XMM-Newton Phase II RPS Users Manual

5.2.3 Observation details page

This is the top-level page for each observation within a proposal (i.e., in almost all cases, the top-level page for observations of one particular target), see Figs. 8 and 9.

When opening a proposal for the first time, it contains already the observations that the OTAC assigned to the successful PI. In the proposal details page only the first ten parameters are defined already with the information provided in Phase I. For technical reasons dummy values are given to the fields ''Source Unabsorbed X-Ray Flux (ergs cm$^{-2}$s$^{-1}$): 9.000e+00'' and ''Hydrogen Column Density (atoms cm$^{-2}$): 1.0000e+30''. These values have to be changed by the user to representative values to allow a successful ''committing'' of the page. At this level, the following information is required (all fields marked with an asterisk are mandatory).

Figure 8: Screen shot of an ''Observation'' page (top part).

• Target Name

  Please use the most commonly used name of the target (max. 20 characters). The first eight characters will be used in the navigation tool (left frame) as the identifier of the observation.

• Nominal Target Type

  This ''HEASARC Object Classification'' parameter is used to select objects according to their classifications. Clicking on the title ''Nominal Target Type'' in the form will open a separate window displaying the list of ''Object Classes'', also listed below.

  Each object is assigned a four digit numeric code to represent its object classification. The first digit describes the global classification (e.g., AGN or star). The following digits assign further classifications or properties, such as, spectral or AGN type. Each sub-class is chosen to contain a unique set of properties. For example, all normal (non-degenerate) stars have the first digit set to 2. The second digit for stars indicates the spectral type (O, B, etc.), the third digit the numerical sub-type, and the last digit the luminosity class; thus, a G5V star will have the class code of 2555. All stars later (cooler) than F0 have a ''class'' number between 2400 and 2999. As another example, all AGN have class codes that lie between 7000 and 7999; a search by class for AGN would thus be made by doing a search of the class parameter with the range set from 7000 to 7999.

  It should be emphasized that the class assignments of the same source found in different databases may not always be identical and, for any given database, the class codes may not always be present, correct, or complete: see the database help for the particular database in question to determine how the class codes were constructed. ALWAYS USE THE CLASS CODES WITH THESE CAVEATS IN MIND.

  Table with Object Classes.

• Observation Type

  Depending on the proposal type specified above, the type of observation intended must be filled in here. In case of a normal GO proposal, the choice is between ''Fixed'' or ''Non-fixed'', referring to the time of the planned observation. An observation is ''Fixed'' if it must be carried out (due to the object's properties or a certain required constellation) at a specific date and time, or at predefined intervals. More details on which entries are required for fixed observations follow in § 5.2.3.2. Observations without time constraints are ''Non-fixed''. Note, that the above refers only to scientific constraints, and not to the constraints imposed by the target visibility. Therefore, an observation of a target that is visible only during part of the AO observing period is NOT fixed.

• Coordinated Observation

  If your XMM-Newton observation should be coordinated with observations of other instruments (e.g. Chandra, NuSTAR, HST, VLT etc.) you should indicate this here by changing the flag from ''No'' to ''Yes''.

• Right Ascension and Declination (J2000)

  All coordinate entries MUST be made in the J2000 equinox, in the ''hh mm ss.ss'' format for right ascension hours, minutes and seconds (valid input range is from 00 00 00.00 to 23 59 59.99) and in the ''[sign]dd mm ss.s'' format for declination in degrees, minutes and seconds of arc (valid input range is from -89 59 59.9 to 89 59 59.9).

• Total Observation Duration (sec)

  The total proposed duration of the observation, including all exposures, in seconds. This time is the net science integration time plus the instrument overhead times and eventual offset times between exposures. These overhead times will be calculated when doing the ''Check Proposal''. The maximum allowed value for the observation duration is 124000s due to the characteristic of the XMM-Newton orbit. The minimum value for XMM-Newton observations, in order to keep the observatory efficiency high, is 6500s. In fact, the definition of the minimum is related to the effective net exposure time which should not be less than 5000s. Depending on the prime instrument chosen (EPIC or RGS) overhead times can vary a lot.

