1 / 39

HIGH-PRECISION PHOTOMETRY OF ECLIPSING BINARY STARS

HIGH-PRECISION PHOTOMETRY OF ECLIPSING BINARY STARS. John Southworth + Hans Bruntt + Pierre Maxted + many others. Eclipsing binary stars: why bother?. Eclipsing binary stars: why bother?. Light curve and radial velocity analysis: get masses and radii of two stars to 1%

curran-bradshaw
Download Presentation

HIGH-PRECISION PHOTOMETRY OF ECLIPSING BINARY STARS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. HIGH-PRECISION PHOTOMETRY OF ECLIPSING BINARY STARS John Southworth + Hans Bruntt + Pierre Maxted + many others

  2. Eclipsing binary stars: why bother?

  3. Eclipsing binary stars: why bother? • Light curve and radial velocity analysis: get masses and radii of two stars to 1% • where else could we get this from?

  4. Eclipsing binary stars: why bother? • Light curve and radial velocity analysis: get masses and radii of two stars to 1% • where else could we get this from? • Accurate mass, radius, Teff, luminosity • use as high-precision distance indicators • check that theoretical models work

  5. Eclipsing binary stars: why bother? • Light curve and radial velocity analysis: get masses and radii of two stars to 1% • where else could we get this from? • Accurate mass, radius, Teff, luminosity • use as high-precision distance indicators • check that theoretical models work • Comparison with theoretical models • get metal abundance and age • investigate overshooting, mixing length, helium abundance, diffusion

  6. Eclipsing binary stars: how? WW Aurigae – Southworth et al. (2005)

  7. Eclipsing binary stars: how? • Light curve analysis gives: • rA rB radii as fraction of orbital separation • e ω orbital eccentricity and periastron longitude • P i orbital period and inclination

  8. Eclipsing binary stars: how? WW Aurigae – Southworth et al. (2005)

  9. Eclipsing binary stars: how? • Light curve analysis gives: • rA rB e ω P i • Radial velocity analysis gives: P e ω • MA sin3i minimum mass of star A • MB sin3i minimum mass of star B • a sin i projected orbital separation

  10. Eclipsing binary stars: how? • Light curve analysis gives: • rA rB e ω P i • Radial velocity analysis gives: • MA sin3i MB sin3i a sin iP e ω • Combine quantities: • MAMBRA RB log gA log gB • get the masses and radii of both stars

  11. Eclipsing binary stars: how? • Light curve analysis gives: • rA rB e ω P i • Radial velocity analysis gives: • MA sin3i MB sin3i a sin iP e ω • Combine quantities: • MAMBRA RB log gA log gB • get the masses and radii of both stars • Spectral modelling or photometric colours: • get effective temperatures • get luminosities • get distance

  12. The WIRE satellite • Launched in 1999 for an IR galaxy survey • electronics problem caused loss of coolant

  13. The WIRE satellite • Launched in 1999 for an IR galaxy survey • electronics problem caused loss of coolant • Star tracker used since 1999 as a high-speed photometer • aperture: 5 cm • cadence: 2 Hz • 5 targets at once

  14. Eclipsing binaries with WIRE. I. ψ Centauri • V = 4.0 spectral type = B9 V + A2 V • Known spectroscopic binary • WIRE light curve: 41 000 points with 2 mmag scatter

  15. Interlude 1: JKTEBOP • Based on EBOP model (Paul Etzel, 1975) • stars treated as biaxial spheroids • numerical integration includes LD and GD

  16. Interlude 1: JKTEBOP • Based on EBOP model (Paul Etzel, 1975) • stars treated as biaxial spheroids • numerical integration includes LD and GD • JKTEBOP retains original model • new input / output • Levenberg-Marquardt optimisation algorithm • bootstrapping and Monte Carlo simulations to find parameter uncertainties http://www.astro.keele.ac.uk/~jkt/codes.html FORTRAN77

  17. Eclipsing binaries with WIRE. I. ψ Centauri • JKTEBOP fit to the eclipses

  18. Eclipsing binaries with WIRE. I. ψ Centauri • Best fit and Monte Carlo simulation results: • rA = 0.043984 ± 0.000045 • rB = 0.021877 ± 0.000032 • e = 0.55408 ± 0.00024 • P = 38.81252 ± 0.00029 • And limb darkening too: • uA = 0.256 ± 0.009 • uB = 0.362 ± 0.041

  19. Eclipsing binaries with WIRE. I. ψ Centauri • Best fit and Monte Carlo simulation results: • rA = 0.043984 ± 0.000045 • rB = 0.021877 ± 0.000032 • e = 0.55408 ± 0.00024 • P = 38.81252 ± 0.00029 • And limb darkening too: • uA = 0.256 ± 0.009 • uB = 0.362 ± 0.041 • See Bruntt et al. (2006, A&A, 456, 651) • We are currently working on new spectroscopy

  20. Eclipsing binaries with WIRE. II. AR Cas • P = 6.07 days B4 V + A6 V V = 4.9 • variation at primary star rotation period • several pulsation frequencies

