1. RIPL Radio Interferometric Planet Search Geoffrey Bower UC Berkeley Collaborators: Alberto Bolatto (UMD), Eric Ford (UFL), Paul Kalas, Adam Fries, Anna Treaster, Vince Viscomi (UCB)

2. Exploding the Transient Radio Sky

3. MM Wavelength T Tauri Outburst in Orion 2 nd most luminous stellar radio outburst 2 nd most luminous stellar radio outburst Briefly, brightest object in nebula Briefly, brightest object in nebula Required long baselines for detection Required long baselines for detection Magnetized T Tauri outburst Magnetized T Tauri outburst Contemporaneous with X-ray outburst Contemporaneous with X-ray outburst Many such objects likely to be found by CARMA & ALMA Many such objects likely to be found by CARMA & ALMA BIMA A configuration images (Bower, Plambeck, Bolatto, Graham, de Pater, McCrady, Baganoff 2004)

4. 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

5. Implications of Orion Parallax Factor of 4 improvement over previous parallax measurement Factor of 4 improvement over previous parallax measurement 480 +/- 80 pc (Genzel et al 1981) 480 +/- 80 pc (Genzel et al 1981) Lower distance reduces stellar luminosities by 40% Lower distance reduces stellar luminosities by 40% Resolves problem of overluminous massive stars Resolves problem of overluminous massive stars Indicates greater age spread of pre-main sequence stars  process of continuous star formation rather than single episode Indicates greater age spread of pre-main sequence stars  process of continuous star formation rather than single episode HST Image of Orion Nebula

6. Taurus Cluster Distance D=141.5 +2.7 -2.8 pc Loinard et al 2005

7. Planets are Easy to Detect

8. Companion to GJ 752B Detected w/Optical Astrometry Pravdo & Shaklan 2009 Not Confirmed by Radial Velocities

9. White et al

10. Stars are Variable EV Lac Osten et al 2005

11. Brown Dwarfs are Radio Sources Berger et al 2001 Hallinan et al 2007

12. Gudel 2002

13. Requirements of a Planet Survey Low mass, nearby star Low mass, nearby star Astrometric displacement ~ 1 mas Astrometric displacement ~ 1 mas Nonthermal radio emission Nonthermal radio emission S ~ 1 mJy S ~ 1 mJy F ~ GHz F ~ GHz Positional stability < 0.1 mas Positional stability < 0.1 mas Stable Image Stable Image Active, but not too active Active, but not too active

14. VLA M dwarf Flux Survey 174 X-ray selected nearby M dwarfs 174 X-ray selected nearby M dwarfs 10 minute VLA observations with 50 microJy rms 10 minute VLA observations with 50 microJy rms 40 detections of 29 stars 40 detections of 29 stars Rough agreement X-ray- radio correlation Rough agreement X-ray- radio correlation No distinction between early and late types No distinction between early and late types Bower, Bolatto, Ford, Kalas 2009, ApJ, in press

15. Pilot Survey 7 stars 7 stars 3 epochs 3 epochs < 10 days < 10 days Hipparcos errors ~ 1 mas/y Hipparcos errors ~ 1 mas/y Error over 10 days < 0.1 mas Error over 10 days < 0.1 mas Test Test Detectability Detectability Image stability Image stability 8000 km baselines 3 cm wavelength 1 mas resolution Astrometry ~ beam/SNR

16. VPAS Astrometry Primary calibrator Secondary calibrator Secondary calibrator ~1 degree 5 Minute switching time

17. Results from Pilot Study: Apparent 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

18. Pilot Study Results Residuals are sensitivity limited ~0.2 mas GJ 4247 GJ 896A GJ 65B

19. VPAS Results GJDetections Proper Motion 65B3/3 Different from Optical 2852/3 Optical, sensitivity limited 896A3/3 42473/3 412B0/3---------- 8031/2---------- 12240/3----------

20. Results from Pilot Study: Constraints on Companion Masses Agreement with optical astrometry sets upper limit on acceleration and therefore companion masses Agreement with optical astrometry sets upper limit on acceleration and therefore companion masses M p < 3 – 10 M Jup @ 1 AU M p < 3 – 10 M Jup @ 1 AU Sensitivity is limited by the short lever arm of VLBA observations: ~10 days Sensitivity is limited by the short lever arm of VLBA observations: ~10 days RIPL will extend this lever arm by factor of 100 RIPL will extend this lever arm by factor of 100 Semi-major Axis (AU) Planet Mass (M jup ) Bower, Bolatto, Ford, Kalas 2009, ApJ

21. RIPL Radio Interferometric Planet Search 30 stars 30 stars 12 epochs/4 years 12 epochs/4 years VLBA + GBT VLBA + GBT 512 Mb/s 512 Mb/s 2 hours on source + 2 hours calibration 2 hours on source + 2 hours calibration 25 microJy rms 25 microJy rms 4 x lower than pilot survey 4 x lower than pilot survey 1392 hours total 1392 hours total Key question: What is fraction of long-period planets around low mass stars?

