Supernova Target-of-Opportunity from the iPalomar Transient Factory – P51-501

Instructions to perform observations for the ToO program "Supernova Target-of-Opportunity from the iPalomar Transient Factory" – P51-501 (PI: J. Sollerman).

Background


This is a Target-of-Opportunity (ToO) programme for core-collapse (CC) and thermonuclear (Ia) supernovae (SNe) at the NOT. The Oskar Klein Centre in Stockholm has recently entered the iPTF survey that started early 2013. This is a major effort to find young SNe just after explosion by using a much higher cadence than ever before. This ToO programme thus merge two previous long-term programmes with the common aim of follow-up and monitoring of young SNe detected by the iPTF. In this investigation we focus in particular on:


Type IIn Supernovae:
SNe IIn interact with their circumstellar environment and therefore show strong signatures of shock interaction. In 2009 we used the NOT for finding and following one of the most distant SNe IIn discovered so far (Amanullah et al. 2011, ApJL, 742, L7). We focus on SNe IIn because: i.) We have a state of the art theoretical machinery to model the shock interactions (e.g., Fransson et al. 2002, ApJ, 572, 350) ii.) These are among the most spectacular SNe, including the brightest ever events. iii.) The interaction with the CSM allows us to probe the mass-loss history of the progenitor star (Taddia et al. 2013, A&A, 555, A10) iv.) SNe IIn may come from very rare stars, like Luminous Blue Variables, where the SN-CSM interaction is one of few probes of their late stages.


Connecting CC Supernova physics to Massive Progenitors:
The most spectacular progress of our CC SN NOT programme the past few years has been our success to monitor several SNe for which we have also identified the progenitor on pre-explosion HST images. The subsequent supernova monitoring, where NOT has played a vital role, allowed us to connect stellar evolution theory to supernova properties. An example is SN 2011dh, where our early progenitor identification paper (Maund et al. 2011, ApJL, 739, L37) was followed by detailed monitoring (Ergon et al. 2014, A&A, 562, A17) and modeling of the light curve (Bersten et al. 2012, ApJ, 757, 31) - enabling us to show that the progenitor was an extended star. We also used the NOT to demonstrate that that yellow supergiant has indeed disappeared. The iPTF early discoveries, where we can catch the cooling phase of the optical light curve, opens up a window to systematically link progenitor stars to supernovae. This is particularly true for the Type Ib/c SNe where we know little about their progenitors.

Thermonuclear supernovae:
Early discoveries of SNe Ia allows us to address key questions that the community has been asking for the past decade. How do we improve SNe Ia as standard candles for cosmology, and what are the progenitor systems of these objects? It is believed that a white dwarf explodes after accreting matter from a companion star, but the second star could be anything from a red giant to another WD. The nature of the companion is expected to affect the early lightcurve (hours to days) of the explosion. In particular one can expect an excess at blue wavelengths originating from the shock caused by the impact between the ejecta and the companion star (Kasen 2010, ApJ 708, 1025). iPTF is the only observing campaign at its scale that also have the cadence needed to systematically find SNe Ia early enough to be able to tell the different models apart. This can be done by early multi band photometry, which also provides important information on the intrinsic colors versus reddening for SNe Ia. The latter is currently a main systematic uncertainty (Amanullah et al., 2010, ApJ, 716, 712) in supernova cosmology.

For the majority of the SNe, we will require optical spectroscopy as well as photometry (UBVRi/ugriz). This can typically be done at any time during the ToO night, as long as the SN is at low airmass.

Instructions

The PI will send an email to the observer with full instructions and may also phone the control room on what to observe and how to carry out the observations.You will be asked to perform one or more of the following:

Spectroscopy of the target SN and a spectroscopic standard with ALFOSC.
Photometry of the target SN with ALFOSC or StanCam.
Acquire bias and flat frames with ALFOSC or StanCam.

This will be achieved using generic sequencer scripts. All scripts are located in the ToO script directory ~obs/scripts/51-501 and are described in detail here. The general procedure for each case is described below. All the necessary information will be provided in the trigger email.

