1No.68

Dec. 2020

ISSN 0917-2211

Variable Star Bulletin
Photometric observations of nine Algol systems
Shin-ya Narusawa
Center for Astronomy, University of Hyogo, Sayo-cho, Hyogo, 679-5313, Japannarusawa@nhao.jp
andYasuhisa Nakamura
Fukushima Binary Star Laboratory, Nishi-Chuou 1-26-2, Fukushima 960-8074, Japannina-nak@dj9.so-net.ne.jp
Received 2020 Dec. 10

1Introduction

It is known that the light curves at the primary eclipse of many Algol-type binary systems are frequently disturbed.
Olson (e.g., Olson 1982) called such phenomena “transient photometric disturbances” (TPDs, hereafter), andconcluded that they occur due to the existence of circumstellar matter, hot/cool spot(s) and/or radius variations.
In order to obtain more information about TPDs, we carried out photometric observations of several short period
Algol binaries. Some comments on TPDs obtained by us are given.

2Observations

We observed nine Algol systems (XZ And, R CMa, RZ Cas, TV Cas, AB Cas, U CrB, AI Dra, RW Mon and XTri) with the 91-cm reflector equipped with the multi-channel polarimetric photometer (MCP) at the Dodaira
Station of the National Astronomical Observatory of Japan 1 from November 1993 to April 1996. The MCP hadeight channels (Kikuchi et al. 1979) with photomultipliers (EMI 9789QB, 6256B, 9658R) refrigerated with dry
ice. The effective wavelengths of the MCP were 360 nm (ch.1), 420 nm (ch.2), 455 nm (ch.3), 530 nm (ch.4), 640nm (ch.5), and 690 nm (ch.6), respectively (all of ch.7 and ch.8 and some of ch.1 were not used here due to large
scattering in our observations). Further details of the MCP are described in Kikuchi (1988).

3Results and Comments

A total of 20 primary eclipses were observed for above Algol systems and summarized in Table 1, together withthe estimated heliocentric times of minima on ch.4. In the table, E indicates the number of orbits counted fromthe first eclipse observed for each system. We found TPDs in five systems, which are described in the followings.

3.1

RZ CasThe primary minimum of RZ Cas is due to the partial eclipse, but it is known that the shape of light curve at themid-eclipse has frequently changed (e.g., Narusawa et al. 1994). Ohshima et al. (1998, 2001) found the δ Sct type1 now Dodaira Observatory of Town of Tokigawa, Saitama

2
nonradial pulsation in the primary component (pulsational period is ca. 22 min). This has led us to understandthat the change of shape is synthesized with the light variation of the partial eclipse and those of the oscillations.
Ohshima et al. (2001) categorized the shapes into four types; the “F-type” with a flat bottom; the “V-type” witha V-shaped curve; and the “S-type” with a slant increasing or decreasing smoothly. Furthermore, the subtypes“Sa” and “Sb” were classified which indicate an ascending slant and a descending one respectively. According
to the explanation by Ohshima et al. (2001), when the light maximum of the δ Sct pulsation coincides with thecenter of eclipse, the F-type is observed. When the light minimum of pulsation coincides with the mid-primary
eclipse, the V-type light curve is observed. The intermediate case is the S-type (the light maximum of pulsation
coincided with just before and just after the mid-eclipse yields the Sa- and Sb-type, respectively). We supposethat a partial-eclipsed curve, the “P-type” probably appears when the amplitude of pulsation is small.
Two of four primary eclipses obtained by us at the Dodaira Station are S-types. In the first night (1995 Nov.
2), the light curve seems to be Sa-type. Subsequently, the Sb-type was detected in the next night (1995 Nov.
3). Light curves of both nights were shown in Figure 1. These shapes indicate that the pulsational amplitude
was not small at that time. On the other hand, two other light curves obtained in 1993/94 season seem to beundisturbed (i.e. P-types were observed).

