Flux Correction
The 3_Flux_Correction.py script requires the spectrum of a standard star you observed, as well as the internal calibration
files in IRAF. The functions are used to create a sensitivity function from the standard star spectrum, and then apply that
sensitivity function to the science targets.
Create Sensitivity File
The first step is to create a sensitivity file, which is a file that contains the sensitivity of the instrument as a function
of wavelength derived from the standard star spectrum. The create_standard_sensfunc function takes in the name of the
standard in your current directory, the name of that standard in the IRAF database, and the name of the directory database
where the calibration files are stored.
create_standard_sens('LTT3218' , 'LTT3218' , 'l3218', iraf_directory = 'ctionewcal')
Warning
I have coded this up in a terrible way that requires you to manually specify the location of
the IRAF database since this was the least crashy option for IRAF. See the commented out lines
in the standard function for some common options. Modify the extinction and caldir
variables to match your setup.
This function will display an interactive window from where you can adjust which regions to use for the flux calibration. In general, you want to remove anything not related to the star, which usually only involves removing telluric absorption regions. You can remove boxes by clicking d while having the red cross-hairs on top of the box you want to delete.
Sensitivity function derived from the standard star spectrum. The individual boxes represent the regions used for the fit.
If everything looks good, press q to quit and go to the next step. The next plot shows the best fit to the sensitivity
function. In here you can adjust the order of the fit by typing : which will launch a prompt window where you can change
the parameters of the fit. Press Enter to implement the changes. You can also delete points with the d key and undelete
them with the u key. Generally, you want the edges of the sensitivity function to not explode to large values.
Best fit to the sensitivity function.
If everything looks good, press q to quit and save the sensitivity function.
Flux Calibration
The next step is to flux calibrate the science targets. The iraf_standard function takes in the name of the object
you want to flux calibrate, as well as the name of the sensitivity function you just created. An example shown below.
iraf_standard('AT2022xzc', 'AT2022xzc', 'sens_l3218.fits')
There is not much to do with this function, other than making sure the WARNING that shwos how many pixels were outside the sensitivity function is not too large. If it is, you may need a different standard or calibration directory.
How to Pick a Standard
In the example shown here we have already selected the LTT3218 standard star with a name of l3218 in the
calibration directory ctionewcal. First, you need to make sure your standard star is one in the IRAF database.
Then, you need to find the name of your star in the calibration directory. Finally, you need to choose which directory
has the best calibration file for your standard. Generally, you want to pick one with the best wavelength coverage.
A list of all the standard stars found in IRAF and their corresponding calibration directories is shown below.
Standard stars in onedstds$bstdscal/
hr718 hr3454 hr3982 hr4468 hr4534
hr5191 hr5511 hr7001 hr7596 hr7950
hr8634 hr9087 hd15318 hd74280 hd100889
hd188350 hd198001 hd214923 hd224926
--------------------------------------------------------------------------------
Standard stars in onedstds$ctiocal/
bd25 eg139 feige56 l2415 l93080
bd73632 eg149 feige98 l2511 l97030
bd8 eg158 g16350 l3218 lds235
cd32 eg248 g2631 l3864 lds749
eg11 eg274 g9937 l4364 ltt4099
eg21 f15 h600 l4816 ltt8702
eg26 f25 hz2 l6248 ross627
eg31 f56 hz4 l7379 w1346
eg54 f98 hz15 l7987 w485a
eg63 f110 kopf27 l8702 wolf1346
eg76 feige110 l377 l9239 wolf485a
eg79 feige15 l1020 l9491
eg99 feige25 l1788 l74546
--------------------------------------------------------------------------------
Standard stars in onedstds$ctionewcal/:
Combined red and blue 3300A-10000A:
cd32 f56 l2415 l4364 l7987
eg21 h600 l3218 l4816 l9239
eg274 l1020 l377 l6248 l9491
f110 l1788 l3864 l7379 l745
