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A broadband search for coherent emission in radio-cataclysmic variables

Margaret E. Ridder, Paul E. Barrett, Craig O. Heinke, Gregory R. Sivakoff

Abstract

Radio observations of cataclysmic variables have revealed a variety of behavior. From some systems, we see bright unpolarized radio flares occurring during dwarf nova outbursts, consistent with synchrotron emission from jets. In others, we see highly polarized emission, restricted in frequency, superimposed on a flat-spectrum continuum, suggesting a coherent emission process. Here, we present spectro-temporal analysis of 2--4 GHz and 8--12 GHz VLA observations of 6 cataclysmic variables. Our results show both broad- and narrow-band, highly polarized, variable radio emission. We suggest that this emission is consistent with electron-cyclotron maser emission or plasma radiation. This could be from an isolated emission region in the case of the narrow-band emission, or a region with varying magnetic field strength or density in the case of the broad-band emission. In one target, V2400 Oph, we see largely unpolarized emission changing on minute timescales, that may coincide with interactions between the white dwarf's magnetosphere and diamagnetic blobs.

A broadband search for coherent emission in radio-cataclysmic variables

Abstract

Radio observations of cataclysmic variables have revealed a variety of behavior. From some systems, we see bright unpolarized radio flares occurring during dwarf nova outbursts, consistent with synchrotron emission from jets. In others, we see highly polarized emission, restricted in frequency, superimposed on a flat-spectrum continuum, suggesting a coherent emission process. Here, we present spectro-temporal analysis of 2--4 GHz and 8--12 GHz VLA observations of 6 cataclysmic variables. Our results show both broad- and narrow-band, highly polarized, variable radio emission. We suggest that this emission is consistent with electron-cyclotron maser emission or plasma radiation. This could be from an isolated emission region in the case of the narrow-band emission, or a region with varying magnetic field strength or density in the case of the broad-band emission. In one target, V2400 Oph, we see largely unpolarized emission changing on minute timescales, that may coincide with interactions between the white dwarf's magnetosphere and diamagnetic blobs.
Paper Structure (11 sections, 2 equations, 10 figures, 7 tables)

This paper contains 11 sections, 2 equations, 10 figures, 7 tables.

Table of Contents

  1. Introduction
  2. Observations and analysis
  3. Results
  4. EF Eri
  5. UZ For
  6. ST LMi
  7. MR Ser
  8. V2400 Oph
  9. V603 Aql
  10. Discussion
  11. Conclusions

Figures (10)

  • Figure 1: The 8--12 GHz data for EF Eri on 2017 September 28 (left column) and 2017 October 2 (right column). The top panels show the full-band SEDs, the second panels show the full-band light curves, the third panels show the Stokes I dynamic SEDs, and the bottom panels show the Stokes V dynamic SEDs. One flare was detected in each 8--12 GHz observation of EF Eri. Both produced broadband LCP emission.
  • Figure 2: The 8--12 GHz data of UZ For on 2017 October 17 (left column) and 2017 October 19 (right column). The top panel shows the full-band SEDs, while the bottom panel shows the full-band light curves. There are neither clear flares nor circular polarization detected.
  • Figure 3: The 8--12 GHz data for ST LMi on 2017 November 1 (left column) and 2017 November 5 (right column). The top panels show the full-band SEDs, while the bottom panels show the full-band light curves. Detections of circular polarization are marginal, but there is an indication of increasing polarization with flux at the end of the first observation and the beginning of the first.
  • Figure 4: The 2--4 GHz data for ST LMi on 2025 March 23. The top panel shows the full-band SED, the second panel shows the full-band light curve, the third panel shows the Stokes I dynamic SED, and the bottom panel shows the Stokes V dynamic SED. There are two flares detected at the beginning and end of the observation that correspond with clear detections of LCP emission.
  • Figure 5: The 8--12 GHz data for MR Ser on 2017 October 11 (left column) and 2017 November 25 (right column). The top panels show the full-band SEDs, the second panels show the full-band light curves, the third panels show the Stokes I dynamic SEDs, and the bottom panels show the Stokes V dynamic SEDs. One flare was detection in the second observation, which was highly circularly polarized.
  • ...and 5 more figures