Gaia API Module

class orbitize.gaia.GaiaLogProb(gaia_num, hiplogprob, dr='dr2')[source]

Class to compute the log probability of an orbit with respect to a single astrometric position point from Gaia. Uses astroquery to look up Gaia astrometric data, and computes log-likelihood. To be used in conjunction with orbitize.hipparcos.HipLogProb; see documentation for that object for more detail.

Follows Nielsen+ 2020 (studying the orbit of beta Pic b). Note that this class currently only fits for the position of the star in the Gaia epoch, not the star’s proper motion.

Note

In orbitize, it is possible to perform a fit to just the Hipparcos IAD, but not to just the Gaia astrometric data.

Parameters
  • gaia_num (int) – the Gaia source ID of the object you’re fitting. Note that the dr2 and edr3 source IDs are not necessarily the same.

  • hiplogprob (orbitize.hipparcos.HipLogProb) – object containing all info relevant to Hipparcos IAD fitting

  • dr (str) – either ‘dr2’ or ‘edr3’

Written: Sarah Blunt, 2021

compute_lnlike(raoff_model, deoff_model, samples, param_idx)[source]

Computes the log likelihood of an orbit model with respect to a single Gaia astrometric point. This is added to the likelihoods calculated with respect to other data types in sampler._logl().

Parameters
  • raoff_model (np.array of float) – 2xM primary RA offsets from the barycenter incurred from orbital motion of companions (i.e. not from parallactic motion), where M is the number of orbits being tested, and raoff_model[0,:] are position predictions at the Hipparcos epoch, and raoff_model[1,:] are position predictions at the Gaia epoch

  • deoff_model (np.array of float) – 2xM primary decl offsets from the barycenter incurred from orbital motion of companions (i.e. not from parallactic motion), where M is the number of orbits being tested, and deoff_model[0,:] are position predictions at the Hipparcos epoch, and deoff_model[1,:] are position predictions at the Gaia epoch

  • samples (np.array of float) – R-dimensional array of fitting parameters, where R is the number of parameters being fit. Must be in the same order documented in System.

  • param_idx – a dictionary matching fitting parameter labels to their indices in an array of fitting parameters (generally set to System.basis.param_idx).

Returns

array of length M, where M is the number of input

orbits, representing the log likelihood of each orbit with respect to the Gaia position measurement.

Return type

np.array of float