Follow-up Studies of Five Cataclysmic Variable Candidates Discovered by LAMOST

Abstract: We report follow-up observations of five cataclysmic variable candidates from LAMOST published by Hou et al. (2020). LAMOST J024048.51+195226.9 is the most unusual of the five; an early-M type secondary star contributes strongly to its spectrum, and its spectral and photometric behavior are strikingly reminiscent of the hitherto-unique propeller system AE Aqr. We confirm that a 7.34-hr period discovered in the Catalina survey data (Drake et al. 2014) is orbital. Another object, LAMOST J204305.95+341340.6 appears to be a near twin of the novalike variable V795 Her, with an orbital period in the so-called 2-3 hour "gap". LAMOST J035913.61+405035.0 is evidently an eclipsing, weakly-outbursting dwarf nova with a 5.48-hr period. Our spectrum of LAMOST J090150.09+375444.3 is dominated by a late-type secondary and shows weak, narrow Balmer emission moving in phase with the absorption lines, but at lower amplitude; we do not see the HeII 4686 emission evident in the published discovery spectrum. We again confirm that a period from the Catalina data, in this case 6.80 hr, is orbital. LAMOST J033940.98+414805.7 yields a radial-velocity period of 3.54 hr, and its spectrum appears to be typical of novalike variables in this period range. The spectroscopically-selected sample from LAMOST evidently includes some interesting cataclysmic variables that have been unrecognized until now, apparently because of the relatively modest range of their photometric variations.