Am/Fm

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Am/Fm STARS
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General properties
Teff gt 6100 K (o Leo) Teff lt about 10000 K
(transition area to HgMn stars) Main sequence
stars Slow rotation vsini lt 90 km/s Often in
binary systems about 80 of Am stars are in
binary systems.
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Peculiarities
Underabundant C, N, O, Ca, Sc Overabundant Fe-p
eak elements, Y, Ba, rare earths.
The slow rotation switches on the diffusion
processes that lead to the peculiar abundances.
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What do we observe?
The observed abundances reproduce quite well the
predictions of diffusion models
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More on diffusion
When the rotational velocity goes below 90 km/s
the Helium goes deep into the atmosphere. It goes
down in a time dependent on the inverse of the
rotational velocity. It settles at a depth
dependent on the rotational velocity. The limit
is 90 km/s.
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More on diffusion
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More on diffusion
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More on diffusion
2.5P1Vsurf50km/s with anisotropy 2.5P2Vsurf15k
m/s with anisotropy 2.5P3Vsurf50km/s without
anisotropy
Peculiarities are dependent on rotational
velocity!!
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More on diffusion
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What do we observe?
Elements underabundant in Am stars increase their
abundance with increasing of vsini, till the
cluster mean.
Apparently it does not work with Sc, but it
should. Why?
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What do we observe?
Elements not peculiar do not show any trend with
vsini, as expected.
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What do we observe?
Elements overabundant in Am stars decrease their
abundance with increasing of vsini, till the
cluster mean.
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What do we observe?
Same properties as seen before Fe is an
indicator of peculiarity, that is vsini
dependent, so we find the same structure as
before.
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What do we observe?
No clear trend with mass and fractional age
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Velocity fields
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Line profiles and bisectors

• Weak lines reproduced reasonably well
• Strong lines line cores agree with observations,
  but wide wings and strong asymmetry are not
  predicted by the model
• Bisectors small span, weak blue asymmetry

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Line profiles and bisectors

• Weak lines reproduced reasonably well
• Strong lines line cores agree with observations,
  but wide wings and strong asymmetry are not
  predicted by the model
• Bisectors small span, weak blue asymmetry

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Velocity fields
High microturbulence velocity to compensate the
increase of equivalenth width due to the
distorted blue wing. The distortion is increasing
with the depth of the line.
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Velocity fields
We have taken 1371 HARPS spectra of 32 Aqr from
the ESO archive (Carrier et al. 2007) R about
120000 SNR each spectrum between 100 and 300 at
5300Å We have radial velocity shifted all the
spectra according to the orbital elements of the
binary system We have add all these spectra to
obtain one single spectrum with a SNR about 1000
with this result
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Velocity fields
32Aqr R120000, 65000, 45000, 30000
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Velocity fields
32Aqr vsini1, 5, 10, 15 km/s
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What would be very nice to have?
Quick method to detect Am stars
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Two open questions
Line profile in cool slow rotating Am stars
What is happening at the transition region with
HgMn stars
alpha Andromedae Kochukhov et al. 2007