New period and period variations of DX Aquarii

The new period (P=0 _. ^d 461700) of the eclipsing binary system DX Aqr has been presented, which is based on available times of minima. O–C diagram of DX Aqr has been presented for the first time, and the period variations present in the system have been analysed. In all five period increases and five period decreases are nothed, and four period increases and five period decreases have been discussed. The strongest period increase occurs between 1975 and 1976. The total period change in different portions of the O–C diagram ranges from 1.40×10^–4 d to 3.61×10^–6 d. Appreciable period fluctuations have been noted to have occurred in the time intervals, 1964–1965 and 1974–1975.     

Period study of XX cassiopeiae

New period (P=3^d.067182) of the eclipsing binary system XX Cassiopeiae has been given, which is based on thirty-nine minima. O–C diagram of XX Cas has been presented for the first time, and the period variations present in the system have been analysed. In all seven period increases and four period decreases are noted in the time-interval 1922 to 1983. Strongest period change occurs in the time-interval 1929 to 1933. The total period change in different portions of the O–C diagram ranges from 6.1×10^–7 d to 6.3×10^–4 d. Appreciable period fluctuations are noted in the time-interval 1922 to 1936. The possibility of the presence of a third body has been suspected.     

A new period and period trend of IZ Persei

A new period (P=3^d.687664) of the eclipsing binary system IZ Persei is given, based on 16 observed times of the minima. O–C diagrams of IZ Per have been presented for the first time, and the period variations have been estimated in different portions of the O–C diagram. Significant period changes do not appear to have occurred in IZ Per. The O–C diagrams suggest that the period of the system is continuously increasing at a rate of 25^s yr^–1. Period variations of the order of 10^–5 d appear to have occurred around the years 1969, 1972, and 1978. The period increases are stronger than the period decreases; but these are yet to be confirmed. The overall picture of IZ Per suggests that strong period changes are not present in the system; however, slow increase of period is apparent in IZ Per. The total period change (3×10^–6 d) till the last epoch is in agreement with the newly derived period of IZ Per.     

A new period and period changes of GG Cassiopeiae

The O–C diagram of the eclipsing binary GG Cassiopeiae has been presented for the first time, and the period changes present in the system have been analysed. In all three period changes are noted. The strongest period change has been found to occur in the time-interval 1942 to 1966. The total period change in different portions of the O–C diagram ranges from 7.1×10^–7 d to 2.0×10^–5 d. The stronger period changes appear to have occurred after 1942; prior to it, the system has shown a negligible period change. The overall picture of the O–C diagram suggests that the O–C values of the system GG Cas are negative after 1942. The presence of a third body does not appear probable. The period fluctuations are also appreciable. A new period (P=3 _. ^d 758733) has been presented.     

Period variations in BZ Eridani

The O-C diagram of BZ Eri has been presented for the first time, and the period variations present in the system have been analysed. In all, eight period decreases and eight period increases are noticed. Of these, four period decreases and seven period increases are appreciable. The strongest period changes are noticed in the interval 1960 to 1962. The total period change in different portions of the O-C diagram ranges from 1.17×10^–3 d to 3.96×10^–6 d. The trend of the period variation appears to have reversed around the year 1980.     

RS CVn-binary RW com: A possible three-body system

A first detailed period study of the eclipsing RS CVn-binary system RW Com is presented. A new period (P=0^d.2373455) based on 223 minima is given. The O–C diagrams of RW Com have been presented for the first time. Types of ten minima have been corrected judging the period trend. Period changes in different portions of the O–C diagram (Figure 2) have been estimated. The total change in period (P/P) ranges from 5.5×10^–7 to 6.4×10^–6. Thus, P ranges from 1.3×10^–7 d to 1.5×10^–6 d. Numerous minima are available in the time interval 1967 to 1986. This part of the O–C diagram (Figure 2) shows a sinusoidal variation, thus, it is suspected that RW Com could be a three-body system. The period of variation due to third body appears to be nearly 16 years.     

