Emily AliceaMuoz

1
HD 101065 Przybylskis Star
Astro 530 28 / April / 2004

• Emily Alicea-Muñoz
• Justin Crepp
• Anand Narayanan

Sample portion of the spectrum of HD 101065 and
automatic fit (thin line) (Cowley Mathys.
1998. AA, 339, 165)
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Where is Przybylski?

• Antoni Przybylski deceased (1984)

• HD 101065 (SIMBAD)
• Centaurus ? RA, DEC (2000.0) 11 37 37.0, -46 42
  34.9
• Parallax 7.95 1.07 mas
• mV 8.01 mag
• vr 10.2 km/s
• Proper motion -47.30, 33.93 mas/yr

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Properties of HD 101065

• Spectral Type (SIMBAD says B5p)
• F0p V (Wegner Petford. 1974. MNRAS, 168, 557)
• F8 (Przybylski. 1977 MNRAS, 178, 735)
• roAp (Cowley et al. 2000. MNRAS, 317, 299)
• Teff (SIMBAD says 16 000 K)
• 7000 K (Wegner Petford 1974)
• 6040 100 K (Przybylski 1977)
• 6500 8000 K (Cowley et al. 2000)
• Visual variable P 12.14 min, amplitude 0.012
  mag (Shavrina et al. 2003. AA, 409, 707)
• Slow spectral variations 23yr (Wegner Petford
  1974)
• Strong magnetic field of 2200 Gauss (Wolff
  Hagen. 1976. PASP, 68, 119)

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The unusual abundances

• Spectrum dominated by rare earth elements (REE)
• Lots of Ho no Fe (Przybylski 1961)
• Li, Sc, Ti, V overabundant (different from other
  Ap stars) Sr, Y, Zr, Mo overabundant (compared
  to solar) by 4 dex no Pm, U, Th (Wegner
  Petford 1974)
• Fe II, Cr II, Ti II, Mn II in UV spectrum
  (ll1200-3200) SED break at 1/l 5.6 mm-1
  (Wegner et al. 1983. ApJ, 272, 646)
• La II, Ce II, Nd II, Sm II, Gd II, Dy II, Er II
  extraordinarily well represented Fe I-II, Ti
  I-II, Co I, Cr I-II present in low abundances no
  Tc, Pm near solar for Na, Si, S deficient in C,
  O heavy blending for Mg (Cowley et al. 2000)

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Figure from Wegner et al. (1983)
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Figure from Cowley et al. (2000)
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Where did the REE come from?

• Two favored theories
• Diffusion (Michaud. 1970. ApJ, 160, 641)
• Radiative levitation of heavier metals (Mn, Sr,
  Y, Zr and rare earths)
• Normally abundant elements in the upper layers of
  the atmosphere sink and settle at the bottom of
  the atmosphere (thus the observed lower
  abundances)
• Magnetic accretion (Havnes Conti. 1971. AA,
  14, 1 Wegner Petford 1974)
• Star encounters ions from the ISM
• Lighter ions get deflected heavier ions get
  entangled in B-field, then fall to the stellar
  surface
• Could lead to magnetic breaking and explain slow
  spectral variations

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Model atmosphere and opacity issues 1

• Matching observed spectrum to atomic data nearly
  impossible (need transition frequencies and
  oscillator strengths for all rare earths and
  ions)
• Model calculations difficult ? controversy over
  Teff
• Increased effect of line opacity alters
  atmospheric structure, thus making standard
  Kurucz models inadequate
• Most recent atmospheric model (Cowley et al.
  2000) ? solar abundances with iron-peak elements
  (Fe, Co, Cu, Mn, Ni) enhanced by 1-2 dex to
  simulate missing line opacities due to lack of
  atomic data for REE

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Model atmosphere and opacity issues 2

• Calculation of pressure stratification affected
  by abnormal chemical composition due to
  relatively cool temperature
• For a cool star, the presence of heavy elements
  imply a larger continuum absorption coefficient
  and a shorter geometrical penetration of the
  line-of-sight into the atmosphere
• Gas pressure goes down electron pressure goes up

• More problems with abundances neutrals vs ions
• Observed ? neutrals dominate over singly and
  double ionized species
• Derived ? doubly ionized exceeds singly ionized
  and neutrals (e.g. Pr III gt Pr
  II, Pr I by 1.6 dex)
• Cannot be explained by uncertainty in oscillator
  strengths or isotopic shifts

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Conclusions

• Lot of effort gone into determining basic
  atmospheric parameters (e.g. Teff)
• Complete model has yet to be created
• Theories to explain abnormal abundances not
  satisfying
• Need to find more stars with similar chemical
  composition (twins of Przybylskis star)
• HR 465 shows rare earth lines including Pm
  (element not present in HD 101065)
• Ciardullo effect???