1. Observational properties of pulsating subdwarf B stars. Mike Reed Missouri State University With help from many, including Andrzej Baran, Staszek Zola, Michal Siwak, Waldek Ogloza.

2. Views of 3 pulsating sdB stars Each with different properties. We wish to understand them and determine how they resemble other pulsating sdB stars.

3. Connecting to a larger picture: What can we learn using Asteroseismology? *Stellar evolutionary timescales *Cosmochronology *Stratifying of stellar interiors *Stellar crystallization *Nuclear fusion cross sections *Masses, radii, and luminosities of stars (distance scales and population synthesis) *Diffusive processes *Convection *Neutrinos *Elementary particle physics *Helium flash *radiative levitation *binary evolution *Type I supernovae *Mass exchange and loss *Stellar magnetism *Interstellar enrichment *Electroweak theory *Core/Envelope ratios *semiconvection *Stellar equations of state *Stellar winds *Lollypop to Popsicle ratio.

5. A Radial Pulsator: l=0 The entire surface changes.

6. A Nonradial Pulsator: l=1 1 line across the surface.

7. A Nonradial Pulsator: l=2 2 lines across the surface.

8. But when many are combined.... It is hard to distinguish the mode.

9. First Goal: Determine the spherical harmonics of pulsation frequencies to constrain models.

10. Mode Identification Methods Traditional: Frequencies and spacings: Feige 48 Binary interactions: PG1336-018

12. Feige 48 Observed over several years and from multiple campaigns.

13. Triplet

15. Our Model Solution: Total Mass: 0.4725 M solar Shell Mass: 0.0025 M solar T eff =29635 K (29,500+/-500) log g = 5.518 (5.50+/-0.05) Near core He exhaustion (0.74% by mass) Predicted a rotation period near 0.4 days, which was detected the following year.

16. Binary sdB pulsator PG1336-018: Observed by WET in 1999 and 2001

17. Binary Period is ~2.4 Hours The companion (~M5V) contributes little light to the integrated flux. i=81 o

18. PG1336-018 Over 20 Pulsation Frequencies Detected within 2500 mHz ➢ 2.4 hour orbital period. ➢ Tidal forces are comparable to Coriolis force

19. Effects to look for. ➢ Eclipse Mapping ➢ Tidal Influence on Pulsations

20. Eclipse Mapping

21. l=1, m=1

23. PG1336-018 An ideal case! ~15 minute eclipses covering ~60% of the pulsator.

24. Eclipse data for PG1336 ➢ All the in-eclipse modes are new! (Except for 2.) ➢ But not where we expect them to be from splittings seen in the OoE data. ➢ Most modes are splittings away from OoE modes. Results: PG1336 eclipses do not map pulsations as we expect.

25. Tipped Pulsation Axis (Tidal Influence on Pulsations)

26. A tipped pulsation axis? ➢ Tidal forces exceed Coriolis force. ➢ Pulsation axis will point at companion- similar to roAp stars. ➢ Orbital motion will precess the pulsation axis, completing one revolution every couple hours.

27. l=2, m=1

30. Each tipped pulsation mode has 3 signatures. ➢ Number and separation of peaks in the combined FT ➢ Predictable regions of like phase. ➢ If divided into regions of like phase, a central peak should show up.

32. And what did we really see?

35. Nothing new and/or exciting.

37. Here is one!

39. What have we learned? 1 good and 1 mediocre l=1, m=1 identifications. 1 reasonable l=2, m=0 identification. 1 reasonable l=2, m=1 identification. On to the models for PG1336!

40. PG0048: An unexpected surprise!

41. Every night, something new!

43. Detected a total of 29 frequencies. But only 1 of them is detected in every good-quality run.

46. Signatures of stochastic oscillations: *Highly variable amplitudes. *Sometimes (or often) damped below detectability *Combinations of data have reduced amplitudes (because of phase differences)

47. Simulations of stochastic oscillations

48. Best fit results for PG0048: A damping timescale if 4 – 6 hours and a re-excitation timescale of 13 – 19 hours.

49. Results: Feige 48 solved using traditional methods. PG1336 shows indications of inclined pulsation axis which can constrain models. PG0048 shows indications of stochastic oscillations.