Subaru HDS Transmission Spectroscopy of the Transiting Extrasolar Planet HD 209458bThe University of TokyoNorio NaritacollaboratorsYasushi Suto, Josh Winn, Ed Turner,Wako Aoki, Chris Leigh, Bunei Sato, Motohide Tamura, Toru Yamada

ContentsIntroductionExtrasolar PlanetsTransmission SpectroscopyPast ResearchesSubaru ObservationsData Reduction and ResultsCorrection of Instrumental ProfilesCalculation of Difference Light CurvesResultant Upper limitsConclusions and Implications

Extrasolar Planetary ScienceExtrasolar 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.

Motivation for ResearchesSo 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?

Transmission SpectroscopyA 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.

Our TargetHD 209458It is the first extrasolar planetary system in which planetary transits by the companion have been found.HD209458 G0V (Sun-like star) V = 7.64HD209458b 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 Jean SchneiderBasic data

Past Researches2002 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. 2002Vidal-Madjar et al. 2003Vidal-Madjar et al. 2004From Hubble Space TelescopeFrom ground-based telescopesFor the cores of atomic absorption lines (0.3)Bundy & Marcy (2000) Keck I /HIRES < 3 % Moutou et al. (2001) VLT /UVES ~ 1 %

Subaru ObservationsThe phase of observationsOrbital Period3.5 daysOne night observation covering an entire planetary transit was conducted in Oct. 2002.Observing ParametersWavelength 4100~6800Spectral Resolution 45000SNR / pix 350Exposure time 500We obtained total 30 spectra:in 12 out 12 half 6

Data Reduction SchemeCreate a template spectrum from all of the raw spectra.Calculate residual spectrum and integrate the residual at specific atomic lines.Calibrate the template spectrum in total flux and wavelength shift matched to each spectrum.

Comparison of Two SpectraRed and Blue two spectra taken 2.5 hours apartGreen ratio spectra (Blue / Red)

Correction MethodIn order to correct the instrumental profiles,we have established an empirical correction method.

Correction ResultWe could limit instrumental variations almost within the Poisson noise.

Difference SpectraWe integrate residual over this region.timetemplatetelluric

Difference Light CurvesThere is no transit-related excess absorption (blue region).For example: a difference light curve of H line.

Upper LimitsOur upper limits are the most stringent so far from ground-based optical observations.Comparison with previous results (Bundy and Marcy 2000)

Conclusion and ImplicationWe 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).

Future Work

Implications of our Results

The Rossiter-McLaughlin Effect

Motivation for ResearchesSo 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.