Radio flux variations of the quasar J1159+2914 (S5 1156+295) in 2010–2013

Results of the observations of the blazar J1159+2914 (S1156+295) in 2010–2013 are reported. The observations were carried out on the RATAN-600 radio telescope (Special Astrophysical Observatory, Russian Academy of Sciences) at 4.85, 7.7, 11.1, and 21.7 GHz and the 32-m Zelenchuk and Badary radio telescopes of the Quasar-KVO Complex (Institute of Applied Astronomy, Russian Academy of Sciences) at 4.85 and 8.57 GHz. A flare peaked in August 2010, after which the flux density decreased monotonically at all studied frequencies. Variability on a timescale of 7 days was detected at 7.7 and 11.1 GHz near the flare maximum. The delay in the maximum at 7.7 GHz relative to the maximum at 11.1 GHz was 1.5 d, implying a Lorentz factor γ = 55 and angle of the jet to the line of sight θ ≈ 2° since mid-2011. Searches for intraday variability (IDV) were undertaken by the 32-m telescopes, mostly since mid-2011. Intraday variability was confidently detected only at the Badary station on November 10–11, 2012 at 4.85 GHz: the IDV timescale was τ _acf = 6 h, the modulation index was m = 1.4%, and the flux density of the variable component was S _var = 126 mJy.     

Rapid variability of the radio flux density of the blazar J0721+7120 (S5 0716+714) in 2010

Results of a study of the variability of the blazar J0721+7120 carried out on the RATAN-600 based on daily observations from March 5, 2010 to April 30, 2010 at five frequencies from 2.3 to 21.7 GHz are reported. In the same time interval, 13 observing sessions at 37 GHz were carried out on the 14-m radio telescope of the Mets?hovi Radio Astronomy Observatory of the Aalto University School of Technology (Finland). From March 19, 2010 to October 20, 2010, 16 daily sessions at 6.2 cm and five sessions at 3.5 cm were conducted on the 32-m radio telescope of the Zelenchukskaya Observatory (Quasar-KVO complex of the Institute of Applied Astronomy, Russian Academy of Sciences). A powerful flare was detected during the observations, with a time scale of approximately 20 days, derived from an analysis of the light curves and the structure and autocorrelation functions. The flare spectrum has been determined. In five sessions on the 32-m Zelenchukskaya telescope at 6.2 cm, intraday variability with time scales 8-16 h was detected; in four sessions, trends with time scales longer than a day were observed. In three sessions at 3.5 cm, intraday variability with a time scale of approximately 5 h was detected.     

Variability of the radio flux density of the Blazar S5 0716+714 on time scales less than a month

Results of a study of the variability of the BL Lac object S5 0716+714 are reported. The data were obtained in 150 daily observations on the RATAN-600 radio telescope at six frequencies from 0.97 to 21.7 GHz and 13 day-long sessions at a wavelength of 6.2 cm on the 32 m radio telescopes of the Zelenchukskaya, Svetloe, and Badary observatories (Quasar-KVO complex, Institute of Applied Astronomy, Russian Academy of Sciences). The RATAN-600 observations detected three “anti-flares,” or eclipses, when the flux density decreased from an initially constant level and then returned to this level. The eclipse time scales obtained from an analysis of light curves, structure functions, and autocorrelation functions are 12–20 days; the eclipse spectra were determined. Intraday variability (IDV) with time scales of 10–12 hours was detected in three sessions on the 32-m radio telescopes.     

Mapping the sun with the RTF-32 radio telescopes

The possibilities of using the RTF-32 radio telescopes of the interferometric QUASAR network for solar observations are investigated. A technique of solar radio mapping with the RTF-32 telescopes is presented. The software developed at the Institute of Applied Astronomy, Russian Academy of Sciences, for reducing such observations is described. The maps of the Sun at 1.35 cm, derived from observations at the Zelenchukskaya observatory November 4–14, 2004, are presented.     

Long-Term and Rapid Radio Variability of the Blazar 3C 454.3 in 2010–2017

The article presents the results of observations of the blazar 3C 454.3 (J2253+1608), obtained in 2010–2017 on the RATAN-600 radio telescope of the Special Astrophysical Observatory at 4.6, 8.2, 11.2, and 21.7 GHz and on the 32-m Zelenchuk and Badary radio telescopes of the Quasar VLBI Network of the Institute of Applied Astronomy at 4.84 and 8.57 GHz. Long-term variability of the radio emission is studied, as well as variability on time scales of several days and intraday variability (IDV). Two flares were observed in the long-term light curve, in 2010 and in 2015–2017. The flux density at 21.7 GHz increased by a factor of ten during these flares. The delay in the maximum of the first flare at 4.85 GHz relative to the maximum at 21.7 GHz was six months. The time scale for variability on the descending branch of the first flare at 21.7 GHz was τ_var = 1.2 yrs, yielding an upper limit on the linear size of the emitting region of 0.4 pc, corresponding to an angular size of 0.06 mas. The brightness temperature during the flare exceeded the Compton limit, implying a Doppler factor δ = 3.5, consistent with the known presence of a relativistic jet oriented close to the line of sight. No significant variability on time scales from several days to several weeks was found in five sets of daily observations carried out over 120 days. IDV was detected at 8.57 GHz on the 32-m telescopes in 30 of 61 successful observing sessions, with the presence of IDV correlated with the maxima of flares. The characteristic time scale for the IDV was from two to ten hours. A number of IDV light curves show the presence of a time delay in the maxima in the light curves for simultaneous observations carried out on the Badary and Zelenchuk antennas, which are widely separated in longitude. This demonstrates that the IDV most like arises in the interstellar medium.     

