Computer Science
Scientific paper
May 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007sptz.prop40124h&link_type=abstract
Spitzer Proposal ID #40124
Computer Science
Scientific paper
Intermediate Polars are binary systems where a magnetic white dwarf accretes matter from a late-type, Roche lobe-filling secondary star. The standard model for IPs assumes that the magnetic field strength of the white dwarf is < 10 MG. If true, any cyclotron emission should occur in the mid-infrared region of the electromagnetic spectrum. In Cycle 2, we conducted a survey of IPs using the IRS on Spitzer and found no compelling evidence for the presence of cyclotron emission. We found that if cyclotron emission was occuring in the 5 to 14 micron bandpass, it constituted less that 0.5% of the bolometric luminosity of these systems (in the highly magnetic 'Polars', the cyclotron emission can rival the bolometric luminosity of the system!). We did, however, detect longer wavelength (> 14 micron) mid-infrared excesses for EX Hya and V1223 Sgr. These excesses are consistent with cyclotron emission from a 1 MG field. Unfortunately, the S/N of the LL2 data were poor, and we lacked the longer wavelength (LL1) observations that would clinch the case for such emission. As part of our IP survey, we extracted archival observations of AE Aqr and confirmed that its mid-infrared spectrum is dominated by optically thin synchrotron emission. It is reasonable to suggest that the LL2 detections of EX Hya and V1223 Sgr can be explained by such emission. With better LL2 data, and new LL1 observations, we will be able to determine whether the standard low field model for IPs is correct, or whether IPs are synchrotron sources. New, higher S/N data is requested for V603 Aql to determine whether it has an optically thin cyclotron emission feature at 8 microns, and whether it has a similar long wavelength excess. Our program requests 8.2 hours of Spitzer time.
Campbell Ryan
Cordova France
Harrison Thomas
Howell Steve
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