ISSN 0917-2211

Variable Star Bulletin
No.24

Dec. 1997

Resumption of Pulsation of RU Cam around 1970: Evidence from theVSOLJ Database
Minoru Sato (Akita, Japan)
Received 97 Sep. 28
1.

Introduction

RU Cam has been claimed to have stopped pulsation. I found from the VSOLJ Database that RU
Cam again showed appreciable variation around 1970. According to Burnham’s Celestial Handbook(Burnham, 1978), variation no greater than 0.04 mag was detected in 1966, and RU Cam wasconsidered to be a Cepheid which stopped pulsation.
However, T. Kato expressed: ”Though RU Cam is called as a variable star which stoppedvariation, recently released Hipparcos Catalogue shows the Hipparcos Satellite detected appreciablevariation. Though the star may have dropped from most amatuer’s target lists, the star should
receive more attention. The Hipparcos Satellite detected variation up to 0.2 mag. If the amplitudeis growing, we may have a chance to see more variation now”.
I searched through the VSOLJ Database whether there is any evidence of resumption of thepulsation in this variable. The result shows the period of cessation of the pulsation as alreadyclaimed, but the data also clearly shows the star resumed variation again around 1970. I describe
the data in two parts.
2.

The Period 1907—1911

In this period, the star varied between 8.0 — 9.6 mag, corresponding to an amplitude of 1.6 mag.
From the inspection of the light curve, I obtained the period of ∼20 d, which agrees with the 22-d
period listed in GCVS. The largest observed variation was detected between 1997 April 11 (9.69mag) and 1997 April 20 (8.02 mag), corresponding to an amplitude of 1.67 mag. Between 1907 and1908, the star showed variation with a range of 8.2 — 9.2 mag, and a period of ∼20 d.
3.

The Period 1964—1978

In the first half of this period, the star showed a range of 8.2 — 9.0 mag, corresponding to an
amplitude of 0.8 mag. In 1968 and 1969, the range of variation became 0.6 mag, fluctuating arounda mean level of 8.6 mag, without clear periodicity. It seems the star was stopping pulsation aroundthis period.
However, in 1970 and 1971, I found an evidence of large variation of 0.8 mag (8.3 — 9.1),
implying the variation, which once seemed to have stopped, resumed around this epoch. From theportion of the light curve showing clear periodicity, I yielded a period of 21.5 d.
In 1973 and 1974, the variation with an amplitude of 0.5 mag (8.4 — 8.9) was also observed,
having a period of ∼20 d. I cite some observations in Table 1. The observer is M. Sono. Fromthese data, it may be inferred that RU Cam resumed pulsation with an amplitude of 0.5 mag, anda period of ∼20 d.
1

Table 1. Selected observations of RU Cam
year month day mag.
1974
1158.91974
11148.4
1974
1125
8.9

Since 1976, the amplitude again decreased to 0.4 mag, and the periodicity became less clear
than around 1975. The data were sparse since 1986, but they also seem to imply the amplitudedecreased, and the periodicity became unclear.
Acknowledgments. This work has been based on the VSOLJ Database. The used data weremade by the following 12 observers: M. Iida, N. Ichinohe, T. Ishihara, N. Iwakami, M. Koshiro, T.
Miyake, M.Morita, E. Mochizuki, K. Kozawa, T. Saito, M. Sekiguchi, M. Sono.
References
Burnham R. Jr. 1978, Burnham’s Celestial Handbook vol.I, p.327-328, Dover, USA.

Reanalysis of Ichinohe’s Observations of RU Cam
Taichi Kato (Kyoto, Japan) and Seiichi Sakuma (Kawasaki, Japan)
Received 97 Nov. 25
The W Vir-type variable star, RU Cam, once claimed to have stopped pulsation (Demers,Fernie 1966; Huth 1966), has been known to show irregularly variable amplitude (Kollath, Szeidl
1993). Sato et al. (1997) has also shown from the analysis of the VSOLJ archive that visualobservers of the VSOLJ have recorded the cessation of pulsation and its possible resumption,
together with the phase of large-amplitude variation around 1910. The observations around 1910
were done by Ichinohe, a part of which was published by the observer himself (Ichinohe 1909).
We present the result of reanalysis of Ichinohe’s original data until 1911, by using the Hipparcos
V-magnitudes of the comparison stars.
The original observational records using Pogson’s step method were first analyzed by a leastsquares program (Kato, in preparation) to obtain the best step values of the comparison stars
and the variable star. The resultant step values of the comparison stars were used to calibrate theoriginal observation into the Hipparcos V system. Table 1 summarizes the result of best determined
step values of the comparison stars.
Table 1. Comparison stars
Desig.
acdebgf∗ Residuals from eq. (1)BD+70◦ 450+70◦ 447+69◦ 422+69◦ 420+70◦ 448+70◦ 445+70◦ 453

2

Steps
0.00
1.33
-3.40
1.44
2.29
5.29
4.54Hipparcos V
8.75
9.05
8.04
8.90
9.06
9.85
9.43

O-C∗
0.05
0.10
-0.01
-0.07
-0.08
0.14
-0.14

A least-squares fit of the step values to the Hipparcos V-magnitudes yielded the following
conversion equation.
V = 8.70 + 0.191 · step(1)
By using this, we have reduced the original observations to the present Hipparcos V-scale. The
result is tabulated in Table 2.

