Subsections

• EXOSAT LE UV Contamination
• Pixel conventions
  • EXOSAT CMA
  • Einstein HRI
• QDP/PLT

Miscellaneous

EXOSAT LE UV Contamination

Many observations of hot stars with EXOSAT showed that enough UV radiation leaked through the filters to dominate the X-ray count rate for bright enough UV sources. Although work has not quite finished, one can obtain an estimate good to 50% or so with the program LE_UV. Users will be prompted in turn for any of the following quantities which they do not specify on the command line:

• filter_code : 2=PPL 4=4000 Lexan 6=Al/Par 7=3000 Lexan 8=Boron
• spectral_type : such as O7 or B3 - no account is taken of luminosity class
• V_magnitude : without reddening correction
• E(B-V) : color excess

The calculation is based on a UV calibration of the CMA done by Fritz Paerels with Sirius AB which has been combined with an IUE atlas of spectra of hot stars and Seaton's interstellar reddening law.

Pixel conventions

EXOSAT CMA

• The pixel coordinates are 0,0 in the center of the image.
• The images cover from -1024 to +1024 pixels.
• One pixel is 4 arc seconds.

Einstein HRI

• The pixel coordinates are 0,0 at the bottom left hand corner.
• The images cover from 0 to 2048 pixels.
• One pixel is 1 arc second (the images are rebinned from the original 0.5 arc sec).

QDP/PLT

QDP is an all purpose plotting and function fitting program. It operates on ASCII files which contain both the data and the commands that control the display. It can be used in an interactive mode to adjust the labels, optimize the plot, etc. The QDP package is used in an automatic mode to plot lightcurves and spectra by BROWSE, XSPEC, and XRONOS. In each case a QDP file can be generated and input to QDP. This is extremely useful for post facto plotting and fitting of data. It also allows the user to generate QDP files within the XRAY captive account, transfer them by mail, and then replot and manipulate the files locally. This program comes from the XANADU EXOSAT analysis package at the Institute of Astronomy, Cambridge, UK. It was written and is currently maintained by Allyn Tennant at the Marshall Space Flight Center (SSL::TENNANT). It can be installed on the user's VAX for local use either by the observatory team (contact exosat::frank) or by obtaining a copy from Allyn Tennant directly. UNIX and MS-DOS versions are also available.

Example:

HEASARC> browse le                          ! Browse the EXOSAT LE database
 
LE_SOURCES_DEC > sn 3c382                   ! search for name 3c382
 
LE_SOURCES_NAM 10> sc                       ! search in a cone, in case
                                            ! other names used. The
R.A. (1950  d/f= 18  h 33 m 11.75sec):      ! default RA, Dec and cone angle
Dec  (1950  d/f= 32deg 39 m 17.93sec):      ! are from the first entry found
Radius in arcmin. (d/f=  30.00):            ! in the previous search.
 
LE_SOURCES_DEC 39> sif filter 7             ! take only filter 7 data (thin
                                            ! lexan)
 
LE_SOURCES_DEC 39:24> cpd /te               ! change plot device to
                                            ! Tektronix
 
LE_SOURCES_DEC 39:24> pp/l/plt 39           ! plot the products lightcurve (/l)
                                            ! of the last (the longest) entry.
                                            ! /plt to stay in qdp/plt
 
PLT> wd 3c382                               ! write a qdp file
 
PLT> ex                                     ! exit qdp/plt
 
LE_SOURCES_DEC 39:24> ex                    ! exit BROWSE
 
HEASARC> mail 3c382.qdp                     ! mail the file
HEASARC> lo                                 ! end the session
USERS_VAX> mail                             ! read the mail messages
                                            ! on the user's VAX
You have 3 new messages.
 
MAIL> <CR>
MAIL> extract/nohead 3c382.qdp              ! extract the first message
%MAIL-I-CREATED, USR:[FRED]3C382.QDP;1 created
 
MAIL> exit                                  ! exit mail
USERS_VAX> QDP 3c382                        ! plot the QDP file
                                            ! this could be done on the
                                            ! user
PLT> r y 0.001 10.0                         ! rescale the y axis
PLT> log y                                  ! make the y axis log
PLT> plot                                   ! replot
PLT> hardcopy 3c382.ps                      ! hardcopy
PLT> ex                                     ! exit
USER_VAX> psprint 3c382.ps                  ! print the postscript file
                                            ! (local command may be
                                            ! different)