Dwarf novae in the Hamburg quasar survey: rarer than expected

Aungwerojwit, A.; Gänsicke, B. T.; Rodríguez‐Gil, P.; Hagen, H. J.; Araujo-Betancor, S.; Baernbantner, Otto; Engels, D.; Fried, Robert; Harlaftis, E. T.; Mislis, D.; Nogami, Daisaku; Schmeer, P.; Schwarz, R.; Staude, Andreas; Torres, M. A. P.

doi:10.1051/0004-6361:20065049

Cited by 39 publications

(44 citation statements)

References 79 publications

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“…Selection effects affecting the observed distribution of CVs are considered by Pretorius et al (2007) with particular attention to the Palomar-Green survey (Green et al 1986). They find that existing samples of CVs are strongly biassed against short-period CVs, largely due to inadequate limiting magnitudes (see also Aungwerojwit et al 2006). In addition, postperiod minimum CVs will have long periods of quiescence, and may lack outbursts entirely (Kolb & Baraffe 1999), making their discovery even more difficult.…”

Section: Post-period Minimum Cataclysmic Variablesmentioning

confidence: 99%

On the evolutionary status of short period cataclysmic variables

Littlefair¹,

Dhillon²,

Marsh³

et al. 2008

AIP Conference Proceedings

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We present high-speed, three-colour photometry of seven short period (P orb 95 mins) eclipsing CVs from the Sloan Digital Sky Survey. We determine the system parameters via a parametrized model of the eclipse fitted to the observed lightcurve by χ 2 minimization. Three out of seven of the systems possess brown dwarf donor stars and are believed to have evolved past the orbital period minimum. This is in line with predictions that 40-70 per cent of CVs should have evolved past the orbital period minimum. Therefore, the main result of our study is that the missing population of post-period minimum CVs has finally been identified. The donor star masses and radii are, however, inconsistent with model predictions; the donor stars are approximately 10 per cent larger than expected across the mass range studied here. One explanation for the discrepancy is enhanced angular momentum loss (e.g. from circumbinary discs), however the mass-transfer rates, as deduced from white dwarf effective temperatures, are not consistent with enhanced angular momentum loss. We show it is possible to explain the large donor radii without invoking enhanced angular momentum loss by a combination of geometrical deformation and the effects of starspots due to strong rotation and expected magnetic activity. Choosing unambiguously between these different solutions will require independent estimates of the mass-transfer rates in short period CVs.The white dwarfs in our sample show a strong tendency towards high masses. We show that this is unlikely to be due to selection effects. The dominance of highmass white dwarfs in our sample implies that erosion of the white dwarf during nova outbursts must be negligible, or even that white dwarfs grow in mass through the nova cycle. Amongst our sample there are no Helium core white dwarfs, despite predictions that 30-80 per cent of short period CVs should contain Helium core white dwarfs. We are unable to rule out selection effects as the cause of this discrepancy.

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Section: Post-period Minimum Cataclysmic Variablesmentioning

confidence: 99%

On the evolutionary status of short period cataclysmic variables

Littlefair¹,

Dhillon²,

Marsh³

et al. 2008

AIP Conference Proceedings

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“…Models of binary evolution predict space densities ranging over an order of magnitude or more, from 10 −5 − 10 −4 pc −3 (de Kool 1992;Kolb 1993;Politano 1996). Observational campaigns, largely using X-ray selected samples, have made estimates of the CV space density converging on 0.5-1×10 −5 pc −3 (Patterson 1998;Schreiber & Gänsicke 2003;Aungwerojwit et al 2006;Pretorius et al 2007;Rogel et al 2008;Pretorius & Knigge 2012). The space density found in Pretorius & Knigge (2012) for long-period CVs was 2.1 +3.5 −1.3 × 10 −6 pc −3 which assumed that all systems with unknown periods had periods below the period gap.…”

Section: Introductionmentioning

confidence: 99%

The relationship between X-ray luminosity and duty cycle for dwarf novae and their specific frequency in the inner Galaxy

