Description Usage Arguments Details Value Author(s) References Examples

Create a 1-d convolution kernel to broaden a spectrum from a rotating star

1 | ```
lsf_rotate(deltav, vsini, epsilon=0.6)
``` |

`deltav` |
step increment in the output rotation kernel, scalar, in km/s |

`vsini` |
rotational velocity projected along the line of sight, scalar, in km/s |

`epsilon` |
limb-darkening coefficient, scalar (default = 0.6) |

This function can be used to derive the broadening effect, or line spread function (LSF),
due to stellar rotation on a synthetic stellar spectrum. It assumes constant limb darkening across the disk. To actually compute the broadening. the spectrum should be convolved with the rotational LSF using a function like *kernapply* or *filter*.

The number of points in the output *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).

The limb darkening coefficient *epsilon* = 0.6 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

1 |

.

The algorithm is adapted from rotin3.f in the SYNSPEC software of Hubeny & Lanz http://nova.astro.umd.edu/. Also see Eq. 17.12 in Gray (1992).

`lsf` |
convolution kernel vector for the specified rotational velocity |

Written by W. Landsman 2001

R adaptation by Arnab Chakraborty June 2013

Gray, D., 1992, "The Observation and Analysis of Stellar Photospheres"

1 2 3 4 | ```
# 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
lsf = lsf_rotate(3,90) # LSF will contain 61 pts
``` |

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