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4 Acta Astronomica

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Curious Variables Experiment (CURVE). RZ LMi - the Most Active SU UMa Star

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Olech A. , Wiśniewski M. , Złoczewski K. , Cook L. M. , Mularczyk K. , Kędzierski P.

2008

tom Vol. 58, No. 2

131--152

We report extensive photometry of the frequently outbursting dwarf nova RZ Leo Minoris. During two seasons of observations we detected 12 superoutbursts and 7 normal outbursts. The V magnitude of the star varied in range from 16.5 mag to 13.9 mag. The superoutbursts occur quite regularly flashing every 19.07(4) days and lasting slightly over 10 days. The average interval between two successive normal outbursts is 4.027(3) days. The mean superhump period observed during the superoutbursts is Psh=0.059396(4) days (85.530±0.006 min). The period of the superhumps was constant except for one superoutburst when it increased with a rate of P/Psh=7.6(1.9)×10-5. Our observations indicate that RZ LMi enters the stage of permanent superhumps, both in superoutbursts and quiescence. This may indicate that decoupling of thermal and tidal instabilities play important role in ER UMa systems. No periodic light variations which can be connected with orbital period of the binary were seen, thus the mass ratio and evolutionary status of RZ LMi are still unknown.

Curious Variables Experiment (CURVE). CCD Photometry of Dwarf Nova V660 Herculis

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Olech A. , Złoczewski K. , Cook L. M. , Mularczyk K. , Kędzierski P. , Wiśniewski M.

tom Vol. 55, No. 2

237--246

We report extensive photometry of the dwarf nova V660 Her. During our campaign, lasting from August 2003 to November 2004, we recorded one bright eruption which turned out to be a superoutburst lasting about 15 days and having amplitude of ≈4.5 mag. Clear superhumps with a mean period of Psh=0.080924(18) days (116.53±0.03 min) were present during all nights of the superoutburst. The period of the superhumps was not stable and in the interval covered by our observations it decreased with a rate of P/Psh=-4.0(1.4)×10-5. Based on our data and the known orbital period of the binary we calculate the period excess of 3.4±0.1%, which is typical for an SU UMa star at this orbital period. This value indicates that the mass ratio of the system is q=0.154

Curious Variables Experiment (CURVE). Superhump Period Change Pattern in KS UMa and Other Dwarf Novae

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Olech A. , Schwarzenberg-Czerny A. , Kędzierski P. , Złoczewski K. , Mularczyk K. , Wiśniewski M.

2003

tom Vol. 56, No. 2

175--194

We report extensive photometry of the dwarf nova KS UMa throughout its 2003 superoutburst till quiescence. During the superoutburst the star displayed clear superhumps with a mean period of Psh=0.070092(23) days. In the middle stage of superoutburst the period was increasing with a rate of P/P=(21±12)×10-5 and later was decreasing with a rate of P/P=-(21±8)×10-5. At the end of superoutburst and during first dozen days of quiescence the star was showing late superhumps with a mean period of Plate=0.06926(2) days. This phenomenon was observed even 30 days after beginning of the superoutburst. In quiescence the star shows quasi-periodic modulations with amplitude reaching 0.5 mag. The most common structure observed during this stage was sinusoidal wave characterized by a period of about 0.1 days. Comparing KS UMa to other SU UMa stars we conclude that this group of dwarf novae shows decreasing superhump periods at the beginning and the end of superoutburst but increasing period in the middle phase.

CURious Variables Experiment (CURVE). CCD Photometry and Variable Stars in the Field of Open Cluster NGC 637

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Pietrukowicz P. , Olech A. , Wiśniewski M. , Kędzierski P. , Mularczyk K. , Złoczewski K. , Starczewski S. , Szaruga K.

Acta Astronomica

2006

tom Vol. 56, No. 3

267--275

We present VI photometry for the open cluster NGC 637 which is located in the Cassiopeia region. Morphology of cluster color-magnitude diagram indicates that it is a young object with age of a few million years. The apparent distance modulus of the cluster is 13.9<(m-M)V<14.3 mag, while reddening is 0.69