Perfecting Type Ia Supernovae as Standard Candles

Background

In case of a ToO request:

What am I required to do?

The NOT-OPC has given an override status to the Type Ia Supernovae program during P44. Time allocated to this program is maximum 1 hour per night, totaling to ~55 hours on Alfosc and 2.5 hours with FIES. Any observer at the NOT must be willing to carry out the observations, unless she/he is not able to perform observations with the requested instrument. (See also Rules for Target-Of-Opportunity programs .) The observer will be acknowledged in any paper based on these observations or, depending on the degree of the participation, be offered co-authorship as decided by the PI. If a ToO is triggered but for any reasons the observations cannot be done on the first night, the ToO remains active for the next night too. However, the PI is still required to confirm this by sending e-mail to the observer and the NOT staff (or calling in the control room).

What information will I get?

The PI or his deputies (Vallery Stanishev, Rahman Amanullah, Ariel Goobar, Francesco Taddia) will phone to the control room and send an email to the observer with full instructions on what to observe and how to carry out the observations. These will consist of:

- Coordinates of the SN and a photometric and a spectrophotometric standard + finding charts
- When the observations should be performed.
- The requested filters and grisms with exposure times and number of images to be obtained.
-Any possible calibration frames, arc-lamp spectra, biases, photometric and spectral flat fields, photometric standards;
- scripts for automatic execution of the observations are available at NOT observing computer (in ). For the moment only scripts for ALFOSC are available. A description of how they work and how they are to be used can be found here. Further down in the web page there is an example of the instructions that are sent to the observers.

What do I do?

ALFOSC

The observations will be performed by executing the observing scripts in the way precisely specified in the activation e-mail. In most situations, the observer will simply need to copy the required commands to the Sequencer command window and follow the instructions printed on the screen. In the case of failure of some of the scripts, at the end of the activation e-mail there are detailed instructions how to preform the observations without the scripts.

Before starting the observations there are several steps to be done. They are highlighted bellow along with several other steps that need to be done manually.

1. If you are not familiar with ALFOSC, then check the instrument web pages and cookbook. You may also contact by phone the introducing support astronomer.
2. Before starting the observations, you will need to focus the telescope following these instructions. Note that all the scripts will ask if the telescope has been focused. Answer 'yes' is already done and 'no' to abort the execution of the script.
3. For imaging, the photometry script will automatically perform all the necessary steps to execute the observations. Normally it will obtain short ~30-180 sec exposures in the standard UBVR and i(the I-band filter is #12 from the NOT catalog) broad-band filters. Because the SNe will be normally bright, AFTER THE SCRIPT FINISHED, PLEASE CHECK THE SUPERNOVA FOR SATURATION AND IF NEEDED REPEAT THE EXPOSURE(S) WITH REDUCED EXPOSURE TIME.
4. If requested and conditions are photometric, observe photometric standard field(s). This will normally be one of the fields listed here with pointing coordinates available from the TCS catalog alphot.cat.
5. During the evening/morning twilight obtain a set of sky flats following these instructions.
6. For spectroscopy, the spectroscopy script will automatically obtain the necessary observations. The only step that needs to be done with manual intervention is the acquisition of the SN on the slit. For this the spectroscopy script first calls the NOT object acquisition script to place the SN on the slit. Please, follow the instructions and iterate at least once the centering on the slit. Then the script will then take all needed exposures.
7. All the images taken the the scripts will be automatically copied to the appropriate directory. Only the calibration images need to be copied manually. Copy the calibration images (flats, biases, ect.) taken during day/twilight time (and if you also take some in morning/day after the observations, copy them later too) from /data/alfosc to /data/too/P44/Stritzinger.
   It is important to do that on the observing computer.
8. Send an email to the SNe Ia project PI max.stritzinger@astro.su.se, and to all e-mails specified in the instructions with a brief description of the observations taken (or if not taken, the reason) and approximately how much time you spent in total. Add in the End-Of-Night report, which images were made, and approximately how much time you spent in total.
9. If you have any problems or questions related to the operation of ALFOSC, contact your support staff on duty.

An example of the detailed observing instruction you will receive is given below.

Dear Observer,

 I would like to activate ToO observations I would to activate ToO
observations of SN 2009dc on 6 May. (ToO program 
"Perfecting Type Ia Supernovae as Standard Candles").  
I need 1 spectrum with 15 min exp.time (gr#4,slit 1") and UBVRi
imaging with 120,30,30,20,20 s exp. times. Attached is a finding
chart. Below are the instructions to do the observations using 4
scripts that should make the observation easier to carry out. Note
that all 4 scripts will ask if the telescope has been focused. They
also check if the requested set ups are available and if not exit with
error and suggestion how to proceed. If the scripts are run without
any parameters, they will print a help message.

Here is a list of the commands in the order to be executed (for the
purpose of copy and paste) and bellow are the detailed instructions. 
At the very end of the e-mail I also attach the instruction to perform
the observations manually, in case the scripts do not work.

***

All commands bellow are to be executed in the Sequencer window.

tcs.append-object sn2009dc 15 51 12.12 +25 42 28.0  2000 0 0 0

cd ~obs/scripts/44-024

./point_sn.script sn2009dc --para

./spec_sn.script sn2009dc 900 Grism_#4 Slit_1.0 400 20 3 5  /data/too/P44/Stritzinger

./point_sn.script sn2009dc

./phot_sn.script sn2009dc /data/too/P44/Stritzinger u,120,1 b,30,1 v,30,1 r,20,1 i,20,1


****

Thank you very much.

