Velimir A. Popov

RETURN OF THE KING: TIME-SERIES PHOTOMETRY OF FO AQUARII’S INITIAL RECOVERY FROM ITS UNPRECEDENTED 2016 LOW STATE

In 2016 May, the intermediate polar FO~Aqr was detected in a low state for the first time in its observational history. We report time-resolved photometry of the system during its initial recovery from this faint state. Our data, which includes high-speed photometry with cadences of just 2 sec, shows the existence of very strong periodicities at 22.5 min and 11.26 min, equivalent to the spin-orbit beat frequency and twice its value, respectively. A pulse at the spin frequency is also present but at a much lower amplitude than is normally observed in the bright state. By comparing our power spectra with theoretical models, we infer that a substantial amount of accretion was stream-fed during our observations, in contrast to the disk-fed accretion that dominates the bright state. In addition, we find that FO~Aqrs rate of recovery has been unusually slow in comparison to rates of recovery seen in other magnetic cataclysmic variables, with an

Observations and light curve solutions of the eclipsing binaries KR Lyn, CSS J110212+244412, NSVS 4917488 and NSVS 7336024

e

The newly discovered eclipsing cataclysmic star 2MASS J16211735 + 4412541 and its peculiarity

-folding time of 115

PY Boo and NSVS 7328383: Two totally-eclipsing W UMa stars with small mass ratios and close parameters

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The W UMa binaries USNO-A2.0 1350-17365531, V471 Cas, V479 Lac and V560 Lac: light curve solutions and global parameters based on the GAIA distances.

days. The recovery also shows irregular variations in the median brightness of as much as 0.2~mag over a 10-day span. Finally, we show that the arrival times of the spin pulses are dependent upon the systems overall brightness.

USNO-B1.0 1452–0049820 and ASAS J102556+2049.3: Two W UMa Binaries Close to the Lower Mass-ratio Limit

We present photometric observations in Sloan filters g′, i′ of the short-period eclipsing stars KR Lyn, CSS J110212+244412, NSVS 4917488 and NSVS 7336024. The light curve solutions revealed that all targets are overcontact binaries whose components are G and K stars. Their temperature differences do not exceed 300 K but they differ considerably in size and mass. NSVS 4917488 and NSVS 7336024 reveal total eclipses and their parameters can be considered as well-determined. We found that KR Lyn, NSVS 4917488 and NSVS 7336024 are of W-subtype while CSS J110212+244412 is A-subtype W UMa-type star.