Exoplanetary Science in Australia: Detection, Characterisation, and Destruction Rob Wittenmyer National Astronomical Observatories of China 2013 June 21
Unseen planets pull on the star as they orbit. That motion is measured as a shift in the star s spectral lines. This shift is typically less than 50 meters/sec.
Anglo-Australian Planet Search Established in 1998 First planet in 2001 Iodine cell radial velocity ~50 nights/year since 2009B Rocky Planet campaigns in 2007, 2009 Team members Chris Tinney, Paul Butler, Hugh Jones, Simon O Toole, Brad Carter, Jeremy Bailey, Rob Wittenmyer, Jonti Horner, Duncan Wright, Graeme Salter
Anglo-Australian Planet Search Storytime: HD 159868 First announced as a single, eccentric planet in 2007 P = 2.7 years, e = 0.69
Anglo-Australian Planet Search Storytime: HD 159868 5 more years of data reveal a second planet P2 = 352 days, e2 = 0.15 Now outer planet has a much lower eccentricity! P1 = 3.2 years, e1 = 0.01
Anglo-Australian Planet Search Storytime: HD 159868 How many more single eccentric planets are really two near-circular planets? Try it! We fit 82 1-planet systems (e>0.3) with two planets restricted to e<0.2. Most of the time, this resulted in likely unstable 1:1 configurations but some gave promising results.
Anglo-Australian Planet Search Storytime: HD 159868 Dynamical tests of the 2-planet scenarios: All systems stable for 100 million years! Wittenmyer, Wang, Horner et al. 2013, ApJ
Johnson (2007)
For high-mass stars on the main sequence, we cannot get precision velocities because: 1) High temperatures = fewer spectral lines. 2) Rapid rotation = lines are broadened. When the star evolves into a subgiant, its photosphere expands and cools, solving both of these problems!
High-mass stars seem to be more likely to have planets. But the sample size is small. Johnson (2007) We need to target more of these massive stars to confirm this trend. Recent results show that ~20% of stars M>1.5 M sun have a planet. Johnson et al. (2010)
AAT observations and funding proposals Rob Wittenmyer, Chris Tinney Additional observations from other sites John Johnson Hu Shao Ming Stellar abundance analysis Wang Liang, Zhao Gang Doppler code and McDonald observations Michael Endl
Single-epoch RV precision 4-6 m/s Tau Ceti, the gold standard for velocity stability
7 CMa b: First planet discovery! P = 763 days, 2.6 Jupiter masses. Wittenmyer et al. 2011, ApJ 743: 184.
Some long-period candidates needing more data to complete orbits
Candidate 2-planet system P1 = 1091 days, P2 = 52 days
Short-period candidate: P = 105 days, 1.6 Jupiter masses Phase plot
Where are the shortperiod planets? Only 6 with P<100 days Is this a real deficit, or due to observational selection effects? e.g. O Toole et al. 2009, Wittenmyer et al. 2010, 2011a, 2011b
A Monster Run approach: Choose a small number of stars, observe every one on every night, for 40+ consecutive nights! This has resulted in AAPS discovery of 5 low-mass planets. No one has tried this for massive stars! We will be the first: Shandong University 1-metre telescope with new high-resolution spectrograph. Plan: Choose ~30 bright giant stars, Observe for 40-50 consecutive nights. Aim: Detect or exclude all planets with a<0.3 AU, M>0.5 Jupiter mass. 61 Vir planets: Vogt et al. (2010)
Kepler results show that small planets are MUCH more common than large ones. This is consistent with radial-velocity results: Even stable stars show evidence for planets, given enough high-precision observations. Howard et al. (2012) So we should intensely observe as many stars as possible! Pepe et al. (2011)
xkcd.com/975 We would like to observe every star, every night the ultimate Monster Run But telescope time is very hard to get, and this strategy will not work with a standard shared-use facility. There are too many stars! We need a new facility optimised for this strategy.
It pays to own the telescope! Initiated by Caltech collaborator John Johnson 4 x 0.7m telescopes located on Mt Palomar Each telescope can operate independently for photometric observations, or all 4 can simultaneously fibre-feed a high-resolution spectrograph. Kiwispec compact, vacuum-enclosed spectrograph, R=75000, iodine cell calibration target 1 m/s velocity precision. All parts are off-the-shelf Inexpensive and easy to get.
