README web version of /home/usg/OPS/MTS/readme_xml/readme_76047200

Principal Investigator Email Address

• mjm@astro.ex.ac.uk

Estimated Total Execution Time (hours, including overheads)

• 4.0

General Description

• This is a continuing NACO program to monitor the orbital motion of Eps
   Indi Ba,Bb, the nearest known binary brown dwarf system. The separation was 0.732
   arcsec at PA=137 degrees E of N in August 2003. The system also has a very high
   proper motion of 4.7 arcsec/yr. Observations have been made in P73/74/75: a further
   4 epochs are needed in P76, spaced roughly by 1 month throughout the time (Oct-Jan)
   when the target is available.
  
  The N90C10 dichroic is used in order to ensure good AO correction using the IR WFS
   on the brighter of the two T dwarfs, Eps Indi Ba, which has an H band magnitude
   of 11.51. The NACO S13 camera is used to get the best possible spatial resolution
   and sampling, and thus the most accurate astrometry.
  
  Images are taken in each of the J, H, and Ks filters to help reduce systematic errors
   in the astrometry and to look for evidence of photometric and colour variability
   in the T dwarfs. In each filter, a total of 1 minute integration time is taken at
   each of 5 dithered positions on the detector.
  
  Eps Indi B moves at 4.7 arcsec/yr: the 1998 epoch 2MASS finding chart shows its
   predicted 2006.0 epoch position.

Waiver Requests

• 076.C-0472A.01: We requested a waiver to allow the DIT/NDIT values for
   our observations to be changed by the SM astronomer at the time of the observations,
   in order to ensure that the sources do not saturate while good S/N is delivered.
   The product DITxNDIT should remain constant. Date requested: July 22 2005; Date
   approved: July 25 2005.

Critical Observing Condition Constraints

• We have been granted observations with a seeing constraint of 0.6 arcsec
   or better, in order to be able to separate the two sources and obtain accurate relative
   positions. The better the final AO-corrected image resolution is, the better the
   results. All efforts taken to optimise the AO system in order to deliver the best
   possible correction will be most appreciated.
  
  Clear conditions are required for our relative photometric measurements.
  
  There are no strong requirements on lunar illumination or distance of the moon from
   the target.

Time-Critical Aspects

• To ensure good sampling of the relative orbit of Eps Indi Ba and Bb, we
   require observations roughly evenly spaced throughout P76. This clearly depends
   on the availability of the target, the times when NACO is scheduled for service
   mode observing, and weather conditions. Ideally we would like the 4 epochs to be
   spaced by 1 month each in the Oct-Jan timeframe (the source sets in February), but
   practically speaking, spacings of 0.5-1.5 months would be ok.
  
  Thus we have imposed time constraints in the OBs with each epoch in a 2 month window
   and with 1 month spacings between the epochs.
  
  IMPORTANT: These windows are designed to allow for flexibility and thus they overlap.
   However, in general, it makes no sense to execute the OBs for two epochs on the
   same night or within a few days. Please try and space the epochs sensibly throughout
   P76!

Special Execution Requirements

• DIT=10 secs and NDIT=6 have been specified in the OBs for the Eps Indi
   B observations, but experience with NACO shows that it is very difficult to specify
   in advance the DIT which ensures that both Eps Indi Ba and Bb are well-exposed but
   not saturated.
  
  Therefore, we have been granted a waiver allowing us to instruct the SM observer
   TO ALTER DIT AND NDIT to give well-exposed (i.e. high S/N) but not saturated images
   for both sources. If this adjustment is made in the H band (where the T dwarfs are
   effectively brightest), the same values of DIT/NDIT should also be ok for J and
   Ks (taken in the same OB). The product of DIT and NDIT should remain fixed at 1
   minute.
  
  As with Eps Indi Ba,Bb, the DIT/NDIT used for the astrometric calibrator (HD208371/HD208372)
   should also be tuned to ensure that both stars are well-exposed but not saturated.
   The nominal values are DIT=1 sec, NDIT=15, a total of 15 seconds.
  
  The same waiver was granted in P73, P74, and P75.

Special Calibration Information

• We have provided OBs for measurements of an astrometric binary standard
   (HD208371/HD208372) for measuring the image scale and orientation. Each time Eps
   Indi Ba,Bb is observed, the astrometric calibrator MUST BE OBSERVED without any
   adjustment of the NACO instrument and mounting. Ideally, these observations should
   be made immediately preceding or following the Eps Indi Ba,Bb observations.
  
  As with Eps Indi Ba,Bb, DIT/NDIT used for HD208371/208372 should be tuned to ensure
   that both stars are well-exposed but not saturated. The nominal values are DIT=1
   sec, NDIT=15, a total of 15 seconds.
  
  The finding chart for HD208371/208372 is a 1x1 arcmin section of the 2MASS H atlas:
   both sources are seen, separated by 9 arcsec.

ToO Information

• N/A

ToO Activators List

• N/A

Is this a Pre-imaging run ?

• false

Pre-imaging Requirements

• N/A

Source(s) of Pre-imaging

• NACO

Pre-imaging sources not listed above

• 2MASS

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

• YES

If this is a pre-imaging run, did you select PRE-IMAGING for the Observing
 Category for each Observing Template ?

• N/A

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

• YES

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

If you have PSF reference star OBs, do the names of those OBs begin with
 PSF_ ?

• N/A

If there are Finding Charts attached to your OBs, is the field-of-view
 of at least one of these charts 2' x 2' (with clearly labelled field orientation)
 ?

• YES

Have you clearly marked and labelled your wavefront reference objects
 R1, R2, R3, ... (as specified in the NAOS Preparation Software) on your Finding
 Charts ?

• YES

Have you specified the magnitude of the brightest object in the field-of-view
 for each OB ?

• YES

Are there objects in any of your fields (including standard stars) which
 are brighter than the limits specified in the User Manual and on NACO web Pages
 ?

• NO

If the previous answer is yes, have you given a list of OBs and a justification
 for the brightness limit violation in the general description field ?

• N/A