Detection of new sources of methanol emission at 107 and 108 GHz with the Mopra telescope     

I. E. Val'Tts  S. P. Ellingsen  V. I. Slysh  S. V. Kalenskii  R. Otrupcek  M. A. Voronkov 《Monthly notices of the Royal Astronomical Society》1999,310(4):1077-1086

A southern hemisphere survey of methanol emission sources in two millimetre-wave transitions has been carried out using the ATNF Mopra millimetre telescope. 16 emission sources have been detected in the 3₁–4₀ A⁺ transition of methanol at 107 GHz, including six new sources exhibiting class II methanol maser emission features. Combining these results with the similar northern hemisphere survey, a total of eleven 107-GHz methanol masers have been detected. A survey of the methanol emission in the 0₀–1₋₁ E transition at 108 GHz has resulted in the detection of 16 sources; one of them showing maser characteristics. This is the first methanol maser detected at 108 GHz, presumably of class II. The results of large velocity gradient statistical equilibrium calculations confirm the classification of these new sources as class II methanol masers.  相似文献   

UBV photometry, UV spectroscopy and radio observations of the peculiar binary V Sagittae     

J. J. Lockley  Janet H. Wood  S. P. S. Eyres  T. Naylor  Sergei Shugarov 《Monthly notices of the Royal Astronomical Society》1999,310(4):963-972

We have performed high-speed UBV photometric observations on the peculiar binary V Sagittae. Using three new eclipse timings we update the orbital ephemeris and convert it to a dynamical time-scale (TDB). We also searched for quasi-periodic oscillations but did not detect them. Using the Wilson–Devinney algorithm we have modelled the light curve to find the stellar parameters of V Sge. We find that the system is a detached binary but that the primary star is very close to filling its Roche lobe, while the secondary star fills 90 per cent of its Roche lobe volume. We find temperatures of the primary and the secondary star to be T ₁=41 000 K and T ₂=22 000 K. We find i =72° and masses of 0.8 M_⊙ and 3.3 M_⊙ for the primary and secondary stars respectively. De-archived Hubble Space Telescope ( HST ) spectroscopy of V Sge shows evidence of mass loss via a wind or winds. In addition we report radio observations of V Sge during an optical high state at 2 cm, 3.6 cm and 6 cm wavelengths. The 3.6 cm emission is increased by a factor of more than six compared with an earlier detection in a previous optical high state.  相似文献   

Results of VLBI monitoring of 3C273 at 22 GHz and 43 GHz     

F. Mantovani  W. Junor  C. Valerio  I. McHardy 《New Astronomy Reviews》1999,43(8-10)

The results of VLBI observations of the quasar 3C273, obtained during a multi-band campaign, are presented. The changes in separation from the core of the components along the first 2 mas of the jet were measured. The jet starts wiggling well inside the first parsec from the core. We derived the period of the oscillating jet path around the principal jet-axis in the range 2–8 mas from the core. The components' angular sizes, their peak fluxes, and turnover frequencies were also derived from the VLBI observations. We have derived lower limits to the Doppler factor by comparing the observed X-ray fluxes with those predicted by the synchrotron self-Compton model. Independent estimates were obtained through the assumption of energy equipartition between particles and magnetic field.  相似文献   

Observational Evidence for Solar Radio Microflares with Unusual Characteristics     

Xie R. X.  Wang M. 《天文研究与技术》1999,(Z1)

1　ＯｂｓｅｒｖａｔｉｏｎｓａｎｄＤａｔａＰｒｏｃｅｓｓｉｎｇ1 1　ＲａｄｉｏＯｂｓｅｒｖａｔｉｏｎｓＡｐａｒｔｉｃｕｌａｒｒａｄｉｏｍｉｃｒｏｆｌａｒｅｗａｓｏｂｓｅｒｖｅｄｄｕｒｉｎｇ 0 6 4 5～ 0 72 0ＵＴｏｎＪａｎｕａｒｙ 5 ,1 994ｂｙｔｈｅＹｕｎｎａｎＯｂｓｅｒｖａｔｏｒｙｈｉｇｈｔｉｍｅｒｅｓｏｌｕｔｉｏｎｓｏｌａｒｒａｄｉｏｔｅｌｅｓｃｏｐｅ .Ｉｔｏｃｃｕｒｒｅｄａｔ 1 42ＧＨｚｄｕｒ ｉｎｇａｓｍａｌｌ4Ｓ/Ｆｔｙｐｅｂｕｒｓｔ.Ｔｈｅｏｂｓｅｒｖａｔｉｏｎｗａｓａｌｓｏｍａｄｅｂｙｔｈ…  相似文献   

