[vsnet-campaign-be 57] Re: Delta Scorpii stopped fading (Percy)

[Taichi Kato <tkato>]

Re: Delta Scorpii stopped fading (Percy)

From: John Percy <jpercy@credit.erin.utoronto.ca>
Date: 	Wed, 20 Sep 2000 13:46:33 -0400
Subject: [vsnet-campaign-be 0] Re: Delta Scorpii stopped fading

Dear Colleagues,

The photometric behaviour of Be stars is quite diverse.  Some Be stars
brighten from a "base level" because of the formation of an equatorial
disc around the star, and they fade because the disc disperses, and is
no longer replenished.  Some Be stars (especially those which are seen
equator-on) tend to fade when the disc forms, because the disc scatters
light out of the line of sight.  Brightenings and fadings can occur on
time scales from days to months or more.  Unfortunately we do not fully
understand how and why a disc forms, and what determines the time scale
on which it forms and disperses.  [See JAAVSO 21, 29 (1992) and JAAVSO
25, 14 (1996) for a couple of papers on AAVSO photoelectric photometry 
of these stars]  That's one good reason for continuing to monitor
these stars using as many techniques as possible - spectroscopy,
photometry, polarimetry....

John Percy
=======================================================================
John R. Percy                                   jpercy@erin.utoronto.ca
Erindale College, University of Toronto         phone: (905) 828-5351
Mississauga, Ontario, Canada  L5L 1C6           fax: (905) 828-5425
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