[vsnet-chat 2427] Re: BL Tel data

["PETER F WILLIAMS" <PFWILLIAMS@onaustralia.com.au>]

Hi Antonio and Fraser,

Re BL Tel (vsnet-chat 2418 and 2422) yes, I have had an interest in this
star for several years (about 15) but, as an observer only and I do not
pretend to be an expert on anything theoretical (not even on cloudy
nights!).

BL Tel is included in S J Kenyon's 1986 book The Symiotic Stars (ISBN 0 521
268079) as showing several features closely related to some symbiotic
(ZAND) systems.  This lists the following orbital elements for BL Tel by R
E Wing (1962, Mon. Not. Roy. Astr. Soc., 125, 189.) :

P	778 days
K1	19.3
K2	--
Vo	+91.8
e	0.31
omega	91
a1 sin i	281
f(M)	0.496


Members of the VSS RASNZ have been visually observing recent eclipses of BL
Tel and these observations indicate the following O-C dates of mid eclipse
(geocentric), relative to the GCVS elements GJD 2434692 +778.1 days.

Year	Observed	Calculated	O-C	Min.Mag (v)	Duration (days)	Interval

1983	2445591.5	2445586.0	+4.5	8.60		57.0		--
1985	2446369.5	2446364.1	+5.4	9.60		65.0		778.0
1987	2447144.5	2447142.2	+2.3	9.30		63.0		775.0
1992	2448703.0	2448698.4	+4.6	9.20		58.0		(1558.5)
1994	2449481.0	2449476.5	+4.5	10.10		62.0		778.0
1996	2450256.0	2450254.6	+1.4	8.90		65.0		775.0
1998	2451034.5	2451032.1	+2.4	8.96		56.0		778.5

This information is essentially Table 3 of a paper giving results for the
1998 eclipse of BL Tel, submitted for the Publications of the VSS RASNZ. 
Only scant observations were recorded for the 1990 eclipse so the intervat
1558.5 days refers to two cycles of this system.  Additional details of
eclipse beginning and end dates, decline and recovery rates, daily mean
magnitudes and the mean visual light curves are given in the series of VSS
papers.  The standard chart and comparison stars used for this series of
observations appears in VSS RASNZ Publications No.18 (1992).  It is
certainly not a pretty as Fraser's chart but it would be nice to all use
the same comparisons and help reduce the scatter typical in visual data. 

The next predicted eclipse of BL Tel should be centred near 2000 September
25 UT when the star will be an early evening to twilight object.

Trust this is of interest.

Regards

Peter Williams

----------
From: Fraser Farrell <fraserf@dove.net.au>
To: padillar@ism.com.br; pfwilliams@onaustralia.com.au
Cc: vsnet-chat@kusastro.kyoto-u.ac.jp
Subject: [vsnet-chat 2422] BL Tel data
Date: Tuesday, November 23, 1999 3:16

G'day Antonio,

Contact Peter Williams (pfwilliams@onaustralia.com.au) about this 
eclipsing binary. It has been a special interest of his for several 
years, and he has published a few articles about it in the Circulars of 
the VSS RASNZ.

If you need a copy of my up-to-date observing chart for BL Tel, let me 
know and I will email it to you.


cheers,
Fraser Farrell

http://vsnet.dove.net.au/~fraserf/

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp