README web version of /home/usg/OPS/MTS/readme_xml/readme_83095800

Principal Investigator Email Address

• claire.martin-zaidi@obs.ujf-grenoble.fr

Estimated Total Execution Time (hours, including overheads)

• 14

General Description

• We propose to observe a sample of young stars with large inner holes in
   their disks, discovered with Spitzer thanks to their characteristic Spectral Energy
   Distributions. These rare objects are very interesting because they have massive
   dust disks beyond 10-20 AU but large inner holes where planets could be currently
   forming at ages between 1 and 10 Myrs. The diffraction-limited VISIR mid-infrared
   imaging will confirm and directly measure the holes, impossible to do accurately
   with unresolved data, and give information about the spatial distribution of different
   dust species (e.g., large grains vs. PAHs). These VISIR observations will be associated
   with UVES spectroscopy observations (run B). The high-resolution UVES optical spectra
   
  will provide detailed information about the stellar parameters and the gas accretion
   through the holes towards the stars. The combination of both diagnostics will provide
   strong support in favor or against the presence of currently forming planets in
   these disks. 
  We selected three filters for VISIR imaging: the Q2 filter at 20 micro m to obtain direct
   evidence for inner holes in disks, and two other filters at shorter wavelengths,
   the PAH2 and PAH2 2 filters, to probe the hotter material and compare the location
   of different dust populations. Since PAHs can easily fill the gap/hole, we choose
   to use one filter on (PAH2) and one filter just off (PAH2 2) the 11.3 micro m PAH feature.
  
  Detailed modeling of the SEDs suggests inner holes from 5 to 50 AU, corresponding
   to angular diameters of 0.04 to 0.36 arcsec at the distance of most objects of the
   sample (150 pc) and of 0.06 to 0.8 arcsec for the targets in closer associations.
   The VISIR observations will have an average FWHM of 0.3 - 0.5 arcsec depending on
   the seeing; thus we selected targets in our sample to have estimated inner holes
   larger than 0.3 arcsec based on their SED. The proposed observations will allow
   us to resolve the holes and hence will provide the first direct evidence for the
   inner holes for most sources in the sample. Furthermore, the combined use of images
   at 20 micro m (large grains) and smaller wavelengths (PAHs) will allow the localization
   of different dust grain populations in the disk holes, with strong implications
   for dust dynamics, and thus planet formation, models. Since several of the cold
   disks do show PAH emission features in their Spitzer IRS spectra, it is important
   to understand their role and location during the clearing of the inner disks.

Waiver Requests

• No Waiver Request was submitted

Critical Observing Condition Constraints

• All the OBs need at least:
  Sky transparency: clear
  Seeing less than 1.0
  any lunar phase
  
  airmass: for most of our target we asked maximum airmass of 1.6
  
  some of our targets never rises above 1.5 airmass. They thus can be observed at
   higher airmass than 1.6.

Time-Critical Aspects

• no time-critical aspects

Special Execution Requirements

• We asked to observe 2 calibrators (PSF) for each science target (one before
   and one after the science exposure). These calibrators are defined in normal OBs.
   The 2 calibrators are in OBs named "CAL_TARGETNAME_1" and "CAL_TARGETNAME_2", where
   "TARGETNAME" is the name of the corresponding science OB. The two calibrators should
   be executed immediately before and after the science OB, so as to ensure that they
   are done under as similar conditions as possible.

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 ?

• 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

If the provided finding chart is at a different wavelength than the observations,
 did you clearly describe in the README file how to identify the target?

• YES

Did you specify a guide star brighter than V=12mag within a field of
 r=5arcmin around the science target?

• NO