Conveners
Exploring the Cosmos: AGN-2: Parallel-12
- Lerothodi Leonard Leeuw (University of Johannesburg (ZA))
We present the results of twelve years of Fermi Large Area Telescope (LAT) monitoring observations of the high-energy peaked BL Lac object PG 1553+113. The Fermi-LAT (E>100 MeV) results are complemented by simultaneous, multi-wavelength data at lower energy bands, including the optical band. Our previous work published in 2015 revealed the presence of a ~2 years periodic modulation in the...
Blazars can show variability on a wide range of timescales. However, the search for periodicity in the gamma-ray emission of blazars remains an on-going challenge. This contribution will show the results obtained when a systematic pipeline is used to implement ten well-established methods for searching for periodicity. We analyze the most promising candidates selected from our previous work,...
Blazars are powered by super-massive black holes in their centers and are known for extreme variability on time scales from minutes to years. In case of a binary black hole system, this duality is traceable as periodic modulation of their gamma-ray emission. So far, high-significance periodicity has been reported for a very few blazars with standard approaches.
We developed a method to search...
The origin of the diffuse isotropic gamma-ray back- ground measured by the Fermi gamma-ray satellite at energies between 100 MeV and 820 GeV remains largely uncertain. Population studies indicate that most of the emission originates in a large number of extragalactic objects such as active galactic nuclei, star-forming galaxies, or radio galaxies too faint to be resolved as individual sources....
Powerful radio-galaxies feature heavily in our understanding of galaxy evolution. However, when it comes to studying their properties as a function of redshift and/or environment, the most-detailed studies tend to be limited by small-number statistics. In this talk, I will present a new sample of ~2,000 of the ‘brightest’ radio-sources in the southern sky (Dec. < 30 deg). These were observed...
We analyze the parsec-scale jet kinematics of a sample of gamma-ray bright blazars monitored roughly monthly with the Very Long Baseline Array at 43 GHz from 2007 to 2018. We implement a novel piece-wise linear fit to the trajectories of over 500 distinct emission features (knots) in the jets of 23 quasars, 12 BL Lacertae objects, and 3 radio galaxies. The apparent speeds range from < 1c to...
