\documentstyle[twoside, epsf]{article}
%\documentstyle[twoside,psfig]{article}

\input ibvs2.sty

\begin{document}

\IBVShead{5199}{13 November 2001}

\IBVStitle{Detection of a ternary spectrum in HD\,216608}

\IBVSauth{Iliev, I. Kh.$^{1}$; Budaj, J.$^{2}$; \v{Z}i\v{z}\v{n}ovsk\'{y}, J.$^{2}$; Zverko, J.$^{2}$; Stateva, I.$^{1}$; Geordzheva, E. K.$^{3}$}

\IBVSinsto{$^{1}$ Institute of Astronomy, National Astronomical Observatory,
P.O.B. 136, BG - 4700, Smolyan, Bulgaria\\
\indent $^{2}$ Astronomical Institute, Slovak Academy of Sciences,
059 60 Tatransk\'{a} Lomnica, Slovak Republic\\
\indent $^{3}$ Technical University Sofia, Plovdiv Branch, Bulgaria\\
\indent e-mail: iliani@astro.bas.bg, budaj@ta3.sk, ziga@ta3.sk, zve@ta3.sk}

\IBVSkey{spectroscopy}
\SIMBADobjAlias{HD 216608}{HIP 113048}

\IBVSabs{We report detection of the second and third spectrum in the}
\IBVSabs{visual and SB1 system HD 216608.}
\IBVSabs{Lines of both new components are very sharp and are clearly}
\IBVSabs{travelling and crossing. They probably both belong to the visual B}
\IBVSabs{companion of HD 216608A.}
\IBVSabs{These sharp lines cause heavy blends of the third broad line}
\IBVSabs{spectrum which we ascribe to the HD 216608A.}
\IBVSabs{Consequently, the orbit and SB1 nature of HD 216608A is questioned} 
\IBVSabs{while HD 216608B seems to be a new SB2 system.}

\begintext

This star (HD 216608, HR 8708, SAO 52465, HIP 113048, BD +43 4331)
is a visual binary system ADS 16345 AB.
The B companion (F6V star) revolves about the primary with a period of 105 yr, 
major semi-axis of 0."60 and $M_{\rm A}+M_{\rm B}=2.62M_{\odot}$
(Finsen \& Worley 1970, S\"{o}derhjelm 1999).
HIPPARCOS lists the visual B companion separated by 0\farcs95 (ESA 1997).
Fabricius \& Makarov (2000) obtained the following magnitudes in the Tycho
passbands: $B_{T}=6\fmm29, V_{T}=6\fmm01$ for the A companion and 
$B_{T}=8\fmm43, V_{T}=7\fmm81$ for the B companion. There is also an optical 
C companion, 10\fmm7 , at 28\farcs0 (Abt \& Levy 1985). The brightest member 
 (HD 216608A) is an SB1 binary. It was first reported as variable in radial 
velocity by Young (1939). Later on this was confirmed by Abt et al. (1980). 
Its Am characteristics were discovered by Walker (1966) who also are 
A2V spectral type and $v \sin i=50$ km\,s$^{-1}$. Cowley et al. (1969) 
classified the star as A3m, Abt (1981) as Am and A3/F0V/F4  
from the CaII K/Hydrogen/Metallic lines (abbreviated usually as K/H/M). 
Another classification is proposed by Sreedhar Rao \& Abhyankar (1991) 
according to the K, m39, m43 and SrII 4077 lines: A3V, F2III/IV, F2III/IV 
and Ap, respectively. Orbital elements 
($P_{\rm orb}=24\fday1635$, $e=0.2$, $K=10.1$ km\,s$^{-1}$) were derived by 
Abt \& Levy (1985) from the photographic plates with a resolution of 0.4 \AA~ 
and a dispersion of 16.9 \AA\,mm$^{-1}$. They also give spectral types A2/A8/F2 from 
the K/H/M lines, respectively. Abt \& Moyd (1973) measured 
$v \sin i=35$ km\,s$^{-1}$ while Abt \& Morrell (1995) obtained 
$v \sin i=46$ km\,s$^{-1}$ from CCD spectra with a resolution of 0.33 \AA. 
They also reclassified the star as Am (A2/F1/F2). Tokovinin (1997) estimated 
the following masses for the companions:
$M_{\rm Aa}=2.54 M_{\odot}$, $M_{\rm Ab}\ge 0.27 M_{\odot}$, 
$M_{\rm B}=1.25 M_{\odot}$. 

