Direct detection of substellar and planetary companions to white dwarfs

DEPARTMENT OF PHYSICS AND ASTRONOMY

Direct detection of substellar and Direct detection of substellar and planetary companions to white dwarfsplanetary companions to white dwarfs

Matt BurleighMatt Burleigh

Dr. Matt Burleigh www.star.le.ac.uk/~mbu

with thanks to:with thanks to:

• Jay Farihi, Sarah Casewell, Martin Barstow, Richard Jay Farihi, Sarah Casewell, Martin Barstow, Richard Jameson, Katherine Lawrie (Leicester)Jameson, Katherine Lawrie (Leicester)

• Paul Steele (MPA Garching)Paul Steele (MPA Garching)• Francesca Faedi (Belfast)Francesca Faedi (Belfast)• Paul Dobbie (AAO)Paul Dobbie (AAO)• Fraser Clarke (Oxford), Emma Hogan (Gemini South)Fraser Clarke (Oxford), Emma Hogan (Gemini South)• Ted von Hippel, Fergal Mullally (Kepler)Ted von Hippel, Fergal Mullally (Kepler)• Hans Zinnecker, Suzanne Friedrich Hans Zinnecker, Suzanne Friedrich


OverviewOverview

• IR searches for substellar companionsIR searches for substellar companions– UKIDSS survey resultsUKIDSS survey results

• Direct imaging: into the planetary regimeDirect imaging: into the planetary regime– Ground-based: DODO surveyGround-based: DODO survey– Space-based: Spitzer surveySpace-based: Spitzer survey

• Latest results: a close WD+ Tdwarf binary Latest results: a close WD+ Tdwarf binary in an open clusterin an open cluster

• A transit survey of WDs with SuperWASPA transit survey of WDs with SuperWASP


Direct imaging of planets around white dwarfsDirect imaging of planets around white dwarfsBurleigh, Clarke & Hodgkin 2002, MNRAS, 331, L41 Burleigh, Clarke & Hodgkin 2002, MNRAS, 331, L41

• Ideal targets for direct imaging (and Ideal targets for direct imaging (and spectroscopy) of exoplanets:spectroscopy) of exoplanets:– Improve contrast problem: WDs up to ~10Improve contrast problem: WDs up to ~1044x fainter x fainter

than their progenitorsthan their progenitors– Improve resolution problem through widening of orbitsImprove resolution problem through widening of orbits

• M(MS) / M(WD) (Jeans 1924)M(MS) / M(WD) (Jeans 1924)

– Indirectly study planetary systems around WD Indirectly study planetary systems around WD progenitors: early-type stars (B,A,F), intermediate progenitors: early-type stars (B,A,F), intermediate masses (1.5<M<8Mmasses (1.5<M<8Msunsun))

– White dwarfs common in solar neighbourhoodWhite dwarfs common in solar neighbourhood– White dwarf ages are well constrainedWhite dwarf ages are well constrained

• Planetary companions of WDs will be old, Planetary companions of WDs will be old, mature gas giantsmature gas giants– 200 < T200 < Teffeff < 600K < 600K

– > few x 10> few x 1088 years old years old– Detectable at ages up to several GyrDetectable at ages up to several Gyr– Most direct imaging programmes target young starsMost direct imaging programmes target young stars


The end of our solar systemThe end of our solar system


Evidence for old planetary systemsEvidence for old planetary systems

1.1. Planets have been found by radial velocity technique around Planets have been found by radial velocity technique around evolved giant starsevolved giant stars

– 9% of stars 1.3<M<1.9M9% of stars 1.3<M<1.9Msun sun have planets (Johnson et al. 2007)have planets (Johnson et al. 2007)– >3% of stars M>1.8M>3% of stars M>1.8Msunsun have planets >5M have planets >5MJup Jup (Lovis and Mayor 2007)(Lovis and Mayor 2007)

2.2. White dwarfs have been identified as wide companions of White dwarfs have been identified as wide companions of planet-hosting starsplanet-hosting stars

– eg CD-38 10980 (Mayor et al. 2004), eps Ret (Raghavan et al. 2006, Chauvin et al. eg CD-38 10980 (Mayor et al. 2004), eps Ret (Raghavan et al. 2006, Chauvin et al. 2006, Farihi et al. 2011)2006, Farihi et al. 2011)