Period study of GH Pegasi

The period study of the eclipsing binary system GH Pegasi has been presented for the first time. A new period (P=2^d.556135) of GH Peg, based on all available times of minima, has been given. O–C diagrams of the system have also been presented for the first time, and the period changes present in the system have been analysed. The period shows changes around the year 1972 and 1981. The total period change in different portions of the O–C diagram, based on the corrected period, ranges from 5.2×10^–6 d to 7.0×10^–5 d. The photoelectric minima show sufficiently large scatter in the system.     

Period study of XY Ceti

A first period study of the eclipsing binary XY Ceti is presented. A new period (P=2^d.7807135), based on all available times of minima, is given. Period changes in different portions of the O–C diagram, with a new period, have been estimated. The total change in period (P/P) ranges from 1.1×10^–5 d to 1.2×10^–4 d, thus, P ranges from 3.1×10^–5 d to 3.3×10^–4 d. The O–C diagram suggests that the trend of the period has changed around the year 1959. Two portions of increasing and decreasing trends also reveal that the period changes (P/P) of the order of 10^–5 d are present, which are appreciably large.     

Period variation and the new light curves of V471 Tauri

The light curve and period variation of the eclipsing system V471 Tau is discussed. The migration period of 191 days obtained recently by Ibanolu agrees well with the new observations. The period decreases by about one second per century, which may correspond to a mass transfer of 1×10^–7 solar mass. Furthermore, the O–C diagram shows a noticeable sine curve super-imposed on the parabolic variation. The period of the sine curve is about 3.1 years.     

Period variations in BZ Eridani?

Recent claims that strong period variations are indicated in the O–C diagram of the eclipsing binary BZ Eri are shown to be based on a gross overestimation of the accuracy of photographic and visual times of minima. There is no evidence for any period change within the last fifty years.     

Period changes in EI Cephei

A new period (P=8^d.439422) of the eclipsing binary system EI Cephei has been given, which is based on all available times of minima. Periods using Strohmeier's (1958) epoch have also been presented for the observations given by other investigators. Period based on only photoelectric minima comes out to be 8^d.439336, which is lesser than the earlier periods given in the literature. O-C diagrams of EI Cephei have been presented for the first time, and period variations have been estimated in different portions of the O-C diagram (Figure 2) of EI Cephei. Strong period changes have occurred around the years 1959 and 1965. The total change in period (P/P) ranges from 6.7×10^–5 to 4.3×10^–4. Thus, P of the order of 10^–3 d are present, which fact suggests that strong period variations are present in EI Cephei. However, periods given by various investigators show no systematic trend of period variations. The existence of a third body in the system could not be confirmed.     

Period study of AL Camelopardalis

A detailed period study of the eclipsing binary system AL Cam is presented. A new period of 1^d.3283304 has been given. Period fluctuations are apparent around the years 1931, 1934, 1948, and 1965. Large scatter present in the early part of the O–C diagrams does not allow us to estimate the actual value of period changes present in different portions of O–C diagrams.     

ST Persei: A possible multi-body system

Detailed period study of the eclipsing binary ST Per is presented. A new period (P=2^d.648339) is given. Period changes in different portions of the O-C diagram with a new period have been estimated. The total changes in period (P) ranges from 2.17×10^–5d to 2.64×10^–4d which is appreciably large. Sufficient number of minima in the time interval 1934 to 1985 for this system are available. Distinct increasing and decreasing trends are evident, the change in the tendency appears to have occurred around 1947. Sinusoidal variation is seen between cycles 7000–10000, which indicates that ST Per is a three-body system, the period of the third body being about 22 years. However, the sinusoidal variation is not perfectly symmetric in shape, therefore, it is suspected that ST Per is a four-(or multi-) body system.     

A new period and period changes in VZ Hydrae

A new period (P=2 _. ^d 9042997) of the eclipsing binary system VZ Hydrae has been given, which is based on all the available times of minima. The period based on the photoelectric epochs has also been presented. The O?C diagram and detailed period study of VZ Hya have been presented for the first time, and the period changes have been estimated in different portions of the O?C diagram. Significant period changes do not appear to have occurred in VZ Hya, however, the O?C diagram suggests that the period of the system shows a slow tendency to increase. Period changes of 10^?5 d (?) to 10^?7 d have occurred around the years 1933, 1971, and 1975. All four period changes are noted in the time-interval 1918 to 1978. Upward treands appear stronger than the declining trends. Secondary minima show larger fluctuations than the primary minima. The fluctuations of the O?C values around the zero-line of VZ Hya demands notice for searching out the cause of period variations such as the presence of a third body.     

