README web version of /home/usg/OPS/MTS/readme_xml/readme_60943100

Principal Investigator Email Address

• milvang@astro.ku.dk

Estimated Total Execution Time (hours, including overheads)

• 1.25

General Description

• Overall description:
  To detect and determine the spatial distribution of Lyman alpha emission
  at z = 2.711 (observed lambda = 451 nm) from the host galaxy of GRB 060714,
  using the IFU for a total exposure time of 1 hour.
  
  Abstract of proposal:
  GRB host galaxies are often intense emitters of Lyman alpha photons. It is not
  rare to detect Lyman alpha emission (from the host) in afterglow spectra. One
  nice example is provided by GRB 060714 at z = 2.711: an afterglow spectrum
  taken 8.5 hr after the GRB showed bright Lyman alpha with flux
  1.3 x 10^{-17} erg/cm^2/s (luminosity L = 10^{42} erg/s).
  Surprisingly, in a late-time spectrum of the host (1.7 yr after the GRB) there
  is no Lyman alpha down to a 3 sigma flux limit of 1.1 x 10^{-18} erg/cm^2/s,
  which is a factor of >10 lower than our previous measurement. If confirmed,
  such variability would be puzzling to explain, and would indicate a profound
  influence of the GRB on the galaxy environment. A possible reason to fake
  the "disappearance" of the line could be a complex spatial geometry of the
  emitting region, which may have been included by the slit in the first
  spectrum but not in the second. We propose here a snapshot (1 hr) observation
  with the X-shooter IFU of this system to look for the "disappeared" Lyman
  alpha emission and to study its spatial distribution.
  
  Description of the observing strategy:
  As mentioned above, the essence of the proposal is to detect Lyman alpha
  emission at z = 2.711 (observed lambda = 451 nm). This means that we optimise
  our observing strategy for the UVB domain and not for the NIR domain.
  We have chosen to split our 1 hour integration time in 2 exposures
  in UVB+VIS due to cosmics. We do not want to apply any offsets on the sky
  between the exposures.
  The acquisition is done on a reference star (magnitudes R = 21.6, B = unknown;
  we assume that 60 sec B-band is suitable for the acquisition image),
  followed by a blind offset.
  The expected S/N of the entire emission line is about 3-5.
  We will use 1x2 binning in UVB+VIS to increase the S/N a bit. We are not
  worried about the slight undersampling this may produce with the IFU, since
  the Lyman alpha emission line is expected to be broad, and since there are
  no strong skylines at 451 nm.

Waiver Requests

• Waiver Request for OB execution time = 1 h 15 min:
  submitted 22-Jul-2009 (WaiverID: 60.A-9431A.01),
  approved 22-Jul-2009 (by Vincenzo Mainieri).

Critical Observing Condition Constraints

• None besides what is specified in the Constraints Set for the OB.
  
  We are observing a faint emission line (S/N = 3-5 of the entire line) in the blue
   (451 nm) and with the IFU for which no ADC is possible, so dark time and low airmass
   are highly beneficial.

Time-Critical Aspects

• None.
  
  The target is only observable in the August SV run, with the constraints being met
   every night at the beginning of the night.
  
  The target is not observable in the September SV run.

Special Execution Requirements

• Since we understand that the ADCs cannot be used with the IFU, a small
   airmass is preferred.

Special Calibration Information

• None --- we assume that spectrophotometric standard stars to enable a
   flux calibration are part of X-shooter's calibration plan.

ToO Information

• ---(Empty)---

ToO Activators List

• ---(Empty)---

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

• YES

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

• YES

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

• YES

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

• N/A

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 ?

• N/A

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