A New Window for Studying Intermediate Polars and Tilted Accretion Disk Precession

Abstract

TV Col is a long-period eclipsing intermediate polar (IP) prototype star for the negative superhump (NSH) system. We investigate the eclipse minima, eclipse depth, and NSH amplitude based on TESS photometry. Using the same analytical method as for SDSS J081256.85+191157.8, we find periodic variations of O − C for eclipse minima and NSH amplitudes with periods of 3.939(25) days and 3.907(30) days, respectively. The periodic variation of the NSH amplitude of TV Col confirms that periodic changes in NSH amplitude in response to the tilted disk precession may be universal, which is further evidence that the origin of the NSHs is related to the tilted disk precession. We suggest that the variation in NSH amplitude may be similar to the superorbital signal, coming from the periodic change in visual brightness of the energy released by streams touching the tilted disk with tilted disk precession. Finally, we find for the first time that the eclipse depth exhibits biperiodic variations with periods of P _1 = 3.905(11) days and P _2 = 1.953(4) days, respectively. P _2 is about half of P _1 and the disk precession period ( P _1 ≈ P _prec ≈ 2 × P _2 ). We suggest that P _1 may come from the periodic change in the brightness of the eclipse center due to tilted disk precession, while P _2 may come from two accretion curtains precessing together with the tilted disk, but more verification and discussion are necessary. The discovery of biperiodic variations in eclipse depth provides a new window for studying IPs and tilted disk precession.

Keywords

• Binary stars
• Cataclysmic variable stars
• DQ Herculis stars