README web version of /home/usg/OPS/MTS/readme_xml/readme_80063100
Principal Investigator Email Address
Estimated Total Execution Time (hours, including overheads)
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~23.4 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 16 spectroscopic observations should be carried out randomly. The standard configuration
will be LSS Grism 300V+10 with no filter and slit width of 1.0", 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 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 080.D-0631(B))
of NGC1313 X-2. For scientific reasons, it would be better if the photometric observation
could be carried out directly before or after a spectroscopic observation. Nevertheless,
it is not a strict constraint as we know that it decreases the scheduling possibilities
of the VLT. The finding chart we have marked the reference star and the target.
The coordinates are as follows : The offset (Target - Ref) is therefore :
d(alpha) = +7".81 ; d(delta) = + 0".42
Waiver Requests
Critical Observing Condition Constraints
Time-Critical Aspects
Special Execution Requirements
Special Calibration Information
ToO Information
ToO Activators List
Is this a Pre-imaging run ?
Pre-imaging Requirements
Source(s) of Pre-imaging
Pre-imaging sources not listed above
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 ?
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 ?
Have you included OBs for any calibrations that you need but which are
not part of the Calibration Plan ?
If you are observing Moving Targets, have you attached suitable ephemeris
files to your OBs?
If you have preferences which OBs should be executed first, did you make
use of the User Priority field in the OBs ?
If this is a run that requires coordinated observations with other facilities,
did you give proper instructions in the Time-Critical Aspects Section ?
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 ?
Last creation of page: Tue Oct 6 15:40:22 2009
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