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\begin{document}

\IBVShead{4667}{29 January 1999}

\IBVStitle{The Carbon Star V1965 C\lowercase{yg}}

\IBVSauth{T.~Tomov$^{1,2}$, M.~Rejkuba$^{3}$, U.~Munari$^{1}$}

\IBVSinst{Osservatorio Astronomico di Padova, Sede di Asiago, via
          dell'Osservatorio 8, I-36012 Asiago (Vicenza), Italy}
\IBVSinst{Visiting Professor, Consiglio Nazionale delle Ricerche d'Italia,
          Unit\`a di Ricerca Padova-Asiago}
\IBVSinst{Departamento de Astronom\'{\i}a y Astrof\'{\i}sica, Pontificia
          Universidad Cat\'{o}lica de Chile, Casilla 104, Santiago 22, Chile} 
 
\SIMBADobj{V1965 Cyg}
\IBVStyp{ * }
\IBVSkey{spectroscopy}

\begintext

V1965~Cyg is entry \#2754 in the General Catalogue of Cool Carbon Stars
(Stephenson, 1973), and \#4347 in the Second edition of the same Catalogue
(Stephenson, 1989).

Unfortunately, the star was mis-identified with the nearby
Mira variable V1129~Cyg and this error propagated over many
papers. Alksnis et al.\ (1990) and Kazarovets et~al.\ (1990) tried to
stop this confusion presenting observational evidences that V1129~Cyg
and V1965~Cyg (= IRAS\,19321+2757 = CGCS\,4347 = RAFGL\,2417 = C\,2754
= NSV\,12165 = IRC\,+30374 = CSV\,4727) are indeed different objects.

V1965~Cyg has remained a poorly known object, without a devoted
investigation in literature. We obtained low-resolution spectra of it
in 1994, 1995 and 1997, and one Echelle spectrum in 1997. The
low-resolution observations were secured with the Boller \& Chivens+CCD
($R\sim$\,18\,\AA) spectrograph of Padova \& Asiago Astronomical
Observatory 1.82 m telescope. The high-resolution spectrum was obtained
with the Echelle+CCD ($R\sim$ 0.3\,\AA) spectrograph at the same
telescope. The spectra were extracted and calibrated in a standard
fashion using the IRAF\IBVSfm\ reduction package running on a PC
under Linux operating system.  The journal of observations is given in
Table~1.  \IBVSfoot{IRAF is distributed by the National Optical
Astronomy Observatories, which are operated by the Association of
Universities for Research in Astronomy, Inc., under cooperative
agreement with the National Science Foundation.}

\begin{table}[h]
\caption{Journal of observations}
\begin{center}
\begin{tabular}{ccccc}
\hline
Date & JD & Exp. time & Resolution & Instrument \\
     & 2400000+ & [sec] & [\AA]   &  \\       
\hline
10. Dec.\ 1994 & 49697.28 &  45+720  & 18 & B\&C+CCD \\
15. Oct.\ 1995 & 50006.29 & 120+420  & 18 & B\&C+CCD \\
13. Nov.\ 1997 & 50766.26 & 1590       & 0.3& Echelle+CCD \\
20. Nov.\ 1997 & 50773.26 & 1500       & 18 & B\&C+CCD \\
\hline
\end{tabular}
\end{center}
\end{table}

\IBVSfig{10cm}{4667-f1.eps}{Flux calibrated Boller \& Chivens spectra of V1965~Cyg.}

\IBVSfig{10cm}{4667-f2.eps}{H$\alpha$ order in the Echelle spectrum of V1965~Cyg (Nov 13, 1997).}
 
\vspace{-22pt}
The low-resolution spectra of V1965~Cyg are shown in Fig.~1 and the
H$\alpha$ order of the high-resolution one in Fig.~2. Both high- and
low-resolution spectra show absorption lines and bands of a carbon
star. In the Boller \& Chivens spectra the strongest absorption
feature is the blend of the NaI resonance doublet at 5889.953\,\AA\ and
5895.923\,\AA\@. The most remarkable change in the low-resolution spectra
of V1965~Cyg is the H$\alpha$ that was in emission in 1994 and 1997 and
absent in 1995. When the H$\alpha$ was not in emission, the carbon
absorption features retraced and the continuum appeared smoother. The
integrated H$\alpha$ flux is $1.7\times 10^{-13}$ on the Dec.\ 10, 1994
spectrum and $1.3\times 10^{-13}$~erg\,cm$^{-2}$\,s$^{-1}$ on the
Nov.\ 20, 1997 one.

The high-resolution spectrum of V1965~Cyg shows a sharp and moderate
intensity H$\alpha$ emission line with a  symmetrical profile, whose
FWHM is $\sim$0.9\,\AA\ (the FWHM of the instrumental PSF on night-sky
lines is $\sim$0.3\,\AA) and the heliocentric radial velocity is
$-$54.0\,km\,s$^{-1}$.

Our observations are indeed not enough to address the issue on the
nature of V1965 Cyg. They however document remarkable spectroscopic
changes (affecting both the emission lines and the continuum) that
could motivate a long term devoted photometric and spectroscopic
monitoring. If the photometric behavior should not match that of a
pulsating variable, the presence of H$\alpha$ in emission and its large
variability could suggest an interacting binary nature for V1965~Cyg.

\references

Alksnis, A., Eglite, M., Platais, I., 1990, {\it IBVS}, No.\,3418

Kazarovets, E.V., Medvedeva, G.I., Samus, N.M., 1990, {\it Astron.\ Tsirk.}, No.\,1543

Stephenson, C.B., 1973, {\it Publ.\ of the Warner and Swasey Observatory}, {\bf 1}, No.\,4

Stephenson, C.B., 1989, {\it Publ.\ of the Warner and Swasey Observatory} {\bf 3}, No.\,2

\end{document}
