Title Magnetic Energy Release and High-Energy Particles in Stellar Atmospheres Pi M. Guedel Time 14 hrs 1. Name of program and authors Magnetic Energy Release and High-Energy Particles in Stellar Atmospheres Authors Manuel Guedel 2. Science goal(s) Millimetric flares have been observed on the Sun, with characteristics that do not reproduce flare emission at lower, centimetric wavelengths. The radiation is due to the gyrosynchrotron process and requires very high-energy electrons (MeV and higher). The suspicion therefore is that millimetric flares correspond to flares producing gamma-ray events from precipitating electrons and ions. However, all impulsive flares may accelerate electrons to the required MeV energies. We know from solar physics that the electron population responsible for mm bursts is most likely distinct from the electrons producing centimetric and hard X-ray flares. There is presently no hope to see gamma-ray flares from magnetically active stars, and even lower-energetic hard X-ray bursts will be extremely challenging for the INTEGRAL satellite. Short wavelength radio waves are an ideal proxy of particle acceleration to extreme energies. Magnetically active stars have shown bursts at radio wavelengths (as well as in X-rays) up to many orders of magnitude more luminous than solar flares. A T Tau star in the Orion complex (450 pc) was recently reported to flare up to 40 mJy at 86 GHz, for a duration of several days (Furuya et al., PASJ, in press). Some of the magnetospheres producing them or trapping the particles have been resolved by VLBI techniques, reaching sizes several times the stellar diameter. This project will test acceleration physics in extremely active stars that may accelerate particles for much longer periods and to much higher energies. 3. Number of sources: ~ 5-10 extremely active nearby single stars and Algol/RS CVn binaries ~ 5-10 extremely active young sources in star forming regions (150 pc for Taurus, 450 pc for Orion) 4. Coordinates: spread over the sky 4.2. Moving target: yes/no (e.g. comet, planet, ...) no 4.3. Time critical: yes/no (e.g. SN, GRB, ...) yes: should be coordinated with lower-frequency radio telescopes, and if possible with X-ray satellite observatories 5. Spatial scales: 5.1. Angular resolution (arcsec): point 5.2. Range of spatial scales/FOV (arcsec): (optional: indicate whether single-field, small mosaic, wide-field mosaic...) typically point surces (wide-field mosaic advantageous for crowded star-forming regions (SFR) 5.3. Single dish total power data: yes/no no 5.4. ACA: yes/no no 5.5. Subarrays: yes/no no 6. Frequencies: 6.1. Receiver band: Band 3, 6, 7, or 9 continuum <250 GHz 6.2. Lines and Frequencies (GHz): (approximate; do NOT go into detail of correlator set-up but indicate whether multi-line or single line; apply redshift correction yourself; for multi-line observations in a single band requiring different frequency settings, indicate e.g. "3 frequency settings in Band 7" without specifying each frequency (or give dummies: 340., 350., 360. GHz). For projects of high-z sources with a range of redshifts, specify e.g. "6 frequency settings in Band 3". Apply redshift correction yourself) (continuum) 6.3. Spectral resolution (km/s): N/A 6.4. Bandwidth or spectral coverage (km/s or GHz): 7. Continuum flux density: 7.1. Typical value (Jy): (take average value of set of objects) (optional: provide range of fluxes for set of objects) up to tens of mJy, in extreme cases up to a few 100 mJy 100 GHz (for nearby active stars, e.g. RS CVn binaries, and for T Tau stars in SFRs) 7.2. Required continuum rms (Jy or K): 0.1 mJy 7.3. Dynamic range within image: (from 7.1 and 7.2, but also indicate whether e.g. weak objects next to bright objects) 10 - 1000 (not important - variable sources) 8. Line intensity: 8.1. Typical value (K or Jy): (take average value of set of objects) (optional: provide range of values for set of objects) N/A 8.2. Required rms per channel (K or Jy): N/A 8.3. Spectral dynamic range: N/A 9. Polarization: yes/no (optional) 9.1. Required Stokes I, V 9.2. Total polarized flux density (Jy) unknown but intermediate (few 10 of %) at best 9.3. Required polarization rms and/or dynamic range 5% 9.4. Polarization fidelity 10. Integration time for each observing mode/receiver setting (hr): 10 nearby single objects: 20 snapshots @ 2 minutes each, spread over 1-2 days => 7 hrs 10 SFR fields: 20 snapshots @ 2 minutes each, spread over 1-5 days => 7 hrs (Alternatives possible - shorter snaphshot integration but more snapshots) 11. Total integration time for program (hr): 14 hr 12. Comments on observing strategy (e.g. line surveys, Target of Opportunity, Sun, ...): (optional) Should be coordinated with lower-frequency radio observations to measure spectral shape. ************************************************************************** Review Leonardo Testi: As 3.2.1, with the addition of a mysterious sentence about the requirement of an rms below 250 GHz of 0.1 mJy in one hour (?? if the goal was continuum it should be easy to go at least a factor of 10 below this number in one hour, maybe is more complicated than I think? Is the goal to obtain line observations?) Assuming as above (rms~0.01 mJy continuum full pol at 100 GHz): total time is 10 hrs total for 10 objects. Comment Ewine: assume 10 hr for program Reply Guedel: The integration times changed a little bit but are better justified. For the flare program, things are very uncertain. The more time the better, but it should come in snapshots spread over several days, so it is difficult to give a well justified number for the integration time, but I've put in a reasonable amount, I think. I've added YSOs to that program since they seem to flare in mm (recent paper on Orion). The emission is all continuum. Comment Ewine: new DRSP is baseline -------------------------------------------------- Review v2.0: 1. Name of program and authors Magnetic Energy Release and High-Energy Particles in Stellar Atmospheres Authors Manuel Guedel DRSP2.0 Review Leonardo Testi: Is this single frequency or (nearly simultaneous) multifrequency (which frequencies)? Answer: (Near-simultaneous) mutifrequency observations required to derive spectral indices and thus to characterize synchrotron spectra. Ideally, at least three frequencies should be included. It is difficult to predict which frequencies are optimum. Should try various combinations.