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\IBVShead{4118}{29 November 1994}                      % Use it with dummy or empty arguments

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\centerline{\ft 35 NEW BRIGHT MEDIUM- AND HIGH-  AMPLITUDE VARIABLES}
\centerline{\ft DISCOVERED BY THE TYCHO INSTRUMENT}
\centerline{\ft OF THE HIPPARCOS SATELLITE\footnote{Based on observations 
made with the ESA Hipparcos satellite}}

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\begintext


The HIPPARCOS project will discover a large number of hitherto unknown
variable stars, as a side result of a primarily astrometric satellite
(for a description see Perryman, 1989, and references therein).  The
HIPPARCOS main instrument is expected to detect low-amplitude
variability in several 10 000 stars, while the TYCHO instrument will
scan 1 million stars down to about B=12 for medium- to high-amplitude
variations.  The four-year lifetime of the satellite ended in August
1993.  The reduced data, including the individual photometric
measurements of all observed stars, will become available to the
general astronomical community in 1997.

Here we present a small list of new bright medium- to high-amplitude
variables that became obvious during routine astrometric processing of
the TYCHO data. All were checked for known counterparts in the General
Catalogue of Variable Stars (GCVS), in the New Catalogue of Suspected
Variables (NSV), and in the five name lists of newly designated
variable stars issued since 1985 (IBVS 2681, 3058, 3323, 3530, 3840).
Ground-based follow-up observations are encouraged to clarify the
nature of the stars and to assess the quality of these preliminary
TYCHO results. The amplitudes (as observed by TYCHO) are mostly above
0.5 magnitude, with 6 of them exceeding 1 magnitude.

The 35 new variables are listed in Table 1.  The columns of the table
contain, in turn: the designation of the star in the Space Telescope
Guide Star Catalogue, the J2000 position, the observed range of
variability in the T magnitude (defined below) and remarks.  For each
of the stars there are of the order of 100 TYCHO observations in two
wavelength bands (close to B and V, respectively).  Nevertheless light
curve classification from these data is very difficult because the
observations are extremely unevenly distributed in time.  Table 1
therefore gives only rough indications on the character of the
variability.

Among the 35 stars in Table 1 there are six NSV stars (indicated in
the remarks column).  The TYCHO measurements thus confirm the
suspected variability of these objects.



Figures 1 and 2 show the observed light curves for two of the NSV
objects as an illustration of the TYCHO data. The T magnitude is a
broad-band optical magnitude derived from the sum of the photon counts
in the TYCHO B and TYCHO V photometric channels, under the condition
that T=B=V if B-V=0. See Halbwachs et al., 1992, for more details.