3.2

AB Cas

We observed four primary eclipses of AB Cas during two seasons. The light curve on Jan. 25 in 1994 seems tobe a flat type as shown in Figure 2. The duration of the flat bottom is about 18 min. Tempesti (1971) foundthat the primary component of AB Cas is a δ Sct-type star whose pulational period is 84 min, and Hong et al.
(2017) revealed that its oscillation is due to the fundamental radial p-mode. Therefore, we suppose that the flatbottom occurred due to the same mechanism as RZ Cas (i.e. it is the F-type). Remaining light curves have noflat bottoms (they are P-types).

3.3

R CMa

We could observe one eclipse of R CMa, and the shape of light curve at the mid-eclipse was not so clear but
seems to be flat (Figure 3). Mkrtichian & Gamarova (2000) found that the primary component of R CMa also
shows the δ Sct type oscillation. Subsequently, Lehmann et al. (2018) found that its period is 1.12 hr. Thus,
this portion is also probably F-type.
Moreover, the light curve has asymmetric shape (Figure 4) and the magnitude differences between descending
and ascending branches are up to 0.10 mag. (ch.1 and 2), 0.08 mag. (ch.3), 0.07 mag. (ch.4) and 0.05 mag. (ch.5and 6). The light curves on ch. 2 and ch. 4 were compared with B- and V -band of Koch (1960), respectively.
From the result, we recognize that brightness of the descending branch is darker than that of the ascending one.
Therefore, there is a possibility that the cool gas cloud which effectively absorb shorter wavelengths was seen at
the before mid-primary phase.

3.4

U CrB

The depth of the primary eclipse of U CrB on ch.1 on April 5 in 1996 was shallower than that of April 12 in
1995 as shown in Figure 5. The difference of 0.03 mag. is larger than the margin of error (differences of otherchannels were almost the same as errors). we regard this depth-change as an effect of circumstellar matter or thepulsation (Narusawa 2021 suggests the primary component of this star is a MAIA-type variable).

3.5

XZ AndThe shape of one (1995 Feb. 22) of three light curves of XZ And was not clear but looked like the F-type thatlasted ca. 17 min as shown in Figure 6 (other two had no clear flat bottoms). Moreover, Blitzstein (1954)
wrote that the primary minimum of this system was the total eclipse and its duration was 0.0076 day (11 min).
According to the Yang’s solution (2013), the primary minimum is partial of the ‘grazing’ eclipse. Hence, thesebottoms were not F-types but the pseud-totality caused by the grazing eclipse. Similar phenomenon appears inanother Algol-type system S Equ (Narusawa 2021).

34Summary

We carried out photometric observations of nine short period Algol-type binaries, and obtained a total of 20
primary eclipses. We found TPDs in five systems; RZ Cas, R CMa, AB Cas, U CrB and XZ And. We conclude
that more than half of all TPDs occurred due to the influence of the pulsation. Although, Olson (1982) studied
about TPDs without any consideration on the pulsation, we strongly feel that future work will surely need it.
Other details of this study will be published elsewhere.
The authors wish to express their thanks to staff members of Dodaira Observatory of NAOJ for their help
during our observations. The authors also acknowledge instructions on the data calibration of the MCP for Drs.
R. Hirata and A. Okazaki.

1.5

1.5

1.6

1.6

1.7

1.7

Δch.2

Δch.2

Reference:
Blitzstein, W. 1954, AJ, 59, 251
Hong, K., Lee, J. W., Koo, J.-R., Kim, S.-L., Lee, C.-U,., Park, J.-H., & Rittipruk, P. 2017, AJ, 153, 247
Kikuchi, S., Mikami, Y., & Konno, M. 1979, Tokyo Astron. Obs. Rep., No.18, 640
Kikuch, S. 1988, Tokyo Astron. Obs. Bull., 2nd ser., No.281
Koch, R. H. 1960, AJ, 65, 326
Lehmann, H., Tsymbal, V., Pertermann, F., Tkachenko, A., Mkrtichian, D. E. & A-thano, N. 2018, A&A, 615,
A131
Mkrtichian, D. E., & Gamarova, A. Yu. 2000, Inf. Bull. Var. Stars, 4836
Narusawa, S., Nakamura, Y., & Yamasaki, A. 1994, AJ, 107, 1141
Narusawa, S. 2021, in preparation
Ohshima, O., Narusawa, S., Akazawa, H., Fujii, M., Kawabata, T., & Ohkura, N. 1998 Inf. Bull. Var. Stars,No. 4581
Ohsima, O., Narusawa, S., Akazawa, H., Arai, K., Fujii, M., Kawabata, T., Morikawa, K., Ohkura, N. &Takeuti, M. 2001, AJ, 122, 418
Olson, E. C. 1982, ApJ, 259, 702
Tempesti, P. 1971, Inf. Bull. Var. Stars, No. 596
Yang, Y.-G. 2013, New Astronomy, 25, 109

