Download On the Frequency of Gas Giant Planets in the Metal

BDT Transits
Working Group Review
Alessandro Sozzetti
INAF-Osservatorio Astronomico di Torino
(On behalf of the BDT Transits WG)
Pathways to Habitable Planets
Barcelona, 14 September 2009
BDT Transits Working Group
•
Cristina Afonso ([email protected])
•
Roi Alonso ([email protected])
•
David Blank ([email protected])
•
Claude Catala' ([email protected])
•
Hans Deeg ([email protected])
•
John Lee Grenfell ([email protected])
•
Coel Hellier ([email protected])
•
David W. Latham ([email protected])
•
Dante Minniti ([email protected])
•
Frederic Pont ([email protected])
•
Heike Rauer ([email protected])
•
Alessandro Sozzetti ([email protected], Coordinator)
Pathways to Habitable Planets
Barcelona, 14 September 2009
BDT Transits WG: Goal
Gauge the potential and limitations of transit
photometry (and follow-up techniques) as a
function of depth of the science investigation,
project scale and detectable exoplanet class
Pathways to Habitable Planets
Barcelona, 14 September 2009
* Observable: decrease of stellar brightness,
when planet moves across the stellar disk
Transit Photometry
* Condition of observability: planetary orbit
must be (almost) perpendicular to the plane
of the sky
* The method allows a determination
of parameters that are not accessible to
Doppler spectroscopy, e.g. ratio of radii,
orbital inclination, limb darkening of the star
Probability of Eclipses:
It is easier to detect an eclipse
by a planet on a tight orbit
Must combine with RV in order to derive mass and radius of the planet
Pathways to Habitable Planets
Barcelona, 14 September 2009
Transit Depth and Duration
Warning!
Prone to a variety of
astrophysical false alarms
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Mimicking Planetary Transits
Eclipsing binaries:
- Grazing
- Low-mass companions
- Multiple systems and blends
Typically, 95%-99% of detections…
Pathways to Habitable Planets
Barcelona, 14 September 2009
Transiting Systems Highlights:
63 transiting planets of main-sequence stars known today (and many more to come):
Super-massive (7-13 MJ) hot Jupiters: WASP-18b, HAT-P-2b, WASP-14b, XO-3b
Very inflated (~1.8 RJ) Jupiters: WASP-12b, TrES-4, WASP-17b
The first to be tidally disrupted on a short timescale: WASP-18b
The tilted, most eccentric transiting planet: HD 80606b
The first transiting planet in a multiple system: HAT-P-13b
The first transiting brown dwarf: CoRot-3b
The first transiting Super Earth: CoRot-7b
Pathways to Habitable Planets
Barcelona, 14 September 2009
THEORETICAL INPUT
- internal properties
- structure and heat content
- atmospheric properties
OBSERVABLES
Evolutionary properties as a function
of irradiation conditions and orbital
distance:
- mass,
- radius,
- temperature,
- age,
- emergent spectrum, composition
Pathways to Habitable Planets
Strongly
Irradiated
Planets
Burrows 2005
Burrows et al. 2007
Barcelona, 14 September 2009
The Mp-Rp Relation
Coreless?
Transiting planets
come in many flavors!
What are their
actual interiors?
Very large core?
Roughly OK
How did they form?
