Ryan K. Campbell

GALEX, Optical, and Infrared Light Curves of MQ Dra: UV Excesses at Low Accretion Rates

Ultraviolet light curves constructed from near-ultraviolet (NUV) and far-ultraviolet (FUV) detectors on GALEX reveal large-amplitude variations during the orbital period of the low accretion rate polar MQ Dra (SDSS J1553+55). This unexpected variation from a UV source is similar to that seen and discussed in the polar EF Eri during its low state of accretion, even though the accretion rate in MQ Dra is an order of magnitude lower than even the low state of EF Eri. The similarity in phasing of the UV and optical light curves in MQ Dra imply a similar location for the source of light. We explore the possibilities of hot spots and cyclotron emission with simple models fit to the UV, optical, and IR light curves of MQ Dra. To match the GALEX light curves with a single-temperature circular hot spot requires different sizes of spots for the NUV and FUV, while a cyclotron model that can produce the optical harmonics with a magnetic field near 60 MG requires multipoles with fields >200 MG to match the UV fluxes.

CYCLOTRON MODELING PHASE-RESOLVED INFRARED SPECTROSCOPY OF POLARS. II. EQ CETI, AN URSA MAJORIS, AND VV PUPPIS

We present phase-resolved low-resolution infrared spectra of the polars EQ Cet, AN UMa, and VV Pup obtained with SPEX on the IRTF. In addition, we supplement our IRTF observations for VV Pup with optical data sets. The infrared spectra cover the wavelength range 0.8 μ m ≤ λ ≤ 2.4 μm and show cyclotron emission at all orbital phases for the three objects. We use a constant-lambda prescription to attempt to model the changing cyclotron features seen in the spectra. We model the EQ Cet data using two different approaches, yielding final parameters of B 34.0 MG, kT 3.5 keV, and log Λ 4.1. For AN UMa we find orbitally averaged models of B = 32.1 MG, kT = 5.0 keV, and log Λ 4.3. We modeled phase-resolved spectra for VV Pup at four different epochs. We find the following range in parameters: 30.0 MG ≤ B≤ 31.9 MG, 4.0 keV ≤ kT ≤ 15.0 keV, and 3.7 ≤ log Λ ≤ 6.5. Finally, we find that in B-kT space, the four epochs are well separated based on the visual brightness of the system at the time of observation.

The detection of discrete cyclotron emission features in phase-resolved optical spectroscopy of V1500 Cygni

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.

Unravelling the source of UV emission in EF Eridani

Oribital phase‐resolved spectra of EF Eri were obtained with the Solar Blind Channel on the Hubble Space Telescope during its low state. The specta peaked at 1500 and 1700 A, and the integrated UV light curves displayed quasi‐sinusoidal modulations. WD hotspot and cyclotron emission models were computed in an attempt to fit the spectroscopic morphology throughout the orbit.