README web version of /home/usg/OPS/MTS/readme_xml/readme_78026900

Principal Investigator Email Address

• grise@astro.u-strasbg.fr

Estimated Total Execution Time (hours, including overheads)

• 16.7

General Description

• This observation aims at studying spectroscopic variations in the optical
   counterpart of the ULX NGC1313 X-2. This can best be studied by observing the high
   excitation HeII4686 line. We are confident that we can for the first time put constraints
   on the mass of the putative black hole in any of these system.
  
  Previous VLT observations of the target during period 72 allow us to be very specific
   about the setup and to avoid problems experienced during the previous run.
  
  The optical counterpart is one of the components of a close optical binary with
   a separation of 0.7". In previous observations, the slit was centered on one or
   the other component which implied large corrections of the measured radial velocity.
   A crucial point for the current observation is therefore to have the counterpart
   well centered in the slit.
  As shown in the finding chart, the target is the north western component of the
   close double star. The two stars are nearly equally bright in the visual to red
   passbands whereas the counterpart is much brighter in the B band. The brightness
   of the counterpart is B~23.3 which implies that the observation must be carried
   out during dark time (moon below the horizon). 
  
  Some observations during period 72 were carried out in moonlit sky and are therefore
   unfortunately completely useless.
  The 10 spectroscopic observations should be carried out during 2 subsequent new
   moon periods in order to cover possible orbital periods up to about ten days. Intervals
   between subsequent nights should be between one and three days.
  
  The standard configuration will be LSS Grism 300V+10 with no filter and slit width
   of 0.7", slit orientation East-West (rotator = -90deg).
  For two observations, we will use different slit orientations in order to cover
   different parts of the nebula around the ULX and a nearby HII region.
  Two observations, one in each of the two new moon periods, will be carried out with
   grating 600B+12 (no filter, same slit width, orientation east-west). This will be
   crucial to resolve the 4686 emission line.
  
  We were also granted 10 photometric observations (programme 078.D-0269(B)) of NGC1313
   X-2.
  For scientific but also practical reasons (saving of slew time), we request that
   each of the photometric observation should be carried out directly before or after
   the spectroscopic observation.
  
  The finding chart we have marked the reference star and the target. The coordinates
   are as follows :
  - Target : 03:18:22.240 ; -66:36:03.44 (J2000)
  - Ref : 03:18:20.929 ; -66:36:03.86    (J2000)
  
  The offset (Target - Ref) is therefore :
       d(alpha) = +7".81 ; d(delta) = + 0".42

Waiver Requests

• Waiver granted by Palle Moller concerning the exposure time of the OBs
   which exceed 1 hour.
  
  WaiverID:  078.D-0269A.01

Critical Observing Condition Constraints

• The constraints are mainly time-critical and are therefore in the corresponding
   section.

Time-Critical Aspects

• In order to cover possible orbital periods of the target up to some 10
   days, we request that the 10 observations should be carried out during two subsequent
   new moon periods with 5 observations each.
  In order not to set too severe time constraints, subsequent observations could be
   done with time intervals from one to three days in any given new moon period.
  
  In case of bad sky conditions during one new moon period, the second set of observations
   could also be postponed one or two months. This will be less than optimal, but will
   still render scientifically important results.

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 ?

• 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 ?

• 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 prepared your finding charts with tools other than FIMS,
 do they comply with the specifications on the FORS1 Phase 2 web page ?

• N/A