Cosmic ray intensity variations and two types of high speed solar streams

This study deals with the short-term variations of cosmic ray intensity during the interval 1973–78. Daily means of high latitude neutron and meson monitors from the same station and those of a low latitude neutron monitor have been analysed using the Chree method of superposed epochs. The zero epoch for the Chree analyses corresponds to the day of a substantial increase (V 200 km s^–1) in the solar wind speed to values of 550 km s^–1 and which persists at such high values for an interval of at least three days. The investigation reveals the existence of two types of cosmic ray intensity variations with distinctly different spectral characteristics. During the interval 1973–76, relative changes in the neutron and meson monitor rates are nearly equal indicating an almost flat rigidity spectrum of variation. During 1977–78, however, the spectrum acquires a negative spectral character similar to that observed for Forbush decreases. We suggest that events of the interval 1973–76 are essentially due to high speed streams associated with solar coronal holes and that events of the interval 1977–78 are due to fast streams from solar active regions with flare activity.     

Photoelectric photometry of the eclipsing binary EE Aqr

The system EE Aqr has been observed inUBV colours. A consistent set of orbital elements and a slightly improved period of 0 _. ^d 5089954 have been obtained. The eclipse is partial and variability is of Lyrae-type. The colour of the components has been determined.     

A period study of V450 Herculis

A detailed period study of the eclipsing binary system V450 Her has been presented. A new period (P= _. ^d 12724) has been given. The period changes in different portions of the O-C diagram, based on new period, have been estimated. The total period change ranges from 3.28×10^–6 d to 7.06×10^–5 d, which is appreciable.     

A note on the BBSAG visual observations

This Letter contains some comments on the communication by Diethelm and Locher (1988) concerning the period variations in the eclipsing binary systems EE Aqr, BZ Eri, IZ Per, and VZ Hya. Significance of the BBSAG visual observations has been discussed.     

Phase Curve Changes and Humps in U Her

U Her is studied by using 5294 observations from the AFOEV database. The 4–th order trigonometric fit to the mean light curve corresponds to the period P = 406^d 30 ± 0^d 01. Long–term variations of P are detected. The characteristics of individual cycles are determined and the correlations between them are studied. The variations of the duration of the ascending branch are nearly compensated by the duration of the preceeding descending branch. Other non obvious correlations were found between the brightness at the maximum and the preceeding minimum; between the inverse slope of the light curve dt/dm and the corresponding time interval from the maximum to the crossings of the constant brightness 9^m5 for both ascending and descending branches. The time interval between the hump and the maximum is correlated with the value of dt/dm at the ascending branch.     

On the period variations of several low declination high amplitude delta Scuti variables

A 16-inch Schmidt-Cassegrain telescope on the campus of Naresuan University of Thailand and several similar-size telescopes in China equipped with CCD cameras were used to observe 14 high amplitude delta Scuti stars: GP And, CY Aqr, BS Aqr, YZ Boo, AD CMi, VZ Cnc, EH Lib, DY Her, V927 Her, KZ Hya, BE Lyn, V1162 Ori, DY Peg, and CW Ser, between the years 1999 and 2010. Data were also collected from scientific journals and sources on the Internet for these variable stars. Times of light maximum of these delta Scuti stars were then either determined from the observations or obtained from the literature to analyze the pulsation period variations. For the 14 delta Scuti stars we concluded that 7 stars (BS Aqr, CY Aqr, AD CMi, EH Lib, KZ Hya, BE Lyn and DY Peg) are binary or multiple systems. 10 delta Scuti stars are found with periods increasing with rates between 5.86×10⁻⁹ and 2.34×10⁻⁶ per year and the other 4 stars (BS Aqr, DY Her, BE Lyn and DY Peg) show periods decreasing with rates of about 10⁻⁹ to 10⁻⁸ per year.