Time filter

Source Type

Yuan Y.,Guangzhou University | Yuan Y.,Astronomy Science and Technology Research Laboratory | Yuan Y.,Hefei University of Technology
Science China: Physics, Mechanics and Astronomy | Year: 2012

Based on the new data from the database of the University of Michigan Radio Astronomy Observatory (UMRAO), we analyze the spectral index and optical variability of OJ287 and 3C279. The main results show that 1) the time delay among three radio bands (4.8, 8, and 14.5 GHz) shows: τ 8-14.5 = 31 d, τ 4-8.8 = 41 d for OJ287, but no time delay lying in 3C279; 2) strong correlation lies in the polarization and flux density at 8 GHz for OJ287 and at 8, 14.5 GHz for 3C279; 3) the logarithmic brightness temperature log(T B) = 14.1 K for OJ287 is 14.1 K, log(T B) = 15.1 K for 3C279. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg. Source

Yuan Y.-H.,Hefei University of Technology | Yuan Y.-H.,Guangzhou University | Fan J.-H.,Hefei University of Technology | Fan J.-H.,Astronomy Science and Technology Research Laboratory
International Journal of Modern Physics D | Year: 2010

In this work, we used the preliminary data of University of Michigan Radio Astronomy Observatory (UMRAO) for the spectral index calculation for two blazars, 3C 273 (1226+023) and 3C 446 (2223-052), and found that the spectral indices are variable. Therefore, we used three methods (Jurkevich method (J), the discrete correlation analysis (D), and the Periodogram method (P)) to investigate the period in the spectral index variation curves. The results show that 3C 273 has a quasi-period of 8.8 ± 1.3 yr, and 3C 446 has a period of 5.8 ± 1.2 yr. © 2010 World Scientific Publishing Company. Source

Fan J.H.,Guangzhou University | Fan J.H.,Astronomy Science and Technology Research Laboratory
Journal of Astrophysics and Astronomy | Year: 2014

In this paper, we describe what we have done with regard to astronomy training for physics students. More and more students are interested in astronomy, they spend their summer holidays and spare time in observations and studying the observation data. Some students are familiar with using the telescope for observations, dealing with absorption line features achieved from the observations. Astronomy was selected as the key subject in Guangzhou city and Guangdong province, the laboratory for astronomy science and technology was selected as the key laboratory of Guangzhou city and that for the education department of Guangdong Province. We also provide a master degree programme for astronomy. © 2014, Indian Academy of Sciences. Source

Lin C.,Guangzhou University | Fan J.-H.,Astronomy Science and Technology Research Laboratory
Research in Astronomy and Astrophysics | Year: 2016

BL Lacertae objects (BL Lacs) are the dominant population of TeV emitting blazars. In this work, we investigate whether there are any special observational properties associated with TeV sources. To do so, we will compare the observational properties of TeV detected BL Lacs (TeV BLs) with non-TeV detected BL Lac objects (non-TeV BLs). From the 3rd Fermi/LAT source catalog (3FGL), we can obtain 662 BL Lacs, out of which 47 are TeV BLs and 615 are non-TeV BLs. Their multi-wavelength flux densities (F R, F O, F X and F γ), photon spectral indexes (αX ph and αph γ), and effective spectral indexes (αRO and αOX) are compiled from the available literature. Then the luminosities (log vL R, log vL O, log vL X, log vL γ) are calculated. From comparisons, we find that TeV BLs are different from low synchrotron peaked BLs and intermediate synchrotron peaked BLs, but TeV BLs show similar properties to high synchrotron peaked (HSP) BLs. Therefore, we concentrated on a comparison between TeV HSP BLs and non-TeV HSP BLs. Analysis results suggest that TeV HSP BLs and non-TeV HSP BLs exhibit some differences in their αRO and αγ ph, but their other properties are quite similar. © 2016 National Astronomical Observatories, Chinese Academy of Sciences and IOP Publishing Ltd. Source

Yuan Y.H.,Guangzhou University | Yuan Y.H.,Astronomy Science and Technology Research Laboratory | Fan J.H.,Guangzhou University | Fan J.H.,Astronomy Science and Technology Research Laboratory | Pan H.J.,Chinese Academy of Sciences
Astronomical Journal | Year: 2015

Using the 1.56 m telescope at Shanghai Observatory, China, we present the photometric results of 1ES 1959+650, which cover from 2006 June 11 to 2014 July 31. The maximum variabilities are DmV max = 1.74 ±0.02 ± mag in the V band, ΔmR max = 0.97 ±0.02 ± mag in the R band, and ΔmI max = 1.15 ±0.03 ± mag in the I band. During the monitoring period, we obtain intraday variabilities on 2009 September 2 (JD 2455077) and 2009 September 3 (JD 2455078). On 2009 September 2, the intraday variabilities are ΔmV = 0.36 ±0.08 mag within 1.56 hr, ΔmR= 0.21 ±0.04 mag within 23 minutes, and ΔmI = 0.53 ±0.03mag within 45 minutes. On 2009 September 3, the intraday variabilities are ΔmV = 0.40 ±0.10 mag within 27 minutes, ΔmR = 0.48 ±0.04 mag within 3.24 hr, and ΔmI = 0.68 ±0.06 mag within 3.72 hr. The two intraday variabilities occur in 24 hr, which may occur in the same variable phase. Other results show that (1) no quasi-periodicity is found in the longterm light curve and (2) the correlations between the brightness and the spectrum show obvious anti-correlation, a = -(0.18 ±0.02)FV + (2.33 ±0.12), with the correlation coefficient r = -0.74 and the chance probability p >0.01%. © 2015. The American Astronomical Society. All rights reserved. Source

Discover hidden collaborations