A Dedicated Search for Transiting Extrasolar Planets using a Doppler Survey and Photometric Follow-up

A Proposal for NASA's Research Opportunities in Space Science

Eric Nielsen

April 28, 2004

Outline

● Extrasolar Planet Background● Importance of Transits● Program Basics● Program Methodology

Radial Velocity Planet Searches

● 111 extrasolar planets found to date by Doppler surveys

● 25 of these planets are Hot Jupiters (P < 30 days)● Requires chromospherically stable stars with

spectral type F, G, K, or M for high radial velocity precision

● Frequency of RV planets increases with parent star's metallicity

● Only one confirmed transit from radial velocity surveys: HD 209458b

Importance of Transits I● Current RV surveys only

give orbital parameters and M*sin(i) of exoplanets

● Transits give radius and more solid constraints on the mass of the planet

● Transits also give the opportunity of obtaining spectra of the planet

exoplanets.org

Importance of Transits II

● Transits are the only available method for taking spectra of exoplanets

● Determine composition of atmospheres

● Constrain models of Hot Jupiter formation and structure

Richardson et al. 2003

Going beyond current RV surveys

● No significant number of additional hot Jupiter expected to be detected by current surveys

● 3 m/s precision is overkill for such large reflex motions

exoplanets.org

Photometric Confirmation of Transits

● Detection of transits requires ~1 % photometry

● Follow up Hot Jupiter detections with: – amateur astronomy

equipment– under-subscribed

“small” telescopes

Brown et al. 2001

Seagroves et al. 2003

Program Outline I

● Observing time per year– Keck 10m 8 nights– VLT 8.4m 12 nights– AAT 3.8m 15 nights– Lick 3m 12 nights

● Survey will include 1100 stars– Spectral types F, G, and K– High metallicity sample: [Fe/H] > 0

Program Outline II

● Focus on Hot Jupiters– Drop required S/N to velocity precision of 10 m/s,

allows inclusion of currently unsampled stars– Star is dropped from the program if no RV signature

is found after 5 observations

● Expected results – 165 stars should have RV planets– 41 Hot Jupiters to be detected over 3 years– 2 Transits – Triples the number of known transits

from RV targets.

Planets Correlate with Metallicity

Fischer et al. 2004

OGLE Detections● OGLE's detection of transits is sensitive mainly

to periods P < 10 days, while our program will seek planets out to P < 30 days

● The stars surveyed by OGLE are ~5 magnitudes fainter than those in our survey, leading to radial velocity errors of 100 m/s – only the closest-in planets are confirmable with RV follow-up

● The 100x factor in flux severely limits the quality of the spectra that can be extracted during transits

Gratuitous 55 Cancri reference

exoplanets.org