The eclipsing post-common envelope binary CSS21055: a white dwarf with a probable brown-dwarf companion

Beuermann, K.; Dreizler, S.; Hessman, F. V.; Backhaus, Udo; Boesch, Andreas; Husser, Tim-Oliver; Nortmann, L.; Schmelev, A.; Roland, Springer

doi:10.1051/0004-6361/201322241

Cited by 42 publications

(38 citation statements)

References 24 publications

(32 reference statements)

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“…There are three double white dwarf binaries in our programme, CSS 41177 (Parsons et al 2011b;Bours et al 2014aBours et al , 2015, GALEX J1717+6757 (Vennes et al 2011;Hermes et al 2014) and NLTT 11748 (Steinfadt et al 2010;Kawka et al 2010;Kilic et al 2010;Kaplan et al 2014). There are also two white dwarf + brown dwarf binaries in the eclipse timing programme, CSS 21055 (Beuermann et al 2013b;Littlefair et al 2014) and SDSS J103533.02+055158.3 (Littlefair et al 2006a;Savoury et al 2011).…”

Section: Binaries With Brown Dwarf or White Dwarf Secondariesmentioning

confidence: 99%

Long-term eclipse timing of white dwarf binaries: an observational hint of a magnetic mechanism at work

Bours

Marsh

Parsons

et al. 2016

Mon. Not. R. Astron. Soc.

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We present a long-term programme for timing the eclipses of white dwarfs in close binaries to measure apparent and/or real variations in their orbital periods. Our programme includes 67 close binaries, both detached and semi-detached and with M-dwarfs, K-dwarfs, brown dwarfs or white dwarfs secondaries. In total, we have observed more than 650 white dwarf eclipses. We use this sample to search for orbital period variations and aim to identify the underlying cause of these variations. We find that the probability of observing orbital period variations increases significantly with the observational baseline. In particular, all binaries with baselines exceeding 10 yrs, with secondaries of spectral type K2 -M5.5, show variations in the eclipse arrival times that in most cases amount to several minutes. In addition, among those with baselines shorter than 10 yrs, binaries with late spectral type (>M6), brown dwarf or white dwarf secondaries appear to show no orbital period variations. This is in agreement with the so-called Applegate mechanism, which proposes that magnetic cycles in the secondary stars can drive variability in the binary orbits. We also present new eclipse times of NN Ser, which are still compatible with the previously published circumbinary planetary system model, although only with the addition of a quadratic term to the ephemeris. Finally, we conclude that we are limited by the relatively short observational baseline for many of the binaries in the eclipse timing programme, and therefore cannot yet draw robust conclusions about the cause of orbital period variations in evolved, white dwarf binaries.

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Section: Binaries With Brown Dwarf or White Dwarf Secondariesmentioning

confidence: 99%

Long-term eclipse timing of white dwarf binaries: an observational hint of a magnetic mechanism at work

Bours

Marsh

Parsons

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Despite many candidate systems being discovered from all-sky surveys (e.g. Girven et al 2011;Debes et al 2011), only eight postcommon envelope systems have been confirmed: GD1400 (WD+L6, P=9.98 hrs; Farihi & Christopher 2004;Dobbie et al 2005;Burleigh et al 2011), WD0137-349 (WD+L6-E-mail: slc25@le.ac.uk † Hubble Fellow L8, P=116 min; Maxted et al 2006;Burleigh et al 2006a), WD0837+185 (WD+T8, P=4.2 hrs; Casewell et al 2012), NLTT5306 (WD+L4-L7, P=101.88 min; Steele et al 2013), SDSS J155720.77+091624.6 (WD+L3-L5, P=2.27 hrs); Farihi et al 2017, SDSS J1205-0242 (WD+L0, P=71.2 min; Parsons et al 2017;Rappaport et al 2017), SDSS J1231+0041 (WD+M/L, P=72.5 min; Parsons et al 2017) and SDSS J141126.20+200911.1, (WD+T5, P=121.73 min; Beuermann et al 2013;Littlefair et al 2014). All of these systems have survived a phase of common-envelope evolution, resulting in the close binary system.…”

Section: Introductionmentioning

confidence: 98%

The first sub-70 min non-interacting WD–BD system: EPIC212235321

Casewell

Braker

Parsons

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We present the discovery of the shortest-period, non-interacting, white dwarf-brown dwarf post-common-envelope binary known. The K2 light curve shows the system, EPIC 21223532 has a period of 68.2 min and is not eclipsing, but does show a large reflection effect due to the irradiation of the brown dwarf by the white dwarf primary. Spectra show hydrogen, magnesium and calcium emission features from the brown dwarf's irradiated hemisphere, and the mass indicates the spectral type is likely to be L3. Despite having a period substantially lower than the cataclysmic variable period minimum, this system is likely a pre-cataclysmic binary, recently emerged from the common-envelope. These systems are rare, but provide limits on the lowest mass object that can survive common envelope evolution, and information about the evolution of white dwarf progenitors, and post-common envelope evolution.

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“…The other three are: GD1400, (WD+L6, P=9.98hrs Farihi & Christopher 2004;Dobbie et al 2005;Burleigh et al 2011), WD0837+185 (WD+T8, P=4.2hrs Casewell et al 2012) and NLTT5306 (WD+L4-L7, P=101.88 min Steele et al 2013). Another eclipsing, candidate system has recently been reported (CSS21055, Beuermann et al 2013) but is yet to be confirmed via radial velocity or spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Multiwaveband photometry of the irradiated brown dwarf WD0137−349B

Casewell

Lawrie

Maxted

et al. 2015

Monthly Notices of the Royal Astronomical Society

100

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WD0137-349 is a white dwarf-brown dwarf binary system in a 116 minute orbit. We present radial velocity observations and multiwaveband photometry from V , R and I in the optical, to J, H and K s in the near-IR and [3.6], [4.5], [5.8] and [8.0] µm in the mid-IR. The photometry and lightcurves show variability in all wavebands, with the amplitude peaking at [4.5] microns, where the system is also brightest. Fluxes and brightness temperatures were computed for the heated and unheated atmosphere of the brown dwarf (WD0137-349B) using synthetic spectra of the white dwarf using model atmosphere simulations. We show that the flux from the brown dwarf dayside is brighter than expected in the K s and [4.5] µm bands when compared to models of irradiated brown dwarfs with full energy circulation and suggest this over-luminosity may be attributed to H 2 fluorescence or H + 3 being generated in the atmosphere by the UV irradiation.

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The eclipsing post-common envelope binary CSS21055: a white dwarf with a probable brown-dwarf companion

Cited by 42 publications

References 24 publications

Long-term eclipse timing of white dwarf binaries: an observational hint of a magnetic mechanism at work

Long-term eclipse timing of white dwarf binaries: an observational hint of a magnetic mechanism at work

The first sub-70 min non-interacting WD–BD system: EPIC212235321

Multiwaveband photometry of the irradiated brown dwarf WD0137−349B

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