CHARACTERIZING THREE CANDIDATE MAGNETIC CATACLYSMIC VARIABLES FROM SDSS: XMM-NEWTON AND OPTICAL FOLLOW-UP OBSERVATIONS1

In the latest in our series of papers on XMM-Newton and ground-based optical follow-up of new candidate mag-netic cataclysmic variables (mCVs) found in the Sloan Digital Sky Survey, we report classifications of three systems: SDSS J144659.95+025330.3, SDSS J205017.84053626.8, and SDSS J210131.26+105251.5. Both the X-ray and optical fluxes of SDSS J1446+02 are modulated on a period of 48:7 0:5minutes, with the X-raymodulation show-ing the characteristic energy dependence of photoelectric absorption seen in many intermediate polars (IP). A longer period modulation and radial velocity variation is also seen at around 4 hr, although neither data set is long enough to constrain this longer, likely orbital, period well. SDSS J205005 appears to be an example of the most highly magnetized class of mCV, a diskless, stream-fed polar. Its 1.57 hr orbital period is well constrained via optical eclipse timings; in the X-ray it shows both eclipses and an underlying strong, smooth modulation. In this case broadly phase-resolved spectral fits indicate that this change in flux is the result of a varying normalization of the dominant com-ponent (a 41 keV MEKAL plasma), plus the addition of a partial covering absorber during the lower flux interval. SDSS J2101+10 is a more perplexing system to categorize: its X-ray and optical fluxes exhibit no large periodic modulations; there are only barely detectable changes in the velocity structure of its optical emission lines; the X-ray spectra require only absorption by the interstellar medium; and the temperatures of the MEKAL fits are low, with maximum temperature components of either 10 or 25 keV. We conclude that SDSS J2101+10 cannot be an IP, nor likely a polar, but is rather most likely a disk accretor—a low-inclination SW Sex star. Key words: novae, cataclysmic variables — stars: individual (SDSS J144659.95+025330.3, SDSS J205017.84053626.8, SDSS J210131.26+105251.5) — stars: magnetic fields — X-rays: stars Online material: color figure