Search

Now showing items 1-10 of 98

The MicroArcsecond Scintillation-Induced Variability (MASIV) Survey: Detection of Angular Broadening at High Redshift?

Pursimo, T.; Ojha, R.; Jauncey, D.; Lovell, J.; Dutka, M.; Bignall, H.; Macquart, J.-P.; Rickett, B.; Kedziora-Chudczer, L. (Astronomical Society of the Pacific, 2008)

Interstellar scintillation has been shown to be primarily responsible for intra-day variability exhibited by extragalactic sources at centimeter wavelengths. The recent MASIV survey has shown that a very high proportion ...

The Second Realization of the International Celestial Reference Frame by Very Long Baseline Interferometry

Ojha, R.; et al. (International Earth Rotation and Reference Systems Service, 2009)

This Technical Note describes the generation by an international team of the second realization of the International Celestial Reference Frame (ICRF2) at radio wavelengths using nearly 30 years of Very Long Baseline ...

Ernie and Bert in the radio TANAMI blazars in the IceCube neutrino fields

Krauß, Felicia; Kadler, M.; Mannheim, K.; Wilms, J.; Ojha, R.; Kreikenbohm, A.; Langejahn, M.; Müller, C.; Schulz, R.; Trüstedt, J.

High-Resolution Observations of Centaurus A

Muller, Cornelia; Blanchard, J.; Bock, M.; Carpenter, B.; Dutka, M.; Furst, F.; Grafe, C.; Großberger, C.; Kadler, M.; Krauß, F.; Markowitz, A.; Ojha, R.; Perucho, M.; Pottschmidt, K.; Ros, E.; Rothschild, R.; Schulz, R.; Trustedt, J.; Wilms, J.; the TANAMI Collaboration (European Space Agency, 2011)

The closest active galaxy Centaurus A is regularly observed at milliarcsecond resolution within the framework of the Southern Hemisphere AGN monitoring program TANAMI. Additional multiwavelength observations up to gamma-ray ...

Gamma-ray emission in radio galaxies under the VLBI scope

Angioni, R.; Ros, E.; Kadler, M.; Ojha, R.; Müller, C.; Edwards, P. G.; Burd, P. R.; Carpenter, B.; Dutka, M. S.; Gulyaev, S.; Hase, H.; Horiuchi, S.; Krauß, F.; Lovell, J. E. J.; Natusch, T.; Phillips, C.; Plötz, C.; Quick, J. F. H.; Rösch, F.; Schulz, R.; Stevens, J.; Tzioumis, A. K.; Weston, S.; Wilms, J; Zensus, J. A. (EDP Sciences, 2019-06-19)

Aims. In the framework of the multi-wavelength and very long baseline interferometry (VLBI) monitoring program TANAMI (Tracking Active Nuclei with Austral Milliarcsecond Interferometry), we study the evolution of the ...

Multi-Physics of AGN Jets in the Multi-Messenger Era

Rani, B.; Petropoulou, M.; Zhang, H.; D'Ammando, F.; Finke, J.; Baring, M.; Böttcher, M.; Dimitrakoudis, S.; Gan, Z.; Giannios, D.; Hartmann, D. H.; Krichbaum, T. P.; Marscher, A. P.; Mastichiadis, A.; Nalewajko, K.; Ojha, R.; Paneque, D.; Shrader, C.; Sironi, L.; Tchekhovskoy, A.; Thompson, D. J.; Vlahakis, N.; Venters, T. M. (2019-03-11)

Active galactic nuclei (AGN) with relativistic jets, powered by gas accretion onto their central supermassive black hole (SMBH), are unique laboratories for studying the physics of matter and elementary particles in extreme ...

A gamma-ray determination of the Universe’s star formation history

Ojha, R.; et al. (American Association for the Advancement of Science, 2018-11-30)

The light emitted by all galaxies over the history of the Universe produces the extragalactic background light (EBL) at ultraviolet, optical, and infrared wavelengths. The EBL is a source of opacity for gamma rays via ...

High-Energy Polarimetry - a new window to probe extreme physics in AGN jets

Rani, B.; Zhang, H.; Hunter, S. D.; Kislat, F.; Böttcher, M.; McEnery, J. E.; Thompson, D. J.; Giannios, D.; Guo, F.; Li, H.; Baring, M.; Agudo, I.; Buson, S.; Petropoulou, M.; Pavlidou, V.; Angelakis, E.; Myserlis, I.; Wadiasingh, Z.; Silva, R. M. Curado da; Kilian, P.; Guiriec, S.; Bozhilov, V. V.; Hodgson, J.; Antón, S.; Kazanas, D.; Coppi, P.; Venters, T.; Longo, F.; Bottacini, E.; Ojha, R.; Zhang, B.; Ciprini, S.; Moiseev, A.; Shrader, C. (2019-03-11)

The constantly improving sensitivity of ground-based and space-borne observatories has made possible the detection of high-energy emission (X-rays and gamma-rays) from several thousands of extragalactic sources. Enormous ...

MASIV:The Microarcsecond Scintillation-Induced Variability Survey

Lovell, J.E.J.; Jauncey, D.L.; Senkbeil, C.; Shabala, S.; Bignall, H.E.; Pursimo, T.; Ojha, R.; Macquart, J.-P.; Rickett, B.J.; Dutka, M.; Kedziora-Chudczer, L. (Astronomical Society of the Pacific, 2007-01-21)

We are undertaking a large-scale 5 GHz VLA survey of the northern sky to search for rapid intra-day variability (IDV). Over four observing epochs we found that 56% of the sources showed variability on timescales of hours ...

Neutrinos, Cosmic Rays and the MeV Band

Ojha, R.; Zhang, H.; Kadler, M.; Neilson, N. K.; Kreter, M.; McEnery, J.; Buson, S.; Caputo, R.; Coppi, P.; D'Ammando, F.; Angelis, A. De; Fang, K.; Giannios, D.; Guiriec, S.; Guo, F.; Kopp, J.; Krauss, F.; Li, H.; Meyer, M.; Moiseev, A.; Petropoulou, M.; Prescod-Weinstein, C.; Rani, B.; Shrader, C.; Venters, T.; Wadiasingh, Z. (2019-03-13)

The possible association of the blazar TXS 0506+056 with a high-energy neutrino detected by IceCube holds the tantalizing potential to answer three astrophysical questions: 1. Where do high-energy neutrinos originate? 2. ...

1
2
3
4
. . .
10