R127 = HDE 269858f was discovered as a new S Dor variable or LBV by Stahl et al. (1983; see also Stahl & Wolf 1986). Its spectrum at minimum light was OIafpe or, alternatively, WN9-10 (Walborn 1977, 1982). Table 2 (click here) lists the global characteristics of light and colour variations.
Figure 5: a) The fine structure of the 1982-1994 light and colour
curves of R127 in 
, 
(derived from the
Walraven V-B) and the colours of the Strömgren system.
The insert shows the more complete schematic light curve
between 1980 and 1994. Dates mark the beginning of the year.
See for the meaning of the arrows Sect. 8.
b) The same as Fig. 5 (click here)a, but now for the
blue and ultraviolet light curves of the Strömgren and
Walraven systems sorted in order of decreasing effective
wavelength from top to bottom; all in magnitude scale;
those of the Walraven system indicated at the right, relative
to the comparison star and with subscript W
Figure 5 (click here) show the detailed light and colour curves
comprising the time interval 1982-1994 (note that brightness and
colours include the contribution of the faint companion HDE
269858p at 
).
In Fig. 5 (click here)a the light curve for the magnitudes is
largely based on the y magnitudes (
) of the LTPV
project. Some values are based on UBV and VBLUW photometry. There is
excellent agreement between the various scales. The
uncertainty of each data point is of the order of 
.
The curve is based on a few UBV observations by de
Groot (plusses, quoted by Stahl et al. 1983) and on the
transformed V-B of the Walraven system. Note that the magnitude
scales for , b-y and v-b are twice those for and
u-v.
In Fig. 5 (click here)b a smooth curve has been sketched through the data points (dotted when the time gap is too long) showing the fine structure of the rising branch, the broad maximum and the start of a descending branch.
Stahl et al. (1983) adopted a minimum brightness for R127 of
(with a correction of 02 for the faint companion at a
distance of 
and with 
) as observed by
Mendoza (1970) in 1969. This is similar to the HDE
photographic magnitude determined at the end of the 19th century, corrected
by 03 to by Feast et al. (1960). Three years prior
to 1969, the brightness was higher by 08: 
(van
Genderen 1970, corrected for the faint companion). Consequently, the
observations presented in Fig. 5 (click here)a lying between 
(corrected for the faint companion) and 8.8 (companion negligible) represent
an SD-type activity with a preceding minimum at JD2444500 (105, see the
insert), a rising branch with three 
amplitude cycles
numbered 1-3 in Fig. 5 (click here)a each lasting 1.4y, a broad maximum
lasting 
, and a slow descent.
Figure 5 (click here)a shows details of the three peaks 1-3 during the early start of the rising branch. These SD phases show the expected colour variation, blue in the minima and red in the maxima. They are superimposed on the rise of what we would consider a VLT-SD cycle (dash-dotted curve in the insert). We suggest that maxima 1-3 be considered normal SD phases with maximum 3 interrupted ("filled in'') by the steep rise of the VLT-SD phase, like e.g. the maxima 36 and 37 of AG Car and the normal SD phases of S Dor (Paper I).
As far as we can judge the micro-variations superimposed on maxima 1-3 tend to belong to the "100d type'' (although the precise time scale cannot always be established with certainty due to time gaps). Their colours are red in the maxima and blue in the minima. An exception may be the small jump at JD 2446060 which is "bright and blue". Although its descending branch seems to last as long as 50 d, it is not certain that this peak should be classified as of the "100d type''.
The broad 1986-1993 maximum (Figs. 5 (click here)a,b) shows the typical
characteristics of an SD phase like the 1990-1993 maximum of HR Car
(Fig. 3 (click here)): a strong reddening of the colours starting midway the
rising branch of the curve. The amplitudes of the light
variations show a steep progressive decline to shorter wavelenghts: from
14 in to 05 in 
. Maximum light is first
reached at the shortest wavelengths and latest in the visual. The time
difference between the maxima in and is at least
1000d. The same is true for S Dor (Paper I), but not for HR Car where
light reaches maximum in all wavelenghts simultaneously
(Fig. 3 (click here)). At maximum , the brightness of
R127 has already declined to roughly the same value as the minimum at
JD2445500. The same fast decline in the ultraviolet has been noticed
for S Dor (Paper I).
This broad maximum shows at least a dozen peaks of micro-variations
with amplitudes of 
. Although it is difficult to
determine all the individual time scales, the general impression
is that they are of the order of 100d. In most cases colours are
red in the maxima and blue in the minima. However, their
behaviour is not always consistent: like in S Dor some peaks show
a mixed colour behaviour or are consistently "bright and blue''
(as at JD2446450 and JD2448650).
Figure 6: The detailed light and colour variations in the Walraven
system of R127 made after JD2447130, showing various 100d-type
cycles (relative to the comparison star and in log intensity
scale, bright and blue are up). Error bars are twice the mean
error per data point
The detailed light and colour variations of a few typical micro-variations are shown in Fig. 6 (click here). While there are some short-time scale micro-variations in addition to the 100 d-type micro-variations, they are generally red in the maxima and blue in the minima.
It seems peculiar that the time scale of the 100d-type
micro-variations of R127 hardly changes during the brightness rise of
in . At least, it does not change more than, say,
50% and there is no obviously continuous time-scale variation as
a function of the star's brightness. This characteristic is shared
with similar micro-variations of HR Car (Sect. 3.3),
apparently creating a paradox if one wants to explain these micro-variations
as the result of stellar pulsations. After all, one would expect that with
the apparent rise in brightness the radius increases and the density
decreases so that the period of radial pulsations increases.
In the case of R127 a rough guess indicates that the stellar radius
should increase by at least a factor of four from light minimum at
JD2444500 (, note that the real minimum is likely 
, see above) to maximum, assuming that the expansion of the star
is responsible for the total brightness rise.
Consequently, we have different possibilities. One of these is that the broad maximum is partly caused by an optically thick cool expanding shell making the star invisible. This shell could then be responsible for the 100d variations caused by responding to the changing flux produced by the stellar oscillations. Consequently, the 100d variations can then no longer be considered direct stellar pulsations. In this case the sometimes simultaneous presence of both short- and long-time scale micro-variations still needs an explanation. Another possibility is that in the expanding star the photospheric instability responsible for the short-time scale micro-variations dominant near minimum brightness is replaced by another type of photospheric instability that produces 100 d micro-variations which become the more dominant ones halfway up the ascending branch. In this case the non-continuous dependence of the time scale on the stellar density needs further explanation.