Our spectroscopic observations were carried out with the 2m RCC telescope of
the Bulgarian National Astronomical Observatory in the frame of our
observational program on Am stars in binary systems. The Photometrics AT200 
camera with a SITe SI003AB $1024 \times 1024$ CCD chip, 
($24\,\mu {\rm m}$ pixels) was used in the Third camera of the coud\'e 
spectrograph to provide spectra in the 6400--6500 \AA~ region with R = 32000. The typical S/N 
ratio is about 300. IRAF standard procedures have been used for bias 
subtracting, flat-fielding and wavelength calibration. Telluric lines have been 
removed using spectra of hot, fast rotating stars. Wavelength calibration has 
the r.m.s. error of 0.005\,\AA. The log of observations is listed in Table 1. 

\begin{table}[ht]
\caption[]{List of observations: Date, HJD of the beginning of the exposure
and effective exposure time.}
\small
\begin{center}
\begin{tabular}{cccc}
\hline
Sp.No.& Date  &  HJD (2450000+) & Eff. exp. (in seconds)\\
\hline
1&  10.6.2001 & 2071.496 & 3000\\
2&  30.8.2001 & 2152.408 & 7210\\
3&  2.9.2001  & 2155.364 & 4280\\
\hline
\end{tabular}
\end{center}
\end{table}

A small portion of all the three spectra in the vicinity of CaI 6439 which is
most illustrative is depicted in Fig. 1. We have chosen this line as 
it is free of blends. It is apparent that there are two systems of sharp 
lines travelling and crossing in the spectra. Nevertheless, all the lines in 
the spectra are broader and stronger than what could be expected from a simple 
sum of both sets of sharp lines (note e.g. the Fe lines). This fact seems to 
be caused by a third faster rotating star which does not seem to have moved 
in our 3 spectra within the precision of measurements.

\IBVSfig{9.5cm}{5199-f1.eps}{Three successive spectra of HD\,216608. While 
Ba and Bb lines are clearly separated on the first spectrum, they shade in 
the next spectrum to become separated again in the third spectrum. Lines of 
the A component are much wider and do not seem to have moved.}


Based on what is known about the system, one could conclude that the 
apparently moving sharp line components are formed in the above mentioned 
SB1 system HD\,216608A while the broad line component belongs probably to 
the visual B companion. However, this interpretation has serious gaps.
The visual A companion is hotter and brighter than the B companion and it is 
hardly probable that it has much sharper lines than the B one. Considering 
the synchronization mechanism of Tassoul \& Tassoul (1992) stretching 
to relatively long orbital periods could partly avoid the problem. However, 
these sharp lines, although very pronounced, carry only a very small amount 
of the total equivalent width of the ternary blend especially in iron lines. 
This guides us to suggest that the sharp lines belong rather to the visual 
B companion which thus seems to be a new SB2 binary. We will denote the deeper 
lines as the primary (Ba) and the less pronounced sharp lines as the secondary 
(Bb). The broad lines would then originate from the A companion. The broad 
components of the Ca lines are relatively much weaker than those of Fe lines 
what confirms the Am characteristics of HD\,216608A making both sharp line 
components more outstanding in Ca than in Fe.

The above accounts were confirmed by fitting the CaI line with three 
gaussians (Kratka 1988; Sp. No. 2 only with two gaussians as Ba and Bb
overlap). All three spectra give a consistent output as far as the depth and 
half-widths of all 3 components is concerned what gives firmer footing to the 
result presented above (see Table 2). This also explains the inconsistent 
rotational velocities of different authors ranging from 35 to 50 km\,s$^{-1}$. 
Under the assumption that the velocity of the mass centre of Ba+Bb did not 
change during the summer, we get from the Sp. No. 1 and 3 for the mass ratio: 
$M_{\rm Ba}/M_{\rm Bb}=\Delta v_{\rm Ba}/ \Delta v_{\rm Bb}=47.9/34.4 = 1.39$.
This mass ratio then yields radial velocity of the mass center Ba+Bb: 
$v_{\rm B}=8.0$ km\,s$^{-1}$. This value is consistent with the radial velocity 
of the Ba+Bb blend from Sp. No. 2 where Ba and Bb lines roughly overlap. 
The estimated $1 \sigma$ precision of our radial velocity measurements 
is about 1 km\,s$^{-1}$ for the sharp Ba and Bb lines and about 
4 km\,s$^{-1}$ for the broad A companion lines.