22. RIPL Sample 30 Stars 30 Stars M1 – M8 M1 – M8 V = 9.6 – 15.8 mag V = 9.6 – 15.8 mag S_6cm = 0.1 – 6 mJy S_6cm = 0.1 – 6 mJy D = 2.7 – 9.5 pc D = 2.7 – 9.5 pc 11 are members of known binary or multiple systems 11 are members of known binary or multiple systems

23. Simulated RIPL Results

24. RIPL Sensitivity

25. Current Status Observing began Oct 2007 Observing began Oct 2007 Approximately 4 observations/month Approximately 4 observations/month Expected completion in mid-2011 Expected completion in mid-2011 67% complete 67% complete Pipeline processing in place Pipeline processing in place All stars detected All stars detected 60% of stars detected in every epoch 60% of stars detected in every epoch Astrometric Analysis of Individual Stars Underway Astrometric Analysis of Individual Stars Underway Detections versus Flux Density

26. Benefits of Astrometric Detection Unique method Unique method Breaks degeneracy of RV searches for mass, inclination angle, and ascending node 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 Probes low mass, active stars that are difficult to study with RV method Planet fraction of low mass stars poorly determined Planet fraction of low mass stars poorly determined Detects planets that can be studied with extreme AO Detects planets that can be studied with extreme AO Ties radio and optical astrometric reference frame Ties radio and optical astrometric reference frame

27. RV Search Results Few M dwarf Hosts

28. RV Search Results Most Planets are >10 pc Distant

29. RV Search Results What is Mplanet/Mstar?

30. Microlensing Search Results What is Mplanet/Mstar?

31. Microlensing Search Results Planets are Very Distant

32. Results of Recent RV Searches Detection of long- period, eccentric planet around M dwarf Detection of long- period, eccentric planet around M dwarf Johnson et al 2007 Johnson et al 2007 Rates suggest that planet mass tracks stellar mass Rates suggest that planet mass tracks stellar mass

33. Comparative Sensitivity of Searches

34. Future Directions for Radio Astrometry & Planets Bandwidth upgrade for VLBA Bandwidth upgrade for VLBA 512 Mb/s  8 Gb/s 512 Mb/s  8 Gb/s  4 x sensitivity  4 x sensitivity  Calibrator density increases by 8 x  Calibrator density increases by 8 x  In-beam calibrators  In-beam calibrators  10 microarcsec accuracy  Neptune mass planets  10 microarcsec accuracy  Neptune mass planets Square Kilometer Array Square Kilometer Array 100 x sensitivity 100 x sensitivity 3000-5000 km baselines 3000-5000 km baselines 1 microarcsec accuracy  Earth mass sensitivity 1 microarcsec accuracy  Earth mass sensitivity

35. Arecibo 12m Upgrade Increase in sensitivity for stars: GB-AR baseline @ 1 Gbps Increase in sensitivity for stars: GB-AR baseline @ 1 Gbps In 1 min: 80 uJy In 1 min: 80 uJy Detect brightest stars instantaneously Detect brightest stars instantaneously Short timescale stellar activity Short timescale stellar activity In 2 hours: 7 uJy In 2 hours: 7 uJy Factor of ~4 improvement over RIPL Factor of ~4 improvement over RIPL Higher SNR, more reliable detections for current stars Higher SNR, more reliable detections for current stars Sub 0.1 mas accuracy for brightest stars Sub 0.1 mas accuracy for brightest stars Increase number of accessible stars by ~10 [within AR FoV --- factor of 2 total] Increase number of accessible stars by ~10 [within AR FoV --- factor of 2 total] Need EVLA survey to identify these stars Need EVLA survey to identify these stars Tradeoffs/Issues Tradeoffs/Issues Reduced sensitivity for phase reference calibrator Reduced sensitivity for phase reference calibrator GB-12m = 1/7 GB-VLBA GB-12m = 1/7 GB-VLBA Requires more distant calibrator (or less SNR) Requires more distant calibrator (or less SNR) Increased systematic astrometric error Increased systematic astrometric error Benefit is primarily towards fainter stars Benefit is primarily towards fainter stars Total bandwidth available? Total bandwidth available? Sensitivity dominated by 1 N-S baseline Sensitivity dominated by 1 N-S baseline 2-D Imaging/Modeling Quality 2-D Imaging/Modeling Quality Until EVLA VLBI Until EVLA VLBI

36. Summary Radio astrometry is sensitive to sub-Jupiter mass planets around M dwarfs 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 We can already exclude BD companions to three stars based on only three measurements RIPL survey will probe low mass, active star parameter space RIPL survey will probe low mass, active star parameter space AR 12m upgrade can provide improved accuracy and larger number of stars AR 12m upgrade can provide improved accuracy and larger number of stars