The Dwarf project Eclipsing binaries precise clocks to

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, 1 Serbia

Circum-binary exoplanets =planets simultaneously orbiting both stars (mass center) of a binary, the planetary orbital period is much longer than that of the binary. . . 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, Co. Ro. T, MOST ✷ (iii) timing of the inner binary eclipses 2

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Timing technique ✷ 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. 4

V 471 Tau ✷ Post-common-envelope system containing a WD and a MS late-type dwarf ✷ enables very precise timing because of short ingress and egress durations. . a BD companion with M 3 = 0. 045 ± 0. 015 MSun and P 3 = 33. 4 yr (Kaminski et al. 2007) 5

HW Vir ✷ two-planet system orbiting the short-period sd. B + 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) 6

Object “rating” 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 7

Precision of a triangular minimum timing ✷ It can be shown (Pribulla et al. , 2012, AN, in press) that: ✷ where Fλ is number of photons from a mλ = 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, kl the extinction coefficient and t (0, 1) throughput of the system 8

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

Intrinsic variability of the binary star ✷ 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 sd. B stars ✷ Applegate's (1992) mechanism: spurious cyclic variability DK CVn, Terrell et al. , 2005, IBVS 5642 10

Suitable types of objects 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 (sd. B or sd. O) and K or M dwarf component ✷ (iii) post-common-envelope systems with a white dwarf (WD) component 11

Important issues. . . ✷ 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 ? 12

Accurate minimum timing: fitting LC by itself ✷ 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: ✷ where T(x) is the template LC and A, B, C, D coefficients allow vertical and horizontal shift, trend and vertical scaling 13

Project strategy & philosophy ✷ 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 2 m-class telescopes ✷ 5 -10 years duration 14

Observing network 40+ instruments at 33 observatories mostly in Europe, 20 -200 cm diameters 15

16 A sample of LC obtained at the Stará Lesná observatory

Additional science ✷ 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 sd. B/sd. O ✷ detection of of eclipsing binaries with pulsating components ✷ detection of new variables ✷. . . 17

Conlusions ✷ 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: http: //www. ta 3. sk/~pribulla/Dwarfs/ http: //astronomy. science. upjs. sk/projectdwarf/ 18

Thank You ! 19