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THE ASTRONOMER Electronic Circular No 968      1995 June 24 15.08UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England. Telephone/FAX(0256)471074 Int:+44256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK             GMH at AST.STAR.RL.AC.UK
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HZ HERCULIS
Professional astronomers at Sussex University have asked for
assistance in monitoring HZ Her, optical component of the X-ray
source Her X-1 and located at: RA 16h56m02s DEC +35 25'05" [1950].
They supply the following background details:
HZ Her is a variable blue star (B~13, V~13) which has been shown to
be the optical companion to the unique X-ray pulsar Hercules X-1.
It is an eclipsing binary, showing a large fade in B (~1.8 mags) at
minimum light. Basically it is the most studied X-ray binary
system, and we are hoping to achieve a number of goals with our
campaign:
(1) weighing the NS - previous studies in the 1970's suggested that
Her X-1 had very low mass for a NS - a mass that causes problems
for theoretical moderls of NS formation. We aim to re-weigh the NS
by studying its radial velocity curve over a large number or
orbits, and also across the 35 day disk precession period.
(2) doppler tomography and eclipse mapping to study the accretion
disk - this will be aided by simultaneous photometric observations
covering the eclipse phase.
Editor: Visual and CCD results are needed between 1995 July 10-16
and again Sept 14-17. Critical nights in the first phase are:
July 10 (~23:00) and 15 (~02:00), covering the optical eclipse.
An e-chart and sequence follows:
\\\\\\HZ Her    c   Optical component of Her X-1
S,400,5,S
-C,16.9639, 35.3424,2000
O,199,200,13.0,14.5p
-L,L,HZ Her
-T,X-ray Seq:S&T 48 p373
-S,TA950624
P,16h 56.0m  +35 25'  (1950)
M,8,104,240
-L,R,75
R,12.5,121,185,A
R,12.8,304,166,B,R
R,13.4,240,188,C
R,13.7,223,255,D
R,13.9,148,102,E
R,14.5,169,100,F
R,14.9,166,221,G
M,10,83,327,178,252
M,11,290,304,79,9
M,12,44,111,241,338,134,319,375,134,184,60
M,13,2,206,15,59,36,299,32,384,1,377,255,393,101,388
M,13,155,330,105,321,87,99,192,121,386,143,279,168
M,13,292,173,162,183,385,213,302,38,113,22
M,13,84,236
M,14,70,237,17,130,8,330,42,246,48,393,53,260,387,384
M,14,383,381,176,380,153,381,199,355,399,341,353,335,276,329
M,14,153,316,290,124,90,294,339,132,158,287,122,144
M,14,103,201,333,258,280,40,82,227,270,31
M,15,68,230,35,20,70,208,57,110,8,292,65,348,38,360
M,15,104,375,299,375,107,373,273,375,374,399,386,398,381,343
M,15,291,82,360,106,350,120,122,122,392,69,236,127,241,136
M,15,360,284,262,61,257,148,375,283,270,152,179,60,351,281
M,15,336,279,226,276,264,175,257,51,111,267,87,194,85,267
M,15,284,5,112,209,252,220,245,249,265,232,149,233
E,103
////// Basic chart automatically generated by CHART ver 1.6
Guy M Hurst