Re: finding eclipsing binaries

[Fraser Farrell <fraser@trilobytes.com.au>]

Stupendous Man wrote:
>
>   It would be an interesting pencil-and-paper exercise for someone
> to estimate this number using the properties of "typical" eclipsing
> binaries.  That is, figure out what fraction of the time the star
> is noticeably fainter than normal, and then estimate how many points
> below max one needs to have confidence in the eclipses, and to
> determine the period, etc.


Here are examples of bright and obvious (in hindsight) eclipsers whose 
discoveries were delayed for various reasons:

V1016 Ori  -  6.72-7.65V, period 65.43 days. Every optical telescope ever 
used on Earth has looked at it, but its eclipses weren't noted until 1973. 
Adjacent is another eclipser BM Ori (7.9-8.65V, 6.47d) discovered years 
earlier. Together with two more adjacent stars these eclipsers form the 
famous Trapezium in Orion.

V1016 Ori's eclipses last for less than one day. I also note that many 
astronomy books mention BM Ori, but still don't identify which of the 
Trapezium stars it is. Undoubtedly many V1016 eclipses have been 
misidentified as BM eclipses. On the occasions when both stars are in eclipse 
the change in the Trapezium is quite striking!


Delta Vel  -  1.9-2.5v, 45.16d. Primary & secondary eclipses both last for 
almost a day. We're still trying to pin down the exact durations. Independent 
discoveries in 1997 by naked eye, and in 1989 by the star sensor (a 
non-image-forming navigational instrument) on the Galileo spacecraft. See 
IBVS 4999 for the details. Probably not spotted earlier because it's 
inevitably overexposed by typical photographic, photometric & CCD procedures. 

Zeta Phe, another southern eclipser of similar amplitude and colour, but 
fainter overall, was discovered almost a century ago.


Beta Per  -  2.1-3.4v, 2.87d. I'm sure Algol was discovered many many times 
throughout recorded history; but ancient astronomers seem to have disbelieved 
the evidence of their own eyes. Algol's variations aren't definitely reported 
prior to the 17th century. Possibly because of religious doctrines asserting 
that the heavens were the abode of gods and therefore "perfect"?

On the secular level we see similar assumptions today about the completeness 
and accuracy of variable star catalogues. Of course _we_ all know how naive 
that is.... :-)




cheers,

-- 

Fraser Farrell

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