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The Triple System of DG Leo: A Universe of Surprising Phenomena

Explore the intriguing physical phenomena within the triple system of DG Leo, with detailed orbit analyses, astrophysical relevance, and future research goals. Uncover the unique characteristics of this system's components and delve into the pulsational properties of twin systems for a rewarding comparative study.

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The Triple System of DG Leo: A Universe of Surprising Phenomena

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  1. DG Leo : a triple system with a surprising variety of physical phenomena P. Lampens,Y. Frémat & H. Hensberge, Royal Observatory of Belgium, Brussel, Belgium V. Tamazian, J.A. Docobo, Observatorio Astronómico R. M. Aller, Santiago de Compostela, Spain Y. Balega, Special Astrophysical Observatory, Russia Garching (ESO) - Multiple stars across the HR diagram

  2. Outline • Part I: Introduction • 1.1 The goal • 1.2 The target • Part I: Astrophysical relevance • 2.1 The close binary • 2.2 The visual binary • Part II: Orbit analyses • 3.1 New astrometric orbit • 3.2 New combined orbit • 4.Future work Garching (ESO) - Multiple stars across the HR diagram

  3. I. Introducing the project • Goal of the current project: In-depth study of a pulsating star in a binary or multiple system • Binarity/multiplicity provides “added value” wrt. the component’s physical properties in a straight-forward, independent way • Binarity/multiplicity allows to “discard” the shared characteristics between the components (distance, environment-e.g.overall chemical composition- and age) • Comparative study of the pulsational properties between components of “twin systems” is most rewarding •  Principal target = DG Leo Garching (ESO) - Multiple stars across the HR diagram

  4. 1.2 Introducing DG Leo HD 85040 = HIP 48218 = Kui 44AB Aab = inner binary (SB2) Porb1 ~ 4.15 days AB = outer binary (SB2-VB) Porb2 ~ 100-150 yr near periastron (2003) Fig. 1 The hierarchical triple system DG Leo 3 nr identical components (A8/F0 IV-III) all   Sct instability strip (+Am) (Fekel & Bopp ’77; Frémat et al. ’05) Garching (ESO) - Multiple stars across the HR diagram

  5. 2.1 The close binary Aab • Aab system: Porb= 4.15 days • From the photometry: • tidal interaction (pure ellipsoidal variation - no net “reflection”) • no eclipses (iorb<73º)*  MAa = MAb > 2.0 M • (Rosvick & Scarfe ’91; • Lampens et al. ’05) Aa Ab Fig. 2. The close binary in DG Leo A Garching (ESO) - Multiple stars across the HR diagram

  6. 2x Max 2x Min Garching (ESO) - Multiple stars across the HR diagram

  7. JD = 2452312.709 Phase = 0.748 T Min Ab Aa Aa JD = 2452313.746 Phase = 0.498 T Max Ab No phase lag between light and RV Garching (ESO) - Multiple stars across the HR diagram

  8. 2.1 The close binary Aab • From the spectroscopy: • (high S/N spectra from ELODIE@OHP, France) • spectral disentangling method(Hadrava 1995) • component spectra • comp radial velocities • (Fekel & Bopp ’77; • Frémat et al. ’05) Aa Ab Fig. 2. The close binary in DG Leo A Garching (ESO) - Multiple stars across the HR diagram

  9. Underabundance Overabundance Fe Ni Ti 5030 Sc II Chemical composition: comp Ab HD 33959 A9 IV V sin i = 29 km/s HD 88849 A7m V sin i = 29 km/s Ab Garching (ESO) - Multiple stars across the HR diagram

  10. 2.2 The visual binary AB • AB pair: Porb ~ 100–150 yr • Abrupt changes in Vr,A • & Vr,B observed (Jan.’03) • First orbit computation; confirmation of high i and e(Frémat et al. 05) •  possibility for deriving all 3 component masses… B Fig. 4. The distant companion DG Leo B Garching (ESO) - Multiple stars across the HR diagram

  11. 2forb f1, f2, f3, f4 (at least) 1 comp is multiperiodic  Sct variable Garching (ESO) - Multiple stars across the HR diagram

