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\IBVShead{4743}{6 August 1999}

\IBVStitle{LS {\sc ii} $+$22$\deg$8 -- a newly recognized classical B\lowercase{e} star}

\IBVSauth{A.S. Miroshnichenko$^1$, K.S. Kuratov$^2$, T.A. Sheikina$^2$, D.B. Mukanov$^3$}

\IBVSinst{Ritter Observatory, Dept. of Physics \& Astronomy, University of
Toledo, Toledo, OH, 43606, USA, e-mail: {\tt anatoly@physics.utoledo.edu}}

%\IBVSinst{Pulkovo Observatory, 196140, Saint-Petersburg, Russia}

\IBVSinst{Fesenkov Astrophysical Institute, Kamenskoye plato, 480068,
Almaty, Kazakhstan}

\IBVSinst{Al-Farabi Kazakh National University, 480000, Almaty, Kazakhstan}

\IBVStyp{ Be star }
\IBVSkey{photometry, spectroscopy}
\SIMBADobj{LS {\sc ii} $+22\deg$8}

\begintext
LS {\sc ii} $+22\deg$8 was discovered by Stock et al. (1960) as a possible
luminous early-type star with emission in the H$\alpha$ line. Later it was
listed in the Henize (1976) catalog of emission-line stars as Hen 1764.
Pesch (1963) estimated its spectral type as B9 {\sc i}a or B2--5 {\sc v}
(with less likelihood) from his $UBV$ photometry (see Table 1), which also
implies the interstellar extinction $A_V \sim 2\fmm0$ assuming no circumstellar
contribution. Allen (1973) obtained near-IR photometry of the star ($H=9\fmm90,
K=9\fmm60$). These data indicate a very weak near-IR excess radiation (see
Fig. 1) taking into account the above $A_V$, a total-to-selective interstellar
extinction ratio, $R=$3.1, and intrinsic color-indices for the above spectral
types (Strajzhys 1977). This excess can be explained by free-free emission of
the circumstellar gas or of a faint cool companion.
Its weakness and shape (E$_{V-K} \sim 0\fmm2$, dereddened $H-K = 0\fmm15$)
rules out the presence of hot dust around the star.

Dong \& Hu (1991) identified LS {\sc ii} $+22\deg$8 with the IRAS PSC source
19381$+$2224. However, the IRAS fluxes detected at 12, 25, and 60 $\mu$m
(10.43, 7.10, and 3.64 Jy respectively) imply a very strong flux rise between
2 and 12 $\mu$m, which is inconsistent with the assumption about a late-type
companion (see Fig. 1). Such a rise might be due to the radiation of dust with
the highest temperature of nearly 300--500 K. Moreover, a steep decrease of
these IRAS fluxes with wavelength is consistent with either a small
extent of the dusty structure or with a different illuminating source for
the dust. The first suggestion along with the absence of the hot dust leads
to a conclusion that the dust is concentrated in a rather thin remote
shell, while the second one points that either the optical object is a
binary system or it is not associated with the IRAS source.

Th\'e et al. (1994) pointed out that there is a 54$\arcs$ offset
between the optical position of LS {\sc ii} $+22\deg$8 and that of the
IRAS source. This is well outside the IRAS positional error
ellipse, which has major axes of 22$\arcs$ and 5$\arcs$ and a position
angle of 70$\deg$. A faint star, that is located very close to the
position of IRAS 19381$+$2224, is seen in the Space Telecope Institute
Digital Sky Survey image of a field around LS {\sc ii} $+22\deg$8.
It seems to be a more appropriate optical counterpart of this IRAS source.
The mid-IR spectrum of IRAS 19381$+$2224 taken by the IRAS Low-Resolution
Spectrometer (LRS) shows a weak emission feature at 11.3 $\mu$m (Olnon et
al. 1986), which is probably due to the SiC dust particles usually
observed in the spectra of carbon stars. Therefore, LS {\sc ii} $+22\deg$8
and IRAS 19381$+$2224 are most likely different sources.

