Rapidly variable circular polarization of HR 1099 at radio frequencies
We studied the very rapid variations in total flux density and circular polarization of HR 1099 at 2695 and 8085 MHz during the outburst of February 1978. From these observations we find the following. (1) The flux density and the activity (percent variation) at 8085 MHz are greater than at 2695 MHz: the radio spectrum has a positive slope, Sproportional..nu../sup ..cap alpha../ with ..cap alpha..>0. (2) Often the radio emission is circularly polarized at both frequencies, although the polarity may be different at the two frequencies. (3) The degree of circular polarization is generally greater at 2695 MHz than it is at 8085 MHz; we find the degree of polarization at 2695 MHz to be as high as approx.40%. (4) During active periods of several hours duration we see changes approx. factor of 2 in flux density at 2695 MHz that are wholly confined to one sense of circular polarization: the activity is altogether absent in the opposite polarity. (5) During two distinct epochs when the circular polarization at 2695 MHz was large, we find evidence for a characteristic sinusoidal modulation of the left circular flux density with a period of approx.4 min; this modulation appears to recur at intervals of 4.5--5.5 min. (6) Large degrees of circular polarization (> or approx. =10%) occur only when the phase of the HR 1099 binary system is near zero, that is, at conjunction with the more active component in front. These data support the conclusion that the radio emission is gyrosynchrotron radiation emitted by energetic electrons that are injected into an ordered magnetic field. The correlation of the degree of circular polarization with orbital phase when the source is active suggests that the magnetic field is a property of the binary system: it is shared by two stars.
- Research Organization:
- National Radio Astronomy Observatory, Green Bank, West Virginia 24944
- OSTI ID:
- 6658375
- Journal Information:
- Astron. J.; (United States), Journal Name: Astron. J.; (United States) Vol. 83:12; ISSN ANJOA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Coordinated ultraviolet, optical, and radio observations of HR 1099 and UX Arietis
Discovery of strong radio flaring from HR 1099