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RIPL Radio Interferometric Planet Search Geoffrey Bower UC Berkeley Collaborators: Alberto Bolatto (UMD), Eric Ford (UFL), Paul Kalas, Anna Treaster, Vince Viscomi (UCB) MM Wavelength T Tauri Outburst in Orion 2nd most luminous stellar radio outburst Briefly, brightest object in nebula Required long baselines for detection Magnetized T Tauri outburst Contemporaneous with X-ray outburst Many such objects likely to be found by CARMA & ALMA BIMA A configuration images (Bower, Plambeck, Bolatto, Graham, de Pater, McCrady, Baganoff 2004) Orion Nebula Parallax w/Star GMR-A D=389 pc +/- 5% <0.1 mas/epoch Sandstrom, Peek, Bower, Bolatto, Plambeck 2007 Astro-ph/0706.2361 Planets are Easy to Detect Companion to GJ 752B Detected w/Optical Astrometry Pravdo & Shaklan 2009 White et al Gudel 2002 Requirements of a Planet Survey Low mass, nearby star Astrometric displacement ~ 1 mas Nonthermal radio emission S ~ 1 mJy F ~ GHz Positional stability < 0.1 mas Stable Image Active, but not too active VLA M dwarf Flux Survey 174 X-ray selected nearby M dwarfs 10 minute VLA observations with 50 microJy rms 40 detections of 29 stars Rough agreement X-rayradio correlation No distinction between early and late types Bower, Bolatto, Ford, Kalas 2009, ApJ, in press Stars are Variable EV Lac Osten et al 2005 Pilot Survey 7 stars 3 epochs < 10 days Hipparcos errors ~ 1 mas/y Error over 10 days < 0.1 mas Test Detectability Image stability 8000 km baselines 3 cm wavelength 1 mas resolution Astrometry ~ beam/SNR Results from Pilot Study: Apparent Motion of GJ 4247 15 mas 26 March 2006 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 25 March 2006 23 March 2006 Pilot Study Results GJ 4247 GJ 896A GJ 65B Residuals are sensitivity limited ~0.2 mas VPAS Results GJ Detections Proper Motion 65B 285 896A 4247 412B 803 1224 3/3 2/3 3/3 3/3 0/3 1/2 0/3 Different from Optical Optical, sensitivity limited Optical, sensitivity limited Optical, sensitivity limited ---------------------------- Agreement with optical astrometry sets upper limit on acceleration and therefore companion masses Mp < 3 – 10 MJup @ 1 AU Sensitivity is limited by the short lever arm of VLBA observations: ~10 days RIPL will extend this lever arm by factor of 100 Planet Mass (Mjup) Results from Pilot Study: Constraints on Companion Masses Semi-major Axis (AU) Bower, Bolatto, Ford, Kalas 2009, ApJ, in press RIPL Radio Interferometric Planet Search 30 stars 12 epochs/4 years VLBA + GBT 512 Mb/s 2 hours on source + 2 hours calibration 25 microJy rms 4 x lower than pilot survey 1392 hours total Key question: What is fraction of long-period planets around low mass stars? RIPL Sample 30 Stars M1 – M8 V = 9.6 – 15.8 mag S_6cm = 0.1 – 6 mJy D = 2.7 – 9.5 pc 11 are members of known binary or multiple systems Simulated RIPL Results RIPL Sensitivity Current Status Observing began Oct 2007 Approximately 4 observations/month Expected completion in mid-2011 40% complete Pipeline processing underway (see poster by Vince Viscomi) All stars detected 60% of stars detected in every epoch Benefits of Astrometric Detection Unique method Breaks degeneracy of RV searches for mass, inclination angle, and ascending node Probes low mass, active stars that are difficult to study with RV method Planet fraction of low mass stars poorly determined Detects planets that can be studied with extreme AO Ties radio and optical astrometric reference frame RV Search Results Few M dwarf Hosts RV Search Results Most Planets are >10 pc Distant RV Search Results What is Mplanet/Mstar? Microlensing Search Results What is Mplanet/Mstar? Microlensing Search Results Planets are Very Distant Comparative Sensitivity of Searches Future Directions for Radio Astrometry & Planets Bandwidth upgrade for VLBA 512 Mb/s 8 Gb/s 4 x sensitivity Calibrator density increases by 8 x In-beam calibrators 10 microarcsec accuracy Neptune mass planets Square Kilometer Array 100 x sensitivity 3000-5000 km baselines 1 microarcsec accuracy Earth mass sensitivity Summary Radio astrometry is sensitive to sub-Jupiter mass planets around M dwarfs We can already exclude BD companions to three stars based on only three measurements RIPL survey will probe low mass, active star parameter space