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Yaël Nazé (Liège University), Nolan R. Walborn (STScI), and Maxime Spano (Geneva Observatory)

Conti. Vreux. HD 108 and the Other Peculiar Of?p Stars: Still Puzzling Peter, Jean-Marie, and the Massive Star Community. Yaël Nazé (Liège University), Nolan R. Walborn (STScI), and Maxime Spano (Geneva Observatory). Outline of the talk. Of?p, a long story… HD108 HD191612 HD148937

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Yaël Nazé (Liège University), Nolan R. Walborn (STScI), and Maxime Spano (Geneva Observatory)

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  1. Conti Vreux HD 108 and the Other Peculiar Of?p Stars: Still Puzzling Peter, Jean-Marie, and the Massive Star Community Yaël Nazé (Liège University), Nolan R. Walborn (STScI), and Maxime Spano (Geneva Observatory)

  2. Outline of the talk Of?p, a long story… • HD108 • HD191612 • HD148937 • Others… • Conclusions

  3. Of?p, what is that for a spectral type ? • The Of?p zoo : • introducedby N.R. Walborn in 1972,1973 • principal defining Of?p characteristic:C III 4650 comparable to N III 4640 + narrow emission/PCyg in Balmer lines + asymmetric/PCyg HeI lines + peculiar wind lines in UV • Rare : 3 Galactic objects

  4. HD108 • My first job : • Jean-Marie : “I have a bunch of spectra” • CIII, H lines, HeI lines variable (+ HeII4686) • 4542 cst  apparent ST changes : O4f?p  O8.5fp(Nazé et al. 2001,2004) • Not so new : • Andrillat, Fehrenbach, Swings & Vreux 1973 “Observations recentes du spectre de HD108 (Of)” • Vreux & Conti 1979 “Spectral variations in the Of star HD108: are they periodic?” Yes, with about 55yrs !

  5. HD108 • What is it ? • Binary ? (Hutchings 1975, Aslanov & Barranikov 1989) • Expanding atmosphere ? (Andrillat et al. 1973) • Disc & jets ? (Underhill 1994) • Wind variations ? (Vreux & Conti 1979) • Disc & oscillations ? (Nazé et al. 2001) • Magnetically confined wind ? (Nazé et al. 2001) • XRB ? (Nazé et al. 2001) Prob. not No No ? ? ? ?

  6. HD108 XMM observations from Jean-Marie : • A soft X-ray spectrum (T1=0.2-0.3 keV – dominates!, T2=1-3keV) • Luminous, but log(Lx/Lbol)= –6.1 (Nazé et al. 2004)  Not an XRB !

  7. HD108 too ! HD191612 • Just as HD 108… • Spectral type : O6.5f?p  O8fp • LPV with P=538d • Photometric variations too ! • Binary with P=1540d (Walborn et al. 2003,2004, Nazé et al. 2007, Howarth et al. 2007 )

  8. 40% New HD191612 XMM, again… Nearly identical high-E spectra ! • Soft X-ray spectrum, with only ~30% of flux (0.5-10keV) in the high T • Broad lines (FWHM~1800km/s), overluminosity log(Lx/Lbol)= –6.1 to –6.2 • Variations! less X-rays when less visible emissions & star fainter (Nazé et al. 2007) is it phase-locked ? YES ! New XMM observation taken at the same phase in the LPV cycle, but at +1.6 in orbital phase

  9. - May 8 - May 12 - May 15 - May 20 HD148937 • Not just the same… • Spectral type : O6f?p • Not a binary : Indeed… see Conti et al. 1977 • LPV for HeII4686, H & H • Possible period : ~7d but sampling inadequate (Nazé et al. 2008a,b) New • Additional monitoring with Coralie • Amplitude of variations  from H to H • HeI5876 also variable ! • Period of ~7d confirmed ! • What about the photometry ?

  10. An answer ? • HD 191612 : detection of a magnetic field ! • Zeeman signature in metallic & HeI lines • line-of-sight component : -220 +/- 38 G (Donati et al. 2006) • HD148937 : • Line-of-sight component : -276 +/- 88 G (Hubrig et al. 2008) • What about HD 108 ? HD191612 New

  11. Others… • In the MCs : a few ones were detected (Heydari-Malayeri & Melnick 1992, Walborn et al. 2000, Massey & Duffy 2001)but are they similar to the Galactic ones ? • In the Galaxy : ONE MORE ! CPD-28°2561 (Barba & OWN survey team, 2008, in prep.) • Spectral variations similar to HD191612 • Period not yet identified due to lack of spectra New

  12. Of?p, unsolved mysteries Questions to be answered • Observationally : • Are they all magnetic ? Test HD108 & the new ones ! • What is the magnetic field geometry ? Monitor it ! • Are small-scale variations periodic too ? Make short-term monitoring of HD108 & HD191612 ! • Theoretically : • If LPV period = rotation period, is it possible to brake rotation up to 55yrs, as for HD108 ? • Where does the soft X-ray emission come from ? • Why is HD148937 the only one to have a nebula ? • Where does the strong CIII emission come from ?

  13. Concluding remarks by the president : « you did convince me, I temporarily maintain my scenario » Liege Colloquium 1996 President of the colloquium : « Andre, I am no longer sure my scenario is correct, what should I do ? » A. Maeder : « It’s too late to cancel everything… most of the participants are seated… some of them look agressive »

  14. Astronomy is a serious affair…but doing it in Belgium has advantages…Rendez-vous in 2010 !

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