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\begin{document}
\IBVShead{5286}{3 June 2002}

\IBVStitle{Has AY D\lowercase{ra} increased amplitude?}

\IBVSauth{Pejcha, O.$^1$; Sobotka, P.$^2$; \v{S}melcer, L.$^3$; Dubovsk\'{y}, P. A.$^4$; Br\'{a}t, L.$^5$; Henden,~A.~A.$^6$}

\IBVSinst{Okrouhl\'{a} 1, 625 00 Brno, Czech Republic, e-mail: {\tt pejcha@meduza.info}}

\IBVSinst{MEDUZA, Nicholas Copernicus Observatory and Planetarium,
Krav\'{\i} Hora 2, 616 00 Brno, Czech Republic,\\  e-mail: {\tt sobotka@meduza.info}}

\IBVSinst{Vala\v{s}sk\'{e} Mezi\v{r}\'{\i}\v{c}\'{\i} Observatory,
Vset\'{\i}nsk\'{a} 78, 757 01 Vala\v{s}sk\'{e}
Mezi\v{r}\'{\i}\v{c}\'{\i}, Czech Republic,\\  e-mail: {\tt lsmelcer@astrovm.cz}}

\IBVSinst{Vedecko-kulturne centrum na Orave, 027 42 Podbiel 194, Slovakia
          e-mail: {\tt vkco@isternet.sk}}
          
\IBVSinst{Velk\'{a} \'{U}pa 193, 542 21 Pec pod Sn\v{e}\v{z}kou, Czech
Republic, e-mail: {\tt brat@meduza.info}}

\IBVSinst{Universities Space Research Association/U.S. Naval
Observatory, P.O.Box 1149, Flagstaff, \\  Arizona
86002-1149, USA, e-mail: {\tt aah@nofs.navy.mil}}

\IBVSabs{We present visual and multi-color CCD observations of AY Dra,}
\IBVSabs{and argue about a possible amplitude increase.}

\SIMBADobj{AY Dra}

\IBVStyp{ Mira }
\IBVSkey{ photometry }



\begintext

The variability of AY~Dra (= BV 338 = GSC 03872 01194 = IRAS 15374+5711; $\alpha = 15\hr 38\mm 
39.34\sec$, 
$\delta = 57\deg 01\arcm 33.8\arcs$ [J2000]) was first noted by Strohmeier and Knigge (1960a). 
They 
determined variability between 10.6 and 12.6 mag on their photographic plates and
a preliminary long period variable classification.
Strohmeier and Knigge (1960b) observed three times of maxima and derived a pulsation period 
of 283.5 days. Nikulina (1961) published one time of maximum light with the remark that the star 
is probably of 
Mira type. Huth and Wittman (1968) searched photographic plates and determined 19 new times of 
maximum light and 
a new period of 262.5 days. Tsessevich and Makarenko~(1983) mention that about 1400 
photoelectric measurements 
of AY~Dra are deposited in the archive of Odessa Astrophysical Observatory. However, we have 
been informed by 
I.~L.~Andronov that these are actually measurements of the bright eclipsing binary AI~Dra. 
Stephenson (1985) determined 
an approximate M7 spectral type for AY~Dra. AY~Dra entered the GCVS (Kholopov et al.,\ 1985) as a 
SRa 
type variable star. Guglielmo et al.\ (1997) made JHK observations of AY~Dra showing that the 
star is oxygen rich. 
No observations of AY~Dra can be found in the databases of amateur visual observations. 
Thus, the star was selected as a target for MEDUZA\IBVSfm\IBVSfoot{{\tt http://www.meduza.info}} 
observers. 
\vskip-14.5pt

\IBVSfig{10cm}{5286-f1.eps}{Light curves of AY Dra. Upper panel: plus signs are visual observations, filled
circles are CCD $V$ band measurements with corresponding error bars. ``V'' shaped symbols are upper limits 
of visual observers. Lower panel: triangles are $V-R$ values and squares are $R-I$ values (shifted by \hbox{+0.2 mag for plot clarity}).}
\vskip-10pt
\IBVSfig{7cm}{5286-f2.eps}{$O-C$ diagram of maxima timings of AY Dra based on data from Table 1 
and ephemerides 
determined in this paper. Triangles are photographic observations and circles with error bars 
maxima from this paper.}

