[vsnet-ecl 2100] Fw: [AAVSO-DIS] GSC 2484-0592 eclipse

[K.Nagai]

----- Original Message -----
>Date: Sun, 22 Jan 2006 18:21:50 -0800
>From: "Don Davies" <DonDavies at verizon.net>
>To: <aavso-discussion at mira.aavso.org>
>Subject: [AAVSO-DIS] GSC 2484-0592 eclipse
>
>
>Last spring I posted an alert that GSC 2484-0592 (8:43:10, 31degs 50" 27", Mv
=7.3) was a previously unknown eclipsing variable with an undetermined period.
 (I had 3 recorded eclipses). There was also an indication of an eclipse with 
a single point in the Hipparcos data. After futilly watching for the last thre
e months, I finally caught another eclipse the evening of Jan. 9th (local time
, Jan. 10th UT). The eclipse was caught twice, with the two measurements being
 4.8 hours apart. The additional information was enough to determine a tentati
ve period of 31.219 days if I ignored the Hipparcos point. The solution had tw
o eclipses per period, separated by 11 and 20 days.
>
>The solution predicted another eclipse at ~8:00 Jan 21 UT. I successfully rec
orded the eclipse in I-band and Bruce Herrick recorded it in V-band.
>
>I obtained 20 measurements on ? hour centers that spanned the full duration o
f the eclipse. Preliminary analysis of the data indicates that the maximum ecl
ipse occurred at 8:50 Jan. 21 2006, which is JD 2453756.868 or HJD 2453756.874
. The duration of the eclipse was 5.0 hours, and the maximum depth was 0.70 ma
gnitudes.
>
>My best estimate of the phase difference between the Jan.10 and Jan 21 eclips
es is 0.357 (i.e. 11.2 days). This means that the next eclipse will happen ~9:
00 Feb. 10th UT, well suited for observations in the Americas. After that the 
next two eclipses will occur near dawn, then in the daytime for the Americas. 
>
>Since the eclipses are spaced unevenly during the orbital period, the orbit m
ust be quite elliptical. The three points that I have on the other eclipse don
't define its shape well, especially since two of them happen to fall at the s
ame phase. However, it is apparent that the Feb. 10th eclipse will be consider
ably longer (2 to 3 times) than the one just observed, again implying an ellip
tical orbit.
>
>The data also seems to imply that the two stars are very similar, and we are 
very close to the plane of the orbit. This follows from
>
>  1.. The "narrow" eclipse (Jan. 10) has a very triangular shape with no flat
 bottom.
>  2.. The "narrow" eclipse blocked out 50% of the light.
>  3.. The "wide" eclipse blocks out > 35% of the light.
>An interesting system; I hope someone gets the next eclipse! It will be espec
ially interesting to see how close the eclipse comes to 50% - that will give a
 better indication of the relative sizes and how far we are out of the plane o
f the orbit.
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