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  • 1980-1984  (15)
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  • 11
    Publication Date: 2011-08-18
    Description: Observations of the 1969 Perseid and Orionid meteor showers are presented and used to derive luminosity functions for the 288 Perseids and 56 Orionids detected. Visual counts were performed under very good to excellent seeing conditions at the times of peak activities, and the brightnesses of the meteors were estimated to the nearest magnitude by comparison with the magnitudes of known objects. Maximum likelihood estimates of the power law index of the luminosity function of 1.56 + or - 0.06 for the Perseids and of 1.85 + or - 0.1 for the Orionids are obtained which are lower than the values found by other investigators. Under the assumption that the luminosity of visual meteors is proportional to their mass, the luminosity function power law may also be used to characterize the mass function.
    Keywords: ASTRONOMY
    Type: Icarus; 43; Sept
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  • 12
    Publication Date: 2011-08-18
    Description: Thirteen observatories have collaborated in obtaining five years of photoelectric photometry for the bright, K1 III RS CVn binary Sigma Geminorum. Except for one year, the light curve has exhibited two minima which are separated by approximately half a cycle. At the 1977.2 epoch of discovery one minimum was shallower, but as of 1982.2 they have become comparable in depth. During the 1979-80 season, the light curve changed shape rapidly, with the shallower minimum becoming as deep as the other within a period of no more than 80 days. The overall brightness range during the five years in V has been 4.13-4.29 mag, and it is found that the times of both minima can be fit with a photometric period of 19.423 days.
    Keywords: ASTRONOMY
    Type: Astrophysics and Space Science (ISSN 0004-640X); 93; 2, Ju; June 198
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  • 13
    Publication Date: 2019-06-28
    Description: Photoelectric photometry of the bright variable RS CVn-type binary Lambda And obtained in 1977-78 and 1980-81 is presented and used, together with earlier photometry, to derive the photometric period and discuss the changing shape of the light curve. The best ephemeris for times of minimum light is 2443829.2 + 53.95 d E. Because times of minimum and maximum extending back to those of Calder in 1933-37 can be phased together properly, the principal dark region must have maintained its identity for almost 50 yr. Over the last five years the brightness range has been between 3.70 and 4.05 m. During 1980-81 shallow secondary minima developed at phases where maxima occurred in previous years. Lambda And remains the only well-established case of nonsynchronous rotation among the known RS CVn variables.
    Keywords: ASTRONOMY
    Type: Astrophysics and Space Science (ISSN 0004-640X); 90; 1 Fe; Feb. 198
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  • 14
    Publication Date: 2019-06-28
    Description: A photometric period of 77.65 days is derived for 39 AY Ceti through a comparison of photoelectric photometry obtained in 1971 and 1972 with that obtained in the periods 1980-1981 and 1981-1982. JD 2444636.0 is an epoch of minimum light, and the full amplitude is found to have been as large as 0.18 mag in V. It is noted that the mean light level has dropped by almost 0.2 mag over the last decade. The present binary star is also noteworthy in light of the recently discovered white dwarf secondary component, and because radial velocity measurements indicate an eccentricity as large as 0.1 and an orbital period which, at 57.1 days, differs considerably from the photometric period presented.
    Keywords: ASTRONOMY
    Type: Astrophysics and Space Science (ISSN 0004-640X); 93; 2 Ju; June 198
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  • 15
    Publication Date: 2019-06-28
    Description: Three years of photometry in V and B of the UBV system are presented to confirm the suspicion of Herbst (1973) that HR 7275 is a variable star. The photometry is used to derive the photometric period, which proves to be about 3% shorter than the spectroscopically determined optical period of 28.59 d. Total variation observed during the three years was 0.22 m in the V, and the light curve was always asymmetrical.
    Keywords: ASTRONOMY
    Type: Astrophysics and Space Science; 83; 1-2,; Apr. 198
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