Evidence for mass accretion driven by spiral shocks onto the white dwarf in SDSS J123813.73–033933.0

Pala, A. F.; Gänsicke, B. T.; Marsh, T. R.; Breedt, E.; Hermes, J. J.; Landstreet, J. D.; Schreiber, M. R.; Townsley, Dean M.; Wang, L.; Aungwerojwit, A.; Hambsch, Franz-Josef; Monard, B.; Myers, Gordon; Nelson, Peter; Pickard, R.; Poyner, G.; Reichart, D.; Stubbings, Rod; Godon, Patrick; Szkody, Paula; Martino, D. de; Dhillon, V. S.; Knigge, Christian; Parsons, S. G.

doi:10.1093/mnras/sty3174

Cited by 20 publications

(13 citation statements)

References 107 publications

(130 reference statements)

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“…• EZ Lyn is characterised by quasi-periodic brightening events superimposed to a sinusoidal photometric modulations (Zharikov et al 2008(Zharikov et al , 2013 that, in the case of its twin system SDSS J123813.73-033933.0, have been interpreted as the interplay between spiral arms and small amplitude thermal instabilities in the accretion disc (Pala et al 2019). Similar behaviour, although less periodic, has been observed also in GW Lib, where it could be associated with fluctuation in the mass accretion rate (Toloza et al 2016).…”

Section: The Intrinsic Populationmentioning

confidence: 73%

A Volume-limited Sample of Cataclysmic Variables from Gaia DR2: Space Density and Population Properties

Pala

Gänsicke

Breedt

et al. 2020

Monthly Notices of the Royal Astronomical Society

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149

113

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We present the first volume-limited sample of cataclysmic variables (CVs), selected using the accurate parallaxes provided by the second data release (DR2) of the European Space Agency Gaia space mission. The sample is composed of 42 CVs within 150 pc, including two new systems discovered using the Gaia data, and is $(77 \pm 10)$ per cent complete. We use this sample to study the intrinsic properties of the Galactic CV population. In particular, the CV space density we derive, $\rho =(4.8^{+0.6}_{-0.8}) \times 10^{-6}\, \mbox{$\mathrm{pc}^{-3}$}$, is lower than that predicted by most binary population synthesis studies. We also find a low fraction of period bounce CVs, seven per cent, and an average white dwarf mass of $\langle M_\mathrm{WD} \rangle = (0.83 \pm 0.17)\, \mathrm{M}_\odot$. Both findings confirm previous results, ruling out the presence of observational biases affecting these measurements, as has been suggested in the past. The observed fraction of period bounce CVs falls well below theoretical predictions, by at least a factor of five, and remains one of the open problems in the current understanding of CV evolution. Conversely, the average white dwarf mass supports the presence of additional mechanisms of angular momentum loss that have been accounted for in the latest evolutionary models. The fraction of magnetic CVs in the 150 pc sample is remarkably high at 36 per cent. This is in striking contrast with the absence of magnetic white dwarfs in the detached population of CV progenitors, and underlines that the evolution of magnetic systems has to be included in the next generation of population models.

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Section: The Intrinsic Populationmentioning

confidence: 73%

A Volume-limited Sample of Cataclysmic Variables from Gaia DR2: Space Density and Population Properties

Pala

Gänsicke

Breedt

et al. 2020

Monthly Notices of the Royal Astronomical Society

Self Cite

149

113

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“…On the other hand, observations (see e.g. Pala et al, 2019) indicate that spiral shocks are present and might play a role in the accretion process, but their interpretation is not straightforward.…”

Section: Spiral Wavesmentioning

confidence: 99%

A review of the disc instability model for dwarf novae, soft X-ray transients and related objects

Hameury

2020

Advances in Space Research

132

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A B S T R A C T I review the basics of the disc instability model (DIM) for dwarf novae and soft-X-ray transients and its most recent developments, as well as the current limitations of the model, focusing on the dwarf nova case. Although the DIM uses the Shakura-Sunyaev prescription for angular momentum transport, which we know now to be at best inaccurate, it is surprisingly efficient in reproducing the outbursts of dwarf novae and soft X-ray transients, provided that some ingredients, such as irradiation of the accretion disc and of the donor star, mass transfer variations, truncation of the inner disc, etc., are added to the basic model. As recently realized, taking into account the existence of winds and outflows and of the torque they exert on the accretion disc may significantly impact the model. I also discuss the origin of the superoutbursts that are probably due to a combination of variations of the mass transfer rate and of a tidal instability. I finally mention a number of unsolved problems and caveats, among which the most embarrassing one is the modelling of the low state. Despite significant progresses in the past few years both on our understanding of angular momentum transport, the DIM is still needed for understanding transient systems.