1.8

1.8

1.9

1.9

2

2

2.1

2.1

11

11.2

11.4

11.6

11.8

UT

1212.2

12.4

15.8

16

16.2

16.4

16.6

16.8

1717.2

UT

Figure 1: Differential light curves of the primary minimum of RZ Cas on ch. 2. (Left panel: Nov. 2 1995. Rightpanel: Nov. 3 1995.) The abscissa is the Universal Time.

4

2

2.1

Δch.2

2.2

2.3

2.4

2.5

2.6

2.7
11.6

11.8

1212.2

12.4

12.6

UT

Figure 2: Same as in Figuer 1, but for the enlarged portion near the bottom of AB Cas on ch.2 on Jan. 25 1994.

1

1.02

1.04

Δch.2

1.06

1.08

1.1

1.12

1.14
12.6

12.8

1313.2

13.4

13.6

UTFigure 3: Same as in Figure 2, but for R CMa on ch.2 on Feb. 19 1995.

0.8

Δch.2

0.9

1

1.1

00.01

0.02

0.03

0.04

0.05

Hel. Phase

Figure 4: Light changes of the primary minimum of R CMa on ch.2 on Feb. 19 1995. Crosses and dots sings
represent ascending and descending branches, respectively.

5

0.9

Δch.1

1

1.1

1.2

1.3
-0.02

-0.01

00.01

0.02

Hel.Phase

Figure 5: Same in Figure 2, but for U CrB on ch.1. Dots and pulses sings represent on Apr. 12 1995 and Apr. 51996, respectively.

1.8

Δch.4

22.2

2.4

10.4

10.6

10.81111.2

UTFigure 6: Same as in Figure 2, but for XZ And on ch.4 on Feb. 22 1995.

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Table 1: Table 1. Estimated times of the observed primary minima
StarDateEXZ And

1994 Jan. 23
1995 Feb. 22
1995 Nov. 4
1995 Feb. 19
1993 Nov. 4
1994 Jan. 22
1995 Nov. 2
1995 Nov. 3
1993 Nov. 5
1993 Nov. 4
1994 Jan. 25
1995 Dec. 1
1995 Dec. 4
1995 Apr. 12
1996 Apr. 5
1994 Oct. 23
1995 Feb. 22
1994 Jan. 24
1994 Jan. 26
1995 Nov. 60291
479
066609610060554
5560104010201-R CMa
RZ CasTV Cas
AB CasU CrB
AI DraRW MonX Tri

Min I (HJD)(+2400000)
49375.96682(5)49770.94366(2)50026.11828(8)49768.04875(8)49296.07973(5)49374.96772(5)50023.99283(5)50025.18902(5)49297.07269(6)49295.99337(4)49378.00750(4)50053.25266(2)50055.98632(3)49820.13455(6)50179.17139(7)49648.95076(6)49771.22864(5)49377.11713(8)49379.02288(8)50028.20450(4)Comparison star
BD+40◦ 0405

-15◦ 1734+67◦ 0224+58◦ 24+70◦ 187+ 31◦ 2724
+52◦ 2018+08◦ 1400+27◦ 0317

VSOLJ
c/o Keiichi Saijo National Science Museum, Ueno-Park, Tokyo Japan
Editor Seiichiro Kiyota
e-mail: skiyotax@gmail.com
Publishing Masahiko Momose