SPH simulations of negative (nodal) superhumps: a parametric study

Wood, M. A.; Thomas, David M.; Simpson, J.

doi:10.1111/j.1365-2966.2009.15252.x

Cited by 48 publications

(55 citation statements)

References 91 publications

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“…An analysis of the phase variations in the quiescent-state oscillations in the light curve at the beginning of Figure 2 light curve shows these are likely to be negative superhumps. As such they indicate accretion onto an accretion disk that is tilted a few degrees out of the orbital plane and precessing slowly in the retrograde direction (Barrett et al 1988;Foulkes et al 2006;Wood & Burke 2007;Wood et al 2000Wood et al , 2009. Instead of impacting the rim of the disk, the accretion spot sweeps across first one face of the tilted disk and then the other during one orbit, impacting the rim only twice during one cycle, along the line of nodes.…”

Section: Relevance Of Results To the V344 Lyr Light Curvementioning

confidence: 99%

THEKEPLERLIGHT CURVE OF V344 Lyrae: CONSTRAINING THE THERMAL-VISCOUS LIMIT CYCLE INSTABILITY

Cannizzo

Still

Howell

et al. 2010

ApJ

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We present time-dependent modeling based on the accretion disk limit cycle model for a 270 d light curve of the short-period SU UMa-type dwarf nova V344 Lyr taken by Kepler. The unprecedented precision and cadence (1 minute) far surpass that generally available for long-term light curves. The data encompass two superoutbursts and 17 normal (i.e., short) outbursts. The main decay of the superoutbursts is nearly perfectly exponential, decaying at a rate ∼12 d mag −1 , while the much more rapid decays of the normal outbursts exhibit a fasterthan-exponential shape. Our modeling using the basic accretion disk limit cycle can produce the main features of the V344 Lyr light curve, including the peak outburst brightness. Nevertheless, there are obvious deficiencies in our model light curves. (1) The rise times we calculate, both for the normal and superoutbursts, are too fast.(2) The superoutbursts are too short. (3) The shoulders on the rise to superoutburst have more structure than the shoulders in the observed superoutbursts and are too slow, comprising about a third to half of the total viscous plateau, rather than the ∼10% observed. However, one of the α cold ↔ α hot interpolation schemes we investigate (one that is physically motivated) does yield longer superoutbursts with suitably short, less structured shoulders.

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Section: Relevance Of Results To the V344 Lyr Light Curvementioning

confidence: 99%

THEKEPLERLIGHT CURVE OF V344 Lyrae: CONSTRAINING THE THERMAL-VISCOUS LIMIT CYCLE INSTABILITY

Cannizzo

Still

Howell

et al. 2010

ApJ

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“…Both contribute to the negative superhump light signal. Therefore, when the gas stream is turned off as shown by Wood et al (2009), only one source is eliminated, but not the second. The negative superhump will still persist in a tilted disc regardless if the stream is present or not and the source is from the centre of the disc as shown by Wood et al and Montgomery. These results would seem to support our explanation for the eclipse depth modulation in PX And.…”

Section: Px and Discussionmentioning

confidence: 99%

SuperWASP observations of long timescale photometric variations in cataclysmic variables

Thomas

Norton

Pollacco

et al. 2010

A&A

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Aims. We investigated whether the predictions and results of Stanishev et al. (2002, A&A, 394, 625) concerning a possible relationship between eclipse depths in PX And and its retrograde disc precession phase, could be confirmed in long term observations made by SuperWASP. In addition, two further CVs (DQ Her and V795 Her) in the same SuperWASP data set were investigated to see whether evidence of superhump periods and disc precession periods were present and what other, if any, long term periods could be detected. Methods. Long term photometry of PX And, V795 Her and DQ Her was carried out and Lomb-Scargle periodogram analysis undertaken on the resulting light curves. For the two eclipsing CVs, PX And and DQ Her, we analysed the potential variations in the depth of the eclipse with cycle number. Results. The results of our period and eclipse analysis on PX And confirm that the negative superhump period is 0.1417 ± 0.0001d.We find no evidence of positive superhumps in our data suggesting that PX And may have been in a low state during our observations. We improve on existing estimates of the disc precession period and find it to be 4.43 ± 0.05d. Our results confirm the predictions of Stanishev et al. (2002). We find that DQ Her does not appear to show a similar variation for we find no evidence of negative superhumps or of a retrograde disc precession. We also find no evidence of positive superhumps or of a prograde disc precession and we attribute the lack of positive superhumps in DQ Her to be due to the high mass ratio of this CV. We do however find evidence for a modulation of the eclipse depth over a period of 100 days which may be linked with solar-type magnetic cycles which give rise to long term photometric variations. The periodogram analysis for V795 Her detected the likely positive superhump period 0.1165d, however, neither the 0.10826d orbital period nor the prograde 1.53d disc precession period were seen. Here though we have found a variation in the periodogram power function at the positive superhump period, over a period of at least 120 days.

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“…The three-dimensional SPH codes used and described in Wood et al (2000Wood et al ( , 2009Wood et al ( , 2011 and Montgomery (2004Montgomery ( , 2009a have their roots in Simpson (1995), a code that applies to nonmagnetic CV systems. These later versions of the root code have, e.g., more particles (i.e., more than 100,000), modified particle shapes, varying injection rates.…”

Section: Three-dimensional Sph Numerical Codementioning

confidence: 99%

Tilt, Warp, and Simultaneous Precessions in Disks

Montgomery¹

2012

ApJ

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Warps are suspected in disks around massive compact objects. However, the proposed warping source-non-axisymmetric radiation pressure-does not apply to white dwarfs. In this Letter, we report the first smoothed particle hydrodynamic simulations of accretion disks in SU UMa-type systems that naturally tilt, warp, and simultaneously precess in the prograde and retrograde directions using white dwarf V344 Lyrae in the Kepler field as our model. After ∼79 days in V344 Lyrae, the disk angular momentum L d becomes misaligned to the orbital angular momentum L o . As the gas stream remains normal to L o , hydrodynamics (e.g., the lift force) is a likely source to disk tilt. In addition to tilt, the outer disk annuli cyclically change shape from circular to highly eccentric due to tidal torques by the secondary star. The effect of simultaneous prograde and retrograde precession is a warp of the colder, denser midplane as seen along the disk rim. The simulated rate of apsidal advance to nodal regression per orbit nearly matches the observed ratio in V344 Lyrae.

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SPH simulations of negative (nodal) superhumps: a parametric study

Cited by 48 publications

References 91 publications

THEKEPLERLIGHT CURVE OF V344 Lyrae: CONSTRAINING THE THERMAL-VISCOUS LIMIT CYCLE INSTABILITY

THEKEPLERLIGHT CURVE OF V344 Lyrae: CONSTRAINING THE THERMAL-VISCOUS LIMIT CYCLE INSTABILITY

SuperWASP observations of long timescale photometric variations in cataclysmic variables

Tilt, Warp, and Simultaneous Precessions in Disks

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