Acknowledgements:
This work was supported by Bundesministerium f\" ur Forschung und
Technologie, Deutsche Agentur f\" ur Raumfahrtangelegenheiten (DARA),
Projects 500092020 and 500091060, and by the Danish Space Board. The
results presented here are based on the collaborative effort of the
HIPPARCOS and TYCHO scientists and engineers, scattered all over
Europe.
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\centerline{2}
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\centerline{Table 1. Results on the 35 new variables}
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\small
%\hbox to 13cm {
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\begin{tabular}{rrrcrl}
\hline
GSC/TIC\ Id&R.A.\,2000&Dec.\,2000&T(max)&T(min)&Remarks\\
\hline
\\
8468 \ 104&0\fh 20\fmm 20\fss 2&$-$57\degr 9'48''&9.37&10.66& \\
2345 1896&3 19 01.5&32 41 16&7.90&8.33& \\
8503 \ 158&3 37 44.6&$-$55 23 47&8.67&10.13&NSV\,1214\\
7572 1544&3 44 18.7&$-$41 53 52&8.22&8.99&350 days period?\\
3347 1499&4 48 15.4&47 16 29&9.24&9.77& \\
3738 \ 234&5 06 31.7&55 21 13&7.73&8.51&periodic, 90 days\\
2910 \ 447&5 31 26.8&38 19 11&7.54&8.23& \\
709\,\ \ \ 46&5 32 54.5&13 03 07&9.04&9.69&NSV\,2106\\
3378 \ 458&6 10 21.3&47 44 22&8.16&8.67& \\
6513 1712&6 16 01.9&$-$27 30 34&8.29&9.44& \\
7102 1296&7 05 13.9&$-$35 56 23&7.42&8.31&NSV\,3379\\
8143 1629&7 56 20.9&$-$49 58 55&8.38&9.69& \\
7132 \ 590&8 01 32.9&$-$37 11 50&8.06&8.60&400 days period?\\
8155 \ 343&8 38 01.0&$-$46 54 16&7.89&9.35&NSV\,4166\\
8585 1054&9 36 14.7&$-$52 32 41&8.13&8.98&360 days period?\\
7729 \ 173&11 02 13.9&$-$41 06 51&7.14&7.55& \\
8212 1230&11 04 31.4&$-$51 13 19&8.43&10.00&SRb type?\\
5511 \ 693&11 15 23.6&$-$11 35 17&7.62&7.96&periodic?\\
8653 1082&13 14 08.3&$-$54 41 35&8.59&9.15& \\
1466 \ 869&13 43 59.2&21 49 05&8.81&9.73& \\
2549 \ 677&14 15 58.3&34 26 15&8.91&9.53& \\
6199 \ 618&15 56 40.1&$-$22 01 40&8.85&9.83&NSV\,7344, R\,CrB type?\\
7850 1060&15 57 59.7&$-$43 57 49&8.94&10.07&NSV\,7357\\
353 \ 301&15 59 05.8&0 35 45&7.51&8.2&eclipsing?\\
8710 1370&16 01 36.3&$-$54 08 36&8.67&9.28& slowly variable\\
7362 \ 894&17 15 15.5&$-$30 32 14&8.77&9.38& \\
8353 \ 620&17 21 04.6&$-$51 07 14&9.47&10.73& \\
6306 \ 417&19 30 09.6&$-$19 23 08&8.74&9.28& \\
5153 \ 387&19 41 07.6&$-$03 55 10&8.38&9.05& \\
8782 \ 316&19 43 13.7&$-$56 15 36&8.25&8.65& \\
1089 \ 751&20 46 49.3&7 33 11 &8.64&9.12&eclipsing?\\
7987 \ 835&21 25 28.4&$-$41 42 07&8.26&8.98&periodic?\\
7990 \ 374&21 54 22.3&$-$41 15 58&8.59&9.36& \\
8827 \ 195&22 57 05.8&$-$57 24 04&7.68&8.71& \\
8833 1050&23 44 19.2&$-$54 26 10&8.12&8.74& \\
\hline
\end{tabular}
\end{center}
\large
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\centerline{\epsffile{4118-f1.ps}}
\noindent Figure 1: TYCHO light curve of GSC 8155 343 = NSV 4166. All raw observations
of the star by TYCHO are shown. The different symbols denote different
apertures of the instrument.  The T magnitude is defined in the text.
The strong clumping of the points is an unavoidable consequence of
the (primarily astrometric) measuring schedule of the HIPPARCOS
satellite. The scatter of the points within each clump is due to
the random measurement errors. They will be somewhat smaller after 
the final photometric reduction of the TYCHO data. The variability
of this suspected variable is confirmed by the data shown here.

