% @(#)standairsp.hlq 17.1.1.1 (ESO-IPG) 01/25/02 17:52:53 % @(#) %++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %.COPYRIGHT (c) 1992 European Southern Observatory %.IDENT rectifirsp.hlq %.AUTHOR E.Oliva, Arcetri (Florence) %.KEYWORDS MIDAS, help files, STANDARD/IRSPEC %.PURPOSE On-line help file for the command: STANDARD/IRSPEC %.VERSION 1.0 23-SEP-1992 : Creation, E.Oliva %---------------------------------------------------------------- \se SECTION./IRSPEC \es\co STANDARD/IRSPEC 23-SEP-1992 EO \oc\su STANDARD/IRSPEC in_ascii_file out_table interp_method [degree=degree] [step=wavelength_step] [limits=wl1,wl2] [units=wavelength_units] [plot=plot_option] Create standard star flux table from a "flux ascii file". \us\pu Purpose: To a create a table containing a properly sampled F(lambda) vs. lambda representation of the continuum of a standard star. The user must provide an ascii file with his/her favourite guesses of the star fluxes at a number of wavelengths, e.g. the values of F(lambda) at the effective wavelengths of photometric filters in case of photometric standard stars. The output table is necessary to create the response frames (see RESPONSE/IRSPEC). You are also kindly invited to read the notes below. \up\sy Syntax: STANDARD/IRSPEC in_ascii_file out_table interp_method [degree=degree] [step=wavelength_step] [limits=wl1,wl2] [units=wavelength_units] [plot=plot_option] \ys\pa in_ascii_file = Input, ascii (i.e. "normal") file created by the user and containing his/her best guesses of the star fluxes at a number of wavelengths (see notes below). The file must contain, in each lines, "wavelength" "flux" "any comment you like" and must not contain empty/comment rows; the format and wavelength order is free.\\ Example:\\ 1.25 1.04e3 J=6.12, flux in 1e-11 erg cm-2 s-1 um-1\\ 2.20 196 K=5.73, same units\\ 1.65 4.34e2 H=5.99, same units \ap\pa out_table= Output table containing wavelengths (column :wl) and fluxes (column :flux) interpolated over the input values according to the method defined by the next parameter. The wavelength step and limits of the table are controlled by the "limits=.." and "step=..." options (see below). \ap\pa interp_method = Method for interpolation/fitting of input data. - b black-body fitting - p polynomial fitting, in the log(F) vs. log(wl) plane - s spline interpolation, in the log-log plane The spline method should be used only when you have many points in your input file, for few data it should give the same result as polynomial interpolation.\\ \\ Additional parameters and options \ap\pa degree = degree of the polynomial/spline, default=2 Not used for black body fitting \ap\pa step = In the output table the star flux is sampled at wavelength intervals equal to "step". Default value is 0.01, be careful to properly set this parameter if you are working in Angstroms! \ap\pa limits = The output table will cover the full wavelength range specified by the input ascii files. Use this parameter if you need to restrict the size of the table (e.g. limits=1.1,1.3 or l=1.9,2.4). This does not affect the fitting procedure which always considers all the input data. \ap\pa units = Wavelengths are usually in microns. You can use units=a (or just u=a) if you prefer to work in Angstroms; your ascii file must also contain wavelengths in Angstroms and ... be careful with the step parameter (see above) \ap\pa plot = Plot option, if equal to 1 (the default) the command will plot your input points and the fitted function, Use plot=0 (or p=0) for silent work. \ap\no Note: The ideal standard star should be featurless - to allow a proper cancellation of the telluric, absorption features (remember that you should not smooth the star spectrum in the IR) - and with a precisely known flux distribution. In practice, no such a star exists not only because all stars - even the hottest O types - have some absorption features, but mainly because it is hard to find accurate measurements (at fairly high resolving powers) of the absolute flux distribution of any star. At present (end 1992), there is nothing like a list of spectrophotometric standard stars as you find in the optical. Hence you must choose your reference stars according to your preferences - I personally like early O types though they are rare, little studied and often variable! - and also use your favourite guesses for their absolute fluxes at a number of wavelengths. In practice, you will probably end up using photometric standard stars in which case you can enter, in your ascii file, the values of F(lambda) at the effective wavelengths of the filters; and for the transformation from magnitudes to fluxes you may use e.g. Wilson et al. (1972, ApJ 177, 533) and Bessel (1979, P.A.S.P. 91, 589) or any other reference you like. \\ \\ This command does not extrapolate beyond the wavelength limits given in the input, ascii file. If you have spectra at wavelength shorter than 1.25 micron (the effective wavelength of the J filter) you may find it difficult to estimate the star flux at wavelengths around 1 micron, and you will probably be forced to use the R - or even the V - photometric point. Be aware that interpolating over such a broad range may introduce not negligible errors! \\ \\ You are recommended to use F(lambda) units rather than F(nu). However, you can also use the latter but be aware that the black-body interpolation will not work. \on\exs Examples: \ex STAND/IRSP bs1933.flux bs1933 bb \xe\ex STAND/IRSP hd33312.flux hd33312k poly d=3 p=0 s=.001 l=1.95,2.50 \xe \sxe