Principal Investigator Email Address
luc@as.arizona.edu
Estimated Total Execution Time (hours, including overheads)
2hr30minutes
General Description
The purpose of this ToO proposal is to measure the linear polarization from one supernova (SN), at eight epochs of its evolution, sampling from a few days to a few months after discovery. Here, we submit the template set of OBs to be used at each of these epochs. We require a unique setup for these observations: PMOS mode, 1.0" slit, 300V grism, GG375 filter. Linear polarization will be measured from observations at 4 waveplate angles (0, 22.5, 45, 67.5 degrees). Only one target will be followed. Since its name is not presently known (object yet to be discovered), we presently use the preliminary calling "SN2007xx". We will provide the RA, DEC, finding chart, and target name at trigger. The exposure time may be adjusted if the object is brighter/fainter than the 14th magnitude assumed in the proposal. Since it is unclear how much overhead time there will be, the first set of observations could be slightly longer than the 2hr30min we estimate. For subsequent observations, we will adjust our estimate accordingly.
Waiver Requests
A waiver request was submitted on Tuesday, 31 July 2007, and approved on Wednesday, 1 August 2007. The reason for this request was OBs in excess of one hour.
Critical Observing Condition Constraints
Observations can be done at any lunar phase, provided it is done at more than about 4 days from full moon. Sky transparency must be clear. Our airmass constraint is loose since the 3-4 months SN evolution we will cover may force us to observe at high airmass. At each epoch, observing at the minimum airmass is obviously prefered.
Time-Critical Aspects
This is a ToO program
Special Execution Requirements
In the first set of observations, a PA will be chosen that must then remain fixed for all other observations, at that epoch as well as at all subsequent epochs. No nodding should be done between any observations - we have set a zero offset for that purpose. The target should be placed at the same position along the slit for all observations (science and calibrations). Background subtraction will be done using a region off-target along the slit.
Special Calibration Information
For the data reduction, we will need three calibration observations at each epoch, performed under an identical setup as for the SN target. These standard stars will be chosen when we know the SN target position in the sky and the dates of our likely observations (magnitude and spectral type are therefore not provided). First, we require a flux standard. We submit an OB for this observation since we need to have the observation done with a 1" slit, at one plate angle (lin0). We undertand that this observation will be taken out of our allocated time. Second, we need a polarized standard star, observed with a 1" slit. Since this observation is "as needed", we believe it should not entail any penalty to our allocated time. Third, to ensure the highest confidence on the polarization signal from FORS1 (and we will be demanding calibration accurate to within 0.1% of 0% polarization), we require the observation, at each epoch, of a null standard. We understand that the time associated with this observation will be taken out of our allocated time. The names used for these observations are, in the same order, ToO_Cal_PMOS_Flux_std, ToO_Cal_PMOS_Pol_std, ToO_Cal_PMOS_Null_Pol_Std We have indicated a nominal exposure time of 30 secs for the flux standard, and 1 second for the polarized and null standards (corresponding to a S/N of 200). This is estimated assuming a magnitude of 12, 8, and 8, respectively, and thus, may need adjustment when we select the actual standard stars to be observed. Avoiding saturation is essential in all these observations and so we ask the service observer to ensure that there are enough counts while avoiding saturation.
ToO Information
This is a ToO run. The supernova we are planning to follow-up spectroscopically is yet to be discovered. Necessary characteristics on the SN target will be provided at the time of trigger. As suggested by the ESO help Desk, we have decided to set up our SN target observations so that a first OB does the acquisition and then observes with one plate (0 degree), followed by an OB containing the observations at the three other wave-plate angles (22.5, 45, and 67.5 degrees). These observations should be done in a row, e.g., with the second observation immediately following the first. Provided the observations are carried out in this manner, we believe it will be unnecessary to reacquire the object for this second OB; this should also greatly reduce the overhead. For the first epochs of observation, when the SN target is on its Plateau phase and is therefore bright, the total execution time per OB will be within 1hr05min. For late time observations, when the SN is dimmer, the total execution time is likely to exceed 1hr05min and in this circumstance, the approved waiver will be used. With our name convention, the sequence of observations should therefore be: ToO_SN2007xx_PMOS_1angle_1, ToO_SN2007xx_PMOS_3angles_1, ToO_SN2007xx_PMOS_1angle_2, ToO_SN2007xx_PMOS_3angles_2. Hence, in practice, the selected plates in this sequence will be 0, 45, 22.5, 67.5, 0, 45, 22.5, 67.5 (note that consecutive observations with two identical plate angles should be avoided). At present, the cumulative exposure time for each plate angle is set to 2x900s.
ToO Activators List
The following investigators are authorized to trigger a ToO observation for this programme: Luc Dessart (luc@as.arizona.edu) Doug Leonard (leonard@sciences.sdsu.edu) Stephane Blondin (sblondin@cfa.harvard.edu)
Is this a Pre-imaging run ?
false
Pre-imaging Requirements
Source(s) of Pre-imaging
Pre-imaging sources not listed above
Do all your OBs comply with the instrument-specific requirements listed on the instrument-specific Phase 2 web page ?
If this is a pre-imaging run, did you select PRE-IMAGING for the Observing Category for each Observing Template ?
N/A
Do all your finding charts comply with both the general and instrument-specific Phase 2 Web Pages ?
N/A
If you submitted OBs for standard stars, did you specify the magnitude and spectral type of all standard stars in the OBs ?
N/A
Have you included OBs for any calibrations that you need but which are not part of the Calibration Plan ?
If you are observing Moving Targets, have you attached suitable ephemeris files to your OBs?
N/A
If you have preferences which OBs should be executed first, did you make use of the User Priority field in the OBs ?
If this is a run that requires coordinated observations with other facilities, did you give proper instructions in the Time-Critical Aspects Section ?
N/A
If you have prepared your finding charts with tools other than FIMS, do they comply with the specifications on the FORS1 Phase 2 web page ?
N/A