Thomas E. Harrison

PHASE-RESOLVED INFRARED SPECTROSCOPY AND PHOTOMETRY OF V1500 CYGNI, AND A SEARCH FOR SIMILAR OLD CLASSICAL NOVAE

We present phase-resolved near-infrared photometry and spectroscopy of the classical nova (CN) V1500 Cyg to explore whether cyclotron emission is present in this system. While the spectroscopy do not indicate the presence of discrete cyclotron harmonic emission, the light curves suggest that a sizable fraction of its near-infrared fluxes are due to this component. The light curves of V1500 Cyg appear to remain dominated by emission from the heated face of the secondary star in this system. We have used infrared spectroscopy and photometry to search for other potential magnetic systems among old CNe. We have found that the infrared light curves of V1974 Cyg superficially resemble those of V1500 Cyg, suggesting a highly irradiated companion. The old novae V446 Her and QV Vul have light curves with large amplitude variations like those seen in polars, suggesting they might have magnetic primaries. We extract photometry for 79 old novae from the Two Micron All Sky Survey Point Source Catalog and use those data to derive the mean, un-reddened infrared colors of quiescent novae. We also extract WISE data for these objects and find that 45 of them were detected. Surprisingly, a number of these systems were detected in the WISE 22 ?m band. While two of those objects produced significant dust shells (V705 Cas and V445 Pup), the others did not. It appears that line emission from their ionized ejected shells is the most likely explanation for those detections.

Infrared Photometry and Spectroscopy of VY Aqr and EI Psc: Two Short-Period Cataclysmic Variables With Curious Secondary Stars

We present new K-band spectra of VY Aqr and EI Psc obtained with NIRSPEC on the Keck II telescope. We find a best-fitting spectral type of K4 for EI Psc, in agreement with the previous classification. The Keck spectrum of VY Aqr suggests an M0 spectral type, much hotter than previously derived. We re-reduce the original data for VY Aqr that were obtained using ISAAC on the Very Large Telescope (VLT) and find a best-fitting spectral type of M6 for VY Aqr. We are unable to reconcile the two data sets. We analyze new phase-resolved optical spectroscopy of VY Aqr, obtained using UVES on the VLT, to derive the mass ratio, and show that the mass of its secondary star is very likely below the stellar/substellar boundary. We also present and model phase-resolved JHK infrared light curves for both objects, and g- and I-band light curves for EI Psc. While the light curve models for EI Psc are consistent with its spectral type, we are unable to model the light curves of VY Aqr without assuming binary star parameters outside the published range for this object.

Herschel observations of Circinus X-1 during outburst and quiescence

We have used the Photodetector Array Camera and Spectrometer and Spectral and Photometric Imaging REceiver instruments on the Herschel Space Observatory to observe Cir X-1 both in and out of outburst. We detected Cir X-1 during outburst at 70 μm. Unfortunately, a cold background source dominates Cir X-1 at longer wavelengths. We have assembled optical and infrared (IR) data for Cir X-1 to model its spectral energy distribution (SED) in both quiescence and outburst and find that in both states it is consistent with a heavily reddened, 10,000 K blackbody. We believe this behavior is completely consistent with previous suggestions that these outbursts are due to accretion disk events, not unlike those of dwarf novae. To explore the behavior of other low-mass X-ray binaries with reported synchrotron jets, we have extracted and/or compiled optical and near- and mid-IR data sets for five such systems to construct their SEDs. The Z-source GX 349+2 and the black hole system GRS 1915+105 have strong and variable mid-IR excesses that suggest synchrotron emission. The other Z-sources have rather weak (or no) IR excesses that can be explained as reddened blackbody spectra with the addition of either synchrotron or bremsstrahlung components.