Skip to content

combine_spectra_arithmetic

Add, subtract, multiply or divide ctx.spectrum by a reference.
Category Transforms
Backend numpy - implemented here on top of numpy primitives
Version 1.0.1
Reads ctx.spectrum (a Spectrum1D)
Writes spectrum

operation ∈ {add, sub, mul, div}. For 'div', samples where |reference| < min_denominator become NaN (clamp on near-zero responses). Pass-through outside the reference domain matches IRAF sarith and prevents wing zero-out.

Parameters

Parameter Default Required Description
operation 'div' - One of 'add', 'sub', 'mul', 'div'.
min_denominator 5e-05 - Division samples with |reference| below this become NaN. Ignored for non-div operations.
reference_path None - Path / URL of a FITS reference spectrum (loaded with read_fits).
reference_key 'reference_spectrum' - ctx.extras key holding a Spectrum1D reference.

Use it

from spectro_kernel import run_algorithm

output = run_algorithm("combine_spectra_arithmetic", ctx, {
    "operation": "div",
    "min_denominator": 5e-05,
    "reference_path": None,
    "reference_key": "reference_spectrum"
})

spectro run combine_spectra_arithmetic --input spectrum.fits \
  --param operation=div \
  --param min_denominator=5e-05 \
  --param reference_path=none \
  --param reference_key=reference_spectrum

{
  "tool": "combine_spectra_arithmetic",
  "arguments": {
    "session_id": "<session_id>",
    "params": {
      "operation": "div",
      "min_denominator": 5e-05,
      "reference_path": null,
      "reference_key": "reference_spectrum"
    }
  }
}

Every algorithm is an MCP tool of the same name; describe_algorithm returns this page's metadata as JSON.

References

  • Tody 1986, Proc. SPIE 627, 733 — IRAF sarith heritage.
  • Robitaille et al. 2013, A&A 558, A33 — specutils Spectrum1D arithmetic.
  • clip_sigma - Remove outlier samples (cosmic rays, hot pixels) by iterative sigma clipping.
  • extract_region - Crop a spectrum to the wavelength window [wavelength_min, wavelength_max].
  • mask_range - Flag every sample inside a wavelength window as masked.