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\IBVShead{5281}{27 May 2002}

\IBVStitle{EUVE~J2244$-$15.9: A New Spectroscopic Binary}

\IBVSauth{Christian, Damian J.$^1$; Mathioudakis, Mihalis$^2$; Vennes, Steph\'ane$^3$}

\IBVSinst{Department of Physics \& Astronomy, Johns Hopkins University, 3400 N. Charles Ave., Baltimore MD, 21218; e-mail: damian@pha.jhu.edu}
\IBVSinst{Queens University of Belfast, Belfast, UK}
\IBVSinst{Astrophysical Theory Centre, Australian National University, Canberra, ACT 0200, Australia}

\SIMBADobjAliasJ2000{EUVE J2244-15.9}{HD 215341}{22 44 38 -15 56 32}

\IBVSabs{We report the detection of a new late-type spectroscopic binary, }
\IBVSabs{EUVE J2244$-$15.9 (HD 215341) using the 0.6 meter Coude }
\IBVSabs{auxiliary telescope and Hamilton echelle spectrograph at Lick observatory.}


\begintext

Over 40\% of the sources in EUV surveys have been
identified as late-type stars (e.g. the Second EUVE Catalog; 
Bowyer et al. 1996; ROSAT 2RE catalog, Pye et al. 1995). 
EUVE J2244$-$15.9 (HD 215341) was discovered as a spectroscopic binary
 in our optical observations
of late-type stars selected from EUVE all-sky survey catalogs,
including the Lampton et al. (1997) catalog
of fainter EUVE all-sky sources jointly detected with the ROSAT PSPC.
The Lampton et al. catalog concentrated on detections in
the EUVE Lexan band which is centered on 100 \AA.

Our optical observations were searching for chromospheric activity
indicators, such as Ca II H\&K and H$\alpha$ in emission in a sample
of EUV-selected late-type stars.  
We observed EUVE~J2244$-$15.9 for 1 hour on 5 and 6 of August 1997  
using the 24 inch coud\'e auxiliary telescope (CAT) and the Hamilton 
echelle spectrograph (Vogt 1987) at Lick observatory. We used a 2048 $\times$ 2048 
CCD binned 2 $\times$ 2 with a dispersion of 0.033 \AA/pixel at Ca H and K and 
0.054 \AA/pixel at H$\alpha$; the resulting velocity resolution is 7.5~km/s.
Spectra were wavelength-calibrated with Th-Ar spectra and flat-fielded 
with quartz lamps. 
The observation log and line emission equivalent widths (eqw) 
from both components are presented in Table~1.

\centerline{Table 1. EUVE J2244$-$15.9 Log }
\vskip 3mm
\begin{center}
\begin{tabular}{lc}
\hline
RA (J2000) &  21 44 38 \\
Dec (J2000)   &    $-$15 56 32 \\
m$_v$ & 9.3 \\
Sp. Type & dK1/2e \\
Obs. dates:  & 05/08/97 10:31:48 UT \\
 & 06/08/97 09:39:22 UT \\
Exp. (sec) &  3600 ($\times$2) \\
Ca K (eqw)    & 4.0  \AA  \\
Ca H (eqw)    & 2.1   \AA \\
H$\alpha$ (eqw)   & 0.4  \AA \\
EUVE Lexan cts/s & 0.028 \\
EUVE Obs. Flux & 3.9$\times10^{-12}$ \\
 &(ergs cm$^{-2}$ sec$^{-1}$) \\
\\
\hline
\end{tabular}
\end{center}

The optical spectrum of EUVE J2244$-$15.9 
clearly shows the tell-tale signs of emission lines
from a spectroscopic binary. 
We show a Ca H\&K and H$\alpha$ spectra in Figure 1.
We calculated the observed flux using a coronal emissivity model 
with log(T) = 6.8 as described in 
Mathioudakis et al. (1995). We then calculated a measure of
the coronal efficiency, $L_{euv}/L_{bol}$.
We find EUVE J2244$-$15.9 with $L_{euv}/L_{bol} \approx 10^{-3}$, and
this is at the upper end of active
late-type stars found in the EUVE and ROSAT all-sky surveys (e.g.
Christian and Mathioudakis 2002; Jeffries \& Jewell 1993).
EUVE J2244$-$15.9 merits further observations as a coronally active
late-type binary.


\vspace*{-2.7cm}

\IBVSfig{14cm}{5281-f1.eps}{Ca H\&K and H$\alpha$ spectra of spectroscopic binary,
EUVE J2244$-$15.9 (flux in units of 10$^{-13}$~ergs cm$^{-2}$ sec$^{-1}$ \AA$^{-1}$).
({\it Top}) panel shows Ca~K on left and Ca~H on right from 
the August 06 observation. ({\it Bottom}) 
panel shows the H$\alpha$ spectra from August 05 and 06 August (upper H$\alpha$ spectrum scaled
by a factor of 1.5).}


\references

Bowyer, S. et al., 1996, {\it ApJS}, {\bf 102}, 129 

Christian, D.~J., \& Mathioudakis, M., 2002, {\it AJ}, {\bf 123}, 2796 

Jeffries, R.~D., \& Jewell, S.~J., 1993, {\it MNRAS}, {\bf 264}, 106 

Lampton, M. et al., 1997, {\it ApJS}, {\bf 108}, 545 

Mathioudakis, M. et al., 1995, {\it A\&A}, {\bf 300}, 775 

Pye, J. P., et al., 1995, {\it MNRAS}, {\bf 274}, 1165 

Vogt, S., 1987, {\it PASP}, {\bf 99}, 1214 

\endreferences


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