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Walter Gonzalez, Francisco Jablonski, Felipe Madsen and Eder Martioli

Search for radio emission in extrasolar planets detected by COROT Accepted AP observational requirements, feasability, expectations. Walter Gonzalez, Francisco Jablonski, Felipe Madsen and Eder Martioli Instituto Nacional de Pesquisas Espaciais São José dos Campos, SP - Brazil. Introduction.

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Walter Gonzalez, Francisco Jablonski, Felipe Madsen and Eder Martioli

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  1. Search for radio emission in extrasolar planets detected by COROTAccepted APobservational requirements, feasability, expectations Walter Gonzalez, Francisco Jablonski, Felipe Madsen and Eder Martioli Instituto Nacional de Pesquisas Espaciais São José dos Campos, SP - Brazil

  2. Introduction • Jupiter shows non-thermal emission in the kHz to GHz frequency range (e.g., Carr et al. 1983) • Below 40 MHz  cyclotron emission • Higher frequencies  synchrotron emission • Average power radiated is above the Giga-Watt level • Predictions for the power emitted by extrasolar planets in Bastian et al. (2000) and Zarka et al. (2001)

  3. The star-planet connection • Many planets very close (<< 1 AU) to their primaries • Magnetic / tidal interaction • Energy input into the planet's magnetosphere orders of magnitude larger than in Jupiter • Mass > MJup B > BJup • Power emitted likely to be much stronger than in Jupiter (Farrel et al. 2003)

  4. Radio-optical connection • In Jupiter, radio emission is enhanced by orders of magnitude after Coronal Mass Ejection (CME) events in the Sun • CME events produce global intensity variations in the Sun with fractional r.m.s ~10-4 • CME events can be detected in COROT photometry! • ~Real-time monitoring with COROT could be useful to early warn radio campaigns to observe enhanced Jupiter-like emission • Alternatively, off-line analysis of simultaneous radio and optical observations likely to show time-correlated events

  5. Possible observational scenario • A planet is found in the sismo field • Unlikely, but very good, since objects tend to be close to us • New planets are found among the brightest targets in the exo field • Large number, but at relatively larger distances • COROT observes a star already known to bear a planet • Very good (eg. HD46375)

  6. Impulsive event detection • Bayesian approach suitable, like in Aigrain and Favata (2002) and Defaÿ et al. (2001) • Photon (Poisson) noise + RON • Two-rate (1, 2) model for flares, similar to the method of Gregory and Loredo (1992), for m=2 • 2 > 1 included as prior information • Model comparison to select best time-window • Segment analysis to set up baseline of "zero activity" • More elaborate models should include information available on the shape of events

  7. Observational requirements • Light curves of stars showing planet transits • Interesting stuff not transits themselves, but impulsive events signaling CME • The brighter (closer) the stars, the better • Close to real-time access to data (say, in ~24 h) would be great since it could be used to trigger radio observations • Offline analysis of simultaneous COROT and radio data ok too

  8. Feasability • Scaling laws predict that among the known exoplanets, 18 should deliver more than 10 mJy at f<100 Mhz • GMRT observations carried out in March 2005 • 55 Cnc, 70 Vir, upsilon And, tau Boo • No radio emission detected • Sensitivity (2 s) of 3 mJy at 150 Mhz, 1 h exp. time • Simultaneous optical observations at LNA, Brazil • Bad weather, but some results • Difficult observations

  9. Expectations • Expectation from a scientific point of view is of a fundamental contribution to magnetospheric studies, for the first time gathering data in environment quite different from that in the solar system. • Increasing levels of scientific cooperation among groups at INPE and abroad • Attracting more people to exoplanetary research

  10. Resources • Quite good computing infrastructure, including access to the supercomputer used by INPE for weather forecasting • Experience with GMRT data acquisition and reduction • Experience with time-series analysis

  11. Summary The sensitivity level of existing meter-wavelength radiotelescopes (better than 10 mJy in the region 10-100 MHz) is such that nonthermal emission from extrasolar planets could be detected with integration times less than one hour. With LOFAR this limit will be at least a factor of ten better. This means that a large number of transit-discovered planets in COROT fields could be monitored for impulsive events that lead enhanced radio- emission.

  12. References Aigrain, S., and Favata, F. 2002, A&A, 395, 625 Bastian, T., Dulk, G.A., and Leblanc, Y. 2000, ApJ, 545, 1058 Carr, T.D., M.D. Desch, and J. K. Alexander, Phenomenology of magnetospheric radio emissions, in Physics of the Jovian Magnetosphere, edited by A.J. Dessler, Chapter 7, pp. 226-284, Cambridge University Press, New York, 1983. Defaÿ, C., Deleuil, M., and Barge, P. 2001, A&A, 365, 330 Farrel, W.M., Desch, M.D., Lazio, T.J., Bastian, T. and Zarka, P. 2003, ASP Conf. Ser. 294: Scientific Frontiers in Research on Extrasolar Planets, ed. D. Deming and S. Seager (San Francisco: ASP), 151 Gregory, P.C., and Loredo, T.J. 1992, ApJ, 398, 146 Zarka, P. Treumann, R.A., Ryabov, B.P. and Ryabov, V.B. 2001, Ap&SS, 277, 293

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