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\IBVShead{5182}{5 October 2001}

\IBVStitle{V, I$_{\bf C}$ Observations of the Variable Antipin V71}

\IBVSauth{Bacher, A.; Lederle, C.; Gr\"omer, G.; Kapferer, W.; Kausch, W.; Kimeswenger, S.}

\IBVSinsto{Institut f\"ur Astrophysik, Leopold-Franzens-Universit\"at 
Innsbruck, Technikerstr.\ 25, A-6020 Innsbruck, Austria\\
\indent e-mail: stefan.kimeswenger@uibk.ac.at}

\SIMBADobj{Antipin V71}

\IBVSabs{We present VI_C CCD photometry of the variable Antipin V71}
\IBVSabs{stated as fast variable of unknown type by the discoverer.}

\begintext

The variable star Antipin V71 was discovered on the Moscow plate
collection (Antipin 2000). We crossidentify the object with the star
USNO SA2 1500-00018885.  The star is given there with 15\fmm7 and
15\fmm0 in the red and the blue passbands, respectively.  Accurate
astrometry based on a local USNO SA2 frame relative to the surrounding
astrometric stars AC2000 451 (= Tycho-2 1053516), AC2000 191 and AC2000
332 (= Tycho-2 1053462) leads to
$$
\alpha_{\rm J2000.0} = 00\hr00\mm52\fsec901 \pm 0\fsec025,\qquad
\delta_{\rm J2000.0} = 62\deg25\arcm14\farcs84 \pm 0\farcs3.
$$
CCD photometry of this rapid variable ($P = 0\fday0865524$, Antipin
2000) was obtained at the Innsbruck 60-cm RC telescope during two runs
October~20, 2000 (MJD 51838) and December~5, 2000 (MJD 51884) using
Johnson $V$ and Cousins $I_{\rm C}$ filters.  Eight stars, later
absolute calibrated as tertiary standards at the end of the second run,
were chosen to obtain differential photometry. The exposure time was
200 and 150 seconds in $V$ and $I_{\rm C}$, respectively.  Due to cirrus
clouds on October~20 sometimes the exposure were extended up to 600
seconds in $V$.

\IBVSfig{6.0cm}{5182-f1.eps}{The $2\farcm8 \times 3\farcm7$ field around Antipin
V71 (thick horizontal bar) and the comparison stars used for the
differential photometry (N is up, E is left)}

\clearpage

\IBVSfig{5.97cm}{5182-f2.eps}{The $V$ (+) and the $I_{\rm C}$ ($\times$) light curve of the target}

\vskip-12pt

\IBVSfig{5.97cm}{5182-f3.eps}{The change of the $V-I_{\rm C}$ color as function of the phase}

\vskip-12pt
For the source extraction we used SExtractor (Bertin \& Arnouts 1996).
The absolute calibration was obtained by 55 frames of the stars HR 670,
7891, 8585, HD 58142 and HD 204414 taken on December 5.

The light curve clearly shows an asymmetrical behavior. We assume
Antipin V71 to be a high amplitude $\delta$ Sct  type star (HADS)\@.
There is a slight bump at phase of about 0.3 to 0.5.  The light curve
does not change during the whole set of observations covering more than
500 pulsations in total.  Antipin (2000) obtained a first light curve
by using 856 photographic plates obtained in the years 1948 to 1994.
Thus he was able to accurately derive the period.  We obtained, using
the original period, a slightly different phase of maximum light
$$
{\rm Max. = HJD}~2441186.458 \pm 0.001 + 0\fday0865524 \times E.
$$

\references

Antipin, S.V., 2000, {\it IBVS}, No.\ 4939 % \BIBCODE{2000IBVS.4939....1A}

Bertin, E., \& Arnouts, S., 1996, {\it A\&AS}, {\bf 117}, 393
% \BIBCODE{1996A&AS..117..393B} 

\endreferences


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