Constraints on the Horizontal-Branch Morphology of the Globular Cluster M79 (NGC 1904) from Optical and Far-UV Observations

Details Constraints on the Horizontal-Branch Morphology of the Globular Cluster M79 (NGC 1904) from Optical and Far-UV Observations Constraints on the Horizontal-Branch Morphology of the Globular Cluster M79 (NGC 1904) from Optical and Far-UV Observations

1996-02-12

arxiv.org/abs/astro-ph/9602057v1

Astronomy and Astrophysics

Astrophysics

20 pages, 12 Postscript figures, uses aaspp4 style. Postscript file available at http://shemesh.gsfc.nasa.gov/~dorman/Ben.html

Scientific paper

10.1086/117931

The globular cluster M79 was observed with the Hopkins Ultraviolet Telescope (HUT) during the Astro-1 space shuttle mission in 1990 December. The cluster's far-UV integrated spectrum shows strong absorption in the Lyman lines of atomic hydrogen. We seek to use this spectrum, together with optical photometry, to constrain the stellar mass distribution along its zero-age horizontal branch (ZAHB). We find that a Gaussian distribution of ZAHB masses, with a mean of 0.59 Msun and standard deviation 0.05 Msun, is able to reproduce the cluster's (B,V) color-magnitude diagram when subsequent stellar evolution is taken into account, but cannot reproduce the cluster's far-UV spectrum. Model stellar spectra fit directly to the HUT data indicate a surprising distribution of atmospheric parameters, with surface gravities (and thus implied masses) significantly lower than are predicted by canonical HB evolutionary models. This result is consistent with the findings of Moehler et al. [A&A, 294, 65 (1995)] for individual HB stars in M15. Further progress in understanding the mass distribution of the HB must await resolution of the inconsistencies between the derived stellar atmospheric parameters and the predictions of HB evolutionary models. Improved stellar spectral models, with higher spectral resolution and non-solar abundance ratios, may prove useful in this endeavor.

Affiliated with

Also associated with

No associations

Rating

Constraints on the Horizontal-Branch Morphology of the Globular Cluster M79 (NGC 1904) from Optical and Far-UV Observations does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Constraints on the Horizontal-Branch Morphology of the Globular Cluster M79 (NGC 1904) from Optical and Far-UV Observations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Constraints on the Horizontal-Branch Morphology of the Globular Cluster M79 (NGC 1904) from Optical and Far-UV Observations will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-50444