JD-2410000
7649.547
7650.805
7651.823
7652.708
7654.726
7657.799
7658.645
7658.646
7664.665
7665.646
7666.584
7667.588
7668.605
7668.653
7671.611
7671.726
7671.826
7675.591
7676.586
7679.625
7680.709
7682.697
7685.835
7686.631
7687.600
7689.715
7703.648
7704.697
7705.628

mag
8.69
9.12
9.08
9.21
9.47
8.78
9.06
9.06
8.37
8.47
8.48
8.71
8.74
8.70
8.88
8.95
9.07
9.53
9.79
9.41
9.01
8.61
8.00
8.50
8.38
8.37
8.76
8.55
8.37

Table 2. Ichinohe’s observations
JD-2410000 mag JD-2410000 mag
7706.709
8.19
8117.0688.86
7708.680
8.22
8148.997
8.44
7713.830
8.04
8168.163
9.07
7723.681
9.43
8173.192
8.22
7724.642
9.14
8174.2098.32
7728.690
8.42
8175.125
8.42
7735.672
8.36
8181.199
8.47
7740.667
9.09
8183.0748.54
7741.774
9.08
8211.088
9.05
7742.732
9.40
8212.120
8.91
7743.796
9.13
8215.051
8.26
7746.8178.90
8216.942
8.43
7747.822
8.74
8306.160
8.38
7749.846
8.25
8311.021
8.51
7759.8198.37
8324.217
8.78
7762.650
9.30
8331.1528.26
7763.7979.18
8336.140
8.76
7881.059
8.64
8337.056
9.21
7889.149
8.43
8354.965
8.33
7890.073
8.24
8359.182
8.80
7904.153
8.64
8364.126
8.89
7945.2409.07
8368.954
9.06
7949.2068.48
8390.133
9.09
7950.060
8.44
8392.944
8.75
7950.988
8.44
8405.003
8.99
7957.1088.32
8406.051
9.57
7962.941
8.95
8413.047
8.99
7966.0379.18
8422.0858.61
8057.1059.12
8424.165
8.25

JD-2410000
8445.040
8446.042
8450.061
8450.961
8526.285
8538.253
8558.232
8664.018
8714.062
8738.1818920.202
8951.024
8971.126
8982.881
9028.997
9053.913
9061.997
9062.985
9072.997
9088.180
9090.235
9103.001
9122.1159128.1159147.110
9150.087
9160.098
9183.034

mag
8.65
8.56
8.94
9.35
8.47
8.35
8.55
7.80
8.56
8.96
8.74
8.97
8.06
8.93
9.43
8.99
8.41
8.41
9.24
8.31
8.54
8.51
8.99
7.99
8.56
7.80
8.75
8.92

During this reduction procedure, possible inconsistencies were found among Ichinohe’s (1909)
step reduction for JDs 2417949.206, 2417962.941, 2418390.133 and 2418413.047. We consistently
used our new values in the following analysis.
After heliocentric corrections, the data were analyzed using the Phase Dispersion Minimization(PDM) method (Stellingwerf 1978) to obtain the pulsation period. The resultant theta diagram isshown in Figure 1. The best determined period of 22.18 d, which confirms the analysis by Ichinohe(1909), well agrees with the 22.187 d period given before 1917 (Huth 1966).
The averaged light curve constructed from these observations is shown in Figure 2. The epochof the light maximum was rather arbitrarily taken as HJD 2419150.085. Each point represents anaverage of 0.1-phase bin, typically constituted of ∼ 10 observations, and vertical bar 1-sigma error.
The range of light variation was 8.26 ( 0.06) — 9.33 ( 0.08), giving an amplitude of 1.07 ( 0.10),
which also confirmed the earlier reports. Our new analysis, however, rather disproves the existenceof the secondary maximum which Ichinohe (1909) described, giving a more consistent, typical W
Vir-type, light curve with those of other observers at that epoch.
3

Figure 1. Period analysis of RU Cam

Figure 2. Average lightcurve of RU Cam

Acknowledgments. This work has been based on the VSOLJ Database. The authors are
grateful to the VSOLJ staﬀs, and to M. Sato, who called our attention to the early observations ofRU Cam.
References
Demers S., Fernie J. D. 1966, Astrophys. J. 144, 440
Huth H. 1966, Dir Sterne 42, 129
Ichinohe N. 1909, Astron. Nachricht. 180, 363
Kollath Z., Szeidl B. 1993, Astron. Astrophys. 277, 62
Sato, M., VSOLJ Variable Star Bull. 24, 1
Stellingwerf R. F. 1978, Astrophys. J. 224, 953

Variable Star Observers League in Japan
National Science MuseumUeno Park Taito-ku Tokyo 110 Japan5