UVITTools

A package for AstroSat/UVIT grating spectroscopy and aperture photometry.

UVITTools.jl is available for Julia 1.9 and later versions, and can be installed with Julia built-in package manager.

julia>]

(@v1.6) pkg> add UVITTools

UVITTools.jl allows FUV/NUV grating spectroscopy and aperture photometry of astronomical sources observed with the Ultra-Violet Imaging Telescope (UVIT) on-board the Indian space observatory AstroSat. The package is compatible with the processed data generated with the CCDLAB pipeline. Check the latest documentation here.

julia> using UVITTools

To find the various tools available, type

julia> ?UVITTools

List of tool to analyze data from the AstroSat/UVIT payload.

• xycen_from_ds9reg: Read x,y centre for DS9 circular region file.
• write_uvit_grating_phafile: Write PHA spectral file for UVIT gratings.
• fuv_grating1_count_spec: Extract 1d count spectrum from FUV-Grating1 image file.
• fuv_grating1_net_countrate_spec: Derive background-corrected net count rate spectrum from FUV-Grating1 image.
• fuv_grating1_pixel2lamA : Convert FUV-Grating1 pixel numbers relative to zero order position into wavelength in Å.
• fuv_grating1_wavelength_calib: Perform wavelength calibration of FUV-Grating1 count sectrum.
• fuv_grating1_flux_calib: Perform flux calibration of FUV-Grating1 wavelength-calibrated count spectrum.
• fuv_grating1_fluxed_spec: Generate wavelength and flux calibrated spectrum from FUV-Grating1 images.
• fuv_grating1_phafile: Generate PHA spectral files from FUV-Grating1 images.
• fuv_grating1_ea : Print FUV-Grating1 effective area.
• fuv_grating2_count_spec : Extract 1d count spectrum from FUV-Grating2 image file.
• fuv_grating2_net_countrate_spec: Derive background-corrected net count rate spectrum from FUV-Grating2 image.
• fuv_grating2_pixel2lamA: Convert FUV-Grating2 pixel numbers relative to zero order position into wavelength in Å.
• fuv_grating2_wavelength_calib: Perform wavelength calibration of FUV-Grating2 count sectrum.
• fuv_grating2_flux_calib: Perform flux calibration of FUV-Grating2 wavelength-calibrated count spectrum.
• fuv_grating2_fluxed_spec: Generate wavelength and flux calibrated spectrum from FUV-Grating2 images.
• fuv_grating2_phafile: Generate PHA spectral files from FUV-Grating2 images.
• fuv_grating2_ea: Print FUV-Grating1 effective area.
• nuv_grating_m1_count_spec: Extract 1d count spectrum from NUV-Grating image file.
• nuv_grating_m1_net_countrate_spec: Derive background-corrected net count rate spectrum from NUV-Grating image.
• nuv_grating_m1_wavelength_calib: Perform wavelength calibration of NUV-Grating count sectrum.
• nuv_grating_m1_flux_calib: Perform flux calibration of NUV-Grating wavelength-calibrated count spectrum.
• nuv_grating_m1_fluxed_spec: Generate wavelength and flux calibrated spectrum from NUV-Grating images.
• nuv_grating_phafile: Generate PHA spectral files from NUV-Grating images.

• read_ds9reg : Read DS9 region file.
• uvit_aphot : Perform aper photometry on UVIT images in any of the broadband filters.
• uvit_countrate2flux: Convert count rate to flux density for any filter.
• uvit_filter2pha: Generate source and PHA spectral files compatible with XSPEC from UVIT images in any of the filters.
• uvit_saturation_corr : Perform saturation correction.
• uvit_zp_uc: Print magnitude zero point and unit conversion factor using Tandon et al. 2020.

• lambdaA2keV : Convert wavelengh in Å to energy in keV.
• lambdaA2ergs : Convert λ in Å to energy in ergs.
• flux_density_photons2cgs : Convert photon flux density n_λ (photons/cm2/s/Å) to energy flux density f_λ (ergs/cm2/s/Å).
• flux_density_cgs2photons : Convert flux density f_λ (ergs/cm2/s/Å) to photon number density n_λ (photons/cm2/s/Å).

To see the help for any tool (e.g., nuv_grating_phafile), type

julia>?
help?> nuv_grating_phafile

UVITTools can perform photometry of individual sources present in FUV or NUV image in any filter. Users will need to create source and background region file using DS9 and input to the photometry tool.

