Priority on ToO?

[Ashley Villar]

Hi -

I have a general question on the priority of transient observations, which I can't quite find in the primary documentation (but please let me know if it's there!). I would like to put together a ToO-based proposal for following up exotic supernovae which evolve on ~weeks timescales. Often we are using several telescopes to develop a spectral sequence in this timeframe. The observations are not exactly "urgent" for this reason, and we will likely have more targets than observing time throughout the trimester (i.e., if we miss on  interesting SN 2022xyy, interesting SN2022xyz may pop up in the next week). Would such a science case be appropriate for P1, or would these be considered P0? If I request very early observations (which now must be completed in days), would that be considered P0?

Thanks so much!

Ashley

[Steven Janowiecki]

Hi Ashley,

That's a good question, and probably more nuanced/complex than is covered in our documentation.

Right now the HET's observations are dominated by the HETDEX survey which uses Priority 0 time to observe its survey fields during dark time. If you want to observe at the same time as HETDEX, your program must have Priority 0 time in order to "interrupt" HETDEX. To calculate whether or not a given target collides with HETDEX on a given night, you can use this tool:

https://het.as.utexas.edu/HET/hetweb/ProgramPrep/hetdexcalendar.html

If your target does not conflict with HETDEX, then I would say that Priority 1 is usually adequate to get observations on timescales of days (weather-permitting, of course). We have had some other supernova programs in the observing queue and they make use of the SYNDATE keyword which lets them specify the nights on which an observation would be useful. That helps us as we observe from the queue -- if we see a Priority 1 target that is observable only for a few nights, it will usually be the target of choice.

I know it's probably hard to know in advance whether a supernova will go off in a galaxy which is conflicted with HETDEX or not, but I hope that helps give you some perspective anyway. You might use that argument to justify asking for some P0 but mostly P1 time -- use the P0 time to observe really important time-sensitive targets which are in competition with HETDEX, and use the P1 time to observe those which are not conflicted.

Happy to help more if you have other questions about strategy, target submissions, etc!

Steven

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