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\IBVShead{5515}{1 April 2004}

\IBVStitletl{CCD Photometry of the Variable Stars}{ V882~H\lowercase{er}, V386~V\lowercase{ul} and LX~P\lowercase{eg}}

\IBVSauth{Wetterer, C.$^1$; Majcen, S.$^2$}

\IBVSinst{United States Air Force Academy, USAF Academy, CO 80840, USA; e-mail: charles.wetterer@usafa.edu}

\IBVSinst{University of Ljubljana, SI - 1000 Ljubljana, Slovenia; e-mail: slavko.majcen@volja.net}

\SIMBADobj{V882 Her} 
\SIMBADobj{V386 Vul} 
\SIMBADobjAlias{LX Peg}{GSC 2212-2323}

\IBVSabs{Results of follow-up observations of variable stars}
\IBVSabs{previously discovered in a search for RR Lyrae variable stars in}
\IBVSabs{the CCD/Transit Instrument (CTI) survey are reported.  These}
\IBVSabs{variables were flagged as needing additional observations to}
\IBVSabs{confirm their type and/or period.}

\begintext

\IBVSEstarlis{
V882~Her & RRc  & 17\hr 44\mm 49\fsec1 & $+$28\deg 01\arcm 00\farcs & CTI catalog \\
V386~Vul & RRc  & 21\hr 21\mm 42\fsec8 & $+$28\deg 09\arcm 06\farcs & CTI catalog \\
LX~Peg   & EW   & 22\hr 03\mm 18\fsec9 & $+$28\deg 02\arcm
42\farcs & CTI catalog
\\}

\IBVSTobs{CCD Transit Instrument (CTI), 1.8-m f/2.2 meridian pointing telescope \\
Capilla Peak Observatory (CAP), 0.61-m f/15.2 Cassegrain telescope \\
US Air Force Academy Observatory (AFA), 0.61-m f/15.6 Cassegrain
telescope}

\IBVSTdet{CTI: RCA LN2-cooled CCD, 320 $\times$ 512 pixels,
8.3\arcm \ wide strip, CAP: RCA LN2-cooled CCD, 320 $\times$ 512
pixels, 3.6\arcm \ $\times$ 5.2\arcm \ FOV, AFA: Photometrics
LN2-cooled CCD, \hbox{512 $\times$ 512 pixels}, 3.6\arcm \ $\times$
3.6\arcm \ FOV.}

\IBVSTfil{CTI: $BVR$, CAP: $V$, AFA: $BV$}

\IBVSTdateobs{CTI: 1988.04--1991.05, CAP: 1994.06--1995.11, AFA: 1998.06--2003.09}

Photometric characteristics for these stars are listed in Table 1:
$V_{\rm Max}$ and $V_{\rm Min}$ are the average standard V magnitudes at
maximum and minimum light (CAP and AFA magnitudes transformed to
CTI instrumental magnitudes via differential photometry with
nearby stars in CTI database and then to standard magnitudes as
detailed in Wetterer et al. 1996 - hereafter W96); $V_{\rm Mean}$ is
the flux averaged standard V magnitude; $(B-V)$ is the B-V color
(recalculated from CTI data for V882~Her (at minimum light) and
V386~Vul (at maximum light due to limited CTI B observations), and
average value and recalculated with CTI and AFA data for LX Peg);
$E(B-V)$ is reddening (from W96 as estimated from Burstein and
Heiles 1982); period is in days, epoch is HJD of maxima for
V882~Her and
V386~Vul and HJD of primary minima for LX~Peg.  \\

\begin{table}[h]
\centering \caption{Photometric characteristics}
\begin{tabular}{llll} \hline\hline
           & V882~Her     & V386~Vul      & LX~Peg  \\
$V_{\rm Max}$  & 15.507(8)     & 15.155(7)     & 13.868(3) \\
$V_{\rm Min}$  & 15.828(10)    & 15.598(13)    & 14.060(5) (primary) \\
           &               &               & 14.032(9) (secondary) \\
$V_{\rm Mean}$ & 15.659(3)     & 15.359(3)     & 13.945(1) \\
$(B-V)$    & 0.31(4)       & 0.176(15)     & 0.978(5) \\
$E(B-V)$   & 0.056         & 0.152         & 0.090 \\
period     & 0.377501(8)   & 0.2452165(7)  & 0.279152(2) \\
epoch      & 2452833.786(9)& 2451092.790(4)& 2452589.6290(24) \\
type       & RRc           & RRc           & EW \\
\hline\hline
\end{tabular}
\end{table}