  12. Start of night 7 Pulsation: comp B Mean CCF Aa B Ab Garching (ESO) - Multiple stars across the HR diagram

  13. Start of night 5 Pulsation: comp B Mean CCF Ab B Aa Garching (ESO) - Multiple stars across the HR diagram

  14. Underabundance Overabundance Fe Ni Ti 5030 Sc II Chemical composition: comp B HD 33959 A9 IV V sin i = 29 km/s HD 88849 A7m V sin i = 29 km/s B Garching (ESO) - Multiple stars across the HR diagram

  15. Fundamental component parameters Garching (ESO) - Multiple stars across the HR diagram

  16. II. First (astrometric+RV) orbit (Frémat et al., 2005) Obtained with VBSB2 (global exploration of the parameter space followed by simultaneous LSQ minimiz.) (Pourbaix 1998) B A However ambiguities on KA, KB reflect on the true semi-major axes aA, aB and on the masses MA, MB Garching (ESO) - Multiple stars across the HR diagram

  17. 3.1 Improved astrometric solution (Docobo & Tamazian, submitted) A new speckle datum at epoch 2004.99 i.e. after periastron passage (6m tel@SAO) leads to: Garching (ESO) - Multiple stars across the HR diagram

  18. 3.1 Improved astrometric solution • Solution 1(Porb=101 yr) • Based on Docobo (1985) • Best agreement for all astrometric data (n=91) • Smaller errors • Efficiency = 0.10 (Pourbaix & Eichhorn 1998) Using Hipparcosparallax System mass ~ 3 M ?! Garching (ESO) - Multiple stars across the HR diagram

  19. 3.2 Combined orbital solution Including new speckle datum after periastron: New Previous (Frémat et al., 2005) (this work) Garching (ESO) - Multiple stars across the HR diagram

  20. 3.2 Combined orbital solution • Solution 2 (Porb=113 yr) • Based on Pourbaix (1998) • Incl. Vr,A and Vr,B • Excellent agreement for interferometric data only (n=41) • Efficiency = 0.16 Garching (ESO) - Multiple stars across the HR diagram

  21. 3.2 Combined orbital solution • Solution 2 (Porb=113 yr) • Includes VrA and VrB • All data (n=111) • Efficiency = 0.32 (x 2) • System parameters hold orbital parallax •  Hipparcos parallax butonlyat 1.5 σ-level (and σπ/π= 15%) B A Using orbitalparallax System mass  6 M ! Garching (ESO) - Multiple stars across the HR diagram

  22. Using Hipparcos parallax: (m-M)=-5-5.log(πHIP) Using the orbital parallax: (m-M)=-5-5.log(πOrb) Schaller et al. 2002 (Z=0.02) Garching (ESO) - Multiple stars across the HR diagram

  23. 4. What is (still) needed ? • Very high-accuracy astrometry to resolve the close binary system Aab (VLTI) for orbital inclination & accurate dynamical masses (2 mild Am) • (Very) high-accuracy astrometry to improve the system parameters/orb. parallax of AB pair (VLTI3-4m tel) for accurate third component mass(δSCT) • Additional high-S/N spectroscopy for pulsation mode identification (multi-colour photometry, line profiles, modelling)  New insights for understanding the link between pulsation - chemical composition (diffusion) - multiplicity Garching (ESO) - Multiple stars across the HR diagram

  24. To be (hopefully) cont’d Garching (ESO) - Multiple stars across the HR diagram

  25. Pulsation: comp B Night 8 • DG Leo B is a multiperiodic, small-amplitude Delta Scuti pulsating star ! Night 7 Night 6 Night 5 Garching (ESO) - Multiple stars across the HR diagram

  26. Am binaries in general • Binary frequency > 50 %(North et al. ‘98) • Orbital period distribution(Debernardi et al. ‘00) • Circularization period(Debernardi et al. ‘00) • Spin-orbit synchronization(Abt, Levato et al. ‘02) Fig. R. The (e, log P) distribution of Am binaries Fig. L. Orbital period distribution of Am bin. from CORAVEL survey Garching (ESO) - Multiple stars across the HR diagram

  27. Using the orbital parallax: (m-M) = -5 -5.log (πOrb) Schaller et al. 2002 (Z=0.02) Garching (ESO) - Multiple stars across the HR diagram

  28. Using Hipparcos parallax: (m-M)=-5-5.log(πHIP) Schaller et al. 2002 (Z=0.02) Garching (ESO) - Multiple stars across the HR diagram

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