tokens: takes place in TX Col (see Buckley Tuohy 1989 ; Norton et al. 1997 ; Wheatley 1999 ; Hellier 2002 ). Thus, a change in mass flow can be a reason for changing geometries between stream-fed dominance and disk-fed dominance. Further, since pure disk-fed accretion also takes place for some of the observational days, it implies that for those days, the contribution of mass accretion from the stream has been negligible in comparison to the disk. 2. They suggested that change in accretion mode is related to changes in the disk itself, which can be easily understood from our one-day analysis of TX Col. The sudden changes between the disk overflow to disk-fed or stream-fed cannot be only because of the change in the mass flow. The changes related to the disk, i.e., the change in the structure of the disk also takes place on such a timescale so that the combined effect of the two processes (i.e., the change in the mass accretion rate and the change in the structure of the disk) have shown such tremendous changes in the system. 4.2. Presence of QPOs We have also found periods of ∼5850–5950 s for days 46, 52, and 71, and these periods could be the QPOs. The flow of matter in IPs can take the form of diamagnetic “blobs” that orbit around the white dwarf (see King 1993 ; Wynn King 1995 for details). The accretion flow in TX Col can be explained as a combination of a stream and orbiting blobs (Hellier 2002 ). Keeping these ideas in mind, Mhlahlo et al. ( 2007 ) claimed that the QPO period results due to the beating of the Keplerian period of the orbiting “blobs” with the spin period. The theoretical calculation of QPO period demands the calculation of Keplerian period ( P kep = 2 π r d / v kep ), which we have calculated in the following way. The mass of the WD in the TX Col system was determined in the range of 0.48–0.82 M ⊙ (see Table 3 of Yuasa et al. 2010 ) in the different previous studies. Therefore, for our calculation, we have used the weighted mean of these mass values as 0.66 ± 0.03 M ⊙ , where the error on mass is the weighted standard deviation of different measurements. The WD radius, R WD , was calculated to be 0.012 ± 0.001 R ⊙ using the mass–radius relation of Nauenberg ( 1972 ). We have estimated the mass of the secondary as 0.61 ± 0.04 M ⊙ using the mass–period relation given by Smith Dhillon ( 1998 ). As a result, the mass ratio (q) was estimated to be 0.92 ± 0.07. The disk radius ( r d ) lies in the range of 2–3 times r r , where r r is the minimum outer radius of disk (Sulkanen et al. 1980 ). The estimation of r r involves binary separation (a), which was calculated using the relations as given in Warner ( 1995 ). The values of r r and “a” were found to be 1.08 × 10 10 cm and 12.17 × 10 10 cm, respectively. In this way, r d was estimated to be in the range of (2.2–3.2) × 10 10 cm. Using these parameters of TX Col, we obtained a range for Keplerian velocity () of 520–640 km s −1 . Further, we found that for the Keplerian velocity of ∼550
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