  Users requiring a total integration time of more than 124000s (which is the approximate maximal continuous visibility for XMM-Newton of any point on the sky) for an observation are requested to split their programs into as many individual observations, of up to 124000s each, as needed to reach the required total integration time.

  Users also have to check the visibility of their targets using the XMM-Newton Target Visibility Tool. Observations longer than the available maximum visibility will not pass the ''Technical Evaluation''. It might be necessary to split the observations in smaller pieces which can be accomodated in different revolutions.

  It should also be taken into consideration that targets with limited visibility are normally visible only at the beginning or at the end of a revolution. This means that, depending on the conditions in the radiation belts, useful visibility might be shortened by up to 10000s.

  XRPS will calculate the sum of all exposure, including overhead and offset times for all XMM-Newton instruments per observation of a given proposal (see § 5.2.4.1 for more details on ''Exposure Offset'' times). This time will be compared to the total observation duration. If the sum is higher than the observation duration, XRPS will raise an error. If the sum for the X-ray instruments is lower than 97% of the total observation duration, another error message is issued. In both cases the exposure times have to be corrected. For OM observations only the maximum limit gives an error, while exposure times lower than 97% of the total observation time just issue a warning message. The reason for this is that in those case where an optically bright source is present in the OM FOV, no OM exposure should be included. The SOC will use this time to perform OM calibrations with the Filter Wheel in the ''Blocked'' position.

• Alternative Names

  Other object names, if any (max. 80 characters).

• Boresight RA and DEC (J2000)

  The coordinates defining the direction in which XMM-Newton will actually be pointing. The requested boresight coordinates can differ from the target's centre coordinates, e.g., in case of extended targets if the observer wants to point to an off-centre position within the extended target (for which still the centre coordinates should be entered as indicated above under the Right Ascension and Declination (J2000) fields).

  The boresight coordinates input fields may be left empty. If so, the target coordinates will automatically be propagated when hitting the commit button. The format is the same as the one used for the target coordinates input in the fields above. Please note that when the target coordinates are changed again AFTER first committing them to memory, the boresight fields are also updated again.

  It should always be kept in mind that when pointing off-axis, the calibration of the RGS may not be optimal due to shifts in the wavelength scale as a function of source position. For off-axis angles of $\geq 2'$ (in the RGS's cross-dispersion direction) the spectrum of a source will not fall on the RGS chips. See also the comments below regarding the choice of prime instrument.

  Note that also the OM standard configurations are optimised for on-axis targets.

• Prime Instrument

  The definition of the prime instrument serves to define the main scientific instrument of the proposal and to stablish whether the observation as a whole is considered as successful or flagged as failed. This last point is based on the total time of the exposures carried out with the prime instrument. The details about the success and failure criteria, and an eventual compensatory observing time for failed observations, are described in the Policies and Procedures document. See also the XMM-Newton Users Handbook chapter on instrument alignment for details.

  In the current AO users can select either EPIC or RGS as prime instrument. Users with a strong interest in RGS dispersive spectroscopy should declare RGS as the prime instrument. OM cannot be chosen as prime instrument.

• Inclusive Position Angle Constraint (deg)

  There are cases, like crowded fields or bright sources in the vicinity of the science target, where users will want to avoid other sources in the FOV, in particular during dispersive spectroscopic observations. Therefore, observers must make sure that nearby sources do not interfere with the science target's spectrum by being located along the dispersion direction of the RGS.

  Note: The XMM-Newton Target Visibility Tool can be used to determine the range of permitted position angles (PAs) for a given source and for each revolution. The user is allowed to specify up to four different PA ranges between 0 and 360 degrees.

Figure 9: Screen shot of an ''Observation'' page (bottom part).

The following entries are requested by the SOC to assist the XMM-Newton user support astronomers in conducting feasibility studies for the execution of the proposed programme.

• Source Extend (deg) of the X-ray emission as specified below

  Indicates the extent of the source's X-ray emission, if extended at all, in units of degrees; if the extension is not circular in shape, please enter a mean value. This is used to estimate count rates and to see whether an extended source will fit into the FOV. The allowed input range is from 0.0 to 20.0 degrees. A value of 0 degrees must be entered for point-like sources.

