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\IBVShead{4241}{6 September 1995}                      % Use it with dummy or empty arguments

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\centerline{\ft NSV\,4219 UMa: AN RR Lyr VARIABLE}	
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The variability of NSV\,4219 UMa (= CSV\,6652 = BV\,28) was discovered by
Strohmeier (Geyer et al., 1955) when he compared photographic plates taken
at the Bamberg Observatory in 1929 and 1930. The magnitude changes were
noted to be rapid and ranging between 11.1 and 11.9 (p).

NSV\,4219 is a visual double star. Its companion is of magnitude 12.61 (V) with
a B$-$V of 0.53.

The
first photoelectric measurements of NSV\,4219 UMa were obtained during a GEOS mission at the 
Jungfraujoch station, at the end of 1992. Others were obtained subsequently
and I have now 47 measurements at my disposal made with the photometer attached 
to the Jungfraujoch Observatory 76-cm telescope equipped with the B and V 
filters of the Geneva photometric system. It covers most of the star's
cycle with an instant of maximum.

To date, I have one photoelectric maximum and 21 maxima determined from visual
estimates at my disposal (Vandenbroere, 1995).
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\centerline{Figure 1. Identification chart of NSV\,4219 UMa and its comparison stars.}
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Figure 2. Composite light curve of the photoelectric measurements in V of
NSV\,4219 UMa using ephemeris (1).
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Figure 3. Phase curve of the  photoelectric indices (B$-$V)G of
NSV\,4219 UMa using ephemeris (1).
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Giving a triple weight to the photoelectric moment, I used the 22 instants to
calculate the elements of the period of NSV\,4219 UMa by linear regression and
obtained the following ephemeris:
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\hspace*{3cm}Max=JD hel 2449012.9896 + 0\fd 5428316 $\times$ E \hfill (1)

\hspace*{6.4cm}$\pm$0.0048\ $\pm$0.0000093 \hfill (confidence 95\%)

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The measurements shown in Figure 2 were obtained with the Jungfraujoch telescope
during the following nights: JD\,48983 (4 measurements), 48984 (2 measurements),
49097 (2 measurements), 49721 (3 measurements), and 49722 (36 measurements).

Except when in the vicinity of the minimum, all the measurements between phase
0.7 and phase 0.2 were obtained during the same cycle of the variable. The 
accuracy is $\pm$0.03 magnitude in V and the non-alignment of the point at
phase 0.91 not necessarily an actual change in the rate of light. The fluctuations
at the end of the decreasing phase are probably real because they are typical
of the light curve of RR Lyr stars with periods very close to that of NSV\,4219
UMa (Lub, 1977).

The ascending phase (M$-$m) is 0.24 period, which indicates an RRab type star.

The (B$-$V)G indices of NSV\,4219 UMa range from $-$0.49 to $-$0.22 (or
from 0.39 to 0.61 in the Johnson and Morgan system). They are in agreement with
the F spectrum of the New Catalogue of Suspected Variable Stars (1982). The 
shape of the colour index curve clearly shows that NSV\,4219 UMa is a classical
pulsating star of the RR Lyr type.

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% Call for macros \authors - \authorsrightcol - \endauthors
\beginauthors
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Jacqueline VANDENBROERE
GEOS (Groupe Europ\'een
d'Observations Stellaires),
3, promenade V\'en\'ezia
F-78000 Versailles
France
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\references

Geyer, E., Kippenhahn, R. and Strohmeier, W., 1955, {\it Kleine Ver\"offentlichungen
der Remeis-Sternwarte Bamberg}, No.\,9

Kukarkin, B. V. et al., 1982, New Catalogue of Suspected Variable Stars

Lub, J., 1977, {\it Astron. Astrophys. Suppl. Ser.}, {\bf 29}, 345

Vandenbroere, J., 1955, GEOS Circular on RR Lyr type variables, RR 13
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