Britt

Maccarone

Pretorius

et al. 2015

Monthly Notices of the Royal Astronomical Society

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We measure the duty cycles for an existing sample of well observed, nearby dwarf novae using data from AAVSO, and present a quantitative empirical relation between the duty cycle of dwarf novae outbursts and the X-ray luminosity of the system in quiescence. We have found that log DC = 0.63(±0.21) × (log L X (erg s −1 ) − 31.3) − 0.95(±0.1), where DC stands for duty cycle. We note that there is intrinsic scatter in this relation greater than what is expected from purely statistical errors. Using the dwarf nova X-ray luminosity functions from Pretorius & Knigge (2012) and Byckling et al. (2010), we compare this relation to the number of dwarf novae in the Galactic Bulge Survey which were identified through optical outbursts during an 8-day long monitoring campaign. We find a specific frequency of X-ray bright (L X 10 31 erg s −1 ) Cataclysmic Variables undergoing Dwarf Novae outbursts in the direction of the Galactic Bulge of 6.6±4.7×10 −5 M −1 ⊙ . Such a specific frequency would give a Solar neighborhood space density of long period CVs of ρ = 5.6±3.9×10 −6 pc −3 . We advocate the use of specific frequency in future work, given that projects like LSST will detect DNe well outside the distance range over which ρ ≈ const.

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“…Article published by EDP Sciences magnetic CVs with relatively weak X-ray emission such as 1RXS J062518.2+733433 (HS 0618+7336, Araujo-Betancor et al 2003), RX J1554.2+2721 (HS 1552+2730, Thorstensen & Fenton 2002;Gänsicke et al 2004), and HS 0943+1404 ); a number of SW Sextantis stars (Szkody et al 2001;Rodríguez-Gil et al 2004; one of the youngest pre-CVs known (HS 1857+5144, Aungwerojwit et al 2007); long-period CVs (Aungwerojwit et al 2005); and several dwarf novae (Aungwerojwit et al 2006). This paper presents the dynamical determination of the stellar masses in the cataclysmic variable HS 0218+3229.…”

Section: Introductionmentioning

confidence: 99%

An evolved donor star in the long-period cataclysmic variable HS 0218+3229

Rodríguez‐Gil

Torres

Gänsicke

et al. 2009

A&A

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Context. We present time-resolved spectroscopy and photometry of HS 0218+3229, a new long-period cataclysmic variable discovered within the Hamburg Quasar Survey. It is one of the few systems that allow a dynamical measurement of the masses of the stellar components. Aims. We combine the analysis of time-resolved optical spectroscopy and R-band photometry with the aim of measuring the mass of the white dwarf and the donor star and the orbital inclination. Methods. Cross-correlation of the spectra with K-type dwarf templates is used to derive the radial velocity curve of the donor star. An optimal subtraction of the broadened templates is performed to measure the rotational broadening and constrain the spectral type of the donor. Finally, an ellipsoidal model is fitted to the R-band light curve to obtain constraints upon the orbital inclination of the binary system. Results. The orbital period of HS 0218+3229 is found to be 0.297229661 ± 0.000000001 d (7.13351186 ± 0.00000002 h), and the amplitude of the donor's radial velocity curve is K 2 = 162.4 ± 1.4 km s −1 . Modelling the ellipsoidal light curves gives an orbital inclination in the range i = 59 • ± 3 • . A rotational broadening between 82.4 ± 1.2 km s −1 and 89.4 ± 1.3 km s −1 is found when assuming zero and continuum limb darkening, respectively. The secondary star has most likely a spectral type K5 and contributes ∼80-85% to the R-band light. Our analysis yields a mass ratio of 0.52 < q < 0.65, a white dwarf mass of 0.44 < M 1 (M ) < 0.65, and a donor star mass of 0.23 < M 2 (M ) < 0.44. Conclusions. We find that the donor star in HS 0218+3229 is significantly undermassive for its spectral type. It is therefore very likely that it has undergone nuclear evolution prior to the onset of mass transfer.

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Dwarf novae in the Hamburg quasar survey: rarer than expected

Cited by 39 publications

References 79 publications

On the evolutionary status of short period cataclysmic variables

On the evolutionary status of short period cataclysmic variables

The relationship between X-ray luminosity and duty cycle for dwarf novae and their specific frequency in the inner Galaxy

An evolved donor star in the long-period cataclysmic variable HS 0218+3229

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