Related papers: Spectral variability in faint high frequency peake…

We present Very Long Baseline Interferometry observations of a faint and low-luminosity ($L_{\rm 1.4 GHz} < 10^{27}~\mbox{W Hz}^{-1}$) Gigahertz-Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sample. We select eight sources from…

It is currently accepted that compact and bright radio sources characterized by a convex spectrum peaking at frequencies ranging from 100 MHz to a few GHz are young objects. In this scenario, high frequency peaker (HFP) radio sources, with…

We present a sample of sources with convex radio spectra peaking at frequencies above a few GHz, known as "High Frequency Peakers" (HFPs). A "bright" sample with a flux density limit of 300 mJy at 5 GHz has been presented by Dallacasa et…

We define a complete sample of thirty-three GHz-Peaked-Spectrum (GPS) radio sources based on their spectral properties. We present measurements of the radio spectra and polarization of the complete sample and a list of additional GPS…

It is currently accepted that intrinsically compact and bright radio sources characterized by a convex spectrum peaking at frequencies ranging from 100 MHz to a few GHz are young objects. Following the evolutionary models, these objects…

The knowledge of physical conditions in young radio sources is important for defining the framework of models describing radio source evolution. We investigate whether young radio sources are in equipartition (i.e. minimum energy)…

We propose a morphological classification based on the parsec scale structure of fifty-one High Frequency Peakers (HFPs) from the ``bright'' HFP sample. VLBA images at two adjacent frequencies (chosen among 8.4, 15.3, 22.2 and 43.2 GHz)…

There is quite a clear anticorrelation between the intrinsic peak frequency and the overall radio source size in Compact Steep Spectrum (CSS) and GHz Peaked Spectrum (GPS) radio sources as shown by O'Dea (1998). This feature is interpreted…

We present the data and analysis of VLBI observations at 1.6, 5 and 15 GHz of a sample of faint Gigahertz Peaked Spectrum (GPS) sources selected from the Westerbork Northern Sky Survey (WENSS). The 5 GHz observations involved a global array…

Up till now very few dying sources were known, presumably because the dying phase is short at centimeter wavelengths. We therefore have tried to improve the statistics on sources that have ceased to be active, or are intermittently active.…

We present multi-frequency radio data for a sample of narrow-line Seyfert 1 galaxies. We first focus on the sub-class of gamma-ray emitting narrow-line Seyfert 1 galaxies, studying the long-term radio variability of five sources and…

In this work, we study the optical properties of compact radio sources selected from the literature in order to determine the impact of the radio-jet in their circumnuclear environment. Our sample includes 58 Compact Steep Spectrum (CSS)…

We present the results of Karl G. Jansky Very Large Array (VLA) observations to study the properties of FR0 radio galaxies, the compact radio sources associated with early-type galaxies which represent the bulk of the local radio-loud AGN…

We present results from a radio survey for variable and transient sources on 15-min timescales, using the Australian SKA Pathfinder (ASKAP) pilot surveys. The pilot surveys consist of 505 h of observations conducted at around 1 GHz…

Radio activity has been observed in a large variety of stellar objects, including in the last few years, ultra-cool dwarfs. To explore the extent of long-term radio activity in ultra-cool dwarfs, we use data taken over an extended period of…

We use optical data from the Palomar Transient Factory (PTF) and the Catalina Real-Time Transient Survey (CRTS) to study the variability of gamma-ray detected and non-detected objects in a large population of active galactic nuclei (AGN)…

Compact Steep Spectrum, Gigahertz Peaked Spectrum and High Frequency Peak (CSS, GPS, HFP) sources are considered to be young radio sources but the details of their duty cycle are not well understood. In some cases they are thought to…

We present multi-frequency and high-resolution studies of a sample of 24 radio transients sources discovered by comparing the NRAO VLA Sky Survey (NVSS) and Very Large Array Sky Survey (VLASS) surveys. All of them are characterized by a…

We report on a blind survey for extragalactic radio variability that was carried out by comparing two epochs of data from the FIRST survey with a third epoch from a new 1.4 GHz survey of SDSS Stripe 82. The three epochs are spaced seven…

Peaked-spectrum (PS) sources, known for their distinct peaked radio spectra, represent a type of radio-loud active galactic nuclei (AGN). Among these, megahertz-peaked spectrum (MPS) sources, which exhibit a spectral peak at a frequency of…