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Register a new userLong-term photometric behavior of the eclipsing cataclysmic variable V729 Sgr
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We present the analysis results of an eclipsing cataclysmic variable (CV) V729 Sgr, based on our observations and AAVSO data. Some outburst parameters were determined such as outburst amplitude ($A_{n}$) and recurrence time ($T_{n}$), and then the relationship between $A_{n}$ and $T_{n}$ is discussed. A cursory examination for the long-term light curves reveals that there are small-amplitude outbursts and dips present, which is similar to the behaviors seen in some nova-like CVs (NLs). More detailed inspection suggests that the outbursts in V729 Sgr may be Type A (outside-in) with a rise time $sim1.76$ d. Further analysis also shows that V729 Sgr is an intermediate between dwarf nova and NLs, and we constrain its mass transfer rate to $1.59times10^{-9} < dot{M}_{2} < 5.8times10^{-9}M_{odot}yr^{-1}$ by combining the theory for Z Cam type stars with observations. Moreover, the rapid oscillations in V729 Sgr were detected and analyzed for the first time. Our results indicate that the oscillation at $sim 25.5$ s is a true DNO, being associated with the accretion events. The classification of the oscillations at $sim 136$ and $154$ s as lpDNOs is based on the relation between $P_{lpDNOs}$ and $P_{DNOs}$. Meanwhile, the QPOs at the period of hundreds of seconds are also detected.
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New eclipse timings of the Z Cam-type dwarf nova AY Psc were measured and the orbital ephemeris was revised. Based on the long-term AAVSO data, moreover, the outburst behaviors were also explored. Our analysis suggests that the normal outbursts are quasi-periodic, with an amplitude of $sim2.5(pm0.1)$ mag and a period of $sim18.3(pm0.7)$ days. The amplitude vs. recurrence-time relation of AY Psc is discussed, and we concluded that this relation may represents general properties of dwarf nova (DN) outbursts. The observed standstill ends with an outburst, which is inconsistent with the general picture of Z Cam-type stars. This unusual behavior was considered to be related to the mass-transfer outbursts. Moreover, the average luminosity is brighter during standstills than during outburst cycles. The changes in brightness marks the variations in $dot{M}_{2}$ due to the disc of AY Psc is nearly steady state. $dot{M}_{2}$ value was limited to the range from $6.35times10^{-9}$ to $1.18times10^{-8}M_{odot}yr^{-1}$. More detailed examination shows that there are a few small outbursts presence during standstills. These events with amplitudes of $sim0.5-0.9$ mag are very similar to the stunted outbursts reported in some NLs. We discussed several possible mechanisms and suggested that the most reasonable mechanism for these stunted outbursts is a changing mass-transfer rate.
We report K2 observations of the eclipsing cataclysmic variable V729 Sgr which covered nearly 80 days in duration. We find five short outbursts and two long outbursts, one of which shows a clear plateau phase in the rise to maximum brightness. The mean time between successive short outbursts is ~10 d while the time between the two long outbursts is ~38 d. The frequency of these outbursts are unprecedented for a CV above the orbital period gap. We find evidence that the mid-point of the eclipse occurs systematically earlier in outburst than in quiescence. During five of the six quiescent epochs we find evidence for a second photometric period which is roughly 5 percent shorter than the 4.16 h orbital period which we attribute to negative superhumps. V729 Sgr is therefore one of the longest period CVs to show negative superhumps during quiescence.
We study the newly discovered variable star GSC 4560--02157. CCD photometry was performed in 2013--2014, and a spectrum was obtained with the 6-m telescope in June, 2014. GSC 4560--02157 is demonstrated to be a short-period (P=0.265359d) eclipsing variable star. All its flat-bottom primary minima are approximately at the same brightness level, while the stars out-of-eclipse brightness and brightness at secondary minimum varies considerably (by up to 0.6m) from cycle to cycle. Besides, there are short-term (time scale of 0.03-0.04 days) small-amplitude brightness variations out of eclipse. This behavior suggests cataclysmic nature of the star, confirmed with a spectrum taken on June 5, 2014. The spectrum shows numerous emissions of the hydrogen Balmer series, HeI, HeII.
We present the results obtained from unfiltered photometric CCD observations of the newly discovered cataclysmic variable SDSS J040714.78-064425.1 made during 7 nights in November 2003. We establish the dwarf nova nature of the object as it was in outburst during our observations. We also confirm the presence of deep eclipses with a period of 0.17017d+/-0.00003 in the optical light curve of the star. In addition, we found periods of 0.166d+/-0.001 and possibly also 5.3d+/-0.7 in the data. The 0.17017d periodicity is consistent within the errors with the proposed orbital period of 0.165d (Szkody et. al. 2003) and 0.1700d (Monard 2004). Using the known relation between the orbital and superhump periods, we interpret the 0.166d and 5.3d periods as the negative superhump and the nodal precession period respectively. SDSS J040714.78-064425.1 is then classified as a negative superhump system with one of the largest orbital periods.
We present the photometric results of the eclipsing cataclysmic variable (CV) WZ Sge near the period minimum ($P_{min}$). Eight new mid-eclipse times were determined and the orbital ephemeris was updated. Our result shows that the orbital period of WZ Sge is decreasing at a rate of $dot{P}=-2.72(pm0.23)times{10^{-13}},s s^{-1}$. This secular decrease, coupled with previous detection of its donor, suggest that WZ Sge is a pre-bounce system. Further analysis indicates that the observed period decrease rate is about $1.53$ times higher than pure gravitational radiation (GR) driving. We constructed the evolutionary track of WZ Sge, which predicts that $P_{min}$ of WZ Sge is $sim77.98 (pm0.90)$ min. If the orbital period decreases at the current rate, WZ Sge will evolve past its $P_{min}$ after $sim25.3$ Myr. Based on the period evolution equation we find $dot{M}_{2}simeq4.04(pm0.10)times10^{-11}M_{odot}yr^{-1}$, which is compatible with the current concept of CV evolution at ultrashort orbital periods.
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