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\centerline{3}
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\centerline{\epsffile{4118-f2.ps}}
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\centerline{Figure 2: TYCHO light curve of GSC 6199 618 = NSV 7344. Same remarks as for Figure 1}


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% Call for macros \authors - \authorsrightcol - \endauthors
\beginauthors
\authorsrightcol
Valeri MAKAROV $^{(1)}$, 
Ulrich BASTIAN $^{(2)}$,
Erik HOEG $^{(1)}$, 
Volkmar GROSSMANN $^{(3)}$,
Andreas WICENEC $^{(3)}$
\vskip 2mm
$^{(1)}$ Copenhagen University Observa\-  
\ \ \ \ tory, Copenhagen, Denmark
$^{(2)}$ Astronomisches Rechen-Institut, 
\ \ \ \ Heidelberg, Germany
$^{(3)}$ Astronomisches Institut 
\ \ \ \ der Universitaet, Tuebingen, 
\ \ \ \ Germany
\endauthors

% Call for macro \references
\references

Halbwachs, J.-L. et al., 1992, {\it Astron. Astrophys.}, {\bf 285}, 193

Perryman, M.A.C., 1989, {\it Nature}, {\bf 340}, 111



\end{document}





% Table 1: 35 new variables
% _________________________
% 
% 
%  GSC number     R.A. 2000   Dec. 2000   T(max) T(min) Remarks
% 
%  8468   104     0 20 20.2   -57  9 48    9.37  10.66
%  2345  1896     3 19  1.5    32 41 16    7.90   8.33
%  8503   158     3 37 44.6   -55 23 47    8.67  10.13 NSV 1214
%  7572  1544     3 44 18.7   -41 53 52    8.22   8.99 350 days period?
%  3347  1499     4 48 15.4    47 16 29    9.24   9.77
%  3738   234     5  6 31.7    55 21 13    7.73   8.51 periodic, 90 days
%  2910   447     5 31 26.8    38 19 11    7.54   8.23
%   709    46     5 32 54.5    13  3  7    9.04   9.69 NSV 2106
%  3378   458     6 10 21.3    47 44 22    8.16   8.67
%  6513  1712     6 16  1.9   -27 30 34    8.29   9.44
%  7102  1296     7  5 13.9   -35 56 23    7.42   8.31 NSV 3379
%  8143  1629     7 56 20.9   -49 58 55    8.38   9.69
%  7132   590     8  1 32.9   -37 11 50    8.06   8.60 400 days period?
%  8155   343     8 38  1.0   -46 54 16    7.89   9.35 NSV 4166
%  8585  1054     9 36 14.7   -52 32 41    8.13   8.98 360 days period?
%  7729   173    11  2 13.9   -41  6 51    7.14   7.55
%  8212  1230    11  4 31.4   -51 13 19    8.43  10.00 SRb type?
%  5511   693    11 15 23.6   -11 35 17    7.62   7.96 periodic?
%  8653  1082    13 14  8.3   -54 41 35    8.59   9.15
%  1466   869    13 43 59.2    21 49  5    8.81   9.73
%  2549   677    14 15 58.3    34 26 15    8.91   9.53
%  6199   618    15 56 40.1   -22  1 40    8.85   9.83 NSV 7344, R CrB type?
%  7850  1060    15 57 59.7   -43 57 49    8.94  10.07 NSV 7357
%   353   301    15 59  5.8     0 35 45    7.51   8.2  eclipsing?
%  8710  1370    16  1 36.3   -54  8 36    8.67   9.28 slowly variable
%  7362   894    17 15 15.5   -30 32 14    8.77   9.38
%  8353   620    17 21  4.6   -51  7 14    9.47  10.73
%  6306   417    19 30  9.6   -19 23  8    8.74   9.28
%  5153   387    19 41  7.6   -03 55 10    8.38   9.05
%  8782   316    19 43 13.7   -56 15 36    8.25   8.65
%  1089   751    20 46 49.3     7 33 11    8.64   9.12 eclipsing?
%  7987   835    21 25 28.4   -41 42  7    8.26   8.98 periodic?
%  7990   374    21 54 22.3   -41 15 58    8.59   9.36
%  8827   195    22 57  5.8   -57 24  4    7.68   8.71
%  8833  1055    23 44 19.2   -54 26 10    8.12   8.74
% 