Cheers,
Maximilian Stritzinger

**********

To perform the observations with the scripts you should:


1. Starts ALFOSC and focus the telescope following the instructions:

Please, focus the telescope WITHOUT filter in the beam
following the instructions in the ALFOSC web page
'Focusing the telescope using the focus pyramid' at

http://www.not.iac.es/instruments/alfosc/focus.html

and set the focus with to the correct value 'nnn' with the TCS
command 'foc-pos nnn'. Before starting the focusing give the TCS
commands 'foc-del 0' and 'foc-pos 23230'


2. append the object to the currently loaded catalog by executing in
the sequencer window the command:

tcs.append-object sn2009dc 15 51 12.12 +25 42 28.0  2000 0 0 0

3. In the sequencer window CD to the scripts directory:

 cd ~obs/scripts/43-008

4. To point to the SN for spectroscopy execute:

 ./point_sn.script sn2009dc --para

The scripts will ask if NOT has been focused.  Answer 'y' if yes.
This will also acquire guiding star and reset the CCD
with full unbinned range. If this fails again, please point
the telescope in the normal way and continue to point.3.

5.  To acquire the SN on the slit and execute all needed observations
execute:

./spec_sn.script sn2009dc 200 Grism_#4 Slit_1.0 400 20 3 5 /data/too/P44/Stritzinger

The script first calls the NOT object acquisition script
to place the SN on the slit. Please, follow the instructions and iterate
at least once the centering on the slit. Then the script will take all
needed exposures.


6. To point to the SN for photometry execute:

 ./point_sn.script sn2009dc

7. to do the photometry execute:

./phot_sn.script sn2009dc /data/too/P44/Stritzinger u,120,1 b,30,1 v,30,1 r,20,1 i,20,1

(!!!NOTE THAT THERE IS NO SPACE AROUND THE COMAS!!!!)

The script will also ask about the telescope focusing.

8. If the conditions are photometric, please observe a photometric standard 
field immediately after the SN photometry (at similar airmass). 
I prefer any if the PG fileds.

 We will need 3 flat fields for each imaging filter used.
Sky flats are preferred, but if it is not possible to obtain sky
 flats, dome flats are also an option. I will also need 10 additional spectral 
flats with the set-up used for the SN observations (taken during the day). Copy  
these files to "/data/too/P44/Stritzinger" using the observing  computer.




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

MANUAL INSTRUCTIONS
to be used only in case the scripts (or some of them) do not work


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


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

The SN coordinates are:

R.A.  =  15 51 12.12
Decl. =  +25 42 28.0

Attached to this message is a finding chart in which the SN is marked.


1. activate the autosaving and the remote file saving by executing the
following two commands in BIAS:
"autosave_on"
"rempath /data/too/P44/Stritzinger" and "remsave_on"

2. Give the following TCS command 'i-p-a 0' (zero,
     not "Oh") and then  point the telescope by using the
     CATALOGUE function 6 'Preset w par ang',
     (instead of the usual 4 'Preset to this'). This is to align the
     slit along the paralactic angle.

3. make sure to remove any filters from the beam

4. in BIAS give the command "resetxy"

5. Center the supernova on the slit by:

   a) Switch on the SlitOffset postprocessing task in the ALFOSC
Postprocess window, and switch off the other postprocessing tasks.
   b) Select the slit in the Options box of the SlitOffset tool.
   c) Take a short image of the target with SlitOffset task on.
   d) After the image has been read out, a ds9 window will pop up. Put
your cursor on the target in that window.
   e) Type 'x' to get the cursor position in the slit, or a for a Gaussian
fit of the nearest point source.
   f) Type 'q' to let the telescope make the required offset.
   g) Wait a moment and the TCS will offset the telescope so that your
object is on the slit.
   h) ITERATE, steps (ag-on) at least once, especially if the telescope
is moved a large distance.


6. Now the star should be centered on the slit, and should be on
   column x=1050. (this is the default "x" position, which is
   seldom changed; the "y" position depends on the slit).
   If the star is on x=1050, then:

7. in BIAS give the following two commands in order to
set the  CCD window: "xbeg 850" and "xsize 400"

   (if the star is on another "x" position, let say N,
then give "xbeg N-200" and "xsize 400"
instead)


8. take one short image to make sure that you gave the
right  numbers and the star is still on the CCD (it should
appear  centered along the x-axis).

9. Load grism #4 and the slit (the same slit used to center the star)

10. Take 2 flat fields with the ALFOSC internal halogen lamp with
    exposure time 20 sec.

11. take one 15 min exposure of the SN.

12. take 2 more flat fields.

13. take a spectrum of the He and Ne arc lamps simultaneously with exposure time 3 sec.


Steps 10-13 have to be obtained with the telescope
pointing to the SN and preferably without changing the optical
configuration of ALFOSC, i.e. without putting the grism or the slit out
and in.

14. in BIAS give the following 2 commands:


    a) "resetxy"
    b) "field-rotation +90"

15. Take UBVRi images with the following exposure times:


   U=120s
   B=30s
   V=30s
   R=20s
   i=20s

16. disactivate remote saving
"remsave_off"

I will need 3 sky flats-fields per filter. We also need 10 spectral flats with grism 
#4 and 1" slit, and the internal halogen lamp with the CCD window used for the spectra 
(taken at the end of the nights). Copy these files to "/data/too/P44/Stritzinger" using 
the observing computer. 

FIES:

The aim is to obtain the FIES observations during service/technical nights and will normally be excuted by NOT staff

The PI of this project is Maximilian Stritzinger.