We carried out visual and CCD observations of AY Dra. For the calibration of the field stars,
Henden used the USNO Flagstaff Station 1.0~m telescope equipped
with a SITe/Tektronix $1024\times1024$ CCD to observe the field in
the standard Johnson-Cousins $BV(RI)_{c}$ passbands on four
photometric nights, using Landolt standards to calibrate the
field. Astrometry is based on USNO-A 2.0 and has less than
100mas internal error. Field photometry based on four nights is available through IBVS website 
as \hbox{5286-t2.txt}.
Sobotka and Pejcha used the 0.4~m Newtonian telescope of Nicholas Copernicus Observatory 
and Planetarium in Brno, equipped with an SBIG ST-7 CCD camera and $VRI$ filters. Frames 
(typically two to six in each band per night) were processed using MUNIDOS 2.2 
(Hroch, Nov\'{a}k and Kr\'{a}l, 2001). Observations were transformed to the standard 
Johnson-Cousins photometric system. 
Systematic zero-point shifts should be below 0.2 mag.
\v{S}melcer employed the 0.28~m Schmidt-Cassegrain telescope of the Vala\v{s}sk\'{e} 
Mezi\v{r}\'{\i}\v{c}\'{\i} 
Observatory with an SBIG ST-7 camera and $V$ filter. CCDOPS software bundled with SBIG cameras 
was 
used for photometry. 
Dubovsk\'{y}, Br\'{a}t and Pejcha made visual observations using 30, 25 and 25 cm Dobsonian 
telescopes, 
respectively. A few additional estimates were made by other MEDUZA members. 
The magnitudes of the comparison stars were based on magnitudes from TYC, TYC-2, GSC 
and field photometry from this paper; the finding chart can be found at the MEDUZA web page. 
As visual observations agree well with simultaneously taken CCD measurements, 
we find their precision adequate. Visual observations are available through the MEDUZA web page 
and CCD observations from the authors upon request.

\IBVSedata{5286-t2.txt}

Figure 1 shows the CCD $V$ band and visual light curve as well as $V-R$ and $R-I$ color curves. 
For clarity, weighted averages of CCD observations made on the same 
night with the 
same filter and by one observer were plotted. Magnitude errors served as weights. 

In Table 1 we present times of maximum light collected from literature and determined from our 
observations 
using the Kwee and von Woerden (1956) method as implemented in AVE (Barbera 2000).  To create a 
denser dataset, 
visual observations and CCD $V$ band timings were both used. The timing of the last maximum 
was determined separately in each passband and the final value in Table 1 is weighted average
 from the three passbands as no obvious difference is seen in times of maximum light determined in 
different filters.
Linear regression using all times of maximum light yields the following ephemeris:
$$\begin{array}{r@{}r@{}l}
{\rm Max. = JD}~2452275.0 & {} + 261.94 \times E. \\
                  \pm 0.5 &\pm 0.08 \\
\end{array}$$
Our best observed maximum was chosen as the fundamental epoch. We assigned double weights to 
maxima 
determined in this paper.  An $O-C$ diagram based on the ephemeris shown above 
and data from Table 1 is presented in Figure 2.

Our light curve amplitudes in the $VRI$ filters are 6.0, 3.9 and 2.4 mag, respectively. 
Our amplitude in the $V$ band is about 
three times higher than that of Strohmeier and Knigge (1960a). Comparison between currently 
known $V$ band amplitudes
for other stars with amplitudes given in Strohmeier and Knigge (1960a) do not show any 
difference higher than 0.2 mag.
This means that, the amplitude of AY~Dra has increased by a factor of 
three, leaving the maximum brightness roughly unchanged. Such a phenomenon has not been 
observed among classical Mira variables, but some semiregulars seem to exhibit such amplitude 
modulation. 
Kiss et al.\ (2000) attributed variations of amplitude with constant maximum brightness to a 
combination of nonradial pulsations and rotation, 
which seems to be quite unlikely for Mira variables. $B-V$ values of AY Dra near minimum light 
do not indicate presence of any hot companion.
We would like to invite astronomers to look through archives of 
photographic plates to confirm or disprove this possible amplitude variation of AY~Dra.

{\it Acknowledgements:} We acknowledge overall support and the use of the telescope with CCD 
camera of 
the Nicholas Copernicus Observatory and Planetarium. We would like to thank 
L. Kr\'{a}l and M. Bro\v{z} for software support and Dr. Mikul\'{a}\v{s}ek for careful review of 
the 
manuscript. 

This work has made use of the SIMBAD database, operated at CDS, Strasbourg, France.
The NASA ADS Abstract Service was used to access data and references. 

