RIPLRIPLRadio Radio

Interferometric Interferometric Planet SearchPlanet Search

Geoffrey BowerGeoffrey Bower

UC BerkeleyUC BerkeleyCollaborators: Alberto Bolatto (UMD), Eric Ford (UFL),

Paul Kalas, Anna Treaster, Vince Viscomi (UCB)

MM Wavelength T Tauri MM Wavelength T Tauri Outburst in OrionOutburst in Orion

22ndnd most luminous stellar radio most luminous stellar radio outburstoutburst

Briefly, brightest object in Briefly, brightest object in nebulanebula

Required long baselines for Required long baselines for detectiondetection

Magnetized T Tauri outburstMagnetized T Tauri outburst Contemporaneous with X-ray Contemporaneous with X-ray

outburstoutburst Many such objects likely to be Many such objects likely to be

found by CARMA & ALMAfound by CARMA & ALMA

BIMA A configuration images(Bower, Plambeck, Bolatto, Graham, de Pater, McCrady, Baganoff 2004)

Orion Nebula ParallaxOrion Nebula Parallaxw/Star GMR-Aw/Star GMR-A

D=389 pc +/- 5%<0.1 mas/epochSandstrom, Peek, Bower, Bolatto,Plambeck 2007Astro-ph/0706.2361

Planets are Easy to Planets are Easy to DetectDetect

Companion to GJ 752B Companion to GJ 752B Detected w/Optical Detected w/Optical

AstrometryAstrometryPravdo & Shaklan 2009

White et al

Gudel 2002

Requirements of a Planet Requirements of a Planet SurveySurvey

Low mass, nearby starLow mass, nearby star Astrometric displacement ~ 1 masAstrometric displacement ~ 1 mas

Nonthermal radio emissionNonthermal radio emission S ~ 1 mJyS ~ 1 mJy F ~ GHzF ~ GHz Positional stability < 0.1 masPositional stability < 0.1 mas

Stable ImageStable Image Active, but not too activeActive, but not too active

VLA M dwarf Flux SurveyVLA M dwarf Flux Survey 174 X-ray selected 174 X-ray selected

nearby M dwarfsnearby M dwarfs 10 minute VLA 10 minute VLA

observations with 50 observations with 50 microJy rmsmicroJy rms

40 detections of 29 40 detections of 29 starsstars

Rough agreement X-Rough agreement X-ray-radio correlationray-radio correlation

No distinction between No distinction between early and late typesearly and late types

Bower, Bolatto, Ford, Kalas 2009, ApJ, in press

Stars are VariableStars are Variable

EV LacOsten et al 2005

Pilot SurveyPilot Survey

7 stars7 stars 3 epochs3 epochs < 10 days< 10 days

Hipparcos errors ~ Hipparcos errors ~ 1 mas/y1 mas/y

Error over 10 days Error over 10 days < 0.1 mas< 0.1 mas

TestTest DetectabilityDetectability Image stabilityImage stability

8000 km baselines3 cm wavelength1 mas resolutionAstrometry ~ beam/SNR

Results from Pilot Study:Results from Pilot Study:Apparent Motion of GJ 4247Apparent Motion of GJ 4247

23 March 200625 March 200626 March 2006

15 mas

Comparison of radio positions (points) with predictions from Hipparcos astrometry (solid line) reveal noise-limited rms residuals ~0.1 milliarcseconds, approximately 1 stellar diameter.

Bower, Bolatto, Ford, Kalas 2009, ApJ, in press

Pilot Study ResultsPilot Study Results

Residuals are sensitivity limited~0.2 mas

GJ 4247

GJ 896A

GJ 65B

VPAS ResultsVPAS Results

GJGJ DetectionsDetections Proper MotionProper Motion

65B65B 3/33/3 Different from OpticalDifferent from Optical

285285 2/32/3 Optical, sensitivity Optical, sensitivity limitedlimited

896A896A 3/33/3 Optical, sensitivity Optical, sensitivity limitedlimited

42474247 3/33/3 Optical, sensitivity Optical, sensitivity limitedlimited

412B412B 0/30/3 --------------------

803803 1/21/2 --------------------

12241224 0/30/3 --------------------

Results from Pilot Study:Results from Pilot Study:Constraints on Companion Constraints on Companion

MassesMasses Agreement with Agreement with

optical astrometry optical astrometry sets upper limit on sets upper limit on acceleration and acceleration and therefore companion therefore companion massesmasses MMpp < 3 – 10 M < 3 – 10 MJupJup @ 1 @ 1

