detached wd/bd binaries as progenitors of cvs

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

Detached WD/BD binaries as Detached WD/BD binaries as progenitors of CVsprogenitors of CVs

Matt BurleighMatt Burleighwith Paul Steele, Francesca Faedi, Paul Dobbie (AAO) and Boris Gaensicke (Warwick)with Paul Steele, Francesca Faedi, Paul Dobbie (AAO) and Boris Gaensicke (Warwick)


MotivationMotivation• Investigate the known deficit of BD companions to main Investigate the known deficit of BD companions to main

sequence starssequence stars– McCarthy & Zuckerman (2004), Grether & Lineweaver (2006)McCarthy & Zuckerman (2004), Grether & Lineweaver (2006)

• WD gives an age constraint: benchmark BDs for testing WD gives an age constraint: benchmark BDs for testing evolutionary and atmospheric modelsevolutionary and atmospheric models– Pinfield et al. (2006)Pinfield et al. (2006)

• In close systems, irradiated BD provides a laboratory for testing In close systems, irradiated BD provides a laboratory for testing models of heated substellar atmospheres (hot Jupiters)models of heated substellar atmospheres (hot Jupiters)– WD0137-349WD0137-349

• Post-CE systems may provide another channel for CV evolutionPost-CE systems may provide another channel for CV evolution– Politano (2004)Politano (2004)

• Previous searches by e.g. Probst (1983), Zuckerman & Becklin (1987), Green, Ali & Previous searches by e.g. Probst (1983), Zuckerman & Becklin (1987), Green, Ali & Naperwotzki (2000), Farihi, Becklin & Zuckerman (2005), and using 2MASS: Wachter et al. Naperwotzki (2000), Farihi, Becklin & Zuckerman (2005), and using 2MASS: Wachter et al. (2003), Wellhouse et al. (2005), Holberg & Magargal (2005), Tremblay & Bergeron (2007) and (2003), Wellhouse et al. (2005), Holberg & Magargal (2005), Tremblay & Bergeron (2007) and Hoard et al. (2007)Hoard et al. (2007)


Irradiation of WD0137-349BIrradiation of WD0137-349B

• AAT + IRIS2 in July 2007AAT + IRIS2 in July 2007

Green - K (+/-14%)

Red - H (+/- 8%)

White - J (+/- 3%)


Post-CE binaries with BD Post-CE binaries with BD secondariessecondaries

• Constrain models of common Constrain models of common envelope evolutionenvelope evolution

• What is the lowest mass object that What is the lowest mass object that can survive a CE?can survive a CE?

• What fraction of CVs are born with What fraction of CVs are born with a BD secondary?a BD secondary?

• Growing number of CVs with Growing number of CVs with confirmed BD secondariesconfirmed BD secondaries– Including examples thought to have Including examples thought to have

formed directly from a detached formed directly from a detached WD+BD progenitorWD+BD progenitor

– e.g. SDSS J150722.30+523039.8, e.g. SDSS J150722.30+523039.8, Littlefair et al. (2007)Littlefair et al. (2007)


Known Known detacheddetached WD+BD binaries WD+BD binaries• Rare: only three confirmed systemsRare: only three confirmed systems• GD165GD165

– 120AU separation, L4 secondary120AU separation, L4 secondary– Becklin & Zuckerman (1988) Becklin & Zuckerman (1988)

• WD0137-349WD0137-349– P=116 mins, L8 secondary (0.053Msun)P=116 mins, L8 secondary (0.053Msun)– Maxted et al. (2006); Burleigh et al. (2006)Maxted et al. (2006); Burleigh et al. (2006)

• GD1400GD1400– P=9.98 hours, L6/7 secondaryP=9.98 hours, L6/7 secondary– Farihi & Christopher (2004), Burleigh et al. (2009)Farihi & Christopher (2004), Burleigh et al. (2009)

