A search for electron cyclotron maser emission from compact binaries

• Published in: Monthly notices of the Royal Astronomical Society Vol. 382; no. 1; pp. 461 - 465
• Main Authors: Ramsay, Gavin, Brocksopp, Catherine, Wu, Kinwah, Slee, Bruce, Saxton, Curtis J.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 21-11-2007; Blackwell Science; Oxford University Press
• Subjects: Astronomy; Double stars; Earth, ocean, space; Exact sciences and technology; Magnetic fields; physical data and processes; planetary systems; Radio astronomy; stars: individual: ES Cet; stars: individual: GJ 876; stars: individual: RX J0806+15; stars: individual: RX J1914+14; Australia; planetary systems; stars: individual: RX J1914+14; stars: individual: GJ 876; physical data and processes; stars: individual: RX J0806+15; stars: individual: ES Cet; Circular polarization; Extrasolar planets; Planetary system; Data reduction; Radio emission; Alignment; Upper bound; Terrestrial planet; Masers; Positions; Models; Brightness temperature; Electron emission; Planet core; Magnetic fields
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2007.12393.x

Unipolar induction (UI) is a fundamental physical process, which occurs when a conducting body transverses a magnetic field. It has been suggested that UI is operating in RX J0806+15 and RX J1914+24, which are believed to be ultracompact binaries with orbital periods of 5.4 and 9.6 min, respectively. The UI model predicts that those two sources may be electron cyclotron maser sources at radio wavelengths. Other systems in which UI has been predicted to occur are short period extrasolar terrestrial planets with conducting cores. If UI is present, circularly polarized radio emission is predicted to be emitted. We have searched for this predicted radio emission from short period binaries using the Very Large Array (VLA) and Australian Telescope Compact Array (ATCA). In one epoch, we find evidence for a radio source, coincident in position with the optical position of RX J0806+15. Although we cannot completely exclude that this is a chance alignment between the position of RX J0806+15 and an artefact in the data reduction process, the fact that it was detected at a significance level of 5.8σ and found to be transient suggests that it is more likely that RX J0806+15 is a transient radio source. We find an upper limit on the degree of circular polarization to be ∼50 per cent. The inferred brightness temperature exceeds 1018 K, which is too high for any known incoherent process, but is consistent with maser emission and UI being the driving mechanism. We did not detect radio emission from ES Cet, RX J1914+24 or Gliese 876.