Title ToO Observing of Radio Supernovae - Pi S. Van Dyk Time 50 hrs per semester 1. Name: ToO Observing of Radio Supernovae -- Schuyler Van Dyk, Kurt Weiler et al. 2. One short paragraph with science goal(s) The radio emission from supernovae (SNe) is one of the best probes of the final stages of evolution for the stellar progenitors. The nonthermal synchrotron arises from the interaction of the SN shock with the pre-supernova, wind-established, circumstellar medium (CSM). Knowledge of the CSM provides strict constraints on the progenitor's nature and evolution. However, the particle acceleration process is still not known, and the absorption mechanism, which arises from the CSM, is not completely obvious. Although progress has been made at centimeter wavelengths over the last two decades, little has been accomplished in the mm and submm due to the sensitivity constraints and difficulty in scheduling ToOs. Observing radio SNe (RSNe) at high frequencies will help constrain both the emission and absorption processes. RSNe turn on quickly, within hours, and become optically thin within days in the ALMA bands. It is essential and indeed possible (with early SN warning arrangements) to observe with ALMA the early hours of a SN's evolution. A Virgo Cluster analog to the well-studied SN 1993J would reach ~2 mJy at max within 10 days; this analog easily could be detected out to a distance of ~60-70 Mpc. Of special interest are Type Ia RSNe, which evolve extremely fast and have yet to be detected at cm wavelengths. We also need to be prepared for the next Galactic or Local Group SN. The precise astrometry afforded by ALMA will also allow, in many cases, the pinpointing of the optical progenitor. This ToO would identify targets for the Monitoring program is also proposed as a standing program for followup studies of the light curve at later times. 3. Number of sources Based on current supernova searches, we anticipate approximately 2 to 20 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 Band 9 (only if detected) 11. Total integration time for program (hr): 0.5 hr for null detection, if detected total ToO monitoring time over 2 weeks is 10-20 hrs Estimated ToO time every semester: on average, 50 hours, based on current monitoring programs at the VLA. 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 mm to submm emission from RSNe, hours at best. The higher the frequency, the shorter the rise time for the emission; models of SN1993J predict a peak emission 2-3 days after optical peak for band 7, and ~10 days after peak for band 3. The investigators would notify ALMA staff immediately of the detection of a SN and would have an observe file ready to go for bands 3, 6, and 7. This observe file would be 0.5-1 hr in length, depending on the distance to the host galaxy. If a solid detection is made, then this ToO program would request additional monitoring observations, including Band 9. The ToO monitoring program would extend up to 2 weeks, observing for 2-4 hours for the first 4 days, (1 hr observe file every 4 hrs), and then daily to day 14. After 2 weeks, the light curve is changing slowly enough that a standing RSN monitoring program would kick in. The scheduling of this ToO requires a significant amount of input from the observing team. The number of hours of ToO monitoring depends on the source: for a source like SN 1993J, in M81 at a distance of 3.5 Mpc, this could amount to observations every 4 hours for the first 4 days, and every 0.5 day for the next two weeks, for a total of 36 hrs for the light curve of the first two weeks. However, nearby supernovae like SN1993J are rare, occurring perhaps once every four years. More typical are RSN at the detection limit. Since the radio light curve falls to half its peak within ~8 days at 330 GHz (Band 7), within ~ 14 days at 230 GHz (Band 6), and ~20 days at 110 GHz (Band 3), the number of hours would be fewer for weaker sources, perhaps only 20, since they would quickly fall below detectability. This project could be done with a subarray, but the observing files would then increase in length from 0.5-1 hour to several hours. *********************************************************************** Review Leonardo Testi (programs 3.5.5 and 3.5.6): The first (3.5.5) is a ToO to measure mm fluxes of SN close to maximum, the second (3.5.6) requires monitoring of a few SN. I could not really tell which is and if there is any difference in the targets between the two projects. I would think that one finds a bright supernova and then will want to follow it in the framework of the first project (? maybe I am missing the point here?). I think these should be combined in a single project that finds and follows the supernovae. Total time, for the three years (is it really required? how many SN you need?) would be a total of 2semx50hx3y=300h for the first part and 2semx30hx3y=150h for the second, and a grand total of 450 hrs. Following the time estimates, this time will correspond to approx 6-10 supernovae for the "first part" and 10 per semester for "second part". Taking into account the "visibility" of SN for the monitoring, the time requested will allow to monitor approx 15 SN/yr, so it appears oversized compared to the first part (one finds 10 SN in 3 yrs, not all will be bright enough for monitoring, then how one selectes the ~45 SN for the monitoring?). I would say that, given the time requested for finding candidates, the monitoring should not exceed a total of at most 50hrs. This programme challenges operations, information- and data-flow. What is particularly critical is programme 3.5.5 (obviously). It is important to have this programme in to set the appropriate requirements on software and operations plan. Reply Jean Turner: Leonardo raises some good points. I attach slightly modified DRSPs. The first point is regarding why these are two DRSPs: the basic answer is that they are different kinds of scheduling. One is dynamic, the other not. I think the ToO should be separate from the monitoring. This is currently how it is handled at the VLA. The second is regarding the relative time estimate of the ToO and monitoring programs; Leonardo is making the reasonable assumption that they are the same sources, when in fact, they are not necessarily. Some RSN are detectable for nearly a decade, others fade within months. It is my impression that there are more RSN than can currently be monitored at the VLA, so only the "best" are followed. Generally the monitoring programs will be following RSN discovered outside the 3 yr time frame here (and this will be true for ALMA, which will initially be following up RSN discovered with the VLA). At some level the amount of time devoted to both of these programs, the ToO and the subsequent monitoring, is somewhat arbitrary. One can't monitor all the RSN. These numbers are roughly consistent with what is currently done at the VLA. It could be different for ALMA. The change I made to the DRSPs was to include in the total time request "based on current VLA programs" to explain the time estimate, which would address the 2nd point Leonardo raised. Comment Ewine: new DRSP is now baseline -------------------------------------------------- Review v2.0: 3.5.5 ToO Observing of Radio Supernovae van Dyk 50 Did not change from earlier proposal, wich was extensively refereed.