README web version of /home/usg/OPS/MTS/readme_xml/readme_81060901

Principal Investigator Email Address

```
bono@mporzio.astro.it
```

Estimated Total Execution Time (hours, including overheads)

```
7.5
```

General Description

We plan to collect interferometric data with AMBER@VLTI to constrain the
 
binary nature of the nearby Classical Cepheid X Sgr. An accurate FGS@HST 
trigonometric parallax for this object is already available and it is 
used to calibrate the slope of the Period-Luminosity relation for Galactic 
Cepheids. However, it is not clear yet whether X Sgr is a binary, thus 
affecting the precision of its absolute distance. Current measurements 
will help us to investigate the binary nature of the source. If feasible, 
we also plan to use the measurements to provide an accurate estimate of X 
Sgr angular diameter and to derive an accurate estimate of its present mass.
We plan to obtain visibilities on 2 different AT triplets, 1 observation 
on the short baselines (E0-G0-H0) (Run A) and 5 more on the long ones 
(A0-K0-G1) belonging to this run of the programme, thus ending up 
with 6 visibility measurements.

Waiver Requests

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No Waiver Request was submitted
```

Critical Observing Condition Constraints

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none
```

Time-Critical Aspects

We would like to spread the 5 observations over the period.
This observing strategy will allow us to measure the
target visibility at different pulsation phases. Note that the
pulsation period of X Sgr is approximately 7 days. Therefore,
to accomplish the scientific goal the distance between different
observing nights should not be multiples of 7 nights.

Special Execution Requirements

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Special Calibration Information

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ToO Information

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ToO Activators List

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Is this a Pre-imaging run ?

```
false
```

Pre-imaging Requirements

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Source(s) of Pre-imaging

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Pre-imaging sources not listed above

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

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 ?

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 ?

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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 ?

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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
```

Did you indicate for each science star OB the corresponding calibrator star OB (and vice versa) in the 'Instrument Comments' field ?

Did you check that your chosen calibrator is bright enough for the instrument mode used ?

If you use calibrator stars which are not in the CalVin database, did you specify their characteristics in the README file and in the OBs ?

```
N/A
```

Do you use the same DIT for pairs of science target and associated calibrator?

Are the magnitudes of science target and calibrator within +/- 1 mag ?

Did you verify that your coordinates are as accurate as possible (2Mass coordinates recommended) and that they include proper motions if available ?

Did you specify the LST range of the calibrators such that they cover the range from 30 min before the start of the LST range of the science target to 30 min after the end of the LST range of the science target ?

Last creation of page: Tue Oct 6 15:40:24 2009
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