AUAU Sensitivity is limited Sensitivity is limited

by the short lever arm by the short lever arm of VLBA observations: of VLBA observations: ~10 days~10 days

RIPL will extend this RIPL will extend this lever arm by factor of lever arm by factor of 100100 Semi-major Axis (AU)

Pla

net

Mass

(M

jup)

Bower, Bolatto, Ford, Kalas 2009, ApJ, in press

RIPLRIPLRadio Interferometric Radio Interferometric

Planet SearchPlanet Search 30 stars30 stars 12 epochs/4 years12 epochs/4 years VLBA + GBTVLBA + GBT 512 Mb/s512 Mb/s 2 hours on source + 2 hours on source +

2 hours calibration2 hours calibration 25 microJy rms25 microJy rms

4 x lower than pilot 4 x lower than pilot surveysurvey

1392 hours total1392 hours total

Key question: What is fraction of long-period planets around low mass stars?

RIPL SampleRIPL Sample

30 Stars30 Stars M1 – M8M1 – M8 V = 9.6 – 15.8 magV = 9.6 – 15.8 mag S_6cm = 0.1 – 6 mJyS_6cm = 0.1 – 6 mJy D = 2.7 – 9.5 pcD = 2.7 – 9.5 pc 11 are members of known binary or 11 are members of known binary or

multiple systemsmultiple systems

Simulated RIPL ResultsSimulated RIPL Results

RIPL SensitivityRIPL Sensitivity

Current StatusCurrent Status Observing began Oct Observing began Oct

20072007 Approximately 4 Approximately 4

observations/monthobservations/month Expected completion in Expected completion in

mid-2011mid-2011 40% complete40% complete Pipeline processing Pipeline processing

underway (see poster by underway (see poster by Vince Viscomi)Vince Viscomi)

All stars detectedAll stars detected 60% of stars detected 60% of stars detected

in every epochin every epoch

Benefits of Astrometric Benefits of Astrometric DetectionDetection

Unique methodUnique method Breaks degeneracy of RV searches for mass, Breaks degeneracy of RV searches for mass,

inclination angle, and ascending nodeinclination angle, and ascending node Probes low mass, active stars that are difficult Probes low mass, active stars that are difficult

to study with RV methodto study with RV method Planet fraction of low mass stars poorly Planet fraction of low mass stars poorly

determineddetermined Detects planets that can be studied with Detects planets that can be studied with

extreme AOextreme AO Ties radio and optical astrometric reference Ties radio and optical astrometric reference

frameframe

RV Search ResultsRV Search ResultsFew M dwarf HostsFew M dwarf Hosts

RV Search ResultsRV Search ResultsMost Planets are >10 pc Most Planets are >10 pc

DistantDistant

RV Search ResultsRV Search ResultsWhat is Mplanet/Mstar?What is Mplanet/Mstar?

Microlensing Search Microlensing Search ResultsResults

What is Mplanet/Mstar? What is Mplanet/Mstar?

Microlensing Search Microlensing Search ResultsResults

Planets are Very DistantPlanets are Very Distant

Comparative Sensitivity of Comparative Sensitivity of SearchesSearches

Future Directions for Radio Future Directions for Radio Astrometry & PlanetsAstrometry & Planets

Bandwidth upgrade Bandwidth upgrade for VLBAfor VLBA 512 Mb/s 512 Mb/s 8 Gb/s 8 Gb/s 4 x sensitivity4 x sensitivity Calibrator density Calibrator density

increases by 8 xincreases by 8 x In-beam calibrators In-beam calibrators 10 microarcsec 10 microarcsec

accuracy accuracy Neptune Neptune mass planetsmass planets

Square Kilometer Square Kilometer ArrayArray 100 x sensitivity100 x sensitivity 3000-5000 km baselines3000-5000 km baselines 1 microarcsec accuracy 1 microarcsec accuracy

Earth mass Earth mass sensitivitysensitivity

SummarySummary

Radio astrometry is sensitive to sub-Radio astrometry is sensitive to sub-Jupiter mass planets around M Jupiter mass planets around M dwarfsdwarfs

We can already exclude BD We can already exclude BD companions to three stars based on companions to three stars based on only three measurementsonly three measurements

RIPL survey will probe low mass, RIPL survey will probe low mass, active star parameter spaceactive star parameter space