• Fraction of L dwarf companions <0.5% Fraction of L dwarf companions <0.5% – (Farihi et al. 2005, survey of >300 WDs)(Farihi et al. 2005, survey of >300 WDs)

• One companion on M/L border found among ~150 WDs One companion on M/L border found among ~150 WDs observed by Spitzer observed by Spitzer – PG1234+482 (Mullally et al. 2007; Steele et al. 2007)PG1234+482 (Mullally et al. 2007; Steele et al. 2007)

• A handful of other WD + A handful of other WD + ultracool dwarfultracool dwarf binaries known binaries known


UKIDSSUKIDSS

• UKIRT Infrared Deep Sky Survey• LAS (Large Area Survey) - 4000 sq. deg

• (~20% of northern sky, coincident with SDSS)• Limiting magnitudes - Y=20.2, J=19.6, H=18.8 & K=18.2 (5 sigma)

• 2-3 mags deeper than 2MASS


Searching for unresolved WD+BD binaries in UKIDSSSearching for unresolved WD+BD binaries in UKIDSS

• Cross-correlate UKIDSS LAS Cross-correlate UKIDSS LAS DR4 release (1060 sq. deg) with DR4 release (1060 sq. deg) with – SDSS DR4 spectroscopically id-ed SDSS DR4 spectroscopically id-ed

WDs (Eisenstein et al. 2006)WDs (Eisenstein et al. 2006)– McCook and Sion WDsMcCook and Sion WDs

• J-H v H-K plot provides an initial J-H v H-K plot provides an initial selectionselection

• Better method: model each WD Better method: model each WD SED, first with BBs and finally SED, first with BBs and finally with model atmospheres (DAs with model atmospheres (DAs only)only)– Identify WDs with >3 sigma Identify WDs with >3 sigma

excesses at H and Kexcesses at H and K


ResultsResults

• 922 SDSS WDs in UKIDSS DR4922 SDSS WDs in UKIDSS DR4– + a further 84 brighter WDs from McCook & Sion+ a further 84 brighter WDs from McCook & Sion

• But DR4 incomplete: many stars missing But DR4 incomplete: many stars missing photometry at one of J, H or Kphotometry at one of J, H or K

• After eliminating known WD+dMs, non-DAs and After eliminating known WD+dMs, non-DAs and DAs missing photometry at H or K:DAs missing photometry at H or K:– 254 DAs with photometry at both H and K254 DAs with photometry at both H and K

• 8 with late M dwarf (M7-9) companions 8 with late M dwarf (M7-9) companions • 5 candidate L dwarf companions5 candidate L dwarf companions• 1 candidate T dwarf companion 1 candidate T dwarf companion


WD+L4

WD+L6

WD+L8


PHL5038 PHL5038 = SDSS J222030.68-004107.3= SDSS J222030.68-004107.3

• BB=18, UKIDSS =18, UKIDSS KK=16.7=16.7• Follow-up imaging and spectroscopy Follow-up imaging and spectroscopy

with Gemini-North + NIRIwith Gemini-North + NIRI• Resolved at 0.92” (=55AU projected)Resolved at 0.92” (=55AU projected)• L8 companion (T~1600K, L8 companion (T~1600K,

M~0.055Msun @ 2-3Gyr)M~0.055Msun @ 2-3Gyr)• WD T=8000+/-100K, M=0.72+/-WD T=8000+/-100K, M=0.72+/-

0.15Msun, d=64+/-10pc0.15Msun, d=64+/-10pc• 4th known WD+BD detached system, 4th known WD+BD detached system,

2nd wide2nd wide• Steele et al. 2009 Steele et al. 2009

K


Frequency of close, detached Frequency of close, detached WD+BD binariesWD+BD binaries

• PHL5038 is flagged as partially resolved in PHL5038 is flagged as partially resolved in UKIDSSUKIDSS

