observationally. An infrared search in the range 200–900 μm would be useful in this connection.