3.3. Growing number of brown dwarf companions in close and Growing number of brown dwarf companions in close and wide orbitswide orbits

– eg Maxted et al. 2006, Steele et al. 2011, Girven et al. 2011, Debes et al. 2011eg Maxted et al. 2006, Steele et al. 2011, Girven et al. 2011, Debes et al. 2011

4.4. Metal-rich circumstellar dust and gas disks discovered Metal-rich circumstellar dust and gas disks discovered around white dwarfsaround white dwarfs

– See various papers by eg Jay Farihi & collaborators, Boris Gaensicke & friendsSee various papers by eg Jay Farihi & collaborators, Boris Gaensicke & friends


Dust disks around white dwarfsDust disks around white dwarfs

• A dozen WDs are known to be surrounded by dust disksA dozen WDs are known to be surrounded by dust disks• Disks identified as near-IR and mid-IR excesses, 500Disks identified as near-IR and mid-IR excesses, 500ooK < T < 1200K < T < 1200ooKK• Disks within a few solar radii of the WDsDisks within a few solar radii of the WDs• Material within the disks is being accreted onto the WD atmosphereMaterial within the disks is being accreted onto the WD atmosphere

– Finally explains WDs with metal-polluted atmospheresFinally explains WDs with metal-polluted atmospheres


Dust disks around white dwarfsDust disks around white dwarfs

• Disks dominated by silicatesDisks dominated by silicates

• Disk forms from tidal disruption asteroid Disk forms from tidal disruption asteroid – Mass of GD362 disk suggests Mars-sized bodyMass of GD362 disk suggests Mars-sized body

• Suggests up to 20% of WDs may have rocky Suggests up to 20% of WDs may have rocky companionscompanions– If all polluted WDs have accreted terrestrial If all polluted WDs have accreted terrestrial

material at some pointmaterial at some point

• But asteroids have to be moved by But asteroids have to be moved by something: something: – Where are the perturbing giant planets?Where are the perturbing giant planets?


HR8799 as a white dwarf…HR8799 as a white dwarf…

• HR8799: A5V 1.2-1.8MHR8799: A5V 1.2-1.8Mjupjup 39pc 30-160Myr old 39pc 30-160Myr old• Planets: 7MPlanets: 7Mjup jup @ 68AU, 10M@ 68AU, 10Mjupjup @ 38AU, 10M @ 38AU, 10Mjupjup @ 24AU @ 24AU

• Will evolve after 1.75Gyr to a 0.58MWill evolve after 1.75Gyr to a 0.58Msun sun white dwarfwhite dwarf• Planet orbits expand by factor ~3 to ~200AU,~120AU & 75AUPlanet orbits expand by factor ~3 to ~200AU,~120AU & 75AU

• Let WD cool to 10,000K over ~0.5Gyr….system age now 2.25Gyr…Let WD cool to 10,000K over ~0.5Gyr….system age now 2.25Gyr…• 10M10Mjup jup planet will be J=23.8 @39pc, or J=22.4 @ 20pc planet will be J=23.8 @39pc, or J=22.4 @ 20pc

– How common are HR8799-like systems? How common are HR8799-like systems?


IR searches for substellar companions:IR searches for substellar companions:UKIDSS survey resultsUKIDSS survey results

• Historical searches for brown dwarf companions to Historical searches for brown dwarf companions to WDs going back to 1980sWDs going back to 1980s– eg eg Probst (1983), Zuckerman & Becklin (1987), Wachter et al. (2003), Farihi et al. Probst (1983), Zuckerman & Becklin (1987), Wachter et al. (2003), Farihi et al.

(2005), Dobbie et al. (2005), Tremblay & Bergeron (2007)(2005), Dobbie et al. (2005), Tremblay & Bergeron (2007)

– GD165B (L4), GD1400B (L6/7), WD0137-349B (L8) GD165B (L4), GD1400B (L6/7), WD0137-349B (L8)

• UKIDSS surveyUKIDSS survey– ~dozen new BD candidates~dozen new BD candidates– Several confirmed (eg PHL5038, Several confirmed (eg PHL5038, Steele et al. 2009, A&A, 500, Steele et al. 2009, A&A, 500,

