1. Nov. 6, 2008Thanks to Henrietta Leavitt Cepheid Multiplicity and Masses: Fundamental Parameters Nancy Remage Evans

2. Nov. 6, 2008Thanks to Henrietta Leavitt Outline Multiplicity: Motivation What we know Implications Masses: Motivation What we know Implications

3. Nov. 6, 2008Thanks to Henrietta Leavitt Cepheids 4-7 M  Formerly B stars Young ~50 Myr Post-RGB, core He burning Evolve without strong mass loss of O stars

4. Nov. 6, 2008Thanks to Henrietta Leavitt Multiplicity Star formation Binary, triple,…. Distribution of mass ratios Maximum separation High vs low mass Basis: ground-based orbits

5. Nov. 6, 2008Thanks to Henrietta Leavitt High Mass Companions: IUE Survey Particularly complete binary information Evolved cool stars: sharp lines Hot companions dominate in UV Observed the 75 brightest Cepheids with IUE All companions through early A detected 21% companions Using R V : 34%

6. Nov. 6, 2008Thanks to Henrietta Leavitt Energy Distributions Hot companions Normalized at 1600 A Generally very low reddening Well determined spectral types, mass

7. Nov. 6, 2008Thanks to Henrietta Leavitt Mass Ratios M 2 /M 1 Strong preference for low mass companions Selection: orbital periods longer than 1 year Contrast: binaries with P<40d: equal mass preference (Tokovinin, 2000)

8. Nov. 6, 2008Thanks to Henrietta Leavitt Multiplicity: Completeness Cepheids with orbits 18 observed with IUE => hot companions known Multiplicity? M 2 unknown

9. Nov. 6, 2008Thanks to Henrietta Leavitt UV high res Multiplicity: Completeness High resolution UV spectra (HST, IUE): velocity of companion 8 of 18 5 of 8 are triples

10. Nov. 6, 2008Thanks to Henrietta Leavitt Multiplicity:S Sge Orbit => mass function: M 1, M 2, sin i Mass from IUE spectrum Secondary double S Sge B IUE

11. Nov. 6, 2008Thanks to Henrietta Leavitt Multiplicity: Completeness Cepheids with orbits + companion spectrum 8 (possibly 9) are triple: 44% (50%) Triples

12. Nov. 6, 2008Thanks to Henrietta Leavitt Low Mass Companions? Cepheid companions young Alpha Per Cluster: age of a typical Cepheid Rosat observations: filled symbols are X-ray detections Essentially all stars cooler than F5 V Field stars would not be detected in X-rays

13. Nov. 6, 2008Thanks to Henrietta Leavitt Expectations Low mass companions? Wide companions Expectations (days) Duquennoy and Mayor Cepheid Orbits Solar type

14. Nov. 6, 2008Thanks to Henrietta Leavitt Chandra Observation of Polaris Center 3’ of ACIS-I field Putative components marked A = Aa + Ab B F3 V C, D X-ray but no 2MASS: background AGN

15. Nov. 6, 2008Thanks to Henrietta Leavitt System Summary A = Aa +Ab B (no low mass companion) 2 possible distant stars (0.16 and 0.29 pc) Searched: Magnitude difference of 15 mag Mass ratio range of 10 Separation of 0.1 pc

16. Nov. 6, 2008Thanks to Henrietta Leavitt Polaris A Originally: no full amplitude Cepheid had been detected in X-rays Probability favored Ab dwarf companion BAAS 2009: Engle, Guinan, Evans, and DePasquale X- rays with XMM from 2 other Cepheids X-rays not so good for unresolved low mass companions Cepheid + K companion Very interesting for atmospheric heating

17. Nov. 6, 2008Thanks to Henrietta Leavitt Multiplicity: Results High binary fraction High triple fraction Many small M 2 /M 1 for P > 1 yr Needed: low mass companions? Needed: Cepheid X-rays?

18. Nov. 6, 2008Thanks to Henrietta Leavitt Masses Why? Benchmark for evolutionary tracks Pulsation calculations Problem: mass mismatch Problem: blue loops

19. Nov. 6, 2008Thanks to Henrietta Leavitt Masses: Evolutionary Tracks Luminosity: mass of He burning core Core convective overshoot Rotation Radiative opacity Mass loss

20. Nov. 6, 2008Thanks to Henrietta Leavitt Masses How? Ground-based spectroscopic orbit Double-lined spectroscopic binaries:high resolution UV spectroscopy: orbital velocity amplitude ratio + mass of secondary Astrometric orbit of Cepheid (Benedict, et al.) + mass of secondary Astrometric orbit of both (Polaris)

21. Nov. 6, 2008Thanks to Henrietta Leavitt Masses Evolutionary framework Padua, Geneva tracks: decreasing overshoot from left to right S Mus,V350 Sgr:HST velocities W Sgr, FF Aql: Benedict orbits No overshoot

22. Nov. 6, 2008Thanks to Henrietta Leavitt S Mus Hottest companion GHRS high resolution velocities Temperature

23. Nov. 6, 2008Thanks to Henrietta Leavitt S Mus FUSE spectra Standards reddened to match S Mus H 2 absorption H2H2

24. Nov. 6, 2008Thanks to Henrietta Leavitt S Mus Example S Mus, B3 V B5 V

25. Nov. 6, 2008Thanks to Henrietta Leavitt W Sgr Spectroscopic orbit: 4.3 yr IUE: hot companion: A0 V Small orbital velocity amplitude: face- on? Inconsistent with reasonable Cepheid mass Resolved?

26. Nov. 6, 2008Thanks to Henrietta Leavitt W Sgr B STIS spectrum Component B: resolved, hot Spectroscopic binary: Cepheid Aa + Ab, cool 2800 A 2625 A Ceph +Comp Ab Comp B 0.16”

27. Nov. 6, 2008Thanks to Henrietta Leavitt W Sgr Solid: extracted Cepheid Aa+ Ab spectrum Dashed: Alp Aqr: slightly cooler than Cepheid Ab not detected M Ab < 1.4 M  M cep < 5.4 M 

28. Nov. 6, 2008Thanks to Henrietta Leavitt Eta Aql B9.8 V companion Orbit? Eaton: 1 year

29. Nov. 6, 2008Thanks to Henrietta Leavitt Summary: Pointers to the Future List of orbits: future possibilities Multiplicity: X-rays, (UV) Masses: roadmap