Title Direct detection of Jupiters around nearby solar-like stars Pi K. M. Menten Time 500 hrs 1. Name: Direct detection of Jupiters around nearby solar-like stars Author: K. M. Menten (kmenten@mpifr-bonn.mpg.de) 2. Science goal: Detect Jupiter at the distance of alpha Centauri (D = 1.34 pc) and around start out to 5 pc. Jupiter at alpha Cen's distance would have a 345 GHz flux density of 6 microJy, while alpha Cen A (G2 V) itself is expected to have a flux density of 19 mJy at this frequency. A Jupiter-like planet moving on the same orbit around alpha Cen A as the real Jupiter around the Sun would, at maximum elongation, appear at a projected distance of 3.9" from alpha Cen A. Using ALMA, this planet could be detected at the 4 sigma level in ~250 hours. The dynamic range of ~10000 (i.e. maximum signal over rms noise) necessary for this observation should be easily reachable, given that self-calibration can be employed using alpha Cen A as a reference. Self calibration will be possible as long as the reference star is detected on each baseline at a few, say 3, sigma within a coherence time, t_coh. If we assume t_coh = 20 sec, we find an SNR of 3 for a single baseline, making self-calibation on alpha Cen A easily feasible. Significantly longer coherence times might be expected, allowing self-calibration for stars at greater distances. Once coherence is achieved with self calibration, long integrations are possible; e.g. 3500 hours of observing time would be required for a 5 sigma$ detection of "Jupiter" at D = 5 pc. Other possible target stars observable with ALMA within or around that distance include tau Cet, Sirius, Procyon, Altair, and sigma Pav. 3. Number of sources: 6 4. Coordinates: 4.1. Solar-like stars within 5 pc: tau Cet (G8 VI, D = 3.6 pc) 01 44 04.08 -15 56 14.9 Sirius (A1 V, D = 2.7 pc) 06 45 08.92 -16 42 58.0 Procyon (F5 V, D = 3.5 pc) 07 39 18.12 +05 13 30.0 alpha Cen (G2 V, D=1.34 pc) 14 39 36.20 -60 50 08.2 Altair (A7 V, D = 5.1 pc) 19 50 47.00 +08 52 06.0 sigma Pav (G6 V, D = 5.7 pc) 20 49 18.17 -68 46 35.5 (All coordinates are J2000) 4.2. Moving target: no 4.3. Time critical: no 5. Spatial scales: 5.1. Angular resolution: 0.1" 5.2. Range of spatial scales/FOV: point source(s) spread over a few arcseconds. 5.3 required pointing accuracy: 6 Observational Setup 6.1 Single dish total power data: no 6.2 stand-alone ACA: no 6.3 Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: no 6.4. Subarrays of 12m baseline-ALMA antennas: no 7. Frequencies: 7.1. Receiver band: Band 7 7.2. Line: none 7.3. Spectral resolution (km/s): N/A 7.4. Spectral coverage (km/s or GHz): N/A 8. Continuum flux density: 8.1. Typical value: a few microJy (planets) 5 - 20 mJy (host stars) 8.2. Required continuum rms: 0.1 microJy 8.3. Dynamic range in image: 10000 8.4. Calibration requirements: absolute 10% repeatability 10% relative 10% 9. Line intensity: 9.1. Typical value: none 9.2. Required rms per channel: N/A 9.3. Spectral dynamic range: N/A 10. Polarization: no 11. Integration time per setting: 250 - 3500 h 12. Total integration time for program: ~10000 hr => reduce to 500 hr 13. Comments on observing strategy ************************************************************************** Review Leonardo Testi: The proposal is challenging but sound. It may be unfeasible to do ALL this programme in the three years covered by the DRSP. One could reasonably consider to do 2 of the closest targets in the 3yrs timeframe, corresponding to approx 1000hrs. Or even limit at the proof of concept on alpha Centauri with 250hrs. Reply Butler: I think this program might be done in the later days of ALMA but i think it has no place in the DRSP. As far as i know, there has never been a claimed detection of an EGP around any of these stars. eps eri is the closest that i know of, and that one is hotly disputed. to propose to use 10000 hours is, well, i think an extreme overcommitment of time. i had suggested that you scrap this entry altogether previously, and i still think this is what should be done. given 2500 hours for all of the proposals in this entire theme, i would not suggest even using 500 for this type of proposal. Comment Mark Gurwell: We (should? could?) include comments that observations of Jupiter and Saturn in our solar system show incredibly deep and broad absorption due to PH3 at 267 GHz (see for example section 4.1.5). In a selected case of a few very nearby objects (1.3 to maybe 3 pc), focused observations of a few hundred to few thousand hours could in fact detect such absorption from a Jupiter or maybe even a Saturn (its not the mass that matters as much as the stellar-planet distance)...with enough integration the line shape could be roughly determined and give some information on the temperature structure of the atmosphere. Comment Ewine: There will undoubtedly be proposal pressure to observe exo-planets with ALMA and it is likely at least some of them will be approved by the TAC. Therefore, 500 hrs has been reserved for this theme (one several M_J exo-planet) and the total time for this theme has been increased. -------------------------------------------------- Review v2.0: Review of 4.4.1-4.4.3 No updated required w.r.t. DRSP 1.1. Integration times still formally hold for 64 antennas, so either increase the total times by 30% or reduce the sensitivity by 14%. Other, unknown factors in the sensitivity and performance will be larger than this correction. R.: This program is not jeopardized by the reduction of the number of antennae. Target list can be adjusted. The key point of this astrometric programm is the performance of ALMA in the extended configuration to benefit of the highest angular resolution of the instrument.