12071207))– WD+L fraction >0.4+/-0.3%WD+L fraction >0.4+/-0.3%– WD+T fraction >0.2%WD+T fraction >0.2%– WD+BD fraction >0.5+/-0.3%WD+BD fraction >0.5+/-0.3%– Steele et al. 2011, MNRAS, 416, 2768Steele et al. 2011, MNRAS, 416, 2768– See also similar study by See also similar study by Girven et al. 2011, MNRAS, 417, Girven et al. 2011, MNRAS, 417,

12101210– Parallel study for very wide binaries in UKIDSS discovered a Parallel study for very wide binaries in UKIDSS discovered a

WD+T4.5 (WD+T4.5 (Day-Jones et al. 2009Day-Jones et al. 2009) )


Direct Imaging Searches Around White Direct Imaging Searches Around White Dwarfs: The DODO projectDwarfs: The DODO project

DDegenerate egenerate OObjects around bjects around DDegenerate egenerate OObjectsbjects

With Emma Hogan (now Gemini South) and Fraser Clarke (Oxford)

The idea: Burleigh et al. 2002, MNRAS, 331, L41The idea: Burleigh et al. 2002, MNRAS, 331, L41Results: Burleigh et al. 2008, MNRAS, 386, L5Results: Burleigh et al. 2008, MNRAS, 386, L5

and Hogan et al. 2009, MNRAS, 396, 2074and Hogan et al. 2009, MNRAS, 396, 2074


• ~40 white dwarfs within 20pc, ages <2-3Gyr~40 white dwarfs within 20pc, ages <2-3Gyr• J band survey, depths J=23-24J band survey, depths J=23-24

^~90”

V

< ~120” >


Van Maanen’s Star (d=4.4pc)Van Maanen’s Star (d=4.4pc)

• DODO ground-based J-band imaging:DODO ground-based J-band imaging:– No companion found >7+/-1MNo companion found >7+/-1MJupJup (300+/-20K) at separations from 3”-45” / 15AU – 200AU (300+/-20K) at separations from 3”-45” / 15AU – 200AU– Separations around progenitor: 3 - 40AUSeparations around progenitor: 3 - 40AU

• Spitzer mid-IR photometry:Spitzer mid-IR photometry:– No unresolved companions > 10+/-2 MNo unresolved companions > 10+/-2 M jupjup

• Burleigh et al. 2008, MNRAS, 386, L5Burleigh et al. 2008, MNRAS, 386, L5

– No resolved companions > 4MNo resolved companions > 4MJupJup• Farihi et al. (2008)Farihi et al. (2008)


A candidate?A candidate?

• Candidate mass ~7MCandidate mass ~7MJupJup

WD


No candidate :(No candidate :(

• 3rd epoch in 2008 refuted candidate3rd epoch in 2008 refuted candidate


Limits on giant planets at white Limits on giant planets at white dwarfs: massdwarfs: mass

– <5% of WDs have resolved substellar companions above deuterium <5% of WDs have resolved substellar companions above deuterium burning limit (13Mburning limit (13MJupJup))

– <7% of WDs have resolved substellar companions >10M<7% of WDs have resolved substellar companions >10MJupJup

– <1/3rd of WDs have resolved substellar companions >6M<1/3rd of WDs have resolved substellar companions >6MJupJup


Limits on giant planets at white Limits on giant planets at white dwarfs: temperaturedwarfs: temperature

– <4% of WDs have resolved substellar companions >500K<4% of WDs have resolved substellar companions >500K– <7% of WDs have resolved substellar companions >400K<7% of WDs have resolved substellar companions >400K


Maximum and minimum orbital Maximum and minimum orbital separations probed by DODOseparations probed by DODO


Comparison with Spitzer limits on Comparison with Spitzer limits on unresolved companionsunresolved companions

(Farihi et al 2008, 34 targets)(Farihi et al 2008, 34 targets)

DODO DODO ((resolved, >few resolved, >few 10s AUs10s AUs))

Spitzer Spitzer ((unresolved, unresolved, <few 10s AUs<few 10s AUs))

>13M>13MJupJup <5%<5% <3%<3%

>10M>10MJupJup <7%<7% <4%<4%

>6M>6MJupJup <1/3<1/3 <12%<12%


Spitzer warm mission programmeSpitzer warm mission programme

• Repeat observations of ~90 white dwarfs originally Repeat observations of ~90 white dwarfs originally observed 2004/5observed 2004/5– Prog ID: 60161Prog ID: 60161– Title: Title: “Cool, spatially resolved substellar & exoplantary “Cool, spatially resolved substellar & exoplantary

analogues at white dwarfs”analogues at white dwarfs”– PI: Burleigh, co-Is Farihi, Steele, Mullally, von Hippel

