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Searching for Frozen super Earth mass
planet via microlensing.
Jean-Philippe Beaulieu,
Institut d’Astrophysique de Paris
PLANET/ROBONET collaboration
HOLMES : Hunting fOr Low Mass Extrasolar Planets
Funded by Agence Nationale de la Recherche, France (2007-2011)
See also contributions by J. Donatowicz (TU Wien), S. Gaudi (Ohio)
Target Field in the Central Galactic Bulge
Galactic center
8 kpc
Sun
1-7 kpc from Sun
Light curve
Source star
and images
Currently, OGLE-III and MOA-II
Lens star
and planet
Observer
Unveiling a planetary companion
tE  20 j, M  0.3 Msun :
tp  q t E
Jupiter : q  3 10 -3  t p  1 j

Terre : q  105  t p  1.5 h
1995 : No planet detected so far.
Microlensing seemed to be a
cool and easy Jupiter hunting method…
Gould et Loeb 1992 : « Planets in a solar-like system positioned half-way to the
Galactic center should leave a noticeable signature (magnification larger than 5
percent) on the light curve of a gravitationally lensed bulge star in about 20 percent
of the microlensing events. »
1996, sensitivity to Earths depends on source size
Earth mass planet
signal is washed
out for giant
source stars
If planetary Einstein Ring < source star disk: planetary microlensing effect
is washed out (Bennett & Rhie 1996)
For a typical bulge giant source star, the limiting mass is ~10 M
For a bulge, solar type main sequence star, the limiting mass is ~ 0.1 M
Need to monitor small stars to get low mass planets.
Using high magnification events,
Griest & Safizadeh 1998
« We show that by focusing on high-magnification events,
the probability of detecting planets of Jupiter mass or greater
in the lensing zone [(0.6
1.6)RE] is nearly 100%,
with the probability remaining high down to Saturn masses
and substantial even at 10 Earth masses. »
Planetary caustic
Central caustic
Detection ≠ characterization
Hunting for planets via microlensing
Detecting real time microlensing event : OGLE-III and MOA 2
Detecting anomalies real time :
Networks of telescopes to do 24 hours monitoring : PLANET/RoboNET, microFUN
Accurate photometry (Image subtraction since 2006)
Real time analysis and modeling
OGLE-III has an online anomaly detector (EWS)
MOA-II
Selecting microlensing event with good planet detection efficiency
Two schools :
- Mainly high magnification events and alerted anomalies (microFUN)
- Monitoring a larger number of events (PLANET/ROBONET)
All. data, models, are shared immediately among the microlensing community.
Cooperation is the way to go !
PLANET/ROBONET collaboration :
Probing Lensing Anomaly NETwork
(current members)
http://planet.iap.fr
Boyden 1.5m
M. D. Albrow, J.P. Beaulieu, V. Batista, D. Bennett, D. Bramich, 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, N. Kaens, K. Horne, F.
Jablonski, U. Jorgensen, S. Kane, D. Kubas, R. Martin, E. Martioli, J. Menzies, P.
Meintjes, K. R. Pollard, K. C. Sahu, Y. Tsapras,J. Wambsganss, A. Williams, M.
Zub
Institut d'Astrophysique de Paris, INSU CNRS, Paris, France
Univ. of Canterbury, Dept. of Physics & Astronomy, Christchurch, New Zealand
South African Astronomical Observatory, South Africa
Boyden Observatory, Bloemfountein, South Africa
Canopus observatory, Univ. of Tasmania, Hobart, Australia
Niels Bohr Institute, Copenhagen, Denmark
Univ. of Potsdam, Potsdam, Germany
Space Telescope Science Institute, Baltimore, U.S.A.
PLANET/RoboNet
SITES
Boyden 1.5m
ESO Danish 1.54m 2003-2008
Brazil 0.6m, 2007+
Sutherland, SAAO 1m 2002-2007+
Boyden, 1.5m, CCD 2006, 2007
Perth 0.6m 2002-2007+
Hobart 1m, 2002-2007+
Robonet :
Liverpool 2m, Canary 2005+
Faulkes North 2m, Hawaii 2006+
Faulkes South 2m, Australia 2007+
Goals at each site :
- ~1 % photometry,
- Adapted Sampling rate
- Online analysis.
