2 Comments

Notes to individual binary systems follow, sorted in order of WDS designation (the 2000-epoch right ascension- and declination-based designation used in the Washington Visual Double Star Catalog of Worley & Douglass 1996).

WDS 04089+4614 = ADS 3007 = A 998 = HD 25987 For the purpose of orbit calculating the position angle is corrected for $180\hbox{$^\circ$ }$ in four cases as follows: 1981.01, 1982.06, 1983.84, 1985.00.

The obtained orbital elements yield a parallax value in good agreement with the trigonometric parallax given in the Hipparcos Catalogue ( $0\hbox{$.\!\!^{\prime\prime}$ }00665\pm0\hbox{$.\!\!^{\prime\prime}$ }00096$).

The measuring of this pair grows in its difficulty and at the epoch of periastron passage in 2010 the component separation will be $\sim 0\hbox{$.\!\!^{\prime\prime}$ }07$only.

WDS 04275+1113 = ADS 3228 = BU 1186 = HD 28217 This pair, visible by the naked eye in the constellation of Taurus, was discovered in 1890 by Burnham S.W. The separation of the components was about $0\hbox{$.\!\!^{\prime\prime}$ }6$ then. From Aitkin's measurement in 1898 the pair grew closer and more unfavourable for the measurements (McAlister & Hartkopf 1988).

The elements are based on a change in $\theta$ of about $60^{\circ}$, but one should take into account that the pair has a high inclination ( $i=120^{\circ}$) and that already 1/4 of the orbital plane has been defined by the observations.

For the purpose of obtaining the parallax and absolute magnitude we use the empirical relation concerning the stars above the main sequence in the HR diagram (luminosity class - LC - B8 IV). The Hipparcos Catalogue yields for this pair $0\hbox{$.\!\!^{\prime\prime}$ }00670\pm 0\hbox{$.\!\!^{\prime\prime}$ }00096$ as its trigonometrical parallax, whereas the orbital parallax obtained by us is somewhat higher $0\hbox{$.\!\!^{\prime\prime}$ }009$.

WDS 04400+2301 = ADS 3370 = HU 442 = HD 29538 The orbital elements for this Hussey W.L. pair, discovered in 1901, are based on a change in the position angle of $103^{\circ}$. Due to its faint components and the separation not exceeding $0\hbox{$.\!\!^{\prime\prime}$ }5$ the pair has not been much observed. Nevertheless, the available observations allow to define the orbit position sufficiently well.

The spectral type and the obtained absolute magnitude indicate that the system belongs to LC VI (subdwarfs). By applying the mass-luminosity relation to the stars below the main sequence one obtains a parallax significantly higher ( $0\hbox{$.\!\!^{\prime\prime}$ }009$) than that given in the Tycho Catalogue ( $0\hbox{$.\!\!^{\prime\prime}$ }0016\pm0\hbox{$.\!\!^{\prime\prime}$ }0009$).

Figure 1: Observed positions ( $\ifmmode\hbox{\rlap{$\sqcap$ }$\sqcup$ }\else{\unskip\nobreak\hfil \penalty50\h... ...x{\rlap{$\sqcap$ }$\sqcup$ } \parfillskip=0pt\finalhyphendemerits=0\endgraf}\fi$$\diamond$) and the ones emanating from the orbit calculation ( $\ifmmode\hbox{\rlap{$\sqcap$ }$\sqcup$ }\else{\unskip\nobreak\hfil \penalty50\h... ...x{\rlap{$\sqcap$ }$\sqcup$ } \parfillskip=0pt\finalhyphendemerits=0\endgraf}\fi$). The periastron position ($\Pi$) and the line of nodes ($\Omega$) are given as well. The unit on both axes is second of arc

Figure 1: continued

  

Table 2: Measurements and (O-C)

$$\begin{tabular}{lrlccrr} \noalign{\hrule\medskip } \multispan... ...13$&$ -0.01$\\ \noalign{\medskip\hrule\medskip } \end{tabular}$$

$$\begin{tabular}{lrlccrr} \noalign{\hrule\medskip } \multispan... ...4 $&$-0.01 $\\ \noalign{\medskip\hrule\medskip } \end{tabular}$$

  

Table 2: continued

$$\begin{tabular}{lrlccrr} \noalign{\hrule\medskip } \multispan... ...8 $&$-0.04 $\\ \noalign{\medskip\hrule\medskip } \end{tabular}$$

$$\begin{tabular}{lrlccrr} \noalign{\hrule\medskip } \multispan... ...1 $&$-0.07 $\\ \noalign{\medskip\hrule\medskip } \end{tabular}$$

  

