Yaël Nazé (Liège University), Nolan R. Walborn (STScI), and Maxime Spano (Geneva Observatory)
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Transcript of Yaël Nazé (Liège University), Nolan R. Walborn (STScI), and Maxime Spano (Geneva Observatory)
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)
Conti Vreux
Outline of the talk
Of?p, a long story…
• HD108
• HD191612
• HD148937
• Others…
• Conclusions
Of?p, what is that for a spectral type ?
• The Of?p zoo : – introduced by 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
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?”
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
?
?
?
?
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 !
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 )
HD108 too !
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 !
40%
New XMM observation taken at the same phase in the LPV cycle, but at +1.6 in orbital phase
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)
– Additional monitoring with Coralie– Amplitude of variations from H to H– HeI5876 also variable !– Period of ~7d confirmed !
– What about the photometry ?
- May 8
- May 12
- May 15
- May 20
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
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
Of?p, unsolved mysteriesQuestions 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 ?
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 »
Concluding remarks by the president : « you did convince me, I temporarily maintain my scenario »
Astronomy is a serious affair…
but doing it in Belgium has advantages…
Rendez-vous in 2010 !