Investigation of flat spectrum radio sources by the interplanetary scintillation method at 111 MHz

¹ Pushchino Radio Astronomy Observatory, Pushchino, Moscow region 142290, Russia e-mail: serg@prao.psn.ru
² Isaac Newton Institute, Chile, Pushchino Branch, Russia
³ Universidade da Madeira, Centro de Ciências Matemáticas, Caminho da Penteada, 9000-390 Funchal, Portugal

Received: 5 August 2004
Accepted: 18 April 2005

Abstract

Interplanetary scintillation observations of 48 of the 55 Augusto et al. (1998) flat spectrum radio sources were carried out at 111 MHz using the interplanetary scintillation method on the Large Phased Array (LPA) in Russia. Due to the large size of the LPA beam (  ) a careful inspection of all possible confusion sources was made using extant large radio surveys: 37 of the 48 sources are not confused. We were able to estimate the scintillating flux densities of 13 sources, getting upper limits for the remaining 35. Gathering more or improving extant VLBI data on these sources might significantly improve our results. This proof-of-concept project tells us that compact (<) flat spectrum radio sources show strong enough scintillations at 111 MHz to establish/constrain their spectra (low-frequency end).