README web version of /home/usg/OPS/MTS/readme_xml/readme_84071900

Principal Investigator Email Address

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gaston@das.uchile.cl
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Estimated Total Execution Time (hours, including overheads)

We plan to use the whole 10 hours assigned

General Description

This is a ToO programme designed for the intensive spectroscopic
follow-up of a very young Type Ia supernova (SN). We will select a SN
that will be discovered by the CHASE programme which has been running in
the last few years using the PROMPT telescopes at CTIO, and
successfully discovering young SN events. The observing goal is to
obtain a time-series of UV-optical-NIR spectra during about two
weeks soon after explosion, as the SN is rising to maximum light. 
It is critical for the success of the programme to obtain repeated
observations on a nearly nightly basis. In particular, during the first
week after the observations are triggered, we would like to obtain one
spectrum every night if the observing conditions are given. After
that, we may relax this requirement but still try to obtain a nearly
nightly cadence (see more details in Time-Critical Aspects). 
In order to clearly identify spectral lines and to be
able to discriminate among models we would ideally need the spectra to
have S/N > 50 (S/N > 30 in the NIR). For the very first epochs, when
the SN is still faint (V~18 mag), this may not be possible to achieve,
so we have constructed a set of OB's indicated for the case of a faint
SN, using longer exposure times and more stringent constraints, where
we set lower S/N requirements.

Waiver Requests

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No Waiver Request was submitted
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Critical Observing Condition Constraints

It is most important for our programme to be able to obtain spectra on
 a nearly nightly basis and starting as soon as possible after the SN is discovered.
 We thus have relaxed the observing constraints in our OB's to increase the chances
 of obtaining a spectrum even if the conditions are not ideal.

Time-Critical Aspects

If possible, we would like to obtain a spectral time-series with a nearly
 nightly cadence. In particular, right after the observations are triggered, while
 the SN is very young and evolving fastest, we would need spectra obtained every
 one or two nights. One of the people in the activators list will be online to evaluate
 the data quality in real time and communicate with the observatory for further observations.
 This type of intensive follow-up is planned to occur only once during the semester.
 We have been assigned a similar amount of time at Gemini, so that if our SN occurs
 while both the Gemini and ESO semesters are underway (Oct-Jan), we could combine
 both facilities to relax the load on each of them.
Our ideal observing plan, although it is impossible to completely determine in advance,
 would consist of:
- 1 spectrum per night during the first week after the discovery (~6 hours)
- ~5 additional spectra during the second week until maximum light (~3 hours)
- 1 or two specta within the first (~1 hour)
(As said above, this can be shared between VLT and Gemini).

Special Execution Requirements

If possible, we would need to retrieve the data for quick analysis during
the day after they were obtained in order to make decisions for further observations
during follow-up. If this is not possible, some feedback from the observer regarding
the quality and S/N of the spectra would be of great help. We would ideally require
S/N greater than 50 in the optical range, and greater than 30 in the NIR, except
probably for the first few epochs if the SN is too faint (V >~ 18). While the
SN is rising, this will require the use of varying exposure times which the ToO
activator would like to help determining in correspondence with the observatory
staff. Also, there may be the need of modifying observing constraints as the SN
evolves in brightness. We have built sets of OB's for the cases of a faint and a
bright SN. The whole set of parameters, however, is difficult to determine in advance.

SNs generally occur within their host galaxies in regions which may present strong
brightness gradients. Therefore in most cases the background emission will not be
negligible and will cover the whole length of the slit. In order to allow a clean
sky subtraction in the NIR arm, we have built OB's which use the SHOOT_slt_obs_FixedSkyOffset
template. Since we do not know the field at this stage, we have set the RA and DEC
offsets between SN and sky to zero. These offsets will be determined by the activator
when the finding chart is built. Some SNe, however, appear isolated in the outskirts
of their galaxies. For those cases, we included OB's that use SHOOT_slt_obs_AutoNodOnSlit
template so that a clean NIR sky subtraction is possible without having to observe
a nearby empty field. For the possible case of a SN that becomes much brighter that
the sky background in most of the NIR range, we have added OB's that use the simple
SHOOT_slt_obs_Stare tamplate.
We will define which OB should be used and parameters auch as the exposure time
based on the characteristics of the SN field.

Special Calibration Information

We have not included special calibration OB's, as we have read in the
 instrument manual that two spectrophotometric standards and two telluric standards
 will be obtained every night. We would like to say, however, that we prefer solar
 type telluric standards for our calibration. In an ideal case, such telluric stars
 should be observed at an airmass similar to that of the SN spectrum. All other standard
 calibration frames should be sufficient for our purposes.

ToO Information

This is a Target of Opportunity programme. The observations will be triggered
 to start the follow-up of a supernova that will be discovered by our search programme
 (CHASE). It is critical for our science purposes that the first spectrum is obtained
 as early as possible. We will make our greatest efforsts to send the trigger early
 diring the day with the hope that a spectrum can be obtained on the night right
 after. Once the first observation is triggered we plan to carry out an intensive
 spectroscopic follow-up which ideally would mean obtaining spectra on a nightly
 basis for about two weeks. The programme activators will be online to interact with
 the observatory staff in order to help planning follow-up observations.

ToO Activators List

PI: 
Gaston Folatelli, gaston@das.uchile.cl
Additional activators:
Giuliano Pignata, gpignata@das.uchile.cl
Francisco Forster, fforster@das.uchile.cl
Joseph Anderson, anderson@das.uchile.cl
Maximilian Stritzinger, mstritzinger@lco.cl
Mario Hamuy, mhamuy@das.uchile.cl
Jose Maza, jmaza@das.uchile.cl

Do all your OBs comply with the instrument-specific requirements listed on the instrument-specific Phase 2 web page ?

Do all your finding charts comply with both the general and instrument-specific Phase 2 Web Pages ?

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N/A
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If you submitted OBs for standard stars, did you specify the magnitude and spectral type of all standard stars in the OBs ?

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N/A
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Have you specified the S/N ratio at given wavelength in the User Comments field of each OB?

Have you included OBs for any calibrations that you need but which are not part of the Calibration Plan ?

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N/A
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If you are observing Moving Targets, have you attached suitable ephemeris files to your OBs?

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N/A
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If you have preferences which OBs should be executed first, did you make use of the User Priority field in the OBs ?

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N/A
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If this is a run that requires coordinated observations with other facilities, did you give proper instructions in the Time-Critical Aspects Section ?

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N/A
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Last creation of page: Tue Oct 6 15:40:32 2009
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