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High Accuracy Atomic Physics In Astronomy. COOL STARS and ATOMIC PHYSICS. Andrea Dupree. Harvard-Smithsonian CfA 7 Aug. 2006. OUTLINE. How does atomic physics influence our understanding of the atmospheres of cool stars ??? Three critical examples:

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High Accuracy Atomic Physics

In Astronomy



Andrea Dupree

Harvard-Smithsonian CfA 7 Aug. 2006



How does atomic physics

influence our understanding

of the atmospheres of cool stars ???

Three critical examples:

1. Identifications temperatures

2. Wavelengths dynamics

3. Coll. X-sections densities

Will draw from highly ionized species characteristic of 10MK, to singly ionized atomsobserved in cool star spectra….



Cool , extended

Giant stars



identification of ions allows emd
Identification of Ions allows EMD

Emission Measure distributions quite different from

the well-known solar case (Sanz-Forcada et al. 2004)

highly ionized species
Highly Ionized Species

FUSE spectra of cool stars show Fe XVIII at 974.86A.

Identified in solar flare spectra.

Feldman and Doschek 1991

Young et al. 2001

Dupree et al. 2003

Redfield et al, 2003.

radial velocity of fe xviii emission lines
Radial Velocity of Fe XVIII emission lines …

Reveals coincidence of Fe XVIII with

the stellar photospheric velocities ,

Suggests that high T plasma,

6.8 K (dex) is anchored close

to the stellar surface reminiscent

of low-lying coronal loops…

high temperature species anchored in warm wind
High Temperature Species Anchored in Warm Wind



FUSE Cool Star Team;

Redfield et al. 2003

symbiotic star ag dra
Symbiotic Star: AG Dra

This stellar system consists of a

red giant whose wind and surrounding

nebula is photoionized by a hot white

dwarf companion. Spectrum is complex

with narrow nebular emission, and the

surprising presencs of high ionization

forbidden lines. These conditions are

quite different from ‘coronal’ plasmas


HST/STIS spectra reveal

forbidden lines: Ca VII, Fe VII, Mg V,

Mg VI, Si VII, and for the first time,

2 transitions of Mg VII between terms

of the 2s 2 2p 2 3P-1D configuration

(Young, P. et al. 2006).

energy levels and density diagnostics
Energy levels and density diagnostics

Separation of ground 3P levels

(from IR astronomical spectra)

plus UV wavelengths define

1D energy levels in Mg VII

Four density diagnostics using

Mg ion ratios do not give consistent results,

although the electron density appears to be high.

High ionization appears to require nearby source

of photoionization. Other problems remain that

might be resolved by detailed modeling.

(Young et al. 2006)

euv spectra offer many coronal diagnostics
EUV spectra offer many coronal diagnostics

Spectra from the EUVE

satellite contain ions


allow both T and Ne to

be defined in cool star


(Sanz-Forcada et al. 2003)

density diagnostics suggest small coronal structures
Density diagnostics suggest small coronal structures

Electron densities are high.

The observed line flux in

combination with the density

diagnostic suggest small

emitting volumes (<0.01 R)

and continuous heating.

FLUXobs ~ Ne 2 ΔV

Sanz-Forcada et al. 2004

euv radiance spectrum of the sun
EUV radiance spectrum of the Sun

CHIPS EUV spectrum

of the whole Sun reveals

differences from the

standard solar irradiance

models (red line).

Courtesy of M. Hurwitz


fluorescent processes in extended atmospheres
Fluorescent processes in extended atmospheres

Betelgeuse – a supergiant

Imaged in the ultraviolet by HST

Dupree and Brickhouse 1998

Narrow lines appeared in emission in far UV (ORPHEUS) spectra

of cool giants and supergiants near 1140Ǻ. Possibly fluorescent

lines from low ionization species.

higher resolution led to confirmation
Higher resolution led to confirmation

Fe II can be produced by H-Lyman-α pumping from

4s a4D and cascade to 4s a6D and 3d7 a4F.

May provide an indirect diagnostic of stellar Lyman-α profile .

Harper et al (2004) hypothesized that Fe II lines away from

H-Ly α (Δλ > 1.8Ǻ) should be weak (marked by *).

fuse spectra show puzzling differences
FUSE Spectra show puzzling differences

FUSE spectra of luminous stars do not show consistent patterns.

(Dupree et al. 2005)

unresolved problem c iii profiles
Unresolved Problem: C III profiles

Profiles of the C III 1176Ǻ line

3P-3P, in luminous cool stars differ

substantially from the solar profile.

Check center to limb behavior.

(Dupree et al 2005)