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The DWARF project: Vidojevica Vince Oliver, Astronomical observatory of Belgrade

The DWARF project: Vidojevica Vince Oliver, Astronomical observatory of Belgrade. Outline. * Will talk about the Serbian side of the DWARF project. The DWARF: “Definition”.

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The DWARF project: Vidojevica Vince Oliver, Astronomical observatory of Belgrade

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  1. The DWARF project: VidojevicaVince Oliver, Astronomical observatory of Belgrade

  2. Outline * Will talk about the Serbian side of the DWARF project

  3. The DWARF: “Definition” • DWARF is an international project aimed at detection of circumbinaryextrasolar planets using the timing of the minima of low-mass eclipsing binaries.

  4. The DWARF: Recall • In general, we can consider 2 types of binary-planet configurations: S-type (planet orbit one star and Pbin>>Ppla) P-type (planet orbit both stars and Ppla>>Pbin) P-type = circumbinaryextrasolar planet (Kepler-16: Saturn-mas planet orbitin K+M dwarfs with P~229days)

  5. The DWARF: Program stars • Starting sample of program stars consist 45 stars that can be sorted into 3 groups: • systems with K or/and M dwarf components • systems with hot subdwarf (sdO or sdB) and K or M dwarf components, • post-common envelope systems with a white dwarf (WD) component.

  6. The DWARF: Program stars Porbit < 5 days => to cover the minima R=10-17mag => 20-200cm telescopes

  7. The DWARF: Detection In general, we have 3 principal techniques: • precise radial-velocity measurements to detect the wobble of the binary mass center, • Photometric detection of transits of the planet(s) across the disks of the components of the inner binary, and • timing of the inner binary eclipse BUT The timing technique proved to be the best for detecting circumbinary planets

  8. The DWARF: Timing technique • The timing technique = precisely measure of the exact instant of some well-defined and repeating feature of the binary light curve (e.g. minimum) e.g. Kepler 16

  9. The DWARF: Members Huge network consisting of 37 institutes/observatories 18 countries 1. Slovakia 2. Germany 3. Russia 4. Ukraine 5. Turkey 6. Egipt 7. Italy 8. Croatia 9. Greece 10. Bulgaria 11. Austria 12. Korea 13. Poland 14. Romania 15. Portugal 16. Czech Republic 17. Hungary 18. Serbia

  10. The DWARF: Teles/Instruments • Telescope sizes: 20 – 200 cm. • Types: Cass, Schmidt-Cass, RC, few Newtons • FOV: 7’x7’ – 132’ x 132’

  11. AOB: Serbian side of the DWARF project • Project ”Stellar Physics” at the AOB participate in the DWARF project since may 2012 • People currently involved in the project: Dr GojkoDjurasevic Dr Istvan Vince Monika Jurkovic Dr Oliver Vince

  12. ASV: Equipment • Observatory is on the Vidojevica mountain: 1150m • 60cm telescope (Cass, Astro System Austria) • ALTA Apogee U42 (2048x2048, 15’x15’ FOV, 0.46 “/pix) • Optec filter wheel (Bessel filters: B V R I)

  13. ASV: Controlling softwares • Telescope control: Autoslew control. soft. (P. Keller) • Camera/filter control: MaxImDL imaging softw. • Dome control: DomeControl soft. (Nikola & Laza)

  14. ASV: Observation • Setup the accurate time • Waits the sunset (using TheShy6 planetary program) • Takes 5 FF frames with 5sec exposures in each band with highest S/N • Takes 10 dark frames with 5sec exposure for making master flat • Takes 10 bias frames for master bias • Takes 10 dark frames with 180sec exposure for scalable master dark Calibration module • AutomatizedinVisual Basic Scripting language Master frame module - Makes master bias, dark and flat frames • Chose the object which has an observable minima on that day • Slew the telescope to the object • Checks the FOV and correct it if needed • Automatically finds the optimal exposure time for each filter Pre-observation module LOOP -Makes an exposure -Calibrates the images -Do photometry on the fly - corrects the exposure time if needed -Check RA, DEC and correct if there is a shift NEXT Observation module

  15. ASV: VBScript output So far we have minima of 3 objects: 1. HAT-192-0001841; Vmax=14; I band; texp=45s; S/N=254; no binning 2. HS 2231+2441; Vmax=14; V band; texp=23s; S/N=79; with binning 3. NSVS 14256825; Vmax=13.2; V band ; texp=23; S/N=180; with binning Final reduction, calibration and photometry is performed in the IRAF package • HAT-192-0001841 • Binary system: K+M dwarfs • Observed in I band • Without binning • Vmax = 14 mag • P ~ 0.31 day • m ~ 0.6 mag • ~ 0.02 mag This project is the first automatized project in Serbia astronomy

  16. ASV: Our experience • Our experience shows that there are at least 3 negative effects for observation: 1. Shutter delay: affects the timing of the minima 2. Shutter effect: affects the LC 3. Non-linearity of the CCD : affects the LC

  17. ASV: Our experience • Shutter delay: is a result of finite time for shutter to START to open e.g. ALTA Apogee E47 has 0.42 sec delay e.g. ALTA Apogee U42 has nearly 0 sec delay Consequently: OBS-TIME written in the image header is not the true one Opinion: Each DWARF member should test their CCD for this effect and correct it if needed

  18. ASV: Our expirience 2. Shutter effect: is a result of a finite time for shutter to open and close – it is not instant event but it is a process e.g. FF with 0.02s (still present for 3sec exposure time) When to wary?: FF frames are usually taken with 1-5 sec where the effect is still severe Consequence: Calibration and photometry is incorrect Opinion: Small exposures should be avoided or to correct for this effect

  19. ASV: Our experience 3. Non-linearity: for instance, if we want 0.01 photometric precision we need to be within 1% of the linarity range with both, Comp and Variable star e.g. ALTA Apogee U42 is linear 3000-47000

  20. ASV: How can 1.5m telescope help in this project? Theory: Expected precision of the minimum N-number of the sampling points; A-aperture size Practice: We can calculate the recommended texp for a given telescope, CCD, and star brightness combination in order to achieve the required precision

  21. ASV: How can 1.5m telescope help? Our case: in order to achieve t < 1s, the program stars can be rawly divided into 4 groups: 30s, 60s, 120s, 240s However: there are problematic cases: - faint stars producing small S/N - stars observed in I band (CCD is ~20% less sensitive then in V band) Solution: -binning can help in some cases (faster readout, greater S/N) - Larger aperture (greater S/N, better sampling)

  22. Conclusions • Serbia became eligible to be a part of nice observational projects like DWARF with the 60cm telescope • 1.5m telescope will improve the current position in the observation

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