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Abteilung Astronomie

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LSF_ROTATE: Source code in lsf_rotate.pro

LSF_ROTATE:

Name
     LSF_ROTATE:
Purpose
     Create a 1-d convolution kernel to broaden a spectrum from a rotating star
Explanation
     Can be used to derive the broadening effect (line spread function; LSF)
     due to  rotation on a synthetic stellar spectrum.     Assumes constant
     limb darkening across the disk.
Calling Sequence
     lsf = LSF_ROTATE(deltav, vsini, EPSILON=, VELGRID=)
Input Parameters
    deltaV - numeric scalar giving the step increment (in km/s) in the output
             rotation kernel.
    Vsini - the rotational velocity projected  along the line of sight (km/s)
Output Parameters
    LSF - The convolution kernel vector for the specified rotational velocity.
          The  number of points in LSF will be always be odd (the kernel is
          symmetric) and equal to  either ceil(2*Vsini/deltav) or
          ceil(2*Vsini/deltav) +1 (whichever number is odd).    LSF will
          always be of type FLOAT.
          To actually compute the broadening. the spectrum should be convolved
          with the rotational LSF.
Optional Input Parameters
    Epsilon - numeric scalar giving the limb-darkening coefficient,
          default = 0.6 which is typical for  photospheric lines.    The
          specific intensity I at any angle theta from the specific intensity
          Icen at the center of the disk is given by:
          I = Icen*(1-epsilon*(1-cos(theta))
Optional Output
     Velgrid - Vector with the same number of elements as LSF
Example
    (1) Plot the LSF for a star rotating at 90 km/s in both velocity space and
        for a central wavelength of 4300 A.    Compute the LSF every 3 km/s
       IDL> lsf = lsf_rotate(3,90,velgrid=vel)      ;LSF will contain 61 pts
       IDL> plot,vel,lsf                    ;Plot the LSF in velocity space
       IDL> wgrid = 4300*(1+vel/3e5)       ;Speed of light = 3e5 km/s
       IDL> oplot,wgrid,lsf                ;Plot in wavelength space
Note
    Adapted from rotin3.f in the SYNSPEC software of Hubeny & Lanz
        http://tlusty.gsfc.nasa.gov/index.html.    Also see Eq. 17.12 in
    "The Observation and Analysis of Stellar Photospheres" by D. Gray (1992)
Revision History
    Written,   W. Landsman                November 2001

Last modified by pro2html on 2001 December 19 at 04:22 UTC

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Jörn Wilms (wilms@astro.uni-tuebingen.de)
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