Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Microlensing search
for extra-solar planets
from Dome C
Arnaud Cassan
Astronomisches Rechen-Institut (ARI),Zentrum für Astronomie der Universität Heidelberg (ZAH)
J.-P. Beaulieu, P. Fouqué, J.-B. Marquette, C. Coutures
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Outline
1/ The microlensing method
2/ The current observing setup
3/ Results and capabilities of the method
4/ Why observing from Dome C ?
5/ Summary & conclusion
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
The Gravitational microlensing effect
► Magnification of the source star flux
• Probing the Galactic Halo (MACHO, EROS)
• Galactic structure (OGLE, MACHO, EROS)
• Search for extra-solar planets (PLANET, MOA, MicroFun)
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Observations toward the Bulge
Probability of a microlensing event : 10-6
observations toward the BulgeOGLE fields
Dome C is definitely the best site to observe the Bulge from Earth
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
• Image separation :
• Einstein radius crossing time :
• Maximum amplification :
unresolved images !
Flux magnification monitoring
mas6.0
km/s200,kpc8,kpc6 :With
*
/
solE
SLSL
M
M
vDD
daysM0.2
M 30
sol
L
/
SL
LEE v
Dt
0when 1
1002 minmin
maxmax uu
AA
3 - 4 weeks continuous observations from Dome C
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
The « standard » multi-site setup: a network of telescopes
• Ongoing microlensing events alerted by OGLE, MOA (EROS, MACHO)
Days
• Follow-up network : PLANET collaboration
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
”Homebase” :- light curves modeling- observational strategy- public alerts- anomaly predictions
Observatories Raw data
( on-line reduction )
Data reduction pipeline
Observational strategy
BUT requires many “manual” operations…
One site allow much more automated
procedures, from data reduction to data
analysis and modeling
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
MOA 2003-BLG-53Lb : a Jupiter-like planet
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
OGLE-2005-BLG-071Lb : another Jupiter-like planet
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
OGLE-2005-BLG-390Lb a 5.5 Earth-mass planet
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
OGLE-2005-BLG-169Lb : a weak Neptune plant signal
Gaps in the coverage difficulties in modeling and finding a unique model
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Detection efficiencies
Cassan et al., 2006, en préparation
[1] Modeling of individual events, e.g. :
[2] Statistical combination of the individual efficiencies
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Microlensing detection efficiencies 1995 - 2006
Cassan et al., 2006, en préparation
These planets of few Earth masses and few AU orbits may be very common
A continuous monitoring from Dome C would push the detection efficiency limits toward low-mass stars
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Limits on abundance of exoplanets
• No strong selection with star brightness (only the lens mass is involved)
• The « whole » range of star mass is probed (prop. to their abundance)
Gaudi et al. 2000
Ultimately, microlensing can provide a good estimation
of Galactic planet abundance
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Multiple planetary systems
Kubas, Cassan et al. (in preparation)
Ex. Constraints on additional Jupiter-like planets on OGLE-2005-BLG-390
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Complementary to other methods
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Main goals of microlensing
• Detection of Neptune to Earth-mass planets
• Abundance of extra-solar planets in the Galaxy
From space simulations (MPF satellite, Bennett et al. 2005) :
– 66 terrestrial planets– 100 icy giants– 3300 gas giants
Order of magnitude of what may be expected from Dome C
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Why Dome C ?With he current setup :
– Gaps in the light curve– Multi-site photometry = difficulties with combining data sets
from different telescopes (mean seeing/air mass, weather conditions, CCDs…)
– Australia do not provide stable weather conditions to operate a deep round-the-clock monitoring
Only 1 terrestrial planet so far
Given that :- the theoretical efficiency is higher than is achievable now- the main difficulties come from
- the non-continuous monitorin- The weather conditions
- the statistical point of view is the most relevant for microlensing search for exoplanets
► The ground base detection capabilities have been reached► Dome C is the most relevant site to achieve the ultimate goal of microlensing searches for exoplanets = statistical aspect
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
What would Dome C provide for microlensing towards the Bulge ?
