Search for Transiting Planets around Nearby M Dwarfs Norio Narita (NAOJ)
Directed Follow-Up of Gaia Photometry in Search of Transiting Planets Shay Zucker Yifat Dzigan...
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Transcript of Directed Follow-Up of Gaia Photometry in Search of Transiting Planets Shay Zucker Yifat Dzigan...
Directed Follow-Up of Gaia Photometry in Search of Transiting Planets
Shay ZuckerYifat Dzigan
Tel-Aviv University
• Dzigan & Zucker, MNRAS, 415, 2513, 2011• Dzigan & Zucker, ApJL, 753, L1, 2012• Dzigan & Zucker,, MNRAS, accepted
Aposteriori Detection of HD209458b in Hipparcos Data
Söderhjelm 1999Robichon & Arenou 2000
Castellano et al. 2000
Why not a real detection?
• No one believed it was possible• Photometry not precise enough• Low cadence
Can we use the data for detection somehow?
Directed Follow-Up – General Idea
• Actually sampled transits provide some knowledge about the period, phase, duration and depth of a hypothetical transit, if it exists.
• Using MCMC we can present this scarce information as a Probability Distribution Function over (P,Tc,w,d) (assuming a BLS-like model).
• For each future time – t, we can use this PDF to calculate an instantaneous transit probability – ITP(t)
• Each new follow-up observataion is added and the process is repeated.
Could HD209458b have been detected in 2004?
Could HD209458b be detected in 2004?
Could HD209458b be detected in 2004?
Lessons from Hipparcos HD209458 Exercise
• With five sampled transits, low cadence data, augmented by DFU, allow detection.
• Data become useless after a few years.• For completeness – we should mention HD189733b.
Testing DFU on Gaia
• Simulated Gaia light curves inspired by known transiting planets (period and duration, coordinates)
• Gaia scanning law• Phase chosen to produce required number of
sampling transits• Photon noise level – 1 mmag.• We defined three scenarios of detection.
First Scenario – Gaia data alone
• Gaia samples enough transits to allow detection of the transit using only Gaia data.
• 1-mmag precision makes this scenario possible.• Simulation inspired by CoRoT-1b (P=1.51 d, w=0.1 d)
• Assuming five sampled transits (Ntot=64)• d > 0.005 mag
First Scenario – Gaia data alone
Second Scenario – one DFU observation
• Gaia samples enough transits to allow several possible solutions. One DFU observation is enough to constrain the period.
• Simulation inspired by CoRoT-4b (P=9.20 d, w=0.16 d)
• Assuming three sampled transits (Ntot=63)• d > 0.001 mag
Second Scenario – one DFU observation
Third Scenario – Few DFU Observations
• Gaia samples enough transits to allow several possible solutions. A few DFU observations are needed to constrain the period.
• Simulation inspired by WASP-4b (P=1.338 d, w=0.104 d)
• Assuming four sampled transits (Ntot=83)• d = 0.005 mag
Third Scenario – Few DFU Observations
Third Scenario – Few DFU Observations
Only Gaia data
Gaia data + 1 DFU observation
Gaia data + 2 DFU observations
We shouldn’t wait till the last minute
• ITP deteriorates over time• Therefore – we should start observing even before the
end of the mission• Tres-1b, (P=3.03 d, w=0.104 d)
• Three sampled tranists (Ntot=48) (mid-life of mission)
• Assume d=0.008 mag
Is it worth it?
Observational Window Function
70 Gaia Measurements 130 Gaia Measurements
Is it worth it?
• Assuming 2 hr transit, Galactic model,
transiting planet statistics from complete surveys (OGLE)
• Down to 14th G magnitude:
minimum 7 transits: ~70 transiting HJs and VHJs
minimum 5 transits: ~200
minimum 3 transits: ~600
• Down to 16th G magnitude:
minimum 7 transits: ~300 transiting HJs and VJHs
minimum 5 transits: ~900
minimum 3 transits: ~2600
To do list:• Get organized
– Dedicated observatory network?– CU7 follow-up network?– Science Alert team?
• Prescreening scheme (metallicity, brightness, activity etc.)• Develop a more efficient computational scheme than MCMC.• Objective criteria for applying DFU
– Wald statistics– ITP values– ITP skewness
• Smaller planets (Neptunian and below?)• Other low-cadence surveys
Additional slides Contingencies for potential questions
HD189733 – Hipparcos and DFU observations
HD189733 – Hipparcos and DFU observations
HD189733 – Hipparcos and DFU observations
HD189733 – Hipparcos and DFU observations
Sanity checks
Gaia WASP-4b – degradation of ITP over 10 years