• Look for common proper motion companionsLook for common proper motion companions– 4.5micron band only4.5micron band only


Spitzer 4.5micron imageSpitzer 4.5micron imageGJ3483 (LTT3059 / WD0806-661) GJ3483 (LTT3059 / WD0806-661)

I am the white dwarf

I maybe a planet… or a brown dwarf

130” / 2500AU




Proper motionProper motion

• PM error +/-25mas/yrPM error +/-25mas/yr

WDCompanion


Candidate parametersCandidate parameters

• WD WD – 0.62M0.62Msunsun

,,

– Progenitor mass 1.8-2.4MProgenitor mass 1.8-2.4Msunsun

– Total age 1.2-2.0GyrTotal age 1.2-2.0Gyr

– Distance 19.2pcDistance 19.2pc

• CandidateCandidate– 4.5micron mag = 16.75+/-0.084.5micron mag = 16.75+/-0.08

– 6-10M6-10MJupJup

– 310-380K310-380K

• BinaryBinary– Projected separation 130” / 2500AUProjected separation 130” / 2500AU

– Original separation 700AUOriginal separation 700AU



Candidate parametersCandidate parameters

• WD WD – 0.62M0.62Msunsun

,,

– Progenitor mass 1.8-2.4MProgenitor mass 1.8-2.4Msunsun

– Total age 1.2-2.0GyrTotal age 1.2-2.0Gyr

– Distance 19.2pcDistance 19.2pc

• CandidateCandidate– 4.5micron mag = 16.75+/-0.084.5micron mag = 16.75+/-0.08

– 6-10M6-10MJupJup

– 310-380K310-380K

• BinaryBinary– Projected separation 130” / 2500AUProjected separation 130” / 2500AU

– Original separation 700AUOriginal separation 700AU


Y band observationY band observation

• AAT / IRIS2 2hours exposure on 25AAT / IRIS2 2hours exposure on 25 thth March 2011 March 2011• No detectionNo detection• SensitivitySensitivity

– Recover 50% of injected fake stars at 21.1 Recover 50% of injected fake stars at 21.1


J-band observationsJ-band observations

• Rodriguez et al. 2011,ApJ, 732, 1222; Luhman et al Rodriguez et al. 2011,ApJ, 732, 1222; Luhman et al 2012, ApJ, 744, 1352012, ApJ, 744, 135

• No detection to J=23.9 (3 sigma)No detection to J=23.9 (3 sigma)– J-[4.5] > 7J-[4.5] > 7– Redder than any known T dwarf – a Y dwarf?Redder than any known T dwarf – a Y dwarf?

– Suggest mass 6-9MSuggest mass 6-9MJupJup and 310K < T and 310K < Teff eff < 350K < 350K


Planet or brown dwarf?Planet or brown dwarf?

• Is GJ3483B a brown dwarf or a planet?Is GJ3483B a brown dwarf or a planet?• Forget deuterium burning limit as the discriminator Forget deuterium burning limit as the discriminator

– can we classify by formation mechanism?can we classify by formation mechanism?

• Original Original projectedprojected separation ~700AU separation ~700AU– Too large for core accretion in a diskToo large for core accretion in a disk– Suggests disk fragmentation -> BDSuggests disk fragmentation -> BD

• Rodriguez et al. 2011Rodriguez et al. 2011

• But unstable, eccentric orbits expected in end states of stellar But unstable, eccentric orbits expected in end states of stellar evolutionevolution– Debes & Sigurdsson 2002, Villaver & Livio 2007, Veras et al. 2011Debes & Sigurdsson 2002, Villaver & Livio 2007, Veras et al. 2011

– Disk of 2MDisk of 2Msun sun star may be massive enough to make 6Mstar may be massive enough to make 6MJupJup companion companion

– Progenitor could be an HR8799-like system Progenitor could be an HR8799-like system • A5V+7MA5V+7MJupJup @68AU + 10M @68AU + 10MJupJup@38AU + 10M@38AU + 10MJupJup@24AU@24AU


