1. Extra-Solar Planets: Detection Schemes Using Optical and Radio Techniques Extra-Solar Planets: Detection Schemes Using Optical and Radio Techniques R.L. Mutel University of Iowa

2. Overview Map of ESP Detection Schemes

3. First Extra-solar Planet Detection 3 (or 4) planets surrounding pulsar PSR1257+12 ( Wolszczan, A. & Frail, D., 1992, Nature ) Pulsar 1257+12 Period 6.2 msec Mass 0.29 Msun Distance 800 pc. Name M/M Earth )P(days)A(AU) A0.01525.30.19 B3.466.50.36 C2.998.20.47 D95M jup 170yr 35 N.B. Planets probably could not have survived SN explosion, were likely formed from SN debris!

4. Second Planet Detection: 51 Peg (M.Mayor & D.Queloz, 1995, Nature) P (days) eccVel K (m/s) Msini (Mjup) a (AU) 4.2310.0155.450.460.05 Stellar Characteristics Sp. TypeMass (Msun) Vel K (km/s) D (pc) P (day) [Fe/H ] G5V1.0654.515.3628.000.20 Planet Characteristics N.B. Tsurface ~ 1000K for this planet!

5. As of mid-2002, there were over 100 extra- solar planets detected, most by spectroscopic technique. Except for PSR1257, all are massive planets (0.2Mjup < 10 Mjup) Most are much closer than expected to parent star and/or more massive N.B. Terrestrial planets would be found here

7. Detection of Extra-Solar Planets: Doppler Effect HD89744 (F7V) P 256 days Mass 7M J HD89744 (F7V) P 256 days Mass 7M J

8. Spectroscopic Technique Star-planet system moves mutually around common barycenter, so solving 2- body problem we have: Solving for the planet mass: Note: Derived mass is always less than true mass [by 1/sin(i)] 2K

9. Most ESP’s detected with spectroscopy have large masses and small semi-major axes: Why?

10. Mostly a selection effect? Current spectroscopy detection schemes have limiting velocity resolution (σ ~ 10 m/s) Future space missions (Kepler, FAME, SIM) will probe much larger areas of M-a diagram Current limit (σ  1 0 ms/)

11. Detection of Extra-Solar Planets: Occultations

12. Detection of Extra- Solar Planets by Occultation: HD 209458 (V = 7.6) First detection by Henry et al. 2001 (0.8 m, Fairborn Observatory, Tennessee State Univ.)  V = 0.017 (1. 58%) STARE Light Curve Transit observed 26-27 July 2000 by Deeg and Garrido at the 0.9m Sierra Nevada Telescope

13. Detection of Extra-Solar Planets: STARE Telescope (currently in Canary Islands) The current STARE telescope, as of July, 1999, is a field-flattened Schmidt working aperture of 4 in, (f/2.9). The telescope is coupled to a Pixelvision 2K x 2K CCD (Charge-Coupled Device) camera to obtain images with a scale of 10.8 arcseconds per pixel over a field of view 6.1 degrees square. Broad-band color filters (B, V, and R) that approximate the Johnson bands are slid between the telescope and camera. By taking exposures with different colored filters, the colors of stars in the field can be determined. This is necessary for accurate photometry.

14. Transit Photometry Technique parameters (assumes R s >> R p ) Transit duration Transit depth Probability of occultation Object  (hr) (  I/I) P (%) Mercury7.110 -5 10 -4 Earth1310 -4 2·10 -5 Jupiter300.0110 -6 HD209458 (a=0.045) 2.80.0150.01

15. Detection of ESP companion to White Dwarfs Using Occultations ( Mike Wilson M.S. 2003) Planets around white dwarfs have much higher probability of occultation (2% at 50 R J ) White Dwarf Jovian Planet Eclipse is total, not photometrically difficult (< 1%) Eclipse duration much shorter (8 min at 25 R J = 4 R roche )

16. But can planets survive red giant phase? Drag force acts to reduce V, hence planet spirals inward. Use RG models to estimate ρ(r), integrate equation of motion Interaction with RG envelope When planet is inside RG, drag force is: Use RG models to estimate ρ(r) and solve equation of motion numerically

17. Sample Calculations (Earth, 1.1 Solar Mass RG) Mass intercepted (kg/sec) vs. normalized radius Normalized radius vs time (yrs)

18. Detection by Direct Imaging Imaging of Gliese 229 with Companion Brown dwarf No planets so far, but HST has imaged a brown dwarf: M = 6 - 20 RJup R ~ 1 RJup a = 44 AU

19. SIM (Space Interferometry Mission: Space-based Interferometer with 1 μas Precision (launch 2009) SIM Instrument and Mission Parameters Baseline10 m Wavelength range0.4 - 0.9µm; Telescope Aperture0.3 m diameter Astrometric Field of Regard 15° diameter Astrometric Narrow Angle Field of View 1° diameter DetectorSi CCD OrbitEarth-trailing solar orbit Science Mission Duration5 years (launch in 2009) Wide Angle Astrometry4 µas mission accuracy Narrow Angle Astrometry 1 µas single measurement accuracy Limiting Magnitude 20 mag

20. SIM Discovery Space

21. Detection by Low-frequency Radio Emission All Solar-system planets with significant magnetospheres emit non- thermal ‘auroral’ radio emission (probably via electron-cyclotron maser mechanism) Radio luminosity scales with solar wind flow pressure or energy flux on the magnetosphere cross-section (Zarka et al. 2001)

22. Radio emission from Planets is strongest at low frequencies (f <100 MHz) Very few large radiotelescopes operate at low frequencies Future arrays includes LOFAR and SKA

23. Sample dynamic spectra from Earth and Jupiter

24. Estimating Radio Power for ESP’s Power dissipated in the interaction of a magnetized flow with an conducting planet with radius R p and speed V: Radio power emitted (scaling by solar system objects) is: Scaling of magnetic flux with stellar distance (at close distances, radial component dominates): Hence, radio power scales as:

25. LOFAR: Low Frequency Array Projected Timeline: Preliminary Design Review ~ end 2002 Site selection ~ end 2002 Critical Design Review ~ early 2004 Initial operations - 2006 Full operations - 2008 The image above is an artist’s conception of one LOFAR station, made up of more than 100 dual-polarization antenna systems. LOFAR will consist of ~100 such stations covering an area ~400 km in diameter at a site yet to be chosen

26. Can ESP’s be detected with LOFAR? LOFAR sensitivity (5σ) below 100 MHz ~ 1 mJy (5 MHz, 1 hr) Jupiter as Pr ~ 10 6 W at 20 MHz, scales to 0.4 mJy at 1 pc., 4 μJy at 10 pc. but burst timescale is seconds. Hence, too faint. But, if scaling with stellar wind power is correct, Jupiter at 0.1pc would be 625x stronger (250 mJy). This would be an easy detection with LOFAR. But, preliminary VLA searches at 74 MHz (Bastian, et al. 2000, 2002) on several stars (47 UMa, d = 14 pc, 2 Jovians at 2,3 AU; 70 Vir, d = 18 pc, one Jovian 0.5 AU) found no detections (typical limit 40 mJy).