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A weak intra-day variability detected in blazar Mrk 421

ATel #5021; X. Liu (XAO), M.-Q. Lin (XAO/UCAS), J. Liu (XAO/UCAS), T. P. Krichbaum (MPIfR), L. Fuhrmann (MPIfR), N. Marchili (University of Padova)
on 27 Apr 2013; 12:26 UT
Credential Certification: Xiang Liu (liux@xao.ac.cn)

Subjects: Radio, Blazar

Following the reports of recent optical, X-ray and gamma activity of Mrk 421 (ATel #4983, ATel #4982, ATel #4978, ATel #4977, ATel #4976, ATel #4974, ATel #4918), we observed this blazar with the 25m radio telescope of the Xinjiang Astronomical Observatory, Chinese Academy of Sciences. Our result suggests an intra-day variability of the blazar at 4.8 GHz, with a modulation index (m defined by rms variability divided mean flux density) of 1.95+/-0.50 (%), and average flux density 0.781+/-0.015 (Jy). This variability index seems to be normal in the IDV amplitude compared with the results of our previous IDV observations of this blazar carried out in the past years, which could be induced by the interstellar scintillation, but its total (mean) flux density is higher than before: epoch | m(%) | mean S (Jy) | 2013.4.21-23 | 1.95+/-0.50 | 0.781+/-0.015 | 2009.3.21-25 | 1.62+/-0.42 | 0.594+/-0.010 | 2008.2.25-28 | 1.41+/-0.59 | 0.649+/-0.009 | 2007.6.15-18 | 2.65+/-0.55 | 0.645+/-0.017 | 2007.4.20-23 | 1.85+/-0.62 | 0.674+/-0.012 | 2007.3.24-27 | 1.29+/-0.46 | 0.693+/-0.009 | 2007.2.12-16 | 1.48+/-0.41 | 0.699+/-0.010 |