\documentstyle[twoside, epsf]{article}

\input ibvs2.sty

\begin{document}

\IBVShead{5051}{30 March 2001} 

\IBVStitletl{Discovery of a Secondary Spectrum in the SB1 System}{ HD~434}

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

\IBVSinst{Institute of Astronomy, National Astronomical Observatory, 
P.O.B. 136, BG -- 4700, Smolyan, Bulgaria\\
\indent e-mail: iliani@astro.bas.bg}


\IBVSinst{Astronomical Institute, Slovak Academy of Sciences,
059 60 Tatransk\'{a} Lomnica, Slovak Republic\\ 
\indent e-mail: budaj@ta3.sk, ziga@ta3.sk, zve@ta3.sk}

\IBVSkey{spectroscopy}
\SIMBADobjAlias{HD 434}{HIP 728}

\IBVSabs{We report detection of the secondary spectrum in the former}
\IBVSabs{SB1 system HD 434. Both components exhibit pronounced Am} 
\IBVSabs{anomalies. Their rotation is probably synchronized in spite of}
\IBVSabs{relatively long orbital period.} 

\begintext 

Radial velocity variations of HD 434 (HIP 728, BD +27\deg3, SAO 73772,
$m_V = 6.47$) were discovered by Shajn (1951) who also classified
the spectrum as A2s. Palmer et al.\ (1968) classified the star as A4Vm
and estimated its $v \sin i = 60~{\rm km\,s^{-1}}$.  Hube \& Gulliver
(1985) reported a preliminary orbit based on 38 spectrograms of a
reciprocal dispersion 15~\AA/mm. Later on, Margoni et al.\ (1992),
using photographic spectra of 42~\AA/mm, confirmed the orbital
elements.  Nevertheless, in the same year Sreedhar Rao \& Abhyankar
(1992) published the radial velocity curve obtained from 33
photographic spectra (33~\AA/mm and the resolution of 0.66~\AA)
which differs significantly in $V_{0}$ and $K$ from that of Hube \&
Gulliver (1985). They also speculated about a secondary spectrum and
concluded that the secondary component should be at least 1\fmm5
fainter in the visible so that it was not seen in their and previous
spectra. CCD observations were called for.

Our spectroscopic observations were carried out with the 2-m RCC
telescope of the Bulgarian National Astronomical Observatory in the
frame of our observational program on Am-stars in binary systems.
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 two different spectral
regions 100 \AA\ wide and centered  on 6440 \AA\ and 6720 \AA\ with $R =
32000$. The typical $S/N$ ratio is 250--350. Wavelength calibration has
the r.m.s.\ error of 0.005~\AA\@. 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. Rectification, equivalent widths and radial velocities were
measured using the EQWREC2 code (Budaj \& Kom\v{z}\'{\i}k 2000).  The
log of observations is listed in Table 1.

\begin{table}[b]
\caption{List of observations, HD 434}
\begin{center}
\begin{tabular}{ccc}
\hline
Date  &  HJD (2400000\,+) & Region [\AA] \\
\hline
03.01.2001 & 51913.1625 & 6667--6770 \\
04.01.2001 & 51914.1977 & 6389--6492 \\
\hline
\end{tabular}
\end{center}
\end{table}

\IBVSfig{10.5cm}{5051-f1.eps}{HD~434, phase = 0.97. Both components are mixed}

\IBVSfig{10.5cm}{5051-f2.eps}{HD~434, phase = 1.00, next day. Both components
are clearly resolved}