Table 2: continued

$$\begin{tabular}{lrlccrr} \noalign{\hrule\medskip } \multispan... ...8 $&$-0.08 $\\ \noalign{\medskip\hrule\medskip } \end{tabular}$$

$$\begin{tabular}{lrlccrr} \noalign{\hrule\medskip } \multispan... ...4 $&$ 0.02 $\\ \noalign{\medskip\hrule\medskip } \end{tabular}$$

 

Table 2: continued

$$\begin{tabular}{lrlccrr} \noalign{\medskip\hrule\medskip } \... ...9$&$ -0.11 $\\ \noalign{\medskip\hrule\medskip } \end{tabular}$$

$$\begin{tabular}{lrlccrr} \noalign{\hrule\medskip } \multispan... ...3 $&$ 0.04 $\\ \noalign{\medskip\hrule\medskip } \end{tabular}$$

 

Table 2: continued

$$\begin{tabular}{lrlccrr} \noalign{\hrule\medskip } \multispan... ...5 $&$-0.02 $\\ \noalign{\medskip\hrule\medskip } \end{tabular}$$

  

Table 3: Ephemerides

$$\begin{tabular}{crrrrrrrr} \noalign{\hrule\medskip } \hfil WD... ... $&$292.32 $&$0.29 $\\ \noalign{\medskip\hrule } \end{tabular}$$

WDS 18018+0118 = ADS 10990 = BU 1125 = HD 164577 The orbital elements are obtained from a position-angle change of $104^{\circ}$. The measurements have a large scatter.

The pair is on the main sequence of HR diagram. The obtained orbital parallax $0\hbox{$.\!\!^{\prime\prime}$ }0012$ agrees well with the one given in the Hipparcos Catalogue ( $0\hbox{$.\!\!^{\prime\prime}$ }001231\pm0\hbox{$.\!\!^{\prime\prime}$ }000083$).

Popovic and Pavlovic failed in noticing the duplicity of this system on May 27, 1998 when they tried to measure this pair. The cause is, most probably, in the magnitude difference $\triangle m=4\hbox{$.\!\!^{\rm m}$ }8$. For this moment, according to the ephemeris, $\rho$ is $0\hbox{$.\!\!^{\prime\prime}$ }56$.

WDS 18033+3921 = ADS 11023 = STF 2275 = HD 88432 In the calculation of the elements the position angle is corrected for $180^{\circ}$ in the case of two Baize's observations from 1954.70 and 1956.70 and also for one Worley's observation from 1961.43. The orbital parallax derived here agrees fully with the trigonometric parallax given in the Hipparcos ( $0\hbox{$.\!\!^{\prime\prime}$ }00836\pm0\hbox{$.\!\!^{\prime\prime}$ }00092$).

At the time of periastron passage in 2012 the component separation will be $\sim 0\hbox{$.\!\!^{\prime\prime}$ }3$.

WDS 18054+6216 = ADS 11073 = HU 1290 = HD 166206 The elements are obtained from a position-angle change exceeding $90^{\circ}$. The value obtained for the absolute magnitude and the F8 spectrum indicates that the system belongs to subgiants (LC IV). The orbital parallax obtained here is $0\hbox{$.\!\!^{\prime\prime}$ }008$. The agreement with the trigonometric one following from the Hipparcos Catalogue ( $0\hbox{$.\!\!^{\prime\prime}$ }00779\pm 0\hbox{$.\!\!^{\prime\prime}$ }00075$) is complete.

WDS 19389+3514 = ADS 12746 = HU 953 = HD 185696 This pair grows in its measuring suitability and the component separation at the time of intersecting the node line will be $\sim 0\hbox{$.\!\!^{\prime\prime}$ }3$. The obtained orbital parallax is $0\hbox{$.\!\!^{\prime\prime}$ }013$ whereas in the Tycho Catalogue one finds $0\hbox{$.\!\!^{\prime\prime}$ }029 \pm 0\hbox{$.\!\!^{\prime\prime}$ }006$.

WDS 20176+2622 = ADS 13649 = BU 984 = HD 193095 The significant number of measurements for this pair, in spite of a modest change of its position angle $-60^{\circ}$, permits a good orbit determination.

The parallax and the absolute magnitude are calculated following the empirical mass-luminosity relation concerning the HR main sequence. According to the absolute magnitude from the Tycho Catalogue this pair would be a subgiant (LC IV). Our parallax ( $0\hbox{$.\!\!^{\prime\prime}$ }015$) is within the parallax-error limits indicated by the Tycho Catalogue ( $0\hbox{$.\!\!^{\prime\prime}$ }011\pm0\hbox{$.\!\!^{\prime\prime}$ }005$).