2001/10/23 by R. P. Fender, David Rayner, D. Rayner +7 · 2 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Cosmic Phenomena #Computational physics #Flare #Gamma-ray bursts and supernovae #Lag #Physics #Polarization (electrochemistry) #Radio frequency #Radio spectrum #Solar and Space Plasma Dynamics #Spectral index #Spectral line #Spectral shape analysis #Telecommunications #astro-ph
paper · pdf · doi:10.1046/j.1365-8711.2002.05072.x
published as Mon.Not.Roy.Astron.Soc. 330 (2002) 212 · Accepted for publication in MNRAS
arxiv created 2001/10/23 · openalex publication_date 2002/02/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We report high-sensitivity dual-frequency observations of radio oscillations from GRS 1915+105 following the decay of a major flare event in 2000 July. The oscillations are clearly observed at both frequencies, and the time-resolved spectral index traces the events between optically thin and thick states. While previously anticipated from sparse observations and simple theory, this is the first time a quasi-periodic signal has been seen in the radio spectrum, and is a clear demonstration that flat radio spectra can arise from the combination of emission from optically thick and thin regions. In addition, we measure the linear polarization of the oscillations, at both frequencies, at a level of about 1–2 per cent, with a flat spectrum. Cross-correlating the two light curves we find a mean delay, in the sense that the emission at 8640 MHz leads that at 4800 MHz, of around 600 s. Comparison with frequency-dependent time-delays reported in the literature reveals that this delay is variable between epochs. We briefly discuss possible origins for a varying time-delay, and suggest possible consequences.