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\IBVShead{4315}{5 April 1996}

\centerline{\ft NEW DEEP MINIMUM OF THE CATACLYSMIC BINARY KR Aur}
\centerline{\ft IN 1994-1995}
\vskip 8mm

\begintext

 KR Aur, whose variability was discovered by Popova (1960), is a member of the nova-like subclass, known as anti-dwarf novae.
 Its spectroscopic observations revealed that it is a close
 binary system, consisting of a white dwarf (0.7 M$_\odot$) and a red
 dwarf  (0.48 M$_\odot$) with orbital period of 3.907 hours and inclination
 angle smaller than 40 degrees (Shafter, 1983).
 The brigthness of KR Aur is usually between 12-14\fmm\ (predominant value
13\fm 5), with occasional decreases to 15\fm 5, but it drops to 18\fmm\ episodically. Rapid variations with amplitude up to 0\fm 4 and time-scales
seconds and minutes (flickering) are typical for the star in its
bright state. The last deep minimum was observed in 1981-1982, when
the star dropped to approximately 17\fmm\ (Popov, 1982; Popova et al., 1982).

 We present photometric and spectral observations of KR Aur in the period
September 1993-November 1995.

 The photometric observations were carried out through B-filter, using 60cm
Cassegrain telescopes with identical one-channel photoelectric photometers at
the National Astronomical Observatory - Rozhen (NAO) and at the Astronomical
Observatory - Belogradchik (AOB), and the 50/70cm Schmidt telescope at NAO with
ZU 21 plates and B-filter. The integration time was 10 seconds and the exposure
time was 20 minutes for all observations, respectively.
 The magnitudes of the variable were estimated on the basis of the standards,
published by Popova (1965). The accuracy was $\le$0\fm 1 for the
photoelectric observations and $\le$0\fm 3 for the photographic ones.
U-monitoring for flickering search was carried out for 8 nights. The
observational data are presented in Table 1 and Figure~1.

One spectrum with 4 \AA\ resolution was obtained on February 9, 1994 in the region
3460 - 5470 \AA\ (Figure 2). The 6m telescope of the Special Astrophysical
Observatory of the Russian Academy of Sciences with 1000 channel  TV-scanner
was used (Afanas'ev et al., 1991). The data processing was done by means of
the package ETAM (Knyazev \& Lipovetskii, 1994).

 Our observations revealed that KR Aur underwent a minimum again.
We think a pre-drop state of the star has appeared since January
1994. The star displayed an unstable brightness -- from 13\fm 8 in
December 1993 to 14\fm 6 on January 20, 1994 (Antov \& Popov, 1994). On January,
1994 KR Aur was fainter than 15\fmm. In all observations up to January 20, 1994
flickering was present, however, on January 22, 1994 it seems to be absent. The
last measurement is a little bit uncertain, because the object was too faint
then.

 An interesting fact is that in the beginning of February 1994 KR Aur increased
its brightness to maximum light  again (13\fm 1 average value) and our
estimates showed fast changes in B-light up to 0\fm 42 amplitude.
 Our measurements in this period are in an agreement with the visual estimates
of Verdenet \& Mizner (1994).

\vfill \eject

\centerline{2}
\vskip 1mm
\centerline{Table 1}
\begin{center}
\begin{tabular}{llllll}
\hline

