Figure 1: The light curve of HR Car, 1889-1994 as a function of JD
(minus 2440000). See the text and
Table 1 (click here) for further explanation. Dates mark the
beginning of the year
In Fig. 1 (click here) a century of photometry of HR Car = HD90177, 1889-1993,
is put on one scale so that a clear overview of the long-term trend is
possible. The same was done in Paper I for AG Car and S Dor. Since
the colour index 
(of the UBV system) of HR Car amounts to
0.85 in the minimum and to 0.95 close to the maximum, the photographic
observations are corrected by 09 assuming that blue-sensitive plates
were used. See Table 2 (click here) for the global characteristics of the light
and colour curves. The smooth continuous curve in Fig. 1 (click here) is a copy
of Hoffleit's (1940) light curve, corrected (brightened) by
09. Dotted sections in the modern part of the light curve are not covered
by observations. The abbreviations used in Fig. 1 (click here) are explained in
Table 1 (click here). It appears that, on average, the visual light curves (Ba
mv) and (A mv) are fainter than the 
light curve by 
,
but their general trends are the same as for the curve. The (Ba
mv) light curve shows a dip not seen in the simultaneously observed parts
of the curve. It seems that the dip is caused by some estimates
of poor quality but, since the individual observations were not
published, this cannot be checked. The continuous curve in the upper
panel of Fig. 1 (click here) and the small portions in the lower panel represent
the well-covered parts of the light curve. Small-amplitude features,
with a time scale 
, in the last part of the
photoelectric light curve were smoothed away. They will be discussed in
Sect. 3.3. The small piece of dot-dashed curve at the right of the
upper panel is the extrapolation of the observed rising branch,
probably the onset of a third high maximum around JD2430000.
The brightness rise after JD2445000 is the
start of another high maximum. From Fig. 1 (click here) it can be deduced that
the apparent visual brightness varied over a range of 14 (between mv
= 7.35 and 8.7) during the last 107y.
Following the results of the analysis of AG Car and S Dor in Paper I, we assume that LBVs exhibit two types of SD phases with different cycle lengths, the VLT- and the normal SD phases, presumably caused by two different pulsational modes.
According to this interpretation, the VLT-SD light curve of HR Car is the lower enveloping line touching the minima and roughly represented by the broken curve in Fig. 1 (click here). All features superimposed thereon are the normal SD phases. For AG Car and S Dor an unambiguous cycle length could be established for these normal SD phases (Paper I).
In HR Car the maximum amplitude of the VLT variation is of the order of
05, which is much smaller than for AG Car and S Dor (
). The
peak-to-peak cycle lenghts (the observed high maxima in Hoffleit's
photographic light curve) lie between 20 and 50 years, which compares
very well with the VLT-SD cycles of AG Car (25y) and S Dor (35y).
Normal SD phases cannot be studied in the Hoffleit (1940) data
since only 200-d means were published.
The light curve after JD2444000 is not suitable for such an analysis,
either due to its short time span (
) or its many time
gaps. At the beginning, two normal SD phases with amplitudes 
were only partly observed; their total durations are between 2 and 2.7y.
Figure 2: Detailed light and colour curves of the 
micro
variations in the hump of the descending branch of HR Car's
normal SD phase (with a maximum at JD2446250). Note that the magnitude
scales for the colour curves are twice that for the light
curve
The observed part of the descending branch of the last-
mentioned SD phase, shown as a line segment running downward in
Fig. 1 (click here), in reality has a small hump on which a few cycles of
micro-variations are present with an average time scale of
and amplitudes of at most 015. They are shown in detail in
Fig. 2 (click here) and are based on the LTPV observations. Colour variations,
with the exception of u-v, are absent. The u-v colour index is blue in
the maxima and red in the minima (see also Sect. 3.3). Note that the
magnitude scales for the colour curves are twice those for the light curves.
A shoulder appears between JD2447000 and JD2447600 which is the
precursor of a high broad maximum discussed in Sect. 3.3.
Figure 3: The fine structure of the 1987-1994 light maximum of HR
Car in , the colour indices (scale at the right;
derived from the Walraven V-B) and of the Strömgren system, and the
blue and ultraviolet light curves of the Strömgren and Walraven
systems sorted in order of effective wavelength (all in magnitude
scale). Dates mark the beginning of the year
Figure 3 (click here) shows the detailed light and colour curves of the high
maximum of HR Car between 1987 and 1994. There is
excellent agreement between the various scales. The
uncertainty in each data point is of the order of 
. The
curve (scale at the right) is based on the transformed V-B
of the Walraven system. The b-y, v-b and u-v colour curves are in
the instrumental system and were obtained by adding the average
value of the comparison star A (= HD93010) to the individual
values of variable minus star A.
Note that the magnitude scales for the colours b-y, , v-b
and u-v are twice those for the light curves. Individual data points were
omitted in those parts of the curves where their number was too large
and the scatter very low. These parts are piecewise represented by
thin continuous lines. All these line pieces and scattered
differential magnitudes were connected by dotted curves. The two framed
sections in the curve consist partly of VBLUW observations.
Those of the frame at the left (which is part of the "shoulder''
mentioned in Sect. 3.2) were discussed in detail by van Genderen et
al. (1990). Those of the second frame higher up in the light curve
are shown in detail in Fig. 4 (click here).
Figure 4: The detailed light and colour variations of HR Car in the
Walraven system (upper framed part of the light curve in
Fig. 3 (click here)) relative to the comparison star and in log
intensity scale (bright and blue are up)
The reddening trend during the 5 years of brightness rise after 1988,
is typical for an SD phase. The range of the increase in
brightness decreases towards shorter wavelengths, but is less extreme
than for S Dor (Paper I) and R127 (Sect. 4) because the
variation in temperature is smaller. In the light minima of 1981
and 1987 HR Car has a temperature 
(van Genderen et al. 1990), in agreement with the
spectral type B4-5 determined by Shore et al. (1990).
Temperatures in the minima of S Dor and R127 are at least
20000K. In the light maxima the temperatures
cannot be much less than, say, 8000K (e.g. Wolf 1989),
perhaps with the exception of R110 (Sect. 7).
Part of the shoulder shows two simultaneous types of micro-variations:
a series of 20d micro-variations (blue in the maxima
and red in the minima) with a light amplitude of 006 superimposed on
micro-variations with amplitudes of 
(detailed
light and colour curves in van Genderen et al. 1990). Note
that these 20d micro-variations are half as short as the variations
detected about two years earlier (Sect. 3.2). After about 500d the 20d
variations disappear (with too few observations to check when and how this
happened). The colour behaviour of the
100d variations is red when bright and blue when faint. (It
should be noted that in the last-mentioned reference they were
interpreted as short-lasting SD phases and were still called "SD
eruptions'' but, as we proposed in Paper I, they should have been
called "SD phases'').
At JD2447880, higher up in the ascending branch (see the detailed
photometry in the VBLUW system in Fig. 4 (click here)), there is still a 20d
hump (time scale uncertain due to the lack of observations prior to
this hump) after which these short-time scale micro-variations are
definitely absent; see the smooth curve in the right-hand
panel of Fig. 4 (click here). Besides, there is now a clear tendency for the
maxima in the light curve to become red. We shall see that the phase lag
between light and colour curves is also, and very convincingly, present
in nearly all of the 100d micro-variations of R127, R40 and R71
(see further in this paper). During its maximum S Dor also showed
micro-variations with a time scale of (of which half
showed a mixed colour behaviour, Paper I). Sterken (1977,
1981) and Sterken et al. (1991) also found this kind
of micro-variation (quasi-period ) in the maximum of the LBV
HD160529.