On the evolutionary status of short-period cataclysmic variables

Littlefair, S. P.; Dhillon, V. S.; Marsh, T. R.; Gänsicke, B. T.; Southworth, J.; Baraffe, I.; Watson, C. A.; Copperwheat, C. M.

doi:10.1111/j.1365-2966.2008.13539.x

Cited by 150 publications

(230 citation statements)

References 78 publications

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“…Eclipsing systems are very useful, since geometrical modelling of their light curves allows for precise measurements of the system parameters, such as masses and radii of the component stars, binary inclination and orbital period (e.g. Littlefair et al 2008;Savoury et al 2011).…”

Section: High-inclination Systemsmentioning

confidence: 99%

1000 cataclysmic variables from the Catalina Real-time Transient Survey

Breedt

Gänsicke

Drake

et al. 2014

Monthly Notices of the Royal Astronomical Society

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Over six years of operation, the Catalina Real-time Transient Survey (CRTS) has identified 1043 cataclysmic variable (CV) candidates -the largest sample of CVs from a single survey to date. Here, we provide spectroscopic identification of 85 systems fainter than g ≥ 19, including three AM Canum Venaticorum binaries, one helium-enriched CV, one polar and one new eclipsing CV. We analyse the outburst properties of the full sample and show that it contains a large fraction of low-accretion-rate CVs with long outburst recurrence times. We argue that most of the high-accretion-rate dwarf novae in the survey footprint have already been found and that future CRTS discoveries will be mostly low-accretion-rate systems. We find that CVs with white-dwarf-dominated spectra have significantly fewer outbursts in their CRTS light curves compared to disc-dominated CVs, reflecting the difference in their accretion rates. Comparing the CRTS sample to other samples of CVs, we estimate the overall external completeness to be 23.6 per cent, but show that as much as 56 per cent of CVs have variability amplitudes that are too small to be selected using the transient selection criteria employed by current ground-based surveys. The full table of CRTS CVs, including their outburst and spectroscopic properties examined in this paper, is provided in the online materials.

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Section: High-inclination Systemsmentioning

confidence: 99%

1000 cataclysmic variables from the Catalina Real-time Transient Survey

Breedt

Gänsicke

Drake

et al. 2014

Monthly Notices of the Royal Astronomical Society

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“…Furthermore, a long-standing mismatch between the predicted and observed minimum period for accreting white dwarf binary systems can be traced to a ∼ 10% offset between the donor radii inferred from observations and those predicted by theoretical model atmospheres 19 . However, such large effects are only possible if the irradiating flux is efficiently absorbed in the atmosphere and redistributed across the terminator, i.e.…”

Section: Models Of Irradiated Planets Suggest That Irradiation Can Inmentioning

confidence: 94%

“…Efficient reprocessing, coupled with poor heat redistribution, has also been found in hot Jupiters in this atmospheric temperature regime 5 and suggested for low-mass stars in accreting white dwarfs 4 . If irradiation is the main cause of the larger-than-predicted donor radii 19 , efficient heat redistribution is required. Our finding that day-side to night-side heat transfer must be modest therefore suggests that irradiation is unlikely to be responsible for inflating the donors.…”