• From evolutionary considerations, WD+BD binaries From evolutionary considerations, WD+BD binaries should either be wide (> few AU) or close (post-CE)should either be wide (> few AU) or close (post-CE)– Substellar companion either spirals inwards in CE, or Substellar companion either spirals inwards in CE, or

orbit expands outwards as Red Giant loses massorbit expands outwards as Red Giant loses mass– Farihi, Hoard & Wachter (2006)Farihi, Hoard & Wachter (2006)

• 2 of 5 L dwarf candidate companions classed as 2 of 5 L dwarf candidate companions classed as partially resolved (i.e. wide)partially resolved (i.e. wide)

• Single T dwarf candidate classed as “stellar” i.e. Single T dwarf candidate classed as “stellar” i.e. more likely to be a close binarymore likely to be a close binary


• Sensitive to companions L0 or later in 247 DAsSensitive to companions L0 or later in 247 DAs– Hence limit on frequency of close L-dwarf companions Hence limit on frequency of close L-dwarf companions

is < 1.2%is < 1.2%– c.f. Farihi et al. (2005) <0.5%, at all separations….c.f. Farihi et al. (2005) <0.5%, at all separations….

• Sensitive to companions T0 or later in 99 DAsSensitive to companions T0 or later in 99 DAs– Frequency of close T-dwarf companions is < 1%Frequency of close T-dwarf companions is < 1%

• Caveat: this assumes all the unresolved candidate binaries Caveat: this assumes all the unresolved candidate binaries are real and are post-CEare real and are post-CE


Next stageNext stage

• Need to spectroscopically confirm remaining Need to spectroscopically confirm remaining substellar candidates substellar candidates

• Determine periods and secondary masses for Determine periods and secondary masses for candidate close binariescandidate close binaries– Optical/IR photometric variability c.f. WD0137-349Optical/IR photometric variability c.f. WD0137-349– Radial velocities of brown dwarfs from Halpha Radial velocities of brown dwarfs from Halpha

emission (WD0137-349) or near-IR spectroscopy emission (WD0137-349) or near-IR spectroscopy (GD1400)(GD1400)

• Follow-up further candidates from future Follow-up further candidates from future UKIDSS data releasesUKIDSS data releases


Magnetic WDs in UKIDSSMagnetic WDs in UKIDSS• 13 MWDs in list of Kawka et al. (2007) have UKIDSS 13 MWDs in list of Kawka et al. (2007) have UKIDSS

photometryphotometry• One interesting system….One interesting system….


X-ray and observational Astronomy X-ray and observational Astronomy

Eclipsing WD binaries in WASPEclipsing WD binaries in WASP● Wide Angle Search for Planets

Search for eclipses and transits of WDs by unseen very low mass companions

(from BDs to Moon-size!)

FoV 7.8 x 7.8 degreesCadence 8 minutesLimit: V=13 (transiting planets)

V=15 (eclipses of WDs)

Instrument characteristics: - 8 Canon lenses 200mm f/1.8 - CCD 2048 x 2048 pixels - Field of View 7.8 x 7.8 degrees (61 sq. degrees) - magnitude limit =15 V mag. - photometric accuracy of 1% down to 1

Average number of points per star

15 new transiting planets discovered so far

WASP-1Orbital Period = 2.52 days

V magnitude 12.8


X-ray and observational Astronomy X-ray and observational Astronomy

Simulations white noise

Simulated WASP light curve of WD0137-349 (WD + Simulated WASP light curve of WD0137-349 (WD + 0.053Msun BD, P=116 mins)0.053Msun BD, P=116 mins) if it was an eclipsing binary if it was an eclipsing binary


• 194 white dwarfs V<15 in WASP fields

• Searched for eclipsing systems with periods from 2hrs - 15 days

• No eclipsing binaries discovered

• After full consideration of detection limits, conclude <1% of WDs have undetected substellar companions P<3hrs (0.125 days)

detached wd/bd binaries as progenitors of cvs

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