Multi-Wavelength Observational Studies of Cataclysmic Variables

Steve performs observational research on interacting binaries, particularly cataclysmic variables, from the X-ray region to the mid-IR. He is a frequent GO on NASA's fleet of astrophysics satellites as well as observing at many of the worlds best ground-based observatories. Recent research has focused on high energy observations (X-ray and EUV) obtained simultaneously with IR observations at 1-5 microns. These have been used to map out the light distribution on the surface of the compact white dwarf primary star in AM Her systems and to understand the gas stream between the two stars.

As an example of recent work, we show below the first ever time-resolved spectroscopy of the secondary star in a cataclysmic variable. This data set is for the star ST LMi.


The two plots above show the first ever time-series spectroscopy in the IR of a cataclysmic variable. The numbers on the plot are the phase of the observation. These data are discussed in detail in Howell et al., 2000, ApJ., 20 Feb issue.

Using simultaneous IR and EUV observations, using the United Kingdom IR Telescope (UKIRT) located on mauna Kea in Hawaii and the NASA EUVE satellite, gas stream mapping is possible as a function of orbital phase, for magnetic systems. The figure here shows an example of such work for the binary star HU Aqr.


These plots show J and K lightcurves for the polar HU Aqr. The top curves are during a high state and the bottom curves are during a low state. Both sets of data show a double humped structure often assigned to ellipsoidal variations. The cosine-curve is a model fit based on ellipsoidal variations. Note that during the low state the fit is good but during a high state, the fit is poor. This indicates that low state observations are modulated by the light from the secondary but during the high state the apparent double humped structure is not caused by ellipsoidal variations.


EUV (70A) and IR (2.2 micron) simultaneous observations of the star HU Aqr. The two lightcurves show many common features. This indicates the the IR flux is highly modulated by the EUV emission from the system.