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Short time-scale radio variations of compact extragalactic radio sources, known as IntraDay Variability, can be explained in at least some sources by a source-extrinsic effect, in which the variations are interpreted as scintillation of…

Short time-scale radio variations of compact extragalactic radio quasars and blazars known as IntraDay Variability (IDV) can be explained in at least some sources as a propagation effect; the variations are interpreted as scintillation of…

Intraday variability (IDV) of compact extragalactic radio sources is a complex phenomenon and shows a wavelength dependent mixture of refractive interstellar scintillation (RISS) (dominant at long cm-wavelengths) and source-intrinsic…

天体物理学 · 物理学 2007-05-23 Giuseppe Cimò , L. Fuhrmann , T. P. Krichbaum , T. Beckert , A. Kraus , A. Witzel , J. A. Zensus

The BLLac object S4 0954+65 is one of the main targets of the Urumqi monitoring program targeting IntraDay Variable (IDV) sources. Between August 2005 and December 2009, the source was included in 41 observing sessions, carried out at a…

高能天体物理现象 · 物理学 2015-06-04 N. Marchili , T. P. Krichbaum , X. Liu , H. G. Song , K. É. Gabányi , L. Fuhrmann , A. Witzel , J. A. Zensus

A sample of classical IntraDay Variable (IDV) and IDV candidate sources has been monitored with the Urumqi 25m telescope and the Effelsberg 100m telescope. Aim of the project is to investigate the origin of IntraDay Variability, a…

We summarize results from flux density monitoring campaigns performed with the 100 meter radio-telescope at Effelsberg and the VLA during the past 15 yrs. We briefly discuss some of the statistical properties of the rapid variability from…

天体物理学 · 物理学 2009-11-07 T. P. Krichbaum , A. Kraus , L. Fuhrmann , G. Cimo , A. Witzel

We report on the variability of 443 flat spectrum, compact radio sources monitored using the VLA for 3 days in 4 epochs at ~ 4 month intervals at 5 GHz as part of the Micro-Arcsecond Scintillation-Induced Variability (MASIV) survey. Over…

We aim to search for evidence of annual modulation in the time scales of the BL Lac object S5 0716+714. The intra-day variability (IDV) observations were carried out monthly from 2005 to 2009, with the Urumqi 25m radio telescope at 4.8 GHz.…

高能天体物理现象 · 物理学 2012-07-12 X. Liu , H. -G. Song , N. Marchili , B. -R. Liu , J. Liu , T. P. Krichbaum , L. Fuhrmann , J. A. Zensus

The intra-day variable source 0917+624 displays annual changes in its timescale of variability. This is explained in terms of a scintillation model in which changes in the variability timescale are due to changes in the relative velocity of…

天体物理学 · 物理学 2009-11-06 D. L. Jauncey , J. -P. Macquart

An in-depth analysis of variability has been carried out on the 2 GHz and 8 GHz light curves from the impressive database of the US Navy's extragalactic source monitoring program at the Green Bank Interferometer (GBI), complemented by UMRAO…

高能天体物理现象 · 物理学 2025-02-05 Nicola Marchili , Gunther Witzel , Margo F. Aller

Intraday Variability of compact extragalactic radio sources can be interpreted as quenched scintillation due to turbulent density fluctuations of the nearby ionized interstellar medium. We demonstrate that the statistical analysis of IDV…

天体物理学 · 物理学 2007-05-23 T. Beckert , L. Fuhrmann , G. Cimo , T. P. Krichbaum , A. Witzel , J. A. Zensus

There is new evidence which identifies seasonal changes of the variability time scale in intraday variable sources with refractive interstellar scintillation effects. Such a RISS-model takes the annual change of the Earth velocity relative…

天体物理学 · 物理学 2009-11-07 L. Fuhrmann , T. P. Krichbaum , G. Cimò , T. Beckert , A. Kraus , A. Witzel , J. A. Zensus , S. J. Qian , B. J. Rickett

The source J 1128+5925 was found recently to show strong intraday variability at radio wavelengths and its radio variability may come from interstellar scintillation. In optical, the object was quiet in our 2007 monitoring session. Here we…

星系天体物理 · 物理学 2009-11-13 Jianghua Wu , Xu Zhou , Jun Ma , Zhenyu Wu , Zhaoji Jiang , Jiansheng Chen

We have conducted the first systematic search for interday variability in a large sample of extragalactic radio sources at 15 GHz. From the sample of 1158 radio-selected blazars monitored over a $\sim$10 year span by the Owens Valley Radio…

Very recently, J 1128+5925 was found to show strong intraday variability at radio wavelengths and may be a new source with annual modulation of the timescale of its radio variability. Therefore, its radio variability can be best explained…

天体物理学 · 物理学 2008-11-26 Jianghua Wu , Xu Zhou , Jun Ma , Zhenyu Wu , Zhaoji Jiang , Jiansheng Chen

The search for compact components of strong ($S_{int} \ge 5$ Jy at 102.5 MHz) discrete radio sources from the Pushchino catalogue was carried out using the method of interplanetary scintillation. A total of 3620 sources were examined, and…

高能天体物理现象 · 物理学 2022-07-18 S. A. Tyul'bashev , I. V. Chashei , I. A. Subaev , M. A. Kitaeva

Radio variability on timescales from a few hours to several days in extragalactic flat-spectrum radio sources is generally classified as intra-day variability (IDV). The origin of this short term variability is still controversial and both…

天体物理学 · 物理学 2009-11-07 T. Beckert , T. P. Krichbaum , G. Cimo' , L. Fuhrmann , A. Kraus , A. Witzel , J. A. Zensus

Blazars from the first-three-months Fermi-AGN list were observed with the Urumqi 25m radio telescope at 5GHz in IDV (Intra-Day Variability) mode and inter-month observation mode. A significant correlation between the flux density at 5GHz…

宇宙学与河外天体物理 · 物理学 2015-05-27 X. Liu , Z. Ding , J. Liu , N. Marchili , T. P. Krichbaum

The search for long-term variability of compact components of radio sources B0821+394 and B1812+412 over an interval of 10 years was carried out. The LPA LPI radio telescope with an operating frequency of 111 MHz was used for observations.…

高能天体物理现象 · 物理学 2025-04-16 S. A. Tyul'bashev , I. V. Chashei , I. A. Grishanova , G. E. Tyul'basheva , I. A. Subaev

Variability of a galaxy's core radio source can be a significant consequence of AGN accretion. However, this variability has not been well studied, particularly at high radio frequencies. As such, we report on a campaign monitoring the high…

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