PLANET DATA PROCESSING
At each site :
-relative photometry for all stars real time
- keep an eye on light curve of prime target
Data from all sites are uploaded to Paris (every ~10 min) :
RoboNet
SAAO
Boyden
Chile
Every day, homebase checks :
data, light curve fits, BAP,
StAndrews priorities algo,
Choose strategy, sampling, …
Alert the community if anomalies
Hobart
Perth
2006 season :
71 events observed by PLANET, 26 by RoboNet
12 events with Amplification > 40 :
MOA 99, 137
OGLE 195, 221, 229, 245, 265, 416, 437, 440, 451
17 events with 40 > Amplification > 10
5 stellar binaries : MOA 3, OGLE 277, 284, 304, 335
9 Anomalous events : OGLE 38, 109, 207, 215, 238, 375, 398, 435, 450
2 variable sources : OGLE 357, 474
52 normal events
CONTRAINTS ON EXTRA SOLAR
PLANETS FROM SINGLE LENS
Albrow et al., 1998
Detection efficiencies
Plan (d,q)
Plan
physique
► Diagrams computed for 1995-2005 events
Methods and Models
• single lens/double lens
• blending
• finite source effects
• ≈ 70+ diagrams computed so far
• Combining them in a rigorous way to derive
planet abundances.
Cassan et al. In prep, coming soon…
OGLE-2005-BLG-390
Coopération : PLANET/RoboNET, OGLE-III, MOA-II
AT LAST, A TEXT BOOK MICROLENSING EVENT
Gould Loeb 1992, Bennett & Rhie 1996, …
Data in the anomaly from : PLANET-Danish, OGLE-III, MOA-II, PLANET-Perth
Data outside the anomaly from : PLANET/Robonet, PLANET-Hobart
PROBABILITY DENSITIES OF THE
STAR AND ITS PLANET
Detection probabities of a Jupiter or a 5.5 Earth mass
In a OGLE-2005-BLG-390 like event
A companion to this frozen super Earth ?
Kubas et al., 2007 submitted
Excluding at :
50 % Jupiter over 1.1-2.3 AU
70 % 3 Jupiter over 1.5-2.2 AU
Core accretion models by Idal & Lin
PLANET detection efficiencies
Neptunes and super-Earth are much more common than Jupiters
Same direction as the core accretion model predictions.
Udalski et al., 2005
Bond et al., 2004
Gould et al., 2006
Beaulieu et al., 2006
Cassan, Kubas, Beaulieu et al., 2007 in prep
DUNE-ML
(Courtesy K. Horne)
Current status of microlensing planet hunting
OGLE-III, MOA-II and PLANET/ROBONET, MicroFUN
-
Network of telescopes, round the clock monitoring.
Frozen Super Earth are detectable from the ground by microlensing.
Much more common than gazeous giants.
Total cooperation between all teams.
Coming out soon :
Fractions from Jupiter to super Earth (combining 1995-2005 data)
Microlensing 2007-2010 : Constraints on frozen super Earth.
Microlensing 2011+ : EARTH HUNTER, DUNE-ML, MPF, …
Talk by Scott Gaudi (Future microlensing projects)
OGLE-2005-BLG-071
Led by OGLE & microFUN
Close binary :
d=0.758
q=6.7 10-3
Wide binary :
d=1.294
q=7.1 10-3
M* ~ 0.45 Mo
5.2 ± 1.8 kpc
2.7 MJupiter
a ~ 2.2 AU or3.7 AU
Central caustic,
Degeneracy d 1/d
Sensitivity to Earths Depends on Source Size
Earth mass
planet signal is
washed out for
giant source stars
Need to monitor small stars to get low mass planets !
Ground-based confusion, space-based resolution
• Main Sequence stars are not resolved from the ground
• Systematic photometry errors for unresolved main sequence stars
cannot be overcome with deeper exposures (i.e. a large groundbased telescope).
• High Resolution + large field + 24hr duty cycle
2007 should be fun !
HOLMES Hunting fOr Low Mass Extrasolar Planets
Funded by Agence Nationale de la Recherche, France (2007-2011)