• Xiang Liu

      Articles written in Journal of Astrophysics and Astronomy

    • Radio Observation of the 11-Month Fermi-AGN at Urumqi Observatory

      Zhen Ding Xiang Liu Jun Liu Lang Cui H. G. Song

      More Details Abstract Fulltext PDF

      We carry out flux observation at 5 GHz for 124 sources from the ‘clean’ sample of Fermi catalog 1LAC (The First LAT AGN Catalog) with Urumqi 25 m telescope. We find that it is obvious that there is a correlation between the 𝛾-ray and the radio flux density for blazars. For the subclasses, the correlation for FSRQs is strong, but the correlation for BL Lacs is weak.

    • Radio Observations of the S5 Sample

      Jun Liu Xiang Liu

      More Details Abstract Fulltext PDF

      The S5 sample was monitored on a monthly basis since December 2008 at Urumqi Observatory. Most of the sources are variables and a considerable proportion (about 20%) exhibited a significant inter-month flux variability (modulation index > 4%) during the 1-year observation.

    • Variability of GPS Radio Sources at 5 GHz

      Lang Cui Xiang Liu Jun Liu

      More Details Abstract Fulltext PDF

      We carry out flux monitoring on a sample of 169 Gigahertz Peaked Spectrum (GPS) radio sources at 5 GHz and find that about one-third of them show considerable Inter-Month Variability (IMV), and these IMV phenomena are likely to be caused by interstellar scintillation (ISS). Furthermore, we find that those showing IMV tend to be point-like or core-jet structures at VLBI scale.

    • Search for Binary Black Hole Candidates from the VLBI Images of AGNs

      Xiang Liu

      More Details Abstract Fulltext PDF

      We have searched the core-jet pairs in the VLBI scales (< 1 kpc), from several VLBI catalogues, and found out 5 possible Binary Black Hole (BBH) candidates. We present here the search results and analyse the candidates preliminarily. We plan to study with multi-band VLBI observation. We also plan to carry out optical line investigation in future.

    • Variability Study of the S5 Sample

      Jun Liu Lang Cui Xiang Liu Zhen Ding Hua-Gang Song

      More Details Abstract Fulltext PDF

      We present the results of flux density monitoring of the S5 sample at 5GHz with the Urumqi 25-m radio telescope during Dec. 2008 and Nov. 2009. Most sources exhibited > 2% rms variation in our one-year monitoring. Twenty-five highly variable sources were detected at a confidence level of 99%. Weaker sources show larger amplitude of variability. Sources that have a steep spectral index are not as variable in flux density as the flat spectrum objects. No galactic dependent variability was found. Supplemental IDV observations for several strong variables were performed in order to search for possible rapid variability, and to compare variability on different time-scales. The absence of short time-scale variability in S5 0633+73 indicates that mid time-scale variability is a main source of intrinsic origin.

    • 4.8 GHz Intra-Day Variability of FSRQ 0507+179

      Lang Cui Jun Liu Xiang Liu

      More Details Abstract Fulltext PDF

      As one of the targets of many flux monitoring campaigns, FSRQ 0507 + 179 shows various flux variation properties at almost all observing wavelengths, from radio to 𝛾-ray. With Urumqi 25-m telescope, our study on this object is focussed mainly on its radio flux variability, especially the Intra-Day Variability (IDV). We carried out a total of six epochs of IDV observations on 0507+179 at 4.8 GHz since March 2010, and found clearly IDV behaviours in all observing sessions and considered it is likely a type-I IDV source by analysing the characteristics and the timescales of the light curves. Additionally, we found 0507+179 exhibited some different IDV behaviours after an optical flare.

    • Position Angle Changes of Inner-Jets in a Sample of Blazars

      Ligong Mi Xiang Liu

      More Details Abstract Fulltext PDF

      We have carried out the Gaussian model-fitting to 15 GHz VLBAcores for a sample of blazars from the MOJAVE database, analysed the correlations in the model-fitted parameters and studied the variability properties for different group of sources. We found that the Fermi LAT-detected blazars have on an average higher position angle changes of cores than the non-LAT detected blazars, and that the LAT-detected ones are associated with more variable cores in flux density.

    • Recent Seven Years of Radio and Optical Variabilities of Quasar 1156+295

      Baorong Liu Xiang Liu

      More Details Abstract Fulltext PDF

      We analyzed the radio (4.8, 8.0 and 14.5 GHz) light curves from UMRAO database and the optical data of quasar 1156+295 and found that the quasar exhibited remarkable quasi-periodic long-term flux variations in both radio and optical bands with a similar variability timescale of 1.2 ± 0.3 yr. In addition, when a cross correlation analysis was adopted to the radio and optical light curves, we found that the optical variations may precede those of the radio e.g., at 14.5 GHz by ∼ 200 days.

  • Journal of Astrophysics and Astronomy | News

    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

© 2017-2019 Indian Academy of Sciences, Bengaluru.