J. Hesser - Academia.edu (original) (raw)

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Papers by J. Hesser

Late Stages of Stellar Evolution, 1974

Highlights of Astronomy, 1983

Symposium - International Astronomical Union, 1984

Astrophysics and Space Science Library, 1973

Proceedings of the International Astronomical Union

Star clusters are at the heart of astronomy, being key objects for our understanding of stellar e... more Star clusters are at the heart of astronomy, being key objects for our understanding of stellar evolution and galactic structure. Observations with the Hubble Space Telescope and other modern equipment have revealed fascinating new facts about these galactic building blocks. This book provides two comprehensive and up-to-date, pedagogically designed reviews on star clusters by two well-known experts in the field. Bruce Carney presents our current knowledge of the relative and absolute ages of globular clusters and the chemical history of our Galaxy. Bill Harris addresses globular clusters in external galaxies and their use as tracers of galaxy formation and cosmic distance indicators. The book is written for graduate students as well as professionals in astronomy and astrophysics.

The Astrophysical Journal, 1975

The Astrophysical Journal, 1976

ABSTRACT Results are reported for UBV photoelectric and photographic observations of about 700 st... more ABSTRACT Results are reported for UBV photoelectric and photographic observations of about 700 stars in the southern globular cluster NGC 6441 and of about 385 stars in or near the G2 globular cluster NGC 6304. Features in the color-magnitude diagrams of the clusters are found which indicate that NGC 6441 is one of the most metal-rich clusters known in the Galaxy and that NGC 6304 is a moderately metal-rich cluster. No unusual features in the color-magnitude diagram of NGC 6441 are detected that might account for its appearing in the error box of the X-ray source 3U 1746-37, except possibly the anomalous position of the variable star V6 in the diagram. Estimates are made of the foreground reddening, distance moduli, and integrated absolute visual magnitudes of both clusters. It is shown that NGC 6441 has a normal M/L ratio and is located at perigalacticon. NGC 6304 is shown to be located 450 pc above the galactic plane and possibly to contain two RR Lyrae variables.

The Astrophysical Journal, 1984

ABSTRACT A large region around the peculiar elliptical galaxy NGC 5128 (Centaurus A) has been ana... more ABSTRACT A large region around the peculiar elliptical galaxy NGC 5128 (Centaurus A) has been analyzed using prime focus plates taken in four colors to search for globular clusters. The plates have been scanned with COSMOS and processed to detect and analyze all images (7656 images in the region studied). Image counts show a significant excess of images above background to limiting magnitudes in the range V = 19-20, and these results are important for measuring the cluster luminosity function. Nonstellar images are identified, and a visual classification is used to obtain a sample of likely cluster candidates. Their sizes are estimated using a model of the plate-scanner system, and the completeness of the sample is discussed. Most bright clusters have probably been found, so the bright tail of the luminosity function is now fairly well known. The fainter clusters found here are systematically smaller than the brightest, and the sample is probably very incomplete for faint, compact clusters. Therefore the difference in sizes between bright and faint clusters is probably real. In most respects, the cluster system of NGC 5128 appears to be normal for a large elliptical galaxy.