Finally, we have used the spectrum synthesis code SYNSPEC (Hubeny et al. 1995, 
Krti\v{c}ka 1998) to fit the spectra and estimated the following values of 
$v \sin i$: 9, 5, 43 km\,s$^{-1}$ for Ba, Bb and A component, respectively.
An allowance for the instrumental profile was included in the above
procedure. In the case of both sets of sharp lines it makes no sense to 
correct for another free parameter, thus microturbulence was set to zero. 
Consequently, their rotational velocities are rather upper limits. In the case 
of broad lines microturbulence of about 2 km\,s$^{-1}$ was considered which 
made a better fit of the iron lines. In our opinion sharp Ba and Bb lines 
cause heavy blends of broad A lines and could have affected previous radial 
velocity measurements in lower resolution leading to a spurious orbit. 
The previous mass estimates of all the components and the very SB1 nature of 
the HD\,216608A must certainly be revisited in the future. It is HD\,216608B 
which seems to be a newly discovered SB2 binary.

\begin{table}[ht]
\caption[]{Results of the CaI 6439 line fitting.}
\vskip 2mm
\small
\begin{center}
\begin{tabular}{|c|c|c|c|c|c|c|c|c|c|}
\hline
Sp.   &\multicolumn{3}{|c|}{central depth}     & 
\multicolumn{3}{|c|}{gaussian half width \AA}  &
\multicolumn{3}{|c|}{rad. velocities [km\,s$^{-1}$]}\\
No. & Ba   &  Bb   &  A    &  Ba  &  Bb  & A    & Ba    & Bb   &  A   \\
\hline
1   &0.069 & 0.026 & 0.035 & 0.16 & 0.11 & 0.70 & -14.2 & 38.9 & 12.1 \\ 
\hline
2   &\multicolumn{2}{|c|}{0.068}         & 0.041 &
\multicolumn{2}{|c|}{0.12}                 &  0.52 &   
\multicolumn{2}{|c|}{9.6}                  &  4.0  \\
\hline
3   &0.064 & 0.018 & 0.035 & 0.14 & 0.12 & 0.60 &  20.2 & -9.0 &  0.5 \\
\hline                            
\end{tabular}
\end{center}
\end{table}


\vskip 2mm
\noindent
This work was partially supported by VEGA grant No. 7107.

\references

Abt, H.A., 1981, {\it ApJS} {\bf 45}, 437
%\BIBCODE{1981ApJS...45..437A}

Abt, H.A., Levy, S.G., 1985, {\it ApJS} {\bf 59}, 229
%\BIBCODE{ 1985ApJS...59..229A}

Abt, H.A., Morrell, N.I., 1995, {\it ApJS} {\bf 99}, 135
%\BIBCODE{1995ApJS...99..135A}

Abt, H.A., Moyd, K.I., 1973, {\it ApJ} {\bf 182}, 809
%\BIBCODE{1973ApJ...182..809A}

Abt, H.A., Sanwal, N.B., Levy, S.G., 1980, {\it ApJS} {\bf 43}, 549
%\BIBCODE{1980ApJS...43..549A}

Cowley, A.P., Cowley, C.R., Jaschek, M., Jaschek, C., 1969, {\it AJ} 
{\bf 74}, 375
%\BIBCODE{1969AJ.....74..375C}

ESA, 1997 in {\it The Hipparcos and Tycho Catalogues}, ESA SP-1200
%\BIBCODE{1997yCat.1239....0E}

Fabricius, C., Makarov, V.V., 2000, {\it A\&A} {\bf 356}, 141
%\BIBCODE{2000A&A...356..141F}

Finsen, W.S., Worley, C.E., 1970, {\it Repl. Obs. Johannesburg, Circ.} {\bf 7}, 
201

Hubeny, I., Lanz, T., Jeffery, C.S., 1995, {\it Synspec - A User's Guide}

Kratka, M., 1988, private communication

Krti\v{c}ka, J., 1998, in: {\it Proceedings of the 20th Stellar
Conference}, J. Du\v{s}ek, M. Zejda (eds.), Brno, 73

S\"{o}derhjelm, S., 1999, {\it A\&A} {\bf 341}, 121
%\BIBCODE{ 1999A&A...341..121S}

Sreedhar Rao, S., Abhyankar, K.D., 1991, {\it Proc. Astron. Soc. 
Australia}, {\bf 9}, 285
% Original:
%Sreedhar Rao, S., Abhyankar, K.D., 1991, {\it Astron. Soc. of 
%Australia, Proceedings} {\bf 9}, No. 2, 285
% Corrected: Thu Aug 14 12:46:14 MET DST 2003

Tassoul, J.-L., Tassoul, M., 1992, {\it ApJ} {\bf 395}, 259
%\BIBCODE{1992ApJ...395..259T}

Tokovinin, A.A., 1997, {\it A\&ASS} {\bf 124}, 75
%\BIBCODE{1997A&AS..124...75T}

Walker, E.N., 1966, {\it The Observatory} {\bf 86}, 154
%\BIBCODE{1966Obs....86..154W}

Young, R.K., 1939, {\it Pub. David Dunlap Obs.} {\bf 1}, 71
\BIBCODE{1939PDDO....1...71Y}

\endreferences
\end{document}