确定砂岩型铀矿矿化地段的铀、钍同位素证据   总被引：6，自引：1，他引：5  

刘金辉 《矿床地质》1999,18(3):262-267

根据铀、钍同位素地球化学基本原理,对新疆伊梨盆地５１２矿床含矿砂岩的Ｕ、Ｔｈ含量及其＾２３４Ｕ／＾２３８Ｕ、＾２３０Ｔｈ／＾２３２Ｔｈ进行了测试,并在此基础上对含矿砂岩的氧化带、还原带和氧化还原过渡带特征进行了研究。研究表明,与氧化带、还原带相比,氧化－还原过渡带具有较高Ｕ含量和＾２３４Ｕ／＾２３８Ｕ比值,较低Ｔｈ／Ｕ比值;矿石样品中的＾２３４Ｕ／＾２３８Ｕ、＾２３０Ｔｈ／＾２３８Ｕ比值位于过渡带  相似文献   

Temporal and spatial distribution of the magnetic field and density of nonthermal electrons in the source of solar microwave bursts     

Guang-Li Huang  Ai-Hua Zhou 《New Astronomy》2000,4(8):1806-599

The temporal and spatial distribution of the magnetic field and density of non-thermal electrons in the source of solar microwave bursts are studied by the gyrosynchrotron model, using the observations of the high-resolution spectrometer at the Owens Valley solar interferometer. The general results are consistent with the previous knowledge about these parameters. For example, the magnetic field decreases with increasing radio flux, and the distribution gradually flattens, so that the non-uniformity of the magnetic field decreases gradually, meanwhile the density increases, and the nonthermal electrons propagate from lower to higher levels. It is interesting that the oscillation of the density is detected at lower frequencies, and there is a correlation between the density and the energy index. The main purpose of this paper is to develop a diagnostic method for the basic plasma parameters in solar flares.  相似文献   

Low frequency radio emission from the &;#x2018;quiet&;#x2019; Sun     

R. Ramesh 《Journal of Astrophysics and Astronomy》2000,21(3-4):237-240

We present observations of the ‘quiet’ Sun close to the recent solar minimum (Cycle 22), with the Gauribidanur radioheliograph. Our main conclusion is that coronal streamers also influence the observed radio brightness temperature.  相似文献   

Intraday polarization variability outside the VLBI core of the active galactic nucleus 0716+714     

D. C. Gabuzda  P. YU. Kochenov  T. V. Cawthorne  R. I. Kollgaard 《Monthly notices of the Royal Astronomical Society》2000,313(3):627-636

Rapid ('intraday') cm-wavelength variations in both total and polarized flux density have been observed in a number of strong extragalactic radio sources. It is difficult to explain these variations purely as propagation effects, but if they are intrinsic to the sources, implausibly high brightness temperatures are required. We discuss here rapid polarization variability during our λ =6 cm global very long-baseline interferometry (VLBI) observations of the active galactic nucleus 0716+714. Measurements made with the Very Large Array (VLA) during the VLBI observations indicate a ≃50° swing in the position angle χ of the VLA core polarization in 12 hours. Corresponding variations were observed only for short VLBI baselines, so that they could not have occurred in the VLBI core (the only feature detected in our VLBI polarization map). The fact that the variations appear both in the VLA data and in the VLBI data for short baselines makes it difficult to explain them as instrumental effects. This leads us to conclude that the rapid variations occurred outside the area covered by our VLBI map; we estimate that the variability occurred in some compact feature roughly 25 milliarcseconds from the nucleus. It is clear that compact structures on a wide range of scales must be taken into account in studies of intraday variability in AGN.  相似文献   

太阳射电日像仪的进步与发展     

耿立红 《天文学进展》2000,18(2):91-103

叙述了太阳射电天文和太阳物理上作出过杰出贡献的几个射电日像仪的概况及其进步与发展,并简述了未来射电日像仪可以完成的科学目标以及应具有的特点,以期为在２１世纪我国实现“一颗空间Ｘ射线卫星、一座红外太阳塔和一台射电像仪”的宏伟构想提供研制依据。  相似文献   

Experimental Set-Up for Detecting Very Fast and Dispersed Millisecond Pulsars     

B. Rougeaux  G. Petit  T. Fayard  E. Davoust 《Experimental Astronomy》2000,10(4):473-485

We have developed observational and data processingtechniques for detecting millisecond pulsars. Themethod of data processing consists in correlating timeseries of data by folding them in two steps accordingto a trial period. While very time consuming,especially for very short periods, this methods allowsus in principle to detect very fast and dispersedmillisecond pulsars. The experimental set-up has beenintegrated into a data acquisition system developed atCentre national d'études spatiales (CNES).Observations of known millisecond pulsars atNançay radio observatory are used to validate thesystem and assess the sensitivity of the survey, whichis 3.5 mJy for 240 sec of integration. Futureimprovements in the radio-telescope and the systemshould bring it down to below 1 mJy. The applicationof the method to a millisecond pulsar survey is underway at Nançay radio observatory in collaborationbetween the Bureau international des poids et mesure(BIPM), Observatoire Midi-Pyrénées (OMP), and CNES.  相似文献