Notes on individual stars: \\

V882~Her was listed in W96 as a RR Lyrae type c variable star with
a period of 0.377069 days, although it was noted that the
1990-1991 CTI data did not match well with the chosen period.  The
additional AFA V observations make it clear that V882~Her's period
is changing. Unfortunately, due to the large gaps of time between
the various sets of data and the fact that CTI makes only one
observation per night, creating a standard O-C plot for this star
is impossible due to cycle count ambiguities.  Instead, we used
Lafler and Kinman's method for determining periods (Lafler and
Kinman 1965) on subsets of the data to determine acceptable
periods and their errors.  Figure 1 plots the best periods and
periods for aliases that produce reasonable but inferior light
curves as a function of central year for various subsets of the
data (the x-axis error bar indicates the range of data used). No
acceptable periods could be found using the ranges 1988 to $\ge$
1990, $\le$ 1991 to $\ge$ 1998, and $\le$ 1994 to 2003. The
simplest solution to building a composite lightcurve is to use
three different periods covering 1988-1989, 1990-1994, and
1998-2003. Figure 2 plots V882~Her's lightcurve for these three
periods and the composite lightcurve using each period over the
applicable time. Accepting these best periods leads to an
anomalously large average period change rate of $\beta$ = 37 $\pm$
8 days/Myr (shown as a line in Figure 1). More observations are
clearly needed over a longer time baseline
to better quantify the period change.\\

V386~Vul was listed in W96 as a RR Lyrae type c variable star with
a period of 0.325160~days, although because of the sidereal day
aliasing of CTI observations, it was noted that other periods were
possible.  Combining the CTI and AFA V observations (there were no
CAP observations) indicate that V386~Vul's period is indeed a
sidereal day alias to the originally calculated period.  The new
period is 0.2452165 days and the lightcurve is plotted in Figure 3.\\

LX~Peg was listed in W96 as a W~UMa type eclipsing variable with a
period of 0.279144~days, although it was noted that some data did
not fit this period very well and several other short periods were
equally possible.  Additional CAP and AFA V observations confirm
that the period is close to the originally published period,
however, this additional data also indicates that LX~Peg's period
may be changing.  Employing a similar strategy as with V882~Her
yields: no acceptable periods using all the data, 0.279152 $\pm$
0.000002~days using AFA V data, and 0.279142 $\pm$ 0.000002 days
using CTI and CAP V data. As in W96, the CTI and CAP period
solution is marginal with some data not fitting well.  Further
subdividing of the data, however, is not practical. Figure 4 plots
LX~Peg's lightcurve for these two periods and a composite
lightcurve using each period with the applicable data. More
observations over a longer time baseline are needed to better
quantify the possible period change. New AFA B observations were
made to check the B-V color and the B amplitude of variation. This
was done to confirm LX~Peg is too red to be a pulsational variable
of the $\delta$~Sct type. A few of the AFA nights included enough
phase coverage to measure minima timings for LX~Peg using the Kwee
and Van Woerden method (Kwee and Van
Woerden 1956). These timings are listed in Table 2.\\

\begin{table}[h]
\centering \caption{LX~Peg minima timings}
\begin{tabular}{ll} \hline\hline
HJD        & type \\
2451041.874(6) & secondary \\
2451048.709(6) & primary \\
2451048.850(5) & secondary \\
2451082.771(13) & primary \\
2451092.739(8) & secondary \\
2452589.6290(24) & primary \\
\hline\hline
\end{tabular}
\end{table}

\IBVSTack{The authors wish to thank Robert Kunkle for additional Capilla Peak observations, and Erik Carlson and Ray Bloomer for helping with the USAFA observations.}

\references

Burstein, D., and Heiles, C., 1982, {\it AJ}, 87, 1165.

Kwee, K. and Van Woerden, H., 1956, {\it BAN}, 12, 327.

Lafler, J. and Kinman, T. 1965, {\it ApJ Sup.}, 11, 216.

Wetterer, C.J., McGraw, J.T., Hess T.R., and Grashuis, R., 1996, {\it AJ}, 112, 742.

\endreferences


\IBVSfig{10cm}{5515-f1.eps}{Calculated periods for V882~Her in days as a
function of year. Filled diamonds are best periods, open diamonds
are aliased periods that produce inferior light curves.}
\IBVSfigKey{5515-f1.eps}{V882 Her}{periodogram}

\IBVSfig{10cm}{5515-f2.eps}{Light curves for V882~Her using various
periods. Composite light curve uses - 1988-1989: P = 0.377056
days, epoch = 2447319.8405 HJD; 1990-1994: P = 0.377223 days,
epoch = 2449552.8130 HJD; 1998-2003: P = 0.377501 days, epoch =
2452833.7863 HJD}
\IBVSfigKey{5515-f2.eps}{V882 Her}{light curve}

\IBVSfig{10cm}{5515-f3.eps}{Ligh tcurve for V386~Vul: P = 0.2452165 days,
epoch = 2451092.790 HJD}
\IBVSfigKey{5515-f3.eps}{V386 Vul}{light curve}

\IBVSfig{10cm}{5515-f4.eps}{Light curves for LX~Peg using various
periods.  Composite light curve uses - CTI/CAP: P = 0.279142 days,
epoch = 2450036.670 HJD; AFA: P = 0.279152 days, epoch =
2452589.630 HJD}
\IBVSfigKey{5515-f4.eps}{LX Peg}{light curve}

\end{document}
