Directed Follow-Up of Gaia Photometry in Search of Transiting Planets

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Directed Follow-Up of Gaia Photometry in Search of Transiting Planets Shay Zucker Yifat Dzigan Tel-Aviv University Dzigan & Zucker, MNRAS, 415, 2513, 2011 Dzigan & Zucker, ApJL, 753, L1, 2012 Dzigan & Zucker,, MNRAS, accepted

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Directed Follow-Up of Gaia Photometry in Search of Transiting Planets. Shay Zucker Yifat Dzigan Tel-Aviv University. Dzigan & Zucker , MNRAS, 415, 2513, 2011 Dzigan & Zucker , ApJL , 753, L1, 2012 Dzigan & Zucker ,, MNRAS, accepted. - PowerPoint PPT Presentation

Transcript of Directed Follow-Up of Gaia Photometry in Search of Transiting Planets

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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

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Aposteriori Detection of HD209458b in Hipparcos Data

Söderhjelm 1999Robichon & Arenou 2000

Castellano et al. 2000

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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?

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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.

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Could HD209458b have been detected in 2004?

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Could HD209458b be detected in 2004?

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Could HD209458b be detected in 2004?

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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.

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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.

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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

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First Scenario – Gaia data alone

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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

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Second Scenario – one DFU observation

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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

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Third Scenario – Few DFU Observations

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Third Scenario – Few DFU Observations

Only Gaia data

Gaia data + 1 DFU observation

Gaia data + 2 DFU observations

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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

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Is it worth it?

Observational Window Function

70 Gaia Measurements 130 Gaia Measurements

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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 VHJsminimum 5 transits: ~200 minimum 3 transits: ~600

• Down to 16th G magnitude:minimum 7 transits: ~300 transiting HJs and VJHsminimum 5 transits: ~900 minimum 3 transits: ~2600

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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

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Additional slides Contingencies for potential questions

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HD189733 – Hipparcos and DFU observations

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HD189733 – Hipparcos and DFU observations

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HD189733 – Hipparcos and DFU observations

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HD189733 – Hipparcos and DFU observations

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Sanity checks

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Gaia WASP-4b – degradation of ITP over 10 years