1. New perspectives on B star X-ray emission: The high-resolution X-ray spectra of Spica and β Cen

2. Collaborators on both projects: –Nathan Miller –Joe Cassinelli β Cen –Ton Raassen –Emre Tepedelenlioglu –Rolf Mewe Spica –Ron Reynolds –Joe MacFarlane –Nate Hall

3. Main Question: Where and how do B stars produce their X-rays? Three approaches: –Line profiles – broadened or not? –Line ratios from He-like ions –Is X-ray flux affected by β Cep-type pulsations

4. Stars’ Biographical Details Beta CenSpica Spectral TypeB1 IIIB1 IV Vinf (km/s)16401750 Mdot (Msun/yr)2.7x10 -8 1.0x10 -8 β Cep Period (d)0.157 d0.1738 d SatelliteXMMChandra InstrumentRGS/MOS/PNACIS-S/LETG

5. β Cen XMM spectra

6. Spica LETG-ACIS-S spectrum

7. 1. Emission Line Profiles

8. Profiles of CVI line of β Cen

9. Spica Line Profiles (vs. scaled Capella in red) (Capella Aa (the main X-ray source) had v ≈ +25 km/s during the observation shown here (Ishibashi & Dewey 2005)

10. 2. f/i Ratios from He-like Ions

12. f/i ratios for β Cen (Kurucz model)

13. Spica’s Ne IX fir region

14. Spica’s O VII fir region

15. Density falloff in Spica’s wind Critical Densities Marked: Radiation will control f/i ratio

16. Interpreting Spica’s f/i ratios (Hubeny model)

17. Interpreting Spica’s f/i ratios (Kurucz model – calc by MacFarlane)

18. -H II region is relatively isolated -Will use to measure ionizing flux and calibrate photospheric FUV/EUV flux which effects f/i ratios Spica’s H II region (Wisconsin H-Alpha Mapper (WHAM) image)

19. 3. X-ray Lightcurves

20. β Cen Lightcurves: 3 XMM instruments

21. β Cen – folded on β Cep period

22. Spica β-Cep-Type History Seen as β Cep variable by Shobbrook et al. (1969) with p=0.1738 d (pulsations evident in archived observations) Photometric variations died out by 1972 (Lomb 1978) May still be pulsing, but axis of NRP may have processed so that we are observing pole-on (Balona 1985) (precession period 130-140 yrs) (Dukes 1974)

23. Spica’s X-ray Lightcurve

24. Spica data folded on β Cep period

25. Conclusions: X-ray emission lines are not strongly Doppler-broadened in either case He-like ions indicate X-rays formed at a range of radii (at least for Spica) No evidence is found for either star to be variable in X-rays on their β Cep periods