High-speed photometry of Z Chamaeleontis in the quiescent state

Cook, Mike; Warner, Brian D.

doi:10.1093/mnras/207.4.705

Cited by 37 publications

(24 citation statements)

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“…A turn-over is observed in the egress for <j> > 1.1. This is similar to the variability seen in Z Cha (Cook & Warner 1984), caused by the presence of a hot spot on the disc. In CAL 87, an analogous component may be the strongly irradiated inner-surface of the accretion disc bulge.…”

Section: Macho Project Photometrysupporting

confidence: 81%

Optical Photometry of the Eclipsing LMC Supersoft Source CAL 87

Southwell¹,

Charles²,

O’Donoghue

et al. 1997

International Astronomical Union Colloquium

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Section: Macho Project Photometrysupporting

confidence: 81%

Optical Photometry of the Eclipsing LMC Supersoft Source CAL 87

Southwell¹,

Charles²,

O’Donoghue

et al. 1997

International Astronomical Union Colloquium

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“…7) and X‐ray (Ishibashi et al 1999) light curves of η Car even show evidence of a two‐step structure similar to that seen in the eclipse light curves of some cataclysmic variables (e.g. Z Cha: see Cook & Warner 1984). In the case of η Car the ‘hotspot’ could either be on a disc or else be a hot region in an interacting wind model, and the eclipse could be due either to an optically thick plasma or to a star.…”

Section: Discussionmentioning

confidence: 64%

Variability ofηCarinae - III

Feast¹,

Whitelock²,

Marang³

2001

Monthly Notices of the Royal Astronomical Society

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Spectra (1951–78) of the central object in η Car, taken by A. D. Thackeray, reveal three previously unrecorded epochs of low excitation. Since 1948, at least, these states have occurred regularly in the 2020‐d cycle proposed by Damineli et al. They last about 10 per cent of each cycle. Early slit spectra (1899–1919) suggest that at that time the object was always in a low state. JHKL photometry is reported for the period 1994–2000. This shows that the secular increase in brightness found in 1972–94 has continued and its rate has increased at the shorter wavelengths. Modulation of the infrared brightness in a period near 2020 d continues. There is a dip in the JHKL light curves near 1998.0, coincident with a dip in the X‐ray light curve. Evidence is given that this dip in the infrared repeats in the 2020‐d cycle. As suggested by Whitelock & Laney, the dip is best interpreted as an eclipse phenomenon in an interacting binary system; the object eclipsed being a bright region (‘hotspot’), possibly on a circumstellar disc or produced by interacting stellar winds. The eclipse coincides in phase and duration with the state of low excitation. It is presumably caused by a plasma column and/or by one of the stars in the system.

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“…The concept was pioneered for Z Cha by Smak (1979) and Cook & Warner (1984), and subsequently adopted for a handful of bright eclipsing CVs. The advent of ULTRACAM on large aperture telescopes , and an increasing sample of eclipsing CVs, predominantly from the SDSS (Szkody et al 2009), led to a significant increase in the number of CVs with published high-precision WD masses (e.g., Feline et al 2004a;Littlefair et al 2006b;Savoury et al 2011).…”

Section: The Wd Masses Of Cvsmentioning

confidence: 99%

Post common envelope binaries from SDSS

Zorotovic

Schreiber

Gänsicke

2011

A&A

300

336

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Context. We have known for a long time that many of the measured white dwarf (WD) masses in cataclysmic variables (CVs) significantly exceed the mean mass of single WDs. This was thought to be related to observational biases, but recent high-precision measurements of WD masses in a great number of CVs are challenging this interpretation. A crucial question in this context is whether the high WD masses seen among CVs are already imprinted in the mass distribution of their progenitors, i.e. among detached postcommon-envelope binaries (PCEBs) that consist of a WD and a main-sequence star. Aims. We review the measured WD masses of CVs, determine the WD-mass distribution of an extensive sample of PCEBs that are representative for the progenitors of the current CV population (pre-CVs) and compare both distributions. Methods. We calculate the CV formation time of the PCEBs in our sample by determining the post common-envelope (CE) and the main-sequence evolution of the binary systems and define a pre-CV to be a PCEB that evolves into a semi-detached configuration with stable mass transfer within less than the age of the Galaxy. Possible observational biases affecting the WD-mass distribution for the pre-CV and the CV samples are discussed. Results. The mean WD mass among CVs is M wd = 0.83 ± 0.23 M , much larger than that found for pre-CVs, M wd = 0.67 ± 0.21 M . Selection effects cannot explain the high WD masses observed in CVs. We also note that compared to the predictions of binary-population models, the observed fraction of He-core WDs is small both among CVs (≤10%) and pre-CVs (≤17 ± 8%). Conclusions. We suggest two possible explanations for the high WD masses among CVs, both of which imply substantial revisions to the standard model of CV evolution: either most CVs have formed above the orbital-period gap (which requires a high WD mass to initiate stable mass transfer or a previous phase of thermal-timescale mass transfer), or the mass of the WDs in CVs grows through accretion (which strongly disagrees with the predictions of classical nova models). Both options may imply that CVs contribute to the single-degenerate progenitors of type Ia supernovae. The number of He-core WDs in CVs (≤10%) is roughly consistent with the number of He-core WDs in pre-CVs (≤17 ± 8%). This indicates a low value of the CE efficiency.

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High-speed photometry of Z Chamaeleontis in the quiescent state

Cited by 37 publications

References 0 publications

Optical Photometry of the Eclipsing LMC Supersoft Source CAL 87

Optical Photometry of the Eclipsing LMC Supersoft Source CAL 87

Variability ofηCarinae - III

Post common envelope binaries from SDSS

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