tilt HEADAS help file

NAME

tilt -- Evaluates the nominal scattered solar X-ray background observed by ROSAT.

USAGE

tilt obs iflag T0 IS01 IS11 IS02 IS12 IS04 IS14 tlog1 scale1 tlog2 scale2

DESCRIPTION

Program TILT uses the methods described in Snowden and Freyberg (1993, ApJ, 404, 403) to evaluate the scattered solar X-ray background contamination using the scale factors fitted by program RATEFIT. There are three parameters which are evaluated: the total number of contaminating counts in each band, the gradient of the counts across the image, and the rotation angle of that gradient. The gradient is assumed to be linear.

The TILT package uses the following input files.

1) Observation ancillary data fits file : xxx_ANC.FITS for RDF data

2) Other fixed input :

valid_times.dat The file valid_times.dat is an ascii file; each line in the file consists of a counter (an integer), begin time, and end time, where the times are given in terms of spacecraft clock time. This must be the same time selection as used with the programs CASTDATA, CASTEXP, CASTPART, and LTE.

3) In addition, TILT reads the following FITS files from the CALDB database: On-axis effective area (EFFAAREA), Window transmission (WTRANS), Gas efficiency (DET_EFF), ROSAT energy grid (ENERGY_GRID), Solar-geophys-data file (SOLAR_GEOPHYS), Detector response matrix (MATRIX) and Raymond and Smith thermal spectra (1991 vintage)(RAYMOND_SPECTRA). The input file SG.DAT contains solar and geophysical data which are required for AO and TILT.

A note about the time offset and scale factors used in TILT:

T0, IS01, IS11, IS02, IS12, IS04, and IS14 are outputs of RATEFIT routine. (IS01 and IS11 are the fitted values for IS0 and IS1 for band R1. Similarly, IS02, IS12, IS04, and IS14 are the fitted values for IS0 and IS1 for bands R2 and R4, respectively.) At this time, TILT ignores band R3. The values IS01 and IS11 are used to scale the values for the R1 or R1L bands, IS02 and IS12 are used to scale the values for the R2 band, while IS04 and IS14 are used to scale the values for the R4 through R7 bands. Bands R4 - R7 are not allowed to vary independently since essentially all the counts originate as oxygen K-alpha emission and so counts in the higher bands are just pulse-height spillover from 0.53 keV. NOTE: Even if the fitted parameters IS0 and IS1 are zero for a given band (R1, R2, or R4), a non-zero value for IS0 must be input for TILT and the results for the given band just ignored. Otherwise, TILT will crash on a divide by zero. The same holds true if certain bands are not being processed. In order to not produce too unreasonable a value for the total number of counts (which is used as an input to the program FITAP) a value for IS0 of 0.1 (to replace an otherwise zero input) is acceptable. (The results of FITAP are not particularly sensitive to the value for the total number of scattered solar X-ray counts, as long as it is at least roughly, order of magnitude, accurate.)

The screen output from the TILT package consists of the following: Contamination parameters - counts, rotation angles, and gradients for each band (except R3).

PARAMETERS

(obs = "OBS") [string]: Observation control (prefix for the filename xxx_ANC.FITS)
(iflag = "1") [integer]: Mode control: IFLAG=1 for simple treatment, 2 for more complete treatment. The simple treatment assumes that the situation is optically thin, the more complete treatment uses a nearly complete radiative transfer approach.
(T0 = "") [integer]: Time offset.
(IS01 = "") [real]: Fitted value for IS0 for band R1.
(IS11 = "") [real]: Fitted value for IS1 for band R1.
(IS02 = "") [real]: Fitted value for IS0 for band R2.
(IS12 = "") [real]: Fitted value for IS1 for band R2.
(IS04 = "") [real]: Fitted value for IS0 for band R4.
(IS14 = "") [real]: Fitted value for IS1 for band R4.
(tlog1 = "6.2") [real]: Temperature for the first solar component - the intrinsic solar X-ray spectrum is modelled as two-component thermal plasma emission, in this case, Raymond and Smith (1977) with the 1991 computer code update. The program requests the log_10 of the temperature and the scale factor for each component. These same temperatures and scale factors must also be used in the program AO for consistency.
(scale1 = "0.8") [real]: The scale factor for the first solar component.
(tlog2 = "5.7") [real]: Temperature for the second component - Scale factors which sum to one for temperatures near log_10 T of near 6 (e.g., 6.2 0.8 and 5.7 0.2) will give model count rates which are typically within a factor of a few to ten of the true values (determined later by the program RATE_FIT).
(scale2 = "0.2") [real]: The scale factor for the second solar component.
(caldbdir = " ") [string]: This should be left blank. If the fixed input FITS files are in a different location than CALDB then the directory structure can be defined using caldbdir. This is mostly for test purposes and should be left unchanged.
(calfexp = "caldb") [string]: Name of calibration information to be used.
(chatter = "9") [string]: Chatter flag level for the output.

EXAMPLES

1. For the input file test_ANC.FITS with input parameters T0=126347396, IS01=19.9, IS11=0.0, IS02=5.65, IS12=0.0, IS04=0.91, IS14=0.0 and (6.2, 0.8) and (5.7, 0.2) as the first and second temperatures and scale factors respectively, assuming simple treatment (iflag=1) the usage is



        ft>  tilt test 1 126347396 19.9 0. 5.65 0. .91 0. 6.3  0.8 5.7 0.2

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