department of physics and astronomy searching for dying solar systems: planets around white dwarfs...
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![Page 1: DEPARTMENT OF PHYSICS AND ASTRONOMY Searching for dying solar systems: Planets around White Dwarfs Matt Burleigh, Leicester Fraser Clarke, Oxford Emma](https://reader035.vdocuments.net/reader035/viewer/2022062715/56649d7d5503460f94a601f6/html5/thumbnails/1.jpg)
DEPARTMENT OF PHYSICS AND ASTRONOMY
Searching for dying solar systems:Searching for dying solar systems:Planets around White DwarfsPlanets around White Dwarfs
Matt Burleigh, LeicesterMatt Burleigh, LeicesterFraser Clarke, OxfordFraser Clarke, Oxford
Emma Hogan, LeicesterEmma Hogan, LeicesterSimon Hodgkin, CambridgeSimon Hodgkin, Cambridge
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Dr. Matt Burleigh RAS November 2004
Improving ContrastImproving Contrast
• To understand extrasolar planets, we need To understand extrasolar planets, we need their light!their light!
• None of the radial velocity planets can be None of the radial velocity planets can be imaged with current technologyimaged with current technology
• Planet is too faint and too close to the starPlanet is too faint and too close to the star• Two solutions;Two solutions;
– Remove the starlight (technology: AO, Remove the starlight (technology: AO, coronography, interferometry)coronography, interferometry)
– Remove the star (stellar evolution)Remove the star (stellar evolution)
Observe White Dwarfs!Observe White Dwarfs!
Above: Gl229B – brown dwarf companion to nearby M dwarf
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Dr. Matt Burleigh RAS November 2004
Surviving the RGBSurviving the RGB
• Red Giant expands to maximum ~5AURed Giant expands to maximum ~5AU• Planets inside 5AU are destroyed by Planets inside 5AU are destroyed by
Red GiantRed Giant• Planets outside ~5AU will migrate Planets outside ~5AU will migrate
outward due to mass loss and surviveoutward due to mass loss and survive– Dynamical time ~10-30 yrDynamical time ~10-30 yr– mass loss time ~1000-10000yrmass loss time ~1000-10000yr– planets planets stay boundstay bound
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Dr. Matt Burleigh RAS November 2004
The Benefits of White DwarfsThe Benefits of White Dwarfs
• WD's are ~10,000 times fainter than WD's are ~10,000 times fainter than their progenitorstheir progenitors
• => Huge => Huge contrast gaincontrast gain
• Planets orbit increasesPlanets orbit increases
• => Big => Big resolution gainresolution gain
• And >120 WDs within 20pcAnd >120 WDs within 20pc
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Dr. Matt Burleigh RAS November 2004
The Benefits of White DwarfsThe Benefits of White Dwarfs
• PLUS the WD progenitors are more PLUS the WD progenitors are more massive than solar-type starsmassive than solar-type stars– Mainly A and B starsMainly A and B stars– Not generally being targeted by radial velocity Not generally being targeted by radial velocity
programmesprogrammes
• So by targeting WDs we are probing So by targeting WDs we are probing frequency of planets around massive stars frequency of planets around massive stars
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Dr. Matt Burleigh RAS November 2004
Planet brightness v agePlanet brightness v age
Solid lines Burrows 1997 models, dashed lines Burrows 2002 models
Models assume evolution in isolation: no addition heating source or reflection component
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Dr. Matt Burleigh RAS November 2004
Imaging planets around white dwarfsImaging planets around white dwarfs
• Large format NIR cameras on 8m-class Large format NIR cameras on 8m-class telescopestelescopes– Typically reach Typically reach J~24 in 1 hourJ~24 in 1 hour
(e.g. VLT+ISAAC, Gemini+NIRI)(e.g. VLT+ISAAC, Gemini+NIRI)– Comparable with predicted magnitudes of Comparable with predicted magnitudes of
planets around nearby white dwarfsplanets around nearby white dwarfs
• No immediate need for AONo immediate need for AO– Searching outside star’s PSFSearching outside star’s PSF
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Dr. Matt Burleigh RAS November 2004
Cool companions to WDsCool companions to WDs
• Becklin & Zuckerman, Probst in the 1980sBecklin & Zuckerman, Probst in the 1980s– IR excess in WDs may indicate cool companionIR excess in WDs may indicate cool companion– First L dwarf discovered is a companion to a WD, GD165First L dwarf discovered is a companion to a WD, GD165
• But brown dwarfs are not common companions to WDsBut brown dwarfs are not common companions to WDs– Only one more found so far (GD1400B, L6/7, Farihi et al. 2004) Only one more found so far (GD1400B, L6/7, Farihi et al. 2004) – Confirms brown dwarf desert at wide separationsConfirms brown dwarf desert at wide separations
• No companions >10MNo companions >10MJupJup found among Hyades WDs found among Hyades WDs– Zinnecker & Friedrich, in prep. (HST/NICMOS)Zinnecker & Friedrich, in prep. (HST/NICMOS)
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Dr. Matt Burleigh RAS November 2004
StrategyStrategy• Select young (<3Gyr), nearby (<20pc) white Select young (<3Gyr), nearby (<20pc) white
dwarfs dwarfs – (0.2”yr < PM < few “/yr)(0.2”yr < PM < few “/yr)– Sample ~40 starsSample ~40 stars– Progenitors mainly A/B stars (short main Progenitors mainly A/B stars (short main
sequence lifetimes)sequence lifetimes)• Obtain deep wide IR (J) images.Obtain deep wide IR (J) images.
