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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