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We studied the radio properties of optically selected quasars with z ≥ 3. The sample constructed with quasars having theflux densities S 1.4GHz ≥ 100 mJy at z ≥ 3 and S 1.4GHz ≥ 20 mJy at z ≥ 4. The observations were conducted in 2017–2021with the radio telescope RATAN-600. Using the multifrequency quasi-simultaneous data we revealed that a peaked spectralshape is a common feature for 50% of bright high-redshift quasars, the majority of them are radio-loud with log R > 2.5. Ourdata did not reveal any significant correlation between the redshift and spectral index. The average flux density variabilityof quasars are about V ar S = 0.2 − 1.0 at 4.7–11.2 GHz.

We present the results of pilot observations of the OH megamaser (OHM) sample carried out with the radio telescopeRATAN-600 at 1.2, 2.3, 4.7, 8.2, 11.2, and 22.3 GHz in 2019–2021. When comparing the radio continuum properties ofthe OHM sample and the control sample of galaxies without detected maser emission, we determine the median spectralindex at 4.7 GHz α 4.7 = −0.59 for the OHM sample, and α 4.7 = −0.71 for the non-OHM galaxies, and steep radiospectra prevail in both samples. Subsamples of OHMs powered by active galactic nuclei (AGN) and star formation have nosignificant differences in their radio properties. AGN-powered galaxies exhibit larger scatter in a range of parameters andtheir standard deviations.

We report observations of a transient source \fermi\ from radio to \grs. \fermi\ was discovered by the {\it Fermi-LAT} in May 2017. Follow-up {\it Swift-XRT} observations revealed three flaring episodes through March 2018, and the peak X-ray flux is about $10^3$ higher than the {\it ROSAT all-sky survey (RASS)} flux upper limit. Optical spectral measurements taken by the {\it Magellan 6.5-m telescope} and the {\it Lick-Shane telescope} both show a largely featureless spectrum, strengthening the BL Lac interpretation first proposed by \citet{Bruni18}. The optical and mid-infrared (MIR) emission goes to a higher state in 2018, when the flux in high energies goes down to a lower level. Our {\it RATAN-600m} measurements at 4.8~GHz and 8.2~GHz do not indicate any significant radio flux variation over the monitoring seasons in 2017 and 2018, nor deviate from the archival {\it NVSS} flux level. During GeV flaring times, the spectrum is very hard ($\Gamma_\gamma\sim$1.7) in the GeV band and at times also very hard (($\Gamma_{\rm X}\lesssim2$) in the X-rays, similar to a high-synchrotron-peak (or even an extreme) BL Lac object, making \fermi\ a good target for ground-based {\it Cherenkov telescopes}., Comment: Submitted in Journal of High Energy Astrophysics