– Total exp time ~1hrTotal exp time ~1hr– Depth J~23.5 (GN) to ~24 (VLT) Depth J~23.5 (GN) to ~24 (VLT) – Image quality typically 0.4”-0.6”Image quality typically 0.4”-0.6”
• Wait 1—2 years…Wait 1—2 years…– Obtain 2Obtain 2ndnd epoch images of epoch images of allall systems to systems to
check for common proper motion companionscheck for common proper motion companions
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Dr. Matt Burleigh RAS November 2004
Parameter spaceParameter space
• For comparison with For comparison with other planet search other planet search techniques;techniques;– Planet mass; >5 MjupPlanet mass; >5 Mjup– Orbit; 5—1000 AUOrbit; 5—1000 AU– Age; 0.5—3 GyrAge; 0.5—3 Gyr– Star mass; 2—7 Msun Star mass; 2—7 Msun
(A and B stars) (A and B stars)• Complimentary to Complimentary to
other search other search techniquestechniques
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Dr. Matt Burleigh RAS November 2004
Not a Not a discoverydiscovery
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Dr. Matt Burleigh RAS November 2004
• White dwarfsWhite dwarfs– Image depth J~24Image depth J~24
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Dr. Matt Burleigh RAS November 2004
Two epochs for Proper MotionTwo epochs for Proper Motion
• One epoch in One colour tells us nothing.One epoch in One colour tells us nothing.
• Faint objects Faint objects couldcould be faint companions, be faint companions, or they could simply be far away…or they could simply be far away…
• AnyAny object in the field could be a object in the field could be a companion!! (orbital expansion)companion!! (orbital expansion)
• 22ndnd epoch observations are needed to epoch observations are needed to confirm companions via proper motion.confirm companions via proper motion.
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Dr. Matt Burleigh RAS November 2004
• Two epochsTwo epochs– June 2002 GS+Flamingos-IJune 2002 GS+Flamingos-I– October 2003 VLT+ISAACOctober 2003 VLT+ISAAC– WD motion ~1” between imagesWD motion ~1” between images– Image depth J~23.5Image depth J~23.5
^~90”
V
< ~120” >
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Dr. Matt Burleigh RAS November 2004
Motions in fieldMotions in field
• Arrows show direction Arrows show direction and degree of motion x and degree of motion x factor 20factor 20
• WD moved ~9 pixels in WD moved ~9 pixels in 15 months (~1”)15 months (~1”)
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Dr. Matt Burleigh RAS November 2004
A non-detectionA non-detection
• Circles: Circles: 11scatter on scatter on distribution of distribution of proper motions of proper motions of background background objectsobjects
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Dr. Matt Burleigh RAS November 2004
A detection?A detection?
• Circles: 1 error on PMs
• If associated, candidates are 7-10MJup
• Would have originally orbited at ~65AU & ~75AU
• First epoch June 2002, second June 2003
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Dr. Matt Burleigh RAS November 2004
Add third epoch (June 2004)Add third epoch (June 2004)
• Candidates have gone away!
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Dr. Matt Burleigh RAS November 2004
SummarySummary
• White dwarfs open up more parameter White dwarfs open up more parameter space for planet surveysspace for planet surveys– Direct imaging of planets >5MDirect imaging of planets >5MJupJup
– Probing frequency of planets around massive Probing frequency of planets around massive stars (>2Mstars (>2MSunSun))
• Sensitivity required is achievable with 8m Sensitivity required is achievable with 8m telescopes in near-IRtelescopes in near-IR
• Our survey is beginning to reach maturityOur survey is beginning to reach maturity– 2 epochs for 12 systems 2 epochs for 12 systems – 40 systems by 200640 systems by 2006
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Dr. Matt Burleigh RAS November 2004
Further work….Further work….
• Is a sample of 40 enough? Is a sample of 40 enough? – Coronographic searches of nearby young stars Coronographic searches of nearby young stars
indicate frequency of companions indicate frequency of companions >5M>5MJupJup beyond 75AU is <3% beyond 75AU is <3%
(McCarthy & Zuckerman 2004)(McCarthy & Zuckerman 2004)
• Plus want to probe to lower masses (<5MPlus want to probe to lower masses (<5MJupJup))
– Spitzer mid-IR observations for photometric Spitzer mid-IR observations for photometric excesses (several programmes in progress)excesses (several programmes in progress)