Line Asymmetry of Cepheids
A NIR approach

Scarlet S. Elgueta
Department of Astronomy
The University of Tokyo

2017/11/16

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Background

AboutCepheids

Location in HR
diagram.
Massive stars(≥ 3.5 − 4.0M )Young ?

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Background

About

Cepheids
Discovery!: Henrietta Leavitt (P-L relation) (1912)

m - M = 5 log (d) - 5

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MethodBaade-Wesselink Method

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Background

MethodBaade-Wesselink MethodRΘΘ= tan ≈d222∆R
d[pc] =∆Θ[mas]Z t∆R[R ] = R(t) − R(t0 ) =v (t)dtt0

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Projection Factor

Phenomenology

From the latter:d∝∆R∆Θ

WithZR(t) =pVrad dt

Then, p allows us to convert radial
into pulsation velocities.

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Projection Factor

Phenomenology

p factor: δ Cep

p factor ”decision”?
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Projection Factor

Phenomenology

p factor decompositionp = p0 · fgrad · fo−g
∆Vlg
p0 =
∆RVc
Geometrical

Scarlet S. Elgueta(UTokyo)fgrad =

∆Vpg
∆Vlg

Velocity gradientLine Asymmetry of Cepheids

fo−g =∆Vpo∆Vpg

Distinction between
optical and gas
photospheric layers

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Scientific Aim

Radial Velocity DefinitionScarlet S. Elgueta(UTokyo)Line Asymmetry of Cepheids

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Scientific Aim

RV importanceScarlet S. Elgueta(UTokyo)Line Asymmetry of Cepheids

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Scientific Aim

Optical or Near Infrared?

BW Method: Where are welooking to?
Radial Velocity Amplitudes.
Advantages
Optical photospheric layer 6= Infrared
photospheric layer

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Scientific Aim

How? : WINERED
Warm INfrared Echelle spectrograph to Realize Extreme Dispersion and sensitivity

Made in Japan, now in Chile :)Warm Optics
Wide spectral coverage:
0.9 − 1.35[µm]Throughput ∼ 50 %3 Observing modes:
WIDE:0.9 − 1.35[µm] , R=30000
HIRES-Y:0.96 − 1.11[µm], R=80000
HIRES-J: 1.14 − 1.35[µm], R=80000

Scarlet S. Elgueta(UTokyo)Line Asymmetry of Cepheids

Name
Su CasDT CygSZ TauV1334 Cyg
RT AurPolarisT Vul
FF Aqlδ CepV367 Sct
η Aql
DL Cas
S Sge
ζ Gem
X Cyg

Period
1.94932
2.499223.14873
3.332823.728123.96964.43546
4.47092
5.36634
6.293077.176648.000678.3820910.15073
16.38633

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Scientific Aim

Line Asymmetry
β - Dor spectral evolution:

Sasselov & Lester in 1990:

What’s going on in here?

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Scientific Aim

Line Asymmetry
Spectral line profile → Asymmetry

How is it defined?

Involved phenomena:
Photospheric pulsation velocity
Vpuls
Limb Darkening
Velocity Gradients ?
Turbulence
All of them can be merged into one
quantity ⇒ Projection Factor!

Center determined by parabolic fit.
AL − AR× 100
ATotalAsymmetry percentage

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Ongoing

Solving the puzzle!

The corners...
Target Feasibility
Line List Creation
Telluric Analysis
Ephemeris !
RV definition & precision?
Toy modelInterferometric Counterparts

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Ongoing

ζ gem (P= 3.74 [days])Spectral evolution of Fe I (10216-18 [A])Radial Velocity curve using line minimum method.

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Conclusion

Summary
IBW Method limited by p!
Distance biased up to the 6 %(See N. Nardetto ’s Saga fron2004)
BW requirements satisfied(?)
p and its phase(in)dependence?
p and P-R and P-L relations(?)
Unpredictable p!
Challenge accepted ... (?)

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Thanks!

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