Summary by M. Rupen.
Chaired by Dale Frail Also present: Tim Bastian, Alan Bridle, Chris Carilli, Vivek Dhawan, Chris Fassnacht, Miller Goss, John Hibbard, Bob Hjellming, Amy Mioduszewski, Frazer Owen, Rick Perley, Michael Rupen, Dick Sramek, one illegible (sorry). Overall: desire for dynamic scheduling, and fast, real-time imaging Also A+, even when the rest of the array is not available: note that A+ with 8GHz/IF is roughly as sensitive as the ENTIRE current VLA 1- The Sun 2- Galactic Novae Follow-up: Bob Hjellming a. Imaging *** * Example: Nova Cyg 1992 - radio shells mapped with MERLIN and VLA, 81-769 days after explosion - masses 3-5 times larger than thermoinuclear WD explosion should give - 30,000 to 40,000 K, but thermal (when tau<1, T~1e4 K) MERLIN showed north-south elongation, whereas VLA source is round; eventually HST kicked in, but by then it only saw 5-10% of the mass --> can get mass and clumpiness fairly directly from radio imaging * What the Expansion Project could do - SENSITIVITY (flux densities are intiailly a few mJy, and Snu goes as t^2 while the source is optically thick, so in a few cases can get 100s of mJy at peak. 43 GHz fluxes can reach the Jy level.) - RESOLUTION (A+) -- ***all the time*** --> could image ALL novae in the entire Galaxy: perhaps 30 per year total, vs. current 6-10 found optically each year which would be suitable (and a few even fainter) (only 2 novae have been imaged so far!) --> early-time geometry progresses from outermost ejection shell inwards through the various layers, until the source is completely optically thin. Optical folks *only* see this latter stage, so they miss all the interesting stuff. Need A+ resolution...which will be there all the time! * vs. recurrent novae, which may have nonthermal emission -- those have not yet been imaged, because the VLA hasn't been in A config. at the right time (RS Oph was caught much later) * Might be able to see RRLs too; velocities are 100-3000km/s, so you need the correlator * "calibrate thermonuclear physics" - geometry - mass -- radio sees too much! - clumpiness b. X-ray binaries See also Galactic and stellar working groups * VLA-VLBA gap leads to missing lots of flux at the VLBA, and boring maps at the VLA * Expansion Project offers - SNAPSHOTS (quick response; good imaging; sensitivity) - A+ always present (good resolution) --> high-quality, high-resolution imaging --> much better light curves --> test ADAFs with "off" sources * Examples (pretty pics): 1655, 1748 - 1655 VLA blobs, VLBA over-resolved - 1748 "laboratory for hot spot interactions and synchrotron jets" 3- Supernovae Follow-up: Dick Sramek a. Early detection --> figure out absorbing process (free-free vs. SSA; if you see high Tb, it's SSA) b. More SNe * Currently about 1/yr of >14th mag. (of which there are ~8/yr) * Could get beyond Virgo * Might detect dust ??? c. Type Ia * So far undetected, though some predict they might be at a low level? - How far out could you see SN87A? d. Misc. * Ties in with X-ray/optical observations e. Expansion Project offers SENSITIVITY, esp. at high frequency 4- GRBs Follow-up: Dale Frail a. Physics of relativistic blast waves: radio contributions ISS+SSA --> size and expansion rate (beaming vs. spherical) reolve with VLBI for z<0.2 blastwave parameters trace full evol'n, for > 1 year, covering all segments of the light-curve b. Nature of progenitors * NS-NS vs. hypernova * subarcsecond positions --> figure out where they live in host galaxies (based on optical follow-up) * Det. optically-obscured GRBs: dusty, or z>5 c. Cosmological tools * high-z population: absorption, RM, etc. to z=6; maybe even lensing??? d. New types of GRBs * SGR, SNe-GRB, classical GRB are all distinguishable at radio wavelengths 5- Surveys for variability Frazer: we have the data already * Looking for ESEs (one per 10^4 or so --> need 4 20cm beams observed for 12hrs each to get one) * stars, lensing, low flux density AGNs, scintillation
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Last modified 08 December 1999