1 The Dwarf project: Eclipsing binaries - precise clocks to discover exoplanets Theodor Pribulla Astronomical Institute of the Slovak Academy of Sciences, Tatranská Lomnica, Slovakia Science with meter-class telescopes, September 18-21, 2012, Belgrade, Serbia

2 =planets simultaneously orbiting both stars (mass center) of a binary, the planetary orbital period is much longer than that of the binary... Circum-binary exoplanets Detection techniques to detect circum-binary exoplanets are: ✷ (i) RV measurements to detect the wobble of the binary center - problem with close binaries: component spin-up ✷ (ii) photometric detection of transit(s) of the planet(s) across the disk of the inner binary: requires satellite photometry - Kepler, CoRoT, MOST ✷ (iii) timing of the inner binary eclipses

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4 ✷ LITE - timing of pulses, eclipses or pulsations ✷ timing variations of eclipses of the binary system orbited by a substellar body due to the finite velocity of light ✷ enables determination of the orbital parameters similar to spectroscopic elements ✷ sensitive to long-period objects ✷ the exoplanet encyclopedia lists (as of September 15, 2012) 14 planetary systems (16 planets/4 multiple planetary systems) detected by timing. Timing technique

5 ✷ Post-common-envelope system containing a WD and a MS late-type dwarf ✷ enables very precise timing because of short ingress and egress durations. V471 Tau...a BD companion with M 3 = ± M Sun and P 3 = 33.4 yr (Kaminski et al. 2007)

6 ✷ two-planet system orbiting the short-period sdB + M dwarf ✷ HW Vir b: Mb = 19.2±0.2 MJ and HW Vir c: MC = 8.5±0.4 MJ (Lee et al. 2009) HW Vir

7 Chances to discover a circum-binary substellar body depend mostly on 3 factors: ✷ (i) precision and number of minima ✷ (ii) semi-amplitude of the LITE caused by the body ✷ (iii) intrinsic variability of the binary Object “rating”

8 ✷ It can be shown (Pribulla et al., 2012, AN, in press) that: Precision of a triangular minimum timing ✷ where F  is number of photons from a m  = 0 star per square meter and second outside Earth atmosphere, d is the depth and D duration of the minimum, A diameter of the telescope, X is airmass,   the extinction coefficient and   (0, 1) throughput of the system

9 ✷ The full amplitude  T (Max-Min, or peak-to-peak) of expected LITE caused by another body orbiting a binary with edge-on orbit is: LITE amplitude ✷ The total mass of the under-lying binary is important: having 8 times more massive inner binary decreases the LITE amplitude four times. ✷  T=4-8 seconds for our sample of stars and a Jupiter-mass planet on a 10-years orbit

10 ✷ Spots and flares in the late-type K or M dwarfs: The advantage of low-mass binaries is offset by their surface activity ✷ pulsations in sdB stars ✷ Applegate's (1992) mechanism: spurious cyclic variability Intrinsic variability of the binary star DK CVn, Terrell et al., 2005, IBVS 5642

11 The following three groups of objects with sharp minima were included: ✷ (i) systems with K or/and M dwarf components ✷ (ii) systems with a hot subdwarf (sdB or sdO) and K or M dwarf component ✷ (iii) post-common-envelope systems with a white dwarf (WD) component Suitable types of objects

12 ✷ Red noise: LCs are affected (at the 0.01 mag level) by the red noise (atmosphere transparency changes, lack of auto-guiding in some of the telescopes) and the second- order extinction) - PCA approach by Tamuz, Mazeh & Zucker (2005) ? ✷ Inhomogeneity of data: the CCD frames will be obtained at several observatories with different setups ✷ Exact time: shutter delay, time reference UTC ==> BJD in TDB, at least 1 sec accuracy ✷ flux-weighted time of exposure ? Important issues...

13 ✷ advantages: (1) timing from any non-constant part of LC (2) LC itself is the best fitting template (3) possibility to include systematic trends and scaling differences in the data (e.g., because of the filter transparencies) ✷ A simple fitting function can be: Accurate minimum timing: fitting LC by itself ✷ where T(x) is the template LC and A,B,C,D coefficients allow vertical and horizontal shift, trend and vertical scaling

14 ✷ involving large number of instruments (now 40+) ✷ selecting several dozens of most promising targets ✷ involving amateur observers to survey preliminary list of objects (from NSVS, HAT, KIC, ASAS etc.) ✷ follow-up of interesting objects with 2m-class telescopes ✷ 5-10 years duration Project strategy & philosophy

15 Observing network 40+ instruments at 33 observatories mostly in Europe, cm diameters

16 A sample of LC obtained at the Stará Lesná observatory

17 ✷ study of spot cycles in the RS CVn-like late-type stars binaries, detection of flares ✷ detection of new low-mass EBs crucial to better define the empirical lower main sequence: determination of absolute parameters of the components ✷ detection of WD and sdB/sdO ✷ detection of of eclipsing binaries with pulsating components ✷ detection of new variables ✷... Additional science

18 ✷ The chances to detect circum-binary bodies depend several factors - brightness, duration and depth of minima, mass of the binary, its intrinsic noise ✷ circum-binary planets down to the Jupiter mass orbiting on a 10-year orbits with meter-class telescopes can be detected ✷ More info at: Conlusions

19 Thank You !