julia> uvit_aphot("NGC4593_FUV_BaF2___MASTER.fits","src.reg","bgd.reg",satu_corr=true)
---------count rates, flux and magnitude------------
Detector: FUV
Filter: BaF2
Exposure time: 17129.3 seconds
source+background rate = 4.2 ± 0.016 counts/s
background rate = 0.0511 ± 0.0004 counts/s
net source count rate = 4.149 ± 0.016 counts/s
Saturation corrected net source count rate= 4.452 ± 0.016 counts/s
Saturation corrected f_λ [BaF2]= 1.591e-14 ± 1.6e-16 ergs/cm2/s/A
Saturation corrected  magnitude[BaF2] (AB system) = 16.15 ± 0.011
------------------------------------------------------
Mean BJD: 2.457588076583e6
------------------------------------------------------
(2.457588076583e6, 4.451869565968372, 0.016218003910273074)

julia> uvit_filter2pha("ngc4593","NGC4593_FUV_BaF2___MASTER.fits","src.reg","bgd.reg")
---------count rates------------
Detector: FUV
Filter: F2
Exposure time: 17129.3 seconds
source+background rate = 4.2+/-0.0157 counts/s
background rate = 0.051+/-0.0004 counts/s
net source count rate = 4.149+/-0.0157 counts/s
Saturation corrected net source count rate= 4.452 ± 0.016 counts/s
--------------------------------
---Writing PHA file-----
Dict{String, Vector}("GROUPING" => Int16[1], "COUNTS" => [77132.30772409608], "CHANNEL" => Int32[1], "QUALITY" => Int16[0])
Dict{String, Vector}("GROUPING" => Int16[1], "COUNTS" => [874.8137822323066], "CHANNEL" => Int32[1], "QUALITY" => Int16[0])
("ngc4593_G05_219T01_9000000_FUV_F2_spec_src.pha", "ngc4593_G05_219T01_9000000_FUV_F2_spec_bgd.pha")

To extract fluxed spectrum in the -2 order of FUV-Grating1, type

 julia> (lam, flam, err_flam) = fuv_grating1_fluxed_spec("ngc40", "NGC40_FUV_Grating1_IMAGE.fits","src.reg","bgd.reg", order=-2, cross_disp_width_pixels = 40, angle_xaxis_disp_deg=0.0)
-----------------------------------
target=ngc40
UVIT channel=FUV
Grating=Grating1
OBS_ID=C02_010T01_9000000
order=-2
Exposure time=1194.007 seconds
---------------------------------------
Wrote spectral ascii file: ngc40_C02_010T01_9000000_FUV_Grating1m2_crossdisp_50pixels_spec.dat

([1196.1544204935722, 1198.9454527675634, 1201.7364850415547, 1204.527517315546, 1207.3185495895373, 1210.1095818635285, 1212.9006141375198, 1215.691646411511, 1218.4826786855024, 1221.2737109594932  …  1773.898101209758, 1776.6891334837492, 1779.4801657577405, 1782.2711980317317, 1785.062230305723, 1787.8532625797143, 1790.6442948537056, 1793.4353271276968, 1796.2263594016881, 1799.0173916756794], [5.045466629574188e-13, 4.3150185620641407e-13, 3.20002438057737e-13, 2.1473337940718712e-13, 3.1256136935946915e-13, 3.309620601584206e-13, 2.330335115352435e-13, 2.8446859045530054e-13, 2.969928077009422e-13, 1.8559317187843672e-13  …  4.78007919733574e-13, 4.1855639102711703e-13, 6.104105792024475e-13, 5.793213715591102e-13, 5.984233168019304e-13, 6.895818454682478e-13, 6.118620245824862e-13, 7.615785936600397e-13, 8.907679878495615e-13, 7.61419751498956e-13], [1.0267947190347392e-13, 8.637264104461592e-14, 6.972295297643998e-14, 5.840516168789386e-14, 5.6833639705142054e-14, 5.42522362473877e-14, 4.587473745925019e-14, 4.4072190863771767e-14, 4.2681889008873683e-14, 3.599499296873876e-14  …  5.96764312139293e-14, 6.233276080702569e-14, 7.279889935967496e-14, 7.101598452391445e-14, 7.784002780312587e-14, 8.738266189464572e-14, 8.352764933553134e-14, 1.0110334674900172e-13, 1.1547586393436977e-13, 1.0992802034895543e-13])

To plot the spectrum,

julia> plot(lam,flam,yerr=err_flam)

To extract XSPEC-style PHA spectral files, type

julia> fuv_grating1_phafile("ngc40", "NGC40_FUV_Grating1_IMAGE.fits","src.reg","bgd.reg", order=-2, cross_disp_width_pixel = 40, angle_xaxis_disp_deg=0.0)
-----------------------------------
target=ngc40
UVIT channel=FUV
Grating=Grating1
OBS_ID=C02_010T01_9000000
order=-2
Exposure time=1194.007 seconds
---------------------------------------
Writing source and background PHA files..
Using /soft/astrosat/responses/uvit/fuv_grating1_m2_4oct19.rmf
("ngc40_C02_010T01_9000000_FUV_Grating1_m2_spec_src.pha", "ngc40_C02_010T01_9000000_FUV_Grating1_m2_spec_bgd.pha")

The UVITTools.jl package is licensed under the MIT License. The original author is Gulab Chand Dewangan (IUCAA, Pune).