• Variable Source

  Knowing the variable status of the source will help during the technical feasibility studies, as well as to determine if observed varying count rates during data taking are due to the source or nor. Allowed inputs: True / False

  Please specify Variable Source: ''True'', if the source flux in the XMM-Newton energy band (0.1-15.0 keV) is expected to vary by a factor of 2 or more (during the observation), on the basis of known source characteristics. If photon pile-up is a concern, users should orient their pile-up calculations for variable sources at the UPPER end of the expected flux range. If unsure about the source variability, leave the flag at its default value (''False'').

• Source Unabsorbed X-ray Flux (erg s$^{-1}$ cm$^{-2}$)

  In units of erg s$^{-1}$ cm$^{-2}$, over the passband to be defined below. Entries can be made as $1.5e-13$ for $1.5\times 10^{-13}$ [erg s$^{-1}$ cm$^{-2}$]. For count rate conversion from previous satellite missions and flux-to-count-rate conversions, the usage of the PIMMS software is recommended.

  If the source extent should exceed $30'$ (diameter), please provide the flux within a $30'$ region, centred on the boresight coordinates. The allowed input range is from $0.0$ to $1.0\times10^{-7}$ erg s$^{-1}$ cm$^{-2}$.

• Lower Flux Band Limit (keV) and Upper Flux Band Limit (keV)

  Energy range over which the above X-ray source flux has been determined. The allowed input range for the ''Lower Flux Band Limit'' is from 0.1 to 10.0 keV and for the ''Upper Flux Band Limit'' is from 1.0 to 15.0 keV. Of course, the ''Lower Flux Band Limit'' must be smaller than the ''Upper Flux Band Limit''.

• X-ray Spectral Model

  X-ray spectral model approximating the source spectrum in the energy range from 0.1 to 15.0 keV (the XMM-Newton passband); the options are,

  • Black Body
  • Power Law
  • Thermal Bremsstrahlung
  • Raymond-Smith

  Even if you are not entirely happy with any of these models, choose one and set the parameters in such a way, that the resulting count rate equals more or less the count rate calculated with your model in the energy range you are most interested in.

• Determining Model Parameter (kT or $\Gamma$)

  Depending on the above X-ray spectral model, enter here the best-fitting value of the characteristic parameter, i.e.,

  • kT (keV) for ''Black Body'' allowed input range from 0.01 to 30.0 keV,
  • $\Gamma$ photon index for power laws (following the convention $F_{\mbox{\scriptsize photon}} \propto E^{-\Gamma}$), allowed input range from -15.0 to 15.0
  • kT (keV) for ''Thermal Bremsstrahlung'' allowed input range from 0.05 to 30.0 keV,
  • kT (keV) for ''Raymond-Smith'' allowed input range from 0.1 to 28.0 keV.

• Hydrogen Column Density (atoms cm$^{-2}$)

  Absorbing column density, in units of cm$^{-2}$; if known, please provide a fit result from existing X-ray data. For extragalactic sources with either negligible or highly inhomogeneous internal absorption, please provide the value for the Galactic foreground absorption. Exponential notation must be used, e.g.: $3.78e20$ for $3.78\times10^{20} cm^{-2}$. The allowed input range is from 0.0 to $1.0\times10^{25} cm^{-2}$.

• Target Optical Spectral Type (O, B, A, F, G, K, M, Rn, Nn, Sn; 0-9)

  Spectral type of the target. This information (together with the Target Visible Magnitude below) is used to estimate the optical loading in the EPIC cameras. In the case of extragalactic objects, the user must select the spectral type that best reproduces the optical spectrum of the target. The allowed spectral types are O, B, A, F, G, K, M, Rn, Nn, Sn with subclasses from 0 to 9.

• Target Visible Magnitude

  Johnson V magnitude of target, if known (or best guess of upper brightness limit). For extended targets, e.g. galaxies, please provide maximum surface brightness, in units of V magnitudes per square arcsec. The allowed input range is from 0.00 to 30.0 mag.

• SOC Enhance Request

  In case of doubt about the optimal observation setup, users can request SOC assistance for optimising an observing programme. However, please read § 7 before filling in this field.

Finally, use the commit button to enter the information into memory.

By now, the navigation tool (§ 4.5) in the left hand window should show one file per Investigator, with the PI in first place, followed by a directory which has just been created for entries regarding the first observation of the proposal (cf. Fig. 5).