README web version of /home/usg/OPS/MTS/readme_xml/readme_78077000

Principal Investigator Email Address

• sylvie.cabrit@obspm.fr

Estimated Total Execution Time (hours, including overheads)

• 3 hours

General Description

• Our program aims at detecting in scattered light in H-band the circumstellar
   disk around the T Tauri star RW Aur A, which appears to have been tidally disrupted
   by its companion RW Aur B (located 1.5" away). The goal is to better define the
   morphology of the tidal arm and the physics of the tidal interaction that created
   it. The RW Aur A disk was previously imaged in CO molecular lines at 0.6"x0.8" resolution
   and its tidal arm extends
  from 1" to 4" of RW Aur A (see Cabrit et al. 2006, A&A). 
  
  Based on published images of the circumbinary disk around UY Aur AB, a system of
   T Tauri stars with very similar brightness and colours to RW Aur AB, we expect the
   disk surface brightness to range from 16 to 18 mag/arcsec2 in H-band. To optimize
   sensitivity we will observe in broad-band, placing RW Aur A (H=7.8mag) behind the
   coronographic mask to avoid heavy saturation of NACO. The secondary RW Aur B being
   quite bright (H=9mag) we will use the smallest DIT=0.35sec to remain below a factor
   4 of saturation on it. Use of the S54 camera is then mandatory to keep good sensitivity
   on the extended disk emission despite readout noise. 
  
  Previous experience with the NACO coronograph shows that disk detection will depend
   critically on an accurate subtraction of PSF residuals (reaching 14mag/arcsec2 at
   1.5" of the masked star). We have thus split our 3h into 4 OBs of about 45', two
   on the source and two on a PSF reference behind the mask. 
  
  Target acquisition is performed with NB_1.64 in order to avoid saturation on RW
   Aur A and B (we prefer not to use the H-band + neutral density filter during acquisition,
   as the neutral density filter is mounted on the same wheel as the mask, and therefore
   we would saturate on RW Aur B as soon as the mask is in place).
  
  A short series of imaging exposures (with no mask) in the H-filter + Neutral density
   
  has been added in the OB RWAUrA-1 to allow rough evaluation of the RW Aur A and
   B brightness in H band, for comparison with the extended disk emission and constraints
   on the disk albedo. Given that the stars are slightly variable, we conservatively
   use a DIT = 2sec to safely remain in the linearity regime.

Waiver Requests

• a waiver request was submitted on july 27. the ID is 078.C-0770A.01
  requesting a waiver to exceed a factor 2 saturation on NACO.
  
  The waiver was accepted on sunday 30 july.

Critical Observing Condition Constraints

• - stable seeing conditions are required, for 2 reasons: (1) The scattered
   light in the disk that we wish to image is much fainter than the PSF residuals outside
   the coronographic mask, hence an accurate subtraction of the residuals is critical
   for our science. If seeing is not stable, the sources will move under the coronographic
   mask, and correction of PSF residuals using our PSF reference OB will be very poor.
   (2) our system is a binary of separation 1.5", with a contrast of 3mag at V (and
   1.2mag at H). We will lock the AO on the brightest component (under the mask); however
   if the seeing is unstable, the AO may occasionally jump to the secondary, causing
   strong elongation of the PSF. A stable seeing is thus mandatory to have good AO
   correction on this source.
  
  - we also request observations at airmass < 2, again to ensure as stable a seeing
   (and AO correction) as possible.

Time-Critical Aspects

• - none

Special Execution Requirements

• ---(Empty)---

Special Calibration Information

• ---(Empty)---

ToO Information

• ---(Empty)---

ToO Activators List

• ---(Empty)---

Is this a Pre-imaging run ?

• false

Pre-imaging Requirements

• ---(Empty)---

Source(s) of Pre-imaging

• ---(Empty)---

Pre-imaging sources not listed above

• ---(Empty)---

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 ?

• 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 ?

• YES

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_ ?

• YES

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