Results of the CCD observations of CzeV404 Her are displayed. During the season of June-August 2014 we detected one outburst and one superoutburst of the star. Clear superhumps with the period of P_sh=0.10472(2) days were observed. The superhump peri
od was decreasing with a high value of P_dot=-2.43(8) x 10^(-4). For 17 eclipses, we calculated an orbital period with the value of P_orb=0.0980203(6) days which indicates that CzeV404 Her belongs to period gap objects and it is the longest orbital period eclipsing SU UMa star. Based on superhump and orbital period determinations, the period excess 6.8 % +/- 0.02 % and the mass ratio q ~ 0.32 of the system were obtained.
We present the results of a photometric campaign of the dwarf nova V1040 Cen. The light curve shows two normal outbursts with recurrence time ~ 40 days and amplitude ~ 2.5 mag. Quiescence data show oscillations with periods in the range ~ 0.1 days (2
.4 h) to ~ 0.5 days (12 h) of unknown origin. We measured the orbital period of V1040 Cen to be P_orb=0.060458(80) days (1.451+-0.002 h). Based on the M_v-P_orb relation we found the distance of V1040 Cen to be 137+-31 pc. In this paper we also report the detection of eleven new variable stars in the field of the monitored dwarf nova.
We report results of an extensive world-wide observing campaign devoted to the recently discovered dwarf nova SDSS J162520.29+120308.7 (SDSS J1625). The data were obtained during the July 2010 eruption of the star and in August and September 2010 whe
n the object was in quiescence. During the July 2010 superoutburst SDSS J1625 clearly displayed superhumps with a mean period of $P_{rm sh}=0.095942(17)$ days ($138.16 pm 0.02$ min) and a maximum amplitude reaching almost 0.4 mag. The superhump period was not stable, decreasing very rapidly at a rate of $dot P = -1.63(14)cdot 10^{-3}$ at the beginning of the superoutburst and increasing at a rate of $dot P = 2.81(20)cdot 10^{-4}$ in the middle phase. At the end of the superoutburst it stabilized around the value of $P_{rm sh}=0.09531(5)$ day. During the first twelve hours of the superoutburst a low-amplitude double wave modulation was observed whose properties are almost identical to early superhumps observed in WZ Sge stars. The period of early superhumps, the period of modulations observed temporarily in quiescence and the period derived from radial velocity variations are the same within measurement errors, allowing us to estimate the most probable orbital period of the binary to be $P_{rm orb}=0.09111(15)$ days ($131.20 pm 0.22$ min). This value clearly indicates that SDSS J1625 is another dwarf nova in the period gap. Knowledge of the orbital and superhump periods allows us to estimate the mass ratio of the system to be $qapprox 0.25$. This high value poses serious problems both for the thermal and tidal instability (TTI) model describing the behaviour of dwarf novae and for some models explaining the origin of early superhumps.
We report CCD photometry of the cataclysmic variable V1113 Cygni. During two campaigns, lasting from May to August 2003 and from March to June 2005, we recorded two superoutburst. In the obtained light curves we detected clear superhumps with a mean
period 0.07891(3) days (113.63(4) min). That fact confirms that the star is a member of SU UMa class of dwarf novae. During the first observed superoutburst the superhump period was decreasing with an enormous rate of $dot P = -4.5(8)times 10^{-4}$ which is one of the highest values ever observed in SU UMa systems.
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 to 13.9 mag. The su
peroutbursts 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 0.059396(4) days (85.530(6) min). The period of the superhumps was constant except for one superoutburst when it increased with a rate of $dot P/P_{rm sh} = 7.6(1.9)cdot 10^{-5}$. Our observations indicate that RZ LMi goes into long intervals of showing permanent superhumps which are observed 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.
We have surveyed a 6.5 x 6.5 field centered on the globular cluster M56 (NGC 6779) in search for variable stars. We have detected seven variables, among which two objects are new identifications. One of the new variables is an RR Lyrae star, the thir
d such star in M56. Comparison of the new observations and old photometric data for an RV Tauri variable V6 indicates a likely period change in the star. Its slow and negative rate of -0.005+/-0.003 d/yr would disagree with post-AGB evolution, however this could be a result of blue-loop evolution and/or random fluctuations of the period.
We report extensive photometry of the dwarf nova V419 Lyr throughout its 2006 July superoutburst till quiescence. The superoutburst with amplitude of ~3.5 magnitude lasted at least 15 days and was characterized by the presence of clear superhumps wit
h a mean period of Psh=0.089985(58) days (129.58+-0.08 min). According to the Stolz-Schoembs relation, this indicates that the orbital period of the binary should be around 0.086 days i.e. within the period gap. During the superoutburst the superhump period was decreasing with the rate of dotP/Psh=-24.8(2.2)*10^-5, which is one of the highest values ever observed in SU UMa systems. At the end of the plateau phase, the superhump period stabilized at a value of 0.08983(8) days. The superhump amplitude decreased from 0.3 mag at the beginning of the superoutburst to 0.1 mag at its end. In the case of V419 Lyr we have not observed clear secondary humps, which seems to be typical for long period systems.
