README web version of /home/usg/OPS/MTS/readme_xml/readme_81012800
Principal Investigator Email Address
Estimated Total Execution Time (hours, including overheads)
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 "SN2008xx".
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 2hr45min we estimate.
For subsequent observations, we will adjust our estimate accordingly.
Waiver Requests
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.
We have not used any User priority in the OBs since all observations should be done
on the
same night, consecutively. Obviously, for linear polarization measurements, observations
with all 4 plates must be done.
Time-Critical Aspects
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
4 seconds 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
1hr. We will adjust the observing time when the brightness of the selected SN
is known.
With our name convention, the sequence of observations should therefore be:
ToO_SN2008xx_PMOS_1angle_1, ToO_SN2008xx_PMOS_3angles_1, ToO_SN2008xx_PMOS_1angle_2,
ToO_SN2008xx_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 2x890s.
ToO Activators List
Is this a Pre-imaging run ?
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 ?
Do all your finding charts comply with both the general and instrument-specific
Phase 2 Web Pages ?
If you submitted OBs for standard stars, did you specify the magnitude
and spectral type of all standard stars in the OBs ?
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?
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 ?
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 ?
Last creation of page: Tue Oct 6 15:40:23 2009
If you have comments, please contact usd-help@eso.org