Comparativo de las Funciones de los Dos Órganos

Now that it has been determined that there are changes to the multiplicity of the original sample, we can take a look at the sample as a whole and see how its composition has changed. The original D&M sample, consisted of 164 systems and fractional numbers of 57:38:4:1:0% (single:double:triple:quadruple:quintuple%). If you add in all the new companions from the research done for this survey neglecting any removal of systems that no longer fit the selection criteria, the percentages change to 51:40:8:0.5:0.5% for those same 164 systems. To be truly consistent, we must apply the same selection criteria to the list again to remove any systems that no longer fall in the distance-limited sample as a result of HIPPARCOS, and recheck the objects removed previously to ensure they were not removed erroneously. For the 291 systems in the wide sample, it was determined that 6 systems, including the common proper-motion pair HD 186408/186427, should be added to the main sample since HIPPARCOS found that they are nearer than previously thought. Of the 164 stars in the multiplicity sample, only 100 retained membership based upon a distance closer than the limit, 22.5 pc. Table 6.1 shows which stars were removed in column 5 (represented with an

of the remaining 106 systems, and with that significant decrease in sample size we are left with a multiplicity percentages of 48:42.5:7.5:1:1%. A short summary of these numbers can be seen in Table 8.1 along with the number of companions per system. Ironically, this rather substantial change to the number of companions per system puts the overall G-dwarf multiplicity fraction closer to what Abt & Levy determined, even though their sample was heavily biased by false detections.

Table. 8.1: Overall Multiplicity

Multiplicity A&L D&M Current Corrected

# % # % # % # % Single 52 42 93 56.7 83 50.6 51 48.1 Double 57 46 62 37.8 66 40.9 45 42.5 Triple 11 9 7 4.3 13 7.3 8 7.5 Quadruple 3 2 2 1.2 1 0.6 1 0.95 Quintuple 0 0 0 0.0 1 0.6 1 0.95 Systems 123 100 164 100 164 100 106 100 Companions 85 82 99 68 Comp/system 0.69 0.50 0.60 0.64

Note. Included here are the number of systems of each multiplicity type and the percentages associated with them for the original D& M sample, the sample with updated companions, and the final list corrected to remove those stars that no longer fall within the parallax limited range. The last three rows detail the total number of systems contained in each multiplicity level, the number of companions, and the number of companions per system respectively.

It is seen that solar-type stars are more likely to have at least one companion than indicated by previous surveys. This invites a re-examination of several other discussion

topics of D&M. How does this affect the distribution of q (mass fraction: q = M2/M1),

logP, and the overall scatter of logP vs. e? In fact, there is very little change. Looking at

Figures 8.1, 8.2, and 8.3, we can see very little difference in the overall distributions. The

maxima forq and logP remain very much the same and the scatter of log P vs.ealso is not

altered to a large degree, leaving the conclusions made by D&M valid for this sample. It is interesting to see a large number of the eccentric young binaries (a major binary formation tracer) have been removed due to their parallax change. This implies that the spatial density of these systems is less than previously believed. A rather large number (10) of the doubles that were eliminated from the sample in this effort have been discovered to be almost twice as far away as they were originally calculated along with at least five mis-identified giants whose classifications have still not been corrected. One such star, HD 5857, has been classified on multiple occasions as recently as 2007 as a G5 without a luminosity class, has a glaring

V −K=+4.0 and a tiny 9 mas parallax which seem to have gone unnoticed by most. It also

seems strange that a few of these same stars had parallaxes that were almost 10 times larger

than currently measured (ex. HD 147266 with πold=99 mas and πHip=9.45 mas) where it

leads to the question of whether or not a misplaced decimal point allowed some of these systems to be included accidentally!

The most significant revision resulting from this effort was the change in multiplicity and through that, the number of companions per system. Though many of the additional com-

Figure. 8.1: Distribution of Mass Ratio from the D&M and SFP Samples. The larger darker bars on the right of each bin show the distribution of the secondary mass compared with the primary for the sample before being corrected for parallax. The bars to the left show how the distribution in general remains much the same with the removal of 64 and the addition of 6 systems. Although the same in general distribution, a significant number of systems in the 0-0.1 and 0.6-0.7 bins were eliminated with respect to the others. The similarly colored lines mimic the distribution fits for each subset.

panions that have since been discovered were covered through the predicted missing multiples (most of the new companions were low mass M, L and T dwarfs), the sheer number of systems eliminated from this project through the changes in parallax was surprising. Also, nearly a sixth of those stars removed were within 5 mas of the cut-off 45 mas limit for both D&M’s and this sample. A more significant change would have been the altering of the maxima in

eitherq or logP, neither of which occurred. Thus, it is reasonable to accept the conclusions

of the most likely companion mass being small compared to the primary and the peak of the unimodal distribution of periods remains at approximately 180 years as determined by D&M.

Figure. 8.2: Distribution oflogP. The distribution of orbits, in the same format as Figure 8.1, show that the samples of the SFP Survey and D&M are quite similar. The lighter bars show dips in bins 2, 5 and 6, due mostly to the removal of systems with misrepresented parallaxes. Many of the systems removed in the 250 to 25,000 year zone were common-proper motion binaries whose parallaxes had been overestimated where the period was based mostly on the separation.