    Date &         H.J.D.&       m$_B$& Obs.&Telescope&        Flickering\\
         &        (2440000+)&                         &                  \\
 \hline
\\
21/22.09.1993&     9252.544&    13.2 &  AOB& Cassegrain    &     \\
22/23.09.1993&     9253.549&    13.0 &  AOB& Cassegrain            &     \\
23/24.09.1993&     9254.541&    12.9 &  AOB& Cassegrain            &  Yes\\
27/28.10.1993&     9288.510&    13.3 &  AOB& Cassegrain            &     \\
17/18.12.1993&     9339.467&    13.8 &  AOB& Cassegrain            &     \\
18/19.12.1993&     9340.458&    14.0 &  AOB& Cassegrain            &     \\
19/20.12.1993&     9341.429&    13.9 &  AOB& Cassegrain            &  Yes\\
19/20.01.1994&     9372.526&    14.6 &  NAO& Cassegrain            &  Yes\\
22/23.01.1994&     9375.385&    $\ge $ 15&  NAO& Cassegrain         &  No?\\
01/02.02.1994&     9385.260&    13.1 &  NAO& Cassegrain            &     \\
01/02.02.1994&     9385.265&    13.1 &  NAO& Cassegrain            &     \\
01/02.02.1994&     9385.271&    12.8 &  NAO& Cassegrain            &     \\
03/04.02.1994&     9387.381&    13.2 &  NAO& Cassegrain            &     \\
03/04.02.1994&     9387.389&    13.4 &  NAO& Cassegrain            &     \\
03/04.02.1994&     9387.397&    13.0 &  NAO& Cassegrain            &     \\
04/05.02.1994&     9388.400&    12.8 &  NAO& Cassegrain            &     \\
04/05.02.1994&     9388.408&    13.2 &  NAO& Cassegrain            &     \\
04/05.02.1994&     9388.415&    13.0 &  NAO& Cassegrain            &     \\
10/11.03.1994&     9422.316&    14.7 &  AOB& Cassegrain            &     \\
12/13.03.1994&     9424.317&    14.7 &  AOB& Cassegrain            &  No \\
15/16.03.1994&     9427.293&    15.2 &  AOB& Cassegrain            &  No \\
13/14.04.1994&     9456.292&    14.0 &  AOB& Cassegrain            &     \\
14/15.04.1994&     9457.316&    14.3 &  AOB& Cassegrain            &     \\
09/10.10.1994&     9635.484&    14.7 &  AOB& Cassegrain            &     \\
12/13.10.1994&     9638.489&    14.6 &  AOB& Cassegrain            &     \\
15/16.10.1994&     9641.490&    14.4 &  AOB& Cassegrain            &     \\
04/05.12.1994&     9691.492&    15.0 &  AOB& Cassegrain            &  No \\
28/29.12.1994&     9715.304&    14.9 &  NAO& Cassegrain            &     \\
02/03.02.1995&     9751.519&    15.5 &  NAO& Schmidt  &     \\
01/02.03.1995&     9778.416&    18.1:&  NAO& Schmidt  &     \\
27/28.09.1995&     9988.585&    18:  &  NAO& Schmidt  &     \\
19/20.10.1995&    10010.508&    19:  &  NAO& Schmidt  &     \\
24/25.11.1995&    10046.692&    14.5:&  NAO& Schmidt  &     \\
25/26.11.1995&    10047.477&    14.8 &  AOB& Cassegrain            &  Yes\\
\hline
\end{tabular}
\end{center}
\vfill \eject

\centerline{3}
\epsfysize=8cm
\centerline{\epsffile{4315-f1.ps}}
\normalsize
\begin{center}
Figure 1. The photometric behaviour of KR Aur. ``Y" denotes presence of
flickering with amplitude $\ge$0\fm 15, ``N" - absence of it.
\end{center}
\large
\epsfysize=8cm
\centerline{\epsffile{4315-f2.ps}}
\normalsize
\begin{center}
Figure 2. The spectrum of KR Aur, obtained on February 9, 1994 with the 6m
telescope of the Special Astrophysical Observatory.
\end{center}
\large

\vskip 3mm
 
 In a month the star dropped again to 14\fm 7. Its spectrum, obtained on
 February 9, 1994 is closer in time to the maximum light state, and resembles
 those observed with the same equipment by Popov \& Kraitcheva (1990). The
detected  Balmer emission lines -- H$_\beta$, H$_\gamma$, H$_\delta$
and H$_\epsilon$ -- have a two-component structure with a redward-shifted second
component. In so far as these lines are considered to  originate from the
accretion disk material (Shafter, 1983) we  suggest that the disk
still exists in the system.



