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

McAllister, M. J.; Littlefair, S. P.; Baraffe, I.; Dhillon, V. S.; Marsh, T. R.; Bento, J.; Bochiński, J.; Bours, Madelon C. P.; Breedt, E.; Copperwheat, C. M.; Hardy, L. K.; Kerry, P.; Parsons, S. G.; Rostron, John; Sahman, D. I.; Savoury, C. D. J.; Tunnicliffe, Rachel

doi:10.1093/mnras/stv956

Cited by 17 publications

(10 citation statements)

References 40 publications

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“…However, real systems do not reach this orbital period, because the smooth track followed by real systems near period minimum is not well represented by two power laws. PHL 1445 (McAllister et al 2015) is expected to be close to the absolute minimum period for main sequence CVs, and so its orbital period of 76.3 min is used for P bounce here. The value of M bounce shown above was determined from the optimal short-period fit.…”

Section: Updating the Semi-empirical Mass-radius Relation For CV Donomentioning

confidence: 99%

The evolutionary status of Cataclysmic Variables: eclipse modelling of 15 systems

McAllister

Littlefair

Parsons

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present measurements of the component masses in 15 Cataclysmic Variables (CVs) -6 new estimates and 9 improved estimates. We provide new calibrations of the relationship between superhump period excess and mass ratio, and use this relation to estimate donor star masses for 225 superhumping CVs. With an increased sample of donor masses we revisit the implications for CV evolution. We confirm the high mass of white dwarfs in CVs, but find no trend in white dwarf mass with orbital period. We argue for a revision in the location of the orbital period minimum of CVs to 79.6 ± 0.2 min, significantly shorter than previous estimates. We find that CV donors below the gap have an intrinsic scatter of only 0.005 R around a common evolutionary track, implying a correspondingly small variation in angular momentum loss rates. In contrast to prior studies, we find that standard CV evolutionary tracks -without additional angular momentum loss -are a reasonable fit to the donor masses just below the period gap, but that they do not reproduce the observed period minimum, or fit the donor radii below 0.1 M .

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Section: Updating the Semi-empirical Mass-radius Relation For CV Donomentioning

confidence: 99%

The evolutionary status of Cataclysmic Variables: eclipse modelling of 15 systems

McAllister

Littlefair

Parsons

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…(eg. Savoury et al 2011;Littlefair et al 2014;McAllister et al 2015). Non-magnetic CVs have a geometry consisting of several key components: the donor and accretor stars, an accretion disc around the accretor, a stream of matter passing from the donor to the accretor, and a 'bright spot' (sometimes referred to as a 'hot spot') on the edge of the accretion disc at the point of intersection with the infalling matter stream.…”

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confidence: 99%

High-speed photometry of Gaia14aae: an eclipsing AM CVn that challenges formation models

Green

Marsh

Steeghs

et al. 2018

Monthly Notices of the Royal Astronomical Society

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AM CVn-type systems are ultra-compact, hydrogen-deficient accreting binaries with degenerate or semi-degenerate donors. The evolutionary history of these systems can be explored by constraining the properties of their donor stars. We present high-speed photometry of Gaia14aae, an AM CVn with a binary period of 49.7 minutes and the first AM CVn in which the central white dwarf is fully eclipsed by the donor star. Modelling of the lightcurves of this system allows for the most precise measurement to date of the donor mass of an AM CVn, and relies only on geometric and well-tested physical assumptions. We find a mass ratio q = M 2 /M 1 = 0.0287 ± 0.0020 and masses M 1 = 0.87 ± 0.02M and M 2 = 0.0250 ± 0.0013M . We compare these properties to the three proposed channels for AM CVn formation. Our measured donor mass and radius do not fit with the contraction that is predicted for AM CVn donors descended from white dwarfs or helium stars at long orbital periods. The donor properties we measure fall in a region of parameter space in which systems evolved from hydrogen-dominated cataclysmic variables are expected, but such systems should show spectroscopic hydrogen, which is not seen in Gaia14aae. The evolutionary history of this system is therefore not clear. We consider a helium-burning star or an evolved cataclysmic variable to be the most likely progenitors, but both models require additional processes and/or finetuning to fit the data. Additionally, we calculate an updated ephemeris which corrects for an anomalous time measurement in the previously published ephemeris.