  21. Eclipsing binaries with WIRE. III. β Aurigae • V = 1.9 P = 3.960 days A1m + A1m • First known double-lined binary: 1889 (Maury) • First known double-lined eclipsing binary: Stebbins (1911) • WIRE light curve: 30 000 points; 0.3 mmag scatter

  22. Interlude 2: more JKTEBOP • Problem: linear limb darkening law too simple • Solution: add log, sqrt, quad, cubic LD laws

  23. Interlude 2: more JKTEBOP • Problem: linear limb darkening law too simple • Solution: add log, sqrt, quad, cubic LD laws • Problem: ratio of the radii poorly determined • Solution: allow spectroscopic light ratio to be included directly as another observation http://www.astro.keele.ac.uk/~jkt/codes.html FORTRAN77

  24. Interlude 2: more JKTEBOP • Problem: linear limb darkening law too simple • Solution: add log, sqrt, quad, cubic LD laws • Problem: ratio of the radii poorly determined • Solution: allow spectroscopic light ratio to be included directly as another observation • Problem: difficult to get good times of minimum light from the WIRE data • Solution: include old times of minimum light directly as additional observations http://www.astro.keele.ac.uk/~jkt/codes.html FORTRAN77

  25. Eclipsing binaries with WIRE. III. β Aurigae • rA = 0.1569 ± 0.0008 P = 3.96004673 (17) • rB = 0.1460 ± 0.0008e = 0.0018 ± 0.0004

  26. Eclipsing binaries with WIRE. III. β Aurigae • Combine light curve result with spectroscopic orbit of Smith (1948): • MA = 2.376 ± 0.027 M • MB = 2.291± 0.027 M • RA = 2.762± 0.017 R • RB = 2.568± 0.017 R

  27. Eclipsing binaries with WIRE. III. β Aurigae • Combine light curve result with spectroscopic orbit of Smith (1948): • MA = 2.376 ± 0.027 M • MB = 2.291± 0.027 M • RA = 2.762± 0.017 R • RB = 2.568± 0.017 R • Distance to system: • Hipparcos parallax: 25.2 ± 0.5 pc • Orbital parallax: 24.8 ± 0.8 pc • Surface brightness: 25.0 ± 0.4 pc • Bolometric corrections: 24.8 ± 0.3 pc • Southworth, Bruntt & Buzasi (2007, A&A, 467, 1215)

  28. Eclipsing binaries: why bother? • Get mass and radius to 1% • accurate distance indicators • compare to theoretical models: get precise age and metal abundance

  29. Eclipsing binaries: why bother? • Get mass and radius to 1% • accurate distance indicators • compare to theoretical models: get precise age and metal abundance • Now apply to EBs in open clusters • get accurate distance • get precise age and metallicity • no need for MS fitting

  30. Eclipsing binaries: why bother? • Get mass and radius to 1% • accurate distance indicators • compare to theoretical models: get precise age and metal abundance • Now apply to EBs in open clusters • get accurate distance • get precise age and metallicity • no need for MS fitting • Combined study of cluster and binary • stronger test of theoretical models

  31. Eclipsing binaries in open clusters. I. V615 and V618 Per • Both members of the young h Per cluster • have same age and chemical composition • compare all four stars to models using a mass-radius diagram • h Per has low metal abundance: Z = 0.01

  32. Eclipsing binaries in open clusters. II. V453 Cyg • Member of sparse young cluster NGC 6871 • Comparison to theoretical models: • age = 10.0 ± 0.2 Myr • metal abundance Z≈ 0.01 (half solar – maybe)

  33. Eclipsing binaries in open clusters. III. The distance to the Pleiades • Surface brightness method gives good results • Use zeroth-magnitude angular diameter Φ(m=0) • Kervella et al (2004) give Φ(m=0) - Teff calibrations • Just need RA and RB and apparent magnitudes • See Southworth, Maxted & Smalley (2005, A&A, 429, 645)

  34. Eclipsing binaries in open clusters. III. HD 23642 in the Pleiades • V = 6.8 P = 2.46 AO Vp (Si) + Am • Light curves from Munari et al. (2004) • We find distance = 139.1 ± 3.5 pc

  35. Eclipsing binaries in open clusters: what next? • V1481 Cyg and V2263 Cyg in NGC 7128 • 14 nights of INT / WFC photometry • 7 nights of INT / IDS spectroscopy • watch this space

  36. JKTEBOP and HD 209458 • JKTEBOP very good for transiting exoplanets • fast and accurate • lots of different limb darkening laws

  37. JKTEBOP and HD 209458 • JKTEBOP very good for transiting exoplanets • fast and accurate • lots of different limb darkening laws • Results for HD 209458 • rA = 0.11405 ± 0.00042 • rB = 0.01377 ± 0.00008 • gB = 9.28 ± 0.15 m s-2 • Southworth et al. (2007, MNRAS, 379, L)

  38. Extrasolar planet surface gravity • The known transiting extrasolar planets have a significant correlation between orbital period and suface gravity • the closer planets are more bloated • Southworth et al. (2007, MNRAS, 379, L)

  39. John Southworth jkt@astro.keele.ac.uk University of Warwick, UK

More Related