Exercise SRK (optional): Formally the measured parallax
cannot be less than zero. Thus the distribution of the error of
the parallax cannot be Gaussian (especially if the SNR of the
measurement is modest). Compute the distance to the putative black
hole system using sensible approximation (i.e. parallax must be
>0).
References: Igoshev, Verbunt &
Cator (2016) | Bailer-Jones
(2015) Nota bene: The exercises are named in honor
of the participants in the class.