The simultaneous $UBVRI$ observations of LS {\sc ii} $+22\deg$8 in the Johnson
photometric system were obtained with two 1-meter telescopes at the Assy and
Tien-Shan Observatories of the Fesenkov Astrophysical Institute in Kazakhstan
equipped with a two-channel photometer-polarimeter (Bergner et al. 1988)
between June 1993 and August 1998 through the 26$\arcs$ diaphragm (Table 1).
Its brightness varies with an amplitude of $\sim 0\fmm$3 in the $VRI$-bands,
while it reaches 0$\fmm$6 in the $U$-band. Such a behaviour might be due
to free-bound emission of the circumstellar gas which gives the
strongest contribution shortward of the Balmer jump and manifests itself by
the peculiar spectrum (see below). The averaged color-indices $U-B$ and $B-V$
are consistent with those of a reddened B8$\pm$1 giant or dwarf ($A_V =
2.3\pm0\fmm2$, $R=$3.1), which displays an excess radiation longward of 0.5
$\mu$m. The latter increases from about 0$\fmm$1 in the $R$-band to 0$\fmm$4
in the $K$-band (according the data by Allen 1973). It can be explained by
free-free emission of the envelope as in classical Be stars (e.g.\ Dougherty
et al. 1991).

\vskip 11pt

\centerline{Table 1. Photometric observations of LS {\sc ii} $+22\deg$8.}
\begin{center}
\begin{tabular}{cccccc}
\hline
\noalign{\smallskip}
JD 2400000+& $V$  & $U-B$ & $B-V$ & $V-R$ &$R-I$ \\
\noalign{\smallskip}
\hline
\noalign{\smallskip}
$^{\rm a}$ &11.78 &0.37  &0.54  &      &     \\
49165.39   &12.04 &0.38  &0.68  &0.69  &0.41 \\
49232.33   &12.05 &0.27  &0.70  &0.66  &0.45 \\
49612.14   &11.97 &0.20  &0.72  &0.58  &0.32 \\
49942.28   &11.95 &0.21  &0.57  &0.69  &0.36 \\
49944.26   &11.81 &0.43  &0.63  &0.58  &0.34 \\
49960.20   &12.02 &0.17  &0.59  &0.69  &0.36 \\
51043.28   &11.74 &0.09  &0.54  &0.61  &0.45 \\
51052.25   &11.73 &0.11  &0.57  &0.58  &0.40 \\
\noalign{\smallskip}
\hline
\end{tabular}
\end{center}
\begin{list}{}
\item $^{\rm a}$ data from Pesch (1963)
\end{list}

\vskip 11pt

The spectroscopic observations were obtained at the 6-meter telescope of
the Russian Academy of Sciences with a photoelectric TV-scanner (Balega et
al. 1979) on 1993 July 10 in the spectral regions 3933--4960 and 5852--6900
\AA\ with a resolution of 2 \AA.
The most prominent features in the spectrum are a double-peaked H$\alpha$
emission (Fig. 2) and Fe {\sc ii} absorption lines. The H$\beta$ line is mostly
filled in with emission, while H$\gamma$ and H$\delta$ show only weak signs of
it. Other emission lines, which are seen in the spectrum, can be identified
with Fe {\sc i} transitions, usually blends of several lines.
The Na {\sc i} D$_{1,2}$ and Si {\sc ii} 6347 and 6371 \AA\ absorption lines
certainly contain circumstellar contribution as their
equivalent width ratios are different from those of pure interstellar and
photospheric, 1.33 and 1.22, respectively.
The observed diffuse interstellar bands at 6278 and 6283 \AA\ are rather
strong and are consistent with the reddening derived above from the
photometric data.

The strong influence of the circumstellar material makes it difficult to
estimate the MK type of the star from our spectral data. The observed H$\delta$
line wings are consistent with the theoretical ones for the temperatures not
higher than 12000 K, that corresponds to a B8 spectral type. Since the
H$\alpha$ emission line is not very strong and hardly affects the Balmer jump
(Doazan 1982), we can assume that our photometric estimate of the object's MK
type is correct.

The H$\alpha$ line profile and strong Fe {\sc ii} absorption lines are
similar to those of classical Be-shell stars, where they are formed in a
dense circumstellar disk viewed at a high inclination angle (close to
edge-on, Hanuschik 1994). The observed ratio of the H$\alpha$
peak intensities $V/R > 1$ is also seen in many classical Be
stars and is thought to be due to rotating one-armed density waves in the
disk (e.g.\ Okazaki 1991). The optical brightening accompanied
with the blueing observed in August 1998 (two last lines in Table 1)
may be due to the shell strengthening, which is usual for classical Be stars
(e.g.\ Doazan 1982).

