\documentstyle[twoside, epsf]{article}

\input ibvs2.sty

\begin{document}

\IBVShead{5176}{21 September 2001}

\IBVStitle{B\lowercase{rh}V35 = GSC 0703-1930 is a Short-period RR\lowercase{c} Variable}

\IBVSauth{Bernhard, K.$^{1,4}$; Kiyota, S.$^{2}$; Lloyd, C.$^{3}$}

\IBVSinst{A--4030 Linz, Austria, e-mail: {\tt kl.bernhard@aon.at}}

\IBVSinst{Tsukuba, 305-0031 Japan, e-mail: {\tt skiyota@nias.affrc.go.jp}}

\IBVSinst{Space Science \& Technology Department, Rutherford Appleton
Laboratory, Chilton, Didcot,\\ \indent Oxon.\ OX11 0QX, UK, e-mail: {\tt cl@astro1.bnsc.rl.ac.uk}}

\IBVSinst{Bundesdeutsche Arbeitsge\-mein\-schaft f\"{u}r Ver\"{a}nderliche
Sterne e.V. (BAV), Munsterdamm 90,\\ \indent D--12169~Berlin, Germany}

\SIMBADobj{GSC 0703-1930}
\IBVStyp{ RRc }
\IBVSkey{RR Lyrae - photometry}
\IBVSabs{CCD observations of the recently discovered variable star BrhV35 =}
\IBVSabs{GSC 0703-1930, covering almost the full light curve, show that it}
\IBVSabs{is an RRc type variable with a period of 0.22630 days and a full}
\IBVSabs{amplitude of 0.4 mag. It is one of the shortest period RRc stars}
\IBVSabs{known.}

\begintext

BrhV35 (GSC 0703-1930, 05\hr17\mm22\fsec0 $+10\deg18\arcm28\arcs$, 2000,
$V\approx12\fmm7$) was discovered as a short-period variable of unknown
type by Bernhard (2000) as part of a programme to discover and classify
new variables in selected fields on the edge of the northern Milky Way
(see Bernhard \& Lloyd 2000 for further details). Following the eight
survey observations, additional long runs were made on one night by
Bernhard, and on six nights by Kiyota. The observations were made using a
20-cm Schmidt--Cassegrain telescope and an unfiltered Starlight Xpress SX
CCD camera with a Sony ICX027B chip (see Bernhard \& Lloyd 2000), and a 25-cm
Schmidt--Cassegrain telescope with an Apogee AP-7 CCD camera and Johnson $V$
filter. The comparison stars used were GSC 0703-2180, $V\approx12\fmm2$
and GSC 0703-1901 $V\approx12\fmm2$, which were found to be constant
with a magnitude difference $< 0\fmm03$.

The magnitudes, relative to GSC 0703-1901, of the two data sets were
simply combined; it was not necessary to apply any offset to the
unfiltered observations. The periodogram of the data shows two possible
periods, close to 4.4 and 5.4 cycles\,day$^{-1}$, which are part of a
series of strong 1-day aliases. However, the $\sim4.4$~c/d is
inconsistent with the data.  The longer period emerges unambiguously,
giving the ephemeris of maximum light
\[
\begin{array}{r@{}r@{}l}
{\rm JD_{Max}} = 2451614.873 & {} + 0.22630 & {} \times E. \\
\pm 5 & \pm 1 \\
\end{array}
\]

The light curve using this ephemeris is shown in Figure 1, and has a
slightly non-sinusoidal shape with a full amplitude of 0\fmm4. The
variation is consistent with a c-type RR Lyrae star, but the period is on
the extreme edge of the observed range, making it one of the shortest
period RRc variables known. In the GCVS only HX Ara ($P=0\fday219$) has a
shorter period (Kholopov et al.\ 1998). The amplitude and shape of the
light curve suggest that it is neither a $\delta$ Scuti nor $\beta$ Cephei
variable.

The observed colour from the USNO A2.0 catalogue (Monet et al.\ 1999),
$b-r=0.1$, is quite blue, and is consistent with other RR Lyrae stars
found by this programme (Bernhard \& Lloyd 2000). As the variation is not
large, and the two POSS plates on which these magnitudes are based were
taken consecutively, the observed value is probably a fair indication of
the true $b-r$.

The galactic co-ordinates, $l=192, b=-16$, place the star towards the
galactic anti-centre, at intermediate galactic latitude, and argue
against the $\delta$ Scuti or $\beta$ Cephei interpretation. They are
entirely consistent with an RR Lyrae star, and coincidentally, the
galactic latitude is the same as HX Ara.

This research made use of the SIMBAD database, operated by
the CDS at Strasbourg, France. 

\IBVSfig{10cm}{5176-f1.eps}{The phase diagram of the BrhV35 assuming that
the comparison star GSC 0703-1901 has $V=12.2$. The CCD observations of
Bernhard (filled circles) and Kiyota (open circles) are folded with the
ephemeris given in the text, and a high-order Fourier fit over plotted}

\references

Bernhard, K., 2000, {\it vsnet-newvar}, No.\ 274,\\
http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-newvar/msg00274.html

Bernhard, K., Lloyd, C., 2000, {\it IBVS}, No.\ 4920

Kholopov, P.N., Samus, N.N., Frolov, M.S., Goranskij, V.P., Gorynya, N.A.,
Karitskaya, E.A., Kazarovets, E.V., Kireeva, N.N., Kukarkina, N.P., Kurochkin,
N.E., Medvedeva, G.I., Pastukhova, E.N., Perova, N.B., Rastorguev, A.S.,
Shugarov, S.Yu., 1998, The Combined General Catalogue of Variable Stars,
4.1 Edition

Monet, D., Bird, A., Canzian, B., Dahn, C., Guetter, H., Harris, H., Henden, A.,
Levine, S., Luginbuhl, C., Monet, A.K.B., Rhodes, A., Riepe, B., Sell, S.,
Stone, R., Vrba, F., Walker, R., 1998, The USNO-A2.0 Catalogue

\end{document}

