Photometric study of new southern SU UMa‐type dwarf novae and candidates – III. NSV 10934, MM Sco, AB Nor and CAL 86

Monthly Notices of the Royal Astronomical Society (Impact Factor: 5.52). 12/2003; 347(3):861 - 872. DOI:10.1111/j.1365-2966.2004.07271.x
Source: arXiv

ABSTRACT We photometrically observed four southern dwarf novae in outburst (NSV 10934, MM Sco, AB Nor and CAL 86). NSV 10934 was confirmed to be an SU UMa-type dwarf nova with a mean superhump period of 0.07478(1) d. This star also showed transient appearance of quasi-periodic oscillations during the final growing stage of the superhumps. Combined with the recent theoretical interpretation and with the rather unusual rapid terminal fading of normal outbursts, NSV 10934 may be a candidate intermediate polar showing SU UMa-type properties. The mean superhump periods of MM Sco and AB Nor were determined to be 0.06136(4) and 0.08438(2) d, respectively. We suggest that AB Nor belongs to a rather rare class of long-period SU UMa-type dwarf novae with low mass-transfer rates. We also observed an outburst of the suspected SU UMa-type dwarf nova CAL 86. We identified this outburst as a normal outburst and determined the mean decline rate of 1.1 mag d−1.

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    ABSTRACT: 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 with 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.
    Acta Astronomica -Warsaw and Cracow- 11/2007; · 2.68 Impact Factor
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    ABSTRACT: We systematically surveyed period variations of superhumps in SU UMa-type dwarf novae based on newly obtained data and past publications. In many systems, the evolution of superhump period are found to be composed of three distinct stages: early evolutionary stage with a longer superhump period, middle stage with systematically varying periods, final stage with a shorter, stable superhump period. During the middle stage, many systems with superhump periods less than 0.08 d show positive period derivatives. Contrary to the earlier claim, we found no clear evidence for variation of period derivatives between superoutburst of the same object. We present an interpretation that the lengthening of the superhump period is a result of outward propagation of the eccentricity wave and is limited by the radius near the tidal truncation. We interpret that late stage superhumps are rejuvenized excitation of 3:1 resonance when the superhumps in the outer disk is effectively quenched. Many of WZ Sge-type dwarf novae showed long-enduring superhumps during the post-superoutburst stage having periods longer than those during the main superoutburst. The period derivatives in WZ Sge-type dwarf novae are found to be strongly correlated with the fractional superhump excess, or consequently, mass ratio. WZ Sge-type dwarf novae with a long-lasting rebrightening or with multiple rebrightenings tend to have smaller period derivatives and are excellent candidate for the systems around or after the period minimum of evolution of cataclysmic variables (abridged). Comment: 239 pages, 225 figures, PASJ accepted
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    ABSTRACT: We present an analysis of the FUSE spectra of eight high-declination dwarf novae obtained from a Cycle 7 FUSE survey. These DN systems have not been previously studied in the UV and little is known about their white dwarfs (WDs) or accretion disks. We carry out the spectral analysis of the FUSE data using synthetic spectra generated with the codes TLUSTY and SYNSPEC. For two faint objects (AQ Men, V433 Ara) we can only assess a lower limit for the WD temperature or mass accretion rate. NSV 10934 was caught in a quiescent state and its spectrum is consistent with a low mass accretion rate disk. For 5 objects (HP Nor, DT Aps, AM Cas, FO Per and ES Dra) we obtain WD temperatures between 34,000K and 40,000K and/or mass accretion rates consistent with intermediate to outburst states. These temperatures reflect the heating of the WD due to on-going accretion and are similar to the temperatures of other DNs observed on the rise to, and in decline from outburst. The WD Temperatures we obtain should therefore be considered as upper limits, and it is likely that during quiescence AM Cas, FO Per and ES Dra are near the average WD Teff for catalcysmic variables above the period gap (30,000K), similar to U Gem, SS Aur and RX And. Comment: 5 tables, 18 figures, 52 pages, ApJ, accepted
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