Neptunes
Super Earth
Pathways to Habitable Planets
Barcelona, 14 September 2009
Transiting Systems Follow-up (1)
Holman et al. 2005
Winn et al. 2007
Pathways to Habitable Planets
Visible Transits:
radius, density, composition,
moons or other planets, spinorbit alignment
Barcelona, 14 September 2009
Transiting Systems Follow-up (2)
Infrared Transits:
Temperature, reflectivity and
composition, rotation, winds
Charbonneau et al. 2005
Burrows 2007
Knutson et al. 2007
Pathways to Habitable Planets
Barcelona, 14 September 2009
Ground-based Searches for Transiting Exoplanets
Credits: Heike Rauer
Pathways to Habitable Planets
Barcelona, 14 September 2009
Photometric Precision
• 0.002-0.003 mag is
achieved from the
ground (high-cadence,
meter-sized telescopes)
• For Earth-sized
companions / solar-type
stars, need better than
0.0001 mag
• The latter cannot be
achieved from the
ground
Pathways to Habitable Planets
Barcelona, 14 September 2009
Space-Based Searches for Transiting Exoplanets
instrument
in service
Telescope
diameter
Limiting Mag
Performance (σph)
Sky Coverage
N targets
CoRoT
ongoing
27cm
V~14
1,00E-04
37 deg2
50000
Kepler
2009
1m
V~14
1,00E-05
106 deg2
100000
Plato (ESA)
2017
0.75m
V~13
3,00E-05
3600 deg2
50000
> 2012
12cm
V~14
1,00E-04
40000 deg2
2500000
TESS (NASA)
Pathways to Habitable Planets
Barcelona, 14 September 2009
Space: Internal Composition of Transiting Systems
Kepler
PLATO
CoRoT
TESS-like
All-sky??
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Barcelona, 14 September 2009
Space: Atmospheric Characterization
THESIS
HST
SPICA
Spitzer
Pathways to Habitable Planets
JWST
Barcelona, 14 September 2009
Roses Have Thorns!
• Main-stream approach: main-sequence stars astrophysics
is a solved problem, for practical purposes
• Reality: for transiting systems, the star is most of the time
the limit (brightness, activity levels, age, rotation, mass,
radius, limb-darkening, composition)!
Characterization of transiting
planets requires the most accurate
knowledge of their stellar hosts
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bright/nearby stars
are privileged targets
challenge = survey
of large samples of
bright stars
Barcelona, 14 September 2009
Followup Decision Tree
Confirmation Observations
•
Very time-consuming
•
For CoRoT/Kepler (and Plato) confirmation
(via radial-velocity measurements) may not
even be feasible below a certain radius
size (depending on spectral type)
•
Could make use of some R&D
K = 9 cm/s for an Earth-like planet
Credits: TESS Team
Pathways to Habitable Planets
Barcelona, 14 September 2009
The BDT Perspective: A Grid Approach
Motivation: to understand the interplay between families of techniques,
project scale, scientific potential, and detectable exoplanet class
Project Scale:
Scientific Potential:
1: Statistical study of planetary systems
2: Identify systems suitable for follow-up
3: Full spectroscopic characterization
Green: existing
Yellow: ground, 30MEUR, 5 yr
Orange: space, 450 MEUR, 10 yr
Red: 650-1000 MEUR, 15-20 yr
Target Systems:
Hot Jupiters around F-G-K-M stars, other Jupiters around F-G-K-M
stars, hot telluric planets (Earths and Super Earths) around F-G-K-M
stars, telluric planets in the Habitable Zone of M dwarfs, telluric planets
in the Habitable Zone of F-G-K dwarfp
Pathways to Habitable Planets
Barcelona, 14 September 2009
Transits: Target Class, Science Potential, Project Scale
*
3
?
*
?
*
3
?
* See the THESIS concept too.
Pathways to Habitable Planets
Barcelona, 14 September 2009
Summary
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Transit photometry allows to characterize the bulk composition of a
planet
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It identifies systems for atmospheric characterization
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It requires large amounts of follow-up work
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The primary can often be the limiting factor
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Ongoing and future programs have the potential to nail the occurrence rate of
habitable planets around main-sequence stellar hosts, and characterize those
around stars with favorable spectral type.
•
The relevant technology for transit detection of terrestrial-type planets is
already there. Not all tools for further characterization are ready
•
Is there a need for an L/XL-class project?
Pathways to Habitable Planets
Barcelona, 14 September 2009
If You Like Transits-Related Science:
• Listen to: Tinetti, Rouan, Clampin, Nakagawa, Latham,
Swain, Català, Enya, Ricker
• Carefully read some 17 posters
• Go to the following satellite meetings:
a) PLATO (coordinators Alcalà and Pollacco),
b) panel P1 (“Can we characterize habitable planets with
transits?”, coordinator Sasselov)
Pathways to Habitable Planets
Barcelona, 14 September 2009