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“…Following an outburst, the white dwarf is heated as a consequence of the increased infall of material, and this can possibly give rise to a non-homogeneous distribution of the temperature across its visible surface. Heated accretion belts or hot spots can dominate the overall ultraviolet emission of the system and the resulting temperature gradient results in the white dwarf radius being underestimated (e.g Toloza et al 2016;Pala et al 2019). The presence of a hot spot can be easily unveiled thanks to the modulation it introduces in the light curve of the system.…”

Section: Wavelength [ ]mentioning

confidence: 99%

“…Throughout the duration of the individual HST observations (typically a few hours), CVs can show different types of variability, such as eclipses, modulations due to the white dwarf rotation, white dwarf pulsations, double humps and brightenings (e.g. Szkody et al 2002b;Araujo-Betancor et al 2003;Szkody et al 2017;Toloza et al 2016;Pala et al 2019). Eclipses are particularly important since they allow a white dwarf mass measurement based only on geometrical assumptions to be obtained.…”

Section: Light Curve Analysismentioning

confidence: 99%

“…In contrast, pulsations and brightenings reflect the presence of hot spots and, more generally, of a gradient in temperature over the visible white dwarf surface. When in view, the emission of the hot spots can dominate the overall ultraviolet emission of the system making the white dwarf look hotter and affecting both the temperature and mass estimates (Toloza et al 2016;Pala et al 2019). Therefore, it is important to remove the contribution of these spurious sources in order to obtain an accurate mass measurement.…”

Section: Light Curve Analysismentioning

confidence: 99%

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Constraining the Evolution of Cataclysmic Variables via the Masses and Accretion Rates of their Underlying White Dwarfs

Pala,

Gänsicke,

Belloni

et al. 2021

Preprint

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We report on the masses (𝑀 WD ), effective temperatures (𝑇 eff ) and secular mean accretion rates ( 𝑀 ) of 43 cataclysmic variable (CV) white dwarfs, 42 of which were obtained from the combined analysis of their Hubble Space Telescope ultraviolet data with the parallaxes provided by the Early Third Data Release of the Gaia space mission, and one from the white dwarf gravitational redshift. Our results double the number of CV white dwarfs with an accurate mass measurement, bringing the total census to 89 systems. From the study of the mass distribution, we derive 𝑀 WD = 0.81 +0.16 −0.20 M , in perfect agreement with previous results, and find no evidence of any evolution of the mass with orbital period. Moreover, we identify five systems with 𝑀 WD < 0.5M , which are most likely representative of helium-core white dwarfs, showing that these CVs are present in the overall population. We reveal the presence of an anti-correlation between the average accretion rates and the white dwarf masses for the systems below the 2 − 3 h period gap. Since 𝑀 reflects the rate of system angular momentum loss, this correlation suggests the presence of an additional mechanism of angular momentum loss that is more efficient at low white dwarf masses. This is the fundamental concept of the recently proposed empirical prescription of consequential angular momentum loss (eCAML) and our results provide observational support for it, although we also highlight how its current recipe needs to be refined to better reproduce the observed scatter in 𝑇 eff and 𝑀 , and the presence of helium-core white dwarfs.

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Evidence for mass accretion driven by spiral shocks onto the white dwarf in SDSS J123813.73–033933.0

Abstract: Please refer to published version for the most recent bibliographic citation information. If a published version is known of, the repository item page linked to above, will contain details on accessing it.

Cited by 20 publications

References 107 publications

A Volume-limited Sample of Cataclysmic Variables from Gaia DR2: Space Density and Population Properties

A Volume-limited Sample of Cataclysmic Variables from Gaia DR2: Space Density and Population Properties

A review of the disc instability model for dwarf novae, soft X-ray transients and related objects

Constraining the Evolution of Cataclysmic Variables via the Masses and Accretion Rates of their Underlying White Dwarfs

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