• Continuous monitoring of the Bulge
• Stable weather condition eliminate false alerts
• Stable and good seeing, low background
• One telescope with one instrument high improvement of photometry precision + known systematic errors
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
A possible setup
• A 2m-class telescope• 28k x 28k camera
0.09”/pixel -> 0.5deg2 FOVFWHM 0.25’’
• 2 deg2 monitored in the Bulge• Time Sampling : every 20 min• During Antarctica winter season: in 2005 (sun < -18 deg) -
> 81 days• 3 – 4 weeks continuous observations (time scale < 30 d)
• A OGLE-like alert + following setup
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Summary & Conclusion
• 4 extra-solar planets discovered :– 2 Jupiter-like + 1 Neptune planets (2003-2006)– A 5.5 Earth-mass planet (2006)
• Abundance of exoplanets around M-dwarfs– will ultimately extend to “all” stars
• Sensitivity/limits on multi-planetary systems• Complementary to other techniques (ex. RV)
• Dome C is the only site on Earth that allows a continuous monitoring of the Galactic Bulge
• A realistic project :– Experience from an ongoing project (10 years with PLANET)– Expertise of data reduction/image subtraction technique– Expertise in modeling, statistical analysis
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
4
2)(
2
2
uu
uuA
Magnification:
u
Magnification curves
Einstein ring radius:
SL
LSE DD
D
c
GM2
*4
(t-t0)/tE
The single lens case
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Model predictions vs. microlensing observation
OGLE 2005-BLG-390Lb
Ida & Lin, 2005, ApJ 246, 1045
Cassan & kubas (in preparation)
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Crowded fields
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Galactic microlensing
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Beaulieu et al., 2006, Nature 439, 437
31.7.05
10.8.05
OGLE 2005-BLG-390Lb : a cool 5.5 Earth-mass planet
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
What we know from the unique modeling
• Planet/star mass ratio : q = mp / M* = (7.6 ± 0.7) x 10-5
• Instantaneous separation/Re : d = rphys / RE = 1.61 ± 0.01
• Source star distance : DS = 8.5 kpc
• Einstein ring crossing time : tE = 11.0 ± 0.1 days
RE = vt tE = 1/c [ 4GM*DL(1-DL/DS) ]1/2
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
The mass of OGLE 2005-BLG-390Lb
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Deriving physical parameters
• Planet mass & orbit : mp = 5.5 +5.5
-2.7 Earth-mass
ap = 2.6 +1.5-0.6 AU
• Host star :M* = 0.2 +0.2
-0.1 Msol
• Lens distance : DL = 6.6 ± 1 kpc
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Détection des exoplanètes
Juillet 2003
(Planète jovienne)
Mai 2005
(Planète jovienne)
Bond et al., 2004, ApJ 606 Udalski et al., 2005, ApJ 628
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
Microlentilles doubles : caustiques et courbes critiques
Caustiques (plan-source)Courbes critiques (plan-lentille)
intermédiaireSéparation : grande
faible
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
The microlensing effect
Observer
lens plane source plane
Source
< mas
Image
Arnaud Cassan Optical and Infrared Wide-Field Astronomy in AntarcticaARI / ZAH Heidelberg IAP, 14 – 16 June 2006
The PLANET collaboration(Probing Lensing Anomalies NETwork)
M. D. Albrow, J.P. Beaulieu, D. Bennett, S. Brillant, J. A. R. Caldwell, H. Calitz, A. Cassan, K. Cook, C. Coutures, M. Dominik, J.
Donatowicz, D. Dominis, P. Fouqué, J. Greenhill, K. Hill, M. Hoffman, K. Horne, U. Jorgensen, S. Kane, D. Kubas, R. Martin, J. Menzies, P.
Meintjes, K. R. Pollard, K. C. Sahu, J. Wambsganss, A. Williams
ARI Heidelberg (Germany), IAP Paris (France), Univ. of Notre Dame (USA), Univ. of Canterbury (New Zealand), SAAO (South Africa), Boyden
Observatory (South Africa), Canopus Observatory (Tasmania), Niels Bohr Institute (Denmark), Univ. of Potsdam (Germany), STSI (USA), Perth
Observatory (Australia), ESO (Chile), OMP (France)
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