Photoelectric observations and the wave minimum of RS CVn

1987 ◽  
Vol 137 (1) ◽  
pp. 63-72
Author(s):  
R. K. Srivastava
Keyword(s):  
Photoelectric Observations ◽  
Wave Minimum

scholarly journals The Unusual Period Distribution of the RR Lyrae Variables in NGC 5897

1989 ◽  
Vol 111 ◽  
pp. 287-287
Author(s):  
Amelia Wehlau
Keyword(s):  
Light Curves ◽  
Instability Strip ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Period Distribution ◽  
Unusual Distribution ◽  
Photoelectric Observations ◽  
Lyrae Stars ◽  
Branch Star ◽  
Central Concentration

AbstractAttention is called to the rather unusual distribution of the periods of the RR Lyrae variables in NGC 5897, a metal-poor halo globular cluster with a very low central concentration. Of the seven RR Lyrae stars known in the cluster, three have periods between 0.797 and 0.856 day and two have periods of 0.45 and 0.42 day. The other two have periods of 0.34 and 0.35 day with much lower amplitudes of variation. Due to the lack of crowding in this cluster photoelectric observations and Fourier decompositions of the resulting light curves should be possible for at least six of the RR Lyrae variables. In addition, the cluster appears to contain a non-variable horizontal branch star, SK 120, lying within the instability strip. As this is the only well documented case of such a star, photoelectric observations of this star would also be desirable.

scholarly journals The Period Changes of YY Eridani

1998 ◽  
Vol 11 (1) ◽  
pp. 370-370
Author(s):  
C.-H. Kim ◽  
J.H. Jeong ◽  
O. Demircan ◽  
Z. Muyesseroulu ◽  
E. Budding
Keyword(s):  
Activity Cycle ◽  
Light Level ◽  
Magnetic Activity ◽  
Third Body ◽  
Period Increase ◽  
Activity Effect ◽  
Abrupt Changes ◽  
Massive Component ◽  
Photoelectric Observations

A total of eighteen times of minimum lights for YY Eri were determined from relatively new or unpublished photoelectric observations collected from Korea and Turkey. All minima available to us were intensively analyzed to deduce the character of period variation of YY Eri. It is either formed by a sinusoidal variation superimposed on an upward parabola, or a set of abrupt changes. The abrupt changes appeared to have alternatively occured in the pattern of two increases following one decrease, which may be an indication of sinusoidal variations rather than real sudden changes of period. Upward parabolic variation can be due to a secular period increase caused by mass transfer from less massive to more massive component. The sinusoidal character can arise from a third body or from a strong magnetic activity cycle. Long term sinusoidal light level variation in the light curves supports the cyclic magnetic activity effect on the orbital period. However, the third body hypothesis can not be ruled out by the present data.

Photoelectric Observations of White Dwarfs at the Bologna Observatory

1993 ◽  
pp. 543-548 ◽  
Author(s):  
C. Bartolini ◽  
G. Cosentino ◽  
A. Guarnieri ◽  
A. Piccioni ◽  
R. Silvotti
Keyword(s):  
White Dwarfs ◽  
Photoelectric Observations

scholarly journals Photoelectric Observations of AD Leo: 1989-1994

1995 ◽  
Vol 151 ◽  
pp. 87-88
Author(s):  
R. Konstantinova-Antova ◽  
A.P. Antov
Keyword(s):  
Single Channel ◽  
Photon Counting ◽  
Astronomical Observatory ◽  
Program Package ◽  
Flare Star ◽  
The Other ◽  
Integration Time ◽  
Differential Photometry ◽  
Computer Controlled ◽  
Photoelectric Observations

An investigation of the activity of the flare star AD Leo was made using U-band patrol observations. 60 cm computer-controlled telescopes with identical single channel photon-counting photometers at the National Astronomical Observatory at Rozhen and at the Belogradchik Observatory were used. The integration time was 1 sec. Differential photometry was carried out, the AD Leo measurements were made relative to BD+20°2475. The data was reduced with the program package APR (Kirov et al. 1991).Two simultaneous observing runs were made. The results of the first have already been published (Antov etal. 1991). The other was part of the observational campaign in May, 1991 with the ROSAT satellite. In Bulgaria, the observations were carried out at Rozhen in the U-band and at Belogradchik in the B-band. Four flares were detected by both.

scholarly journals High-Speed Photometry of Cluster Flare Stars

1975 ◽  
Vol 67 ◽  
pp. 69-73
Author(s):  
M. Rodonò
Keyword(s):  
High Speed ◽  
Activity Level ◽  
Flare Star ◽  
Solar Neighbourhood ◽  
High Occurrence ◽  
High Speed Photometry ◽  
Flare Stars ◽  
Photoelectric Observations ◽  
Absolute Luminosity

Recent photoelectric observations made at Catania Observatory show a high occurrence of short-lived faint flares on the Hyades member II Tau (H II 2411). Its activity level turns out to be higher than for UV Cet-type stars of equal absolute luminosity.II Tau could represent a transition prototype between UV Cet-type flare star in the solar neighbourhood and cluster ones.The importance of coordinated photoelectric patrol of properly selected flare stars in clusters of different age is emphasized.

scholarly journals White Light Photometry of the Cataclysmic Variable BZ Camelopardalis

1992 ◽  
Vol 151 ◽  
pp. 441-444
Author(s):  
Gabriel Pajdosz ◽  
Stanisław Zoła
Keyword(s):  
Power Spectrum ◽  
Time Scales ◽  
White Light ◽  
High Speed ◽  
Cataclysmic Variable ◽  
Prominent Feature ◽  
Periodic Oscillations ◽  
Fourier Technique ◽  
Orbital Modulation ◽  
Photoelectric Observations

We present high-speed photoelectric observations of a 13th-mag cataclysmic binary BZ Cam (=0623+71), gathered in 1989 and 1990. The data were analyzed by means of the Fourier technique. The most prominent feature detected in the power spectrum is a 3h36m period which we ascribe as being a photometric orbital modulation. This period is significantly different from the periodicity previously known from spectroscopic observations. The power spectrum shows also quasi-periodic oscillations of shorter time-scales but any conclusions about their stability can not be drawn yet.

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