ALFOSC

1. Starting and initializing

If you are using another instrument you have to start and initialize ALFOSC. Instructions how to start and initialize ALFOSC are provided here and here.

2. Focusing

If not already done you have to determine and set the focus position (without filter) in the TCS. Instructions how to determine the focus position are provided here. Determining the focus position is preferred but not required. You may also use the default focus position (23230). The focus position can be set with the tcs.focus-position sequencer command described here or by using the TCS interface directly.

3. Add target SN to TCS catalogue

Append the target SN to the current TCS catalogue with tcs.append-object sequencer command. Command parameters are provided in the trigger email. The command is described in detail here.

4. Photometry

Photometry of the target SN may be done any time during the night when the SN target is at low airmass.

Go to the ToO script directory and run the too-alfosc-photometry.sh sequencer script. This script moves the telescope to the target SN and takes a series of exposures with the specified filters. Script data are provided in the trigger email. The script is described in detail here.

5. Spectroscopy

Spectroscopy of the target SN may be done any time during the night when the SN target is at low airmass.

Go to the ToO script directory and run the too-alfosc-spectroscopy.sh sequencer script. This script moves the telescope to the target SN, positions the target SN on the slit interactively and takes a series of exposures with the specified grism and slit. It also takes spectroscopic flats and wavelength calibration frames. Script data and finding chart to position the target on the slit are provided in the trigger email. The script is described in detail here.

This procedure will usually be requested to be done twice. Once for the target SN and once for a spectroscopic standard. A couple of suitable spectroscopic standards will be suggested in the trigger email. Please use an airmass as close as possible to the airmass of the target SN. A list of spectroscopic standards and their current airmass is provided here.

6. Acquire bias frames

Bias frames may be taken during day or twilight time.

Go to the ToO script directory and run the too.alfosc-bias.sh sequencer script. This script takes a series of bias frames. Script data are provided in the trigger email. The script is described in detail here.

7. Acquire flat frames

Flat frames must be taken during twilight time.

Select a blank field from the TCS catalogue and move the telescope with the tcs.goto-object sequencer command described here or by using the TCS interface directly.

Go to the ToO script directory and run the too-alfocs-flat.sh sequencer script. This script takes a series of flat exposures with the specified filters. Script data are provided in the trigger email. The script is described in detail here.

StanCam

1. Starting and initializing

If you're using another instrument you have to start and initialize StanCam. Instructions how to start and initialize StanCam is provided here and here.

2. Focusing

If not already done you have to determine and set the focus position (with the R filter) in the TCS. Instructions how to determine the focus position are provided here. Determining the the focus is preferred but not required. You may also use the default focus position (23040). The focus position can be set with the tcs.focus-position sequencer command described here or by using the TCS directly.

3. Add target SN to TCS catalogue

Add the target SN to the current TCS catalogue with tcs.append-object sequencer command.. Command parameters are provided in the trigger email. The command is described in detail here.

4. Photometry

Photometry of the target SN may be done any time during the night when the SN target is at low airmass.

Go to the ToO script directory and run the too-stancam-photometry.sh sequencer script. This script moves the telescope to the target SN and takes a series of exposures with the specified filters. Script data are provided in the trigger email. The script is described in detail here.

5. Acquire bias frames

Bias frames may be taken during day or twilight time.

Go to the ToO script directory and run the too.stancam-bias.sh sequencer script. This script takes a series of bias frames. Script data are provided in the trigger email. The script is described in detail here.

6. Acquire flat frames

Flat frames must be taken during twilight time.

Select a blank field from the TCS catalogue and move the telescope with the tcs.goto-object sequencer command described here or by using the TCS interface directly.

Go to the ToO script directory and run the too-stancam-flat.sh sequencer script. This script takes a series of flat exposures with the specified filters. For each filter a test exposure is first taken and the user is requested to adjust the exposure time until a satisfactory count level has been achieved. Script data are provided in the trigger email. The script is described in detail here here.