The secondary component lines are not seen in our first spectrum of
HD~434 (orbital phase 0.97, Fig.~1) (phases were computed following the
ephemeris $$T = 2447186.26 + 34\fday25999 \times E,$$ (where $T$ is the
time of periastron passage) given by Sreedhar Rao \& Abhyankar
(1992)).  However, a clear secondary spectrum was observed next day
(orbital phase 1.00, Fig.~2) although the orbital period is quite
long.  It appeared due to the high eccentricity of the orbit
($e=0.41$). From the ratio of equivalent widths of the Ca {\sc i} 6718
and Fe {\sc i} 6678 lines, ($[{\rm Ca/Fe}] = 0.27$), we can infer that
at least the brighter A component has strong Am peculiarity.  This
ratio is about 0.9 for normal stars but can be as low as 0.2 for the
strongest Am stars (Boesgaard 1987, Burkhart \& Coupry 1989, 1991,
1997, Iliev et al.\ 1998). The spectrum obtained at phase 1.00, with
clearly separated lines of components, allows us to obtain more
information. It is apparent that the projected rotational velocity of
the A component is much lower than previously thought (about $32~{\rm
km\,s^{-1}}$, half of the previous value). We were also able to
determine the value of $v \sin i$ of the B component and it seems to be
very much the same, about $27~{\rm km\,s^{-1}}$. From the Ca and Fe
lines of this spectrum it seems that not only the A but both components
exhibit pronounced Am anomalies. Although we have no spectrum from the
region 6667--6770~\AA\ at phase 1.00 (the $[{\rm Ca/Fe}]$ ratio used
for classification purposes has to be determined from the lines of Ca
{\sc i} 6718 and Fe {\sc i} 6678), we found that the Ca {\sc i} lines
are weak, what is a typical feature of Am stars.  Radial velocities
measured from the spectrum at phase 1.00 are:  $v_{\rm A}= -21.8 \pm
0.4~{\rm km\,s^{-1}}$, $v_{\rm B}= 52.2 \pm 0.3~{\rm km\,s^{-1}}$.  The
orbital period is rather long ($\approx 34$ days), and possible
synchronization in this system would give another support to the
hydrodynamical synchronization mechanism of Tassoul \& Tassoul (1992)
which remains operative for rather large orbital periods up to $P_{\rm
orb}\approx 100$ days. The pronounced Am anomalies of both components
and the rather eccentric orbit seem to conform the hypothesis of Budaj
(1996, 1997, 1999) about a stabilization mechanism in binary systems
competing with diffusion processes.

\bigskip \noindent This work was supported by VEGA grant No.~7107.

\references

Boesgaard, A.N., 1987, {\it ApJ}, {\bf 321}, 967 %\BIBCODE{1987ApJ...321..967B}

Budaj, J., 1996, {\it A\&A}, {\bf 313}, 523 %\BIBCODE{1996A&A...313..523B}

Budaj, J., 1997, {\it A\&A}, {\bf 326}, 655 %\BIBCODE{1997A&A...326..655B}

Budaj, J., 1999, {\it MNRAS}, {\bf 310}, 419 %\BIBCODE{1999MNRAS.310..419B}

Budaj, J., Kom\v{z}\'{\i}k, R., 2000, http://www.ta3.sk/\~{}budaj/software

Burkhart, C., Coupry, M.F., 1989, {\it A\&A}, {\bf 220}, 197 %\BIBCODE{1989A&A...220..197B}

Burkhart, C., Coupry, M.F., 1991, {\it A\&A}, {\bf 249}, 205 %\BIBCODE{1991A&A...249..205B}

Burkhart, C., Coupry, M.F., 1997, {\it A\&A}, {\bf 318}, 870 %\BIBCODE{1997A&A...318..870B}

Hube, D.P., Gulliver, A.F., 1985, {\it J. R. Astron.\ Soc.\ Canada}, {\bf 79}, 49
%\BIBCODE{1985JRASC..79...49H}

Iliev, I.Kh., Budaj, J., Zverko, J., Barzova, I.S., \v{Z}i\v{z}\v{n}ovsk\'{y}, J., 
1998, {\it A\&AS}, {\bf 128}, 497 %\BIBCODE{1998A&AS..128..497I}

Margoni, R., Munari, U., Stagni, R., 1992, {\it A\&AS}, {\bf 93}, 545 
%\BIBCODE{1992A&AS...93..545M}

Palmer, D.R., Walker, E.N., Jones, D.H.P., Wallis, R.E., 1968, {\it R. Greenwich 
Obs.\ Bull.}, No.\ 135 \BIBCODE{1968RGOB..135..385P}

Shajn, G.A., 1951, {\it Izv.\ Krym.\ Astrophys.\ Obs.}, {\bf 7}, 124 

Sreedhar Rao, S., Abhyankar, K.D., 1992, {\it MNRAS}, {\bf 258}, 819 %\BIBCODE{1992MNRAS.258..819S}

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

\endreferences
\end{document}
