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\input ibvs2.sty
\input ibvst.sty

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\IBVShead{4954}{13 September 2000}

\IBVStitletl{CCD Light Curve and Revised Period}{ for the RR\lowercase{c} Variable AP Serpentis}

\IBVSauth{Bl\"attler, E.}

\IBVSinsto{BBSAG, Schl\"usselacher 1, CH-8636 Wald, Switzerland;
e-mail: blaettler-wald@bluewin.ch}

\SIMBADobjAlias{AP Ser}{HIP 74556}

\begintext

\IBVSTnam{AP Ser = AN\,34.1935 = GSC\,920.002 = HIP\,74556}

\IBVSTcoo{15\hr 14\mm 01\sec}{+09\deg 58\arcm 52\arcs}{2000.0}

\IBVSTobs{Private observatory, Schl\"usselacher, Wald, 0.15-m refractor}

\IBVSTdet{SBIG ST-7 CCD camera}

 \IBVSfig{8cm}{4954-f1.eps}{CCD light curve (without filter) of AP Ser}

\IBVSTfil{None}

\IBVSTcomp{GSC\,923.1074}

\IBVSTchk{GSC\,923.1281}

\IBVSTdata{Upon request from blaettler-wald@bluewin.ch} %email


\IBVSTtyp{ RRc }

\IBVSTrem{
The well known RRc variable AP Serpentis, discovered by 
Hoffmeister (1935), has been reobserved with our CCD equipment as  
mentioned above. During 8 nights between JD\,2451697 and JD\,2451724 
a total of 312 measurements were secured. AP Ser is the brighter, 
north-eastern star in a close double. In our aperture photometry, 
both components of the pair were included in the diaphragm. In the 
the Digital Sky Survey, the brightness of the companion can be 
estimated to be about 15.0 mag (photographic). Figure 1 shows our 
observations folded with a period of 0\fday340853, the best value 
for the representation of our data. This value is considerably 
shorter than the one given by de Bruijn and Lub (1985; 0\fday341320),
determined from $VBLUW$ photometry secured in 1975, and slightly longer 
than the period derived from the Hipparcos satellite photometry
(http://astro.estec.esa.nl/Hipparcos/), 0\fday340805. Neither of these 
earlier period values yield light curves of acceptable quality from 
our data. We have fitted the earlier photometry of AP Serpentis 
(Varsavsky, 1960; Pe\~na et al., 1990) with our period value and 
find both sets to be very well representable by it. Due to the rather 
long time gaps between the available sets of observations, it is not 
possible to assign cycle numbers unequivocally. A period of 
0\fday340852 brings the two latest sets in very good agreement, 
but fails to do so for the earliest set (Varsavsky, 1960). The most 
likely reason for this being a slight lengthening of the period 
value of AP Ser over the course of the last 40 years.}

\references

de Bruijn, J.W., Lub, J., 1985, {\it IBVS}, No.\ 2829

Hoffmeister, C., 1935, {\it Astron.\ Nachrichten}, {\bf 255}, 401

Pe\~na, J.H., Diaz, L.M., Peniche, R., 1990, {\it Rev.\ Mexicana
Astron.\ Astrof.}, {\bf 20}, 139

Varsavsky, C.M., 1960, {\it Astrophys.\ J.}, {\bf 131}, 623

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