This week we have a look at another Mira type variable star. It is the star V809Ori in our Lambda-Ori target field. The object is clearly a background star, but it’s actual distance is not very well determined. Even with Gaia, the uncertainty of the parallax is almost as large as the parallax itself. This is of course in part caused by the large distance, but also by the very red colour and variable nature of the object. The current best estimates for the distance range from 3.1 to 5.6kpc, with the most likely value being about 4.2kpc.
In the light curve we show only the I-Band and V-band data. These are the most observed filters in this so far rather sparsely covered field. One can clearly see how the pulsations of the object change the brightness dramatically (by more than six magnitudes – a factor of 100). It also shows how difficult it can be to study variables that have a period of about one year, and which are also situated near the ecliptic. This means the objects regularly get close to the Sun and cannot be observed for about half a year at a time. Thus, for objects like V809Ori, with an estimated period of about 338 days, it means that each time they are observable one can only see the same part of the light curve. In this case the brightest peaks. We have so far not been able to measure the faintest state of the source, as it is completely hidden behind the Sun during this phase. With this period, it will take about 14 years for us to cover the entire evolution of this star. Well, we are about half way there 🙂