determining stellar properties classical methods · distance –parallax‐parsec 1 ... to.. the...
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Determining Stellar Properties –classical methods
Teff, logg, [Fe/H], Luminosity, Mass, Radius, Age
and their relation to colours
Karsten Brogaard
Colour‐temperature relation
Filters, magnitudes and colours
J. Jessen‐Hansen – Studenter Kollokvium 323‐01‐2014
U B V I
u v b y
IRFM
Spectroscopy – Teff, logg, [Fe/H]
Interferometry
Interferometry
With the measurement of θ we can calculateTeff:
and the stellar radius R if we know the distance D:
R= (θ/2)*D
Distance – parallax ‐ Parsec
1 Parsec = 1 AU/1” = 206265 AU = 4.4e7 Rʘ = 3.09e16 m
D = 1/π , π = parallax in arcseconds
Distance – parallax ‐ Parsec
1 Parsec = 1 AU/1” = 206265 AU = 4.4e7 Rʘ = 3.09e16 mD(Parsec) = 1/π , π = parallax in arcseconds
Distances in the universe:To..the math canteen : ~ 6.5×10−15 pcthe sun : 4.8481×10−6 pcthe nearest star (not the sun) : 1.3 pcthe center of the MW: 8 kpcAndromeda (M31): 778 kpc
Luminosity and distance
Calibrations
• Colour‐Teff (e.g. Casagade et al. 2010)
Calibrations
• Colour‐Diameter (e.g. Di Benedetto 2005)
Θ = 100.2[Sv‐V0] , SV = 2.565 + 1.483(V‐K)0 ‐ 0.044(V‐K)02
Calibrations
• Bolometric Correctionand Colour‐Teff(e.g. Casagrande & VandenBerg 2014!)
Isochrones‐ Star evolutionary track
‐> with element composition as the sun
Tid
Isochrones
Tid
‐ Star evolutionary tracks‐> Same composition but different masses
Isochrones
Tid
‐ A given point in time…
xx
xx
x
x1010År
Isochrones
Tid
1010År
Masse
Isochrones
Tid
109År
Masse
1010År
Masse
Shifted to colour‐magnitude diagram
Isochrones
older
Cassisi et al
older
Isochrones
109År
Masse
1010År
from VandenBerg et al (2013)
Colour‐magnitude diagram (CMD)
‐ Hipparcos Catalog15000 stars
Blue B‐V Red
High Temp Low Temp
Apparent Magnitude V
Low = bright!
High = faint
Colour‐magnitude diagram (CMD)
‐ Hipparcos Catalog15000 stars
Blue B‐V Red
High Temp Low Temp
Absolute Magnitude Mv
Low = bright!
High = faint
Why the differences?
Isochrones
ældre
[Fe/H]
Højere metal‐indhold
X + Y + Z = 1(H + He + resten= 1)
Cassisi et al
Detached eclipsing binaries
iM 32,1 sinR1,2/a
i =↓
M 1,2
R1,2
Pi
↑
→ [ Fe / H ]T eff
↑↓
glog
ia sin
Detached eclipsing binaries
Detached eclipsing binaries
iM 32,1 sinR1,2/a
i =↓
M 1,2
R1,2
Pi
↑
→ [ Fe / H ]T eff
↑↓
glog
ia sin
Age from a mass‐radius diagram Thompson et al. (2010) 47 Tuc
Summary
Teff : IRFM, spectroscopy, interferometry+flux[Fe/H], logg : spectroscopyR : interferometry+parallax, eclipsing binaryL : parallax+flux, eclipsing binaryM : eclipsing binaryAge: isochrones
+ as many of the others a possible!