Information on Service 'TheoSSA - Theoretical Stellar Spectra Access'

For a list of all services and tables belonging to this service's resource, see Information on resource 'TheoSSA - Theoretical Stellar Spectra Access'

Service Documentation

SSA services are particularly well suited for programmatic access. Here is a sample program using pyVO and astropy to plot a T_eff grid:

from astropy.table import Table
import pyvo
import numpy as np

TEFF_SCALER = 200.


def _wiggle(val):
  """returns a +/- 2% range for the float val in SSAP syntax.
  """
  if val is not None:
    return "%s/%s"%(val*0.98, val*1.02)


def discover_spectra(teff=None, logg=None, **elements):
  """returns a pyvo result for spectra with teff, logg, and given abundances.

  Each argument, when given, must be a float.  The function "wiggles"
  them by +/- 10%.
  """
  pars = {"format": "votable"}
  pars["t_eff"] = _wiggle(teff)
  pars["log_g"] = _wiggle(logg)
  for el, abundance in elements.items():
    pars["w_%s"%el] = _wiggle(abundance)

  svc = pyvo.dal.SSAService("http://dc.g-vo.org/theossa/q/ssa/ssap.xml")
  return svc.create_query(**pars).execute()


def plot_spectrum(ax, spectrum):
  """plots spectrum (an SSA result from theossa) into fig, offset by teff,
  into the matplotlib axes ax.
  """
  teff = spectrum.get("t_eff")
  t = Table.read(spectrum.acref)
  ax.plot(t["spectral"], np.log(t["flux"])+teff/TEFF_SCALER)
  ax.text(max(t["spectral"]), teff/TEFF_SCALER, str(teff),
    horizontalalignment="right")


def make_plot(spectra):
  """arranges spectra in a plot, showing evolution by teff.
  """
  from matplotlib import pyplot
  fig = pyplot.figure(figsize=(4,6))
  ax = fig.add_axes([0,0,1,1])

      for sp in spectra:
      plot_spectrum(ax, sp)

      with open("combined.pdf", "wb") as f:
      pyplot.savefig(f, format="pdf")


if __name__=="__main__":
  specs = discover_spectra(logg=6, C=0.0034, He=0.284, H=0.715)
  make_plot(specs)

Overview

You can access this service using:

• form -- an interface for web browsers through an HTML form
• ssap.xml -- a standard SSAP interface as defined by the IVOA to access spectral or time-series data; SSAP clients use http://dc.zah.uni-heidelberg.de/theossa/q/ssa/ssap.xml? to access the service

Copyright, License, Acknowledgements

When publishing research making use of this service, please acknowledge: "The TheoSSA service (http://dc.g-vo.org/theossa) used to retrieve theoretical spectra for this paper was constructed as part of the activities of the German Astrophysical Virtual Observatory."

Citation Info

VOResource XML (that's something exclusively for VO nerds)