Blue 3300A-7550A:
cd32blue f56blue l2415blue l4364blue l7987blue
eg21blue h600blue l3218blue l4816blue l9239blue
eg274blue l1020blue l377blue l6248blue l9491blue
f110blue l1788blue l3864blue l7379blue
Red 6050A-10000A:
cd32red f56red l2415red l4364red l7987red
eg21red h600red l3218red l4816red l9239red
eg274red l1020red l377red l6248red l9491red
f110red l1788red l3864red l7379red l745red
--------------------------------------------------------------------------------
Standard stars in onedstds$iidscal/
40erib eg50 eg149 g16350 hz4 lds235b
amcvn eg54 eg158 g191b2b hz7 lds749b
bd253941 eg63 eg162 g2610 hz14 lft1655
bd284211 eg67 eg182 g2631 hz15 lp414101
bd332642 eg71 eg184 g4718 hz29 ltt13002
bd404032 eg76 eg193 g88 hz43 ltt16294
bd73632 eg77 eg247 g9937 hz44 ltt4099
bd7781 eg79 eg248 gd128 kopff27 ltt8702
bd82015 eg91 feige15 gd140 l13633 ross627
eg11 eg98 feige24 gd190 l140349 ross640
eg20 eg99 feige25 gh7112 l14094 sa29130
eg26 eg102 feige34 grw705824 l151234b sao131065
eg28 eg119 feige56 grw708247 l74546a ton573
eg29 eg129 feige92 grw738031 l8702 wolf1346
eg31 eg139 feige98 he3 l93080 wolf485a
eg33 eg144 feige110 hiltner102 l97030
eg39 eg145 g12627 hiltner600 lb1240
eg42 eg148 g14563 hz2 lb227
--------------------------------------------------------------------------------
Standard stars in onedstds$irscal/
bd082015 eg50 feige34 hd117880 hd60778 hr7001
bd174708 eg71 feige56 hd161817 hd74721 hz44
bd253941 eg139 feige92 hd17520 hd84937 kopff27
bd262606 eg158 feige98 hd192281 hd86986 wolf1346
bd284211 eg247 feige110 hd19445 he3
bd332642 feige15 g191b2b hd217086 hiltner102
bd404032 feige25 hd109995 hd2857 hiltner600
--------------------------------------------------------------------------------
Standard stars in onedstds$oke1990/
bd284211 feige110 feige67 g191b2b g249 gd248 ltt9491 eg71
bd75325 feige34 g13831 g19374 gd108 hz21 eg158 eg247
--------------------------------------------------------------------------------
Standard stars in onedstds$redcal/
40erib eg63 eg139 eg248 gd140 hz44 ltt16294
amcvn eg67 eg144 feige24 gd190 l13633 ltt4099
bd7781 eg76 eg145 g12627 grw705824 l14094 ltt8702
bd73632 eg79 eg148 g14563 grw708247 l151234b ross627
bd174708 eg91 eg149 g16350 grw738031 l74546a ross640
bd262606 eg98 eg162 g191b2b hd19445 l93080 sa29130
eg20 eg99 eg182 g2610 hd84937 l97030 sao131065
eg33 eg102 eg184 g2631 he3 lds235b wolf1346
eg50 eg119 eg193 g4718 hz29 lds749b wolf485a
eg54 eg129 eg247 g9937 hz43 lft1655
--------------------------------------------------------------------------------
Standard stars in onedstds$spec16cal/:
Combined red and blue 3300A-10300A:
hd15318 hd74280 hd114330 hd188350 hd214923
hd30739 hd100889 hd129956 hd198001 hd224926
hr1544 hr4468 hr5501 hr7596 hr8634
hr3454 hr4963 hr718 hr7950 hr9087
Blue 3300A-7550A:
hd15318blue hd74280blue hd114330blue hd188350blue hd214923blue
hd30739blue hd100889blue hd129956blue hd198001blue hd224926blue
hr1544blue hr4468blue hr5501blue hr7596blue hr8634blue
hr3454blue hr4963blue hr718blue hr7950blue hr9087blue
Red 6020A-10300A:
hd15318red hd74280red hd114330red hd188350red hd214923red
hd30739red hd100889red hd129956red hd198001red hd224926red
hr1544red hr4468red hr5501red hr7596red hr8634red
hr3454red hr4963red hr718red hr7950red hr9087red
--------------------------------------------------------------------------------
Standard stars in onedstds$spec50cal/ (3200A - 8100 A)
bd284211 eg247 feige34 hd192281 pg0205134 pg0934554 wolf1346
cygob2no9 eg42 feige66 hd217086 pg0216032 pg0939262
eg139 eg71 feige67 hilt600 pg0310149 pg1121145
eg158 eg81 g191b2b hz14 pg0823546 pg1545035
eg20 feige110 gd140 hz44 pg0846249 pg1708602
Standard stars in onedstds$spec50cal/ (3200A - 10200A)
bd284211 eg247 feige34 g191b2b hz44
eg139 eg71 feige66 gd140 pg0823546
eg158 feige110 feige67 hilt600 wolf1346
--------------------------------------------------------------------------------
Standard stars in onedstds$spechayescal/
bd284211 eg139 feige67 hd217086 pg0216032 pg0939262
cygob2no9 eg158 feige110 hiltner600 pg0310149 pg1121145
eg42 eg247 g191b2b hz14 pg0823546 pg1545035
eg71 feige34 gd140 hz44 pg0846249 pg1708602
eg81 feige66 hd192281 pg0205134 pg0934554 wolf1346
Once you have completed the flux calibration, you can proceed to the Plot Data tutorial.