Spitzer survey completenessSpitzer survey completeness





Black: Spitzer resolvedRed: DODO resolved(Hogan et al. 2009)Green: Spitzer unresolved (Farihi et al. 2008)


A WD+T dwarf close binary in A WD+T dwarf close binary in PraesepePraesepe

• RV & V band variability (4.2hr) in a WD in Praesepe cluster• M sin i > 25MJup

• Non-detection in NIR and mid-IR (Spitzer IRAC) limits spectral type <T5• At age of Praesepe (625Myr) M<30MJup

• Strict age limit gives tight constraints on common envelope evolution parameters• Original orbit ~2AU (max extent of AGB

envelope)• WD progenitor 3.5Msun/B9V

• How did original binary form?• Most likely, capture early in cluster lifetime• Is this a significant method to populate the

“brown dwarf desert”?

For more details see poster by Sarah Casewell


A search for eclipsing and transiting A search for eclipsing and transiting planets with SuperWASPplanets with SuperWASP

• SuperWASP world’s most successful ground-based transit survey (>80 planets so far) • Has observed ~200 WDs since 2004

• 1% photometry to V=13, detection limit V~15• No eclipsing or transiting companions detected • Placed (weak!) limits on incidence of such objects in close orbits around these white dwarfs

• accounting for observing efficiency & co-variant noise in data• Limiting factors:

• cadence: 8min for WASP v transit times of 1-few mins• unknown frequency of close planetary companions

• Survivors of common envelope evolution?• 2nd generation planets?

Faedi, West, Burleigh, Goad, & Hebb, (2011), MNRAS, 410, 899 and various conference proceedings since 2007

Please read the poster for more details


Open questions, future directionsOpen questions, future directions• How common are GJ3483-like objects? How common are GJ3483-like objects?

– More direct imaging searches for wide companionsMore direct imaging searches for wide companions– What are their formation mechanisms? What are their formation mechanisms?

• Disk fragmentation?Disk fragmentation?

• Core accretion and subsequent ejectionCore accretion and subsequent ejection??

• Where are the perturbers that help create dust disks Where are the perturbers that help create dust disks around white dwarfs?around white dwarfs?– Mid-IR photometric searches; adaptive optics & HSTMid-IR photometric searches; adaptive optics & HST

• What is the lowest mass that can survive CE evolution What is the lowest mass that can survive CE evolution intact?intact?– Transit/eclipse searchesTransit/eclipse searches

• What is the orbital period distribution for substellar What is the orbital period distribution for substellar companions?companions?– Are there “deserts”?Are there “deserts”?

• Can rocky planets exist in close orbits to WDs?Can rocky planets exist in close orbits to WDs?– Transit searchesTransit searches

• Can 2Can 2ndnd generation planets form? generation planets form?– Hot, young gas giants, metal-rich terrestrial planets?Hot, young gas giants, metal-rich terrestrial planets?


The lowest mass companions to WDsThe lowest mass companions to WDsName Mass

(Mjup)Period a

(AU)Evolutionary status

Detection method

Comment Reference

GD66 b >2.4 ~7y >3AU WD Pulsation timing

Retracted Mullally et al. 2008

GJ3483 b(WD0806-661 b)

6-9 2500 WD Direct imaging

Y dwarf?310K<T<350K

Burleigh et al. 2012

Praesepe WD B 25-30

4.2hr 0.006 WD,Post-CE

Radial velocity

In Praesepe open cluster

See Sarah Casewell’s poster

WD0137-349 B 53 1.93hr 0.003 WD,Post-CE

Radial velocity

L8 dwarf, T~1300K

Maxted et al. 2006

PHL5038 B 55 55 WD Direct imaging

L8 dwarf, T~1400K

Steele et al. 2009

GD1400 B 60 9.98hr 0.009 WD,Post-CE

Radial velocity

L6/7 dwarf,T~1500K

Burleigh et al. 2012

LSPM 1459+0857 B

60-75

26500 WD Direct imaging

T4.5 dwarf, T~1000K

Day-Jones et al. 2011

NN Ser bNN Ser c

6.92.3

15.5y7.7y

5.43.4

Pre-CV(WD+M)

Eclipse timing

Beuermann et al. 2010

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Direct detection of substellar and planetary companions to white dwarfs

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