Orbital Period Analyses for the CVs Inside the Period Gap

Transcription

1 Orbital Period Analyses for the CVs Inside the Period Gap YNAO Dai Zhibin Yunnan Astronomical Observatory, Chinese Academy of Sciences

2 OUTLINE What is the Period Gap? New orbital period distributions of CVs Orbital period analyses Summary

3 Part I. Period Gap

4 What is the Period Gap? Katysheva & Pavlenko (2003)

5 Why is there a gap? " Selection effect for observation (Rappaport et al., 1983) " CV Evolution A. The corresponding gap in white dwarf mass distribution (de Kool, 1992) M wd 0.46M Θ M wd 0. 56M Θ for the CVs below gap for the CVs above gap B. The similar gap has already been shown in the distribution of progenitors of CVs (Vojkhanskaja., 2007) Progenitors of CVs: White dwarf + red dwarf binary system / PCEBs C. Disrupted Magnetic Braking hypothesis (Robinson et al., 1981; McDermott & E. Taam, 1989) Sharp reduction in AML rate when secondary becomes fully convective

6 Standard paradigm of CV evolution A default argument: CVs evolution will shorten its Orbital period Evolution Above Gap Magnetic Wind With radiation core Below Gap Gravitational Radiation Full Convective

7 Part II. Investigation

8 Details of Orbital period distribution The distributions for different subtype of CVs a) Bimodality caused by DN and NL b) The shallower gap in MCV and DN c) No gap in NL and N&RN The pie diagram for the CVs inside below period gap a) MCV DN becomes is a significant a significant subtype subtype inside period below period gap gap b) The Over other 75% subtypes CVs below are gap nearly are DN equal and MCV New N&RN MCV DN NL!

9 A gradual rise branch near 2hr -- is it a result the whole caused gap by gravitational radiation? CVs have spread over The real minimum of gap is near 3hr-- is longer period it a possible evidence for the sudden decline of stellar wind? A small shift towards Smaller interval 10mins for histogram of orbital period distribution

10

11 Part III. Analyses

12 Eclipsing CVs inside gap Subtype MCV DN N & RN Eclipse CVs Orbital Period (hr) *HU Aqr (~15mag) (2.08h)!DD Cir (~20mag) (2.34h) *UZ For (~18mag) (2.11h) *V348 Pup (~15mag) (2.44h)!V597 Pup (>18mag) (2.6687h) *DV Uma (~19mag) (2.06h) *IR Com (~15mag) (2.09h)!SDSS J (~18mag) (2.40h)!CTCV J (~16mag) (2.13h)?TY Psa (~14mag) (2.02h)!V Per (~18mag) (2.57h)!DD Cir (~20mag) (2.34h)!V630 Sgr (~18mag) (2.83h)!QU Vul (~19mag) (2.68h)!V597 Pup (>18mag) (2.6687h)

13 Photometries for AM Her (Dai et al., 2012, in preparation) It locates at the upper edge of period gap. Its secular evolution state is a key factor to test the current evolution theory. Collected from AAVSO and our photometries

14 New O-C diagram of AM Her A typical period decrease rate ~ Low-state data just add the large scatters

15 The orbital period variations Cyclical Secular Log(P mod ) = -0.36(±0.10)Log(Ω) ² A combined masses of 0.78M sun (WD) M sun (RD) means that mass transfer E0/Emin<<1 in AM Her with an average mass transfer rate M sun yr -1 only induces the orbital period increase(gänsicke et al., 2001). ² This increase can be counteracted by the gravitational radiation. ² R 3 /a ~ 10 3 ² The magnetic braking may be suppressed ² in Mpolars 3 (min)/m (Cumming, 2 ~ ). Including Algol, RS CVn,WUMa and CVs (Lanza & Rodonò,1999)

16 Decreasing orbital period (Qian et al., MNRASL, 2011) (Qian et al., ApJL, 2008) HU Aqr(b) HU Aqr (c) Amplitude (d) (17) (14) Eccentricity (±0.15) Period (yr) 6.54(±0.01) 11.96(±1.41) Solar Titus-Bode relation Distance (au) 3.6(±0.8) 5.4(±0.9) Masses (Jup) 5.9(±0.6) HU Aqr 4.5(±0.5) HW Vir P cycle =15.7 yr A cycle = d A planetary system with three giant planets

17 Can we find the orbital period increase? λ( q) Rcr Porb q 1 In conservative case Normal CVs cannot sustain conservative mass transfer. It obviously conflicts with hypothesis of CV evolution We need to pay more attention to the increasing O-C diagrams

18 Possible increasing orbital period (Dai et al., in preparation) E0/Emin~4 (Dai et al., MNRAS, 2010) V348 Pup UZ For UZ For The more increase observations in a decrease long base It Different line should are necessary be model a substellar can for result checking object out for both this totally models increasing opposite (>90% trend variation probability) trend

19 Summary The orbital period distribution for different subtype exhibits the complication of gap. Part of the eclipsing CVs inside gap never give us definite secular evolutional information Most of modulations in O-Cs can be explained by light travel-time effect

20 Thanks for your attention!