{\small
\begin{table}[h]
\caption{Maxima timings of AY Dra}
\begin{center}
\begin{tabular}{lcccclll}
\hline 
Geo.\ JD & Error & Filter & Epoch & $O-C$ & Observer & Source & Remark \\
\hline 
2426588 &    &  pg       &$-$98            &$-$17           &Strohmeier\&Knigge    &BV 11,6 &\\
2426872 &    &  pg       &$-$97            &$-$5            &Strohmeier\&Knigge    &BV 11,6 &\\
2427145 &    &  pg       &$-$96            &\phantom{+}16 &Strohmeier\&Knigge    &BV 11,6 &\\
2429759 &    &  pg       &$-$86            &\phantom{+}11 &Huth                  &MVS 4,176 & 
uncertain\\
2430524 &    &  pg       &$-$83            &$-$10           &Huth                  &MVS 4,176 &\\
2430796 &    &  pg       &$-$82            &$-$0            &Huth                  &MVS 4,176 &\\
2431310 &    &  pg       &$-$80            &$-$10           &Huth                  &MVS 4,176 
&uncertain\\
2431569 &    &  pg       &$-$79            &$-$13           &Huth                  &MVS 4,176 &\\
2433391 &    &  pg       &$-$72            &$-$24           &Huth                  &MVS 4,176 &\\
2434188 &    &  pg       &$-$69            &$-$13           &Nikulina              &AT 227,17 &\\
2434460 &    &  pg       &$-$68            &$-$3            &Huth                  &MVS 4,176 &\\
2435247 &    &  pg       &$-$65            &$-$2            &Huth                  &MVS 4,176 &\\
2436820 &    &  pg       &$-$59            &$-$1            &Wittman               &MVS 4,176 &\\
2437097 &    &  pg       &$-$58            &\phantom{+}14 &Wittman               &MVS 4,176 &\\
2437361 &    &  pg       &$-$57            &\phantom{+}17 &Wittman               &MVS 4,176 &\\
2437620 &    &  pg       &$-$56            &\phantom{+}14 &Wittman               &MVS 4,176 &\\
2437890 &    &  pg       &$-$55            &\phantom{+}22 &Wittman               &MVS 4,176 &\\
2438159 &    &  pg       &$-$54            &\phantom{+}29 &Wittman               &MVS 4,176 &\\
2438422 &    &  pg       &$-$53            &\phantom{+}30 &Wittman               &MVS 4,176 &\\
2438680 &    &  pg       &$-$52            &\phantom{+}26 &Wittman               &MVS 4,176 &\\
2438952 &    &  pg       &$-$51            &\phantom{+}36 &Wittman               &MVS 4,176 &\\
2439200 &    &  pg       &$-$50            &\phantom{+}22 &Wittman               &MVS 4,176 &\\
2439460 &    &  pg       &$-$49            &\phantom{+}20 &Wittman               &MVS 4,176 &\\
2451749 & 1  &  $V$+vis  &$-$2           &$-$2            &this paper                &this paper &\\
2452010 & 6  &  $V$+vis  &$-$1           &$-$3            &this paper               &this paper &\\
2452275 & 0.5& $V$+$R$+$I$+vis&\phantom{+}0&\phantom{+}0.0&this paper          &this paper & basic maximum\\ 
\hline
\end{tabular}
\end{center}
\end{table}
}
\large

\newpage
\references

Barbera, R., 2000, {\tt http://www.astrogea.org/soft/ave/aveint.htm}

Guglielmo, F. et al., 1997, {\it A\&AS}, {\bf 122}, 489  
%\BIBCODE{1997A&AS..122..489G}

Hroch, F., Nov\'{a}k, R., Kr\'{a}l, L., 2002, {\tt http://munipack.astronomy.cz}

Huth, Von H., Wittman, A., 1968, {\it MVS}, {\bf 4}, 176

Kholopov, P. N. et al., 1985, {\it General Catalogue of Variable Stars}, 4th edition, Moscow

Kiss, L. L., Szatm\'{a}ry, K., Szab\'{o}, G., Mattei, J. A., 2000, {\it A\&AS}, {\bf 145}, 283 
%\BIBCODE{2000A&AS..145..283K}

Kwee, K. K. and Van Woerden, H., 1956, {\it BAN}, {\bf 12}, No.\,464, 327

Nikulina, T.G., 1961, {\it Astr. Tsirk.}, {\bf 227}, 17  
%\BIBCODE{1961ATsir.227...17N}

Stephenson, C. B., 1985, {\it IBVS}, 2657  
%\BIBCODE{1985IBVS.2657....1S}

Strohmeier, W., Knigge, R., 1960a, {\it Bamb Ver\"off}, {\bf 5}, 6

Strohmeier, W., Knigge, R., 1960b, {\it Bamb Ver\"off}, {\bf 5}, 11

Tsessevich, V. P., Makarenko, E. N., 1983, {\it Astr. Tsirk.}, {\bf 1273}, 6 
\BIBCODE{1983ATsir1273....6T}

\endreferences


\end{document}

