Times Of Primary Minimum Research Articles

NEW CMOS PHOTOMETRY AND ARCHIVAL PHOTOGRAPHIC OBSERVATIONS OF THE W UMA STAR V752 CEN: EXTENDING THE O-C RECORD OF PERIOD CHANGES

We present new CMOS Bayer g-band photometry of the southern W UMa star V752 Cen, presenting two new times of primary minimum, and use archival photographic photometry from the Bamberg Sky Survey (mid 1960s) and the Harvard plate collection (∼1890 to 1990) to extend the O-C diagram back in time to ∼1900. Earlier authors have reported a constant period from the earliest published photometry in 1970 to about the year 2000, when a sudden change occurred to an increasing period. The archival photographic record presented here indicates the period was effectively constant back to 1900. Our 2020 data are also consistent with reported period increase. The V752 Cen system is known from earlier work to be a W UMa binary orbiting a lower mass spectroscopic binary. Our preliminary calculations, based on the reported centre-of-mass velocity change of the W UMa binary, suggest the wide orbit may have a period near 245 d, and could give rise to a light-travel time-effect of order 0.02 d. This does not however appear to be consistent with the SuperWASP photometric O-C results. Hence we suggest that considerable uncertainty exists concerning the properties of the wide orbit.

Evidence for quasiperiodicity in orbital period modulation of WW Cygni

The Algol type binary system WW Cygni is known to display an intricate orbital period variability phenomenon which consists in the presence of an alternating component superposed on a secular trend. The alternating component clearly deviates from a strictly periodic pattern. In the present paper we studied WW Cyg using a data set consisting of 309 times of primary minimum, free of outliers, covering a time base of 113.8 yr. We investigated these timing data using periodicity detection methods relying on both amplitude spectrum and enhanced self-correlation (ESC) methods through Monte Carlo simulations. The problem of estimation of the statistical significance in the ESC method was further developed. The multiperiodicity of the $O-C$ residuals was investigated via iterative prewhitening using three types of models consisting of polynomial (P) + multiperiodic (MP) terms, P + light travel time effect (LTTE) terms, and P + MP terms + LTTE terms. The interpretation of the results led us to the following two hypotheses: (i) a quasiperiodic modulation at a time scale of about 46 yr induced by the cyclic magnetic activity occurring in the cool secondary component of WW Cyg, or (ii) the coexistence of a periodic modulation with a period of 50.41 yr related to the presence of an unseen compact stellar object of at least $2.22~\mbox{M}_{\odot }$ in the system and a quasiperiodic modulation at a time scale of about 19.7 yr, caused by the mechanism (i).

An Exo-Jupiter candidate in the eclipsing binary FL Lyr

Light curves of the eclipsing binary FL Lyr acquired by the Kepler space telescope are analyzed. Eclipse timing measurements for FL Lyr testify to the presence of a third body in the system. Preliminary estimates of its mass and orbital period are > 4M_Jupiter and > 7 yrs. The times of primary minimum in the light curve of FL Lyr during the operation of the Kepler mission are presented.

Uvbylight curves of the eclipsing binary system V2154 Cyg

This paper presents complete uvby light curves for the recently discovered eclipsing binary system V2154 Cyg. Additional Crawford H data were also obtained. Three times of primary minima and two secondary minima are determined. An improved orbital period is found to be 2: 6306312. A detailed photometric analysis is made using the EBOP code. This eclipsing binary is probably one of the components of a much wider double star, forming altogether a triple system. The results show that the eclipsing pair is a detached system with two late-type stars very dierent in size. Masses of about M1 =1 :4 M and M2 =0 :8 M are inferred for the components by using stellar evolution models. The total mass of the probable triple system is estimated to be of about 3.5 M, leading to a minimum orbital period of about 140 yr for the visual pair.

Recent photoelectric photometry of the newly discovered eclipsing system BD + 13o4708

Two-colour photoelectric photometry of the eclipsing binary BD + 13o4708 was carried out. Several features such as asymmetry in the branches, light difference between the maxima, an eccentric orbit, a dip around phase 0.2 are distinctive. The new light elements of the system were computed using also the previous times of primary minima given by Walker (1988).

SUDDEN CHANGES IN THE PERIOD OF RT ANDROMEDAE

ABSTRACT Photoelectrically determined times of primary and secondary minimum are presented for the eclipsing binary RT And. These times of primary minima, when combined with other published minima, indicate that the system has undergone two sudden decreases in period since its discovery in 1901. The possibility of smaller amplitude, sporadic period jumps is also indicated. Key words: eclipsing binary - photometry - period changes

The Night Sky in November

THE moon is new on November 11 at 7·9h. and full on November 26 at 21·9h. U.T. The bright star λ Geminorum (magnitude 3·6) is occulted on November 30, the disappearance as seen from Greenwich taking place at 2h. 22·8m. at position angle 102° from the north point, and the reappearance at 3h. 37·8m. at 282°. Mars, Jupiter and Saturn are bright planets in the evening or night sky. In mid-November, Mars souths at about 18½h., Jupiter at 20½h. and Saturn at 22¼h. Jupiter is in conjunction with the moon on November 21 at 22h. and Saturn on November 24 at 1h. Uranus is in opposition on November 13, when its distance from the earth is nearly 1,731 million miles. Neptune, near the border between the constellations of Virgo and Leo, makes a near approach (about 20″) to the eighth magnitude star BD + 3° 2549. At about 21h. in the middle of the month, the Milky Way passes from the eastern to the western horizon through the zenith of London. The most distant celestial object that can be seen with the naked eye—the Great Nebula in Andromeda—is on the meridian at an altitude of 79°. Vega is the brightest star in the north-west quadrant of the sky and Capella the brightest in the north-east. The Pleiades cluster is well above the eastern horizon, and Orion is then just rising. The Leonid meteors should be looked for about November 14–16; their radiant point, preceding γ Loonis, rises about 23h. The meteors of this well-known shower are characterized by swift flights and their greenish colour. Light variations in the variable star Algol (β Persei) may be noticed about one and a half hours before and after the following times of primary minima: November 14d. 3·1h.; 16d. 23·9h.; 19d. 20·8h. and 22d. 17·6h.