\IBVSfig{8.5cm}{4743-f1.ps}{
The dereddened SEDs of LS {\sc ii} $+22\deg$8
constructed from the averaged $UBVRIHK$ photometric data (filled circles)
along with that of IRAS 19381$+$2224 (filled squares -- IRAS photometry,
crosses -- IRAS LRS spectrum). A Kurucz (1994) model atmosphere for
T$_{\rm eff}$ = 12000 K and log $g$ = 3.5 is shown by a solid line.}

\IBVSfig{8.5cm}{4743-f2.ps}{The H$\alpha$ line profile in the spectrum of
LS {\sc ii} $+22\deg$8. The heliocentric velocity is given in km\,s$^{-1}$,
the intensity is normalized to the continuum.}

The separation between the H$\alpha$ emission peaks, 290$\pm$60 km\,s$^{-1}$,
implies a rotational velocity of the envelope of at least 100 km\,s$^{-1}$
if one assumes that rotation is the main mechanism of the line formation.
Subtraction of the photospheric profile from the observed H$\beta$ line profile
reveals a double-peaked emission similar to that in the H$\alpha$ line.

If we suggest a typical luminosity of a late B-type classical Be star for the
object, log L$_{\rm bol}$/L$_{\odot} \sim$ 2.5 (e.g.\ Zorec \& Briot 1991),
a distance of $\sim$ 2 kpc can be derived.
An assumption that the object is a supergiant is not consistent with the
derived spectral type and intrinsic color-indices of the star. Furthermore,
the presence of a disk-like gaseous envelope is a feature of B[e]
supergiants (Zickgraf et al. 1986), which also exhibit a strong
near-IR excess not seen in LS {\sc ii} $+22\deg$8. Balmer line profiles
similar to those of the object also display pre-main-sequence Herbig
Ae/Be stars (Finkenzeller \& Mundt 1984). However, such a strong
emission-line spectrum in these stars is usually acompanied by a
noticeable near-IR excess that rules out the pre-main-sequence nature
of LS {\sc ii} $+22\deg$8. The collected observational data do not
allow us to consider other possible options (e.g., binary system with
different types of the secondary component).

Thus, both photometric and spectroscopic properties of LS {\sc ii}
$+22\deg$8 suggest that it is most likely a classical Be-shell star.
Its emission in the H$\alpha$ line is one of the strongest among
those of Be stars with nearly similar spectral types. It is similar to that of
Pleione during its shell phase (Doazan 1982). New photometric
and spectroscopic variations of LS {\sc ii} $+22\deg$8 are, therefore,
expected in the future. The IRAS source 19381$+$2224 is most likely
associated with a cool nearby star.

\references
Allen, D.A., 1973, {\it MNRAS}, {\bf 161}, 145

Balega, I.I., Vereschagina, R.G., Markelov, S.V., et al., 1979, {\it Izvestia
Spec. Astroph. Obs.}, {\bf 11}, 248

Bergner, Yu.K., Bondarenko, S.L., Miroshnichenko, A.S., et al., 1988,
{\it Izvestia Glavn. Astron. Obs. v Pulkove}, {\bf 205}, 142

Dong, Y.S., Hu, J.Y., 1991, {\it Chin. A\&A}, {\bf 15}, 275

Doazan, V., 1982, in {\it The B Stars with and without Emission Lines},
 A.B. Underhill, V. Doazan (eds.), NASA SP-456

Dougherty, S.M., Taylor, A.R., Clark, T.A., 1991, {\it AJ}, {\bf 102}, 1753

Finkenzeller, U., Mundt, R., 1984, {\it A\&AS}, {\bf 55}, 109

Hanuschik, R.W., 1994, {\it IAU Symp.}, {\bf 162}, 358, (eds.) L.A. Balona,
H.F. Henrichs, and J.M. Le Contel, Kluwer Acad. Publ.
%Changed: Wed Jun 15 10:33:22 MEST 2005

Henize, K.G., 1976, {\it ApJS}, {\bf 30}, 491

Kurucz, R.L., 1994, {\it Smithsonian Astrophys. Obs.}, CD-ROM No. 19

Okazaki, A.T., 1991, {\it PASJ}, {\bf 43}, 75

Olnon, F.M., Raymond, E., and IRAS Science Team, 1986, {\it A\&AS}, {\bf 65},
607

Pesch, P., 1963, {\it ApJ}, {\bf 137}, 547

Stock, J. et al., 1960, Luminous Stars in the Northern Milky Way, Part {\sc ii}

Strajzhys, V., 1977, in {\it Multicolor Photometry of Stars}, Vilnius, Mokslas

Th\'e, P.S., de Winter, D., P\'erez, M.R., 1994, {\it A\&AS}, {\bf 104}, 315

Zickgraf, F.-J., Wolf, B., Stahl, O., et al., 1986, {\it A\&A}, {\bf 163}, 119

Zorec, J., Briot, D., 1991, {\it A\&A}, {\bf 245}, 150


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