Revision of the Phenomenological Characteristics of the Algol-Type Stars Using the Nav Algorithm

Abstract

Phenomenological characteristics of the sample of the Algol -type stars are revised using a recently developed NAV ("New Algol Variable") algorithm (2012Ap.....55..536A, 2012arXiv 1212.6707A) and compared to that obtained using common methods of Trigonometric Polynomial Fit (TP) or local Algebraic Polynomial (A) fit of a fixed or (alternately) statistically optimal degree (1994OAP.....7...49A, 2003ASPC..292..391A).The computer program NAV is introduced, which allows to determine the best fit with 7 "linear" and 5 "nonlinear" parameters and their error estimates. The number of parameters is much smaller than for the TP fit (typically 20 -40, depending on the width of the eclipse, and is much smaller (5 -20) for the W UMa and  Lyrae -type stars. This causes more smooth approximation taking into account the reflection and ellipsoidal effects (TP2) and generally different shapes of the primary and secondary eclipses. An application of the method to two -color CCD photometry to the recently discovered eclipsing variable 2MASS J18024395 + 4003309 = VSX J180243.9 +400331 (2015JASS...32..101A) allowed to make estimates of the physical parameters of the binary system based on the phenomenological parameters of the light curve. The phenomenological parameters of the light curves were determined for the sample of newly discovered EA and EW -type stars (VSX J223429.3+552903, VSX J223421.4+553013, VSX J223416.2+553424, USNO-B1.0 1347-0483658, UCAC3-191-085589, VSX J180755.6+074711= UCAC3 196-166827). Despite we have used original observations published by the discoverers, the accuracy estimates of the period using the NAV method are typically better than the original ones.

Instabilities in Interacting Binary Stars

“…The algoritm NAV ("New Algol Variable"), originally introduced for phenomenological modelling of the light curves by , was used for determination of characteristics of newly discovered eclipsing binary (Andronov et al (2012), Tkachenko et al (2015)), while determined these parameters for the prototype eclipsing binaries Algol, β Lyrae and W UMa. Numerous possible improvements of the method NAV by introducing a minimal number of additional phenomenological parameters were introduced (Andronov et al (2016a), Andronov et al (2016b), Andronov et al (2017)).…”