The HARPS-Spitzer Transit Search: First Results Michaël Gillon B.-O. Demory, D. Deming, S. Seager, C. Lovis & the HARPS team IAU Symposium 276 – Torino, Italy – 12 Oct 2010

Context: from transiting planet characterization to exoplanetology Hellier et al. (2010)Clampin et al. (2010)

What is the best target among transiting planets for atmospheric studies? Swain et al. 2008Grillmair et al Detected by RV (Bouchy et al. 2005) Answer: HD189733b! Bloated hot Jupiter + late-type star dF = 2.5 % K = 5.5 “Rosetta Stone” for exoplanetology

Characterizing low-mass planets: “super-Earths” and “Neptunes” RV + microlensing: their population is big Transits: their diversity is large Goal: detecting a few that transit and that can be studied thoroughly  transit search for RV low-mass planets Hartmann et al. (2010) Super Earths Neptunes

The HARPS-Spitzer transit search HARPS: ~30 short-period low-mass planets orbiting bright nearby stars, a few of them should transit. Detecting them: - very precise photometry (transit depth from 100 to 1000 ppm) - continuous observation of 5 – 25 hours Spitzer has demonstrated exquisite photometry and can monitor the same star during days to weeks Cryogenic Spitzer DDT program targeting HD40307b (Mayor et al. 2008) + Warm Spitzer DDT program (100 hours): 9 most promising candidates

Search for the transit of the “hot super-Earth” HD 40307b Mayor et al Host star: K2V, V=7.2, K=4.8, d=13pc Planets: 3 “super-Earths”, including one at AU (3.93d) Msini = 4.2 M Earth Prior P transit ~ 7%

Search for the transit of the “hot super-Earth” HD 40307b Gillon et al Data: 3 runs Spitzer/IRAC 8μm (25h) Msini ~ 4.2 M Earth, P transit ~ 7% Star: K2V, K=4.8 Baseline model:

Search for the transit of the “hot super-Earth” HD b Gillon et al Global Bayesian analysis HARPS RVs + Spitzer photometry. Prior: R p > 1.0 R Earth (pure iron) Posterior P transit : 0.19%

Search for the transit of the “hot Neptune” HD 47186b Msini~22.9 M Earth, P transit ~10% Star: G5V, K=6 Data: Spitzer/IRAC 3.6μm (5h) Rms=130ppm/5min Posterior P transit < 0.5% Baseline model:

Search for the transit of the “hot Neptune” HD 10180c Msini~13.1 M Earth, P transit ~9% Star: G1V, K=5.9 Data: Spitzer/IRAC 3.6μm (10.2h) rms=97ppm/20min Posterior P transit : not high… Baseline model:

Search for the transit of the “hot super-Earth” GJ 3634b Bonfils et al Host star: M2.5V, V=11.95, K=7.5, d=18pc Planet: “Super-Earth” at AU (2.645d) Msini = M Earth, e~0 Prior P transit ~ 6.5% HARPS M-stars program (Grenoble/Liège/Genève, PI X. Bonfils) 400 M-stars, 10 consecutive nights to select quickly short-period candidates Goal: statistics + transit

Search for the transit of the “hot super-Earth” GJ 3634b Data: Spitzer/IRAC 4.5μm (6h30) Baseline model: rms = 100ppm/20min

Search for the transit of: the “hot super-Earth” GJ 3634b Global Bayesian analysis HARPS RVs + Warm Spitzer photometry. Prior: R p > 1.2 R earth (pure iron) Bonfils et al Posterior P transit : 0.5%

Preliminary conclusions - No transit for HD 40307b, HD 10180c, HD 47186b - New super-Earth orbiting around a M-dwarf: GJ 3634b. It does not transit - Data for 4 other candidates are still under analysis - Still 2 planets to be observed - Enough low-mass HARPS planets to justify a new program - Warm Spitzer: more systematic effects at 3.6μm, while 4.5μm channel photometry remains very good - We also collaborate with MOST (D. Dragonir), no transit detected yet