Title  ToO Observing of GRB Afterglows
Pi     S. Van Dyk
Time   30 hrs
1. Name: ToO Observing of GRB Afterglows -- Schuyler Van Dyk, Kurt Weiler et al.
        
2. One short paragraph with science goal(s)

Gamma ray bursts (GRBs) are among the most energetic events in the
Universe. Their origins are still unknown.  The radio emission from GRB
afterglows will provide insight into the physical processes associated
with the burst and its immediate circumburst environment.  If some
(long-duration) GRBs are actually associated with hypernovae (extremely
energetic supernovae), then we expect that their properties may be
similar to those of the most luminous radio supernovae (RSN); this was
particularly true for the nearby SN 1998bw/GRB 980425 and the more
distant SN 2003dh/GRB 030329. As such, the justification for detecting
and monitoring GRBs early in their radio evolution, particularly in the
mm and submm, follow similar lines to that for studying RSNe.  The rapid
rise to maximum in the ALMA bands will provide valuable information on
both the emission and absorption processes for GRBs, which further
provides vital insight into the nature of the objects giving rise to the
burst.  Analogs of SN 1998bw can be detected and followed out to 100's
of Mpc.

3. Number of sources

The SWIFT mission (launch in December 2003) will greatly increase the
discovery rate. Based on current GRB detections, we guess roughly 20 to
100 per semester.

4. Coordinates:

      4.1. All over the sky.

      4.2. Moving target:  no

      4.3. Time critical: very


5. Spatial scales:

      5.1. Angular resolution (arcsec): any ALMA resolution

      5.2. Range of spatial scales/FOV (arcsec): point sources

     
5.3. Single dish total power data: no

      5.4. ACA: no

      5.5. Subarrays: could do


6. Frequencies:

      6.1. Receiver band: 3, 6, 7, optionally 9

      6.2. Lines and Frequencies (GHz): --- continuum
                
      6.3. Spectral resolution (km/s):  --- N/A

      6.4. Bandwidth or spectral coverage (km/s or GHz):  --- 8 GHz


7. Continuum flux density:

       7.1. Typical value (Jy): 0.001-0.1 (detection, based on current
       RSN detections)

       7.2. Required continuum rms (Jy or K): 0.00006 (.06 mJy)

       7.3. Dynamic range within image: >4

8. Line intensity:

      8.1. Typical value (K or Jy): N/A

      8.2. Required rms per channel (K or Jy): N/A

      8.3. Spectral dynamic range: N/A

9. Polarization:  no

10. Integration time for each observing mode/receiver setting (hr):
typically
      1/60 hr for Band 3 
      3/60 hr for Band 6 
      10/60 hr for Band 6 
      0.5 hr for Band 9
      
11. Total integration time for program (hr): 0.5-1 hr for null detection. 
     If there should be a strong detection, requested monitoring program
     will last for 3-4 days, totaling 10 hours.
    
     Estimated ToO time every semester:  on average, 10-30 hours for
     afterglow searches.

12. Comments on observing strategy (e.g. line surveys, Target of
       Opportunity, Sun, ...):

This is a target of opportunity proposal. The ToO window is very small
for GRBs; to date, only SN 2003dh/GRB 030329 has been studied with any
regularity in the mm.  Detection of these extremely energetic objects is
critical.  This project is very similar to the RSN ToO program, and will
require dynamic scheduling and notification and input from the observing
team.

**********************************************************************

Review Chris Carilli: Sensitivies look OK.  For purposes of DRSP they
should be more explicit on the reaction times -- how quickly do we
need to get on source to make this interesting?

Reply Turner: We dont' know what GRBs are, but assuming they are
supernovae, Kurt Weiler's models show that they peak 8-12 hrs after
the SN. So the answer is, observations need to be scheduled ASAP after
the SN, within 2-3 hours ideally, or even faster. Obviously this will
not always work since SN are caught at different stages of evolution,
but if you wait 12 hours you will probably never see anything in the
submm. At this point so little is known about progenitors of either SN
or GRBs that the interruption is well justified.