1. Variability study of flat-spectrum radio sources sample at the RATAN-600 Sotnikova Yu.V., Erkenov A.K.

2. ● The aim: to study variations of radio emission of AGNs on time scales from days to 8 years to determine characteristics of their variability. The paper presents results of observations of compact radio sources with flat spectra near the Celestial North Pole (75° ≤ δ ≤ 88°) ● All observations of sources were carried out with the radio telescope RATAN-600 (21.7, 11.2, 7.7, 4.8, 2.3 and 1.1 GHz) during several observational sessions in the period 1999-2007. The main task was to obtain simultaneous multi-frequency spectra and spectral characteristics of compact radio sources in the near-polar region of the celestial sphere.

3. OBSERVATIONS 1. 1999, 182 sources S NVSS ≥ 400 mJy, 75° ≤ Decl ≤ 88°. The work was provoked by a necessity to take account of discrete radio sources in the study of background. 2. 2005, 504 sources, S NVSS ≥ 200 mJy, 75° ≤ Decl ≤ 88°. This resulted in detection of 51 sources with flat spectra. 3. October 2006, April and September 2007, separate objects of the sample with flat spectra were observed additionally. 4. August 2007, 33 objects of the list under investigation were observed during 30 days daily.

4. NAXIS1=7080 CTYPE1=TIME CRVAL1=7051.683 CRPIX1=1 CDELT1=0.1 BSCALE=0.4571429 BZERO=0 OBJECT=0203+81 DATE-OBS=25/07/07 LAMBDA=0.027 TM-END=7759.683 TTYPE1=CHANNEL 2 OBSRA=2.06725253333333 OBSDEC=81.13616 AZIMUTH=180 ELEVAT=52.709923 ELEV-AN=52.709923 ELEV-SH=0 EPOCH=2000 RA=2.05216666666667 DEC=81.103528 NUT-RA=4.263864e-01 CMPRS-CF=1 NOISE-T=4.8 CALIBR1=11 CALIBR2=10 FAST VARIABILITY 2007.07.27 23:21:29 '7725r 7280021.r 1937+83 Marat': Start 2007.07.27 23:21:47 Failures: 174A 86.8 251.0 Fail: Nmov 2007.07.27 23:22:20 '7725r 7280021.r 1937+83 Marat': Stop 2007.07.28 0:37:43 '7725r 7280053.r 2005+77 Marat': Start 2007.07.28 0:37:55 Failures: 174A 86.8 251.0 Fail: Nmov 2007.07.28 0:42:10 '7725r 7280053.r 2005+77 Marat': Stop 2007.07.28 1:01:22 '7725r 7280112.r 2022+76 Marat': Start 2007.07.28 1:03:04 '7725r 7280112.r 2022+76 Marat': Stop an output file-protocol of the condition of antenna surfaces state format of the output file with observant data

5. name 1.38 cm2.7 сm3.9 cm6.3 cm relative errors of antenna temperature [%] 0410+761.10.170.210.33 0410+76 cor1.10.160.200.30 0016+794.60.510.240.36 0016+79 cor4.50.510.220.36 2344+826.40.610.260.47 2344+82 cor6.40.600.250.45 Relative errors of antenna temperature of reference sources averaged over the observational cycle, before and after introduction of corrections for the antenna surface state (the correction was calculated by Lena Majorova)

6. Long-term variability (1999-2007) Var ΔS = (Smax–Smin)/Smin

7. Approximate classification 20 sources – flat spectra which can be described by a power law, with 0 ≥ α ≥ -0.5 mainly Galaxies 5 sources with peaked spectra (candidates in GPS) Quasars – core/core-jet Galaxies – compact symmetrical structure

8. http://lacerta.gsfc.nasa.gov/vlbi/images/

10. 9 sources with complex or powerfully changing shape 9 sources with complex or powerfully changing shape Varied VLBI-morphology Varied VLBI-morphology Approximate classification 17 sources with rising spectra mainly Quasars - core

11. The statistical analysis of fast variability of the obtained data was based on methods described in [Quirrenbach A. 2000]: - we used the modulation index m, which is related to the mean antenna temperature end their standard deviation - as a criterion whether a source is variable or not, we perform a test - the variability amplitude for the variable sources, where m 0 – is the modulation index of a non-variable sources (reference sources). But our statistical analysis differs a little bit from classical one… 55 minutes for Decl=88º … 0410+76 0016+79 2344+82

12. “Light curves” of the selected reference sources and (lower) relation between the modulation index and declination of a source.

13. Results

15. Conclusions 1. It was obtained simultaneous multi-frequency radio spectra of objects (from flux- density full sample ) of near-polar region at several epochs (1999, 2005, 2006, 2007). 2. As a result of statistical analyze 15 objects were detected with presence of variability of radio emission on scales of days and more (in system of the observer) at frequencies 21.7, 11.2, 7.7 and 4.8 GHz. Most of them are quasars. The variability amplitude of these sources is not above 7%. Four sources from them (J0626+8202, J1153+8058, J1800+7828, J2005+7752 ) are already known as fast-variations sources [D.S. Heeschen 1987; A. Quirrenbash 2001; A. Kraus 2003]. 3. On the results of statistical analyze both objects with significant long-term variability and ones without long-term variability show presence of variability of radiation at the time scales on days and more. For example, three radio sources with peaked spectrum, were earlier candidates in GPS-sources J0626+82, J0726+79 and J1044+80. 4. More than half of sources with rapid variability demonstrate the rise of the variability amplitude with the frequency. ______________________________________________________________________ Publications: 1. 1. Mingaliev M.G., et al., Astron. J., 2007, 84, N5, 1-22. 2. 2. Mingaliev M.G., et al., Astron. J., 2008, in prepare.

16. THE END

17. References S.J. Tingay, D.L. Launcey, E.A. King, et al., PASJ, 55, 351 (2003).