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Period variations of Algol-type eclipsing binaries AD And, TWCas and IV Cas

“…Their lightcurve solution led to conclusion that the secondary component almost fills its Roche lobe. Djurasevic et al (2006) re-analysed older photoelectric observations from McCook (1971) and determined masses of the primary and secondary components to be M 1 =2.66 M ⊙ and M 2 =1.15 M ⊙ , respectively, which is in agreement with values obtained by Narita et al (2001). Kreiner (1971) used all the available minima times of TW Cas, but could draw no definite conclusions concerning the period variations.…”

“…Kreiner (1971) used all the available minima times of TW Cas, but could draw no definite conclusions concerning the period variations. Narita et al (2001) assumed that the orbital period of TW Cas was slowly decreasing, as was confirmed by Lloyd & Guilbault (2002). Khaliullina (2015) noted that the recent minima times demonstrate sinusoidal changes of the orbital period and thus, cyclic variations of the period due to the presence of a third body in the system are observed.…”

“…TYC -number in Tycho-2 catalog, V -magnitude in the V filter, B − V -colour index, T 0 -initial time of minimum, P -period. Linear ephemeris are taken from the on-line database (Kreiner 2004 Narita et al (2001). Their lightcurve solution led to conclusion that the secondary component almost fills its Roche lobe.…”