variable stars
DESCRIPTION
Variable Stars. in the. Survey. Andrzej Udalski Warsaw University Observatory. 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 - PowerPoint PPT PresentationTRANSCRIPT
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Variable Stars
Andrzej Udalski
Warsaw University Observatory
in the Survey
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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. Billion stars regularly monitored
http://ogle.astrouw.edu.pl
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Las Campanas Observatory, Chile
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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 (~7 Moon disks), scale – 0.26”/pixel
• 20 sec. reading time
• First light September 7, 2009
• Regular observations since March 4/5, 2010
• 30-50 TB of raw data per year
• ~3 mmag accuracy (DIA photometry since 2001)
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OGLE-IV Nowa Kamera Mozaikowa
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OGLE-IV Sky
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OGLE-IV 2013 BLG SKY
Cadence: red – ~30 epochs/night
yellow – ~10 epochs/night
green – ~3 epochs/night
blue – ~1 epoch/night
cyan – ~1 epoch /2 nights
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Current O-IV MC Survey – 600 square degrees
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OGLE-IV Galactic Disk (l<0)
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Non-Variable Stars
• ~billion stars monitored – VI CMDs
• O-III Photometric Maps:
LMC – 35 million stars, SMC – 6.2 million stars, GB – 380 million stars, GD – 9 million stars
• Structure studies
• Reddening maps
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Variable Stars
Geometrical
Physical
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New Classes of Variable Objects: Microlensing Phenomena
Bohdan Paczyński (1940—2007)
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Gravitational Microlensing
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OGLE-I #1
Microlenses: Discovery of the first events toward the GB (1993).
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Microlensing: Three Main Scientific Channels
• Search for Dark Matter
• Galactic Structure
• Extrasolar Planets – Planetary Microlensing
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First Binary Microlensing (1994)
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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
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2012 Planetary Microlensing
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Free-Floating Planets
• Microlensing event characteristic time: 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 : ~50 events/season 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
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OGLE Variable Star Statistics
OIII-CVS: OGLE-III Catalog of Variable Stars
(Soszyński et al. 2013, Acta Astronomica 63, 21; Part XV)
(Pietrukowicz et al. 2013, Acta Astronomica 63, 115; Part XVI)
• LMC: 3361 Classical Cepheids, 280 Pop. II Cepheids, 24906 RR Lyrae stars, 2786 Delta Scuti, 91995 LPVs, 26121 Eclipsing Binaries
• SMC: 4630 Classical Cepheids, 43 Pop II Cepheids, 2475 RR Lyrae stars, 19384 LPVs
• Galactic Bulge: 16836 RR Lyrae (~400 from SGR Dwarf Galaxy), 32 Classical Cepheids, 357 Pop II Cepheids, 232406 LPVs
• Galactic Disk: ~30000 (11 600 Eclipsing binaries, 40 DNe)
• Total > 400000
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OGLE Pulsating Stars
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Cepheids in the MCs
Hubble constant determinationis based on OGLE PL relations
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Cepheids in the SMC
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RR Lyrae Stars in the LMC
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RR Lyrae Stars in the SMC
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MC: LPVs
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Delta Scuti in the LMC
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LMC
SMC
Magellanic Bridge
Classical Cepheids in the Magellanic Clouds
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LMC
SMC
Magellanic Bridge
RR Lyrae Stars in the Magellanic Clouds
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Eclipsing Stars (Great distance indicators)
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Distance to the LMC
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Transiting Planets
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Transiting OGLE Exoplanets (2001– 2004)
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Ellipsoidal Variables on Eccentric Orbits
model
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X-ray Sources Optical Counterparts (XROM System)
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R CrB (RCOM System)
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OGLE-IV Transient Detection System
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Quasars Behind the Magellanic Clouds
• Candidates selected based on long term variability in the OGLE-III data, IR brightness and X-ray detection
• Spectroscopic campaigns for confirmation (AAT)
• Spectacular results: >700 new quasars behind the MCs (the farthest at z=3.99)
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GB Cepheids
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GB RR Lyrae
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Galactic Bulge – Structure
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GB LPVs
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Galactic Disk Survey
• VI Photometry of the strip -3<b<+3 around the Galactic Disk (210<l<360); several epochs; VI maps up to I~22 mag
• Shallow (I<18.5 mag) variability survey: 100-150 epoch per field (2013-2014 observing seasons)
• Test O-III Galactic Disk: >7 square degrees (high cadence O-III planetary transit fields) in Carina:
~30 000 variable stars: 20 CEP, 50 RRL, 800 DSCT, 11600 ECL, 14000 RSCVn, 40 DNe, 100 UVCET
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OGLE-CEP-0227
MCeph = 4.14 ± 0.05 M☼
MPul = 3.98 ± 0.29 M☼
Cepheid pulsation mass in agreement with measured dynamical mass
•2008 r.: discovery of OGLE-CEP-0227
•2009-2010: high precision spectroscopy, ARAUCARIA
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A RR Lyrae Star in Eclipsing System in the BLG?
Odkrycie – OGLE (prof. Igor Soszyński, 2010 r.)Follow up – Araucaria (prof. Grzegorz Pietrzyński, 2011 r.)
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Nova Scorpii 2008 (V1309 SCO) – OGLE
• Star in the fields regularly observed since 2001
• Unique possibility of tracing the star behavior before eruption
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V1309 Sco – Conclusions
• First observations of the stellar merger• Next candidate: OGLE-2002-BLG-360
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http://ogle.astrouw.edu.pl