New perspectives on B star X-ray emission: The high-resolution X-ray spectra of Spica and β Cen
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Transcript of New perspectives on B star X-ray emission: The high-resolution X-ray spectra of Spica and β Cen
New perspectives on B star X-ray emission:
The high-resolution X-ray spectra of Spica and β Cen
• Collaborators on both projects: – Nathan Miller– Joe Cassinelli
• β Cen – Ton Raassen– Emre Tepedelenlioglu– Rolf Mewe
• Spica – Ron Reynolds– Joe MacFarlane– Nate Hall
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
Stars’ Biographical Details
Beta Cen Spica
Spectral Type B1 III B1 IV
Vinf (km/s) 1640 1750
Mdot (Msun/yr) 2.7x10-8 1.0x10-8
β Cep Period (d) 0.157 d 0.1738 d
Satellite XMM Chandra
Instrument RGS/MOS/PN ACIS-S/LETG
β Cen XMM spectra
Spica LETG-ACIS-S spectrum
1. Emission Line Profiles
Profiles of CVI lineof β Cen
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)
2. f/i Ratios from He-like Ions
f/i ratios for β Cen (Kurucz model)
Spica’s Ne IX fir region
Spica’s O VII fir region
Density falloff in Spica’s windCritical Densities Marked:
Radiation will control f/i ratio
Interpreting Spica’s f/i ratios(Hubeny model)
Interpreting Spica’s f/i ratios
(Kurucz model – calc by MacFarlane)
-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)
3. X-ray Lightcurves
β Cen Lightcurves: 3 XMM instruments
β Cen – folded on β Cep period
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)
Spica’s X-ray Lightcurve
Spica data folded on β Cep period
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