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“…The validity of this final assumption has been questioned by Spark & O'Donoghue (2015) through fast photometry observations of the dwarf nova OY Car. However, as stated in McAllister et al (2015), we feel this is still a reasonable assumption to make due to agreement between photometric and spectroscopic parameter estimates Savoury et al 2012 As outlined in McAllister et al (2017), our eclipse model has recently received two major modifications. First, it is now possible to fit multiple eclipse light curves simultaneously, whilst sharing parameters intrinsic to the system being modelled, e.g.…”

Section: Simultaneous Average Light Curve Modellingmentioning

confidence: 87%

“…The relation between donor mass and orbital period in CVs was used to investigate the evolutionary status of SDSS 1057. Figure 7 shows SDSS 1057's donor mass (M d ) plotted against orbital period (P orb ), along with the four other known substellar donor eclipsing systems: SDSS J150722.30+523039.8 (SDSS 1507), PHL 1445, SDSS J143317.78+101123.3 (SDSS 1433) and SDSS J103533.03+055158.4 (SDSS 1035) (Savoury et al 2011;McAllister et al 2015). Also plotted are four evolutionary tracks: a red track representing the evolution of a CV with a main-sequence donor (Knigge, Baraffe & Patterson 2011), and three blue tracks as examples of evolution when systems contain a brown dwarf donor from formation (McAllister et al 2015).…”

Section: Evolutionary State Of Sdss 1057mentioning

confidence: 99%

“…It is expected for a small amount of intrinsic scatter to exist due to differences in white dwarf mass, but a significant contribution may come from variations in the additional angular momentum loss (approximately 2.5× gravita-tional radiation) that is required in order for the donor track to conform with the observed period minimum Knigge, Baraffe & Patterson 2011). In McAllister et al (2015) we used the width of the observed period minimum from Gänsicke et al (2009) as a measure of the intrinsic scatter of the main-sequence donor track, but we concluded this was too small to account for the positions of PHL 1445 and SDSS 1433.…”

Section: Evolution At Period Minimummentioning

confidence: 99%

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SDSS J105754.25+275947.5: a period-bounce eclipsing cataclysmic variable with the lowest-mass donor yet measured

McAllister

Littlefair

Dhillon

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present high-speed, multicolour photometry of the faint, eclipsing cataclysmic variable (CV) SDSS J105754.25+275947.5. The light from this system is dominated by the white dwarf. Nonetheless, averaging many eclipses reveals additional features from the eclipse of the bright spot. This enables the fitting of a parameterised eclipse model to these average light curves, allowing the precise measurement of system parameters. We find a mass ratio of q = 0.0546 ± 0.0020 and inclination i = 85.74 ± 0.21 • . The white dwarf and donor masses were found to be M w = 0.800 ± 0.015 M and M d = 0.0436 ± 0.0020 M , respectively. A temperature T w = 13300 ± 1100 K and distance d = 367 ± 26 pc of the white dwarf were estimated through fitting model atmosphere predictions to multicolour fluxes. The mass of the white dwarf in SDSS 105754.25+275947.5 is close to the average for CV white dwarfs, while the donor has the lowest mass yet measured in an eclipsing CV. A low-mass donor and an orbital period (90.44 min) significantly longer than the period minimum strongly suggest that this is a bona fide period-bounce system, although formation from a white dwarf/brown dwarf binary cannot be ruled out. Very few period-minimum/periodbounce systems with precise system parameters are currently known, and as a consequence the evolution of CVs in this regime is not yet fully understood.

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

Cited by 17 publications

References 40 publications

The evolutionary status of Cataclysmic Variables: eclipse modelling of 15 systems

The evolutionary status of Cataclysmic Variables: eclipse modelling of 15 systems

High-speed photometry of Gaia14aae: an eclipsing AM CVn that challenges formation models

SDSS J105754.25+275947.5: a period-bounce eclipsing cataclysmic variable with the lowest-mass donor yet measured

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