Subaru HDS Transmission Spectroscopy of the Transiting Extrasolar Planet HD 209458b

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Subaru HDS Transmission Spectroscopy of the
Transiting Extrasolar Planet HD 209458b

• The University of Tokyo
• Norio Narita

collaborators Yasushi Suto, Josh Winn, Ed
Turner, Wako Aoki, Chris Leigh, Bunei Sato,
Motohide Tamura, Toru Yamada
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Contents

• Introduction
• Extrasolar Planets
• Transmission Spectroscopy
• Past Researches
• Subaru Observations
• Data Reduction and Results
• Correction of Instrumental Profiles
• Calculation of Difference Light Curves
• Resultant Upper limits
• Conclusions and Implications

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Extrasolar Planetary Science
Extrasolar Planets are planets orbiting around
main sequence stars other than the Sun.
The first extrasolar planet, 51 Peg. b, was
discovered by Michel Mayor et al. in 1995.
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Motivation for Researches
So far 137 exoplanetary systems have been
identified.
We already know that extrasolar planets do exist
in the universe, but we do not have enough
observational information.
What are there in extrasolar planets?
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Transmission Spectroscopy
A method to search for atmospheric components of
extrasolar planets.
At least in principle, one can detect atmospheric
components as excess absorption in the in-transit
spectra.
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Our Target
HD 209458 It is the first extrasolar planetary
system in which planetary transits by the
companion have been found.
Basic data
HD209458 G0V (Sun-like star) V
7.64 HD209458b Orbital Period 3.524738
0.000015 days inclination
86.1 0.1 deg Mass
0.69 0.05 MJ
Radius 1.43 0.04 RJ
from Extra-solar Planet Catalog by Jean
Schneider
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Past Researches
From Hubble Space Telescope
2002 An excess absorption of 0.02 in Na D lines
was reported. 2003 A strong additional Ly alpha
absorption of 15 was found. 2004 Oxygen and
Carbon were detected as well.
Charbonneau et al. 2002
Vidal-Madjar et al. 2003
Vidal-Madjar et al. 2004
From ground-based telescopes

• For the cores of atomic absorption lines (0.3Å)
• Bundy Marcy (2000) Keck I /HIRES lt 3
• Moutou et al. (2001) VLT /UVES 1

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Subaru Observations
One night observation covering an entire
planetary transit was conducted in Oct. 2002.
Orbital Period 3.5 days
We obtained total 30 spectra in 12 out 12 half
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Observing Parameters Wavelength
41006800Å Spectral Resolution 45000 SNR / pix
350 Exposure time 500
The phase of observations
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Data Reduction Scheme
Create a template spectrum from all of the raw
spectra.
Calibrate the template spectrum in total flux and
wavelength shift matched to each spectrum.
Calculate residual spectrum and integrate the
residual at specific atomic lines.
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Comparison of Two Spectra
Red and Blue two spectra taken 2.5 hours apart
Green ratio spectra (Blue / Red)
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Correction Method
In order to correct the instrumental profiles, we
have established an empirical correction method.
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Correction Result
We could limit instrumental variations almost
within the Poisson noise.
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Difference Spectra
We integrate residual over this region.
time
template
telluric
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Difference Light Curves
For example a difference light curve of Ha line.
There is no transit-related excess absorption
(blue region).
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Upper Limits
Comparison with previous results (Bundy and Marcy
2000)
Our upper limits are the most stringent so far
from ground-based optical observations.
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Conclusion and Implication

• We performed the first transmission spectroscopy
  of transiting extrasolar planet using Subaru HDS.
• However, we could not detect any transit-related
  signature.

• Our results may imply a limit of photometric
  accuracy from ground-based observations.
• Next we intend to investigate spectroscopic
  changes caused by planetary transits (i.e. the
  Rossiter effect).

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Future Work
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Implications of our Results
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The Rossiter-McLaughlin Effect
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Motivation for Researches
So far 136 exoplanetary systems have been
identified.
We already know that extrasolar planets do exist
in the universe, but we do not have enough
observational information.
What are there in extrasolar planets?
Transmission spectroscopy of transiting
extrasolar planets is one of the best clues to
study nature of extrasolar planets.