The Detection of Discrete Cyclotron Emission Features in Phase-Resolved Optical Spectroscopy of V1500 Cygni

TL;DR

This study presents phase-resolved optical spectroscopy of V1500 Cygni, revealing discrete cyclotron emission features indicating strong magnetic fields, which suggest the system has reverted to a synchronous polar state, aligning optical, IR, and X-ray observations.

Contribution

The paper reports the first detection of discrete cyclotron humps from two magnetic field regions in V1500 Cyg, providing new insights into its magnetic field strengths and spin state.

Findings

Detected cyclotron humps indicating B=72 MG and B~105 MG

Reconciled optical/near-IR light curves with cyclotron emission

V1500 Cyg has likely reverted to a synchronous polar state

Abstract

We have obtained phase-resolved optical spectroscopy of the old nova, and asynchronous polar V1500 Cyg. These new data reveal discrete cyclotron humps from two different strength magnetic fields. One region has B = 72 MG, while the other has B ~ 105 MG. With the detection of these features, we revisit the optical/near-IR light curves presented in Harrison & Campbell (2016), and find that the large photometric excesses observed in those data are fully reconcilable with cyclotron emission. These results, when combined with the X-ray observations that appeared to have maxima that repeated on the orbital period, imply that V1500 Cyg has reverted back to a synchronous polar. Using existing theory, we show that the strong field strengths found here can explain the rapid spin down time.