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confidence: 99%

An irradiated brown-dwarf companion to an accreting white dwarf

Santisteban

Knigge

Littlefair

et al. 2016

Nature

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Brown dwarfs and giant planets orbiting close to a host star are subjected to significant irradiation that can modify the properties of their atmospheres. In order to test the atmospheric models that are used to describe these systems, it is necessary to obtain accurate observational estimates of their physical properties (masses, radii, temperatures, albedos). Interacting compact binary systems provide a natural laboratory for studying strongly irradiated sub-stellar objects. As the mass-losing secondary in these systems makes a critical, but poorly understood transition from the stellar to the sub-stellar regime, it is also strongly irradiated by the compact accretor. In fact, the internal and external energy fluxes are both expected to be comparable in these objects, providing access to an unexplored irradiation regime. However, the atmospheric properties of such donors have so far remained largely unknown 3 . Here, we report the direct spectroscopic detection and characterisation of an irradiated sub-stellar donor in an accreting white dwarf binary system. Our near-infrared observations allow us to determine a model-independent mass estimate for the donor of M 2 = 0.055 ± 0.008M and an average spectral type of L1 ± 1, supporting both theoretical predictions and model-dependent observational constraints. Our time-resolved data also allow us to estimate the average irradiation-induced temperature difference between the day and night sides on the sub-stellar donor, ∆T 57 K, and the maximum difference between the hottest and coolest parts of its surface, of ∆T max 200 K. The observations are well described by a simple geometric reprocessing model with a bolometric (Bond) albedo of A B < 0.54 at the 2-σ confidence level, consistent with high reprocessing efficiency, but poor lateral heat redistribution in the donor's atmosphere 4, 5 .Only a single brown dwarf donor to an accreting white dwarf has been detected spectroscopically to date 3 , and no empirical information at all is available regarding the effect of irradiation on the donor's atmosphere. We have therefore carried out simultaneous optical and nearinfrared time-resolved spectroscopy of one such system with the X-Shooter instrument 6 at the Very 2 Large Telescope (ESO). Our target, SDSS J143317.78+101123.3 7 (J1433 hereafter), is an eclipsing system with a short orbital period (P orb = 78.1 min) and a likely donor mass well below the hydrogen-burning limit, as estimated from eclipse modelling (M 2 = 0.0571 ± 0.0007M 8, 9 ). The exceptionally wide wavelength coverage provided by our data set (0.35 µm -2.5 µm) allows us to confidently dissect the overall spectral energy distribution. This is illustrated in Fig. 1. Diskformed, double-peaked hydrogen emission lines can be seen across the entire spectral range. The presence of broad Balmer absorption lines between 0.3 µm and 0.5 µm shows that the white dwarf is the strongest emitter in this wave band. However, the donor star spectrum is clearly visible in the near-infrared and dominates between 1.0 µm and 2.5...

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“…SDSS 1433 -with an orbital period of 78.1 min and donor mass of 0.0571 ± 0.0007 M -was claimed to be a postperiod bounce system by both Littlefair et al (2008) and Savoury et al (2011). Current estimates now place the period minimum at 81.8 ± 0.9 min , suggesting that SDSS 1433 may not, in fact, be a period bouncer.…”

Section: Phl 1445: a Possible Period Bouncer?mentioning

confidence: 94%

“…Another CV, SDSS J143317.78+101123.3 (SDSS 1433), has also been found to host a substellar donor (Littlefair et al 2008;Savoury et al 2011). SDSS 1433 -with an orbital period of 78.1 min and donor mass of 0.0571 ± 0.0007 M -was claimed to be a postperiod bounce system by both Littlefair et al (2008) and Savoury et al (2011).…”

Section: Phl 1445: a Possible Period Bouncer?mentioning

confidence: 99%

PHL 1445: an eclipsing cataclysmic variable with a substellar donor near the period minimum

McAllister

Littlefair

Baraffe

et al. 2015

Monthly Notices of the Royal Astronomical Society

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We present high-speed, three-colour photometry of the eclipsing dwarf nova PHL 1445, which, with an orbital period of 76.3 min, lies just below the period minimum of ∼82 min for cataclysmic variable stars. Averaging four eclipses reveals resolved eclipses of the white dwarf and bright spot. We determined the system parameters by fitting a parameterised eclipse model to the averaged lightcurve. We obtain a mass ratio of q=0.087 ± 0.006 and inclination i=85.2 ± 0.9 • . The primary and donor masses were found to be M w =0.73 ± 0.03 M and M d =0.064 ± 0.005 M , respectively. Through multicolour photometry a temperature of the white dwarf of T w =13200 ± 700 K and a distance of 220 ± 50 pc were determined.The evolutionary state of PHL 1445 is uncertain. We are able to rule out a significantly evolved donor, but not one that is slightly evolved. Formation with a brown dwarf donor is plausible; though the brown dwarf would need to be no older than 600 Myrs at the start of mass transfer, requiring an extremely low mass ratio (q=0.025) progenitor system. PHL 1445 joins SDSS 1433 as a sub-period minimum CV with a substellar donor. These existence of two such systems raises an alternative possibility; that current estimates for the intrinsic scatter and/or position of the period minimum may be in error.

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On the evolutionary status of short-period cataclysmic variables

Cited by 150 publications

References 78 publications

1000 cataclysmic variables from the Catalina Real-time Transient Survey

1000 cataclysmic variables from the Catalina Real-time Transient Survey

An irradiated brown-dwarf companion to an accreting white dwarf

PHL 1445: an eclipsing cataclysmic variable with a substellar donor near the period minimum

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