Science goals 1. Nightly radial-velocity observations of bright stars. -- Target precision of 1 m/s 3-15 earth-mass planets detectable -- High cadence and precision makes every target new again HD 20794: a stable star from the Anglo-Australian Planet Search. For P<100 days, we ruled out planets more than 50 Earth masses. Detectability: 10% for M>8 Earth mass Data rms = 3.43 m/s, N=78 Wittenmyer et al. (2010)
Science goals HARPS results for HD 20794: P = 18 days 2.7 Earth masses P = 40 days 2.4 Earth masses Better precision (rms = 1.2 m/s) More data (N=173) P = 90 days 4.8 Earth masses Pepe et al. (2011)
Science goals 2. Search for transits of known radial-velocity planets. -- Successful approach: e.g. HD 209458b, HD 80606b, 55 Cancri e -- Transit allows for most comprehensive knowledge of the planet HD 80606b Highly eccentric (e=0.93) 111-day period 3.9 Jupiter masses Naef et al. (2001)
Rapid atmospheric heating observed by Spitzer in secondary eclipse Science goals Primary transit observed from the ground! G. Laughlin, oklo.org Laughlin et al. (2009) Shporer et al. (2010)
Science goals 3. Follow-up photometry for confirmed and candidate transiting planets. -- Improve transiting system parameters, look for timing variations -- Higher-resolution follow up for candidates from wide-field transit surveys 1' 1' Image credit: M. Hidas Wide-field transit surveys all have the same problem: Large (10 arcsec) pixels can cause confusion!
Science goals High-resolution photometry from Minerva can resolve the various blend scenarios. Critically needed for all transit surveys! F. Bouchy, presentation at ESO at 50 conference, 2012
Project status 2013 April -Telescope 1 delivered to Caltech for testing. -First-light operations with Apogee 2Kx2K imager Transit science and public outreach -Telescopes 2 and 3 paid for by partners Penn State and U. Montana. -KiwiSpec spectrograph paid for by Harvard-Smithsonian Center for Astrophysics. -UNSW-led grant proposal for Australia to purchase Telescope 4. -Site: Mt Hopkins, Arizona Test platform at Caltech, 2012 July
THINK BIG Once the Minerva concept is proven at Mt Hopkins, why not do it in the southern hemisphere? Minerva-South: Coming to Siding Spring Observatory China AST-3/CSTAR follow-up Pan-Pacific Planet Search monster runs And more partners wanted!
Constraining Multiple Exoplanetary Systems with Dynamical Simulations In collaboration with: Jonti Horner Jonathan Marshall Tobias Hinse Using high-performance computing facilities at UNSW (Katana) and Murdoch University (Epic)
Why do dynamics? Sometimes, observations of a star are used to detect planets on orbits that might not be stable So, are these really planets? - Qian et al., 2011, MNRAS, 414, L16-L20 Best Min. Max. fit a,e orbits, for planet 20 year c, integration 7.5 30 years
The dynamics of HU Aquarii Horner et al., 2011, MNRAS, 416, L11-L15
The dynamics can also work to support an exoplanet discovery The two Jupiter-mass planets in the HD155358 system move on stable orbits close to mutual 2:1 mean-motion resonance. Planet b at a = 0.64, e = 0.17 Robertson et al. 2012, ApJ 749: 39
The dynamics can even put quite tight constraints on the system in question This new system is only stable if the two planets are trapped in 3:2 MMR (HD 204313b at a = 3.04 AU, e = 0.23) Robertson, Horner, Wittenmyer et al. 2012, ApJ 754: 50
While some systems are dynamically quite boring HD 159868b at a = 2.25 AU, e = 0.05 Wittenmyer et al. 2012, ApJ 753: 169
A summary of our dynamical mapping results Circumbinary planets detected by eclipse timing HW Vir Horner et al. 2012b, MNRAS 427, 2812 NN Ser Horner et al. 2012a, MNRAS 425: 749 HU Aqr Horner et al. 2011, MNRAS 416: L11 Wittenmyer et al. 2012a, MNRAS 419: 3258 Radial-velocity planets HD 155358 Robertson et al. 2012a, ApJ 749: 39 HD 204313 Robertson et al. 2012b, ApJ 754: 50 HD 159868 Wittenmyer et al. 2012b, ApJ 753: 169 HD 200964 & 24 Sex Wittenmyer et al. 2012c, ApJ 761: 165
A summary of our dynamical mapping results Circumbinary planets detected by eclipse timing HW Vir Horner et al. 2012b, MNRAS 427, 2812 NN Ser Horner et al. 2012a, MNRAS 425: 749 HU Aqr Horner et al. 2011, MNRAS 416: L11 Wittenmyer et al. 2012a, MNRAS 419: 3258 Radial-velocity planets HD 155358 Robertson et al. 2012a, ApJ 749: 39 HD 204313 Robertson et al. 2012b, ApJ 754: 50 HD 159868 Wittenmyer et al. 2012b, ApJ 753: 169 HD 200964 & 24 Sex Wittenmyer et al. 2012c, ApJ 761: 165
rob@phys.unsw.edu.au