twenty years of microlensing observations from the andrzej udalski warsaw university observatory...
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Twenty Years of Microlensing Observations
From the
Andrzej Udalski
Warsaw University Observatory
Perspective
Bohdan Paczyński (1940—2007)
Gravitational Microlensing toward the Galactic Bulge
Planetary Microlensing
Search for Gravitational Microlenses
• MACHO Project – Mt. Stromlo, Australia (1992 – 1999)
• EROS Project – ESO, Chile (1992 – 2002)
• MOA Project – Mt. Johns, New Zealand (1997– …)
• OGLE Project – Las Campanas, Chile (1992 – …)
Twenty One Years of the OGLE Survey
OGLE: The Optical Gravitational Lensing Experiment (1992 - ….)
Four Phases of the OGLE Project
• OGLE-I (1992-1995). 1 m Swope telescope at LCO. ~2 million stars observed. Microlensing
• OGLE-II (1997-2000). 1.3 m Warsaw telescope. ~40 million stars observed. Variable and non-Variable Stars in GB, MC
• OGLE-III (2001– 2009). 8k x 8k mosaic CCD. ~200 million stars observed (GB, GD, MC). Extrasolar Planets, Microlensing
• OGLE-IV (2010– ….). 32-chip 256 Mpixel mosaic CCD
http://ogle.astrouw.edu.pl
Las Campanas Observatory, Chile
Discovery of the First Microlensing Events – September 1993
OGLE-I #1
Microlenses: Discovery of the first events toward the GB (1993).
First Binary Microlensing (1994)
Fine Microlensing Effects
Early Warning System (EWS – 1994)
Follow-Up Microlensing Projects
< 2001• PLANET
• GMAN
• MOA
>= 2001• microFuN
• PLANET
• Robonet
• MindSTEP
Three Main Channels
• Search for Dark Matter• Galactic Structure• Extrasolar Planets – Planetary Microlensing
Dark Matter – MACHO in the Galactic Halo
OGLE-2005-SMC-001
OGLE MC Microlensing
Current O-IV MC Survey – 600 square degrees
LMC
SMC
Magellanic Bridge
Classical Cepheids in the Magellanic Clouds
LMC
SMC
Magellanic Bridge
RR Lyrae Stars in the Magellanic Clouds
Stellar Populations in the Magellanic Bridge
OGLE-IV Transient Detection System
Galactic Structure
• Optical depth for microlensing toward CG• High resolution spectroscopy of highly
microlensed bulge dwarfs• Microlensing in the Galactic disk
Gravitational Microlensing Optical Depth
• probably the best way to constrain the internal structure of the Milky Way
• The recent models of the Galactic Bulge: Kerins,Robin,Marshall (2010)
• OGLE >~10000 microlenses
3.2±0.8 (OGLE3 2007)
2.4±0.4 (MACHO 2000)
2.6±0.8 (MOA 2003)
Optical Depth
Microlensing in the Galactic Disk
OGLE-IV Galactic Disk (l<0)
Planetary Microlensing
OGLE-III Hardware and Software (2001)
• 1.3 m OGLE telescope at Las Campanas Observatory, Chile
• 8192 x 8192 pixel mosaic CCD camera (0.26 arcsec/pixel scale): 0.5 x 0.5 sq. degree
• Data Pipeline: photometry derived with image subtraction method (accuracy up to 3 mmag for the brightest stars over a few months long observing run)
Transiting OGLE Exoplanets
Planetary Microlensing
O-III ~600 microlensing events per year in real time since 2002.
Short-lived anomaly in the light curve of a typical single mass microlensing event.
OGLE-2003-BLG-235/MOA-2003-BLG-53First Planetary Microlensing
Planet/star mass ratio: q~0.004
OGLE-2005-BLG-71
Planet/star mass ratio: q~0.007
OGLE-2005-BLG-390
Planet/star mass ratio: q~0.00008. Mass of the planet: ~6 Earth masses. The least massive planet at the discovery
MOA-II Survey (2006– …)
Microlensing Planets – results
• ~30 microlensing planets found since the first announcement in 2004 (~20 published so far)
• First cool super-Earths of 3-10 Earth masses: low mass planets are common
• OGLE-2006-BLG-109: analog of the solar system (multiplanetary system: Jupiter+Saturn like)
• First estimations of the frequency of planets at and behind the „snow line”
• 2003– 2007: the discovery rate 0-1 exoplanets per season
• 2007–2010: the discovery rate of 2-4 exoplanets per season
Main Potential of Microlensing
• Full status and characterization of exoplanets in regions located 0.5—10 AU from Host Stars (the regions at and behind the Snow Line)
• Status of exoplanets around wide range of types of Host Stars
• Discovery of low mass planets from the ground
Second Generation Planetary Microlensing Survey
• Survey and Follow-up in one• Network of 1—2-m class telescopes over the globe with
large field (>1 square degs) cameras• Monitoring of the most microlensing efficient parts of the
Galactic bulge with the cadence of ~15 minutes• No missing planets, easier estimation of survey statistics• Estimations: A network of three 1.3—2 m telescopes: the
detection of 1—4 Earth mass planets, 10—15 super-Earths, 100 Jupiter mass planets per year
• Five year long survey should provide resonable large sample of planets for estimation of the census of exoplanets down to Earth mass at orbits of 0.5—10 AU
OGLE-IV: 2010 – ….
• 32 chip 256 Mpixel mosaic CCD camera (+ 2 chips for guiding)
• 2048 x 4102 pixel E2V 44-82 DD CCD detectors (15 m).
• 1.4 square degrees field, 0.26”/pixel
• 20 sec. reading time
• First light September 7, 2009
• Regular observations since March 4/5, 2010
OGLE-IV Nowa Kamera Mozaikowa
OGLE-IV 2012 BLG SKY
Cadence: red – up to 30 epochs/night
yellow – up to 10 epochs/night
green – up to 3 epochs/night
blue – ~1 epoch/night
cyan – ~1 epoch /2 nights
Real Time Microlensing: OGLE-IV
• 58 O-IV fields analyzed in real time including all very high and high cadence
• Statistics for 2012 BLG season: ~1700 on-line detections (~20 in O-I, ~60/season in O-II, ~600/season in O-III)
• Total number of OGLE-IV microlensing fields: 107 – they will be gradually included to EWS
OGLE-IV planetary microlenses 2010Commissioning Mode
MOA-2010-BLG-117 MOA-2010-BLG-328
MOA-2010-BLG-477 MOA-2010-BLG-523
2012 Planetary Microlensing
Free-Floating Planets
• Microlensing event characteristic time: tE=RE/vtr
• RE~sqrt(Mlens) → tE~sqrt(Mlens)• tE< 2 days – lensing object has planetary mass• High cadence observations needed for detection : (OGLE-IV:
18-60 min.)• MOA and OGLE data from 2006-2007: 10 short-lived
microlensing events of likely planetary mass. No trace of host stars: population of unbound (FFP) or very distant exoplanets.
• OGLE-IV data much better suited : preliminary estimation – 2011 season: ~40 events with tE< 2 days (shortest corespond statistically to a few Earth mass objects)
• Origin: gravitational interactions – stellar encounters, ejection of planets during planetary system formation
OGLE-IV 2013 BLG SKY
Cadence: red – up to 30 epochs/night
yellow – up to 10 epochs/night
green – up to 3 epochs/night
blue – ~1 epoch/night
cyan – ~1 epoch /2 nights
Prospects for Planetary Microlensing Field: Bright
• New facilities: Bisdee Tier Tasmania, LCOGT Network, KMNet
• Space Missions: WFIRST, EUCLID
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