[APML] OT: A Deep M13

["Robert Gendler" <robgendler@worldnet.att.net>]

Hi all,
Here's an M13 collaboration, data by Jim Misti, processed by me.

http://www.robgendlerastropics.com/M13JM.html

Just a little clarification about the presence of blue stars in many
globulars. Many of us have erroneously attributed the blue population
stars to "Blue Stragglers" which have received lots of publicity recently.
Probably the vast majority of blue stars in globulars are blue horizontal
branch stars which having exhausted their hydrogen fuel are now
fusing helium to carbon. The other bland colored or white stars are mostly
RR Lyrae stars which surprisingly make up a substantial population of many
globulars. The blue stragglers which are likely the result of either
collisions
in high density central regions or mass transfer in binary systems are
considerably
dimmer than the helium burning horizontal branch stars and are mostly
located
in the central dense core of globulars.

In summary many of the blue stars we see in CCD images of
globulars are blue horizontal branch helium burning stars and not
blue stragglers which are mostly central and less luminoius than the
other populations mentioned.

I hope that professional astronomers out there will let me know if I got
some of this wrong.


Rob Gendler
email: robgendler@att.net
Web Site: http://www.robgendlerastropics.com

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