The Magnetic Fields of Donor Stars in Magnetic Cataclysmic Variables
Abstract
During the last five years, we have obtained 195 hours of VLA radio observations to observe 165 magnetic cataclysmic variables (MCVs). We have detected radio emission from 29 MCVs, increasing the number of known sources by a factor of five (from 6 to 33). This larger sample of MCVs enables a statistical analysis of the number of MCVs versus orbital period, and demonstrates that rapidly-rotating (< 10 d) fully-convective dwarf stars emit strongly at radio frequencies (Barrett et al. 2018). This result is in conflict with the standard model of cataclysmic variable evolution where magnetic braking ceases below an orbital period of about 3 hours. Over two-thirds of the stars in our sample have orbital periods of less than three hours. This result implies that the donor stars in MCVs are magnetically more active below the period gap than above. We also note that ~75% of our radio detections show highly polarized emission that we attribute to electron cyclotron maser emission in a 2 - 8 kG magnetic field. The large percentage of highly polarized emission is in contrast to the early observations of MCVs by Chanmugam et al. (1983) and others that showed mostly unpolarized radio emission.
- Publication:
-
American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23333601B