NOAO >   Observing Info >   Approved Programs >   2001B-0001

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Proposal Information for 2001B-0001


PI: Thomas E. Harrison, New Mexico State University, tharriso@nmsu.edu
Address: Box 30001/MSC4500, Las Cruces, New Mexico 88003, USA

CoI: Steve Howell, Planetary Science Institute
CoI: Dawn Gelino, New Mexico State University

Title: SQIID Observations of Magnetic CVs: Using Ellipsoidal Variations to Measure Orbital Inclinations

Abstract: We propose to use SQIID to obtain JHK light curves of several ``polars". Polars are cataclysmic variables where the white dwarf has a very strong magnetic field (>=10 MG) that directly channels the mass-accretion from the low-mass companion directly to the surface of the primary. As we have recently demonstrated for the polar AR UMa, JHK observations allow us to accurately determine the orbital inclination of such systems. In the infrared, the secondary star dominates the luminosities of these systems, and thus light-curve modeling allows us to accurately estimate the inclination angle. We need to know the orbital inclination angles for several reasons, the first is that it allows us to model the observed photometric and polarimetric behavior of these systems. Second, we can ascertain how the relative precession of the magnetic axis of the white dwarf, rarely aligned with the orbital poles, modulates the accretion processes. [In the case of AR UMa, we were even able to independently estimate the magnetic field strength of the white dwarf.] Finally, due to still unknown reasons, the accretion in these systems sometimes shuts down (or nearly so). At these times, the radial velocities (K_1, K_2) of both stellar components can be accurately measured. If K_1, K_2, and the orbital inclination are known, then the masses of both components can be determined. We request seven nights of time with SQIID on the 2.1 m to obtain JHK light curves, \it covering the entire orbital periods, of several polars.


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