 In the period March 1994 - October 1994 KR Aur varied in the interval 14\fm 0
 - 15\fm 2. The star has begun to decrease its brightness since
  October 1994 and approximately in 4 months (March 1, 1995) reached 18\fm 1,
which is in an agreement with the observations of Honeycutt \& Robertson (1995).
\vfill \eject

\centerline{4}
\vskip 1mm
  The deep minimum state lasted approximately 8 months. The faintest magnitude
of the star, detected on October 20, 1995, was 19\fmm. However, this
measurement is uncertain because the object was near the plate limit.
From October 20, 1995 to November 25, 1995 KR Aur became 4\fmm\ brighter and
a flickering with an amplitude of 0\fm 15 in U-filter was detected again on November 25, 1995.

  We think, that the star had an unusually unstable mass transfer in a period
10 months before its fading to a deep minimum. It is possible, that a
pre-minimum  state exists for KR Aur. A slow decrease of the mass transfer
followed and it seems, the object spent a long time in an intermediate state.
 KR Aur faded from its intermediate state to the minimum for 4 months.  It
 spent 8 months in minimum state. The star went out of the minimum relatively
quickly -- for a little more than a month.

 The authors are thankful to Dr. I. Panfiorova for processing the spectral material.

 This work is partially supported by the Bulgarian National Science
Foundation under contract F-346/1993.
\vskip 1cm


\beginauthors
\authorsrightcol
A.P. ANTOV$^1$
R. KONSTANTINOVA-ANTOVA$^1$
E. SEMKOV$^1$ 
N. BORISSOV$^2$ 
Tsv. GEORGIEV$^1$
V. UMLENSKI$^1$
\endauthors
\vskip 5mm
$^1$ Institute of Astronomy, Bulgarian Academy of Sciences,

72 Tsarigradsko shosse blvd., BG-1784 Sofia, Bulgaria

e-mail: belogr@bgearn.acad.bg
\vskip 3mm
$^2$ Special Astrophysical Observatory of the Russian Academy of Sciences

357147 Niznij Arhyz, Karachaevo - Cherkezia
\vskip 9mm

\references

Afanas'ev, V.L., Lipovetskii, V.A., Mihailov, V.P. et al., 1991, {\it Astrophys.
Invest. (Izv.SAO)}, {\bf 31}, 128

Antov, A.P., Popov, V.N., 1994, {\it IAU Circ.}, No.\,5927

Honeycutt, K., Robertson, J., 1995, {\it IAU Circ.}, No.\,6132

Knyazev, A.Yu., Lipovetskii, V.A., 1994, {\it Otchet SAO}, No. 225

Popov, V.N., 1982, {\it IBVS}, No.\,2095

Popov, V.N., Kraitcheva, Z.T., 1990, {\it Contributions of the Astronomical
Observatory Skalnate Pleso}, {\bf 20}, 63

Popova, M.D., 1960, {\it Mitt. Ver\"and. Sterne (Sonneberg)}, 463, 81
%Popova, M.D., 1960, {\it Mitt. Ver\"and. Sterne (Sonneberg)}, No.\,463, 81

Popova, M.D., 1965, {\it Peremennie Zvezdi}, {\bf 15}, 534

Popova, M.D., Antov, A.P., Popov, V.N., 1982, in ``Magnetic and Variable
Stars", Commun. Konkoly Obs. Hung. Acad. Sci., Budapest, eds. M. Marik and
L. Szabados, No.\,83, p.220
\IBVSlink{http://www.konkoly.hu/Mitteilungen/83.html}

Shafter, A.W., 1983, {\it ApJ}, {\bf 267}, 222

Verdenet, M., Mizner, M., 1994, {\it IAU Circ.}, No.\,5931

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