A few questions about Delta Trianguli

[PlutonianEmpire]

Do we know the age of the system? Is the info provided by Google Earth astronomy at all accurate? Why do their orbits in Celestia depict the stars as having equal mass and similar brightness when one of them seems to be smaller and dimmer in real life? And finally, how will this system die once DEL Tri A gets old and wrinkly?

[selden]

Celestia's representation of DEL Tri is specified in spectbins.stc

In general, Celestia's philosophy is for its primary star catalogs to be based on major published catalogs and then to provide carefully documented corrections for individual stars in separate revision stc files. Celestia's catalogs for binaries are new enough that nobody has started providing corrections based on more recent studies of individual systems.

[t00fri]

Do we know the age of the system? Is the info provided by Google Earth astronomy at all accurate? Why do their orbits in Celestia depict the stars as having equal mass and similar brightness when one of them seems to be smaller and dimmer in real life? And finally, how will this system die once DEL Tri A gets old and wrinkly?

Basically DEL Tri is an observationally difficult spectroscopic binary system. That's why even the authoritative catalog SB9 (2009) about spectroscopic binaries does neither give apparent visual magnitudes nor spectral types for BOTH components independently.

In the original renowned publication by D. Pourbaix that is at the base of my spectbins.stc data, a long paragraph is devoted to the problems related to this star system.

I copy it literally:

HIP 10644: Although the standard deviations of the orbital parameters are quite small, we are puzzled by the shape of the cross-correlation dip obtained with CORAVEL (Fig. 1 in the paper by Duquennoy & Mayor (1988a)). It suggests that the two proles overlap almost every time. It is therefore difficult to imagine that precise radial velocities can be extracted for both components. The authors also assumed the orbit to be circular. Although the mass ratio is close to unity, their difference of magnitudes in blue is 2:0 +- 0:2 mag. No information is given in the paper about the potential inconsistency of these two results

(kappa = MB / (MA+MB) ~ 0:5 and Delta m ~ 2 mag).

The simultaneous adjustment of the visual and spectroscopic data is a complete nightmare! In addition to the natural correlation between omega and T due to the nearly circular orbit, there is another strong, ?0.996, correlation between the inclination i and the parallax pi. Within the confidence interval on the inclination (7 deg-width), sin i ranges between 0.22 and 0.34. Therefore, a small variation on i implies a large variation on pi. That is the reason why our results are quite imprecise (and rather unreliable): pi = 136 +- 30 mas, MA = 0.25 +- 0.16 M_sol and MB = 0.23 +- 0.14 M_sol. The parallax after Hipparcos (ESA 1997) is 92.2 +-0.84 mas is consistent neither with our value nor with the estimate of Van Altena et al. (1991).

In Celestia's official database you will only find data that have been measured with reasonable confidence. In my forthcoming updates of spectbins.stc and visualbins.stc many important catalogs have been searched and the results merged. Hence any missing entries are REALLY not known sufficiently well!

For DEL Tri I have decided to include the magnitude difference ~ 2.0 mentioned inofficially in Pourbaix's above HIP 10644 discussion. Moreover, I switched from the distance given by Pourbaix ( < 25 ly) to the distance (~ 35 ly) given in the revised HIP data.

Fridger