Variability of the Blazar J1504+1029 on Timescales from Hours to Years

The results of observations of the blazar J1504+1029 (PKS 1502+106, OR 103), obtained in 2000–2018 on the RATAN-600 radio telescope of the Special Astrophysical Observatory at 2.3, 3.9 (4.7), 7.7 (8.2), 11.2, and 21.7 GHz and on the 32-m Zelenchuk and Badary radio telescopes of the Quasar-KVO complex of the Institute of Applied Astronomy of the Russian Academy of Sciences at 5.05 and 8.63 GHz are presented. The long-term variability is studied, as well as variability on time scales from several days to several weeks and intraday variability (IDV). The long-term light curves are correlated at all frequencies and show continuous activity, against which three flares with their maxima in 2002, 2009, and 2018 are distinguished. The time scale for variability of the flare in 2009 is τ_var ≈ 1 year. At 21.7 GHz, the linear size of the emitting region is R ≤ 0.3 pc, its angular size is θ ≤ 0.05 mas, its brightness temperature is T_b ≥ 2 × 1014 K, and the Doppler factor is δ ≥ 5.8. The flare with its maximum in 2018 has a long rising branch at 21.7 GHz: τ_var = 3.2 years, linear size R ≤ 1.1 pc, angular size θ ≤ 0.17 μas, brightness temperature T_b ≥ 2.2 × 10¹² K, and Doppler factor δ ≥ 2.8. Among eleven sets of daily observations of the source over 75–120 days in 2000–2017, variability was detected in eight data sets at two to four frequencies with characteristic time scales of 4–30 days. In seven data sets, the variability is due to one to three cyclic processes with characteristic time scales τ_acf = 4?30^d. The spectral indices of the variable components in different years vary from α_var = ?1.6 to +1.8. In at least four data sets, the variability is due to processes in the source itself. In this case, at 21.7 GHz, the apparent linear size of the emitting region is ≤4000 AU, the angular size is θ ≤ 3.5 μas, the brightness temperature is T_b ≥ 3 × 10¹⁴ K, and the Doppler factor is δ ≥ 14. In the 2004 data set, the variability has an “ anti-flare” form, with the flux density of the variable component falling at high frequencies. Thirty-six successful sessions were conducted on the 32-m telescopes at 8.63 GHz, and 16 at 5.05 GHz. IDV was detected in 17 sessions at 8.63 GHz and in three sessions at 5.05 GHz, with the IDV being detected mainly near flare maxima.

     

Intraday variability of three flat-spectrum radio sources

Searches for intraday variability in the flat-spectrum radio sources J0527+0331, J0721+0406, and J1728+0427 have been carried out at 3.5 cm using the 32-m radio telescope of the Zelenchuk Observatory of the Kvazar-KVO complex of the Institute of Applied Astronomy of the Russian Academy of Sciences (located near the Zelenchuk Village, Karachaevo-Cherkesskaya Republic). Intraday variabiility with characteristic time scales from one to five hours was detected in all three sources.     

Investigation of the radio emission from active galactic nuclei: Determining the spin of a supermassive black hole

The results of radio observations for ten kinetically dominated quasars are presented. The observations have been performed at 3.5 cm with the RTF-32 radio telescopes at the Zelenchukskaya and Badary observatories of the Institute of Applied Astronomy of the Russian Academy of Sciences. The kinetic power of the relativistic jets and the spins of the supermassive black holes in these objects have been determined from radio luminosity measurements. The rotation of the black hole in these objects is shown to be retrograde with respect to the Keplerian rotation in the accretion disk in the case of an approximate equality between the magnetic and gas pressures near the black hole event horizon.     

Short variability of the radio flux density from the blazar J0530+1331

The results of observations of the quasar J0530+1331 (B0528+134) with the radio telescopes RATAN-600 at frequencies of 4.6, 8.2, 11.2, 21.7 GHz and RT-32 at the Zelenchukskaya and Badary observatories of the Quasar network of the Institute of Applied Astronomy, the Russian Academy of Sciences, at frequencies of 4.84 and 8.57 GHz in 2014–2015 are presented. A strong variability on a timescale of 20 days at 4.6–11.2 GHz has been detected over three months of daily RATAN-600 observations; the variability indices are V = dS/〈S〉; = 0.65?0.39. The spectrum of the variable component is falling toward high frequencies with an index α = ?0.76. The structure and autocorrelation functions at 4.6 GHz show an additional process on a timescale of 7 days. No delay of the main process has been detected between 11.2 and 8.2 GHz; the delay between 8.2 and 4.6 GHz does not exceed two days. The most likely cause of the observed variability is the scattering by inhomogeneities of the interstellar medium. The variability has been obtained at theminimum activity phase of the source. The intraday variability (IDV) has been searched for at both RT-32 telescopes since April 2014. Out of 38 successful observing sessions for the source, only three have shown a variability on a timescale of four hours or more at a significance level no higher than 0.1%. This confirms our conclusion drawn from the previous IDV measurements for other sources that the IDV is observed mainly at the maximum phases of long-term variability of the sources.